Week 4: Spermatogenesis

Question 1

Anatomy of the testis

Answer 1

• divided into 2 compartments
• surrounded by tunica albuginea
  1. Seminiferous tubules
  2. Interstitium
• contains Leydig cells that synthesize testosterone

Question 2

Types of cells in seminiferous tubules

Answer 2

1. spermatogonia: stem cell of spermatozoa. adjacent to basal lamina
2. primary spermatocytes: large cells, coarse chromatin. 2n with 4 copies of DNA
3. secondary spermatocytes: completed first meiotic division. Haploid with 2 copies of DNA
4. Spermatids: completed meiosis. Located close to lumen. Still circular cell
5. Spermatozoa: final cellular product of spermatogenesis
6. Sertoli cells: nurse cells, has tight junctions separating haploid and diploid cells

Question 3

Role of Sertoli cells

Answer 3

• create basal and adluminal compartments via tight junctions.Creates blood-testis barrier to protect haploid cells from immune system
• phagocytose cytoplasm from spermatids
• synthesize inhibin and androgen binding protein in response to FSH. ABP concentrates testosterone in testis for spermatogensis

Question 4

Spermiogenesis

Answer 4

• conversion of spermatids to spermatozoa
• occurs while spermatids embedded within invaginations in Sertoli cells
• nuclear condensation, nucleus capped by golgi-derived acrosomal cap, mitochondria line up behind the head

Question 5

extratesticular sperm transport

Answer 5

• spermatozoa released into seminiferous tubule lumen, and move through rate testis (empty space) and efferent ductules (festooned appearance) via fluid flow
  1. epididymis -simple columnar with stereocilia
• absorptive and secretory functions
  2. vas deferens
• pseudostratified columnar epithelium surrounded by thick layers of smooth muscle
• in spermatic cord is counter current heat exchange to allow arterial blood to be cooled by venous blood

Question 6

Male accessory sex glands

Answer 6

1. seminal vesicles: highly infolded structure lined by simple epithelium
   - smooth muscle expels lumenal contents during ejactulation
2. prostate
   - has 5a reductase to convert testosterone to DHT
   - with age can have calcified concretions, benign
3. Bulbourethral glands
   - erection achieved by increased blood flow into corpora cavernous
   - dense CT (tunica albuginea surrounded corpus cavernous to provide rigid scaffolding
   - parasympathetics cause relaxation of SM, diverts arterial blood flow into corpus cavernosum