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Final Exam Review – Urinary & Reproductive Systems

Functions: Homeostatic regulation of the volume and composition of the body fluids:

1. filters the plasma2. eliminates water soluble wastes, especially nitrogenous wastes

such as ammonia, urea,(ammonia and urea come from amino acids) uric acid (comes from DNA & RNA)

3. reabsorbs useful substances into the blood4. excretion of water soluble metabolic wastes, toxins, drugs, salts,

electrolytes and water

Regulates:

1. water and electrolyte balance within body fluid compartments2. pH of the blood3. solute concentration and water volume of the body fluids4. erythrocyte production by releasing erythropoietin5. blood pressure by the release of rennin

Detoxification of free radicals and drugs (works with liver in this function).

Kidney 1. location – posterior wall of abdominal cavity, between T12-L3, it is retroperitoneal.

2. anatomy of the Kidney :a. hilum – area of kidney where the renal artery, renal vein,

ureter, nerves, and lymphatics enter or exit the kidney.b. renal pelvis – region of kidney that receives urine from the

major calyces and carries the urine to the ureter.c. major and minor calycesd. renal papillae. capsule

Internal anatomy of the kidney:a. renal medulla: composed of the renal pyramidsb. renal cortex: outer area of kidney and the renal columns

3. Renal Blood Vessels: a. Renal arteries – branches of the abdominal aorta. The

kidneys at rest receive 15-30% of the cardiac output.b. Renal veins – carry blood back to inferior vena cava after it

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has been filtered by the kidney.c. Afferent arterioles – carry blood to the glomerulus where

the filtration occurs.d. Efferent arterioles – carry blood away from the glomerulus.e. Peritubular capillaries – surround the convoluted tubules

and reabsorb and secrete substances into or out of the filtrate.f. Vasa recta – carry blood into the medulla. These vessels

follow the nephron loop (loop of Henle). These vessels are important in producing concentration gradients between interstitial fluid

Nephron this is the functional unit of the kidneyEach kidney contains about one million nephrons.Nephrons function to remove wastes and to regulate concentrations of water and electrolytes of the filtered blood.

Blood Flow Thru the Kidney:

Blood Flow Thru the KidneyContinued:

Renal Artery ---> segmental artery ---> interlobar artery ---> arculate artery ---> interlobular artery ---> afferent arteriole ---> glomerulus (filtration of the plasma occurs here) ---> efferent arteriole ---> peritubular capillaries ---> vasa recta ---> interlobular veins ---> arcuate veins ---> interlobar veins ---> renal vein ---> inferior vena cava

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Pathway of Filtrate Through the Nephron, Kidney & Urinary System:

glomerulus (filtration occurs here) Bowman’s (glomerular) capsule proximal convoluted tubule descending limb of nephron loop (Loop of Henle) ascending limb of loop of Henle distal convoluted tubule (DCT), numerous DCTs combine to form collecting ducts that travel through renal pyramids and empty through pores in the renal papillae minor calyx major calyx renal pelvis ureter ureter urinary bladder internal urethral sphincter external urethral sphincter urethra exterior of the body

Ureter Muscular tube which carries urine from renal pelvis to urinary bladder.

At entrance to bladder a valve prevents backflow of urine from the bladder to the ureter and kidney.

Actively moves urine by peristaltic contractions.

Urinary Bladder Muscular organ for the storage of urine. lined with transitional epithelium (cells look round when

empty but flatten out when bladder fills and stretches) muscular wall is composed of smooth muscle that is called the

detrusor muscle parasympathetic nervous system stimulates contraction of

detrusor muscle of the bladder and relaxation of internal urethral sphincter

the external urethral sphincter is skeletal muscle and is under voluntary control

Urethra tube which carries urine from the urinary bladder to the outside of the body

Micturiton urinationA. As the bladder fills, stretch receptors are stimulated causing

discomfort.B. When you decide to urinate, sacral parasympathetic fibers

stimulate the following:1) detrusor muscle to contract.2) the internal urethral sphincter relaxes

C. External urethral sphincter is a skeletal muscle and therefore is under voluntary conscious control. When it is relaxed, urination occurs.

URINE FORMATION

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Glomerular Filtration: this is the first step in urine formation.Water and dissolved substances filter out of the glomerular capillaries (which are very permeable) into Bowman’s (glomerular) capsule producing the filtrate.

1. the glomerular blood pressure forces fluid out of the leaky capillaries of the glomerulus, while the osmotic pressure exerted by the plasma proteins pulls fluid into the glomerulus from the Bowman’s capsule.The glomerular filtration pressure is the net of these two opposing pressures.

2. filtrate consists of water and dissolved particles very similar to plasma with the exception of proteins, molecules, and cells that are too large to pass through the glomerulus into Bowman’s capsule.

3. filtration rate is directly proportional to filtration pressure (BP)

4. glomerular filtration rate (GFR) – the amount of filtrate formed in the kidneys per minute—normally about 125 ml/minute (this amounts to 180 liters /day!)

Regulation of GFR

Regulation of GFR (continued)

Two Mechanisms:1. Renal Autoregulation – kidneys respond to a decrease in

glomerular filtration (low blood pressure) in the following way:

a. a decrease in Na+ (Cl-) is perceived by macula densa (specialized epithelial cells in the wall of the distal

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convoluted tubule).b. the macula densa signals smooth muscle in afferent

arteriole to relax.c. dilation of afferent arteriole occurs.d. increased blood flow into glomerulus.e. increased GFR results.

2. macula densa signals juxtaglomerular cells (in afferent arteriole) to secrete an enzyme called renin into the plasma.

a. renin converts angiotensinogen to angiotensin I.b. angiotensin I is converted into angiotensin II by

angiotensin converting enzyme (ACE) in the plasma and in the endothelium of the lungs (pulmonary circulation).

c. angiotensin II causes:i. vasoconstriction of efferent arteriole (raises

systemic blood pressure)ii. aldosterone release from the adrenal cortex

which causes:1. increased reabsorption of Na+ from distal

convoluted tubules and collecting ducts.2. H2O follows by osmosis (need ADH)3. increased blood volume4. increased blood pressure

iii. increased thirst, increasing fluid intakeiv. release of ADH (antidiuretic hormone) from

posterior pituitary increased water reabsorption from the distal convoluted tubules and collecting ducts

v. all the above result in an increase blood pressure which increases the glomerular filtration pressure and increases GFR.

Renin-Angiotensin-Aldosterone

Angiotensinogen renin > angiotensin I angiotensin converting enzyme > angiotensin II aldosterone release from adrenal cortex increased

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Mechanism: Na+ reabsorption from distal convoluted tubules

Tubular Reabsorption there are many substances that are present in the glomerular filtrate but are either absent or in a much lower concentration in the urine; therefore they must have been reabsorbed into the blood.

Important reabsorbed substances:

1. glucose is reabsorbed in the proximal convoluted tubule by active transport.

Carrier molecules are necessary for glucose transport.

With normal blood glucose levels, usually all the filtered glucose is reabsorbed.

Tubular maximum (T-max) - the maximum amount of a substance that can be transported by the nephron.

Clinical Application:

If T-max for glucose (or any transported substance) is exceeded, then the substance will appear in the urine.

in diabetes mellitus there is a large increase in blood glucose concentration

therefore the concentration of glucose I the glomerular filtrate is increased

when glucose concentration exceeds T-max, glucose appears in the urine

glucose in the urine is called glucosuria. This indicates diabetes.

2. ATP is required since this is an active transport process. This process uses 5% of our total resting energy expenditure!!!

3. There are different symporters for glucose, amino acids, and other metabolites. Each transporter has a maximum rate at which it can reabsorb. This is called the tubular maximum (T-max).

The renal threshold is the plasma concentration of a substance at which it begins to appear in the urine.

4. By the end of the proximal convoluted tubule the following

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have been reabsorbed: 100% of filtered nutrients 80-90% of HCO3

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65% of Na+ and H2O 50% of Cl- and K+ have been reabsorbed.

5. water is reabsorbed by osmosis. water reabsorption is associated with the reabsorption of

sodium and other electrolytes (most of which occurs in the PCT).

as H2O leaves the filtrate, the filtrate becomes more concentrated. This creates a concentration gradient for K+, Cl-, HCO3

- and urea. These substances are reabsorbed by diffusion.

water that enters the distal convoluted tubule and collecting duct is reabsorbed only if ADH is present .

6. electrolytes – negatively charged electrolytes like HCO3-, PO4

-, and Cl- move with Na+ because of opposite charges (electrochemical attraction).

7. amino acids are reabsorbed in proximal convoluted tubule

Tubular Secretion is occurring when a substance that is not present in glomerular filtrate, but is found in the urine. This is a process in which substances are transported from the plasma of the peritubular capillaries into the renal tubules.

Regulation of Urine Concentration & Volume:

1. antidiuretic hormone (ADH) is released by the pituitary gland in response to an increase in the tonicity of the blood.

The feedback mechanism of blood is hypertonic and works as follows:a. an increased tonicity is perceived by neurons in the

hypothalamus.b. ADH is released by the posterior pituitary into blood and

reaches kidney.c. ADH increases the permeability of the distal convoluted

tubules and collecting ducts that are normally impermeable to water, and water moves rapidly from the tubules into the blood, decreasing urine volume and increasing the tonicity of the urine.

d. the body retains water preventing dehydration and maintaining blood pressure.

2. If the blood has too much water (hypotonic) then the opposite

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occurs:1. ADH secretion decreases2. distal convoluted tubules and collecting ducts are

impermeable to water3. there is an increased volume of hypotonic urine4. excess water is urinated, blood volume decreases.

Urine Composition: varies greatly with temperature, humidity, diet, activity, water consumption.

1. urine is usually about 95% water2. important wastes that need to be removed from the body

include urea, ammonia, uric acid3. electrolytes that are founded in the urine: H+, Na+, K+, H+4. volume of urine also varies with fluid intake; sweating, etc.

amount is usually between 0.6-2.5 liters/day.

Renal control of pH: A. In proximal convoluted tubules, the response the decreased pH is as follows:1. CO2 diffuses from peritubular capillaries into the cells of the

proximal convoluted tubule2. CO2 + H2O carbonic anhydrase > H2CO3 H+ + HCO3

-

3. H+ is secreted, HCO3- diffuses into blood

4. blood pH will increase toward normal.

The opposite will occur if the blood pH increases.

B. In the collecting ducts:

Secretion or reabsorption of H+ by primary active transport (can pump against a 1000 fold concentration gradient).

Evaluation of Kidney Function:

A. Blood urea nitrogen (BUN) – in renal disease, BUN rises sharply because the kidneys are not effectively excreting it in the urine.

B. Plasma creatinine – this is a metabolite of creatine, if it rises above 1.5 mg/dl, this indicates poor kidney function.

Clinical Application : increased BUN and Creatinine indicate poor kidney function.

MALE REPRODUCTIVE

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SYSTEM:ORGANS: Testes, scrotum, seminal vesicles, prostate, bulbourethral (Cowper’s)

glands, penis

Testes 1. tunica albuginea – white fibrous capsule that sends septa inward to divide the testes into lobules. Each lobule contains 1-3 highly coiled seminiferous tubules.

2. seminiferous tubules – lined with cells that produce spermatozoa. They also contain sustentacular (Sertoli) cells that function to protect and promote the development of sperm cells.

3. blood-testes barrier – tight junctions between the Sertoli cells prevent the immune cells from attacking the spermatozoa. The sperm would be recognized as foreign and destroyed.

4. interstitial cells (of Leydig) – these cells that are located in groups between the seminiferous tubules. There function is to produce testosterone in response to ICSH.

5. rete testis – tubes that receive sperm from the seminiferous tubules and transport them to the efferent ductules.

6. efferent ductules – tubes that transport sperm from the rete testis to the epididymis.

7. epididymis – receives sperm produced in the testis via the efferent ductules. It is a single, tightly coiled duct. If uncoiled, it would be 18 feet long.

Functions: maturation of the sperm. sperm also develop motility here.

Ducts that carry sperm from the epididymis out of the body.

8. ductus (vas) deferens – muscular tube that carries sperm from the epididymis to the ejaculatory duct. A section of the ductus deferens is severed during a vasectomy.

9. ejaculatory duct – a tube that is formed by the union of the duct of the seminal vesicle and the ampulla of the ductus deferens. This enters the urethra within the prostate gland.

10. urethra – a common tube that receives urine from the bladder or seminal fluid from the ductus deferens and transports them out of the body.

Pathway of sperm through the male duct

seminiferous tubules (within the testes) rete testis efferent ductules epididymis ductus (vas) deferens ejaculatory duct

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system: (within prostate) urethra exterior of body

Blood Supply of the testes:

1. Testicular artery (branch of the abdominal aorta).2. Testicular vein – formed from the pampiniform plexus.

Scrotum sac that contains the testes.

The testes descend from the pelvic cavity into the scrotum through the inguinal canal. After the testes have descended into the scrotum, the inguinal canal contains the spermatic cord. If the inguinal canal opening (inguinal ring) is weakened or too large, part of the intestine can pass into the canal and even into the scrotum. This condition is called an inguinal hernia.

Spermatic Cord contains:

1. ductus (vas) deferens – conveys sperm from epididymis to the ejaculatory duct.

2. testicular artery and vein (pampiniform plexus)3. lymphatic vessels4. testicular nerve5. cremaster muscle – extension of the internal oblique muscle.

Elevates testes when it is cold, relaxes and lowers testes when it is warm. Important in temperature regulation which is critical for the normal production of sperm.

Seminal Vesicles Its secretions constitute about 60% of the semen. This secretion is basic (alkaline) to help neutralize the acidic pH of the urethra and the female reproductive system. This secretion contains fructose, the energy source for sperm motility.

Location: posterior to the urinary bladder.

The ductus deferens unites with the duct of the seminal vesicle to form the ejaculatory duct.

Prostate Surrounds the urethra at the base of the urinary bladder. Secretes an alkaline solution that contains prostaglandins.

Bulbourethral (Cowper’s) glands:

Produces small amount of an alkaline mucus. Provides minor lubrication for intercourse and neutralizes the acidity of the urethra and female reproductive system.

Penis: Contains three masses of erectile tissue. Functions to deposit semen in the vagina.

Structure:Composed of three columns of erectile tissue that are surrounded

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by fibrous connective tissue called the tunica albuginea. These erectile tissues contain numerous tiny blood sinuses called lacunae.Erectile tissue is comprised of the following:

a. corpus spongiosum – erectile tissue that surrounds the urethra. Is softer than the corpora cavernosa that are on the dorsal surface of the penis. The bulb is attached to the perineal membrane. The corpus spongiosum becomes enlarged at the distal end and this portion is called the glans penis. The glans is covered by loose flap of skin called the prepuce.

b. corpora cavernosa – two dorsal masses of erectile tissue. These are attached to the pubic arch. The female clitoris is also composed of this type of erectile tissue.

SPERMATOZOA:

Structure of a Sperm: 1. acrosome – located on the tip of the sperm head. It contains enzymes for digesting the wall of the ovum.

2. head – contains 23 chromosomes (DNA).3. midpiece/body – contains numerous mitochondria.4. tail – a flagella, needed for sperm motility which is critical for the

sperm to move through the female reproductive system.

Spermatogenesis The process in which sperm are produced.

1. spermatogonial cells are outside the blood-testis-barrier (BTB) undergo mitosis.

2. type B spermatogonial cells are transported through the BTB, divide mitotically and produce primary spermatocytes. (2N=diploid)

3. primary spermatocytes undergo first meiotic division forming two secondary spermatocytes (n).

4. secondary spermatocytes undergo second meiotic division each forming two spermatids (total of four).

5. spermiogenesis – the transformation of the spermatids into mature sperm.

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SUMMARY OF MALE REPRODUCTIVE ORGANS AND THEIR FUNCTIONS:

OrganTestes

Epididymis

Vas deferens

Seminal Vesicle

Ejaculatory Duct

Functionproduction of sperm, testosterone

sperm maturation, they become motile

muscular tube which transports sperm to ejaculatory duct during ejaculation

secretes alkaline fluid rich in fructose.

tube formed by the junction of vas deferens and seminal vesicle, transports semen into the urethra

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Prostate Gland

Bulbourethral Gland

Seminal Fluid

External Organs:

Scrotum

Penis

At base of urinary bladder and surrounds urethra. Secretes alkaline fluid.

secrete alkaline mucus for minor lubrication, neutralize acidic pH or urethra and female reproductive system

alkaline pH, fructose to supply energy for sperm, volume 2-6 ml, 120 million sperm/ml

Sac that holds the testes; controls temperature of testes. Contains cremaster muscle which can elevate/descent the testes.

conveys sperm and urine through the urethra; contains erectile tissue which allows it to be inserted into the vagina during intercourse to deposit semen.

HORMONAL CONTROL A. Controlled by hypothalamus, anterior pituitary and testes.

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OF MALE REPRODUCTIVE FUNCTION:

B. Hypothalamus releases gonadotropin-releasing hormone (GnRH) in response to GnRH, the anterior pituitary secretes ICSH and

FSH LH in men is called interstitial cell stimulating hormone

(ICSH) ISCH stimulates the interstitial cells of the testes to secrete

testosterone FSH stimulates the production of sperm cells in the

seminiferous tubules.C. Testosterone

most is produced by the interstitial cells, but some is also produced by the adrenal cortex.

at puberty, testosterone production increases rapidly.

Actions of testosterone:1. stimulates spermatogenesis2. suppresses secretion of GnRH3. development of the male secondary sex characteristics:

growth of body hair: axillary, pubic, facial enlarged larynx and thickened vocal cords – deeper

voice muscular development – tremendous increases in

physical strength bone development

4. production of RBC’s increased hematocrit5. increased secretion of growth hormone6. increases libido

Testosterone is controlled by a negative feedback:

GnRH (hypothalamus) increases ICSH from the anterior pituitary increases testosterone production and release from the interstitial cells in the testes increased testosterone feeds back to the hypothalamus decreases GnRH decreases ICSH decreases testosterone cycle repeats

FEMALE REPRODUCTIVE SYSTEM:

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ORGANS OF THE FEMALE REPRODUCTIVE SYSTEM:

ovary, uterine (Fallopian) tubes, uterus, vagina, vulva, accessory glands

Ovary the female gonad

1. functions: a. produce ova (eggs)b. produce female sex hormones – estrogen and progesterone

2. structure: a. tunica albuginea – connective tissue capsule of the ovaryb. cortex – outer region of the ovary where the primordial

follicles are located and the ova develop.c. medulla – central region of the ovary where the blood vessels

are located.d. ligaments

ovarian ligament holds ovary to the uterus suspensory ligament attaches ovary to the pelvic wall

e. blood supply: ovarian artery and vein

Uterine Tubes also called oviduct or Fallopian tube

1. infundibulum – adjacent to the ovary, flared end with many projections called fimbriae.

2. ampulla – middle portion of the tube. This is where fertilization must occur for the embryo to implant in the uterus.

3. isthmus – narrow portion that conveys ovum or embryo into the uterus.

4. The wall contains smooth muscle and the tube is lined with a ciliated epithelium. Muscular contractions and the cilia move the ova toward the uterus.

Uterus thick, muscular organ that is connected to the oviducts superiorly and to the vagina inferiorly

1. Functions :a. provides a location for the growth of the embryo and fetusb. provides nutrition for the embryo/fetusc. muscular contractions expel the fetus during birth

2. Structure of the Uterus : (size: height = 7 cm)

a. fundus – the broad superior portion

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b. body (corpus) – midportionc. isthmus – point at which the body narrowsd. cervix – inferior portion that communicates with the vagina via

the cervical canalinternal os – opens into the uterusexternal os – opens into the vagina

cervical glands – produce a thick mucus. This prevents the entrance of microbes from the vagina into the uterus.

This mucus thins around the time of ovulation so that sperm can enter the uterus and Fallopian tubes.

Clinical application:The Pap smear looks at the squamous cells of the external

surface of the cervix to detect precancerous or malignant changes indicating cervical cancer.

e. lumen within the uterus is triangular: the opening of the oviducts superiorly, the internal os inferiorly.

3. layers of the uterine wall:a. perimetrium – the serosa. The membranous outer covering.b. myometrium – the smooth muscle that comprises most of the

thickness of the wall.c. endometrium – the simple columnar epithelium that lines the

inside of the uterus and the glands, connective tissues and blood vessels associated with it. It serves as the site of attachment for the developing embryo.

Layers of the endometrium: stratum functionalis – superficial 2/3 that is shed

during each menstrual cycle. stratum basalis – deep 1/3 that regenerates a new

stratum functionalis during each menstrual cycle.

4. blood supply to the uterus: a. uterine artery (from internal iliac artery)b. arcuate arteries penetrate into the myometriumc. spiral arteries penetrate through inner myometrium into the

endometrium

Vagina 1. Functions :a. discharge of menstrual fluid during menstruationb. receives penis and semen during intercoursec. serves as the birth canal

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2. Structure: a. adventitia – outer connective tissue layer that attaches the

vagina to surrounding structuresb. muscularis – middle layerc. mucosa – epithelium is stratified squamous non-keratinized –

this protects the underlying tissues.

Vulva the external genitalia

1. mons pubis – mound of adipose tissue that overlies the pubic symphysis.

2. labia majora – pair of thick folds of skin and adipose tissue inferior to the mons. These are covered with hair and are homologous to the scrotum in the male.

3. labia minora – medial and internal to the labia majora. Much thinner, hairless. Function: to cover and protect the vestibule.

4. vestibule – the area enclosed by the labia minora. Contains the urethral and vaginal openings.

5. clitoris – composed of erectile tissue like the penis but lacks a corpus spongiosum and does not enclose the urethra. Internally, two corpora cavernosa (crura) attach to the pubic bones. The glans portion of the clitoris protrudes slightly from the prepuce, the anterior point where the labia minora meet.

Accessory Glands greater vestibular (Bartholin) glands – located on either side of the vaginal orifice with a short duct that opens into the vagina. Keeps the vulva moist and provides most of the lubrication for intercourse. The male bulbourethral glands only provide a minimal lubrication.

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Secondary Sex Characteristics:

A. Distribution of body fat – thighs, gluteal area, breasts.B. Pitch of the voiceC. Pelvic bone structureD. Hair growth in the axilla and pubic regionsE. Breast development – mammary glands develop with increased

fat deposition.1. Non-lactating breast consists of adipose and callagenous tissue.

Contains little mammary gland.2. Suspensory ligaments attach the breast to the dermis and to

the fascia of pectoralis major.3. During pregnancy, the mammary glands greatly hypertrophy.4. Lactiferous ducts drain into lactiferous sinuses near the

nipple.

Clinical Application:Breast cancer will occur in approximately 1 of 9 women in the United States.

Signs and Symptoms:A palpable lump, puckering of skin, orange peel skin, changes in skin texture, discharge from nipple.

Most tumors are first detected by breast self-exam.

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Mammograms detect tumors much smaller than can be detected by breast self examination.

If your grandmother, mother, and/or sisters have had breast cancer, it is even more important that you get regular exams and at an earlier age.

Pathway of Ovum: Mature (Graafian) follicle ruptures releasing the ovum infundibulum (fimbriae) move the ovum into the oviduct cilia and gentle muscle contractions of oviduct transport the ovum through oviduct from the infundibulum ampulla isthmus uterus internal os cervical canal external os vagina exterior

Summary of the Female Reproductive System Organs:

Organs:

Ovary

Uterine (Fallopian) Tubes

Uterus

Vagina

Labia Majora

Labia Minora

Clitoris (corpora cavernosa)

Functions:

produce mature ova, secrete estrogen and progesterone

transport the ovum toward the uterus

receives embryo and sustains in during development, contractions expel the fetus during birth

conveys uterine secretions (menstruation), receives penis during intercourse, birth canal

enclose and protect external reproductive organs

protects structures in the vestibule and the openings of the vagina and urethra

erectile tissue that acts as sensory organ during sexual arousal and intercourse

Female Sex Hormones:(Estrogen & Progesterone)

A. GnRH hypothalamus increases secretion of FSH and LH (luteinizing hormone)

FSH stimulates the formation of a mature (Graafian) follicle

LH stimulates ovary to increase its secretion of estrogen

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B. Increased Estrogen causes: 1. enlargement of female reproductive organs (at puberty)2. development of the mammary gland (at puberty and to a

much greater degree, during pregnancy)3. fat deposition in the breasts, thighs, hips (this is genetically

determined and fat deposition varies)4. distribution of body hair in axilla and pubic regions5. increase in libido

Female Reproductive Cycles:

A. Oogenesis – the process of meiosis in the ovary that results in the formation of a single ovum.

Meiosis II only occurs if the oocyte is fertilized by sperm.

Only one ovum is formed during meiosis, the other chromosomes are thrown away as polar bodies.

Primary Oocyte Meiosis I > Secondary Oocyte Meiosis II > Zygote Embryo

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B. Menstrual Cycle GnRH is released from hypothalamus GnRH stimulates anterior pituitary to release FSH and LH FSH stimulates ovary to produce a mature follicle containing

a single ovum LH promotes the production and release of estrogen that

stimulates the development of the stratum functionalis of the endometrium of the uterus.

as the follicle develops in response to FSH, follicular cells secrete increasing amounts of estrogen which causes an increase in thickness of the endometrium, preparing it for possible implantation of the developing embryo.

at about the 14th day of the cycle, there is a rapid rise in estrogen secretion.

this creates a positive feedback that causes the hypothalamus to release more GnRH.

the increased GnRH stimulates the anterior pituitary releases a very large amount of LH (LH surge) and FSH.

the LH surge causes a further increase in estrogen secretion. the LH surge causes the mature follicle to swell with follicular

fluid and rupture, releasing the ovum – ovulation. the remnants of the ruptured follicle becomes a temporary

endocrine structure called a corpus luteum that secretes larger quantities of estrogen and progesterone during the 2nd half of the menstrual cycle.

blood progesterone levels rise most sharply. progesterone increases the vascular and glandular nature of

the endometrium. It also stimulates endometrium to store glycogen and fats which will provide nutrition for the embryo.

If Fertilization and Implantation do NOT Occur:

the corpus luteum degenerates. the levels of estrogen and progesterone decrease. the stratum functionalis of the endometrium sloughs off. the stratum functionalis and blood from the damaged capillaries

pass through the vagina as the menstrual flow. low levels of estrogen/progesterone stimulate the release of

GnRH from the hypothalamus. cycle repeats.

Terminology: a Zygote is formed when one sperm and one ovum join nuclei. the offspring is called an embryo until the end of the 8th week. after week 8 until birth, the conceptus is called a fetus.