Spermatogenesis

Question 1

What is spermatogenesis and where does it occur

Answer 1

= spermatocytogenesis + spermiogenesis

w/in seminiferous tubules (sertoli cells and fluid filled lumen and intersticial leydig cells

Question 2

What is Spermatocytogenesis

Answer 2

cell division of spermatogonia

Question 3

Spermatocytogenesis - what is spermatogonium and process

Answer 3

• 19.4 days
• spermatogonium = a cell produced at early stage information of spermatozoa by spermatozoal division from underdeveloped germinal cells (gonocytes) in base of seminiferous wall
• several MITOTIC divisions produce large no. primary spermatocytes
• 5 different types of spermatogonia = A1,2,3 and B1,2
• division of A1 - produce more stem cell spermatogonia by mitosis to replenish supply for future spermatozoa production and produce committed A1 spermatogonia
• A1 spermatogonia to produce primary spermatocytes divide by mitosis 4 times to produce 16 A2 spermatogonia
• throughout division groups of spermatogonia originating from single A1 stay connected by intercellular bridges
• each A2 spermatogonia divide by mitosis to give 2 B2 differentiated spermatogonia
• B2 divide to form 2 primary spermatocytes

Question 4

Meosis

Answer 4

• meotic divisions produces secondary spermatocytes (haploid) contain either x/y chromosomes
• 19 dyas
• allow exchange of material between chromosomes in dividing cell
• first meotic division involves multiplication and exchange of genetic material = 2 diploid secondary spermatocytes (18.7 days)
• second division having genetic material and production of 2 haploid spermatids per single secondary spermatocyte (0.7 days)

Question 5

Spermiogenesis

Answer 5

= production of sperm

• spermatids develop acrosome, head, mid-piece and tail = differentiate into spermatozoa
• heads bury into sertoli cells and tails in lumen
• relased into lumen and go to epidydimis to mature
• 18.6 days
• 4 phases = golgi, cap, acrosome and maturation
• loss of cytoplasm, changes to nucleus and development of tails

Question 6

Spermiation

Answer 6

• spermatozoa released into lumen of seminiferous tubules
• pass to rete testis and onto epidydimis by rhymich contractions for final maturation
• freed from sertoli cells once mature

Question 7

How long in total

Answer 7

55-57 days

Question 8

Hormones involved

Answer 8

• FSH from spermatogonia to secondary spermatocytes

- testosterone from secondary spermatocytes to spermatozoa

Question 9

Daily sperm output

Time for sperm production and maturation

Answer 9

• 14-19x10^6 sperm/g testes

- 60-90 days

Question 10

where does final maturation of sperm occur and where stored

Answer 10

in head and body of epidydmis

epidydimal tail and proximal ducts deferens

Question 11

what can determine daily sperm output

Answer 11

• parenchymal weight of testes
• estimate weight by total scrotal width
• testicular size is heritable (can estimate DSO)

Question 12

Do stallions stop producing sperm in winter - what happens to sperm production in winter (+study)

Answer 12

No

• size/volume of testes and daily sperm production decrease
• increased melatonin in winter - decrease GnRH and LH
• less testosterone form leydig cells
• less sertoli cells stimulated
• sertoli cells = facilitate progression of germ cells to spermatozoa via direct contact and controlling the environment milieu within seminiferous tubules
• study by Berndtson 1983 = looking at the influence of season found that the concentration of testicular testosterone increased from 228ng/g in December and January to 467ng/g in July