Lect. 3 - Gametogenesis III Flashcards
List the stages of spermatogenesis and the major meiotic events that occur at each stage.
- spermatogonium - DNA replication: 2N, 4c
- Primary spermatocyte: 1st meiotic division in progress - 2n, 4c
- 2 secondary spermatocytes - second meiotic division in progress; 1n, 2c
- 4 spermatids - immature haploid gametes; 1n, 1c
- 4 spermatozoa - haploid gametes; 1n, 1c
Where are the Leydig cells located and what is their function?
Interstitial cells located in the testis - produce testosterone.
What are the 4 stages of spermiogeneis?
Golgi phase, cap phase, acrosomal phase, maturation phase.
Golgi phase
proacrosomal and acrosomal vesicles
Cap phase
mature acrosome forms a cap over the nucleus
Acrosomal Phase
rotation of sperm so acrosomal pole faces wall of seminiferous tubule - cytoplasm displaced toward tail
Maturation phase
completion of flagellum and nuclear condensation
What is the location of Sertoli cells?
They form an immunological barrier b/w the forming sperm cells and the rest of the body and spermatogonia
Functions of the sertoli cells
Physical support and maintenance, maintain and coordinate spermatogenesis.
Secrete estrogen, inhibit and anti-Mullerian factor
Maintain blood testis barrier
Secrete tubular fluid
Phagocytize residual bodies of sperm cells
Sertoli cells and blood testis barrier
Sertoli cells form an immunologic barrier b/w the forming sperm cells and the rest of the body and spermatogonia
- surface adhesion compelxes bind surfaces of Sertoli cells to late spermatids
- they also break down and release spermatids into lumen
- laminin fragments from surface adhesion complexes plus sytokines and proteinase break down the tight-junctional proteins of the blood testis barrier and allow developing spermatocytes to move closer to the lumen
What role does testosterone play in the blood-testis barrier?
It stimulates the formation of a new blood-testis barrier closer to the basal lamina
What is the action of LH on interstitial cells and Sertoli cells w/ regard to sperm cell production?
LH (secreted by anterior pituitary in response to GnRH from hypothalamus) binds to LH receptors on interstitial cells of Leydig
*testosterone is synthesized by Leydig cells from cholesterol and is then carried via the blood to Sertoli cells (binds to cytoplasmic receptors) and to secondary sexual tissues (prostate, seminal vesicle epididymis, ductus deferens, peni, scrotum)
what is the synonymous process to oogenesis in male ?
spermatogenesis
What are the two types of spermatogonia?
type a: stem cells
Type b: leave mitotic cycle and enter meiotic cycle under influence of RA
what do primary oocyte mature from and what is their ploidy?
from type B spermatogonia and they are 2N
