Male Reproductive Physiology Flashcards
Understand the role of the Sry gene in determining gender.
SRY, the mammalian Y-chromosomal testis-determining gene, induces male sex determination. The major role of SRY is to achieve sufficient expression of the related gene Sox9, in order to induce Sertoli cell differentiation, which in turn drives testis formation.
Describe the location and function of Sertoli cells.
located in seminiferous tubules, Sertoli cells act as nurse cells (sustentacular cells) that surround primary spermatocytes and “nurse” them through the process of spermatogenesis and spermiogenesis (differentiation of spermatids into mature sperm)
Form estrogens from testosterone: •Thought to be important for spermiogenesis
Describe the location and function of cells of Leydig.
Found in interstitial spaces in testes.
Secrete testosterone
Stimulated by luteinizing hormone secreted by anterior pituitary.
FSH is also necessary for spermatogenesis.
Describe the stages of 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
Describe the secretions and functions of the secretions of the seminal vesicles.
•Paired structures behind prostate. •Each vesicle is a loculated tube lined with secretory epithelium: •Secretes a mucoid material that contains: •Fructose •Citric acid •Additional nutrients •Prostaglandins •Fibrinogen During emission and ejaculation: •Contents of vesicles are emptied into ejaculatory ducts containing sperm. •60% of total volume of semen •Fructose provides energy for sperm •Prostaglandins make cervical mucous more receptive to sperm movement and may cause retro-peristaltic contractions of uterus and fallopian tubes.
Describe the secretions and functions of the secretions of the prostate gland
location where testosterone is converted to dihydrotestosterone During emission and ejaculation: •30% of total volume of semen •Milky fluid containing calcium, citrate ions phosphate ions, clotting enzyme, and profibrinolysin •Slightly alkaline fluid: •May help to neutralize acidity of other seminal fluids and vaginal secretions of the female.
List kinds of androgens and, sources of androgens, and functions of androgens.
Definition: •Any steroid hormone that has masculinizing effects. Formed by interstitial cells of Leydig.
Include: •Testosterone •Dihydrotestosterone •Androstenedione
Can be synthesized in testes and adrenal glands from: •Cholesterol •Acetyl-CoA
List the major hormones that control reproduction and list their specific functions.
Gonadotropin-Releasing Hormone: Stimulates anterior pituitary to produce: •LH (mostly) and FSH (Gonadotropic hormones)
Luteinizing Hormone (LH): Causes Sertoli cells to secrete testosterone. •Testosterone has a negative feedback effect on hypothalamus.
Inhibin: Inhibits secretion of FSH by anterior pituitary. •Also inhibits secretion of GnRHto a lesser extent.
Describe the stages of spermatogenesis
Spermatogenesis is a meiotic process that culminates in the formation of haploid spermatids.
- Primordial germ cells: Migrate into future testes and become: SPERMATOGONIA
- Spermatogonia: Begin mitotic division at puberty and become: PRIMARY SPERMATOCYTES
- Primary spermatocytes: Complete the first half of meiosis and become: SECONDARY SPERMATOCYTES
- Secondary spermatocytes: Complete the second half of meiosis and become: SPERMATIDS
- Spermatids: Undergo differentiation to become: Mature sperm
