Male Reproductive Physiology

Question 1

Where do primordial germ cells migrate and what do they ultimately become?

Answer 1

-migrate into future testes and become spermatogonia

Question 2

What do spermatogonia do?

Answer 2

-begin mitotic division at puberty and become primary spermatocytes

Question 3

What do primary spermatocytes do?

Answer 3

-complete the first half of meiosis and become secondary spermatocytes

Question 4

What do secondary spermatocytes do?

Answer 4

-complete the second half of meiosis and become spermatids

Question 5

What do spermatids do?

Answer 5

-undergo differentiation to become mature sperm

Question 6

Where are Sertoli cells located?

Answer 6

-within the seminiferous tubules

Question 7

What is the function of Sertoli cells?

Answer 7

• act as nurse cells (sustentacular cells) that surround primary spermatocytes and nurse them through the process of spermatogenesis and spermiogenesis
• form estrogens and testosterone important for spermiogenesis

Question 8

What happens during spermiogenesis?

Answer 8

• proacrosomal vesicles coalesce to form acrosome (hyaluronidase and proteolytic enzymes)
• nucleus becomes highly condensed
• acrosome caps nucleus
• centrioles migrate to side of nucleus opposite acrosome
• distal centriole begins to organize flagellum
• mitochondria move to base of forming flagellum and wrap around it
• excess cytoplasm a is sloughed off as residual body

Question 9

Where are sperm cells stored until ejaculation?

Answer 9

-epididymis, requires several days to pass through

Question 10

How long must sperm remain in the epididymis?

Answer 10

-minimum of 18-24 hours in order to gain motility

Question 11

Where are Leydig cells found?

Answer 11

-interstial spaces in testes

Question 12

What is the function of Leydig cells?

Answer 12

-secrete testosterone

Question 13

What stimulates the Leydig cells?

Answer 13

• LH secreted by anterior pituitary

- FSH is also necessary for spermatogenesis

Question 14

What are the two male accessory glands?

Answer 14

• seminal vesicles

- prostate gland

Question 15

Where are the seminal vesicles?

Answer 15

• paired structures behind the prostate

- each vesicle is a loculated tube lined with secretory epithelium

Question 16

What is in the mucosa material that the seminal vesicles secrete?

Answer 16

• fructose
• citric acid
• additional nutrients
• prostaglandins
• fibrinogen

Question 17

What happens to the seminal vesicles during emission and ejaculation?

Answer 17

• contents of vesicles are emptied into ejaculatory ducts contains sperm
• 60% total volume of semen
• fructose provides energy for sperm
• prostaglandins make cervical mucus more receptive to sperm movement and may causes retro-peristaltic contractions of uterus and Fallopian tubes

Question 18

What happens to the prostate gland during emission and ejaculation?

Answer 18

• 30% total volume of semen
• milky fluid containing Ca, citrate ions, phosphate ions, clotting enzyme, and profibrinolysin
• slightly alkaline fluid -> helps neutralize acidity of other seminal fluids and vaginal secretions of the female

Question 19

What is an androgens? What does this include?

Answer 19

• any steroid hormone that has masculinizing effects
• testosterone
• dihydrotestosterone
• androstenedione

Question 20

What can androgens be synthesized from?

Answer 20

-can be synthesized in testes and adrenal glands from cholesterol and acetyl CoA

Question 21

What forms testosterone?

Answer 21

• Leydig cells
• cells are numerous in newborn males and adult males after puberty
• almost nonexistent in testes during childhood

Question 22

What happens to testosterone after secretion?

Answer 22

• 97% is loosely bound with albumin or tightly bound with beta globulin
• circulates in blood for 30mins to several hours
• transferred to tissues or degraded to inactive products that are subsequently secreted

Question 23

What happens to testosterone that enters tissue?

Answer 23

-mostly converted to dihydrotestosterone especially in prostate and in fetal external genitalia

Question 24

What happens to testosterone that is not fixed in tissues?

Answer 24

• converted in lover to androsterone and dehydroepiandrosterone
• conjugated as either glucuronides or sulfate so
• excreted into gut via bile or urine via kidneys

Question 25

What are the functions of testosterone?

Answer 25

-distinguishing characteristics of masculine body
-stimulates descent of testes
-responsible for enlargement of external genitalia and formation of secondary male sexual characteristics
-responsible for male pattern hair growth
+associated with baldness
-responsible for hypertrophy of larynx
-increased skin thickness and secretion rate of sebaceous glands
-increase in protein formation and muscle formation
-increased in bone matrix and Ca retention
-increased BMR
-increased hematocrit
-reabsorption of Na in distal kidney tubules

Question 26

What does gonadotropin releasing hormone do?

Answer 26

• produced by neurons located in arcuate nuclei of hypothalamus
• transported to anterior pituitary via hypothalamic-hypophyseal system
• stimulates anterior pituitary to produce LH and FSH

Question 27

What does LH do?

Answer 27

• activates cAMP second messenger system in target tissues

- causes Sertoli cells to secrete testosterone -> negative feedback effect on hypothalamus

Question 28

What secretes inhibin? What does it do?

Answer 28

• secreted by Sertoli cells
• inhibits secretion of FSH by anterior pituitary
• inhibits secretion of GnRH to a lesser extent

Question 29

What determines the embryo to be male?

Answer 29

-SRY gene