IPHY 4440 1st Edition Lecture 21Outline of Last Lecture I. Clinical aspects of adrenal disorders continued II. Development of the Reproductive System III. Sex differentiation IV. Disorders of human differentiationOutline of Current Lecture II. Nature’s experimentIII. Male reproductive system IV. Regulation of testis function V. Other actions of testosteroneCurrent LectureI. Nature’s experiment: the spotted hyena A. The spotted hyena (Crocuta crocuta)•Females have normal ovaries•Ovaries produce high levels of androstenedione•Females have male genitalia: one canal, three functions  urination, partuition, and copulation (give birth through pseudopenis) Small opening (1.5 kg fetus in clitoris): Rips its way out through CT and mother can die when in labor and delivery. Same as passing a 3.8 lb kidney stone - Also have difficulty mating II. Male reproductive system A. Testicular structure- Seminiferous tubule  Spermatogenesis takes place, surround by connectivetissue layer that has no blood vessels that penetrate the tubules - Leydig cells steroidogenic, primary job has to do with spermogenesis- Sertoli cells  support spermatogenesis - Lumen of seminiferous tubule contains germ cells (sperm)These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.B. Germ cells: Spermatogonia (diploid stage) undergoes spermatogenesis (mitosis and meiosis)  Spermatid (haploid stage) undergoes spermiogenesis (differentiation and elongation) spermatozoa (sperm) (haploid stage) *Cells at various stages to becoming mature sperm * Spermaotgonia: Like stem cells that can divide indefinitely for a long period of time, every single ejaculation so need spermatogonia to replenish the lost sperm and are diploid two sets of chromosomes * Sertoli cells aka Sustentacular cells nurture the sperm by tight junctions that make the blood-testis barrierNote: No blood can access the germ cells unless they go through the sertoli cellsBTB: important because immune cells will never seen sperm so may launch attack on sperm -autoimmune if they see a sperm cell as foreign C. Extra notes: Least mature germ cells furthest away from lumen. When get more mature then they get closer to the lumen.- How do they get released from sertoli cells? Has to undergo sperimiation: release from sertoli cells (After spermiation go into the lumen and now can go through male reproductive tract Note: Ejaculation is sperm leaving the body D. Interstitial cells aka Leydig cells - Located between tubule- Testosterone secretion: Main function is to produce TIII. Regulation of testis function A. LH: increases synthesis of testosterone, increases spermiation= release of sperm into lumen- not ejaculation - LH doesn’t directly increase spermiation but must increase Testosterone first and must have LH to have testosterone- Rely on instructions coming from the pituitary B. FSH: stimulates spermatogonial proliferation (mitosis) but no FSH receptors on gonia instead FSH directly stimulates Sertoli cells (have FSH receptor), secrete paracrine factors to increase spermatogonia- Stimulates the synthesis of aromatase synthesis of E2 by the leydig and sertoli cells - Stimulates synthesis of cytoskeletal elements- Stimulates the synthesis of STP= Steroidogenesis-stimulating protein that increases LH sensitivity of leydig cells and increase steroid production- Stimulates the synthesis of inhibins- Negative feedback at pituitary for FSH- Stimulates the synthesis of androgen-binding protein- ABP binds to testosterone: transports T to epididymis to increase epididymal secretions to increase sperm viability and motilityIV. Other actions of testosterone1) Simulates secondary sex characteristics: beard, muscle mass2) Simulates reproductive behavior: may involve conversion to E2 or DHT3) Stimulates