Reproductive System

Question 1

source of testicular testosterone

Answer 1

Leydig cells- interstitial cells

Question 2

how does the concentration in the testes compare to the systemic concentration

Answer 2

100x more concentrated in testes

Question 3

how does testosterone circulate

Answer 3

97% bound, 44% bound to testosterone-estradiol-binding-protein

Question 4

what stimulates TeBG production?

Answer 4

estradiol

Question 5

describe the MOH of testosterone

Answer 5

passive diffusion into androgen receptor in the nucleus

tissues are Wolffian duct, pituitary, and kidney

Question 6

DHT

Answer 6

dihydrotestosterone- testosterone converted to DHT at the urogenital sinus by 5a-reductase

DHT binds to androgen receptors but is 100x more potent

Question 7

how does DHT amplify testosterone results

Answer 7

1. conversion is irreversible and cannot be converted to estrogen

2 DHT has a higher affinity for androgen receptors

3. DHT receptor complex is more efficient at binding DNA site

Question 8

describe sexual differentiation in males

Answer 8

sex-determining region produces testes determing factor, which promotes development of the testes. cells in the medulla of primitive sex cords develop into sertoli cells, and the mesenchyme becomes leydig cells

if the gonad develops into testes then:

1. wolffian duct develops into epididymis, vas, and seminal vesicles

2 mullerian system is inhibited by MIF

3 DHT causes differentiation of genital tubercle to penis, scrotum, prostate, and urethra

Question 9

androgen insensitivity

Answer 9

XY genotype in females w/ androgen resistance of target tissues. 3 categories

1. complete- external genitalia are female
   2 mild- external genitalia are male
   3 partial- external genitalia are partially but not fully masculinized

Question 10

why do patients w/ complete AIS feminize?

Answer 10

1. estradiol secretion increases significantly per day

2 androgen resistance

Question 11

5a-reductase deficiency

Answer 11

dont have enzyme to convert testosterone into DHT. can have male, female or ambiguous genitalia

born w/ testis and wolffian structures, but female primary sex characteristic

Question 12

functions of androgens in males in terms of sex characteristics

Answer 12

1. differentiation of wolffian ducts and external genitalia
2. puberty- enlargement of external genitalia
3. facial skin increases sebaceous gland activity
   4 body hair growth
   5 growth spurt
   6 enlargement of vocal cords
   6 spontaneous erection

Question 13

anabolic functions of androgens

Answer 13

1 increased bone and muscle mass
2 accumulation of K P and Ca
3 stimulation of linear bone growth
4 increase in protein synthesis

Question 14

Leydig cell regulation

Answer 14

leydig cells produce testosterone

stimulated by LH
inhibited by testosterone via conversion to estradiol at hypothalamus and ant pit

Question 15

GnRH causes what?

Answer 15

release of both LH and FSH. release is periodic

Question 16

describe spermatogenesis

Answer 16

basal spermatogonia undergo mitotic division to form primary spermatocyte. undergo meiotic division to form secondary spermatocyte. mature into spermatotids and transform into spermatozoa.

Question 17

sertoli cell functions

Answer 17

1 support for stem cells
2 form blood testis barrier
3 phagocytoze damaged sperm
4 synthesize and secrete estradiol
5 secrete androgen binding protein

Question 18

FSH effects in males

Answer 18

stimulates spermatogenesis by acting on sertoli cells and by triggering a key event in spermatogenesis that will start the process (and will continue for as long as testosterone present

Question 19

FSH regulation

Answer 19

can be inhibited w/ high doses of testosterone and estrogen, but primarily by inhibin

inhibin is secreted by sertoli cells

Question 20

describe female sexual differentiation

Answer 20

in the absence of SRY and TDF, and in the presence of Wnt-4, cortical sex cords develop in an ovary. this causes:

1 wolffian ducts atrophy and mullerian system develops

2 estrogen causes mullerian development into fallopian tubes, uterus, and vagina

3 w/ estrogen, external genitalia develops from genital tubercule (low vagina, clitoris, labia)

Question 21

effects of FSH in females

Answer 21

acts (w/ estradiol and LH) on FSH receptors on granulosa cells to

1 stimulate follicle growth and maturation
2 stimulate LH receptor formation
3. stimulate granulosa cells to form aromatase to form estradiol

Question 22

effects of LH in females

Answer 22

1 causes preovulatory follicle to rupture and release ovum
2 midcycle LH surge is essential for ovum maturation and ovulation
3 stimulation and maintenance of corpus luteum
4 causes thecal cells to produce androstenedione

Question 23

effects of estradiol in females

Answer 23

at puberty, increases in estradiol secretion by ovary cause

1.  maturation of uterus
2  maturation of cervix
3 hypertrophy of breast
4 feminine body contour
5 pubic hair
6 shape of pelvis
7 increase vascularity of skin
8 stimulate closure of epiphysis

Question 24

effects of progesterone in females

Answer 24

1. prep endometrium for ovum implantation
   2 glycogen increase in uterine epithelial cells for blastocyst consumptoin
   3 inhibits spontaneous uterine contractions
   4 blocks oxytocin effects during pregnancy
   5 mucus becomes resistant to sperm
   6 breast development
   7 natriuretic effect (Na loss)

Question 25

two cell theory of estrogen production in females

Answer 25

androstenedione is synthesized by thecal cell in response to LH, where it diffuses to granulosa cells and it is converted to estradiol by aromatase.

FSH causes an increase in aromatase secretion in granulosa cells

Question 26

how is estradiol moved in the blood

Answer 26

bound to albumin

Question 27

describe the burst of the ovarian follicle

Answer 27

following LH surge, oocyte matures and there is an increase of progesterone. progesterone stimulates proteolytic enzymes that digest collagen and weaken of the follicular walls

Question 28

describe 2 estradiol/progesterone receptors

Answer 28

1. steroid receptors

2 indirectly though receptors in uterine fibroblasts

Question 29

gonadal regulation of FSH

Answer 29

activin- stimulates FSH but not LH
inhibin- inhibits FSH but not LH
follistatin- inhibits FSH

Question 30

describe the menstrual cycle

Answer 30

day 1- first day of bleeding

just prior to onset of menses- blood levels of FSH rise (d/t removal of estrogen/progesterone from previous cycle), causing follicle maturation

during the beginning of follicular phase, developing follicle secretes activin, which further stimulates GnRP and FSH.

increased FSH causes estradiol secretion by granulosa cells

estradiol increases FSH and LH receptor density in the follicle

later in the follicular phase, inhibin and follistatin are produced by developing follicle, inhibiting FSH release

as the follicle continues to mature, estradiol levels reach a peak where the feedback on the hypothalamus goes from negative to positive, creating the LH and FSH surge

LH and progesterone cause follicle rupture

remaining granulosa and theca interna become corpus luteum, which continues secreting progesterone and estradiol

if fertilization does not occur, corpus luteum regresses and progesterone and estradiol levels fall, causing FSH levels to increase

Question 31

implantation window

Answer 31

5-7 days after luteal surge when uterus is receptive to implantation

Question 32

window of vulnerability

Answer 32

7-10 days after ovulation where immune system is suppressed and women are more likely to get become infected

Question 33

describe fertilization

Answer 33

acrosome pierces ovum, changing electrical conductance of outer layer, causing release of granules that swell and prevent other sperm from entering