chapter 28: the reproductive system primary sources for figures and content: marieb, e. n. human...

Chapter 28:

The Reproductive System

Primary sources for figures and content:

Marieb, E. N. Human Anatomy & Physiology. 6th ed. San Francisco: Pearson Benjamin Cummings, 2004.

Martini, F. H. Fundamentals of Anatomy & Physiology. 6th ed. San Francisco: Pearson Benjamin Cummings, 2004.


• Primary sex organs = gonads– Gonads: organs that produce gametes and hormones

• Gametes = sex cells; ovum and sperm• Sex cells are Haploid (n):

– have half normal chromosome number (23 vs. 46)• All human tissue = somatic cells are Diploid (2n)

– 46 chromosomes, 23 homologous pairs• (1) 1n/23 chrom. ovum + (1) 1n/23 chrom. sperm (1)

2n/46 chromosome zygote, fertilized ovum• Zygote will divide by mitosis to produce all diploid

somatic cells of the body

Male and Female Reproductive Systems

• Are functionally different• Female produces 1 gamete per month:

– retains and nurtures zygote• Male disseminates large quantities of

gametes:– produces 1/2 billion sperm per day


• Gametogenesis– Process of gamete formation– 2n somatic cells produce 1n sex cells– Reducing chromosome number by

half requires special cell division meiosis

Chromosomes in Mitosis and Meiosis

Figure 28–6

Mitosis• 2n (duplicated) cell two 2n daughter cells • All daughter cells are identical• One 2n cell duplicates its DNA:

– each duplicated chromosome consists of two sister chromatids

• Sister chromatids are separated equally during anaphase– Now single chromosomes are in each new

daughter cell• Two identical diploid daughter cells result• Process of cell division used by all somatic cells

Meiosis• 2n (duplicated) four 1n daughter cells• All daughter cells are different• One 2n cell duplicates its DNA

– Each duplicated chromosome consists of two sister chromatids

• Homologous chromosome undergo synapsis– Pair up forming tetrads

•Tetrads = four sister chromatids or 2 duplicated chromosomes

• Homologous chromosomes exchange by cross-over

Meiosis

• In Meiosis I homologous chromosomes separate– Cells now haploid with duplicated chromosomes

• In Meiosis II sister chromatids separate (now single chromosomes)– Producing four haploid cells, all genetically different

• Process of cell division only used for sex cell production

Male Reproductive System

The Male Reproductive System

• Consists of– male gonads = testes

•secrete male sex hormones (androgens)•produce male gametes (spermatozoa or sperm)

– Accessory reproductive organs•Ducts•Glands•External genitalia that aid sperm

production/delivery

Summary: Male Reproductive System

• Emission:– mature spermatozoa move along duct

system• Semen:

– sperm mixed with accessory gland secretions

• Ejaculation:– semen expelled from body

Figure 28–1

The Male Reproductive System

Male Reproductive System FlythroughPLAYPLAY

Pathway of Spermatozoa

• Testis• Epididymis• Ductus deferens (vas deferens)• Ejaculatory duct• Urethra

Accessory Organs

• Secrete fluids into ejaculatory ducts and urethra:– seminal vesicles– prostate gland– bulbourethral glands

Male Reproductive System

Figure 28–3

Scrotum

• Sac of cutaneous membrane, fascia, and muscle• External to abdominopelvic cavity• 2 chambers, divided by raphae

– Each supports one testis• Maintains testes at optimal temp for sperm

development (36.2°C/96.5°F)– Normal sperm development in testes requires

temperatures 1.1°C (2°F) lower than body temperature

• Two muscles regulate temp.1. Dartos muscle2. Cremaster muscle

Scrotum• Two muscles regulate temp.

1. Dartos muscle•Smooth muscle in the dermis•Causes surface wrinkling to reduce heat

loss2. Cremaster muscle

•Skeletal muscle from internal obliques•Adjusts proximity of the testes to the

body–Tenses scrotum and pulls testes

closer to body (temperature regulation)

Testes

• = male gonads• Produce gamates (sperm) and hormones:

androgens (testosterone) and inhibin• Development

– Form in abdominal cavity•Same tissue and position as ovaries

– Descend prior to birth through inguinal canal•Are passageways through abdominal

musculature

The Fetus

• 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

Descent of the Testes

• During seventh month:– fetus grows rapidly

• Circulating hormones:– stimulate contraction of gubernaculum

testis• Each testis:

– moves through abdominal musculature– are accompanied by pockets of

peritoneal cavity

Figure 28–2a


Figure 28–2b


Accessory Structures

• Accompany testis during descent• Form body of spermatic cord:

– ductus deferens– testicular blood vessels, nerves, and

lymphatic vessels

Problems with Descent

1. Cryptorchidism– Failure of restes to descen– 3% full term, 30% premature births– Internal testis will be sterile

2. Male Inguinal Hernias– Are protrusions of visceral tissues,

intestines, into inguinal canal– Spermatic cord (in closed inguinal canal):

•causes weak point in abdominal wall

Testes

• Structure– Surrounded by two tunics

1. Tunica vaginalis– Derived from peritoneum

»Parietal and visceral layers

2. Tunica albuginea– Fibrous capsule of testis– Partitions of tunica albuginea divides testis

into lobules»Each lobule contains 1-4 coiled

seminiferous tubules

Structure of the Testes

Figure 28–4

Testes• Seminiferous tubules converge into rete testis

(inside the testis) efferent ductules (superior and exterior to testis) single epididymis (coiled around outside of testis)

• Epididymis transmits sperm to ductus/vas deferens– Connects testis to urethra

• Testes connected to abdominopelvic cavity by spermatic cord. Composed of:

• CT surrounding ductus deferens• Blood and lymphatic vessels• Autonomic nerves supplying testes

– Vasectomy = Surgical sterilization• Sever ductus deferens in spermatic cord

Testes

Figure 28–9

Testes• Functional regions of testes

1. Interstitial cells• In CT around seminiferous tubules• Produce androgens (testosterone)

2. Seminiferous tubules• Surrounded by capsule and areolar CT

outer edge lined with spermatogonia – Spermatogonia = sperm stem cell

• Spermatogonia divide and differentiate to produce spermatozoa for release into lumen

• Also contain sustentacular cells– Aid sperm differentiation– Extend from basement membrane to lumen

The Seminiferous Tubules

Figure 28–5a

Figure 28–5b

Testis contains about 1/2 mile of tightly-coiled seminiferous tubules

The Seminiferous Tubules

Figure 28–5c

Spermatogenesis = Sperm formation

• Occurs in seminiferous tubules, aided by sustentacular cells

• Begins with stem cells = spermatogonium– outer most tubule cell, contacts basement

membrane• As cells divide and differentiate they migrate

toward the lumen of tubule

5 Steps in Spermatogenesis 1. Stem cells (spermatogonia) divide by mitosis:

– to produce 2 daughter cells:• 1 remains as spermatogonium• second differentiates into primary spermatocyte

2. Primary spermatocytes:– begin meiosis– form secondary spermatocytes

3. Secondary spermatocytes: – differentiate into spermatids (immature gametes)

4. Spermatids: differentiate into spermatozoa5. Spermatozoa:

– lose contact with wall of seminiferous tubule– enter fluid in lumen

Chromosomes in Mitosis and Meiosis

Figure 28–6

Spermatogenesis

• Involves 3 integrated processes:1. mitosis2. meiosis3. spermiogenesis

1. Mitosis

• Spermatogonium primary spermatocyte• Spermatogonia divide producing daughter cells

– Daughter cell A•Remains at basement membrane as

spermatogonium– Daughter cell B

•Differentiates into a primary spermatocyte and moves toward the lumen

2. Meiosis

• Primary spermatocyte spermatid• The diploid primary spermatocyte

undergoes meiosis I to generate two diploid secondary spermatocytes

• The secondary spermatocytes complete meiosis II producing four spermatids– gametes contain 23 chromosomes

• Fusion of male and female gametes produces:– zygote with 46 chromosomes

3. Spermiogenesis

• Spermatid sperm/spermatozoa• Involves major structural changes• The round spermatids differentiate into small,

streamlined motile cells at the lumen– A long flagellum is formed– The chromosomes are compacted– Excess cytoplasm (cytosol and organelles) is

shed• Complete cellular transformation takes ~5

weeks

Spermatogenesis

Figure 28–7

2n

2n

1n (haploid with duplicated chromosomes,

sister chromatid)

1n (haploid with single chromosomes)

Chromosomes in Spermatogenesis

• Meiosis I and meiosis II:– produce 4 haploid cells, each with 23 chromosomes

• Prophase I:– chromosomes condense – each chromosome has 2 chromatids– Synapsis:

• maternal and paternal chromosomes come together• 4 matched chromatids form tetrad

– Crossing over:• some genetic material is exchanged• increases genetic variation among offspring


• Metaphase I:– tetrads line up along metaphase plate

• Anaphase I:– maternal and paternal chromosomes separate– each daughter cell receives whole chromosome:

• maternal or paternal– Independent assortment:

• as each tetrad splits maternal and paternal components are randomly distributed

• Telophase I ends:– with formation of two daughter cells– with unique combinations of chromosomes

• Both cells contain 23 chromosomes with 2 chromatids each


• Interphase:– separates meiosis I and meiosis II– is very brief– DNA is not replicated

• Meiosis II:– proceeds through prophase II and metaphase II

• Anaphase II:– duplicate chromatids separate

• Telophase II:– yields 4 cells, each containing 23 chromosomes

KEY CONCEPT

• Meiosis produces gametes:– that contain 1/2 of chromosomes in

somatic cells• For each cell entering meiosis:

– testes produce 4 spermatozoa– ovaries produce 1 ovum and 3 polar

bodies

Spermiogenesis and Spermatozoon Structure

Figure 28–8a

Structure of sperm/spermatozoon

1. Head (genetic part)– Flattened nucleus, compact DNA– Covered by acrosome

•Lysosome-like cap containing hydrolytic enzymes for ovum penetration

2. Midpiece (metabolic part)– Contains mitochondria ATP

•To power contractile filaments of flagella3. Tail (locomotor region)

– Flagellum: whip-like motion to propel cell


Figure 28–8b

Spermiogenesis

• Is the last step of spermatogenesis• Each spermatid matures into 1

spermatozoon (sperm):– attached to cytoplasm of

sustentacular cells (sertoli cells)

Sustentacular (sertoli) cells

Figure 28–5b

Role of Sertoli (sustentacular) Cells in Spermatogenesis

1. Maintenance of blood-testis barrier– Cells linked by tight junctions– Regulate environment inside tubule

•High levels of androgens, estrogens, K+, amino acids (testicular fluid)

•Excludes leukocytes2. Support mitosis and meiosis

– Stimulated by FSH and testosterone– Promote cell division

3. Support during spermeogenesis– Hold spermatids and stimulate development

Role of Sertoli (sustentacular) Cells in Spermatogenesis

4. Secrete inhibin– Peptide hormone, inhibits FSH and GnRH

•Negative feedback for spermatogenesis5. Secrete Androgen Binding Protein

– Binds androgens to retain them in tubule to stimulate spermiogenesis

6. Secrete Mullerian Inhibiting Factor– Causes regression of fetal Müllerian ducts

(uterus, uterine tubes)

Fetal Müllerian Ducts

• 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


Figure 28–8a

KEY CONCEPT

• Spermatogenesis:– begins at puberty and continues past

age 70– is a continuous process

• All stages of meiosis are observed within seminiferous tubules

Reproductive Tract

• Spermatogenesis is seminiferous tubule takes 64-72 days

• Immature sperm released into testicular fluid in lumen of tubule

• Moved by fluid pressure and cilia to epididymis

• Includes1. Epididymis2. Ductus deferens3. Urethra

1. The Epididymis

Figure 28–9

Functionally Immature Spermatozoa

• Are incapable of locomotion or fertilization

• Are moved by cilia lining efferent ductules:– into the epididymis

1. Epididymis

• 6 meter coiled tubule around top and side of testis• Functions

1. Monitor and adjust composition of testicular fluid•Stereocilia absorb or secrete

2. Recycle damaged spermatozoa3. Protect, store, facilitate maturation of sperm

•Transit takes ~20 days, sperm mature and gain ability to be motile

•Mature sperm stored few months• During ejaculation, smooth muscle in wall propels sperm to

ductus deferens

2. Ductus deferens

• Passes through inguinal canal (anterior to pubis) as part of the spermatic cord loops over ureter descends posterior to bladder

• Ends in ampulla– Connects to seminal vesicles and prostate

• During ejaculation– peristaltic contractions transmit sperm from storage

in epididymis ejaculatory duct to mix with glandular secretions which activate sperm (now motile)

• Ejaculatory duct connects ampulla to urethra

Spermatozoa Leaving Epididymis

• Are mature, but remain immobile• To become motile (actively swimming) and

functional:– spermatozoa undergo capacitation

1.Spermatozoa become motile:• when mixed with secretions of seminal

vesicles

2.Spermatozoa become capable of fertilization:• when exposed to female reproductive tract

The Ductus Deferens

Figure 28–10a, b

3. Urethra

• Shared by urinary and reproductive systems• 3 regions

1. Prostatic urethra•Connects to urinary bladder and ejaculatory

duct, passes through prostate2. Membranous urethra

•Passes through body wall (urogenital diaphragm)3. Spongy/penile urethra

•Length of penis, opens at external urethral orifica

Accessory Glands

- Produce fluid, nutrients, enzymes, buffers, that comprise bulk of semen

- Semen = sperm + gland secretions- Accessory gland

1. Seminal Vesicles2. Prostate Gland3. Bulbourethral Gland

4 Major Functions of Male Glands

1. Activating spermatozoa2. Providing nutrients spermatozoa need

for motility3. Propelling spermatozoa and fluids along

reproductive tract:– mainly by peristaltic contractions

4. Producing buffers:– to counteract acidity of urethral and

vaginal environments

1. Seminal Vesicle

Figure 28–10a, c

1. Seminal vesicle• On posterior bladder wall• Are extremely active secretory glands • Produce about 60% of semen volume • Produce seminal fluid

1. Fructose: nutrients to drive sperm motility2. Prostaglandins: promote smooth muscle contraction to aid

sperm mobility3. Fibrinogen: converted to fibrin to form clot in vagina4. Vasiculase: enzyme for fibrinogen conversion5. Alkaline buffer: buffer acid pH of vagina

• During ejaculation sperm mixed with seminal fluid in ejaculatory duct become highly motile

2. Prostate Gland

Figure 28–10a, d

2. Prostate Gland

• Encircles prostatic urethra• Forms 20–30% of semen volume• Secretes prostatic fluid into urethra

1. Enzymes to digest cervical mucus2. Fibrinolysin

• breaks down semen clot to release sperm in vagina

3. Seminalplasmin antibiotic

3. Bulbourethral Gland

Figure 28–10a, e

3. Bulbourethral Gland

• In urogenital diaphragm• Secrete alkaline mucus

– Neutralize urinary acids and lubricate glans

• Duct of each gland:– travels alongside penile urethra– empties into urethral lumen

Semen

• 2-5 ml/ejaculation• 60% seminal fluid• 30% prostatic fluid• 10% testicular fluid + active

spermatozoa• 50-300 million sperm/ml

– Less than 60 million total = sterile

External Genitalia

1. Scrotum2. Penis

– Function: deliver sperm to female tract– 3 parts

1. Root: attaches to body wall2. Shaft: tubular, houses erectile tissue3. Glans: distal end, covered by perpuce preputial

glands secrete smegma– Circumcision: remove prepuce

»Prevents UTI’s

The Penis

Figure 28–11b, c

2. The Penis

• Shaft contains 3 columns of erectile tissue

1. (2) corpora cavernosa•Anterior, stiffen shaft

2. (1) corpus spongiosum•Surrounds urethra•Distal end forms glans•Holds urethra open

• Erectile tissue– Vascular channels surrounded by elastic CT and smooth

muscle– Fills with blood via parasympathetic stimulation

2. The Penis

Figure 28–11a, b

Male Sexual Function

1. Erection– Triggered by tactile or mental stimuli– Parasympathetic triggers release of NO– No dilates arterioles blood fills channels– Expansion compresses drainage veins

blood pressure = stiff– Parasympathetic also triggers secretion from

bulbourethral glands– Eventually spinal reflex triggered ejaculation


2. Ejaculation– Spinal reflex sympathetic stimulation– Ducts and glands contract emptying contents to urethra– Skeletal muscles of penis contract, semen propelled out

uretheral oridice

3. Detumescence– Erection subsides

•Sympathetic constricts arterioles– Latent period

•New ejaculation not possible (min-hrs)


• Impotence– Inability to achieve or maintain erection– Due to

•Alcohol, drugs, or hormonal, vascular, or nervous system problems

Hormonal mechanisms regulate

male reproductive functions.

Hormonal and Male Reproductive Function

Figure 28–12

Male Hormones and Repro. Function

1. GnRH is released consistently in 60-90 minutes intervals from the hypothalamus– This triggers release of FSH and LH from the anterior

pituitary2. FSH targets sertoli (sustentacular) cells to

– Promote spermatogenesis– Promote secretion of androgen binding protein– As spermatogenesis increases it triggers release of inhibin

• Inhibin decr. GnRH and FSH by negative feedback3. LH targets interstitial cells

– LH promotes the secretion of androgens (testosterone)

Male Hormones and Repro. Function

4. Testosterone– Stimulates spermatogenesis

• binds to antigen binding protein

– Promotes sex drive in CNS– Stimulates metabolism

• Especially skeletal muscle growth

– Establishes/maintain male secondary sex characteristics– Maintains accessory organs of the reproductive tract– As levels increase, testosterone inhibits GnRH release by negative

feedback• The consistent release of GnRH insures that the circulating levels of

all the hormones (FSH, LH, and testosterone) remain relatively constant

Inhibin, FSH, LH• Elevated FSH levels:

– increase inhibin production– until FSH returns to normal

• If FSH declines:– inhibin production falls– FSH production increases

• LH– Targets interstitial cells of testes– Induces secretion of testosterone

Testosterone and Development• Testosterone production:

– begins around seventh week of fetal development– reaches prenatal peak after 6 months

• Secretion of Müllerian inhibiting factor:– by sertoli (sustentacular) cells– leads to regression of Müllerian ducts

• Early surge in testosterone levels:– stimulates differentiation of male duct system and

accessory organs– affects CNS development

• Testosterone programs hypothalamic centers that control:– GnRH, FSH, and LH secretion, sexual behaviors,

sexual drive

Estradiol

• Is produced in relatively small amounts (2 ng/dl)

• 70% is converted from circulating testosterone:– by enzyme aromatase

• 30% is secreted by interstitial and sustentacular cells of testes

Age Related Changes

1. Male climacteric:– Decrease testosterone = decr. Libido

2. Benign prostatic hypertrophy– Prostate increases, can block urethra

3. Increased impotence4. Sperm motility rate declines

On a warm day, would the cremaster muscle be contracted or relaxed?

A. contracted

B. relaxed

What will happen if the arteries within the penis dilate?

A. impotence

B. becomes flaccid

C. erection

D. erectile disfunction

What effect would low levels of FSH have on sperm production?

A. higher rate of production

B. lower rate of production

C. malformed sperm

D. no effect on sperm production

Female Reproductive System.

The Female Reproductive System

Figure 28–13


• Consists of– Female gonads = ovaries– Accessory reproductive organs = uterine

tubes, uterus, vagina•Aid fertilization and embryo growth

and delivery

Ovary = female gonads

• Produce:– Gametes (ova) and hormones estrogen, progesterone,

inhibin• Lateral to uterus• Surrounded by two layers

– Germinal epithelium•Simple cuboidal epithelium, from peritoneum

– Tunica albuginea•Dense CT capsule

• Cortex– Houses forming gametes in ovarian follicles

Ovary = female gonads

• Stroma interior tissues of ovary include: 1. Cortex

– Houses forming gametes in ovarian follicles:•Oocyte•Surrounding cells

– Single layer = follicle cells– Stratified = granulosa cells

»Endocrine cells that produce female sex hormones 2. Medulla

– Contains blood vessels and nerves

Ovary Support

• Mesovarium • Ovarian ligament:

– extends from uterus to ovary• Suspensory ligament:

– extends from ovary to pelvic wall– Contains major blood vessels of ovary:

•Ovarian artery and ovarian vein– Vessels connect to ovary at ovarian hilum:

where ovary attaches to mesovarium

Oogenesis

Figure 28–15

Oogonia = stem cells of females:complete mitotic divisions before birth

Oogenesis = oocyte formation

• Begins prior to birth and ends at metaphase• During fetal development

– primary oocytes suspended in Meiosis I are formed in primordial follicles

• From puberty to menopause – primary oocytes are activated on a 28 day cycle (the ovarian

cycle) to complete Meiosis I to produce one large secondary oocyte and one small polar body

• At ovulation the secondary oocyte is released from the ovary suspended in Meiosis II

• Secondary oocyte will not complete Meiosis to produce a mature ovum until fertilized by a sperm

Atresia

• Is the degeneration of primordial follicles:

• Ovaries have about 2 million primordial follicles at birth:– each containing a primary oocyte

• By puberty:– number drops to about 400,000

Oogenesis: 2 Characteristics of Meiosis

1. Cytoplasm of primary oocyte divides unevenly:

– producing 1 ovum (with original cytoplasm)

– and 2 or 3 polar bodies (that disintegrate)2. Ovary releases secondary oocyte (not

mature ovum):– suspended in metaphase of meiosis II– meiosis is completed upon fertilization

Ovarian Cycle

The Ovarian Cycle

Figure 28–16 (1 of 2)

The Ovarian Cycle

Figure 28–16 (2 of 2)

Ovarian Cycle

1. Follicular Phase (preovulatory phase)

2. Ovulation3. Luteal Phase (postovulatory

phase)

Ovarian Cycle

1. Follicular Phase– Period of follicle growth (day 1-14)A. Formation of Primary Follicles (day 1-8)

• Squamous follicle cells of many primordial follicles enlarge into cuboidal cells and begin dividing

– forming primary follicles• The follicular cells produce stratified layers

– Now called granulosa cells• Microvilli form the innermost granulosa cells are

connected to the primary oocyte via gap junctions to – support and stimulate the growth of the oocyte

Ovarian Cycle1. Follicular Phase

– Period of follicle growth (day 1-14)A. Formation of Primary Follicles (day 1-8) con’t

• The granulosa cells secrete glycoproteins – form a thick membrane around the primary

oocyte called the zona pellucida• Cells form the ovarian cortex form a layer of thecal

cells around the outside of the primary follicle• Thecal cells and granulosa cells together begin

producing estrogens


– Period of follicle growth (day 1-14)B. Formation of Secondary Follicles (8-10)

• Only a few primary follicles continue development to become secondary follicles

• Granulosa cells begin to secrete follicular fluid• The fluid accumulates between the stratified

layers of the granulosa cells creating a space called the antrum

– This is now called a secondary follicle


– Period of follicle growth (day 1-14)C. Formation of one Tertiary Follicle (10-14)

• The primary oocyte becomes restricted to one side of the follicle attached by a stalk and surrounded by a layer of granulosa cells called the corona radiata

• The antrum continues to expand until the follicle spans the width of the cortex

– This is now called a tertiary follicle

• One tertiary or vasicular follicle usually forms – 99% of the time

• The primary oocyte completes meiosis I forming a secondary oocyte and a small polar body

Ovarian Cycle

2. Ovulation– Day 14– The tertiary follicle ruptures through the ovarian

wall releasing the secondary oocyte – Secondary oocytes is surrounded by the zona

pellucida and corona radiata (granulosa cells associated with secondary oocyte)

Ovarian Cycle3. Luteal Phase

– Day 14-28– The ruptured tertiary follicle collapses and fills with blood– The granulosa cells and thecal cells proliferate and reorganize

into the corpus luteum– The corpus luteum secretes progesterone and some estrogens– If pregnancy does not occur:

• the corpus luteum degenerates and is invaded by fibroblasts• The fibroblasts create scar tissue called the corpus albicans

– If pregnancy occurs:• The corpus luteum remains active for 3+ months until the

placenta takes over progesterone secretion

KEY CONCEPT

• Oogenesis begins during embryonic development• Primary oocyte production is completed before

birth• Each month after puberty:

– ovarian cycle produces at least 1 secondary oocytes

– from existing population of primary oocytes• Number of viable primary oocytes:

– declines over time– until ovarian cycles end (age 45–55)


• Ovaries or female gonads:– release 1 immature gamete (oocyte) per

month– produce hormones

• Uterine tubes: – carry oocytes to uterus

• If sperm reaches oocyte:– fertilization is initiated– oocyte matures into ovum

Uterine Tubes• Function

– Transmit oocyte to uterus– Site for fertilization

• Muscular tube, lined with ciliated columnar epithelium and mucin secreting cells

• Oocyte moved via peristalsis and cilia• Secretions to nourish oocyte (and sperm)• Pelvic Inflammatory Disease

– Infection of uterine tubes • N. gonorrhoeae, Chlamydia

– Scaring can cause infertility

Uterine Tubes• 3 regions

1. Infundibulum• Expanded end, has fimbriae with cilia that sweep ovarian

surface to brush oocyte into uterine tube2. Ampulla

• Muscular length• Fertilization occurs here

3. Isthmus connects to uterus

• Transit ovary to uterus takes 3-4 days• Ectopic pregnancy

– Implantation of zygote in location other than uterus (0.6%), most spontaneously abort

Uterine Tube

Figure 28–14

Also known asFallopian tubes or oviducts

Figure 28–17a, b

The Uterine Tubes

Uterine Tube and Oocyte Transport

• From infundibulum to uterine cavity:– normally takes 3–4 days

The Uterus

Figure 28–18a

Uterus

• Anterior to rectum, posterior and superior to bladder

• Function– House and nourish fertilized ovum

• Two regions1. Body2. Cervix

Uterus

1. Body• Main portion, was has 3 layers

1. Perimetrium = visceral peritoneum2. Myometrium = Middle, thick muscular

• Smooth muscle arranged into longitudinal, circular, and oblique layers

• Provides force to move fetus out of uterus into vagina

3. Endometrium = Inner, glandular mucosa• Simple columnar epithelium over thick lamina propria• Glandular and vascular tissues support physiological demands

of growing fetus• 2 zones

1. Functional zone 2. Basilar zone

Uterus

1. Body– 2 zones

1. Functional zone– Thick, borders uterine cavity, glands, vessels

and epithelium change with hormones through uterine cycle

– Shed in mensus2. Basilar zone

– Thin, borders myometrium, remains constant– Gives rise to new function zone after mensus

The Uterine Wall

Figure 28–19

Uterus2. Cervix

– Inferior, tubular– Connects to vagina through cervical canal at external os

(orifice)– Mucosa has cervical glands

• Secrete thick mucus to block canal to prevent infections– Mucus thins at mid ovarian cycle for sperm entry

• Prolapse of the uterus– Damage to supporting ligaments results in uterus

protruding through vaginal opening

The Uterus

• Provides for developing embryo (weeks 1–8) and fetus (week 9 through delivery):

1. mechanical protection2. nutritional support3. waste removal

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

• Unfertilized oocyte– Degenerate in terminal portions of

uterine tubes or within uterus

The Uterus

Figure 28–18b

As the result of infections such as gonorrhea, scar tissue can block the lumen of each uterine

tube. How would this blockage affect a woman’s ability to conceive?

A. easier to conceive

B. sterility

C. difficulty in conceiving

D. no effect on conception

Which layer of the uterus is sloughed off during menstruation?

A. myometrium

B. basilar zone of the endometrium

C. functional layer of the endometrium

D. perimetrium

Uterine Cycle

Figure 28–20

3 Phases of the Uterine Cycle

1. Menses2. Proliferative phase3. Secretory phase

Uterine Cycle (Menstrual Cycle)

• Corresponds with ovarian cycle • Same hormones regulate both• 1. Mensus (day 1-5)

– Correlates with beginning of follicular phase at ovary– Arteries constrict, tissues and glands of functional

zone deteriorate– Necrotic vessels rupture, blood flushes necrotic

endometrial tissue out of uterus to vagina = menstruation•Menstruation = loss of functional zone of

endometrium

Uterine Cycle (Menstrual Cycle)

• 2. Proliferative phase (day 6-14)– Correlates with follicular enlargement and oocyte maturation– Cells of basilar zone of endometrium multiply to restore the

mucosa, glands, and vessels of the function zone• 3. Secretory phase (day 15-28

– Correlates with ovulation and duration of luteal phase– Endometrial glands enlarge and secrete mucus rich in

glycogen to nourish potential embryo– Secretion peaks 12 days post ovulation then declines as

corpus luteum ceases hormone production– In pregnancy occurs,

• secretion will continue and mensus will be inhibited

Uterine Cycle

• Endometriosis– Endometrial tissue growing outside uterus– Painful mass that cycles– Requires drugs or surgery

• Menarche = first menstrual cycle• Menophase = last menstrual cycle• Amenorrhea

– Failure to initiate mensus– Due to physical exertion and low body mass– Leptin permissive on gonadotropins

What changes would you expect to observe in the ovarian cycle if the LH

surge did not occur?

A. premature ovulation

B. no follicular development

C. oogenesis would not occur

D. ovulation and corpus luteum formation would not occur

What effect would a blockage of progesterone receptors in the uterus

have on the endometrium?

A. inhibit menstruation

B. inhibit glandular secretion

C. inhibit initial thickening of endometrium

D. promote development of endometrial lining

What event occurs in the uterine cycle when the levels of estrogens and

progesterone decline?

A. pregnancy

B. menarche

C. menses

D. menopause

Vagina

Figure 28–21

Vagina

• Functions to receive penis and deliver infants and menstrual flow

• Elastic muscular tube, connect cervix to vestibule (external genitalia)

• 3 wall layers1. Adventitia2. Muscularis3. Mucosa: stratified squamous epithelium

• Folded into rugae when relaxed• Epithelium secretes glycogen

– Resident bacteria metabolize into lactic acid, low pH prevents pathogen colonization

Vaginitis

• Is an inflammation of the vaginal canal

• Is caused by fungi, bacteria, or parasites

A Vaginal Smear

• Is a sample of epithelial cells shed at surface of vagina

• Used to estimate stage in ovarian and uterine cycles

What is the advantage of the acidic pH of the vagina?

A. enhances sperm motility

B. prevents mucus secretions

C. maintains epithelial lining

D. prevents bacterial, fungal, and parasitic infections

The Female External Genitalia

Figure 28–22

External genitalia = Vulva

1. Mons pubis – Anterior vulva, adipose over pubic symphasis

2. Labia majora– Lateral vulva (=male scrotum), surrounds

labia minora3. Labia minora

– Encloses vestibule (=ventral penis)

External genitalia = Vulva

4. Vestibule– Urethral orifice anterior, vaginal orifice

posterior, flanked by greater vestibular glands (=bulbourethral glands) that produce secretions to lubericate vestibule

5. Clitoris– Anterior to vestibule– Erectile tissue (=corpus cavernosa)– Covered by prepuce – formed by anterior labia

The Mammary Glands

Figure 28–23a

Mammary Glands• Lactation - Milk to nourish newborn• Modified sweat glands over pectoralis muscles• Center = areola

– Pigmented skin around nipple• Divided into ~25 lobes around nipple, CT and adipose between

lobes• Lobe contains lobules of alveoli – glandular structures that

produce milk• Lobule empties to lactiferous duct, exits lobe to lactiferous sinus• Sinus stores milk during nursing• Pregnancy causes proliferation of alveolar tissue for milk

production

Circulating Hormones

• Control female reproductive cycle• Coordinate ovulation and uterus

preparation

GnRH

• GnRH from hypothalamus:– regulates reproductive function

• GnRH pulse frequency and amplitude:– change over course of ovarian cycle

• Changes in GnRH pulse frequency:– are controlled by estrogens and progestins

• Estrogens increase pulse frequency• Progestins decrease pulse frequency

Pathways of Steroid Hormone Synthesis in Males and

Females

Figure 28–24

Follicular Development

• Begins with FSH stimulation• Monthly:

– some primordial follicles develop into primary follicles

• As follicles enlarge:– thecal cells produce androstenedione

The Hormonal Regulation of Ovarian Activity

Figure 28–25

Hormones and the Female Reproductive Cycle

• Ovarian and uterine cycles – must be coordinated to allow fertilization and

implantation of an embryo

• GnRH levels changes over the duration of the cycles to alter the levels of FSH and LH– FSH and LH

• Control the secretion of the female sex hormones estrogen and progesterone

• Sex hormone levels drive oocyte maturation and uterus development


1. Follicular Phase– GnRH levels begin to rise triggering release of FSH and LH– FSH and LH stimulate follicle growth and maturation and

production of estrogen• LH targets thecal cells to produce androstenedione• FSH targets granulosa cells to convert androstenedione to

estrogens

– Increasing estrogen levels trigger• Continued oocyte and follicle development• Growth of new functional layer in the uterus• Expression of progesterone receptors on endometrial tissue• Negative feedback inhibition of the release of FSH and LH

– Both are still produced but are stored in the anterior pituitary


1. Follicular Phase– Granulosa cells of secondary follicles secrete inhibin– Inhibin provides further negative feedback on FSH

2. Ovulation– Tertiary follicles are producing peak levels of estrogen

which triggers• A burst of LH to be release (along with some FSH)• Thinning of the cervical mucus

– LH surge triggers• Primary oocyte to complete meiosis I forming the

secondary oocyte• Ovulation: rupture of secondary oocyte through ovary wall• Formation of the corpus luteum form damaged tertiary

follicle


3. Luteal Phase– The corpus luteum secretes progesterone, estrogen,

and inhibin– Increasing levels of progesterone

• trigger glandular secretion in the uterus and thickening of the cervical mucus

– All three luteum hormones (progesterone, estrogen, inhibin) act to provide negative feedback inhibition on• LH, FSH, and GnRH production and release

– As LH levels decline• The corpus luteum beings to degrade forming the

corpus albicans • Luteum hormone secretion ceases


3. Luteal Phase– Declining levels of progesterone and estrogen

trigger the initiation of mensus– Decreased levels of all three luteum hormones no

longer provide negative feedback• GnRH levels increase and a new cycle begins

Hormonal Regulation of the Female Reproductive Cycle

Figure 28–26a, b


Figure 28–26c, d


Figure 28–26e, f

Functions of Estrogen

1. Stimulates bone and muscle growth2. Maintains female secondary sex characteristics:

– body hair distribution– adipose tissue deposits

3. Stimulate sex drive in CNS- Affects central nervous system (CNS) activity (especially in

the hypothalamus, where estrogens increase the sexual drive)

4. Maintains functional accessory reproductive glands and organs

5. Initiates repair and growth of endometrium

Hormones and Body Temperature

• Monthly hormonal fluctuations affect core body temperature:– during luteal phase:

• progesterone dominates

– during follicular phase:• estrogen dominates• basal body temperature decreases about

0.3°C

Basal Body Temperature

• The resting body temperature• Measured upon awakening in

morning

Body Temperature and Ovulation

• Upon ovulation:– basal body temperature declines

noticeably

• Day after ovulation:– temperature rises

KEY CONCEPT• Cyclic changes in FSH and LH levels maintain

ovarian cycle• Hormones produced by ovaries regulate uterine

cycle• Chance of pregnancy is reduced or eliminated by:

– inadequate hormone levels– inappropriate or inadequate responses to

circulating hormones– poor coordination and timing of hormone

production or secondary oocyte release

Aging and the Reproductive System

1. Menophase– Menstruation and ovulation cease due to

lack of perimordial follicles2. Estrogen and progesterone levels decline3. GnRH, FSH, LH increase4. Resulting hormone levels result in

– Reduction of uterus and breast (glands)– Osteopenia or osteoporosis– Cardiovascular disorders

Why does the level of FSH rise and remain high during menopause?

A. Because estrogen declines.

B. Because the ovaries no longer respond to FSH.

C. Because LH levels increase.

D. Because GnRH levels increase.

Menopause

• Is the time that ovulation and menstruation cease

• Typically occurs around age 45–55

Premature Menopause

• Is depletion of follicles before age 40

Andropause

• Also called male climacteric • Is the period of declining

reproductive function • Circulating testosterone begins to

decline:– between ages 50 and 60

• Circulating FSH and LH increase

KEY CONCEPT

• Sex hormones have widespread effects on:– brain development and behavioral drives– muscle mass– bone mass and density– body proportions– patterns of hair and fat distribution

• As aging occurs, reductions in sex hormone levels affect:– appearance– strength– many physiological functions

Hormones of the Reproductive Tract

Table 28–1 (1 of 2)

Hormones of the Reproductive Tract

Table 28–1 (2 of 2)

SUMMARY• Gametes• Fertilization• Gonads:

– Testes and ovaries• External genitalia• Spermatozoa• Semen• Oocytes• Ova• Spermatogenesis• Spermatozoon• Oogenesis

SUMMARY

• Uterine tubes• Uterus• Uterine cycle• Vagina• Mammary glands• Hormones• Male sexual function• Female sexual function• Menopause• Male climacteric

chapter 28: the reproductive system primary sources for figures and content: marieb, e. n. human...

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