Lecture 25: Male Reproductive Physiology Flashcards
What is spermatogenesis?
A meiotic process that culminates in the formation of haploid spermatids.
What do primordial germ cells migrate into future testes and become?
spermatogonia
What do spermatogonia become after mitotic division at puberty?
primary spermatocytes
What do primary spermatocytes become after the completion of the first half of meiosis?
secondary spermatocytes
What do secondary spermatocytes become after completion of the second half of meiosis?
spermatids
What do spermatids become after they undergo differentiation?
mature sperm
Where are sertoli cells located?
Within the seminiferous tubules.
What do sertoli cells act as?
Nurse Cells (sustentacular cells) that surround primary spermatocytes and “nurse” them through the process of spermatoenesis and spermiogenesis.
What do sertoli cells nurse primary spermatocytes through?
Spermatogenesis and Spermiogenesis
What is spermiogenesis?
Differentiation of spermatids into mature sperm.
What do sertoli cells form estrogen from?
Testosterone (thought to be important for spermiogenesis).
Talk through spermiogenesis.
> 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.
Where are cells of Leydig found?
Interstitial spaces in testes.
What do cells of Leydig secrete?
Testosterone
What cells in the male reproductive tract secrete testosterone?
Cells of Leydig
What stimulates cells of Leydig to secrete testosterone?
Stimulated by luteinizing hormone (LH) secreted by anterior pituitary.
What hormone, besides LH, is also necessary for spermatogenesis?
FSH
What are the two accessory glands in the male reproductive system?
- seminal vesicles
- prostate gland
What is each vesicle of the seminal vesicles lined with?
Each vesicle is a loculated tube lined with secretory epithelium.
What is secreted by seminal vesicles?
Secretes a mucoid material.
What does the mucoid material that is secreted by seminal vesicles contain?
- fructose
- citric acid
- additional nutrients
- prostaglandins
- fibrinogen
What percentage of the total volume of semen does the mucoid material secreted by seminal vesicles make up?
60%
What does the fructose that is contained in the mucoid material that is secreted by seminal vesicles provide energy for?
Energy for Sperm
What is the function of prostaglandins found in the mucoid material that is secreted by seminal vesicles?
Make cervical mucous more receptive to sperm movement and may cause retro-peristaltic contractions of uterus and fallopian tubes.
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?
prostaglandins
What percentage of the total volume of semen does the milky fluid secreted by the prostate gland make up?
30%
What does the milky fluid secreted by the prostate gland contain?
- calcium
- citrate ions
- phosphate ions
- clotting enzyme
- profibrinolysin
Is the milky fluid secreted by the prostate gland slightly alkaline or acidic?
Slightly Alkaline
Why is it important that the milky fluid secreted by the prostate gland is slightly alkaline?
Helps to neutralize acidity of other seminal fluids and vaginal secretions of the female.
What is the definition of androgens?
Any steroid hormone that has masculinizing effects.
What are testosterone, dihydrotestosterone, and androstenedione?
androgens
What are androgens synthesized from in the testes and adrenal gland?
cholesterol + acetyl-CoA
What is 97% of testosterone bound to in the blood?
- loosely bound with albumin
- tightly bound with beta globulin
Testosterone
> Formed by interstitial cells of Leydig:
- Cells are numerous in newborn males and adult male after puberty.
- Almost nonexistent in testes during childhood.
What is testosterone converted into after it enters tissues?
Mostly converted to dihydrotestosterone, especially in prostate and in fetal external genitalia.
What is testosterone that is not fixed in tissues converted to in the liver?
- androsterone
- dehydroepiandrosterone
Testosterone that is not fixed in tissues?
- Conjugated as either glucuronides or sulfates.
- Excreted into gut via bile or urine via kidneys.
- Converted in liver to:
> androsterone
> dehydroepiandrosterone
What are the functions of testosterone?
- 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.
Where are the neurons located that produce gonadotropin-releasing hormone (LH-releasing hormone)?
Produced by neurons located in arcuate nuclei of hypothalamus.
What does gonadotropin-releasing hormone stimulate the anterior pituitary to produce?
- LH (mostly)
- FSH (gonadotropic hormones)
What second messenger system in target tissues are activated by luteinizing hormone (LH)?
cAMP second messenger system in target tissues
What does luteinizing hormone (LH) cause sertoli cells to secrete?
testosterone
testosterone has a negative feedback effect on hypothalamus
What cell type secretes inhibin?
sertoli cells
What is the function of inhibin, which is secreted by sertoli cells?
> Inhibits secretion of FSH by anterior pituitary.
> Also, inhibits secretion of GnRH to a lesser extent.
Look over figure 81-10 (feedback regulation of the hypothalamic-pituitary-testicular axis).
Know this well for the exam.
