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Chapter 28 - The Reproductive System

Terms in this set (83)

- paired oval glands in scrotum
- measures 5cm long, 2.5cm diameter
- each has mass of 10-15 grams

Develop:
- near kidneys
- in posterior part of abdomen
- descend through inguinal canals
- to scrotum (7th month in uterus)

Tunica Vaginalis:
- serous membrane
- derived from peritoneum
- forms during descent of testes
- partially covers testes

Hydrocele:
- collection of serous fluid in tunica vaginalis
- caused by injuries to testes or inflammation of epididymis
- no treatment required

Tunica Albuginea:
- internal to tunica vaginalis
- white fibrous capsule of dense irregular connective tissue
- extends inward, forming septa that divides testes into series of compartment called lobules

Lobules:
- 200-300
- each one contains three tightly coiled seminiferous tubules

Seminiferous Tubules:
- where sperm is produced

Spermatogenesis:
- process by which the seminiferous tubules produce sperm

Spermatogenic Cells:
- part of seminiferous tubules
- sperm-forming cells

Sertoli Cells:
- supports spermatogenesis
- support and protect developing spermatogenic cells in several ways:
1) nourish spermatocytes, spermatids, and sperm
2) phagocytize excess spermatid cytoplasm during development
3) control movements of spermatogenic cells
- and release sperm into lumen of seminiferous tubule
4) produce fluid for sperm transport
5) secrete hormone inhibin
6) regulate effects of testosterone and FSH (follicle-stimulating hormone)

Spermatogonia:
- stem cells
- develop from primordial germ cells that arise from yolk sac and enter testes during 5th week of development
- embryonic testes develop into spermatogonia - remain dormant until puberty - to become sperm

Order of Advancing Maturity of Sperm:
- primary spermatocytes
- secondary spermatocytes
- spermatids
- sperm cells

Sperm Cell: (spermatozoon)
- released into lumen of seminiferous tubule

Sustentacular Cells:
- large Sertoli cells
- embedded among spermatogenic cells in seminiferous tubules
- extend from basement membrane to lumen of tubule

Blood-testis Barrier:
- tight junctions join neighboring Sertoli cells to one another
- internal to basement membrane
- substances pass through Sertoli cells before they reach developing sperm
- prevents immune response against spermatogenic cell's surface antigens - recognized as foreign by immune system

Leydig (Interstitial) Cells:
- in spaces between seminiferous tubules
- clusters of cells that secrete testosterone (most prevalent androgen)

Androgen:
- hormone that promotes development of masculine characteristics
- testosterone promotes mans libido
- takes 65-75 days

Steps:
1) Spermatogonia
Begins with spermatogonia containing:
- diploid number (2n) of chromosomes

Spermatogonia type of stem cells:
- undergo mitosis
- some remain near basement membrane of seminiferous tubule in undifferentiated state to serve as reservoir of cells for future cell division and sperm production
- the rest lose contact with basement membrane - through blood-testes barrier - undergo developmental changes - differentiate into primary spermatocytes

2) Primary Spermatocytes
- diploid (2n) have 46 chromosomes
- replicates DNA
- meiosis begins

Meiosis I: Forms Secondary Spermatocytes
- homologous pairs of chromosomes line up on metaphase plate
- crossing occurs
- meiotic spindle pulls one duplicated chromosome of each pair to an opposite pole of dividing cells
- two cells formed by meiosis I are secondary spermatocytes

3) Secondary Spermatocytes
- 23 chromosomes
- haploid number (n)
- each secondary spermatocyte made up of two chromatids (copies of the DNA) still attached to centromere
- no replication of DNA occurs in secondary spermatocytes

Meiosis II: Forms spermatids (4 haploid cells)
- chromosomes line up in single file along metaphase plate
- two chromatids from each chromosome separate
- four haploid cells resulting from meiosis II are spermatids

4) Spermatids:
- single primary spermatocyte
- produces four spermatids
- via two rounds of cell division (Meiosis I and Meiosis II)

Cytokinesis
- spermatogenic cells proliferate
- but fail to complete cytoplasmic separation
- cells remain in contact via cytoplasmic bridges through entire development
- half sperm contain an X chromosome and half contain a Y chromosome
- larger X chromosome may carry genes for spermatogenesis that are lacking in the Y chromosome

5) Spermiogenesis
- final stage of spermatogenesis
- development of haploid spermatids into sperm
- no cell division occurs
- each spermatid becomes a single sperm cell
- spherical spermatids transform into elongated, slender sperm
- acrosome forms atop nucleus
- flagellum develop
- mitochondria multiply
- Sertoli cells dispose of excess cytoplasm that sloughs off
- Spermiation occurs - sperm release from connections to Sertoli cells
- sperm enter lumen in seminiferous tubule
- fluid secreted by Sertoli cells push sperm along toward ducts of testes (sperm not yet able to swim)
Gonadotropin-releasing hormone (GnRH)
- at puberty hypothalamic cells increase secretion

Stimulates gonadotrophs:
- in anterior pituitary
- to increase secretion of two gonadotropins:
- luteinizing hormone and follicle stimulating hormone

1) Luteinizing Hormone
- stimulates Leydig cells
- located between seminiferous tubules
- to secrete testosterone

Testosterone
- steroid hormone
- synthesized from cholesterol in testes
- principal androgen
- lipid-soluble
- readily diffuses out of Leydig cells into interstitial fluid and then into blood

Via negative feedback Testosteorne:
- suppresses secretion of LH by anterior pituitary gonadotrophs
- suppresses secretion of GnRH by hypothalamic neurosecretory cells

5 alpha-reductase converts:
- testosterone
- to dihydrotestosterone (DHT androgen)
- in external genitalia and prostate
- stimulates final steps of spermatogenesis in seminiferous tubules

2) Follicle Stimulating Hormone
- indirectly stimulates spermatogenesis

FSH and testosterone act synergistically:
- on Sertoli cells
- to stimulate secretion of androgen-binding protein (ABP)
- ABP binds to testosterone - keeps its concentration high

Inhibin
- released by Sertoli cells
- protein hormone

Inhibits FSH secretion by:
- anterior pituitary

Spermatogenesis proceeds too slowly:
- less inhibin is released
- permits FSH to be secreted more
- increasing rate of spermatogenesis

Testosterone and Dihydrotestosterone:
- bind to same androgen receptors
- found within nuclei of target cells
- hormone receptor complex regulates gene expression
- turning some genes on or off

Produce several Effects
1) Prenatal Development:
- before birth
- testosterone stimulates male pattern development of reproductive system ducts and descent of testes
- dihydrotestosterone - stimulates external genitalia.
- testosterone converted to estrogens in brain - may help in developing certain regions of brain in males

2) Development of Male Sexual Characteristics
During puberty:
- testosterone and dihydrotestosterone secreted
- development and enlargement of male sex organs
- and masculine secondary sexual characteristics

Secondary sexual characteristics:
- muscular and skeletal growth
- wide shoulders
- narrow hips
- face and chest hair
- more on other parts
- thickening of skin
- increase in sebaceous gland secretion
- enlargement of larynx
- deeper voice

3) Development of Sexual Function
Androgens contribute to:
- male sexual behavior
- spermatogenesis
- sex drive (male and females)

Adrenal cortex:
- main source of androgens for females

4) Stimulation of Anabolism
Androgens:
- anabolic hormones
- stimulate protein synthesis
- heavier muscle and bone mass in males
- contains urethra
- passageway for semen and urine
- cylindrical shape

Consists of:
- body
- glans penis
- root

Body of Penis
- three cylindrical masses of tissue
- surrounded by tunica albuginea

1) Tunica Albuginea
- surrounds penis
- composed of fibrous tissue

2) Corpora Cavernosa Penis
- two dorsolateral masses

3) Corpus Spongiosum Penis
- smaller, midventral mass
- contains spongy urethra
- keeps spongy urethra open during ejaculation

Skin and Subcutaneous Layer:
- enclose all three penis masses
- consists of erectile tissue

Erectile Tissue:
- composed of numerous blood sinuses (vascular spaces) lined by endothelial cells
- surrounded by smooth muscle and elastic connective tissue

Glans Penis:
- rounded, acorn shaped region
- distal end of corpus spongiosum penis

Corona:
- margin of glans penis

External Urethral Orifice:
- distal, terminal end of urethra
- slitlike opening

Prepuce or Foreskin:
- covering glans penis
- loosely fitting skin

Root of Penis:
- attached portion
- consists of bulb of penis and crura of the penis

1) Bulb of Penis
- expanded posterior continuation of base of corpus spongiosum penis
- attached to inferior surface of deep muscles of perineum
- enclosed by bulbospongiosus muscle (aid ejaculation)

2) Crura of the Penis
- two separated and tapered portions of corpora cavernosa penis
- bends laterally away from bulb of penis to attach to ischial and inferior pubic rami
- surrounded by ischiocavernosus muscle

Two Ligaments:
- continuous with fascia of penis
1) Fundiform Ligament
- arises from inferior part of linea alba
2) Suspensory Ligament of Penis
- pubic symphysis

Erection:
- enlargement or stiffening of penis
- occurs upon arousal or stimulation (visual, tactile, auditory, olfactory, or imagined)
- parasympathetic fibers from sacral portion of spinal cord initiate erection
- nitric oxide causes smooth muscle in walls of arterioles supplying erectile tissue to relax, causing vasodilation of these arterioles and causes widening of blood sinuses
- caused by increased blood flow and widening of blood sinuses - maintained by compression of veins from blood sinuses

Priapism:
- persistent and painful erection
- not involving sexual arousal or excitement
- lasts several hours
- pain, tenderness
- from abnormalities of blood vessels and nerves - usually in response to medication used for erectile dysfunction
- other causes: spinal cord disorder, leukemia, sickle-cell disease, pelvic tumor

Ejaculation:
- powerful release of semen from urethra to exterior
- sympathetic reflex controlled by lumbar portion of spinal cord - smooth muscle sphincter at base of urinary bladder closes
- peristaltic contractions in epididymis, ductus (vas) deferens, seminal vesicles, ejaculatory ducts, prostate propel semen into penile portion of urethra (spongy urethra)
- bulbospongiosus, ischiocavernosus, superficial transvere perineus muscles contract - supplied by pudendal nerve

Emission:
- discharge of small volume of semen before ejaculation
- may occur during sleep

Sexual Stimulation Ended:
- arterioles supplying erectile tissue of penis constrict
- smooth muscle within erectile tissue contracts
- blood sinuses become smaller
- pressure is relieved on veins of penis - blood can drain through them
- penis becomes flaccid
Oogenesis:
- formation of gametes in ovaries
- begins in females before even born

1) Oogenia:
- germ cells that have migrated from yolk sac to the ovaries
- diploid 2n stem cells
- divide mitotically to produce millions of germ cells

Atresia:
- degeneration of germ cells

2) Primary Oocytes:
- enter prophase of meiosis I during fetal development
- do not complete phase until after puberty
- surrounded by a single layer of flat follicular cells
- 200,000-2,000,000 primary oocytes at birth in each ovary
- 40,000 are present at puberty
- 400 will mature and ovulate during life time
- remainder of oocytes undergo atresia

3) Primordial Follicle
- structure of primary oocytes surrounded by single layer of flat follicular cells
- ovarian cortex surrounding primordial follicle has collagen fibers and fibroblast-like stromal cells

FSH and LH:
- gonadotropins (FSH and LH)
- secreted by anterior pituitary
- stimulate development of primordial follicles

4) Primary Follicles
- develop from primordial follicles
- reach maturity needed for ovulation
Consists Of:
- primary oocyte
- surrounded by granulosa cells

Granulosa Cells:
- outermost rest on basement membrane
- later stage development of layers of cuboidal and low-columnar cells

Zona Pellucida:
- as primary follicles grow
- form clear glycoprotein layer
- between primary oocyte and granulosa cells

Theca Folliculi:
- organized layer of stromal cells
- surrounding basement membrane

5) Secondary Follicle
- primary follicle
- develops into secondary follicle

Two Layers:
a) Theca Interna:
- highly vascularized internal layer of cuboidal secretory cells
- secrete estrogens

b) Theca Externa:
- outer layer of stromal cells and collagen fibers

Granulosa Cells:
- begin to secrete follicular fluid
- builds up in the antrum (cavity in center of follicle)
- inner layer attached to zona pellucida (now called corona radiata)

6) Mature (graffian) Follicle
- secondary follicle matures into mature (graffian) follicle
- just before ovulation a diploid primary cell is present inside

Diploid primary cell completes:
- meiosis I
- producing two haploid (n) cells
- unequal size
- producing 23 chromosomes each

First Polar Body: Packet of discarded nuclear material
- smaller cell
- produced by meiosis I of diploid primary cell

Secondary Oocyte:
- larger cell
- has most of cytoplasm
- begins meiosis II
- stops in metaphase

Ovulation:
- mature (graafian) follicle ruptures
- releases secondary oocyte into pelvic cavity with first polar body and corona radiata (clear glycoprotein layer)
- cells swept into uterine tube
- if fertilization does not occur - cells degenerate
- fertilization occurs - meiosis II begins

Meiosis II:
- secondary oocyte splits into two cells of unequal size

Ovum
- larger cell
- mature egg

If first polar body undergoes cell division:
- two polar bodies formed

Primary oocyte gives rise to:
- 3 haploid polar bodies
- all degenerate
- and a single haploid ovum

Second Polar Body
- second smaller cell

Diploid Zygote:
- sperm cell and ovum unite forming diploid zygote

* one primary oocyte gives rise to single gamete (an ovum)
Uterine (Fallopian) Tubes: Oviducts
- two
- extend laterally from uterus
- 10 cm long tubes, lie within folds of broad ligament in uterus

Provide:
- route for sperm to reach ovum
- transport secondary oocytes and fertilized ova from ovaries to uterus

Each infundibulum:
- extends medially and inferiorly
- to attach to superior lateral angle of uterus

Movement of Oocyte or Ovum to Uterus by:
- Peristaltic contractions of muscularis
- ciliary action of mucosa

Sperm meets and fertilizes secondary oocyte in:
- ampulla of uterine tube
- sometimes fertilization occurs in peritoneal cavity

Infundibulum:
- funnel portion of tube
- close to ovary
- open to pelvic cavity

Fimbriae:
- fringe of fingerlike projections on end of infundibulum
- attached to lateral end of each ovary

Ampulla:
- widest, longest portion

Isthmus:
- thick walled, medial, short, narrow portion that joins the uterus

Currents:
- produced by movements of fimbriae (surround surface of mature follicle just before ovulation)
- sweep ovulated secondary oocyte from peritoneal cavity to uterine tube

Three Histological Layers:
1) Mucosa:
- epithelium
- lamina propria (areaolar connective tissue)

Epithelium
Ciliated simple columnar cells:
- cilia conveyor belt
- help move fertilized ovum

Non ciliated peg cells:
- have microvilli
- secrete fluid that nourishes ovum

2) Muscularis:
- middle layer
- inner, thick, circular ring of smooth muscle
- outer, thin region of longitudinal smooth muscle

3) Serosa
- outer layer

Fertilization
- occur up to 24 hours after ovulation
- after ferilization nuclear materials from haploid ovum and sperm unite
- unfertilized secondary oocyte disintegrate

Zygote
- diploid fertilized ovum
- begins cell divisions while moving toward uterus
- arrives 6-7 days after ovulation
Location:
- between urinary bladder and rectum
Shape:
- inverted pear shape
Size:
- never pregnant: 7.5 cm long, 5 cm wide, 2.5 cm thick
- larger in woman pregnant before
- atrophied (menopause)

Anatomical Subdivisions:
1) Fundus:
- dome-shaped portion superior to uterine tubes
2) Body:
- tapered central portion
3) Cervix:
- inferior narrow portion
- opens into vagina

Isthmus
- between body of uterus and cervix
- constricted region 1cm long

Uterine Cavity:
- interior of body of uterus

Cervical Canal:
- interior of cervix

Internal Os:
- cervical canal opens into uterine cavity here

External Os:
- cervical canal opens into the vagina here

Position of Uterus
Anteflexion:
- normal position of pelvis
- projects superiorly and anteriorly over urinary bladder

Retroflexion:
- posterior tilting of pelvis
- malposition of uterus
- harmless variation of a normal position of uterus
- may occur after childbirth

Position of Cervix
- cervix projects inferiorly and posteriorly to enter wall of vagina at near right angle

Ligaments
- maintain anteflexed position of uterus
- allow uterine body to move which may cause malpositioning of uterus

Broad Ligaments:
- double folds of peritoneum
- attaches uterus to either side of pelvic cavity

Uterosacral Ligaments:
- paired
- peritoneal extensions
- on either side of rectum
- attach uterus to sacrum

Cardinal (Lateral Cervical) Ligaments:
- inferior to bases of broad ligaments
- extend from pelvic wall to cervix and vagina

Round Ligaments
- bands of fibrous connective tissue
- between layers of broad ligament

Extend from:
- point on uterus inferior
- to uterine tubes
- to portion of labia majora of external genitalia
Three Layers of Tissue
- perimetrium
- myometrium
- endometrium

1) Perimetrium:
- outer layer
- serosa
- part of visceral peritoneum
- simple squamous epithelium
- areolar connective tissue
- becomes broad ligament laterally
- anteriorly covers urinary bladder

Vesicouterine Pouch (pouch of Douglas):
- shallow pouch formed by perimetrium
- most inferior point of uterus

2) Myometrium
- middle layer of uterus
- three layers of smooth muscle fibers
- thickest in fundus
- thinnest in cervix

Thicker Layer:
- circular
Inner Layer and Outer Layers:
- longitudinal or oblique

Oxytocin:
- help expel fetus from uterus by contracting uterus
- released from anterior pituitary

3) Endometrium
- inner layer
- three components

a) Innermost Layer:
- simple columnar epithelium
- ciliated and secretory cells line lumen

b) Underlying Endometrial Stroma:
- very thick region of lamina propria (areolar connective tissue)

c) Endometrial (uterine) Glands
- develop as invaginations of luminal epithelium
- extend almost to myometrium

Two Layers:
1) Stratum Functionalis:
- functional layer
- lines uterine cavity
- sloughs off during menstruation

2) Stratum Basalis:
- deeper layer
- is permanent
- gives rise to new stratum functionalis after each menstruation

Blood Supply
- essential for regrowth of stratum functionalis after menstruation
- implantation of fertilized ovum
- development of placenta

Uterine Arteries (internal iliac artery):
- supplies blood to uterus

Arcuate Arteries:
- branches of uterine arteries
- arranged in circular fashion in myometrium

Radial Arteries:
- branches of arcuate arteries
- penetrate deeply into myometrium

Straight Arterioles:
- just before radial arteries reach endometrium they branch into straight arterioles and spiral arterioles
- supply stratum basalis with materials needed to regenerate the stratum functionalis

Spiral Arterioles:
- just before the radial arteries reach endometrium they branch into straight arterioles and spiral arterioles
- supply stratum functionalis
- change a lot during menstrual cycle

Uterine Veins:
- drains blood from uterus into internal iliac veins
VAGINA
- tubular
- 10 cm long
- fibromuscular canal lined with mucous membrane
- extends from exterior of body to uterine cervix
- receptacle for penis during sex, outlet of menstrual flow, passage for childbirth

Location:
- between urinary bladder and rectum
- directed superiorly and posteriorly - where it attaches to uterus

Fornix:
- recess
- surrounds vaginal attachment to cervix
- where contraceptive diaphragm rests - covers cervix

Layers
1) Mucosa
- continuous with uterus
- non keratinized stratified squamous epithelium
- large stores of glycogen (decomposition of organic acids)
- acidic environment inhibits microbial growth
- acidic environment harsh on sperm
- sperm alkalinity from seminal vesicles raises pH in vagina - making a more hospitable environment for sperm

Rugae:
- areolar connective tissue folds

Dendritic cells:
- antigen-presenting cells
- can participate in transmission of AIDS

2) Muscularis
- outer circular layer
- inner longitudinal layer
- smooth muscle
- stretch to accommodate penis during sex and child birth

3) Adventitia
- superficial layer of vagina
- areolar connective tissue
- anchors vagina to urinary bladder anteriorly and rectum and anal canal posteriorly

Hymen:
- vascularized mucous membrane
- forms border and partially closes inferior end of vaginal opening to exterior
- ruptures after first sex encounter - remnants remain

Imperforate Hymen:
- completely covers vaginal orifice
- surgery may be needed to open orifice to allow discharge of menstrual flow

Vaginal Orifice:
- opening to exterior
- partially covered by hymen
Vulva or Pudendum
- external genitals

Components

1) Mons Pubis:
- anterior to vaginal and urethral openings
- elevation of adipose tissue by skin and coarse hair
- cushions pubic symphysis

2) Labia Majora: labium majus (singular term)
- two longitudinal folds
- extend inferiorly and posteriorly
- covered by pubic hair
- contain a lot of adipose tissue
- sebaceous glands
- apocrine sudoriferous glands
- homologous to scrotum (came from same tissue)

3) Labia Minora: labium minus (singular term)
- two smaller folds of skin
- no pubic hair and adipose tissue
- have few sudoriferous glands
- contain sebaceous glands
- homologous to spongy (penile) urethra

4) Clitoris
- small cylindrical mass
- homologous with glans penis in males
- capable of enlargement on tactile stimulation
- role in sexual excitement
- composed of two erectile bodies:
a) corpora cavernosa
b) numerous nerves and blood vessels

Location:
- anterior junction of labia minora

Prepuce of the Clitoris:
- layer of skin
- formed at point where labia minora unite
- covers body of clitoris

Glans Clitoris:
- exposed portion of clitoris

5) Vestibule
- region between labia minora
- homologous to membranous urethra in males

Within Vestibule:
- hymen (if still present)
- vaginal orifice
- external urethral orifice
- openings of ducts of several glands

Vaginal Orifice:
- opening of vagina to exterior
- occupies large part of vestibule
- bordered by hymen

External Urethral Orifice:
- opening of urethra to exterior
- anterior to vaginal orifice
- posterior to clitoris

Glands
a) Paraurethral Glands (Skene's Glands)
- either side of external urethral orifice
- mucus-secreting glands
- embedded in wall of urethra
- homologous to prostate

b) Greater Vestibular (Bartholin's) Glands:
- either side of urethral orifice
- open by ducts into a groove between the hymen and labia minora
- secrete mucus during arousal and intercourse
- adds to cervical mucus
- provides lubrication
- homologous to bulbourethral glands in males

6) Bulb of the Vestibule:
- two elongated masses of erectile tissue
- deep to labia on either side of vaginal orifice
- becomes engorged with blood during arousal
- narrows vaginal orifice
- places pressure on penis during intercourse
- homologous to corpus spongiosum and bulb of penis
Gonadoptropin-releasing hormone (GnRH):
- released by hypothalamus
- controls ovarian and uterine cycles
- stimulates release of FSH and LH from anterior pituitary

Follicle-stimulating Hormone (FSH):
- stimulated by GnRH
- released by anterior pituitary
- initiates follicular growth
- stimulate ovarian follicles to secrete estrogens
- influences androgens to be taken up by granulosa cells of the follicle and be converted to estrogens

Luteinizing Hormone (LH):
- stimulated by GnRH
- released by anterior pituitary
- stimulates development of ovarian follicles
- stimulate ovarian follicles to secrete estrogens
- stimulates theca cells of developing follicle to produce androgens
- midcycle triggers ovulation and promotes formation of corpus luteum (reason for name luteinizing hormone)

Corpus Luteum:
- formation triggered by LH
Stimulation of LH triggers - corpus luteum secretes estrogens, progesterone, relaxin, inhibin

Six Different Estrogens
- isolated from human female plasma

Three present in significant quantities:
beta (b)-estradiol:
- most common in non pregnant woman
- synthesized from cholesterol in ovaries
estrone
estriol

Estrogens
- secreted by ovarian follicles

Functions:
- promote development and maintenance of female reproductive structures, secondary sex characteristics, breasts
- increase protein anabolism, including building of strong bones
- estrogens are synergistic with human growth hormone
- lower blood cholesterol (women age 50 and up - high risk of coronary artery disease)
- moderate levels of estrogen in blood inhibits release of both GnRH by hypothalamus and secretion of LH and FSH in anterior pituitary

Secondary Sex Characteristics include:
- distribution of adipose tissue in breasts, abdomen, mons pubis, hips
- voice pitch
- broad pelvis
- pattern of hair growth on head and body

Progesterone:
- secreted mainly by cells of corpus luteum
- with estrogens, prepares and maintains endometrium for implantation of fertilized ovum
- prepare mammary glands for milk secretion
- high levels inhibit release of GnRH and LH

Relaxin:
- produced by corpus luteum during month cycle
- relaxes uterus by inhibiting contractions of myometrium
- placenta secretes relaxin during pregnancy - relaxes uterine smooth muscle
- end of pregnancy increases flexibility of pubic symphysis
- help dilate cervix for delivery of baby

Inhibin:
- secreted by granulosa cells in growing follicles
- secreted by corpus luteum during ovulation
- inhibits secretion of FSH and lesser extent LH
Duration:
- 24 - 36 days
- duration for discussion in book is 28 days

MENSTRUAL CYCLE

Menstrual Phase (Menstruation):
- 5 days in cycle

Events in Ovaries:
- under FSH influence
- several primordial follicles develop into primary follicles - to secondary follicles
- takes several months to occur
- follicle that begins at beginning of one menstrual cycle may not be fully developed until a couple cycles later

Events in Uterus:
- 50-150 mL of menstrual blood, tissue fluid, mucus, epithelial cells shed from endometrium
- due to declining levels of progesterone and estrogens - stimulate release of prostoglandins cause uterine spiral arterioles to contract
- cells supplied by uterine spiral arterioles die
- stratum functionalis sloughs off
- endometrium very thin - 2-5 mm
- only stratum basalis remains
- menstrual flow passes from uterine cavity - cervix - vagina - exterior

PREOVULATORY PHASE
- time between end of menstruation and ovulation
- variable in length
- 6-13 days in 28 day cycle

Events in Ovaries:
- secretion of estrogens and inhibin by secondary follicles in ovaries
- day 6 single secondary follicle in one (out of two) ovaries has become dominant follicle

Dominant Follicle:
- secretes estrogens and FSH causing other well-developed follicles to stop growing and undergo atresia

Fraternal (non-identical) Twins:
- result from 2-3 secondary follicles becoming codominant
- secondary follicles are ovulated and fertilized at same time

Mature (graafian) Follicle:
- dominant secondary follicle continues to enlarge until more than 20 mm in diameter - ready for ovulation
- forms blisterlike bulge due to swelling of antrum on surface of ovary
- final maturation process - mature follicle increases productions of estrogens

Follicular Phase:
- menstrual and preovulatory phases

Events in Uterus:
- estrogens in blood stimulate repair of endometrium
- cells of stratum basalis undergo mitosis and produce new stratum functionalis
- short, straight endometrial glands develop from thickening of endometrium
- arterioles coil and lengthen to penetrate stratum functionalis
- thickness of endometrium doubles to 4-10 mm

Proliferative Phase:
- term for preovulatory phase in uterine cycle
- endometrium is proliferating

OVULATION
- rupture of a mature (graafian) follicle
- release of secondary oocyte into pelvic cavity
- occurs on day 14 in 28 day cycle
- secondary oocyte surrounded by zona pellucida and corona radiata

Positive Feedback Effect
- high levels of estrogens effect cells that secrete LH and GnRH
- cause ovulation in following ways

1) high concentration of estrogens
- stimulates frequent release of GnRH from hypothalamus
- directly stimulates gonadotrophs in anterior pituitary to secrete LH

2) GnRH promote release of
- FSH and LH
- by anterior pituitary

3) LH causes rupture of
- mature (graafian) follicle
- and expulsion of secondary oocyte
- 9 hours after peak of LH surge
- ovulated oocyte and corona radiate swept away in uterine tube

Mittelschmerz:
- pain and blood associated with ruptured follicle

POSTOVULATORY PHASE
- time between ovulation and onset or next menses
- lasts for 14 days in 28 day cycle (15-28)

Events in One Ovary:
- after ovulation, mature follicle collapses
- basement membrane between graulosa cells and theca interna break down
- ruptured follicle becomes corpus hemmorhagicum after minor bleeding from ruptured follicle
- theca interna cells mix with granulosa cells
- become corpus luteum under LH influence
- LH stimulates corpus luteum to secrete progesterone, estrogen, relaxin, inhibin
- luteal cells absorb blood clot
- ovarian cycle called luteal phase

Non Fertilized Secondary Oocyte:
Corpus Luteum:
- breaks down after 2 weeks
- secretory activity declines
- degenerates into corpus albicans
- progesterone, estrogen levels decline
- release of GnRH, LH and FSH rise due to loss of negative feedback by ovarian hormones

Fertilized Secondary Oocyte:
- secondary oocyte begins to divide
- corpus luteum is maintained

Human Chorionic Gonadotropin Hormone (hCG):
- maintains corpus luteum
- produced by chorion of embryo 8 days after fertilization
- stimulates secretory activity of corpus luteum
- in maternal blood or urine - indicator of pregnancy
- detected in home pregnancy tests

Events in Uterus:
Progesterone and estrogens produced by corpus luteum promote:
- growth and coiling of endometrial glands
- vascularization of superficial endometrium
- thickening of endometrium 12-18 mm

Endometrial Glands:
- high secretory activity
- secrete glycogen

Secretory Phase:
- begins at time of secretion of glycogen by endometrial glands
- peak at 1 week after ovulation
- fertilized ovum might arrive at uterus

Non Fertilization:
- levels of progesterone and estrogens decline - due to degeneration of corpus luteum
- withdrawal of progesterone and estrogens causes menstruation
Hormones from the anterior pituitary regulate ovarian function, and hormones from the ovaries regulate changes in endometrial lining of uterus.

Hypothalamus:
- releases gonadotropin releasing hormone

Anterior Pituitary:
- releases FSH and LH
- receives stimulation from hypothalamus and GnRH

Ovary:
- FSH and LH regulate changes in endometrial lining and maturation of follicles

1) Growth of primary and secondary follicles
2) Maturation of one dominant follicle
3) Ovulation
4) Formation of corpus luteum
5) Formation of corpus albicans

Ovarian Hormones
1) growth of primary and secondary follicles and maturation of one dominant follicle
- increases secretion of estrogens and inhibin by granulosa cells

Inhibin inhibits release of:
- LH and FSH by anterior pituitary

Estrogens inhibits secretion of:
- GnRH by hypothalamus
- FSH, LH by anterior pituitary

Formation of Corpus Luteum:
- increased secretion of progesterone and estrogens by cells of corpus luteum
- increased secretion of inhibin by cells of corpus luteum
- inhibin inhibits release of LH and FSH by anterior pituitary

Formation of Corpus Albicans:
- no secretion of progesterone and estrogens by corpus albicans
- low levels of progesterone and estrogens promote secretion of GnRH by hypothalamus, and FSH, LH from anterior pituitary

Uterus:
1) Increasing secretion of estrogens and inhibin by granulosa cells
- leads to repair and proliferation of endometrium

2) Increased secretion of progesterone and estrogens by cells of corpus luteum
- leads to preparation of endometrium for arrival of fertilized ovum

3) No secretion of progesterone and estrogens by corpus albicans
- leads to menstruation
Oral Contraceptives:
- hormones designed to prevent pregnancy

Combined Oral Contraceptives:
- contain both progestin (hormone with actions similar to progesterone) and estrogens
- inhibit ovulation by suppressing gonadotropins FSH and LH
- low levels of FSH and LH prevent development of dominant follicle in ovary
- estrogen levels do not rise
- no midcycle LH surge
- no ovulation
- block implantation in uterus and inhibit transport of ova and sperm to uterine tubes

Progestin:
- thickens cervical mucus
- more difficult for sperm to enter uterus
- do not consistently inhibit ovulation

Benefits:
- regulation of length of menstrual cycle
- decreased menstrual flow
- protection against endometrial and ovarian cancers
- lowers risk of endometriosis

Risks: check history of
- blood clotting disorders
- cerebral blood vessel damage
- migraine headaches
- hypertension
- liver malfunction
- heart disease
- smokers face higher risk of stroke or heart attack

Types:
1) Combined Pill:
- both progestin and estrogens
- take once daily x three weeks
- prevent pregnancy and regulate menstrual cycle
- take during fourth week are not active pills

2) Seasonale:
- both progestin and estrogens
- taken once a day in three month cycles of 12 weeks of hormones and 1 week inactive pills
- menstruation during week 13

3) Minipill:
- progestin only
- taken every day of month

Non-Oral:
1) Contraceptive Skin Patch (Ortho Evra):
- contains progestin and estrogens
- in a skin patch placed on skin (buttock, upper arm, lower abdomen, back)
- placed once a week
- after 1 week patch is removed from one location - placed in new location
- 4th week no patch

2) Vaginal Contraceptive Ring (NuvaRing):
- flexible
- doughnut shape ring
- 5cm diameter
- contains estrogens and progesterone
- inserted by female into vagina
- 3 weeks to prevent conception
- removed one week to permit menstruation

3) Emergency Contraception (EC) (morning after pill):
- progestin and estrogens or progestin along
- high levels of progestin and estrogens in EC pills inhibit FSH and LH secretion
- cease secretion of estrogens and progesterone
- uterus shed uterine lining
- implantation is blocked
- one pill within 72 hours
- second pill again in 12 hours

4) Hormone Injections (Depo-provera):
- injectable progestin
- given intramuscularly by M.D once every three months