1	Human Anatomy, First Edition McKinley & O'Loughlin Chapter 28 Lecture Outline: The Reproductive System
2	Reproductive Systems Ensure the sexual maturation of each individual. Produce the gametes. Male and female structures are derived from common developmental tissues and serve a common function in adults (homologues).
3	Comparison of the Female and Male Reproductive Systems Primary sex organs called gonads. ovaries in females and testes in males Produce gametes which unite to form a new individual. oocytes sperm Gonads produce large amounts of sex hormones which affect maturation, development, and changes in the activity of the reproductive system organs. estrogen and progesterone in the female androgens in the male
4	Comparison of the Female and Male Reproductive Systems Both have accessory reproductive organs, including duct systems to carry gametes away from the gonads toward the site of fertilization (in females) or simply to the outside of the body (in males). Fertilization occurs when male and female gametes meet. copulation, coitus, sexual intercourse
5	Comparison of the Female and Male Reproductive Systems Primarily nonfunctional and “dormant” until puberty. At puberty, external sex characteristics become more prominent. breast enlargement in females pubic hair in both sexes reproductive organs become fully functional gametes mature gonads secrete sex hormones Both reproductive systems produce gametes. Female typically produces and releases a single oocyte monthly. Male produces 100,000,000’s of (sperm) daily. male gametes are stored for a short time if they are not expelled from the body within that period, they are resorbed
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7	Perineum Diamond-shaped area between the thighs that is circumscribed anteriorly by the pubic symphysis, laterally by the ischial tuberosities, and posteriorly by the coccyx. 2 distinct triangle bases are formed by an imaginary horizontal line extending between the ischial tuberosities of the ossa coxae. Anterior triangle, called the urogenital triangle, contains the urethral and vaginal orifices in females and the base of the penis and the scrotum in males. Posterior triangle, called the anal triangle, is the location of the anus in both sexes.
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9	Anatomy of the Female Reproductive System Peritoneum folds around the various pelvic organs and creates two major dead-end recesses, or pouches. anterior vesicouterine pouch forms the space between the uterus and the urinary bladder posterior rectouterine pouch forms the space between the uterus anteriorly and the rectum posteriorly Primary sex organs of the female are the ovaries. Accessory sex organs include the uterine tubes, uterus, vagina, clitoris, and mammary glands.
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15	Ovarian Follicles Within the cortex are thousands of ovarian follicles. Consist of a type of oocyte surrounded by follicle cells (or granulosa cells), which are nurse cells that support the oocyte. Several different kinds of ovarian follicles, each representing a different stage of development. Oogenesis is the maturation of a primary oocyte to a secondary oocyte.
16	Before Birth The process of oogenesis occurs in a female fetus before birth. At this time, the ovary contains primordial germ cells called oogonia, which are diploid cells, meaning they have 23 pairs of chromosomes. During the fetal period, the oogonia start the process of meiosis, but they are stopped at prophase I. At this point, the cells are called primary oocytes. At birth, the ovary of a female child is estimated to contain approximately 1.5 to 2 million primordial follicles within its cortex. The primary oocytes in the primordial follicles remain arrested in prophase I until after puberty.
17	From Puberty to Menopause During childhood ovaries are inactive, and no follicles develop. Atresia occurs, in which some primordial follicles regress or break down. By the time she reaches puberty only about 400,000 primordial follicles remain. At puberty, the hypothalamus releases GnRH (gonadotropin-releasing hormone), which stimulates the anterior pituitary to release FSH (follicle-stimulating hormone) and LH (luteinizing hormone). The levels of FSH and LH vary in a cyclical pattern and produce a monthly ovarian cycle. The three phases of the ovarian cycle: are the follicular phase, ovulation, and the luteal phase.
18	The Three Phases of the Ovarian Cycle Follicular phase occupies days 1–13 of an approximate 28-day ovarian cycle. Ovulation occurs on day 14 of a 28-day ovarian cycle and is defined as the release of the secondary oocyte from a vesicular follicle. only one ovary ovulates each month Luteal phase occurs during days 15–28 when the remaining follicle cells in the ruptured vesicular follicle turn into a corpus luteum. secretes progesterone and estrogen that stabilize and build up the uterine lining, and prepare for possible implantation of a fertilized oocyte has a life span of about 10–13 days if the secondary oocyte is not fertilized it regresses and becomes a corpus albicans the uterine lining to be shed as menstruation menarche
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20	After Menopause The time when a woman is nearing menopause is called perimenopause. estrogen levels begin to drop, and a woman may experience irregular periods, skip some periods, or have very light periods When a woman has stopped having monthly menstrual cycles for 1 year and is not pregnant, she is said to be in menopause. The age at onset typically is between 45 and 55 years follicles stop maturing, and significant amounts of estrogen and progesterone are no longer being secreted a woman’s endometrial lining does not grow, and she no longer has a menstrual period
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24	Uterine Tubes The uterine tubes, also called the fallopian tubes or oviducts, extend laterally from both sides of the uterus toward the ovaries. In these tubes, the secondary oocyte is fertilized, and the pre-embryo begins to develop as it travels toward the uterus. Usually it takes the pre-embryo about 5 to 6 days to reach the lumen of the uterus.
25	The Uterus Serves Four Functions Site for implantation. pre-embryo implants into the inner uterine wall and becomes connected to the uterine lining Supports, protects, and nourishes the developing embryo/fetus forms a vascular connection with the mother’s uterine wall that later develops into the placenta Ejects the fetus at birth after maternal oxytocin levels increase to initiate the uterine contractions of labor. Site for menstruation. if an oocyte is not fertilized or after a baby is expelled, the muscular wall of the uterus contracts and sheds its inner lining as menstruation
26	Wall of the Uterus Composed of three concentric tunics: Perimetrium Myometrium Endometrium The outer tunic of most of the uterus is a serosa called the perimetrium. continuous with the broad ligament The myometrium is the thick, middle tunic of the uterine wall formed from three intertwining layers of smooth muscle. in the nonpregnant uterus, the muscle cells are less than 0.25 millimeters in length during the course of a pregnancy, smooth muscle cells increase both in size and in number
27	Uterine (Menstrual) Cycle and Menstruation The menstrual phase occurs approximately during days 1–5 of the cycle. This phase is marked by sloughing of the functional layer and lasts through the period of menstrual bleeding. The proliferative phase follows, spanning approximately days 6–14. The initial development of the functional layer of the endometrium overlaps the time of follicle growth and estrogen secretion. The last phase is the secretory phase, which occurs at approximately days 15–28. During the secretary phase, increased progesterone secretion from the corpus luteum results in increased vascularization and development of uterine glands. If the oocyte is not fertilized, the corpus luteum degenerates, and the progesterone level drops dramatically. Without progesterone, the functional layer lining sloughs off, and the next menstrual phase begins.
28	Vagina The vagina is a thick-walled, fibromuscular tube that forms the inferior-most region of the female reproductive tract and measures about 10 centimeters in length in an adult female. The vagina connects the uterus with the outside of the body anteroventrally, and thus functions as the birth canal. The vagina is also the copulatory organ of the female, as it receives the penis during intercourse, and it serves as the passageway for menstruation. The vaginal wall is heavily invested with both blood vessels and lymphatic vessels. The vagina’s relatively thin, distensible wall consists of three tunics: an inner mucosa, a middle muscularis, and an outer adventitia
29	External Genitalia The external sex organs of the female, are collectively called the vulva. The mons pubis is an expanse of skin and subcutaneous connective tissue immediately anterior to the pubic symphysis. covered with pubic hair in postpubescent females labia majora labia minora clitoris located at the anterior regions of the labia minora glans prepuceis−an external fold of the labia minora that forms a hoodlike covering over the clitoris.
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31	Mammary Glands Each mammary gland, or breast, is located within the anterior thoracic wall and is composed of a compound tubuloalveolar exocrine gland. Breast milk contains proteins, fats, and a sugar to provide nutrition to infants. The nipple is a cylindrical projection on the center of the breast. It contains multiple tiny openings of the excretory ducts that produce breast milk. The areola is the pigmented rosy or brownish ring of skin around the nipple. Its surface often appears uneven and grainy due to the numerous sebaceous glands immediately internal to the surface. The color of the areola may vary, depending upon whether or not a woman has given birth. In a nulliparous woman (a woman who has never given birth), the areola is rosy or light brown in color. In a parous woman (a woman who has given birth), the areola may change to a darker rose or brown color.
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34	Anatomy of the Male Reproductive System Primary gonads are the testes Accessory sex organs include: a complex set of ducts and tubules leading from the testes to the penis a group of male accessory glands the penis, which is the organ of copulation
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36	Scrotum Male gametes often exhibit abnormal or completely curtailed development when exposed to elevated temperatures. Consequently, both the male gonads and the first portion of the duct system, which is the site of early sperm maturation and development, reside outside the body proper within a skin-covered sac called the scrotum. When the testes are exposed to elevated temperatures, the skin of the scrotal sac becomes thin as a result of dartos relaxation. At the same time, another muscle (the cremaster muscle) relaxes to allow the testes to move inferiorly away from the body. The testes temperature becomes less than normal body temperature. The opposite occurs if the testes are exposed to cold.
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39	Testes The spaces surrounding the seminiferous tubules are called interstitial spaces. Within these spaces reside the interstitial (Leydig) cells, which produce hormones called androgens. There are several types of androgens, the most common one being testosterone. Although the adrenal cortex secretes a small amount of androgens, the vast majority of androgen release is via these interstitial cells in the testis, beginning at puberty. These hormones cause males to develop the classic characteristics of axillary and pubic hair, deeper voice, and sperm production.
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42	Spermatic Cord The blood vessels and nerves to the testis travel from within the abdomen to the scrotum in a multilayered structure called the spermatic cord.
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45	Epididymis The epididymis is a comma-shaped structure composed of an internal duct and an external covering of connective tissue. Its head lies on the superior surface of the testis, while the body and tail are posterior to the testis. Internally, the epididymis contains a long, convoluted duct of the epididymis, which is approximately 4 to 5 meters in length. Sperm must reside in the epididymis for a period of time to become mature and fully motile. If they are expelled too soon, they lack the motility necessary to travel through the female reproductive tract and fertilize an oocyte. If sperm are not ejected from the male reproductive system in a timely manner, the old sperm degenerate in the epididymis.
46	Ductus Deferens When sperm leave the epididymis, they enter the ductus deferens, also called the vas deferens. The ductus deferens is a thick-walled tube that travels within the spermatic cord, through the inguinal canal, and within the pelvic cavity before it reaches the prostate gland. The ampulla of the ductus deferens unites with the proximal region of the seminal vesicle to form the terminal portion of the reproductive duct system, called the ejaculatory duct.
47	Urethra Transports semen from the ejaculatory duct to the outside of the body. Subdivided into: prostatic urethra that extends through the prostate gland membranous urethra that travels through the urogenital diaphragm penile urethra that ends through the penis Sperm leave the body through the urethra.
48	Accessory Glands The vagina has a highly acidic environment to prevent bacterial growth. Sperm cannot survive in this type of environment, so an alkaline secretion called seminal fluid is needed to lessen the acidity of the vagina and bring pH values closer to neutral. As the sperm travel through the reproductive tract (a process that can take several days), they are nourished by nutrients within the seminal fluid. The components of seminal fluid are produced by accessory glands: seminal vesicles prostate gland bulbourethral glands
49	Seminal Vesicles The paired seminal vesicles are located on the posterior surface of the urinary bladder adjacent to the ampulla of the ductus deferens. Each seminal vesicle is an elongated, pouchlike hollow organ approximately 5–8 centimeters long. It is the proximal portion of each seminal vesicle that merges with a ductus deferens to form the ejaculatory duct. The seminal vesicles secrete a viscous, whitish-yellow alkaline fluid containing both fructose and prostaglandins. The fructose is a sugar that nourishes the sperm as they travel through the female reproductive tract, while the prostaglandins promote the widening and slight dilation of the external os of the cervix.
50	Prostate Gland A compact encapsulated organ that weighs about 20 grams and is shaped like a walnut, measuring approximately 2 cm by 3 cm by 4 cm. Located immediately inferior to the bladder. Secretes a slightly milky fluid that is weakly acidic and rich in citric acid, seminalplasmin, and prostate-specific antigen (PSA). citric acid is a nutrient for sperm health seminalplasmin is an antibiotic that combats urinary tract infections PSA acts as an enzyme to help liquefy semen following ejaculation
51	Bulbourethral Glands Paired, pea-shaped bulbourethral glands (or Cowper’s glands) are located within the urogenital diaphragm on each side of the membranous urethra. Each gland has a short duct that projects into the base of the penis and enters the spongy urethra. Their secretory product is a clear, viscous mucin that forms mucus when mixed with water. As a component of the seminal fluid, this mucin protects the urethra and serves as a lubricant during sexual intercourse.
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55	Semen Seminal fluid from the accessory glands combines with sperm from the testes to make up semen. When released during intercourse, semen is called the ejaculate, and it is normally about 3 to 5 milliliters in volume and contains approximately 200 to 500 million spermatozoa. In a sexually active male, the average transit time of human spermatozoa—from their release into the lumen of the seminiferous tubules, passage through the duct system, and appearance in the ejaculate—is about 2 weeks. Since semen is composed primarily of seminal fluid, a male who is very active sexually may have a reduced sperm count because there are fewer sperm to be released from the epididymis; however, the total semen volume remains close to normal for that individual.
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58	Aging and the Reproductive Systems Our reproductive systems are basically nonfunctional for several years following birth. When we reach puberty, hormonal changes in the hypothalamus and anterior pituitary gland stimulate the gonads to begin producing sex hormones. Thereafter, changes occur in many body structures, the reproductive organs mature, and gonads begin to produce gametes. Gametes stop maturing in females in their 40s or 50s, and menopause occurs. A reduction in hormone production that accompanies menopause causes some atrophy of the reproductive organs and the breasts. The vaginal wall thickness decreases, as do glandular secretions for maintaining a lubricated and moist lining. The uterus shrinks and atrophies, becoming much smaller than it was before puberty.
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