Physio: Reproductive Physiology - Male Reproduction
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- What three types of cells are in the epithelium lining the seminiferous tubules?
- spermatogonia (stem cells), spermatocytes (in process of development), and Sertoli cells
- What are the three main supportive functions of Sertoli cells?
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1. provide nutrients
2. form tight jns to create blood-testes barrier
3. create aqueous fluid in lumen to help transport sperm to epididymis - During what life stages does spermatogenesis occur?
- ENTIRE LIFE!
- Spermatogonia -> ??????? -> Spermatozoon
- spermatogonia -> mitosis -> generate primary spermatocytes -> meiosis I -> secondary spermatocytes -> meiosis II -> spermatid -> spermiogenesis -> spermatozoa
- How long does one full cycle of spermatogenesis take?
- 64 days
- How do prostaglandins secreted by the seminal vesicles aid in fertilization?
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1. react w/cervical mucus to make it more penetrable
2. induce peristaltic contractions in female repro tract - How do prostate secretions aid in fertilization?
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(rich in citrate, Ca, enzymes)
alkalinity increases sperm motility, neutralizes acidic vaginal secretions - How are sperm modified once they are in the female repro tract?
- capacitation occurs: inhibitory factors washed free, surface proteins redistributed, surf cholesterol removed, Ca influx increases motility, acrosomal reaction
- What is the acrosomal reation?
- acrosomal membrane and sperm membrane fuse, releasing hydrolytic enzymes that can create a path for sperm to penetrate ovum's protective coverings
- How does the testicular steroidogenic pathway differ from the adrenal steroidogenic pathway?
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in testes:
1)no 21beta-hydroxylase or 11beta-hydroxylase = no glucocort/mineralocort
2)has 17beta-hydroxysteroid dehydrogenasae, which converts androstenedione to testost - What is the active form of testosterone in some tissues? How is this produced?
- dihydrotestosterone (converted by 5alpha-reductase)
- In what forms does testosterone circulate?
- 98% bound to sex steroid-binding globulin or albumin (acts as reservoir), 2% free (active)
- What hormone stimulates the production of testosterone?
- LH (stimulates cholesterol desmolase)
- What type of inhibitor could be used to treat benign prostatic hypertrophy?
- 5alpha-reductase inhibitors (finasteride)
- What type of cells does FSH stimulate?
- Sertoli cells, to promote spermatogenesis
- What type of cells does LH stimulate?
- Leydig cells, to produce testosterone
- What paracrine effect does testosterone have?
- diffues to nearby Sertoli cells to reinforce spermatogenic action of FSH
- What two substances exert negative feeback control over GnRH, LH, and FSH?
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1. testosterone inhibits hypothal and s/c of LH from a/p
2. inhibin (produced by Sertoli cells) inhibits s/c of FSH from a/p - What are the prenatal actions of testosterone?
- differentiation of internal genital tract (of wolffian ducts)
- What are the prenatal actions of dihydrotestosterone?
- differentiation of external male genitalia
- What are the pubertal effects of testosterone?
- increased muscle mass, growth spurt, closure of epiphyseal plates, growth of penis and seminal vesicles, deepening of voice, spermatogenesis, libido
- What are the post-natal effects of dihydrotestosterone?
- male hair pattern, pattern baldness, sebacious gland activity, growth of prostate