Chapter 16 Reproductive System

Chapter 16 Reproductive System
Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

Pretest True or False The gonads include egg and sperm cells.
The head of a sperm contains 46 chromosomes. Sperm are propelled through the ductus deferens by peristalsis. The prostate gland encircles the urethra. The scrotum is a pouch of skin and subcutaneous tissue that contains the testes. Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

Pretest, cont. True or False
The process of egg formation is known as oogenesis. Fertilization usually takes place in the uterus. The bulk of the uterine wall is made up of the myometrium. The endometrium is shed from the uterine wall during the secretory phase of the uterine cycle. The cessation of the female reproductive cycle is known as menarche. Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

Introduction to the Reproductive System
Functions: Produce egg and sperm cells Transport and sustain egg and sperm cells Nurture developing offspring Produce hormones Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

Introduction to the Reproductive System, cont.
2. Gonads: primary reproductive organs Include ovaries and testes Produce egg and sperm cells (gametes) Produce hormones Regulate normal physiology of reproductive system 3. Secondary (or accessory) reproductive organs Include all other organs, ducts, and glands in the reproductive system Functions: Transport and sustain gametes Nurture the developing offspring (in the female) Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

Male Reproductive System
Functions: Produces, sustains, and transports sperm Introduces sperm into the female vagina Produces hormones Testes (testicles) Primary reproductive organs in the male Begin development high in abdominal cavity Last 2 months before birth (or shortly after birth) Testes descend into scrotum Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

Male Reproductive System, cont.
3. Scrotum: pouch of skin and subcutaneous tissue Extends below abdomen and behind penis Contains the testes Vertical septum of subcutaneous tissue Divides into two parts Each contains one testis Testes: located outside the abdominal cavity Provides a temperature about 3°C below normal body temperature Necessary for the production of viable sperm Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

Structure 1. Tunica albuginea White fibrous connective tissue capsule Surrounds each testis 2. Septa: partitions each testis into lobules 250 lobules in each testis Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

3. Seminiferous tubules: tightly coiled tubules located in the lobules Converge to form a single straight tubule Leads into the rete testis 4. Rete testis: network of tubules on one side of the testis Short efferent ducts exit the testes 6. Interstitial cells (cells of Leydig): cells located between seminiferous tubules Produce male sex hormones Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

Spermatogenesis: Process of Sperm Formation 1. Seminiferous tubules: tightly coiled tubules in which sperm are produced Packed with cells in various stages of spermatogenesis b. Supporting cells (Sertoli cells): interspersed with these cells Provide support and nourishment for gamete-producing cells Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

3. Spermatogonia: immature cells that remain dormant until puberty Located around periphery of seminiferous tubules Diploid cells: contain 46 chromosomes (23 pairs) At puberty: Hormones stimulate cells to begin dividing by mitosis Produce daughter cells Some remain at the periphery as spermatogonia Others are pushed toward lumen Undergo changes: become primary spermatocytes (46 chromosomes) Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

4. Meiosis I a. Primary spermatocyte Undergoes first meiotic division Produces two secondary spermatocytes Contains 23 chromosomes (haploid) Just before this division: Genetic material is replicated Each chromosome: consists of two chromatids joined by a centromere One chromosome (consisting of two chromatids): goes to each secondary spermatocyte Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

5. Meiosis II Each secondary spermatocyte: Divides to produce two spermatids (4 total) Centromere divides Single-stranded chromatid goes to each spermatid Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

Each stage in spermatogenesis: pushes maturing cells toward center of tubule More immature cells at periphery More differentiated cells are nearer the center Cells that result: only half the number of chromosomes as the original cell When sperm cell nucleus unites with egg cell nucleus: Full number of chromosomes is restored Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

8. Spermiogenesis: last stage Spermatids become mature spermatozoa, or sperm Mature sperm Head Contains 23 chromosomes Surrounded by a nuclear membrane Covered by an acrosome Contains enzymes: help sperm penetrate female gamete Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

Midpiece Contains mitochondria that provide adenosine triphosphate (energy) for the sperm Tail Locomotor region Consists of a flagellum Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

9. Sperm Released into lumen of seminiferous tubule Leave testes Enter epididymis Undergo final maturation Become capable of fertilizing a female gamete Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

Sperm production Begins at puberty Continues throughout the life of a male Entire process (beginning with primary spermatocyte): Takes about 74 days After ejaculation: Sperm can live for 48 hours in female reproductive tract Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

Duct System: Series of Ducts by Which Sperm Reach Outside of Body 1. Epididymis Series of efferent ducts leave testis and enter epididymis b. Epididymis: tightly coiled tube along the posterior margin of each testis Sperm complete maturation process Become fertile as they move through epididymis Mature sperm: stored in lower portion of epididymis Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

2. Ductus deferens (vas deferens) Tubular structure that is continuous with epididymis Peristalic movements: propel sperm through the tube Transports sperm from the epididymis to the ejaculatory duct Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

3. Ejaculatory duct Each ductus deferens: joins duct from the adjacent seminal vesicle Forms an ejaculatory duct b. Function: Empties sperm and fluid from seminal vesicles into urethra Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

4. Urethra Extends from urinary bladder to external urethral orifice Functions as a passageway for: Sperm and fluids from reproductive system Urine from urinary system While reproductive fluids are passing through urethra: Urinary bladder sphincters contract tightly: keep urine from entering urethra Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

Three regions Prostatic urethra: portion that passes through prostate gland Receives ejaculatory duct Receives numerous ducts from prostate gland Membranous urethra: short region that passes through pelvic floor Spongy urethra (also called penile urethra): extends the length of the penis Receives ducts from the bulbourethral glands Opens to the outside at the external urethral orifice Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

Accessory Glands: Secrete Fluids That Enter the Urethra 1. Seminal vesicles Saclike glands Have a short duct that joins with ductus deferens Forms the ejaculatory ducts: empty into the urethra Secrete a fluid: contains fructose Provides an energy source for spermatozoa Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

Prostate Firm, dense structure Located just behind urinary bladder Size of a walnut Encircles urethra Numerous short ducts from prostate gland: empty into prostatic urethra Secretions of prostate: thin, milky colored, alkaline Enhance motility of sperm Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

Bulbourethral glands (Cowper’s glands) Small (size of a pea) Located near the base of penis Short duct from each gland enters penile urethra Secrete an alkaline fluid in response to sexual stimulation Neutralizes acidity of urine residue in urethra Helps neutralize acidity of vagina Provides lubrication for tip of penis during intercourse Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

Seminal Fluid (Semen) Slightly alkaline mixture of: Sperm cells Secretions from accessory glands Volume of semen in a single ejaculation: ml Number of sperm: million sperm per milliliter of semen Sperm counts below million: usually cause fertility problems Only one spermatozoon penetrates and fertilizes an ovum However: takes several million spermatozoa to ensure fertilization Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

Penis Male copulatory organ Transfers sperm to the vagina Consists of three columns of erectile tissue Wrapped in connective tissue and covered with skin Two dorsal columns: corpora cavernosa Single, midline ventral column: corpus spongiosum Surrounds the urethra Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

Parts of the penis a. Root: attaches penis to the pubic arch b. Body (or shaft): visible portion Glans penis: distal end of the penis Formed by expansion of corpus spongiosum Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

Corpus spongiosum: expands at the end of the penis Forms the glans penis Urethral orifice: opening of the penis at tip of glans penis Prepuce (foreskin): loose fold of skin Covers the glans penis Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

Male Sexual Response Absence of sexual arousal
Erectile tissue of penis contains only a small volume of blood Causes penis to be flaccid During sexual excitement: Arterioles that supply blood to the erectile tissue: dilate Spaces in the erectile tissue: become engorged with blood Penis enlarges and become rigid: erection Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

Male Sexual Response, cont.
Continued sexual stimulation Reflexes that promote an erection: become more intense Level is reached that prompts a surge of impulses to genital organs Stimulate rhythmic contractions of: Epididymides, vasa deferentia, and ejaculatory ducts Cause contractions of accessory glands Results in emission: forceful discharge of semen into urethra Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

4. Ejaculation: immediately follows emission Forceful expulsion of semen from urethra to the exterior Sphincters of urinary bladder constrict (during emission and ejaculation) Prevents semen from entering bladder Inhibits flow of urine from the bladder Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

Hormonal Control 1. Puberty in males: reproductive organs become sexually mature Begins: years of age Continues: until years of age Hypothalamus Begins to secrete gonadotropin-releasing hormone (GnRH) Enters blood and goes to anterior pituitary gland Anterior pituitary: starts secreting luteinizing hormone (LH) and follicle-stimulating hormone (FSH) Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

2. LH Promotes growth of interstitial cells (cells of Leydig) in testes Stimulates them to secrete testosterone 3. FSH Binds with receptor sites on sustentacular cells (Sertoli cells) in seminiferous tubules Makes spermatogenic cells respond to stimulation by testosterone Stimulates spermatogenesis in seminiferous tubules Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

4. Testosterone (at puberty) Promotes maturation of male reproductive organs Stimulates spermatogenesis Promotes development of male secondary sex characteristics Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

Female Reproductive System
Functions: Produces and sustains female sex cells (egg cells, or ova) Transports ova to fertilization site Provides favorable environment for developing offspring Moves offspring to outside at end of development period Produces female sex hormones Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

Female Reproductive System, cont.

Ovaries Primary reproductive organs in female Solid, ovoid structures Size and shape of an almond Located in shallow depressions: ovarian fossae One on each side of uterus Held in place by peritoneal ligaments Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

Structure 1. Germinal (ovarian) epithelium: epithelium that covers outside of ovaries 2. Tunica albuginea: dense connective tissue capsule under the epithelium of the ovaries 3. Cortex: outer area of the ovary Contains: Ovarian follicles Oocyte: female germ cell contained in each follicle 4. Medulla: inner area of the ovary Consists of loose connective tissue Abundant blood vessels, lymphatic vessels, and nerve fibers Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

Oogenesis: Process of Egg Formation Early in fetal development Primitive germ cells in the ovaries: differentiate into oogonia 2. Oogonia Divide rapidly: form thousands of cells with 46 (23 pairs) chromosomes Enter a growth phase: become primary oocytes Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

3. Primary oocytes (with 46 chromosomes) Replicate their DNA Begin the first meiotic division Process stops in prophase Cells remain in this suspended state until puberty Ovaries: contain 700,000 primary oocytes at birth Lifetime supply No more will develop By puberty: number of primary oocytes has declined to 400,000 Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

Beginning at puberty: several primary oocytes start to grow again each month One outgrows the others: resumes meiosis I (others degenerate) 5. Meiosis I Primary ooctye: undergoes an unequal division Nearly all the cytoplasm, organelles, and half the chromosomes Goes to one cell: becomes a secondary oocyte Remaining half of the chromosomes: go to a smaller cell (first polar body) Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

6. Meiosis II Secondary oocyte begins the second meiotic division Process stops in metaphase Ovulation occurs If fertilization occurs: meiosis II continues Unequal division: all of the cytoplasm goes to ovum Ovum has 23 single-stranded chromosomes Smaller cell from this division: second polar body 7. If fertilization does not occur: secondary oocyte degenerates Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

Ovarian Follicle Development 1. Ovarian follicle: consists of a developing oocyte Surrounded by one or more layers of cells: follicular cells At the same time the oocyte is going through meiosis: Corresponding changes take place in follicular cells Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

3. Primordial follicles: consist of a primary oocyte Surrounded by a single layer of flattened cells Develop in the fetus Stage that is present: at birth and throughout childhood Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

Beginning at puberty: FSH stimulates changes in primordial follicles Follicular cells become cuboidal Primary oocyte enlarges Becomes a primary follicle Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

5. Primary follicle Continues to grow: under the influence of FSH Follicular cells proliferate Granulosa cells: several layers of cells that form around primary oocyte Most of primary follicles degenerate One continues to develop each month Granulosa cells: start secreting estrogen Cavity forms within follicle: antrum Becomes a secondary follicle Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

6. Secondary follicle Granulosa cells secrete a substance Form a clear membrane around the oocyte: zona pellucida After 10 days of growth: Becomes mature follicle: graafian follicle Forms a “blister” on the surface of the ovary Contains a secondary oocyte ready for ovulation Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

Ovulation 1. Graafian follicle: mature follicle at the surface of the ovary Ruptures Releases secondary oocyte into peritoneal cavity Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

2. Secondary oocyte Surrounded by: Zona pellucid: consists of a clear membrane Corona radiata: consists of several layers of cells If not fertilized: secondary oocyte degenerates If fertilization occurs: Second meiotic division resumes Forms a polar body and a mature ovum Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

4. Corpus luteum Glandular structure Secretes progesterone and estrogen If fertilization does not occur: Remains functional for about 10 days Begins to degenerate into a corpus albicans Consists of scar tissue Hormone output ceases Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

If fertilization occurs: corpus luteum persists Continues to secrete hormones Until placenta develops to secrete necessary hormones Ultimately degenerates into a corpus albicans Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

Genital Tract Uterine Tubes (Fallopian Tubes) Extend laterally from upper portion of the uterus Extend to ovary on that side One tube associated with each ovary End of tube: forms a funnel-shaped infundibulum Surrounded by finger-like extensions: fimbriae No direct connection between the infundibulum and ovary Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

Oocyte enters peritoneal cavity before it enters uterine tube At the time of ovulation: Fimbriae create currents in peritoneal fluid Help propel oocyte into fallopian tube Once inside uterine tube: oocyte is moved along By rhythmic beating of cilia By peristaltic action of smooth muscle in the wall of the tube Journey through fallopian tube: takes about 7 days Oocyte is fertile for only hours Fertilization usually occurs in fallopian tube Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

Uterus Muscular organ that receives the fertilized oocyte Provides environment for developing offspring Located in the pelvic cavity: between rectum and urinary bladder Size: Before the first pregnancy: size and shape of a (upside-down) pear After childbirth: becomes larger After menopause: becomes smaller Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

5. Fundus: upper, bulging surface of uterus 6. Body: large main portion of uterus 7. Cervix: lower narrow region of the uterus that projects into the vagina 8. Internal os: opening of the uterus between the body and cervix 9. External os: opening of the uterus from the cervix into the vagina 10. Broad ligament: holds uterus in place Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

Wall of the uterus a. Perimetrium: outer serous layer b. Myometrium: thick middle layer Consists of smooth muscle Makes up bulk of uterine wall c. Endometrium: inner layer Consists of a mucous membrane Stratum functionale: portion sloughed off during menstruation Stratum basale: provides materials to rebuild stratum functionale after menstruation Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

Vagina Fibromuscular tube Extends from the cervix to the outside Functions: Passageway for menstrual flow Receives penis and semen during sexual intercourse Serves as birth canal Smooth muscle and mucosal lining of vaginal wall capable of stretching Accommodate erect penis Permit passage of a baby Vaginal orifice: opening of the vagina to the outside Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

External Genitalia: Accessory Structures of Female Reproductive System (Vulva) 1. Labia majora: two large fat-filled folds of skin Enclose the other external genitalia Mons pubis: rounded elevation of fat that overlies the pubic symphysis 3. Labia minora: two smaller folds of skin medial to the labia majora 4. Vestibule: area between the two labia minora Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

5. Clitoris: small mass of erectile tissue located at anterior end of vestibule Becomes erect in response to sexual stimulation 6. Prepuce: fold of skin that covers the clitoris 7. Paraurethral glands: open into vestibule on each side of urethral orifice Secrete mucus 8. Greater vestibular glands (Bartholin’s glands): open into vestibule next to vaginal orifice Produce a mucous-like secretion Provides lubrication during sexual intercourse Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

Female Sexual Response Similar to that of the male Body’s responses to sexual stimuli Increased blood flow to clitoris, vaginal mucosa, breasts, nipples Clitoris and nipples: become rigid and erect Breasts and vaginal mucosa: enlarge Glands in cervix and vestibular glands: secrete fluids Lubricate vaginal mucosa Continued stimulation: culminates in orgasm Accompanied by: rhythmic contractions of uterus and muscles of the pelvic floor Helps the movement of sperm through the uterus toward uterine tubes Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

Hormonal Control Hypothalamus secretes: a. Gonadotropin-releasing hormone (GnRH) Stimulates anterior pituitary to secrete FSH and small amounts of LH Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

Anterior pituitary secretes: a. FSH Stimulates growth of ovarian follicles Stimulates estrogen production by ovaries b. LH Stimulates ovulation to occur Stimulates production of progesterone and estrogen by ovaries Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

4. At puberty: Hypothalamus: secretes GnRH Enters blood and goes to anterior pituitary gland Anterior pituitary: secretes FSH and LH FSH and LH: affect ovaries and uterus Monthly cycles begin Menarche: first period of menstrual bleeding Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

Ovarian Cycle: changes that take place within ovary each month 1. Follicular phase: triggered by secretion of GnRH by hypothalamus GnRH stimulates anterior pituitary to secrete: FSH (and a small amount of LH) FSH Stimulates growth of ovarian follicles Stimulates estrogen production by follicle cells As follicles enlarge: estrogen secretion by follicle cells increases Follicle continues to grow and mature until middle of the cycle Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

2. Ovulatory phase High levels of estrogen secreted by mature follicle cells Stimulates anterior pituitary to secrete increased amount of LH (and a small amount of FSH) b. Surge of LH Stimulates resumption of meiosis in oocyte Causes rupture of mature (graafian) follicle Oocyte released into peritoneal cavity Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

3. Luteal phase Surge of LH also stimulates: Development of corpus luteum from ruptured follicle Corpus luteum to secrete progesterone and some estrogen Exerts a negative feedback effect on hypothalamus and anterior pituitary FSH and LH levels decline As LH level declines: corpus luteum activity declines Ovarian cycle starts over Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

Uterine (Menstrual) Cycle: changes that take place to the endometrium of the uterus each month 1. Menstrual phase Begins on the first day of the cycle Continues for 3-5 days Stratum functionale (outer layer of endometrium) Detaches from uterine wall Passes through the vagina: menstrual flow During this time: follicles are growing in ovary Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

2. Proliferative phase Begins with the end of the menstrual phase Lasts about 8 days b. Estrogen: secreted by growing follicles in ovary Stimulates repair of endometrium Endometrium thickens, glands develop, blood vessels grow Ovulation occurs at the end of this phase Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

3. Secretory phase Progesterone: secreted by the corpus luteum Stimulates continued growth and thickening of endometrium Arteries and glands grow and enlarge Glands secrete glycogen Nourish a developing embryo if fertilization occurs If fertilization does not occur: Corpus luteum degenerates (progesterone and estrogen secretion ceases) Causes menstruation to occur Uterine cycle starts over again Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

Menopause: cessation of the female reproductive cycles First changes occur in the ovary By age 45 or 50: Ovarian follicles cease responding to FSH and LH Follicle cells do not produce estrogen Ovulation ceases Corpus luteum does not result (no progesterone secreted) Without estrogen and progesterone: Cyclic changes in uterus stop Menstruation ceases Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

Mammary Glands Organs of milk production Located in the breast: overlying pectoralis major muscles 3. Nipple Surrounded by a circular pigmented area: areola Lobes of glandular tissue (15-20 in each breast) Radiate around the nipple Separated by: Connective tissue: helps support the breasts Adipose tissue: determines size and shape of breast Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

Each lobe consists of lobules Contain the glandular units 6. Lactiferous duct: collects milk from the lobules and carries it to nipple Lactiferous duct enlarges: forms a lactiferous sinus (ampulla) Serves as a reservoir for milk Duct again narrows and opens on surface of nipple Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

Mammary gland function: regulated by hormones At puberty: Estrogen: Stimulates development of glandular tissue Causes breasts to increase in size Progesterone stimulates: Development of duct system Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

During pregnancy: Estrogen and progesterone further enhance development of mammary glands Prolactin: stimulates production of milk within the glandular tissue Oxytocin: causes ejection of milk from the glands Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

Posttest True or False The interstitial cells in the testes produce male sex hormones. Spermatogonia divide by mitosis. The epididymis secretes a fluid containing fructose to provide an energy source for sperm. Ejaculation is the forceful discharge of semen into the urethra. The epididymis is a tightly coiled tube in which sperm complete the maturation process. Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

Posttest, cont. True or False
If fertilization does not take place, the corpus luteum continues to grow and enlarge. Fimbriae help propel sperm through the uterus. The growth of the ovarian follicle occurs during the follicular phase of the ovarian cycle. In the female, LH is responsible for stimulating the growth and thickening of the endometrium. The upper bulging surface of the uterus is the fundus. Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc.

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