Lecture 25: Male Reproductive Physiology

Question 1

What is spermatogenesis?

Answer 1

A meiotic process that culminates in the formation of haploid spermatids.

Question 2

What do primordial germ cells migrate into future testes and become?

Answer 2

spermatogonia

Question 3

What do spermatogonia become after mitotic division at puberty?

Answer 3

primary spermatocytes

Question 4

What do primary spermatocytes become after the completion of the first half of meiosis?

Answer 4

secondary spermatocytes

Question 5

What do secondary spermatocytes become after completion of the second half of meiosis?

Answer 5

spermatids

Question 6

What do spermatids become after they undergo differentiation?

Answer 6

mature sperm

Question 7

Where are sertoli cells located?

Answer 7

Within the seminiferous tubules.

Question 8

What do sertoli cells act as?

Answer 8

Nurse Cells (sustentacular cells) that surround primary spermatocytes and “nurse” them through the process of spermatoenesis and spermiogenesis.

Question 9

What do sertoli cells nurse primary spermatocytes through?

Answer 9

Spermatogenesis and Spermiogenesis

Question 10

What is spermiogenesis?

Answer 10

Differentiation of spermatids into mature sperm.

Question 11

What do sertoli cells form estrogen from?

Answer 11

Testosterone (thought to be important for spermiogenesis).

Question 12

Talk through spermiogenesis.

Answer 12

> Proacrosomal vesicles coalesce to form acrosome: contains 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 is sloughed off: residual body.

> Sperm cells are stored in epididymis until ejaculated.

> Sperm cells must remain in epididymis for a minimum of 18 to 24 hours in order to gain motility.

> Passage through the epididymis requires several days.

Question 13

Where are cells of Leydig found?

Answer 13

Interstitial spaces in testes.

Question 14

What do cells of Leydig secrete?

Answer 14

Testosterone

Question 15

What cells in the male reproductive tract secrete testosterone?

Answer 15

Cells of Leydig

Question 16

What stimulates cells of Leydig to secrete testosterone?

Answer 16

Stimulated by luteinizing hormone (LH) secreted by anterior pituitary.

Question 17

What hormone, besides LH, is also necessary for spermatogenesis?

Answer 17

FSH

Question 18

What are the two accessory glands in the male reproductive system?

Answer 18

• seminal vesicles

- prostate gland

Question 19

What is each vesicle of the seminal vesicles lined with?

Answer 19

Each vesicle is a loculated tube lined with secretory epithelium.

Question 20

What is secreted by seminal vesicles?

Answer 20

Secretes a mucoid material.

Question 21

What does the mucoid material that is secreted by seminal vesicles contain?

Answer 21

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

Question 22

What percentage of the total volume of semen does the mucoid material secreted by seminal vesicles make up?

Answer 22

60%

Question 23

What does the fructose that is contained in the mucoid material that is secreted by seminal vesicles provide energy for?

Answer 23

Energy for Sperm

Question 24

What is the function of prostaglandins found in the mucoid material that is secreted by seminal vesicles?

Answer 24

Make cervical mucous more receptive to sperm movement and may cause retro-peristaltic contractions of uterus and fallopian tubes.

Question 25

What molecule found in the mucoid secretions of seminal vesicles makes the cervical mucous more receptive to sperm movement and may cause retro-peristaltic contractions of the uterus and fallopian tubes?

Answer 25

prostaglandins

Question 26

What percentage of the total volume of semen does the milky fluid secreted by the prostate gland make up?

Answer 26

30%

Question 27

What does the milky fluid secreted by the prostate gland contain?

Answer 27

- calcium - citrate ions - phosphate ions - clotting enzyme - profibrinolysin

Question 28

Is the milky fluid secreted by the prostate gland slightly alkaline or acidic?

Answer 28

Slightly Alkaline

Question 29

Why is it important that the milky fluid secreted by the prostate gland is slightly alkaline?

Answer 29

Helps to neutralize acidity of other seminal fluids and vaginal secretions of the female.

Question 30

What is the definition of androgens?

Answer 30

Any steroid hormone that has masculinizing effects.

Question 31

What are testosterone, dihydrotestosterone, and androstenedione?

Answer 31

androgens

Question 32

What are androgens synthesized from in the testes and adrenal gland?

Answer 32

cholesterol + acetyl-CoA

Question 33

What is 97% of testosterone bound to in the blood?

Answer 33

- loosely bound with albumin | - tightly bound with beta globulin

Question 34

Testosterone

Answer 34

> Formed by interstitial cells of Leydig: - Cells are numerous in newborn males and adult male after puberty. - Almost nonexistent in testes during childhood.

Question 35

What is testosterone converted into after it enters tissues?

Answer 35

Mostly converted to dihydrotestosterone, especially in prostate and in fetal external genitalia.

Question 36

What is testosterone that is not fixed in tissues converted to in the liver?

Answer 36

- androsterone | - dehydroepiandrosterone

Question 37

Testosterone that is not fixed in tissues?

Answer 37

- Conjugated as either glucuronides or sulfates. - Excreted into gut via bile or urine via kidneys. - Converted in liver to: > androsterone > dehydroepiandrosterone

Question 38

What are the functions of testosterone?

Answer 38

- Responsible for 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 hair pattern growth. - Associated with baldness. - Responsible for hypertrophy of larynx. - Increased skin thickness and secretion rate of sebaceous glands. - Responsible for increase in protein formation and muscle formation. - Responsible for increase in bone matrix and calcium retention. - Responsible for increased BMR. - Responsible for increased hematocrit. - Increases reabsorption of sodium in distal kidney tubules.

Question 39

Where are the neurons located that produce gonadotropin-releasing hormone (LH-releasing hormone)?

Answer 39

Produced by neurons located in arcuate nuclei of hypothalamus.

Question 40

What does gonadotropin-releasing hormone stimulate the anterior pituitary to produce?

Answer 40

- LH (mostly) | - FSH (gonadotropic hormones)

Question 41

What second messenger system in target tissues are activated by luteinizing hormone (LH)?

Answer 41

cAMP second messenger system in target tissues

Question 42

What does luteinizing hormone (LH) cause sertoli cells to secrete?

Answer 42

testosterone **testosterone has a negative feedback effect on hypothalamus**

Question 43

What cell type secretes inhibin?

Answer 43

sertoli cells

Question 44

What is the function of inhibin, which is secreted by sertoli cells?

Answer 44

> Inhibits secretion of FSH by anterior pituitary. | > Also, inhibits secretion of GnRH to a lesser extent.

Question 45

Look over figure 81-10 (feedback regulation of the hypothalamic-pituitary-testicular axis).

Answer 45

Know this well for the exam.