Exam 4: Chapter 28: Reproductive System Flashcards
(139 cards)
1
Q
Gametogenesis
Fertilization
Development and nourishment of a new individual
Production of reproductive hormones
A
Functions of the Reproductive System
2
Q
*Is the production of gametes, which are reproductive cells that are produced in the gonads
*The male gonads are the testes, which are the site of sperm cell production
*The female gonads are the ovaries, which are the site of oocyte (egg) production
A
Gametogenesis
3
Q
*The reproductive system enables ______ of the oocyte by the sperm
*The duct system in males nourishes sperm cells until they are mature and are deposited in the female reproductive tract by the penis
*The female reproductive system receives the sperm cells from the male and provides a passageway for them to the ______ site
A
Fertilization
4
Q
*The female reproductive system nurtures the developing fetus in the uterus until birth and provides nourishment (breast milk) after birth
A
Development and nourishment of a new individual
5
Q
*Hormones produced by the reproductive system control its development and the development of the sex-specific body form
*These hormones are also essential for the routine functions of the reproductive system and for reproductive behavior
A
Production of reproductive hormones
6
Q
Cell division that produces haploid cells
A
Meiosis
7
Q
*Sperm cells and oocytes contain the _______ number of chromosomes, or 23
*Each gamete contains one chromosome from each of the homologous pairs
*Reduction in the number of chromosomes in sperm cells or oocytes to a _____ number is important
*When a sperm cell and an oocyte fuse to form a fertilized egg, each provides a haploid number of chromosomes, which reestablishes a diploid number
*If meiosis did not take place, the number of chromosomes in the fertilized oocyte would double each time fertilization occurred, and the extra chromosomal material would be lethal to the developing offspring
A
Haploid
8
Q
*In humans, the somatic cells normally have 46 chromosomes, called the ______ number
A
Diploid
9
Q
*Chromosomes exist in 23 homologous pairs-22 autosomal pairs and 1 pair of sex chromosomes
*One chromosome of each homologous pair is inherited from the male parent, and the other chromosome of each pair is inherited from the female parent
*The chromosomes of each homologous pair are alike in size and shape and contain genes for the same traits, with the exception of the X chromosome and Y chromosome
*The combination of sex chromosomes is known as the sexual karyotype
*The female sexual karyotype is two X chromosomes; the male sexual karyotype includes one X chromosome and one Y chromosome
*Though the X and Y chromosomes pair during meiosis, they are not the same size, nor do they carry the same genetic information
A
Homologous Chromosomes
10
Q
Reductional division
Early prophase I
Middle prophase I
Metaphase I
Anaphase I
Telophase I
A
Meiosis I
11
Q
At the beginning of meiosis, each of the 46 duplicated chromosomes consists of two sister chromatids connected by a centromere
A
Early Prophase I
12
Q
The chromosomes become visible, and the homologous pairs come together in a process called synapsis
oBecause each chromosome consists of two chromatids, the paring of the homologous chromosomes brigs two chromatids of each chromosome close together, an arrangement called a tetrad
oOccasionally, part of a chromatid of one homologous chromosome breaks off and is exchanged with part of another chromatid from the other homologous chromosome
oThis exchange of genetic material between maternal and paternal chromosomes is called crossing over and may result in new gene combinations on the chromosomes
A
Middle Prophase I
13
Q
Homologous pairs of chromosomes line up near the center of the cell
oFor each homologous pair, however, the orientation of the maternal and paternal chromosomes is random
oThis random alignment and crossing over are responsible for the large degree of diversity in the genetic composition of sperm cells and oocytes produced by each individual
A
Metaphase I
14
Q
The chromosomes of homologous pairs separate and are moved to opposite sides of the cell
A
Anaphase I
15
Q
New nuclei form, and the cell completes division of the cytoplasm to form two cells
*When meiosis I is complete, each daughter cell has 1 chromosome from each homologous pair
*Because the chromosome number is reduced from a diploid number (46 chromosomes, or 23 pairs) to a haploid number (23 chromosomes, or 1 from each homologous pair) during meiosis I, this division is often called a reduction division
*At the end of meiosis I, each of the 23 chromosomes in the daughter cells still consists of two chromatids
*The separation of the chromatids of the duplicated chromosomes occurs in meiosis II
*The second meiotic division is similar to mitosis
A
Telophase I
16
Q
Equational division
Prophase II
Metaphase II
Anaphase II
Telophase II
A
Meiosis II
17
Q
As the chromosomes condense, it is apparent that each is duplicated, consisting of two chromatids
A
Prophase II
18
Q
The duplicated chromosomes line up near the middle of the cell
A
Metaphase II
19
Q
The chromatids are separated at the centromere and are moved to opposite sides of the cell so that each daughter cell receives one of the chromatids from each chromosome
oWhen the centromere separates, each of the chromatids is called a chromosome
A
Anaphase II
20
Q
New nuclei from around the chromosomes and the cells divide to form four daughter cells each containing 23 chromosomes
A
Telophase II
21
Q
Production, maintenance, and distribution of male gametes
A
Function of the Male Reproductive System
22
Q
Testes, epididymis, ductus deferens, ejaculatory duct, urethra, seminal vesicles, prostate gland, bulbourethral gland, scrotum and penis
A
The Male Reproductive System Includes
23
Q
Site of spermatogenesis (sperm production)
*Are small, oval-shaped organs, each about 4-5cm long, within the scrotum
*Function as both exocrine and endocrine glands
*Their major exocrine secretion is sperm cells, and their major endocrine secretion is the hormone testosterone
*The outer part of each _____ is a thick, white capsule consisting mostly of fibrous connective tissue called the tunica albuginea
*Extensions of the tunica albuginea extend into the ______ and form incomplete septa
*The septa divide each ____ into about 300-400 cone-shaped lobules
A
Testes
24
Q
*The lobules contain _______, in which sperm cells develop
*The combined length of the _______ is nearly half a mile
*Considering that sperm cells are produced in the _______, it is not surprising that adult males are capable of producing more than 100 million mature sperm each day
*Empty into a set of short, straight tubules called the tubuli recti
*These in turn empty into a tubular network called the rete testis
*The rete testis empties into 15-20 tubules called efferent ductules that pass through the tunica albuginea to exit the testis
*The efferent ductules have a ciliated pseudostratified columnar epithelium, which helps move sperm cells out of the testis
A
Seminiferous Tubules
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Interstitial cells
Cellular stages of spermatogenesis
Sustentacular cells
Each Tubule is Surrounded by a Capsule that Contains
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oLoose connective tissue surrounding the seminiferous tubules contains clusters of endocrine cells called ______, or Leydig cells
oSecrete testosterone
Interstitial Cells
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oSpermatogonia
oSpermatocytes
oSpermatids
oSpermatozoa
Cellular Stages of Spermatogenesis
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*Sperm cell development, occurs in the seminiferous tubules
*Before puberty, the testes remain relatively simple and unchanged from the time of their initial development
*The interstitial cells are not particularly prominent during this period, and the seminiferous tubules lack a lumen and are not yet functional
*At 12-14 years of age, the interstitial cells increase in number and size, a lumen develops in each seminiferous tubule, and sperm cell production begins
*It takes approximately 74 days for sperm cells to be produced
*For about 50 of those days, the sperm cells are in the seminiferous tubules
*The seminiferous tubules, the site of spermatogenesis, contain two types of cells: 1.germ cells and 2sustenttacular cells, or Sertoli cells (nurse cells)
*The germ cells are what divide and differentiate during _______ to form sperm cells
Spermatogenesis
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*The sustentacular cells are large cells that extend to form the periphery to the lumen of the seminiferous tubule
*The sustentacular cells nourish the germ cells and produce, together with the interstitial cells, a number of hormones, such as androgens, estrogens, and inhibins
*In addition, tight junctions between the sustentacular cells form a blood-testis barrier between germ cells and sperm cells.
*The blood-testis barrier isolates the sperm cells from the immune system
*This barrier is necessary because, as the sperm cells develop, they form surface antigens that could stimulate an immune response, resulting in their destruction
*Interstitial cells secrete testosterone, which passes into the sustentacular cells and binds to intracellular receptors
Spermatogenesis
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*This binding enables the sustentacular cells to function normally
*In addition, testosterone in the sustentacular cells is converted to two other steroids: 1.dihydrotestosterone and 2.estradiol, a specific type of estrogen
*These hormones are then secreted by the sustentacular cells
*The sustentacular cells also secrete sex hormone binding globulin (SHBG), also called androgen-binding protein, into the seminiferous tubules
*Testosterone and dihydrotestosterone bind to androgen-binding protein and are carried along with other secretions of the seminiferous tubules to the epididymis
*Follicle-stimulating hormones, synergistically with testosterone, induce sperm cell formation
Spermatogenesis
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*Meiosis I, the primary spermatocyte divides to produce two haploid secondary spermatocytes.
*Meiosis II, each secondary spermatocyte divides to produce two haploid spermatids.
Summary of Spermatogenesis
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oGerm cells are partially embedded in the sustentacular cells
The most peripheral cells, those adjacent to the basement membrane of the seminiferous tubules, are spermatogonia, which divide by mitosis
Some of the daughter cells produced from these mitotic divisions remain spermatogonia and continue to produce additional spermatogonia
Other daughter cells differentiate to form primary spermatocytes, which divide by meiosis
oSpermatogenesis begins when the primary spermatocytes divide.
Primary spermatocytes are diploid cells
Each primary spermatocyte passes through the first meiotic division to produce two secondary spermatocytes
oThe secondary spermatocytes are haploid cells, each containing 23 duplicated chromosomes
Each secondary spermatocyte undergoes a second meiotic division to produce two even smaller cells called spermatids
Each spermatid is a haploid cell with nonreplicated chromosomes, which means each contains 23 chromosomes, a combination of 22 autosomes and either an X or a Y chromosome
oEach spermatid undergoes the last phase of spermatogenesis, called spermiogenesis, to form a mature sperm cell, or spermatozoon
The Process of Spermatogenesis
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*During ______, each spermatid develops a head, a midpiece, and a tail, or flagellum
Spermiogenesis
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Head
Neck
Midpeice
Tail
The Structure of a Spermatozoa
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*The nucleus of the sperm is located in the _______
a. Acrosomal cap
*Just anterior to the nucleus is a vesicle called the acrosome, which contains enzymes necessary for the sperm cell to penetrate the female oocyte
Head
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*Contains large numbers of mitochondria, which produce the ATP necessary for microtubule movement
Midpiece
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*The flagellum is similar to a cilium, and microtubules within the flagellum move, propelling the sperm cell forward
Tail
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*The efferent ductules from each testis become extremely convoluted and form a comma-shaped structure on the posterior side of the testis called the ______
*Each _______ consists of a head, a body, and a long tail
*The head contains the convoluted efferent ductules, which empty into the duct of the ______, a single convoluted tubule located primarily within the body of the _______
*This duct alone, if unraveled, would extend for several meters
*The duct of the ______ has pseudostratified columnar epithelium with elongated microvilli called stereocilia
*The stereocilia increase the surface area of the epithelial cells that absorb fluid from the lumen of the duct of the _______
*The duct of the _______ ends at the tail of the ______, which is located at the inferior border of the testis
Epididymis
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*The final maturation of the sperm cells occurs within the _______
*It takes 12-16 days for sperm to travel through the epididymis and appear in the ejaculate
*Several structural and functional changes occur in the sperm cells as they pass through the _______
*Structural changes include a further reduction in cytoplasm and maturation of the acrosome
*Functionally, the sperm cells develop the ability to bind to the zona pellucida of the secondary oocyte during fertilization
*Sperm cells taken from the head of the _______ are unable to fertilize secondary oocytes, and they are not yet able to become motile; however, sperm cells taken from the tail of the ______ are able to perform both functions
Epididymis
40
*Or vas deferens, emerges from the tail of the epididymis and ascends along the posterior side of the testis medial to the epididymis, where it associated with the blood vessel and nerves that supply the testis to form the spermatic cord
*The spermatic cord consists of 1.the _______, 2.the testicular artery and venous plexus, 3.lympathic vessels, 4.nerves, and 5.fibrous remnants of the process vaginalis
*The coverings of the spermatic cord include 1.the external spermatic fascia; 2.the cremaster muscle, and extension of the muscle fibers of the internal abdominal oblique muscle of the abdomen; and 3.the internal spermatic fascia
*The ______ and the rest of the spermatic cord structures ascend and pass through the inguinal canal to enter the pelvic cavity
*The ______ crosses the lateral and posterior walls of the pelvic cavity, travels over the ureter, and loops over the posterior surface of the urinary bladder to approach the prostate gland
*Near the prostate gland, the end of the ______ enlarges to form an ampulla
*The lumen of the ________ is lined with pseudostratified columnar epithelium, which is surrounded by smooth muscle
*Peristaltic contractions of the smooth muscle help propel sperm cells through the ________
Ductus Deferens
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*Adjacent to the ampulla of each ductus deferens is a sac-shaped gland called the seminal vesicle
*A short duct from each seminal vesicle joins the ampulla of the ductus deferens to form the _______
*Each ______ is approximately 2.5cm long
*These ducts extend into the prostate gland and open into the urethra
Ejaculatory Duct
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*The male ______ is about 20cm long and extends from the urinary bladder to the distal end of the penis
*Is a passageway for both urine and male reproductive fluids
*Is divided into three parts: 1.the prostatic _____, 2.the membranous _____, and 3.the spongy _______
*The prostatic ______ is connected to the bladder and passes through the prostate gland
*Fifteen to 30 small ducts form the prostate gland and the two ejaculatory ducts empty into the prostatic ______
*The membranous ______ is the shortest part of the ______, extending from the prostate gland through the perineum
*The spongy _______, also called the penile _______, is the longest part of the ______; its extends from the membranous ______ through the length of the penis, where it opens to the exterior at the external _______ orifice
*In rare cases, the penis does not develop normally, and the ______ may open to the exterior along the inferior surface of the penis
*Stratified columnar epithelium lines most of the _____, but transitional epithelium is in the prostatic ______ near the bladder, and stratified squamous epithelium is near the external ______ orifice of the spongy _______
*Several minute, mucus-secreting _______ glands empty into the _______
Urethra
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*Is the male organ of copulation, through which sperm cells are transferred from the male to the female
*Contains three columns of erectile tissue
*Erectile tissue is composed of a network of connective tissue and smooth muscle tissue with many sinusoids, or spaces, that can fill with blood
*This condition is referred to as engorgement
*Engorgement of this erectile tissue causes the ____ to enlarge and become firm, a process called erection
*The spongy urethra passes through the corpus spongiosum, penetrates the glans ____, and opens as the external urethral orifice
Penis
44
*At the base of the____, the corpus spongiosum expands to form the bulb of the ______
*Each corpus cavernosum expands to form the crus of the _____, which attaches the ______ to the pelvic bones
*Together, the bulb of the _____ and the crura of the _____ constitute the root of the _____
*Skin is loosely attached to the connective tissue that surrounds the erectile columns in the shaft of the _____
*The skin is firmly attached at the base of the glans _____, and a thinner layer of skin tightly covers the glans _____
*The skin of the _____, especially the glans _____, is well supplied with sensory receptors
*A loose fold of skin called the prepuce, or foreskin, covers the glans _____
*The primary nerves, arteries, and veins of the _____ pass along its dorsal surface
*Dorsal arteries, with dorsal nerves lateral to them, exist on each side of a single, midline dorsal vein
*Additional deep arteries lie within the corpora cavernosa
*Copulatory organ
*Erectile tissue
Penis
45
Are the erectile columns that form the dorsum ad sides of the penis
Corpora Cavernosa
46
The third column, the ______, forms the ventral portion of the penis
Corpus Spongiosum
47
o The corpus spongiosum expands to form a cap, the ____, over the distal end of the penis
Glans Penis
48
Seminal vesicles
Prostate gland
Bulbourethral gland
Accessory Glands of the Male Reproductive System
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oAre sac-shaped glands located next to the ampullae of the ducta deferentia
oEach gland is about 5cm long and tapers into a short excretory duct that joins the ampulla of the ductus deferens to form the ejaculatory duct
oHave a capsule containing fibrous connective tissue and smooth muscle cells
Seminal Vesicles
50
oConsists of both glandular and muscular tissue
oIt resembles a walnut in shape and size and is approximately 4cm long and 2cm wide
oIt is dorsal to the pubic symphysis at the base of the urinary bladder, where it surrounds the prostatic urethra and the two ejaculatory ducts
oIs composed of a fibrous connective tissue capsule containing distinct smooth muscle cells and numerous fibrous partitions, also containing smooth muscle, that radiate inward toward the urethra
oCovering these muscular partitions is a layer of columnar epithelial cells that form saccular dilations
oThe columnar cells secrete prostatic fluid into the saccular dilations
oFifteen to 30 small prostatic ducts carry these secretions into the prostatic urethra
Prostate Gland
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oThe _______, or Cowper glands, are a pair of small glands located near the membranous urethra
oIn young males, each gland is about the size of a pea, but they decrease in size with age and are almost impossible to detect in older males
oEach ________ is a compound mucous gland
oThe small ducts of each gland unite to form a single duct, which empties into the spongy urethra at the base of the penis
Bulbourethral Gland
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*Secretions from accessory glands and sperm cells
*Collectively, the sperm cells and secretions from the accessory glands are called _____
*The seminal vesicles produce about 60% of the fluid, the prostate gland contributes about 30%, the testes contribute 5%, and the bulbourethral glands contribute 5%
Semen
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*The major component of the testicular secretions is sperm cells
*In addition to the sperm cells, the testes also secrete a small amount of fluid necessary for moving the sperm cells through the reproductive tract
*Metabolic by-products are also included in this fluid, as sperm cells carry out basic cellular processes
*The bulbourethral glands and urethral mucous glands produce a mucous secretion just before ejaculation
*This alkaline mucous secretion has four major functions: 1.lubricating the urethra for sperm movement, 2.neutralizing the acidic fluids of the spongy urethra, 3.providing a small amount of lubrication during intercourse, and 4.reducing vaginal acidity
Secretions in the Testes, Bublourethral Gland, and Urethra
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*The thick, mucuslike secretions of the seminal vesicles contain many substances, each with a specific function
Secretions in the Seminal Vesicles
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Nourishment of sperm cells
Coagulation of semen
Movement of sperm cells
The Functions of these Substances Include
56
Fructose, citric acid, and other nutrients nourish the sperm cells
Nourishment of Sperm Cells
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The seminal vesicle secretions contain fibrinogen, which is involved in a weak coagulation reaction of the semen immediately after ejaculation
Coagulation of Semen
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Prostaglandins within the seminal vesicle secretions stimulate uterine contractions, which help transport sperm cells through the female reproductive tract to the site of fertilization
Movement of Sperm Cells
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*The prostate produces a thin, milky, alkaline secretion
*In combination with secretions of the seminal vesicles, bulbourethral glands, and urethral mucous glands, the prostatic secretions help neutralize the acidic urethra
*The secretions of the prostate and seminal vesicles also help neutralize the acidic secretions of the testes and the vagina
*In addition, the prostatic secretions are important in the transient coagulation of semen because they contain clotting factors that convert fibrinogen from the seminal vesicles to fibrin, resulting in coagulation
*The coagulated material keeps the semen a sticky mass for a few minutes after ejaculation, and then fibrinolysin, also secreted by the prostate, causes the mass to dissolve
*This releases the sperm cells to make their way through the female reproductive tract
Secretions in the Prostate Gland
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GnRH
LH
FSH
Testosterone
Hormones of Male Reproduction
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oA small peptide hormone called _______ is released from neurons in the hypothalamus
oGnRH passes through the hypothalamohypophysial portal system to the anterior pituitary gland
oIn response to GnRH, cells within the anterior pituitary gland secrete two hormones, referred to as gonadotropins because they influence the function of the gonads
oGnRH can be produced synthetically; if administered in small amounts in frequent pulses or surges, it can be useful in treating male infertility
oChronically elevated GnRH levels in the blood cause the anterior pituitary cells to become insensitive to stimulation by GnRH molecules, and little LH or FSH is secreted
oLong-term administration of synthetic GnRH, therefore, can reduce sperm cell production, causing infertility
*For GnRH to stimulate the secretion of large quantities of LH and FSH and thereby influence sperm cell production, the anterior pituitary must be exposed to a series of pulses, or brief increases and decreases in GnRH
Gonadotropin-Releasing Hormone (GnRH)
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oA gonadotropin
oSometimes is called interstitial cell-stimulating hormone (ICSH)
oLH binds to the interstitial cells in the testes and causes them to increase their rate of testosterone synthesis and secretion
Luteinizing Hormone (LH).
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oA gonadotropin
oFSH binds primarily to sustentacular cells in the seminiferous tubules and promotes sperm cell development
oIt also increases the secretion of a hormone called inhibin
Follicle Stimulating Hormone (FSH)
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oHas a stimulatory effect on the sustentacular cells of seminiferous tubules, as well as on the development of reproductive organs and secondary sexual characteristics
oIs the major male hormone secreted by the testes
oIt is classified as an androgen because it stimulates the development of male reproductive structures and male secondary sexual characteristics
oThe testes secrete other androgens, but they are produced in smaller concentrations and are less potent than ______
oIn addition, the testes secrete small amounts of estrogen and progesterone
oCauses the enlargement and differentiation of the male genitals and reproductive duct system and is necessary for sperm cell formation
Testosterone
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oAffects the development of secondary sexual characteristics, which are those structural and behavioral changes, other than in the reproductive organs, that develop at puberty and distinguish males from females
oStimulates growth of thicker, coarser, pigmented hair in the pubic area and extending up the linea alba, as well as on the legs, chest, axillary region, face, and back
oCauses existing vellus hair to be converted to terminal hair, which is coarser and more pigmented
oAffects the appearance of the skin
oSpecifically, it causes the texture of the skin to become rougher or coarser
oThe quantity of melanin in the skin also increases, making the skin darker
oIncreases the rate of secretion from the sebaceous glands, especially on the face
Testosterone
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oNear puberty, the increases ______ level and increased sebaceous gland secretion frequently cause acne
oAlso causes hypertrophy of the larynx and reduced tension on the vocal folds, beginning near puberty
oAt first, the structural changes can make the voice difficult to control, but ultimately its normal masculine quality is achieved
oStimulates metabolism so that males have a slightly higher metabolic rate than females
oThe red blood cell count increases by nearly 20% as a result of ____ effect on erythropoietin production
Testosterone
67
oAlso has a minor mineralocorticoid-like effect, causing Na+ to be retained in the body and, consequently, an increased volume of body fluids
oPromotes protein synthesis in most tissues; as a result, skeletal muscle mass increases at puberty
oThe average percentage of the body weight composed of skeletal muscle is greater for males than for females because of the effect of androgens
oIs required to initiate and maintain male sexual behavior
oEnters cells within the hypothalamus and the surrounding areas of the brain and influences their function, resulting in sexual behavior
Testosterone
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*When _____ occurs, the penis becomes enlarged and rigid
*Is the first major component of the male sex act
*Action potentials travel from the spinal cord through the pudendal nerve to the arteries that supply blood to the erectile tissues
*The release of acetylcholine and nitric oxide causes smooth muscle cells to relax and blood vessels to dilate
*At the same time, other arteries of the penis. Constrict to shunt blood to the erectile tissues
*As a consequence, blood fills the sinusoids of the erectile tissue and compresses the veins
*Because venous outflow is partially occluded, the blood pressure in the sinusoids causes inflation and rigidity of the erectile tissue
*Nerve action potentials that result in _____ come from parasympathetic centers (S2-S4) or sympathetic centers (T2-L1) in the spinal cord
*Normally the parasympathetic centers are more important for _____; however, in cases of damage to the sacral region of the spinal cord, _____ can occur through the sympathetic system
*Parasympathetic action potentials also cause the mucous glands within the penile urethra and the bulbourethral glands at the base of the penis to secrete mucus
Erection
69
*Is the discharge of all these secretions from the ducta deferentia into the urethra
*Is the accumulation of sperm cells and secretions of the accessory glands in the urethra
*Sympathetic centers in the spinal cord (T12-L1), which are stimulated as the level of sexual tension increases, control _____
*Sympathetic action potentials cause peristaltic contractions of the reproductive ducts and stimulate the seminal vesicles and the prostate gland to release their secretions
*Consequently, semen accumulates in the prostatic urethra and produces sensory action potentials that pass through the pudendal nerves to the spinal cord
*Integration of these action potentials results in both sympathetic and somatic motor output
*Sympathetic action potentials cause the internal sphincter of the urinary bladder to constrict so that semen and urine are not mixed
Emission
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*Is the forceful expulsion of semen from the urethra caused by contraction of the urethra, the skeletal muscles in the pelvic floor, and the muscles at the base of the penis
*Somatic motor action potentials travel to the skeletal muscles of the urogenital diaphragm and the base of the penis, causing _____ by several rhythmic contractions that force the semen out of the urethra
*Muscle tension increases throughout the body as well
Ejaculation
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*Produce hormones
*Produce gametes: ova
*Protect, support and nourish a developing embryo
*Nourish newborn infant
Functions of the Female Reproductive System
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Ovaries, uterine tube, uterus, vagina, external genitalia
The Female Reproductive System Includes
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*Gonads
*Site of oogenesis
*The two ____, the female gonads, are small organs about 2-3.5cm long and 1-1.5cm wide
*A peritoneal fold called the mesovarium attaches each ovary to the posterior surface of the broad ligament
*Two other ligaments are associated with the ovary: 1.the suspensory ligament, which extends from the mesovarium to the body wall, and 2.the ovarian ligament, which attaches the ovary to the superior margin of the uterus
*The ovarian arteries, veins, and nerves traverse the suspensory ligament and enter the ovary through the mesovarium
Ovaries
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*The ovary is covered by a portion of the visceral peritoneum, made up of simple cuboidal epithelium, called the ovarian epithelium, or germinal epithelium
*Immediately below the ovarian epithelium is a capsule of dense fibrous connective tissue called the tunica albuginea
*The tissue of the ovary is divided into two areas: the cortex and the medulla
*The cortex is the denser, outer part of the ovary, and the medulla is the looser, inner part of the ovary, and the medulla is the looser, inner part of the ovary
*The connective tissue of the ovary is called the stroma
*Numerous ovarian follicles, each of which contains an oocyte, are distributed throughout the stroma of the cortex
*Blood vessels, lymphatic vessels, and nerves from the mesovarium enter the medulla
Ovarian Histology
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*The process of gamete production in females is called ______
*This process begins before a female is born
Oogenesis
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*By the fourth month of development, the ovaries contain 5 million oogonia, the cells from which oocytes develop
*By the time of birth, many of the oogonia have degenerated, and the remaining ones have differentiated into cells that have begun meiosis
*Oogonia can form after birth from stem cells, but the extent to which this occurs, and how long it occurs, is not clear
*During development, oogonia increase in number by mitosis
*Before birth, most of the oogonia have differentiated into primary oocytes
Oogonium
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*Which are diploid cells, begin the process of meiosis I
*Meiosis stops at birth, however, during the first meiotic division at prophase I
*At puberty,_____ will reenter and complete meiosis I just before ovulation
*Unlike meiosis in males, cytoplasm is split unevenly between the two haploid cells
Primary Oocyte
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*Most of the cytoplasm remains with the ______, resulting in a larger cell
*The cytoplasm contains organelles, such as mitochondria, and nutrients that increase the viability of the_____
*The smaller first polar body has less cytoplasm and therefore few organelles and nutrients
*It either degenerated or divides, producing second polar bodies, which eventually degenerate
*Ovulation is the release of a _____ from an ovary
*Begins the second meiotic division, but stalls at metaphase II unless fertilization occurs
*Fertilization begins when a sperm cell binds to and penetrates the plasma membrane of a _______
*Subsequently, the ______ completes the second meiotic division to form two cells, each containing 23 chromosomes
*One of these cells has very little cytoplasm and is called the second polar body, which degenerates
*The other, larger cell is often called the ovum
Secondary Oocyte
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*At ________, the 23 chromosomes from the sperm cell nucleus join with the 23 chromosomes from the oocyte to from a zygote
*The zygote has 23 pairs of chromosomes (a total of 46 chromosomes)
*All cells of the human body contain 23 pairs of chromosomes, except for the male and female gametes
*The zygote divides by mitosis to form two cells, which divide to form four cells, and so on
*Seven days after ovulation, the mass of cells may implant in or attach to the uterine wall
*The implanted mass of cells continues to develop for approximately 9 months to form a new individual
Fertilization
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The primary oocyte enter meiosis during embryonic development, but stall before completing the division. At puberty, one cell per month continues the process of cellular division to produce a gamete.
Females are Born with a Set Number of Primary Oocytes
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*Within the cortex of the ovary are specialized structures called _______
*These follicles contain the developing primary oocytes
*As the primary oocytes progress through meiosis I, the ______ undergoes development, changing in size and structure
*The ovarian cycle refers to the reoccurring events that take place in the ovaries of sexually mature, nonpregnant females, particularly the changes in the _______
*The ovarian cycle is hormonally regulated
Ovarian Follicles
82
oOogenesis begins when a female is in her mother’s uterus
The primary oocytes present at birth are located in the primordial follicles
A primordial follicle is a primary oocyte surrounded by a single layer of flat cells, called granulosa cells
oAt birth a female possesses about 2 million primary oocytes
From birth to puberty, the number of primary oocytes decreases to around 300,000-400,000
On average, about 400 primary oocytes will actually complete development and give rise to the secondary oocytes that are eventually released from the ovaries
oOnce puberty begins, some of the primordial follicles become primary follicles
This transition to a primary follicle occurs as the oocyte enlarges and the single layer of granulose cells becomes thicker and the cells become cuboidal in shape
Subsequently, several layers of granulosa cells form, and a layer of clear material called the zona pellucida is deposited around the primary oocyte
oApproximately every 28 days, hormonal changes stimulate some of the primary follicles to continue to develop
The primary follicle becomes a secondary follicle as fluid-filled spaces called vesicles form among the granulosa cells, and a capsule called the theca forms around the follicle
Cells of the theca interna surround the granulosa cells, where they participate in the synthesis of ovarian hormones
The theca externa is primarily connective tissue that merges with the stroma of the ovary
Follicle Changes that Occur During the Ovarian Cycle
83
oThe secondary follicle continues to enlarge
When the fluid-filled vesicles fuse to form a single, fluid-filled chamber called the antrum, the follicle is called a mature follicle, or Graafian follicle
In the mature follicle, the oocyte is pushed off to one side and lies in a mass of granulosa cells called the cumulus cells, or cumulus oophorus
oThe mature follicle forms a lump of the surface of the ovary
During ovulation, the mature follicle ruptures, releasing a small amount of blood, follicular fluid, and the oocyte, surrounded by the cumulus cells, into the peritoneal cavity
The cumulus cells resemble a crown radiating from the oocyte and are thus called the corona radiata
Usually, only one mature follicle reaches the most advanced stages of development and is ovulated
The other follicles that were undergoing this maturation process degenerate, a process called atresia
oAfter ovulation, the ruptured mature follicle still has an important function.
It is transformed into an endocrine structure called the corpus luteum
The corpus luteum has a convoluted appearance as a result of its collapse after ovulation
The granulosa cells and the theca interna, now called luteal cells, enlarge and begin to secrete hormones-progesterone and smaller amounts of estrogen
If pregnancy occurs, the corpus luteum enlarges and remains active, particularly through the first trimester, as the corpus luteum of pregnancy
oIf pregnancy does not occur, the corpus luteum remains functional for about 10-12 days and then begins to degenerate
As the corpus luteum degenerates, progesterone and estrogen secretion decreases
Within the corpus luteum, connective tissue cells become enlarged and clear, giving the whole structure a whitish color
The structure is then called the corpus albicans
The corpus albicans continues to shrink and eventually disappears after several months or even years
Follicle Changes that Occur During the Ovarian Cycle
84
*A _______, also called a fallopian tube or oviduct, is associated with each ovary
*It extends from the area of the ovary to the uterus
*Each _____ is located along the superior margin of the broad ligament
*The part of the broad ligament most directly associated with the _____ is called the mesosalpinx
*Opens directly into the peritoneal cavity to receive the secondary oocyte released from the ovary during ovulation
*Carry ovum from ovary to uterus
Uterine Tubes
85
*Fertilization of ovum usually occurs at the border between the ampulla and isthmus
*The uterine part, or intramural part, of the ______ passes through the uterine wall and ends in a very small uterine opening
*The wall of each _____ consists of three layers: 1.the serosa, 2.the muscular layer, and 3.the mucosa
*The outer serosa is formed by the visceral peritoneum, the middle muscular layer consists of longitudinal and circular smooth muscle cells, and the inner mucosa consists of a mucous membrane of simple ciliated columnar epithelium
*The mucosa is arranged into numerous longitudinal folds
*The mucosa of the _______ provides nutrients for the oocyte or, if fertilization has occurred, for the developing embryo as it passes through the ______
*The ciliated epithelium helps move the small amount of fluid and the oocyte, or the developing embryo, through the ____
Uterine Tubes
86
*Near the ovary, the uterine tube expands to form the ______
*Long, thin processes called fimbriae surround the opening of the ________
*The inner surface of the fimbriae consist of a ciliated mucous membrane
*Movement of the cilia sweeps the secondary oocyte into the uterine tube
Infundibulum
87
*The part of the uterine tube that is nearest the infundibulum is called the ______
*It is the widest and longest part of the tube and accounts for about 7.5-8cm of the total 10cm length of the tube
*Fertilization usually occurs in the _____
Ampulla
88
*The part of the uterine tube nearest the uterus is the ______
*It is much narrower and has thicker walls than the ampulla
Isthmus
89
*Provides protection, nourishment and waste removal for the developing embryo and fetus
*Contraction expel fetus at birth
*Is the size and shape of a medium-sized pear-about 7.5cm long and 5cm wide
*Internally, the uterine cavity continues as the cervical canal, which opens through the ostium into the vagina
*Is supported by 1.the broad ligament, 2.the round ligaments, and 3.the uterosacral ligaments
Uterus
90
*The broad ligament is a peritoneal fold extending from the lateral margins of the _____ to the wall of the pelvis on either side
*It also surrounds and supports the ovaries and the uterine tubes
*The round ligaments extend from the _____ through the inguinal canals to the labia majora of the external genitalia, and the uterosacral ligaments attach the lateral wall of the uterus to the sacrum
*Normally, the _____ is anteverted, meaning that the body of the ____ is tipped slightly anteriorly
*In some females the ______ is retroverted, or tipped posteriorly
*In addition to the ligaments, skeletal muscles of the pelvic floor support the ______ inferiorly
*If these muscles are weakened (e.g. in childbirth), the ______ can extend inferiorly into the vagina, a condition called a prolapsed ______
Uterus
91
Body
Fundus
Cervix
Isthmus
Regions of the Uterus
92
*The main part of the uterus, the _____, is the region between the fundus and the cervix
Body
93
*It is slightly flattened anteroposteriorly and is oriented in the pelvic cavity with the larger, rounded part, the fundus, directed superiorly and the narrower part, the _____, directed inferiorly
Cervix
94
*A slight constriction called the _____ marks the junction of the cervix and the body
Isthmus
95
*The next layer, just deep to the perimetrium, is the ______, or muscular layer, composed of a thick layer of smooth muscle
*The ______ accounts for the bulk of the uterine wall and is the thickest layer of smooth muscle in the body, although the structure is not the same in all areas of the uterus
*In the cervix, the muscular layer contains less muscle and more dense connective tissue
*The cervix is therefore more rigid and less contractile than the rest of the uterus
Myometrium
96
*The innermost layer of the uterus is the ______
*The _______ is a mucous membrane that consists of a simple columnar epithelial lining and a connective tissue layer called the lamina propria
*Simple tubular glands, called spiral glands, are scattered about the lamina propria and open through the epithelium into the uterine cavity
*The _____consists of two layers: 1.the basal layer, and 2.the functional layer
Endometrium
97
*The thin, deep _____ is the deepest part of the lamina propria and is continuous with the myometrium
Basilar Zone
98
*The thicker, superficial ______ consists of most of the lamina propria and the endothelium and lines the uterine cavity itself
*Is so named because it undergoes changes and sloughing during the uterine cycle
*Small spiral arteries of the lamina propria supply blood to the ____ of the endometrium
*These blood vessels play an important role in the cyclic changes of the endometrium
Functional Zone
99
*Or serous layer, is the visceral peritoneum that covers the uterus
Perimetrium
100
*Copulatory organ
*Is the female organ of copulation, receiving the penis during intercourse
*It also allows menstrual flow and childbirth
*Is a tube about 10cm long that extends from the uterus to the outside of the body
*Longitudinal ridges called columns extend the length of the anterior and posterior vaginal walls, and several transverse ridges called rugae extend between the anterior and posterior columns
*The superior, domed part of the _____, the fornix, is attached to the sides of the cervix so that a part of the cervix extends into the _____
*The wall of the ______ consists of an outer muscular layer and an inner mucous membrane
*The muscular layer is smooth muscle that allows the ______ to increase in size to accommodate the penis during intercourse and to stretch greatly during childbirth
Vagina
101
*The mucous membrane is moist, stratified squamous epithelium that forms a protective surface layer
*Lubricating fluid passes through the epithelium into the _____
*During intercourse, increased lubrication is provided by increased fluid released from the vaginal wall as well as secretions from the cervix and glands of the external genitalia
*The hymen is a thin mucous membrane that covers the vaginal opening, or orifice
*Sometimes the hymen completely closed the vaginal opening (a condition called imperforate hymen), and it must be removed to allow menstrual flow
*More commonly, the hymen is perforated by one or several holes
*The openings in the hymen are usually greatly enlarged during the first sexual intercourse
*In addition, the hymen can be perforated earlier in a young female’s life, such as during strenuous physical exercise
*Thus, the absence of an intact hymen is an unreliable indicator of virginity
Vagina
102
Vulva
Vestibule
Labia majora
Labia minora
Clitoris
Female External Genitalia
103
*The female external genitalia are called the _____, or pudendum
*It consists of the vestibule and its surrounding structures
Vulva
104
oIs the space into which the vagina opens posteriorly and the urethra opens anteriorly
oErectile tissue that corresponds to the corpus spongiosum of the male lies deep to and on the lateral margins of the vestibular floor on each side of the vaginal orifice
oEach erectile body is called a bulb of the _____
oLike other erectile tissue, it becomes engorged with blood and is more sensitive during sexual arousal
oExpansion of the bulbs causes narrowing of the vaginal orifice and allows better contact of the vagina with the penis during intercourse
oGlands associated with the _____ secrete a lubricating fluid that prevents drying of the ______
oThe ducts of the greater _____ glands open on each side of the ______, between the vaginal opening and the labia minora
oAdditional small mucous glands, the lesser vestibular glands, or paraurethral glands, are located near the clitoris and urethral opening
Vestibule
105
oLateral to the labia minora are two prominent, rounded folds of skin called the ______
oSubcutaneous adipose tissue is primarily responsible for the prominence of the ____
oThe two _____ unite anteriorly in an elevation over the pubic symphysis called the mons pubis
oThe lateral surfaces of the ______ and the surface of the mons pubis are covered with coarse hair
oThe medial surfaces are covered with numerous sebaceous and sweat glands
oThe space between the _____ is called the pudendal cleft
oMost of the time, the ______ are in contract with each other across the midline, closing the pudendal cleft and concealing the deeper structures within the vestibule
Labia Majora
106
oA pair of thin, longitudinal skin folds called the _______ form a border on each side of the vestibule
Labia Minora
107
oA small, erectile structure called the _____ is located in the anterior margin of the vestibule
oThe _____ is usually less than 2cm in length and consists of a shaft and a distal glans
oWell supplied with sensory receptors, it initiates and intensifies the level of sexual sensation
oThe _____ contains two erectile structures, the corpora cavernosa, each of which expands at the base end of the _____ to form the crus of the ______ and attaches the _____ to the pelvic bones
oThe corpora cavernosa of the _____ are comparable to the corpora cavernosa of the penis, and they become engorged with blood as a result of sexual excitement
oIn most females, this engorgement results in an increase in the diameter, but not the length, of the ______
oWith increased diameter, the ______ makes better contact with the prepuce and surrounding tissues and is more easily stimulated
Clitoris
108
*Are the organs of milk production and are located within the breasts
*Are modified sweat glands
*Externally, the breasts of both males and females have a raised nipple surrounded by a circular, pigmented region called the areola
*The areolae normally have a slightly bumpy surface caused by areolar glands just below the surface
*The areolar glands are actually rudimentary ______
*Secretions from these glands lubricate and protect the nipple and the areola from chafing during nursing
Mammary Gland
109
*Before puberty, the general structure of the breasts is similar in both males and females
*The breasts possess a rudimentary glandular system, which consists mainly of ducts with sparse alveoli
*The female breasts begin to enlarge during puberty, primarily under the influence of estrogen and progesterone
*Increased sensitivity or pain in the breasts often accompanies this enlargement
*Males often experience the same sensations during early puberty, and their breasts can even develop slight swellings; however, these symptoms usually disappear fairly quickly
*On rare occasions, the breasts of a male become enlarged, a condition called gynecomastia
*Each adult female _______ usually consists of 15-20 glandular lobes covered by a considerable amount of adipose tissue
*It is primarily this superficial adipose tissue that gives the breast its form
*The lobes of each ______ form a conical mass, with the nipple located at the apex
Mammary Gland
110
*A group of suspensory ligaments, or Cooper ligaments, support and hold the breasts in place
*These ligaments extend from the fascia over the pectoralis major muscles to the skin over the _______ and prevent the breasts from excessive sagging
*The nipples are very sensitive to tactile stimulation and contain smooth muscle cells that contract, causing the nipple to become erect in response to stimulation
*These smooth muscle cells respond to stimuli such as tough, cold, and sexual arousal
Mammary Gland
111
oEach lobe has a single ______, which opens independently of other lactiferous ducts on the surface of the nipple
oThe _____ supplying a lobe subdivides to form smaller ducts, each of which supplies a lobule
oWithin each lobule, the ducts branch and become even smaller
oIn milk-producing, or lactating, mammary glands, the ends of these small ducts expand to form secretory sacs called alveoli
oMyoepithelial cells surround the alveoli and contract to expel milk
oIn nonlactating mammary glands, only the duct system is present
Lactiferous Duct
112
oJust deep to the surface, each lactiferous duct enlarges to form a small, spindle-shaped ______
oIn lactating females, milk accumulates in the _______ during milk letdown
Lactiferous Sinus
113
28 day cyclical changes, includes events at the ovary and uterus
Menstrual Cycle
114
Is divided into a follicular phase and a luteal phase
*The term____ refers to the regular events that occur in the ovaries of sexually mature, nonpregnant females during the menstrual cycle
*This cycle can be divided into the follicular phase, which occurs before ovulation, and the luteal phase, which occurs after ovulation
*During the follicular phase, a primordial follicle develops into a mature follicle as the primary oocyte within undergoes the first meiotic division
*Given the idealized 28-day cycle, the follicular phase occurs between days 1 and 14
*On day 14, the mature follicle ruptures, releasing the newly formed secondary oocyte
*Following ovulation, the follicle forms the endocrine structure, the corpus luteum
*Ovulation marks the transition to the luteal phase (days 15-28)
*The corpus luteum secretes progesterone and a small amount of estrogen
*If fertilization of the secondary oocyte occurs, the corpus luteum continues to secrete progesterone to maintain pregnancy, particularly in the first trimester, after which the placenta becomes the primary source for progesterone
*If fertilization does not occur, the corpus luteum degenerates to form the corpus albicans
Ovarian Cycle
115
Step 1: Formation of primary follicle
Step 2: Formation of the secondary follicle
Step 3: Formation of the tertiary follicle
Step 4: Ovulation
Step 5: Formation of the corpus luteum
Step 6: Degeneration of the corpus luteum
Ovarian Cycle
116
Changes in structure of the functional zone; 28 days
Menses
Proliferative phase
Ovulation occurs
Secretory phase
Menstrual Cycle (Uterine Cycle)
117
*The first day of menses is considered day 1 of the uterine cycle, and menses typically lasts 4-5 days
*Ovulation occurs on about day 14 of a 28-day ______; however, the timing of ovulation varies from individual to individual and even within a single individual from one ______ to the next
*The time between ovulation (day 14) and the next menses is typically 14 days
*The time between the first day of menses and the day of ovulation is more variable than the time between ovulation and the next menses
*Estrogen causes the endometrial cells and, to a lesser degree, the myometrial cells to divide during the proliferative phase
*It also makes the uterine tissue more sensitive to progesterone by stimulating the synthesis of progesterone receptor molecules within the uterine cells
*After ovulation, during the secretory phase, progesterone from the corpus luteum binds to the progesterone receptors, resulting in cellular hypertrophy in the endometrium and myometrium and causing the endometrial cells to become secretory
Menstrual Cycle (Uterine Cycle)
118
*Estrogen increases the tendency of smooth muscle cells of the uterus to contract in response to stimuli, but progesterone inhibits smooth muscle contractions
*When progesterone levels increase while estrogen levels are low, contractions of the uterine smooth muscle are reduced
*In uterine cycle in which pregnancy does not occur, progesterone and estrogen levels decline to low levels as the corpus luteum degenerates
*The drop in these hormones initiates the beginning of the next uterine cycle, beginning with the next menses
*As a consequence of low progesterone and estrogen levels, the uterine lining begins to degenerate
*The spiral arteries constrict in a rhythmic pattern for longer and longer periods as progesterone levels fall
*As a result, all but the basal parts of the spiral glands become ischemic and then necrotic
*As the cells become necrotic, they slough into the uterine lumen
*The necrotic endometrium, mucous secretions, and a small amount of blood released from the spiral arteries make up the menstrual fluid
*Decreases in progesterone levels and increases in inflammatory substances that stimulate myometrial smooth muscle cells cause uterine contractions, which expel the menstrual fluid from the uterus through the cervix and into the vagina
Menstrual Cycle (Uterine Cycle)
119
*Is a period of mild hemorrhage that occurs approximately once each month, during which the functional layer of the endometrium is sloughed and expelled from the uterus
*Menstruation is the discharge of the sloughed endometrial tissue and blood
Menses
120
*The time between the ending of menses and ovulation is called the _____
*During the ______, the endometrium of the uterus begins to regenerate
*The remaining epithelial cells rapidly divide and replace the cells of the functional layer that were sloughed during the last menses
*A relatively uniform layer of low cuboidal endometrial cells is produced
*The cells later become columnar, and the layer of cells folds to form tubular spiral glands
*Blood vessels called spiral arteries project through the delicate connective tissue that separates the individual spiral glands to supply nutrients to the endometrial cells
Proliferative Phase
121
*The period after ovulation and before the next menses is called the _____ because of the maturation of and secretion by spiral glands
*During the ______, the endometrium becomes thicker, and the spiral glands develop to a greater extent and begin to secrete small amounts of a fluid right in glycogen
*Approximately 7 days after ovulation, or about day 21 of the menstrual cycle, the endometrium is prepared to receive a developing embryonic mass, if fertilization has occurred
*If the developing embryonic mass arrives in the uterus too early or too late, the endometrium does not provide a suitable environment for it
Secretory Phase
122
First menstruation
Menarche
123
Last uterine cycle
*When a female is 40-50 years old, menstrual cycles become less regular, and ovulation does not occur consistently
*Eventually, menstrual cycles stop completely
*The cessation of menstrual cycles is called _______
*The time from the onset of irregular cycles to the complete cessation, which is often 3 to 5 years, is called perimenopause, of the female climacteric
*Is associated with changes in the ovaries
*The number of follicles remaining in the ovaries of menopausal females is small
*In addition, the follicles that remain become less sensitive to stimulation by LH and FSH; therefore, fewer mature follicles and corpora lutea are produced
*Older females experience gradual changes in response to the reduced amount of estrogen and progesterone produced by the ovaries
Menopause
124
*For example, some females experience sudden episodes of uncomfortable sweating (hot flashes), fatigue, anxiety, temporary decreases in sex drive, and occasionally severe emotional disturbances
*Many of these symptoms can be treated successfully with hormone replacement therapy (HRT)
*HRT usually involves administering small amounts of estrogen, or estrogen in combination with progesterone, and then gradually decreasing the treatment over time
*It appears that administering estrogen following _______ also helps prevent osteoporosis and may reduce colorectal cancer
*Although estrogen therapy has been successful, it prolongs the symptoms associated with menopause in many females, and some potential side effects are of concern, including an increased risk for breast, ovarian, and uterine cancer
*In addition, HRT does not reduce the risk for heart disease for the first few years after the beginning of _______
*Some data indicate that the risk for heart attacks, strokes, and blood clots is also increased
Menopause
125
FSH
Estrogens
Hormones of the Follicular Phase
126
*FSH stimulates the granulosa cells to convert androgens to estrogen
*FSH gradually increases LH receptors in the granulosa cells
*FSH levels actually decrease during the follicular phase because developing follicles produce inhibin, which has a negative-feedback effect on FSH secretion
Follicle Stimulating Hormone (FSH)
127
Secreted by the granulosa cells
*Stimulates bone growth and muscle growth
*Maintenances of secondary sexual characteristics
*Affects CNS
*Maintenance of reproductive organs and glands
*Initiates repair and growth of the endometrium
*Produced by the granulosa cells increases LH receptors in the theca interna cells
*______, in turn, increases receptors in both theca internal cells and granulosa cells
*These androgens are also converted to _____ by the granulosa cells
*The production of androgens by the theca interna cells increases, resulting in a gradual increase in _______ secretion by granulosa cells throughout the follicular phase, even though only a small increase in LH secretion occurs
Estrogens
128
LH
Progesterone
Hormones of the Luteal Phase
129
Triggers ovulation
*LH stimulates the theca interna cells to produce androgens, which diffuse from these cells to the granulosa cells
*After LH receptors in the granulosa cells have increased, LH stimulates the granulosa cells to produce progesterone, which diffuses from the granulosa cells to the theca interna cells, where it is converted to androgens
Luteinizing Hormone (LH)
130
Secreted by the corpus luteum
*Prepares the uterus for pregnancy
*Decreases hypothalamic secretion of GnRH which in turn reduces the amount of LH and FSH release by the pituitary
Progesterone
131
Hypothalamic secretion
Anterior pituitary gland secretion
Follicular phase of ovarian cycle begins
Effects of estrogen secretion
LH surge and FSH surge
Ovulation and luteal phase of ovarian cycle begins
Formation of corpus luteum
Negative-feedback effect on progesterone and estrogen secretion
Hormonal Regulation of the Ovarian Cycle
132
Early in the ovarian cycle, the hypothalamus increases release of GnRH
oAdditionally, the anterior pituitary sensitivity to GnRH increases
Hypothalamic Secretion
133
As a result of increased GNRH secretion, the anterior pituitary increases secretion of FSH and LH
Anterior Pituitary Gland Secretion
134
FSH and LH stimulate growth and maturation of ovarian follicles
oFSH is primarily responsible for initiating the development of the primary follicles, and as many as 25 follicles begin to mature during each ovarian cycle
oHowever, normally only 1 is ovulated
oThe follicles that start to develop in response to FSH may not ovulate during the same ovarian cycle in which the begin to mature, but they may ovulate one or two cycles later
oThe remaining follicles degenerate
Follicular Phase of Ovarian Cycle Begins
135
As follicles mature, they begin to secrete estrogens
oEstrogen secretion by the follicle has three major effects: 1.stimulation of uterine endometrial proliferation, 2.positive feedback on hypothalamic and anterior pituitary secretion, and 3.determination of which follicles degenerate
oLarger, more mature follicles appear to secrete estrogen and other substances that have an inhibitory effect on other, less mature follicles
Effects of Estrogen Secretion
136
Estrogen has a positive-feedback effect on the hypothalamus and anterior pituitary, resulting in an increase in secretion of both LH and FSH, often referred to as the _____ and _______
oThe _____ occurs several hours earlier and to a greater degree than the _____, and the _____ can last up to 24 hours
LH Surge and FSH Surge
137
The LH surge stimulates maturation of the follicle, including completion of meiosis I by the primary oocyte
oAlso the LH surge triggers several events that are very much like inflammation in a mature follicle
oThese events result in ovulation, which involves he rupturing of the follicle and the release of the oocyte and corona radiata
Ovulation and Luteal Phase of Ovarian Cycle Begins
138
Shortly after ovulation, the follicle’s production of estrogen decreases and the remaining cells of the follicle differentiate into corpus luteum cells and begin to secrete progesterone and estrogen
oProgesterone and estrogen secretion stimulate further development of the uterine endometrium
Formation of Corpus Luteum
139
The increased progesterone and estrogen levels now have a negative-feedback effect on the hypothalamus and anterior pituitary, resulting in a decrease in FSH and LH secretion
Negative-Feedback Effect of Progesterone and Estrogen Secretion
