THE REPRODUCTIV E SYSTEM Chapter 28 An Introduction

THE REPRODUCTIV E SYSTEM Chapter 28 An Introduction

THE REPRODUCTIV E SYSTEM Chapter 28 An Introduction to the Reproductive System Learning Outcomes 28-1 List the basic structures of the human reproductive system, and summarize the functions of each. 28-2 Describe the structures of the male reproductive system and the roles played by the reproductive tract and accessory glands in producing spermatozoa; specify the composition of semen; and summarize the hormonal mechanisms that regulate male reproductive functions. 28-3 Describe the structures of the female reproductive system and the ovarian roles in oogenesis; explain the complete ovarian and uterine cycles; outline the histology, anatomy, and functions of the vagina; and summarize all

aspects of the female reproductive cycle. 2015 Pearson Education, Inc. An Introduction to the Reproductive System Learning Outcomes 28-4 Discuss the physiology of sexual intercourse in males and females. 28-5 Describe the reproductive system changes that occur with aging. 28-6 Give examples of interactions between the reproductive system and each of the other organ systems. 2015 Pearson Education, Inc. An Introduction to the Reproductive System

The Reproductive System Is the only system that is not essential to the life of the individual Does affect other systems The male and female reproductive organs Produce and store specialized reproductive cells that combine to form new individuals Reproductive organs Also secrete hormones that play major roles in the maintenance of normal sexual function 2015 Pearson Education, Inc.

28-1 Structures of the Reproductive System Reproductive Structures Gonads are organs that produce gametes and hormones Ducts receive and transport gametes Accessory glands secrete fluids into ducts Perineal structures collectively known as external genitalia 2015 Pearson Education, Inc. 28-1 Structures of the Reproductive System The Reproductive Tract

Includes all chambers and passageways that connect ducts to the exterior of the body Male and Female Reproductive Systems Are functionally different Female produces one gamete per month Retains and nurtures zygote Male produces large quantities of gametes Produces 2015 Pearson Education, Inc. 1/2 billion sperm per day 28-1 Structures of the Reproductive System The Male Reproductive System

Testes or male gonads Secrete male sex hormones (androgens) Produce male gametes (spermatozoa or sperm) The Female Reproductive System Ovaries or female gonads

Uterine tubes Encloses and supports developing embryo Vagina 2015 Pearson Education, Inc. Carry oocytes to uterus if sperm reaches oocyte, fertilization is initiated and oocyte matures into ovum Uterus Release one immature gamete (oocyte) per month Produce hormones

Connects uterus with exterior 28-2 Male Reproductive Functions Pathway of Spermatozoa Testis Epididymis Ductus deferens (vas deferens) Ejaculatory duct Urethra 2015 Pearson Education, Inc. 28-2 Male Reproductive Functions Accessory Organs

Secrete fluids into ejaculatory ducts and urethra Seminal glands (vesicles) Prostate gland Bulbourethral glands External Genitalia Scrotum Encloses testes Penis Erectile organ Contains distal portion of urethra 2015 Pearson Education, Inc.

Figure 28-1 The Male Reproductive System (Part 1 of 2). Prostatic urethra Pubic symphysis Major Structures of the Male Reproductive System Ducts Urinary bladder Ejaculatory duct Membranous urethra Spongy urethra Ductus deferens Epididymis Gonad Testis Corpus cavernosum External Genitalia Penis

Corpus spongiosum Scrotum External urethral orifice Figure 28-1 The Male Reproductive System (Part 2 of 2). Ureter Rectum Accessory Glands Seminal gland Prostate gland Bulbourethral gland Anus 28-2 Male Reproductive Functions The Testes Egg shaped

5 cm long, 3 cm wide, 2.5 cm thick (2 in. 1.2 in. 1 in.) Each weighs 1015 g (0.350.53 oz) Hang in scrotum 2015 Pearson Education, Inc. The Scrotum Is a fleshy pouch Suspended inferior to perineum Anterior to anus Posterior to base of penis 28-2 Male Reproductive Functions

Descent of the Testes Testes form inside body cavity adjacent to kidneys Gubernaculum testis Is a bundle of connective tissue fibers Extends from testis to pockets of peritoneum Locks testes in position (near anterior abdominal wall) as fetus grows 2015 Pearson Education, Inc. 28-2 Male Reproductive Functions Descent of the Testes During seventh month

Fetus grows rapidly Circulating hormones Stimulate contraction of gubernaculum testis Each testis: Moves through abdominal musculature Is accompanied by pockets of peritoneal cavity 2015 Pearson Education, Inc. 28-2 Male Reproductive Functions Accessory Structures

Accompany testis during descent Form body of spermatic cord Ductus deferens Testicular blood vessels, nerves, and lymphatic vessels 2015 Pearson Education, Inc. 28-2 Male Reproductive Functions The Spermatic Cords Extend between abdominopelvic cavity and testes Consist of layers of fascia and muscle Enclose ductus deferens, blood vessels, nerves, and lymphatic vessels of testes

Pass through inguinal canal Are passageways through abdominal musculature Form during development as testes descend into scrotum Descend into scrotum 2015 Pearson Education, Inc. 28-2 Male Reproductive Functions Blood Vessels of Testes Deferential artery Testicular artery Pampiniform plexus of testicular vein

Nerves of Testes Branches of genitofemoral nerve From 2015 Pearson Education, Inc. lumbar plexus 28-2 Male Reproductive Functions Male Inguinal Hernias Are protrusions of visceral tissues into inguinal canal Spermatic cord (in closed inguinal canal) Causes weak point in abdominal wall

Female Inguinal Canals Are very small Contain ilioinguinal nerves and round ligaments of uterus 2015 Pearson Education, Inc. 2015 Pearson Education, Inc. 28-2 Male Reproductive Functions The Scrotum and the Position of the Testes Is divided into two chambers, or scrotal cavities Each testis lies in a separate scrotal chamber Raphe Is

a raised thickening in scrotal surface Marks partition of two scrotal chambers 2015 Pearson Education, Inc. 28-2 Male Reproductive Functions Tunica Vaginalis Is a serous membrane Lines scrotal cavity Reduces friction between opposing surfaces Parietal (scrotal) Visceral (testicular) 2015 Pearson Education, Inc. 28-2 Male Reproductive Functions

The Dartos Muscle Is a layer of smooth muscle in dermis of scrotum Causes characteristic wrinkling of scrotal surface The Cremaster Muscle Is a layer of skeletal muscle deep to dermis Tenses scrotum and pulls testes closer to body (temperature regulation) 2015 Pearson Education, Inc. 28-2 Male Reproductive Functions Temperature Regulation Normal sperm development in testes

Requires temperatures 1.1C (2F) lower than body temperature Muscles relax or contract To move testes away or toward body To maintain acceptable testicular temperatures 2015 Pearson Education, Inc. 28-2 Male Reproductive Functions Structure of the Testes Tunica Albuginea Is deep to tunica vaginalis A dense layer of connective tissue rich in collagen

fibers Continuous with fibers surrounding epididymis Fibers extend into substance of testis and form fibrous partitions, or septa, that converge near entrance to epididymis Supports blood and lymphatic vessels of testis and efferent ductules 2015 Pearson Education, Inc. 28-2 Male Reproductive Functions Histology of the Testes Septa subdivide testis into lobules Lobules contain about 800 slender and tightly coiled seminiferous tubules Produce sperm Each is about 80 cm (32 in.) long Testis contains about 1/2 mile of tightly coiled seminiferous tubules

Form a loop connected to rete testis, a network of passageways Efferent Ductules 1520 large efferent ductules Connect 2015 Pearson Education, Inc. rete testis to epididymis 28-2 Male Reproductive Functions Connective Tissue Capsules Surround tubules Areolar tissue fills spaces between tubules Within those spaces, there are:

Blood vessels Large interstitial cells (Leydig cells) 2015 Pearson Education, Inc. Produce androgens, dominant male sex hormones Testosterone is the most important androgen 28-2 Male Reproductive Functions Spermatogenesis Is the process of sperm production Begins at outermost cell layer in seminiferous tubules Proceeds toward lumen

2015 Pearson Education, Inc. 28-2 Male Reproductive Functions Cells of Spermatogenesis Spermatogonia (stem cells) divide by mitosis to produce two daughter cells One remains as spermatogonium Second differentiates into primary spermatocyte Primary spermatocytes begin meiosis and form secondary spermatocytes 2015 Pearson Education, Inc. 28-2 Male Reproductive Functions Cells of Spermatogenesis

Secondary spermatocytes differentiate into spermatids (immature gametes) Spermatids Differentiate into spermatozoa Spermatozoa Lose contact with wall of seminiferous tubule Enter fluid in lumen 2015 Pearson Education, Inc. Figure 28-5d The Seminiferous Tubules. 28-2 Male Reproductive Functions

Contents of Seminiferous Tubules Spermatogonia Spermatocytes at various stages of meiosis Spermatids Spermatozoa Large nurse cells (also called sustentacular cells or Sertoli cells) Are attached to tubular capsule Extend to lumen between other types of cells 2015 Pearson Education, Inc. 28-2 Male Reproductive Functions Spermatogenesis

Involves three integrated processes 1. 2. 3. 2015 Pearson Education, Inc. Mitosis Meiosis Spermiogenesis 28-2 Male Reproductive Functions Mitosis Is part of somatic cell division Produces two diploid (2n) daughter cells Both

have identical pairs of chromosomes 2015 Pearson Education, Inc. 28-2 Male Reproductive Functions Meiosis Is a special form of cell division involved only in production of gametes Spermatozoa in males Oocytes in females Gametes contain 23 chromosomes,

half the normal amount Fusion of male and female gametes produces zygote with 46 chromosomes In seminiferous tubules: Begins with primary spermatocytes Produces spermatids (undifferentiated male gametes) 2015 Pearson Education, Inc. 28-2 Male Reproductive Functions Spermiogenesis Begins with spermatids Small, relatively unspecialized cells

Involves major structural changes Spermatids differentiate into mature spermatozoa Highly 2015 Pearson Education, Inc. specialized cells 28-2 Male Reproductive Functions Meiosis I and meiosis II Produce four haploid cells, each with 23 chromosomes (n) Prophase I Chromosomes condense Each chromosome has two chromatids Synapsis

Maternal and paternal chromosomes come together Four matched chromatids form tetrad Crossing over: exchange of genetic material that increases genetic variation among offspring 2015 Pearson Education, Inc. Metaphase I Tetrads line up along metaphase plate Independent assortment As each tetrad splits:

Maternal and paternal components are randomly distributed 28-2 Male Reproductive Functions Anaphase I Maternal and paternal chromosomes separate Each daughter cell receives whole chromosome Maternal or paternal Telophase I

2015 Pearson Education, Inc. Ends With formation of two daughter cells With unique combinations of chromosomes Both cells contain 23 chromosomes with two chromatids each (reductional division) 28-2 Male Reproductive Functions Mitosis and Meiosis Interphase Separates meiosis I and meiosis II Is very brief DNA is not replicated

2015 Pearson Education, Inc. 28-2 Male Reproductive Functions Mitosis and Meiosis Meiosis II Proceeds through prophase II and metaphase II Anaphase II Duplicate chromatids separate Telophase II

Yields four cells, each containing 23 chromosomes (equational division) 2015 Pearson Education, Inc. 28-2 Male Reproductive Functions Spermiogenesis Is the last step of spermatogenesis Each spermatid matures into one spermatozoon (sperm) Attached to cytoplasm of nurse cells

2015 Pearson Education, Inc. Spermiation At spermiation, a spermatozoon: Loses attachment to nurse cell Enters lumen of seminiferous tubule Spermatogonial division to spermiation Takes about nine weeks 28-2 Male Reproductive Functions

Nurse Cells Affect: Mitosis Meiosis Spermiogenesis in seminiferous tubules Six Major Functions of Nurse Cells 2015 Pearson Education, Inc.

Maintain bloodtestis barrier Support mitosis and meiosis Support spermiogenesis Secrete inhibin Secrete androgenbinding protein (ABP) Secrete Mllerianinhibiting factor (MIF) 28-2 Male Reproductive Functions Maintenance of BloodTestis Barrier Bloodtestis barrier isolates seminiferous tubules Nurse cells are joined by tight junctions that divide seminiferous tubule into compartments Outer basal compartment contains spermatogonia Inner luminal compartment is where meiosis and spermiogenesis occur

2015 Pearson Education, Inc. 28-2 Male Reproductive Functions Support of Mitosis and Meiosis Nurse cells are stimulated by: Follicle-stimulating hormone (FSH) Testosterone Stimulated nurse cells promote: Division of spermatogonia Meiotic divisions of spermatocytes 2015 Pearson Education, Inc. 28-2 Male Reproductive Functions

Support of Spermiogenesis Nurse cells Surround and enfold spermatids Provide nutrients and chemical stimuli for development Phagocytize cytoplasm shed by developing spermatids 2015 Pearson Education, Inc. 28-2 Male Reproductive Functions Secretion of Inhibin Inhibin Is a peptide hormone secreted by nurse cells in

response to factors released by spermatozoa Depresses: Pituitary production of FSH Hypothalamic secretion of GnRH Regulation 2015 Pearson Education, Inc. of FSH and GnRH by inhibin: Gives nurse cells feedback control of spermatogenesis After division, increases inhibin production 28-2 Male Reproductive Functions Secretion of Androgen-Binding Protein (ABP) Androgen-Binding Protein (ABP)

Binds Is androgens (primarily testosterone) In seminiferous tubule fluid important in: Elevating androgen in seminiferous tubules Stimulating spermiogenesis Production 2015 Pearson Education, Inc. of ABP is stimulated by FSH 28-2 Male Reproductive Functions Secretion of Mllerian-Inhibiting Factor (MIF)

Mllerian-Inhibiting Factor (MIF) Is secreted by nurse cells in developing testes Causes regression of fetal Mllerian (paramesonephric) ducts 2015 Pearson Education, Inc. Help form uterine tubes and uterus in females In males, inadequate MIF production leads to: Retention of ducts Failure of testes to descend into scrotum 28-2 Male Reproductive Functions The Anatomy of a Spermatozoon

Head Neck (attaches head to middle piece) Middle piece Tail 2015 Pearson Education, Inc. 28-2 Male Reproductive Functions The Anatomy of a Spermatozoon Head A flattened ellipse that contains nucleus and chromosomes Acrosome

2015 Pearson Education, Inc. A cap-like compartment at tip of head A membranous compartment that contains enzymes essential to fertilization Made of fused saccules of spermatids Golgi apparatus 28-2 Male Reproductive Functions The Anatomy of a Spermatozoon Middle piece Attached to head by short neck Contains mitochondria In spiral around microtubules Activity provides ATP to move tail Tail Is

the only flagellum in the human body Is a whiplike organelle Moves cell from one place to another Has complex, corkscrew motion 2015 Pearson Education, Inc. Figure 28-8 Spermiogenesis and Spermatozoon Structure (Part 1 of 2). Spermatid Mitochondria Nucleus Shed cytoplasm Golgi apparatus Acrosomal vesicle Acrosome Nucleus Acrosome Spermiogenesis. The differentiation of a spermatid into a spermatozoon. This

process is completed in approximately 24 days. 28-2 Male Reproductive Functions Mature Spermatozoon Lacks: Endoplasmic reticulum Golgi apparatus Lysosomes and peroxisomes Inclusions and other intracellular structures Loss of these organelles reduces sperm size and mass Sperm must absorb nutrients (fructose) from surrounding fluid 2015 Pearson Education, Inc.

28-2 Male Reproductive Functions The Male Reproductive Tract Sperm maturation Testes produce physically mature spermatozoa that CANNOT fertilize an oocyte Other parts of reproductive system are responsible for: 2015 Pearson Education, Inc. Functional maturation, nourishment, storage, and transport 28-2 Male Reproductive Functions The Male Reproductive Tract

Sperm maturation Spermatozoa 2015 Pearson Education, Inc. Detach from nurse cells Are free in lumen of seminiferous tubule Are functionally immature Are incapable of locomotion or fertilization Are moved by cilia lining efferent ductules into the epididymis 28-2 Male Reproductive Functions

The Epididymis Is the start of male reproductive tract Is a coiled tube almost 7 m (23 ft) long Bound to posterior border of testis 2015 Pearson Education, Inc. Has a head, a body, and a tail 28-2 Male Reproductive Functions

Epididymis Head Epididymis Body Is proximal to the testis Receives spermatozoa from efferent ductules From last efferent ductule to posterior margin of testis Epididymis Tail Begins near inferior border of testis where number of coils decreases Re-curves and ascends to connection with ductus deferens Primary storage location of spermatozoa

2015 Pearson Education, Inc. 2015 Pearson Education, Inc. 28-2 Male Reproductive Functions Three Functions of the Epididymis 1. 2. 3. Monitors and adjusts fluid produced by seminiferous tubules Recycles damaged spermatozoa Stores and protects spermatozoa 2015 Pearson Education, Inc. Facilitates functional maturation 28-2 Male Reproductive Functions

Spermatozoa Leaving Epididymis Are mature, but remain immobile To become motile (actively swimming) and functional: Spermatozoa undergo capacitation Two Steps in Capacitation 1. Spermatozoa become motile 2. When mixed with secretions of seminal glands Spermatozoa become capable of fertilization

2015 Pearson Education, Inc. When exposed to female reproductive tract 28-2 Male Reproductive Functions The Ductus Deferens (Vas Deferens) Is 4045 cm (1618 in.) long Begins at tail of the epididymis and, as part of spermatic cord, ascends through inguinal canal Curves inferiorly along urinary bladder Toward prostate gland and seminal glands Lumen enlarges into ampulla

Wall contains thick layer of smooth muscle 2015 Pearson Education, Inc. 28-2 Male Reproductive Functions The Ductus Deferens Is lined by ciliated epithelium Peristaltic contractions propel spermatozoa and fluid Can store spermatozoa for several months In 2015 Pearson Education, Inc. state of suspended animation (low metabolic rates) Figure 28-10a The Ductus Deferens and Accessory Glands. Ureter

Ductus deferens Urinary bladder Seminal gland Ampulla of ductus deferens Duct of seminal gland Ejaculatory duct Prostate gland Prostatic urethra a posterior view of the urinary A bladder and prostate gland, showing subdivisions of the ductus deferens in relation to surrounding structures. Bulbourethral glands Urogenital diaphragm Figure 28-10b The Ductus Deferens and Accessory Glands.

Lumen of ductus deferens Smooth muscle Ductus LM120 deferens b Light micrograph showing the thick layers of smooth muscle in the wall of the ductus deferens. 28-2 Male Reproductive Functions The Ejaculatory Duct Is a short passageway (2 cm; less than 1 in.)

At junction of ampulla and seminal gland duct Penetrates wall of prostate gland Empties into urethra The Urethra Is used by urinary and reproductive systems Extends 1820 cm (78 in.) from urinary bladder to tip of penis Is divided into three regions 1. 2. 3. 2015 Pearson Education, Inc.

Prostatic Membranous Spongy 28-2 Male Reproductive Functions The Accessory Glands Produce semen, which is a mixture of secretions from many glands Each with distinctive biochemical characteristics Important glands include: 1. 2. 3. 2015 Pearson Education, Inc. Seminal glands

Prostate gland Bulbourethral glands 28-2 Male Reproductive Functions Four Major Functions of Male Glands 1. 2. 3. Activating spermatozoa Providing nutrients spermatozoa need for motility Propelling spermatozoa and fluids along reproductive tract Mainly 4. by peristaltic contractions Producing buffers To

counteract acidity of urethral and vaginal environments 2015 Pearson Education, Inc. 28-2 Male Reproductive Functions The Seminal Glands (Seminal Vesicles) Each gland is about 15 cm (6 in.) long with short side branches from body Are tubular glands coiled and folded into 5 cm by 2.5 cm (2 in. 1 in.) mass Are extremely active secretory glands Produce about 60 percent of semen volume 2015 Pearson Education, Inc. 28-2 Male Reproductive Functions

Seminal Fluid Has same osmotic concentration as blood plasma but different composition High concentrations of fructose easily metabolized by spermatozoa Prostaglandins stimulate smooth muscle contractions (male and female) Fibrinogen forms temporary clot in vagina Is slightly alkaline To 2015 Pearson Education, Inc. neutralize acids in prostate gland and vagina 28-2 Male Reproductive Functions

Seminal Fluid Initiates first step in capacitation Spermatozoa begin beating flagella, become highly motile Is discharged into ejaculatory duct at emission When peristaltic contractions are under way Contractions are controlled by sympathetic nervous system 2015 Pearson Education, Inc. The Accessory Glands 28-2 Male Reproductive Functions

The Prostate Gland Is a small, muscular organ, about 4 cm (1.6 in.) in diameter Encircles proximal portion of urethra Below urinary bladder Consists of 3050 compound tubuloalveolar glands Surrounded by smooth muscle fibers 2015 Pearson Education, Inc. 28-2 Male Reproductive Functions

Prostatic Fluid Is slightly acidic Forms 2030 percent of semen volume Contains antibiotic seminalplasmin Is ejected into prostatic urethra By 2015 Pearson Education, Inc. peristalsis of prostate wall 28-2 Male Reproductive Functions The Bulbourethral Glands (Cowpers Glands)

Are compound, tubular mucous glands Round shaped, up to 10 mm (less than 0.5 in.) diameter Located at base of penis Covered by fascia of urogenital diaphragm 2015 Pearson Education, Inc. 28-2 Male Reproductive Functions The Bulbourethral Glands (Cowpers Glands) Secrete thick, alkaline mucus Helps neutralize urinary acids in urethra Lubricates the glans (penis tip) Duct of each gland travels alongside penile urethra and empties into urethral lumen

2015 Pearson Education, Inc. 28-2 Male Reproductive Functions Semen Typical ejaculation releases 25 mL Abnormally low volume may indicate problems With prostate gland or seminal glands Sperm count Is taken of semen collected after 36 hours of sexual abstinence Normal range 20100 million spermatozoa/mL of ejaculate 2015 Pearson Education, Inc.

28-2 Male Reproductive Functions Ejaculate Is the volume of fluid produced by ejaculation Contains: Spermatozoa Seminal fluid Enzymes Including protease, seminalplasmin, prostatic enzyme, and fibrinolysin 2015 Pearson Education, Inc. 28-2 Male Reproductive Functions Male External Genitalia The penis Is

a tubular organ through which distal portion of urethra passes Conducts urine to exterior Introduces semen into females vagina 2015 Pearson Education, Inc. 28-2 Male Reproductive Functions The Penis The root Is the fixed portion that attaches penis to body wall Attachment occurs within urogenital triangle, inferior to pubic symphysis The body (shaft) Is

the tubular, movable portion of the penis Consists of three cylindrical columns of erectile tissue The glans Is the expanded distal end of penis that surrounds external urethral orifice 2015 Pearson Education, Inc. 2015 Pearson Education, Inc. 28-2 Male Reproductive Functions Dermis of the Penis Contains a layer of smooth muscle A continuation

Underlying areolar tissue Allows of dartos muscle skin to move freely Subcutaneous layer Contains vessels 2015 Pearson Education, Inc. superficial arteries, veins, and lymphatic 28-2 Male Reproductive Functions The Prepuce (Foreskin)

Is a fold of skin surrounding tip of penis Attaches to neck and continues over glans Preputial glands In skin of neck and inner surface of prepuce Secrete waxy material (smegma) that can support bacteria Circumcision can help prevent infection 2015 Pearson Education, Inc. 28-2 Male Reproductive Functions Erectile Tissue In body of penis Located deep to areolar tissue In dense network of elastic fibers That

encircles internal structures of penis Consists of network of vascular channels Incompletely separated by partitions of elastic connective tissue and smooth muscle fibers In resting state: Arterial branches are constricted Muscular partitions are tense Blood flow into erectile tissue is restricted 2015 Pearson Education, Inc. 28-2 Male Reproductive Functions The Corpora Cavernosa

Two cylindrical masses of erectile tissue Under anterior surface of flaccid penis Separated by thin septum Encircled by dense collagenous sheath Diverge at their bases, forming the crura of penis Each crus is bound to ramus of ischium and pubis By tough connective tissue ligaments Extend to neck of penis Erectile tissue surrounds a central artery 2015 Pearson Education, Inc. 28-2 Male Reproductive Functions

The Corpus Spongiosum Relatively slender erectile body that surrounds penile urethra Extends from urogenital diaphragm to tip of penis and expands to form the glans Is surrounded by a sheath With more elastic fibers than corpora cavernosa Erectile tissue contains a pair of small arteries 2015 Pearson Education, Inc. 28-2 Male Reproductive Functions

Hormones and Male Reproductive Function Anterior lobe of the pituitary gland releases: Follicle-stimulating hormone (FSH) Luteinizing hormone (LH) In response to: Gonadotropin-releasing 2015 Pearson Education, Inc. hormone (GnRH) 28-2 Male Reproductive Functions Gonadotropin-Releasing Hormone Is synthesized in hypothalamus Carried

Is secreted in pulses At to pituitary by hypophyseal portal system 6090 minute intervals Controls rates of secretion of: FSH and LH Testosterone (released in response to LH) 2015 Pearson Education, Inc. 28-2 Male Reproductive Functions FSH and Testosterone

Target nurse cells of seminiferous tubules Nurse cells Promote spermatogenesis and spermiogenesis Secrete androgen-binding protein (ABP) 2015 Pearson Education, Inc. 28-2 Male Reproductive Functions Negative Feedback Spermatogenesis is regulated by: GnRH, As spermatogenesis accelerates: Inhibin FSH, and inhibin

secretion increases Inhibin Inhibits FSH production In anterior lobe of the pituitary gland Suppresses secretion of GnRH At 2015 Pearson Education, Inc. hypothalamus 28-2 Male Reproductive Functions Inhibin and FSH Elevated FSH

levels Increase inhibin production Until FSH returns to normal If FSH declines: Inhibin production falls FSH production increases 2015 Pearson Education, Inc. Luteinizing Hormone Targets interstitial cells of testes Induces secretion of: Testosterone

Other androgens 28-2 Male Reproductive Functions Testosterone Is the most important androgen Stimulates spermatogenesis Promoting Affects CNS function Libido functional maturation of spermatozoa (sexual drive) and related behaviors Stimulates metabolism Especially

protein synthesis Blood cell formation Muscle growth 2015 Pearson Education, Inc. 28-2 Male Reproductive Functions Testosterone Establishes male secondary sex characteristics Distribution of facial hair Increased muscle mass and body size Characteristic adipose tissue deposits Maintains accessory glands and organs of male reproductive tract

2015 Pearson Education, Inc. Male reproductive function is regulated by the complex interaction of hormones from the hypothalamus, anterior lobe of the pituitary gland, and the testes. Negative feedback systems keep testosterone levels within a relatively narrow range until late in life. ? Figure 28-12 Regulation of Male Reproduction (Part 1 of 2). HYPOTHALAMUS Negative feedback Release of GonadotropinReleasing Hormone (GnRH) High testosterone levels inhibit the release of The hypothalamus secretes GnRH the hormone GnRH at a by the hypothalamus, rate

causing a decrease in that remains relatively LH secretion, which steady. lowers testosterone to As a result, blood levels of normal levels. FSH, LH, and testosterone remain within a relatively narrow range throughout a When stimulated by GnRH, the mans reproductive life. anterior lobe of the pituitary gland releases luteinizing hormone (LH) and follicle-stimulating hormone (FSH). Secretion of FollicleStimulating Inhibin depresses the Hormone pituitary production FSH targets primarily (FSH) of FSH, and perhaps the nurse cells of the the hypothalamic

seminiferous secretion of tubules. gonadotropinreleasing hormone (GnRH).The faster the rate of sperm production, the more inhibin is secreted. By regulating FSH and GnRH secretion, nurse cells provide ANTERIOR LOBE OF THE PITUITARY GLAND Secretion of Luteinizing Hormone (LH) LH targets the interstitial cells of the testes.

KEY Stimulation Inhibition Negative feedback Figure 28-12 Regulation of Male Reproduction (Part 2 of 2). Inhibin Interstitial Cell Stimulation TESTES LH induces the secretion of testosterone and other androgens by the interstitial cells of the testes. Testosterone Nurse Cell Stimulation Under FSH stimulation, and with testosterone from the interstitial

cells, nurse cells (1) secrete inhibin in response to factors released by developing spermatozoa, (2) secrete androgen-binding protein (ABP), and (3) promote spermatogenesis and spermiogenesis. Androgen-binding protein (ABP) binds androgens within the seminiferous tubules, which increases the local concentration of androgens and stimulates the physical maturation of spermatids. Nurse cell environment facilitates both spermatogenesi s and spermiogenesis. KEY

Stimulation Inhibition Peripheral Effects of Testosterone Maintains libidoStimulates Establishes andMaintains (sexual drive) bone and maintains male accessory glands and related muscle secondary sex and organs behaviors growth characteristics of the male reproductive system 28-2 Male Reproductive Functions Testosterone Functions like other steroid hormones Diffuses across target cell membrane Binds to intracellular receptor

Hormonereceptor complex Binds to DNA in nucleus Circulating in bloodstream Bound to one of two types of transport proteins 2015 Pearson Education, Inc. Gonadal steroid-binding globulin (GBG) carries 2/3 of circulating testosterone Albumins carry 1/3 of testosterone 28-2 Male Reproductive Functions Testosterone and Development

Production begins around seventh week of fetal development and reaches prenatal peak after six months Secretion of Mllerian-inhibiting factor by nurse cells leads to regression of Mllerian ducts Early surge in testosterone levels stimulates differentiation of male duct system and accessory organs and affects CNS development 2015 Pearson Education, Inc. 28-2 Male Reproductive Functions Testosterone and Development Testosterone programs hypothalamic centers that control: 1. 2. 3.

2015 Pearson Education, Inc. GnRH, FSH, and LH secretion Sexual behaviors Sexual drive 28-2 Male Reproductive Functions Estradiol Is produced in relatively small amounts (2 ng/dL) 70 percent is converted from circulating testosterone By enzyme aromatase 30 percent is secreted by interstitial and nurse cells of testes 2015 Pearson Education, Inc.

28-3 The Female Reproductive System The Female Reproductive System Produces sex hormones and functional gametes Protects and supports developing embryo Nourishes newborn infant Organs of the Female Reproductive System Ovaries Uterine tubes Uterus Vagina

External genitalia 2015 Pearson Education, Inc. Figure 28-13 The Female Reproductive System 28-3 The Female Reproductive System Structural Support Ovaries, uterine tubes, and uterus are enclosed in broad ligament Uterine tubes Run along broad ligament Open into pelvic cavity lateral to ovaries The mesovarium Stabilizes

2015 Pearson Education, Inc. position of each ovary Figure 28-14b The Ovaries and Their Relationships to the Uterine Tube and Uterus. Uterine tube Mesenteries of the Ovary and Uterine Tube Mesosalpi nx Corpus luteum Cortex Tunica albugine a Mesovariu m

Broad ligament Ovarian Egg Germinal Mature hilum nest epitheliu follicle m b A sectional view of the ovary, uterine tube, and associated mesenteries 28-3 The Female Reproductive System Ovaries Are small, almond-shaped organs near lateral walls of pelvic cavity Three main functions 1. 2. 3.

2015 Pearson Education, Inc. Production of immature female gametes (oocytes) Secretion of female sex hormones (estrogens, progestins) Secretion of inhibin, involved in feedback control of pituitary FSH 28-3 The Female Reproductive System Ovary Support Mesovarium Ovarian ligament extends from uterus to ovary Suspensory ligament extends from ovary to pelvic wall Contains the ovarian artery and ovarian vein These vessels connect to ovary at ovarian hilum, where ovary attaches to mesovarium

2015 Pearson Education, Inc. 28-3 The Female Reproductive System The Visceral Peritoneum of the Ovary Also called germinal epithelium Covers surface of ovary Consists of columnar epithelial cells Overlies tunica albuginea 2015 Pearson Education, Inc. 28-3 The Female Reproductive System The Stroma Are interior tissues of ovary

Superficial cortex Deeper medulla Gametes are produced in cortex 2015 Pearson Education, Inc. 28-3 The Female Reproductive System Oogenesis Also called ovum production Begins before birth Accelerates at puberty

Ends at menopause 2015 Pearson Education, Inc. 28-3 The Female Reproductive System Fetal Development Between third and seventh months: Primary Stop oocytes prepare for meiosis at prophase of meiosis I Atresia Is the degeneration of primordial follicles

Ovaries have about 2 million primordial follicles at birth Each containing a primary oocyte By puberty: Number 2015 Pearson Education, Inc. drops to about 400,000 28-3 The Female Reproductive System Process of Oogenesis Primary oocytes remain in suspended development until puberty At puberty:

Rising FSH triggers start of ovarian cycle Each month thereafter: Some further primary oocytes are stimulated to develop 2015 Pearson Education, Inc. 28-3 The Female Reproductive System Oogenesis: Two Characteristics of Meiosis 1. Cytoplasm of primary oocyte divides unevenly Producing one ovum (with original cytoplasm) And two or three polar bodies (that disintegrate)

2. Ovary releases secondary oocyte (not mature ovum) Suspended in metaphase of meiosis II Meiosis is completed upon fertilization 2015 Pearson Education, Inc. 28-3 The Female Reproductive System The Ovarian Cycle After sexual maturation A different group of primordial follicles is activated each month Is divided into: Follicular

phase (preovulatory phase) Luteal phase (postovulatory phase) Ovarian follicles Are specialized structures in cortex of ovaries Where oocyte growth and meiosis I occur Primary oocytes Are located in outer part of ovarian cortex Near tunica albuginea In clusters called egg nests 2015 Pearson Education, Inc. 28-3 The Female Reproductive System Primordial Follicle Each primary oocyte in an egg nest Is

surrounded by follicle cells Primary oocyte and follicle cells form a primordial follicle 2015 Pearson Education, Inc. 28-3 The Female Reproductive System The Uterine Tubes Also called Fallopian tubes or oviducts Are hollow, muscular tubes about 13 cm

(5.2 in.) long Transport oocyte from ovary to uterus 2015 Pearson Education, Inc. 28-3 The Female Reproductive System Three Segments of the Uterine Tubes 1. Infundibulum An expanded funnel near ovary With fimbriae that extend into pelvic cavity Inner surfaces lined with cilia that beat toward middle segment 2. Ampulla Middle segment Smooth muscle layers in wall become thicker approaching

uterus 3. Isthmus A short 2015 Pearson Education, Inc. segment between ampulla and uterine wall 28-3 The Female Reproductive System Histology of the Uterine Tube Epithelium lining uterine tube Contains scattered mucin-secreting cells

Mucosa is surrounded by concentric layers of smooth muscle 2015 Pearson Education, Inc. 28-3 The Female Reproductive System Uterine Tube and Oocyte Transport Involves ciliary movement and peristaltic contractions in walls of uterine tube A few hours before ovulation, nerves from hypogastric plexus: Turn on beating pattern Initiate peristalsis From infundibulum to uterine cavity

Normally 2015 Pearson Education, Inc. takes three to four days 28-3 The Female Reproductive System Uterine Tube and Fertilization For fertilization to occur: Secondary oocyte must meet spermatozoa during first 12 24 hours Fertilization typically occurs: Near boundary between ampulla and isthmus

Uterine tube provides nutrient-rich environment by secretions from peg cells Containing lipids and glycogen Nutrients supply spermatozoa and developing preembryo 2015 Pearson Education, Inc. 28-3 The Female Reproductive System The Uterus Provides for developing embryo (weeks 18) and fetus (week 9 through delivery) Mechanical protection Nutritional support Waste removal

Is pear-shaped cm long, 5 cm diameter (3 in. 2 in.) Weighs 50100 g (1.753.5 oz) 7.5 Normally bends anteriorly near base (anteflexion) In 2015 Pearson Education, Inc. retroflexion, uterus bends backward 28-3 The Female Reproductive System Suspensory Ligaments of Uterus Uterosacral ligaments Prevent

Round ligaments Restrict inferioranterior movement posterior movement Cardinal (lateral) ligaments Prevent 2015 Pearson Education, Inc. inferior movement 28-3 The Female Reproductive System Uterine Body Is largest portion of uterus

Ends at isthmus Fundus Is rounded portion of uterine body Superior 2015 Pearson Education, Inc. to attachment of uterine tubes 28-3 The Female Reproductive System Cervix Is inferior portion of uterus Extends from isthmus to vagina Distal end projects about 1.25 cm (0.5 in.) into vagina

External os Also called external orifice of uterus Is surrounded by distal end of cervix Leads into cervical canal 2015 Pearson Education, Inc. 28-3 The Female Reproductive System Cervical Canal Is a constricted passageway opening to uterine cavity of body At 2015 Pearson Education, Inc. internal os (internal orifice) 28-3 The Female Reproductive System

Blood Supply of the Uterus Branches of uterine arteries Arising from branches of internal iliac arteries Ovarian arteries Arising from abdominal aorta Veins and lymphatic vessels 2015 Pearson Education, Inc.

28-3 The Female Reproductive System Nerves of the Uterus Autonomic fibers from hypogastric plexus (sympathetic) Sacral segments S3 and S4 (parasympathetic) Segmental blocks Anesthetic procedure used during labor Target spinal nerves T L 10 1 2015 Pearson Education, Inc. Figure 28-18a The Uterus (Part 2 of 2). Fundus

Uterine tube of uterus Suspensory ligament of ovary Ovarian artery and vein Mesovarium Body of uterus Ovary Uterine cavity Broad ligament Cervix Vagina a A posterior view with the left portion of

the uterus, left uterine tube, and left ovary shown in Ovarian ligament Round ligament of uterus Figure 28-18b The Uterus. Uterosacral ligament POSTERIOR Cardinal ligaments (under broad ligament) Sigmoid colon Suspensory ligament

of ovary Ovary Broad ligament Uterus Round ligament of uterus Urinary bladder Ovarian ligament Uterine tube Vesicouterine pouch ANTERIOR b A superior view of the ligaments that stabilize the position of the uterus in the pelvic

Figure 28-18c The Uterus. POSTERIOR Rectouterine pouch Ovary Ovarian ligament Uterine tube Uterus Vesicouterin e pouch ANTERIOR c Superior view of the female pelvic cavity showing supporting ligaments of uterus and ovaries. In the photo, the urinary bladder cannot be seen because it is covered by peritoneum. 28-3 The Female Reproductive System

The Uterine Wall Has a thick, outer, muscular myometrium Has a thin, inner, glandular endometrium (mucosa) The perimetrium Is an incomplete serous membrane Continuous with peritoneal lining Covers fundus and posterior surface of uterine body and isthmus 2015 Pearson Education, Inc. 28-3 The Female Reproductive System

The Myometrium The thickest portion of the uterine wall Constitutes almost 90 percent of the mass of the uterus Arranged into longitudinal, circular, and oblique layers Provides force to move fetus out of uterus into vagina 2015 Pearson Education, Inc. 28-3 The Female Reproductive System The Endometrium

Contributes about 10 percent of uterine mass Glandular and vascular tissues support physiological demands of growing fetus Uterine glands Open onto endometrial surface Extend deep into lamina propria Estrogen Causes uterine glands, blood vessels, and epithelium to change with of monthly uterine cycle 2015 Pearson Education, Inc. phases 28-3 The Female Reproductive System Two Divisions of Endometrium

1. The functional zone 2. Contains most of the uterine glands Contributes most of endometrial thickness Undergoes dramatic changes in thickness and structure during menstrual cycle The basilar zone 2015 Pearson Education, Inc. Attaches endometrium to myometrium Contains terminal branches of tubular endometrial glands 28-3 The Female Reproductive System

Blood Supply of Endometrium Arcuate arteries Encircle endometrium Radial arteries Supply straight arteries (to basilar zone) Supply spiral arteries (to functional zone) 2015 Pearson Education, Inc. 28-3 The Female Reproductive System Cyclical Changes in Endometrium

Basilar zone remains relatively constant Functional zone undergoes cyclical changes In response to sex hormone levels Produce characteristic features of uterine cycle 2015 Pearson Education, Inc. 28-3 The Female Reproductive System The Uterine Cycle (Menstrual Cycle) Is a repeating series of changes in endometrium Lasts from 21 to 35 days Average Responds to hormones of ovarian cycle Menses and proliferative phase Occur

28 days during ovarian follicular phase Secretory phase Occurs 2015 Pearson Education, Inc. during ovarian luteal phase 28-3 The Female Reproductive System Menses Is the degeneration of functional zone Occurs in patches

Is caused by constriction of spiral arteries Reducing blood flow, oxygen, and nutrients Weakened arterial walls rupture Releasing zone 2015 Pearson Education, Inc. blood into connective tissues of functional 28-3 The Female Reproductive System Menses Degenerating tissues break away, enter uterine

lumen Entire functional zone is lost Through external os and vagina Only functional zone is affected Deeper, 2015 Pearson Education, Inc. basilar zone is supplied by straight arteries Figure 28-20a The Appearance of the Endometrium during the Uterine Cycle. Perimetriu m Endometriu m Myometrium Uterin e gland

s Uterine cavity Basilar zone of endometrium Cervix MYOMETRIUM Menses LM 63 a The endometrium at menses 2015 Pearson Education, Inc. 28-3 The Female Reproductive System Menstruation

Is the process of endometrial sloughing Lasts one to seven days Sheds 3550 mL (1.21.7 oz) blood 2015 Pearson Education, Inc. 28-3 The Female Reproductive System The Proliferative Phase Epithelial cells of uterine glands Multiply and spread across endometrial surface Restore integrity of uterine epithelium Further growth and vascularization Completely

restores functional zone Occurs at same time as: Enlargement ovary 2015 Pearson Education, Inc. of primary and secondary follicles in 28-3 The Female Reproductive System The Proliferative Phase Is stimulated and sustained by: Estrogens secreted by developing ovarian follicles

Entire functional zone is highly vascularized Small arteries Spiral toward inner surface From larger arteries in myometrium 2015 Pearson Education, Inc. Figure 28-20b The Appearance of the Endometrium during the Uterine Cycle. Uterine cavity Uterin e gland s Uterine cavity Functional zone Myometrium

ENDOMETRIUM Basilar zone MYOMETRIUM Proliferative phase b The endometrium 2015 Pearson Education, Inc. LM 66 during the proliferative 28-3 The Female Reproductive System The Secretory Phase Endometrial glands enlarge, increasing rate of secretion Arteries of uterine wall Elongate

and spiral through functional zone Begins at ovulation and persists as long as corpus luteum remains intact Peaks about 12 days after ovulation Glandular activity declines Generally lasts 14 days Ends as corpus luteum stops producing stimulatory hormones 2015 Pearson Education, Inc. Figure 28-20c The Appearance of the Endometrium during the Uterine Cycle. Uterin e glands

Functional zone Secretory LM 52 phase c The endometrium during 2015 Pearson Education, Inc. the secretory phase of the uterine Detail of uterine glands Uterine cavity LM 150 28-3 The Female Reproductive System

Menarche Menopause The first uterine cycle Begins at puberty (age 1112) The termination of uterine cycles Age 4555 Amenorrhea Primary amenorrhea Failure

to initiate menses Transient secondary amenorrhea Interruption of six months or more Caused by physical or emotional stresses 2015 Pearson Education, Inc. 28-3 The Female Reproductive System The Vagina Is an elastic, muscular tube Extends between cervix and vestibule 7.59 cm (33.6 in.) long Highly distensible 2015 Pearson Education, Inc.

28-3 The Female Reproductive System The Vagina Cervix projects into vaginal canal Fornix is shallow recess surrounding cervical protrusion Lies parallel to: Rectum, posteriorly Urethra, anteriorly 2015 Pearson Education, Inc. 28-3 The Female Reproductive System Blood Supply of the Vagina

Is through vaginal branches of internal iliac (uterine) arteries and veins Innervation of the Vagina Hypogastric plexus Sacral nerves Branches of pudendal nerve 2015 Pearson Education, Inc. 28-3 The Female Reproductive System Three Functions of the Vagina 1. 2. 3. Passageway for elimination of menstrual fluids Receives spermatozoa during sexual intercourse

Forms inferior portion of birth canal 2015 Pearson Education, Inc. 28-3 The Female Reproductive System Anatomy and Histology of the Vagina The Vaginal Wall Contains a network of blood vessels and layers of smooth muscle Is moistened by: Secretions of cervical glands Water movement across permeable epithelium The Hymen

Is an elastic epithelial fold That partially blocks entrance to vagina Usually ruptured by sexual intercourse or tampon usage 2015 Pearson Education, Inc. 28-3 The Female Reproductive System Vaginal Muscles Two bulbospongiosus muscles extend along either side of vaginal entrance Vestibular bulbs Masses of erectile tissue that lie beneath the muscles Have same embryological origins as corpus spongiosum of penis 2015 Pearson Education, Inc.

28-3 The Female Reproductive System The Vaginal Epithelium Is nonkeratinized, stratified, and squamous Forms folds (rugae) Changes with ovarian cycle Vaginal Lamina Propria Is thick and elastic Contains small blood vessels, nerves, and lymph nodes 2015 Pearson Education, Inc. 28-3 The Female

Reproductive System The Vaginal Mucosa Is surrounded by elastic muscularis layer Layers of smooth muscle fibers Arranged in circular and longitudinal bundles Continuous with uterine myometrium 2015 Pearson Education, Inc. 28-3 The Female Reproductive System Vaginal Bacteria

A population of harmless resident bacteria Supported by nutrients in cervical mucus Creates acidic environment Restricts growth of many pathogens A Vaginal Smear Is a sample of epithelial cells shed at surface of vagina Used to estimate stage in ovarian and uterine cycles 2015 Pearson Education, Inc. 28-3 The Female Reproductive System The External Genitalia Vulva (or pudendum)

Area containing female external genitalia Vestibule A central space bounded by small folds (labia minora) Covered with smooth, hairless skin Urethra opens into vestibule Anterior to vaginal entrance 2015 Pearson Education, Inc. 28-3 The Female Reproductive System Paraurethral Glands

The Clitoris Also called Skenes glands Discharge into urethra near external opening A small protuberance in vestibule Has same embryonic structures as penis Extensions of labia minora form prepuce or hood Vestibular Glands Lesser vestibular glands Secrete onto exposed surface of vestibule Greater vestibular glands (or Bartholins glands) Secrete

2015 Pearson Education, Inc. into vestibule near vaginal entrance 28-3 The Female Reproductive System Mons Pubis and Labia Majora Form outer limits of vulva Protect and cover inner structures Contain adipose tissue Sebaceous glands and apocrine sweat glands Secrete onto inner

surface of labia majora 2015 Pearson Education, Inc. 28-3 The Female Reproductive System The Mammary Glands Secrete milk to nourish an infant (lactation) Are specialized organs of integumentary system Are controlled by hormones of reproductive system and the placenta Lie in pectoral fat pads deep to skin of chest Nipple on each breast Contains ducts from mammary glands to surface

Areola Reddish-brown skin around each nipple Consist of lobes Each containing several secretory lobules Separated by dense connective tissue 2015 Pearson Education, Inc. 28-3 The Female Reproductive System Suspensory Ligaments of the Breast Bands of connective tissue

Originate in dermis of overlying skin Areolar tissue separates mammary gland complex from underlying pectoralis muscles Blood Supply of Mammary Glands Branches of internal thoracic artery 2015 Pearson Education, Inc. 28-3 The Female Reproductive System Mammary Gland Ducts Leave lobules Converge Form single lactiferous duct in each lobe Lactiferous Duct

Enlarges Forms expanded chamber (lactiferous sinus) 1520 lactiferous sinuses open to each nipple 2015 Pearson Education, Inc. 28-3 The Female Reproductive System An Active Mammary Gland Is a tubuloalveolar gland Consisting of multiple glandular tubes Ending in secretory alveoli

Does not complete development unless pregnancy occurs 2015 Pearson Education, Inc. 28-3 The Female Reproductive System Hormones and the Female Reproductive Cycle Involve secretions of pituitary gland and gonads Form a complex pattern that coordinates ovarian and uterine cycles Circulating hormones Control female reproductive cycle Coordinate ovulation and uterus preparation

2015 Pearson Education, Inc. 28-3 The Female Reproductive System Hormones and the Female Reproductive Cycle GnRH from the hypothalamus regulates reproductive function GnRH pulse frequency and amplitude change over course of ovarian cycle Changes 2015 Pearson Education, Inc. in GnRH pulse frequency are controlled by: Estrogens that increase pulse frequency Progestins that decrease pulse frequency

28-3 The Female Reproductive System The Endocrine Cells Of anterior lobe of the pituitary Each group of endocrine cells: Responds to different GnRH pulse frequencies Is sensitive to some frequencies, insensitive to others Hormones and the Follicular Phase Begins with FSH stimulation Monthly Some primordial follicles develop into primary follicles

As follicles enlarge: Thecal 2015 Pearson Education, Inc. cells produce androstenedione 28-3 The Female Reproductive System Androstenedione Is a steroid hormone Is an intermediate in synthesis of estrogens and androgens Is absorbed by granulosa cells and converted to estrogens 2015 Pearson Education, Inc. 28-3 The Female Reproductive System

Interstitial Cells Scattered throughout ovarian stroma Also secrete small amounts of estrogens Circulating estrogens Are bound primarily to albumins Lesser amounts carried by gonadal steroid-binding globulin (GBG) Three 2015 Pearson Education, Inc. types: estradiol, estrone, and estriol 28-3 The Female Reproductive System

Estradiol Is most abundant Has most pronounced effects on target tissues Is dominant hormone prior to ovulation 2015 Pearson Education, Inc. 28-3 The Female Reproductive System Estrogen Synthesis Androstenedione is converted to testosterone Enzyme aromatase converts testosterone to estradiol Estrone and estriol are synthesized from androstenedione

2015 Pearson Education, Inc. Figure 28-25 Pathways of Steroid Hormone Synthesis in Males and Females. Cholesterol Aromatase Androstenedione Other Estrogens Estrone Progesterone Estriol Androgens In some tissues Progesterone Testosterone

Dihydrotestosterone Aromatase Estradiol KEY = Common pathways = Primary pathways in females = Primary pathways in males 28-3 The Female Reproductive System Five Functions of Estrogen 1. 2. Stimulates bone and muscle growth Maintains female secondary sex characteristics 3. Affects central nervous system (CNS) activity

4. 5. Such as body hair distribution and adipose tissue deposits Especially in the hypothalamus, where estrogens increase the sexual drive Maintains functional accessory reproductive glands and organs Initiates repair and growth of endometrium 2015 Pearson Education, Inc. Figure 28-24 Regulation Female Reproduction (Partin 3 of 6). The ovarian and uterineofcycles

must operate synchrony to ensure proper reproductive function. If the two cycles are not properly coordinated, infertility results. A female who doesnt ovulate cannot conceive, even if her uterus is perfectly normal. A female who ovulates normally, but whose uterus is not ready to support an embryo, will also be infertile. HYPOTHALAMUS As in males, GnRH from the hypothalamus regulates reproductive function in females. However, in females, GnRH levels change throughout the course of the ovarian cycle. 1 Release of Gonadotropin-Releasing Hormone (GnRH) The cycle begins with the release of GnRH, which stimulates the production and secretion of FSH and the

productionbut not the secretion of LH. KEY Stimulation Release of GnRH 2 Follicular Phase of the Ovarian Cycle The follicular phase begins when FSH stimulates some secondary follicles to develop into a tertiary follicle. Production and secretion of FSH ANTERIOR LOBE OF PITUITARY GLAND

Inhibition 3 Production of LH Secretion of LH As secondary follicles develop, FSH levels decline due to the negative feedback effects of inhibin. Negative feedback Luteal Phase of the Ovarian Cycle The combination of increased GnRH pulse frequency and elevated estrogen levels stimulates LH secretion. On or around day 14, a massive surge in LH level triggers (1) the completion of meiosis I by the primary oocyte, (2) the forceful rupture of the follicular wall, (3) ovulation, roughly 9 hours after the LH peak, and (4) formation

of the corpus luteum. Figure 28-24 Regulation of Female Reproduction (Part 4 of 6). 2 Follicular Phase of the Ovarian Cycle 3 Developing follicles also secrete estrogens, especially estradiol, the dominant hormone prior to ovulation. In low concentrations, estrogens inhibit LH secretion. This inhibition gradually decreases as estrogen levels increase. OVARY Before day 10

Effects on CNS Follicle development Secretion of inhibin Secretion of estrogens Stimulation Establishment and maintenance of of bone and muscle growth female secondary sex characteristics After day 10 Meisois I completion Ovulation

Corpus luteum formation Secretion of progesterone Maintenance of accessory glands and organs Stimulation of endometrial growth and secretion Luteal Phase of the Ovarian Cycle The corpus luteum secretes progesterone, which stimulates and sustains endometrial development. After ovulation, progesterone levels rise and estrogen levels fall.

This suppresses GnRH secretion. If pregnancy does not occur, the corpus luteum will degenerate after 12 days, and as progesterone levels decrease, GnRH secretion increases, and a new cycle begins. KEY Stimulation Inhibition Figure 28-24 Regulation of Female Reproduction (Part 5 of 6). FOLLICULAR PHASE OF OVARIAN CYCLE LUTEAL PHASE OF OVARIAN CYCLE 50 LH 40 Gonadotropic 30 hormone levels (IU/L)

20 GnRH pulse frequency (pulses/day) FSH 10 Follicle stages during the ovarian cycle Follicle development Ovulation Corpus luteum formation Mature corpus luteum Corpus albicans Progesterone

Ovarian hormone levels Estrogens Inhibin 28/0 7 14 Days 21 28/0 Figure 28-24 Regulation of Female Reproduction (Part 6 of 6). FOLLICULAR PHASE OF OVARIAN CYCLE Destruction of functional zone

Endometrial change during thes uterine cycle Phases of the uterine cycle Repair and regeneration of functional zone Secretion by uterine glands PROLIFERATIVE PHASE MENSES LUTEAL PHASE OF OVARIAN CYCLE SECRETORY PHASE 36.7

Basal body temperature (C) 36.4 28/0 7 14 Days 21 28/0 28-3 The Female Reproductive System Summary: Hormonal Regulation of the Female Reproductive Cycle Early in follicular phase of ovarian cycle: Estrogen

levels are low GnRH pulse frequency is 1624/day (1 per 6090 minutes) As tertiary follicles form, concentration of circulating estrogens rises steeply 2015 Pearson Education, Inc. And GnRH pulse frequency increases to 36/day (1 per 3060 minutes) 28-3 The Female Reproductive System Summary: Hormonal Regulation of the Female Reproductive Cycle In follicular phase: Switchover 2015 Pearson Education, Inc.

occurs When estrogen levels exceed threshold value for about 36 hours Resulting in massive release of LH from the anterior lobe of the pituitary gland 28-3 The Female Reproductive System Summary: Hormonal Regulation of the Female Reproductive Cycle In follicular phase: Sudden 1. 2. 3. surge in LH concentration triggers: Completion of meiosis I by primary oocyte Rupture of follicular wall Ovulation

Ovulation occurs 3438 hours after LH surge begins (nine hours after LH peak) 2015 Pearson Education, Inc. 28-3 The Female Reproductive System Summary: Hormonal Regulation of the Female Reproductive Cycle In luteal phase of ovarian cycle: High LH levels trigger ovulation Promote progesterone secretion Trigger formation of corpus luteum Frequency

of GnRH pulses stimulates LH more than FSH 2015 Pearson Education, Inc. LH maintains structure and secretory function of corpus luteum 28-3 The Female Reproductive System Summary: Hormonal Regulation of the Female Reproductive Cycle Luteal phase Progesterone levels remain high for one week Unless pregnancy occurs, corpus luteum begins to degenerate Progesterone and estrogen levels drop GnRH pulse frequency increases

2015 Pearson Education, Inc. Stimulating FSH secretion Ovarian cycle begins again 28-3 The Female Reproductive System Hormones and the Uterine Cycle Corpus luteum degenerates Progesterone and estrogen levels decline Resulting in menses Endometrial tissue sheds several days Until

rising estrogen stimulates regeneration of functional zone Proliferative phase continues Until rising progesterone starts secretory phase Increase in estrogen and progesterone Causes enlargement of endometrial glands And increase in secretory activities 2015 Pearson Education, Inc. 28-3 The Female Reproductive System Hormones and Body Temperature Monthly hormonal fluctuations affect core body

temperature During luteal phase, progesterone dominates During follicular phase, estrogen dominates and basal body temperature decreases about 0.3C Upon ovulation, basal body temperature (BBT) declines noticeably Day after ovulation, temperature rises 2015 Pearson Education, Inc. 28-4 Sexual Function Autonomic Function Controls the Reproductive System Coitus (Copulation) Sexual

2015 Pearson Education, Inc. intercourse Introduces semen into female reproductive tract 28-4 Sexual Function Male Sexual Function Is coordinated by complex neural reflexes Using sympathetic and parasympathetic divisions of ANS Male sexual arousal Leads to increase in parasympathetic outflow over pelvic nerves, which leads to erection

2015 Pearson Education, Inc. 28-4 Sexual Function Male Sexual Stimulation Initiates secretion of bulbourethral glands Lubricates penile urethra and surface of glans Leads to coordinated processes of emission and ejaculation 2015 Pearson Education, Inc. 28-4 Sexual Function Emission Occurs under sympathetic stimulation

Peristaltic contractions of ampulla Push fluid and spermatozoa into prostatic urethra Seminal glands contract Increasing Peristaltic contractions in prostate gland Move in force and duration seminal mixture into urethra Sympathetic contraction of urinary bladder and internal urethral sphincter Prevents 2015 Pearson Education, Inc.

passage of semen into bladder 28-4 Sexual Function Ejaculation Occurs as powerful, rhythmic contractions In ischiocavernosus and bulbospongiosus muscles That stiffen penis Push semen toward external urethral opening Causes pleasurable sensations (orgasm) Followed by subsidence of erectile tissue (detumescence) 2015 Pearson Education, Inc. 28-4 Sexual Function

Impotence Also called male sexual dysfunction Is an inability to achieve or maintain an erection Caused by physical or psychological factors 2015 Pearson Education, Inc. 28-4 Sexual Function Female Sexual Function Parasympathetic activation leads to: Engorgement of erectile tissues Increased secretion of cervical mucous glands and greater vestibular glands

Blood vessels in vaginal walls fill with blood Fluid moves from underlying connective tissues To 2015 Pearson Education, Inc. vaginal surfaces 28-4 Sexual Function Female Orgasm Is accompanied by: Peristaltic contractions of uterine and vaginal walls Rhythmic contractions of bulbospongiosus and ischiocavernosus muscles 2015 Pearson Education, Inc. 28-4 Sexual Function

Sexually Transmitted Diseases (STDs) Are transferred by sexual intercourse Include bacterial, viral, and fungal infections Pelvic inflammatory disease (PID) AIDS Gonorrhea Syphilis Herpes Genital warts Chancroid 2015 Pearson Education, Inc. 28-5 Effects of Aging on the Reproductive System Effects of Aging

Female reproductive system Changes associated with menopause Male reproductive system Changes associated with male climacteric (andropause) Occur gradually, over longer time period 2015 Pearson Education, Inc. 28-5 Effects of Aging on the Reproductive System Menopause

Is the time that ovulation and menstruation cease Typically occurs around age 4555 Circulating concentrations of estrogens and progesterone decline Production of GnRH, FSH, and LH rises sharply 2015 Pearson Education, Inc. 28-5 Effects of Aging on the Reproductive System Perimenopause The interval immediately preceding menopause Ovarian and uterine cycles become irregular Due to shortage of primordial follicles Estrogen levels decline Ovulation is not triggered

Decline in Estrogen Levels Leads to: Reduction in uterus and breast size Thinning of urethral and vaginal epithelia Reduction in bone deposition (osteoporosis) 2015 Pearson Education, Inc. 28-5 Effects of Aging on the Reproductive System The Male Climacteric (Andropause) Is the period of declining reproductive function Circulating testosterone begins to decline Between

ages 50 and 60 Circulating FSH and LH increase Sperm production continues Sexual activity gradually decreases With 2015 Pearson Education, Inc. declining testosterone levels 28-6 Sex Hormones and Homeostasis Males Sperm count must be adequate Semen must have correct pH and

nutrients Erection and ejaculation must function properly Females Ovarian and uterine cycles must coordinate properly Ovulation and oocyte transport must occur normally Environment of reproductive tract must support: 2015 Pearson Education, Inc. Survival and movement of

sperm Fertilization of oocyte Table 28-1 Hormones of the Reproductive System. 28-6 Reproductive System Integration Human Reproduction Requires normal function of multiple systems Reproductive system Digestive system Endocrine system Nervous system Cardiovascular system Urinary system 2015 Pearson Education, Inc. Figure 28-26 diagrams the functional relationships system S Y S Tbetween

E M the I Nreproductive T E G R A T O and R the other body systems. Covers external genitalia; provides sensations that stimulate sexual behaviors; mammary gland secretions nourish the newborn Reproductive hormones affect distribution of body hair and subcutaneous fat deposits Pelvis protects reproductive organs of females, portion of ductus deferens and accessory glands in males Sex hormones stimulate growth and maintenance of bones; sex hormones at puberty accelerate growth and closure of epiphyseal cartilages

Contractions of skeletal muscles eject semen from male reproductive tract; muscle contractions during sexual act produce pleasurable sensations in both sexes Reproductive hormones, especially testosterone, accelerate skeletal muscle growth Controls sexual behaviors and sexual function Sex hormones affect CNS development and sexual behaviors Integumenta ry Body System

Skeletal Reproductive System Muscula r Skeletal Page 174 Muscula r Page 285 Page 380 Nervous Reproductive System Nervous Integumenta

ry Body System Provides oxygen and removes carbon dioxide generated by tissues of reproductive system and (in pregnant women) by a growing embryo and fetus Lysozymes and bactericidal chemicals in secretions provide innate immunity against reproductive tract infections Page 824 Changes in respiratory rate and depth occur during sexual arousal, under control of the nervous system Page 874 The Male Reproductive System In pregnant women, digestive organs are crowded by

developing fetus, constipation is common, and appetite increases Urethra in males carries semen to exterior; kidneys remove wastes generated by reproductive tissues and (in pregnant women) by a growing embryo and fetus Accessory organ secretions may have antibacterial action that helps prevent urethral infections in males Figure 2826 diagrams the functional relationships between the reproductive system and the other body systems. Endocrine Page 776 Provides additional nutrients required to support gamete production and (in pregnant women) embryonic and

fetal development The REPRODUCTIVE System Lymphatic Cardiovascula r Provides IgA for secretions by epithelial glands; assists in repairs and defense against infection Page 647 Estrogens may help maintain healthy vessels and slow development of atherosclerosis Respirator y Distributes reproductive hormones; provides nutrients, oxygen, and waste removal for fetus; local blood pressure changes responsible for physical changes during sexual arousal

Steroid sex hormones and inhibin inhibit secretions from the hypothalamus and pituitary gland Digestive Hypothalamic regulatory hormones and pituitary hormones regulate sexual development and function; oxytocin stimulates smooth muscle contractions in uterus and mammary glands Page 929 Urinary Urinary Digestive Respirator y Lymphatic Cardiovascula

r Endocrine Page 558 Page 1010 For all systems, the reproductive system secretes hormones with effects on growth and metabolism.

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