deck_695151 Flashcards
Development of the testis
7th week of gestation: Testes form26th week of gestation: Testes descend into scrotum at thru inguinal canal as the gubernaculum shortens
seminal vesicles, ejaculatory duct, excurrent ducts origin
Mesonephric duct
seminiferous tubules, straight tubules, retes testis origin
Indifferent gonads
prostate origin
Primordium in pelvic urethra
Determination of Sex
1) genetic sex - Y chromosome at time of fertilization2) Gonandal sex - activation of SRY gene3) Hormonal sex - leydig cells produce testosterone 5alpha-reductase - DHT • Sertoli cells produce Mullerian-inhibiting factor
Tunica albuginea
thick dense CT capsule covering each testis divides testes into lobules by septa
Tunica vasculosa
inner looser portion of testicular CT capsule w/ blood vessels
Blood supply to testis
Testicular artery • Pampiniform plexus • VeinsVas deferens w/ blood supplyCremasteric mm. w/ blood supplyVast plexus of arteries to cool blood - counter current heat exchange: warmer blood supplying seminiferous tubules passes cooler blood in plexus • Sperm need slightly lower temperatures for motility
pathway for gamete to travel
Seminiferous tubules - Spermatogenesis (meiosis) and spermiogenesis (maturation)Straight tubules – no spermatogonia or spermatocytes -> empty into retes testisRetes testis (in mediastinum) - efferent ductules - epididymus - vas deferens - ejaculatory duct - merge w/ urethra in prostate
Seminiferous tubules
Leydig cellsSpermatogenic cells Peritubular cells Sertoli cells
Sertoli cells
-supporting or sustentacular cells-do not replicate after puberty (G0)-Columnar epithelium-extensive apical and lateral processes that surround spermatogenic cells -> blood-sperm barrier
Luminal vs basal compartment
barrier formed by sertoli cell processesLuminal compartment – meiotic cells, spermatocytes, post-meiotic cells, spermatidsBasal compartment – mitotic cells, spermatogoniaPhysical compartmentalization Permeability barrier
Exocrine and endocrine secretory function of sertoli cells
• Secrete fluid that facilitates passage of maturing sperm along seminiferous tubules• Secrete androgen-binding protein: binds and concentrates testosterone and DHT in luminal compartment essential in sperm dev.• Secrete inhinin: involved in feedback loop that inhibits FSH release from anterior pit.• Secrete plasminogen activator: converts plasminogen to active hormone plasmin• Secrete transferrin: iron transporting protein
Spermatogenic cells
derived from primordial germ cells (yolk sac)• Spermatogonial cells (mitotic) - on basal lamina• Spermatocytes (meiotic) • Spermatids (post meiotic: mature into sperm) - near tubule lumen
Peritubular cells
specialized smooth muscle cell• Propels maturing gametes out of seminiferous epithelium
Leydig cells
interstitial cells - Synthesize and secrete testosterone• Eosinophilic• Numerous lip drops • Lipofuscin pigment• Distinct rod shaped crystals of Reinke• Extensive SER and Mitochondria with tubular cristae
Hormonal regulation of male reproductive function
• Sertoli cells haveFSH receptors• Leydig cells have LH and estradiol receptors• leydig and serotoli cells communicate
Spermatogenesis
- the process by which spermatogonia develop into sperm- Begins shortly before puberty under rising levels of gonadotropins continues for majority of man’s life - mitosis and meiosis- Spermatogonial phase- Spermatocyte phase- Spermatid phase (spermiogenesis
Spermatogonial phase
spermatogonia/stem cells divide by mitosis to replace themselves and provide a population of committed spermatogonia cells that will undergo meiosis• 3 types of spermatogonia (begin as A dark -> pale -> B -> 1° spermatocytes -> meiosis)
Spermatocyte phase
- spermatocytes undergo meiosis to reduce chromosome # and DNA content producing haploid spermatids• Primary spermatocytes (2N4C) undergo meiosis to reduce both the chromosome number and DNA amount - Crossing over and independent assortment insure genetic diversity of gametes• Secondary spermatocytes (1N2C) -> meitosis 2 lasts a few hours -> spermatids (1N1C)
Spermatid phase
Spermatid undergo extensive remodeling as they differentiate into mature sperm -> 4 stages
Acrosomal cap
contains hyaluronidase, neuramidase, acid phosphatase and acrosin• Like a vesicle• Makes zona pellucida of oocyte permeable- Acrosome reaction -> release of acrosomal enzyme occurs as sperm touches egg
Principal piece
approx. 40 picom and contains the axoneme as well as a dense fibrous sheath of proteins that play a role in directing the beat of flagella
Sperm maturation
• Morphological maturation – in seminiferous tubules: mitosis, meiosis and sperm maturation• Functional maturation – in epididymis as sperm gain motility