Chapter 22 Reproductive Systems

Male reproductive organs

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Male Reproductive Organs

posterior view

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Male Reproductive Organs

• Specialized to produce, maintain the male sex cells (sperm)

• Transport these cells together with supporting fluids to the female reproductive tract

• Secrete male sex hormones 3

1 Testes

• Ovoid structure about 5 cm long and 3 cm in diameter

• Suspended by spermatic cord

• Contained within the cavity of the scrotum

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Descent of the Testes

During fetal development, each testis develops near a kidney and then descends through an inguinal canal and enters the scrotum completing the journey by the eighth gestational month.

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Structure of the Testes

Tunica albuginea

Mediastium testes -septa -lobules

Seminiferous Tubules

Epididymis

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2 Formation of Sperm Cells

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Spermatogenesis

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Crossing Over

• mixes up genetic traits • different colors represent the fact that one homologous chromosome comes from the individual’s father and one from the mother

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3 Crossing Over

• the genetic information in sperm cells and egg cells varies from cell to cell

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Blood-testis barrier

• Prevents some substances from reaching the developing sperm

• Helps maintain favorable environment by isolating sperm from the man’s immune system

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Structure of a Sperm Cell

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4 Male Internal Accessory Organs

• epididymus • ductus deferens • seminal vesicles • prostate gland • bulbourethral glands

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Epididymus

• tightly coiled tubes • connected to ducts within testis • Support stored sperm • promote maturation of sperm cells

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Ductus Deferens

• muscular tubes • about 45 cm each • extends from epididymis to ejaculatory duct • Ampulla-expanded part of ductus deferens near the end • Passes through prostate into urethra 15

5 Seminal Vesicles

• attached to ductus deferens near base of bladder • secrete alkaline fluid • secrete fructose and prostaglandins • contents empty into ejaculatory duct

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Prostate Gland

• surrounds proximal portion of urethra • ducts of gland open into urethra • secretes a thin, milky, alkaline fluid • secretion enhances fluid mobility • composed of tubular glands in connective tissue • also contains smooth

muscle 17

Bulbourethral Glands

• inferior to the prostate gland • secrete mucus- like fluid • fluid released in response to sexual stimulation

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6 Semen

• sperm cells • secretions of seminal vesicles, prostate gland, and bulbourethral glands • slightly alkaline • prostaglandins • nutrients • 120 million sperm cells per milliliter 19

Male External Reproductive Organs

• scrotum • penis

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Scrotum

• pouch of skin and subcutaneous tissue • dartos muscle – smooth muscle in subcutaneous tissue; contracts to cause wrinkling of the scrotum • medial septum divides scrotum into two chambers • each chamber lines with a serous membrane • each chamber houses a testis and epididymis

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7 Penis

• conveys urine and semen • specialized to become erect for insertion into the vagina • circumcision

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Penis

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Erection, Orgasm, and Ejaculation

Erection • parasympathetic nerve impulses • blood accumulates in erectile tissues

Orgasm • culmination of sexual stimulation • accompanied by emission and ejaculation

Ejaculation • emission is the movement of semen into urethra • ejaculation is the movement of semen out of the urethra • largely dependent on sympathetic nerve impulses 24

8 Hormonal Control of Male Reproductive Functions

• hypothalamus controls maturation of sperm cells and development of male secondary sex characteristics

• negative feedback among the hypothalamus, the anterior lobe of the pituitary gland, and the testes controls the concentration of testosterone 25

Actions of Testosterone

• In fetus, stimulates formation of male reproductive organs and causes testes to descend

• increased growth of body hair • sometimes decreased growth of scalp hair • enlargement of larynx and thickening of vocal cord • thickening of skin • increased muscular growth • thickening and strengthening of the bones • increases rate of cellular metabolism and production of rbc’s • male sex drive 26

Organs of the Female Reproductive System

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9 Organs of the Female Reproductive System • Specialized to produce and maintain female sex cells (egg cells or oocytes) • Transport sex cells to the site of fertilization • Provides a favorable environment for a developing offspring • Move the offspring to the outside • Produce female sex hormone

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Ovaries

• Solid, ovoid structures 3.5 cm long, 2 cm wide and 1 cm thick

• Held in place by several ligaments • Broad ligament-largest • Also attahed to uterus and uterine tube • Suspensory ligament-upper end • Ovarian ligament-attaches ovaries to uters

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Ovary Structure

• Medulla-outer part

• Cotex-inner part • Ovarian follicles

• Tunica albuginea

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10 Primordial Follicles

• Start meiosis before birth then stop until puberty

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Oogenesis

• the process of egg cell formation

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Follicle Maturation

Primordial follicle Mature (Graafian) follicle

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11 Follicle Maturation

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Ovulation

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Ovulation

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12 Female Internal Accessory Organs

• uterine tubes • uterus • vagina

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Uterine Tubes

• convey eggs toward the uterus

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Uterus

• hollow muscular organ that receives the embryo that has been fertilized in the uterine tube

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13 Uterine Wall

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Vagina

• fibromuscular tube that conveys uterine secretions, receives the penis during intercourse, and provides an open channel for offspring • hymen

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Female External Reproductive Organs

• labia majora • labia minora • clitoris • vestibule • vestibular glands

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14 Labia Majora

• rounded folds of adipose tissue and skin • enclose and protect the other external reproductive parts • ends form a rounded elevation over the symphysis pubis

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Labia Minora

• flattened, longitudinal folds between the labia majora

• well supplied with blood vessels

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Clitoris

• small projection at the anterior end of the vulva • analogous to the male penis • composed of two columns of erectile tissue • root is attached to the sides of the pubic arch 45

15 Vestibule

• space between the labia minora that encloses the vaginal and urethral openings • vestibular glands secrete mucus into the vestibule during sexual stimulation

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Hormonal Control of Female Reproductive Functions

• estrogens inhibit LH and FSH during most of the reproductive cycle

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Effects of Estrogens

• Stimulates enlargement of accessory organs • Stimulates the endometrium to thicken • Development and maintenance of female sexual characteristics • development of breasts and ductile system of the mammary glands • increased adipose tissue in breasts, thighs, and buttocks • increases vascularization of skin 48

16 Female Reproductive Cycle

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Female Reproductive Cycle

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Menopause

• usually occurs in late 40s or early 50s • reproductive cycles stop • ovaries no longer produce as much estrogens and progesterone • some female secondary sex characteristics may disappear • may produce hot flashes and fatigue • May lead to osteoporosis • May cause migranes, backaches

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17 Mammary Glands

• specialized to secrete milk following pregnancy • composed of lobes • lobes contain alveolar glands drained by alveolar ducts which drain into alveolar ducts which drain into lactiferous ducts that leads to the nipple • estrogens stimulate breast development in females

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Sexually Transmitted Diseases

• silent infections • most are bacterial and can be cured • herpes, warts, and AIDS are viral and cannot be cured • many cause infertility • AIDS causes death • symptoms of STDs include • burning sensation during urination • pain in lower abdomen • fever or swollen glands • discharge from vagina or penis • pain, itch, or inflammation in genital or anal area • sores, blisters, bumps or rashes • itchy runny eyes 53

Clinical Application

Prostate Enlargement

• benign prostatic hypertrophy occurs in most men over 50

• BPH causes frequent urination

• risk factors include a fatty diet, having had a vasectomy, exposure to certain environmental factors, and inheriting a a particular gene that also causes breast cancer

• treatments include surgical removal, drugs, insertion of balloon into urethra, freezing of tumor, or insertion of a stent between lobes of prostate to relieve pressure on urethra

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18 Clinical Application

• Male infertility • Prostate cancer • Testicular cancer

• Female infertility • Cervical cancer • Breast cancer

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