The Reproductive System

Chapter 16

The Reproductive System

• Gonads- Primary Sex Organs–Males - Testes–Females - Ovaries–Produce sex cells “gametes”•Males – sperm• Females – eggs

–Secrete sex hormones2

Male Reproductive System• Testes

• Duct System– Epididymis– Ductus Deferens– Urethra

• Accessory Glands and Semen– Seminal vesicles– Prostate gland– Bulbourethral Glands– Semen

• External Genitalia– Scrotum– Penis

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Male Reproductive System

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Testes

• Coverings of Testes– Tunica albuginea• White coat

surrounding each testes

– Septa• Divides testes

into a large number of lobules

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Testes

• Each lobule contains one of four tightly coiled seminiferous tubules–“sperm-forming factories”–Empty sperm into rete testis

• Sperm travels through rete testis to epididymis• Intersitial cells produce horomones–More specifically testosterone

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Epididymis

• Comma shaped highly coiled tube• Provides storage site for

immature sperm that enter testis• Sperm mature while in epididymis

over 20 days• When sexually stimulated- walls

contract to expel sperm to ductus deferens

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Ductus Deferens (vas deferens)

• Propels live sperm from epididymis to urethra by perisalisis• End of ductus deferens empties

into ejaculatory duct• Spermatic cord- ductus deferense,

blood vessels and nerves• Vasectomy – cutting of ductus

deferense – leads to sterility but no loss in sex drive

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Urethra• Extends from base of urinary

blader to tip of penis• 3 regions–Prostatic urethra – surrounded by

prostate gland–Membranous urethra – distance from

prostatic urethra to penis–Spongy (penile) urethra – runs

within length of penis• Carries both urine and sperm–Never pass at the same time

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Seminal Vesicles

• At base of bladder• Produce about 60% of fluid

volume of semen• Thick yellowish secretion rich

in sugar, vitamin C, prostaglandins and other substances–Nourish and activate the sperm

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Prostate Gland

• Encircles upper part of urethra• Secrets milky fluid that

activates sperm• Enters urethra through

several small ducts

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Bulbourethral Glands

• Produce thick, clear mucus that drains into penile urethra• First secretion to pass when

man become sexually excited–Cleans out traces of acidic urine–Serves as lubricant for sexual intercourse

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Semen

• Milky white, somewhat sticky mixture of sperm and gland secretions• Provides transport, nutrients,

and chemicals that protect sperm and aid in movement

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External Genitalia• Scrotum– Sac of skin hanging outside abdominal

cavity– Provides temperature about 30 C lower

than body temp for healthy sperm• Penis– Delivers sperm to female reproductive

tract– Regions of the penis• Shaft• Glans penis – enlarged tip• Prepuce or foreskin – cuff of skin

– Can be removed in circumcision

• Erection – spongy urethra that fills with blood during sexual excitement 14

Spermatogenesis

• Production of sperm• Starts during puberty and

continues throughout life• Every day man makes millions

of sperm• Sperm formation takes place in

seminiferous tubules of testis

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Spermatogenesis• Spermatogonia–Rapid mitoic

divison to build up stem cell line

• Follicle-stimulating hormone modifies division–Division produces

two types of cells• One stem cell• Primary

spermatocyte 16

Spermatogenesis• Primary

spermatocytes undergo meiosis• Produce four

sperm – spermatids

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Spermatogenesis• Spermiogenesis–Maturing of

spermatids into sperm cells–3 regions of

mature sperm• Head – contains

DNA• Midpiece • Tail

• Entire process takes 64-72 days 18

Anatomy of a Mature Sperm

• DNA is found in head• Only

flagellated cell in human body

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Threats to Sperm Formation

• Penicillin• Tetracycline• Radiation• Lead• Certain pesticides• Marijuana• Tobacco• Excessive alcohol

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Testosterone Production• Produced in testes in intersitial

cells• Stimulates reproductive organ

development• Underlies sex drive• Causes secondary male sex

characteristics–Deepening of voice– Increased hair growth–Enlargement of skeletal muscles– Increased heaviness of skeleton 21

• 21 slides• 6 picture only slides• 2 picture and word slides• 13 word slides

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Female Reproductive System

• Ovaries• Duct System–Uterine tubes (fallopian tubes)–Uterus–Vagina

• External Genitalia

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Female Reproductive System

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Ovaries• Primary

reproductive organ• Ovarian

follicles–Sac like structures–Oocyte–Follicle cells

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Ovarian Follicle Stage• Primary follicle- contains

immature oocyte• Graafian follicle- enlargement of

follicle and maturation of oocyte• Ovulation- rupturing of follicle

and ejection of developed egg–Occurs about every 28 days

• Corpus luteum- transformed ruptured follicle

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Support for Ovaries

• Suspensory ligaments – secure ovaries to lateral walls of pelvis• Ovarian ligaments – anchor

ovaries to uterus• Broad ligaments – enclose and

hold ovaries in place by a fold of peritoneum

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Support for the Ovaries

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Uterine Fallopian Tubes

• Initial part of duct system• Provide site where fertilization can

occur• Does not connect to uterine tubes and

ovaries• End of tube has fimbriae – fingerlike

projections• Held in place by broad ligament• Move oocyte toward uterus (3-4 days)

by peristalsis and rythmic beating of cilia

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Uterus• Located between urinary

bladder and rectum• Receives, retains and nourishes

a fertilized egg• Size and shape of pear in

unpregnant woman• Suspended in pelvis by broad

ligament and anchored by round and uterosacral ligaments

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Support for the Uterus

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Regions of the Uterus

• Body – main portion• Fundus – round region above

entrance of uterine tubes• Cervix – narrow outlet

protruding into vagina

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Walls of the Uterus• Endometrium– Inner layer–Where fertilized egg resides during

development–Sloughs off about every28 days

(menses) if not pregnant• Myometrium – middle layer of

smooth muscle–Active role during delivery

• Visceral peritoneum – outermoust serous layer

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Vagina• Thin-walled tube• Extends from cervix to body

exterior• Also known as birth canal• Receives penis and semen

during sexual intercourse• Hymen is distal end of vagina

and usually ruptures during first sexual intercourse 34

External Genitalia• Mons pubis

– Fatty, rounded area over pubic area

– Usually covered with pubic hair

• Labia – skin folds– Labia majora– Labia minora

• Vestibule– Contains external

opening of urethra– Greater vestibular

glands- provide lubrication during intercourse

• Clitoris – Composed of erectile

tissue similar to penis 35

Oogenesis

• Total supply of eggs is determined by birth• Reproductive ability begins at

puberty and ends around 50s (menopause)• Similar to formation of sperm

in male testes

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Oogenesis• Oogonia – female stem cells found in

a developing fetus• Mitosis occurs to produce primary

oocytes• Primary oocytes surrounded by single

layer of cells to form primary follicles• Oogonia does not exist after birth• Primary oocytes inactive until puberty

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Oogenesis

• Follicle-stimulating hormone released during puberty causing some primary follicles to mature–Meiosis starts inside maturing

follicle• Produces seconday oocyte and first polar body is formed

–Meiosis finishes only if sperm penetrates and fertilization occurs• Two more polar bodies are formed

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Menstrual Cycle• Cyclic changes of endometrium• Controlled by cyclic production of

estrogen and progesterone by ovaries• Stages of the menstrual cycle–Menses• Day 1-5: functional layer of endometrium

is sloughed off• Accompanied by 3 – 5 days of bleeding

– Proliferative stage• Day 6 – 14: regeneration of endometrium

layer– Secretory stage• Day 15 – 28: endometrium increases in

size and becomes ready for implantation 40

Hormone Control of Ovarian and Uterine Cycles

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Hormone Control of Ovarian and Uterine Cycles

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Hormone Production of the Ovaries

• Estrogens– Produced by follicle cells– Causes appearance of secondary

characteristics• Enlargement of accessory organs• Development of breasts• Appearance of pubic and axillary hair• Increased deposits of fats in hips and breasts• Widening and lightening of pelvis• Onset of menses (menstrual cycle)

• Progesterone – Produced by corpus luteum– Produced as long as LH is present– Helps maintain pregnancy 43

Mammary Glands

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Male Reproductive System

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