Spermatogenesis Flashcards
spermatogenesis
mitosis (spermatocytogenesis)
meiosis
spermatogenesis
role of testes
production of spermatozoa
production of various hormones
Spermatogenesis
formation of spermatozoa
from spermatogonia
Spermatogenesis definition
spermatocytogenesis + meiosis + spermatogenesis
Spermatocytogenesis
proliferation
mitotic divisions involving proliferation and maintenance of spermatogonia
meiosis
reduction of genetic material, involves primary and secondary spermatocytes
spermatogenesis
differentiation
morphologic transformation of spherical spermatids into spermatozoa
Generation of Spermatogonia (basal)
from basement membrane
A1-A2-A3-A4- I (intermediate) - B (proliferation)
number of divisions= species dependent
Meiosis phase (Adluminal)
2 phases- first division (primary spermatocyte to secondary spermatocyte)
2nd division= secondary spermatocytes to spermatids
Differentiation phase (Adluminal)
spermatids develop and differentiate, travel to lumen
Phases of spermiogenesis
Golgi (1-3)= formation of acrostic granule
cap (4-7) = growth of acrostic head cap
Acrosome (8-12) = condensation, elongation and shaping
Maturation (13-14) = final formation of flagellum and neck piece, final condensation and shaping of nucleus
Golgi phase
golgi apparatus produces proacrosomic granules and centrioles begin to migrate
acrostic vesicle forms along with granule and centrioles continue moving
the cap phase
acrosomic vesicle and granules form and the AX develops further
The acrosomal phase
Annulus now present along with Manchete and mitochondria
elongate further
the maturation phase
Annulus still present and now have distinct middle, head, neck, and principle piece
endocrine regulation of the testis function
secretion of GnRH from the hypothalamus
FSH and LH secretion from the ant. pituitary
testosterone production by Leydig cells
inhibit and active production by sertoli cells
Negative feedback
inhibit neg. feedback on Ant. pituitary
testosterone neg. feedback on both hypothalamus and anterior pituitary
Ant. Pituitary hormone production
LH- leydig cells- testosterone- spermatogenesis
FSH- sertoli cells- spermatogenesis
FSH-sertoli cells- inhibin- - feedback
Stages of the equine seminiferous epithelium and their germ cell types
lots of different types, a spermatogonia may be found in all 8 stages
spermatogonia may be found in stages IV and V
Cellular association and animals
more cells associated with smaller animals
Spermatogenic cycle
complete series of successive cellular associations (stages) in one seminiferous tubule
spermatogenic wave
the distribution of the stages along the length go the tubule in the wave
if the whole length of the seminiferous tubule is viewed at any given time
Duration of the cycle of seminiferous epithelium and spermatogenesis
Dog and Bull have longest cycle with the dog reaching 54.4 spermatogenesis and the bull reaching 61
man has the greatest value
boar= shortest cycle
epididymis role
low disulfide cross linking (head)
moderate to high degree of disulfide crosslinking (body)
high disulfide cross linking (tail)
***all condensation of chromatin
translocation of cytoplasmic droplet- proximal cytoplasmic droplet (head), distal droplet at tail
Sperm chromatin packing in somatic and sperm nucleus
Somatic- DNA wrapped around histone center forming nucleosome which multiple join together forming chromatin fiber (solenoid, supercoiled)
Sperm- minor and major groove intertwine (protamine) via disulfide cross linking which then continue to add up forming chromatin fiber and then a chromatin fiber with a side by side linear array
Anisogamy
difference in size of male and female gametes
shape of spermatozoa
Bull= longest tail followed by boar, ram and then horse
man is smallest head and tail, rat is hook with extremely long tail and cock is straight and thin which very long postacrosomal region
sperm cell head morphology
at tip= apical segment which plasma membrane followed by acrosome contents mostly in principle segment,
surrounded by outer and inner acrosomal membrane with plasma around entire sperm apical, principal and equatorial segments
then in the postacrosomal region there are nucleus and nuclear membrane
Sperm tail
mitochondrial helix near posterior head and fibrous helix within inside
Axioneme (9x2) + 2 = outside has 9 groups of 2 subfigure which dynein arm and spokes attached to the central sheath and central droplet
the outer dense fibers are surrounded by fibrous sheath (which is the 9) and then there are longitudinal column of the fibrous sheath on outside (+2)
sperm processing
high speed manufacturing - testis
finishing shops- fluid absorption (membrane changes, nuclear and flagellar stabilization, motility and cytoplasmic droplet translocation) - epididymis head and body
warehouse and shipping (storage, spermatozoa for 5-10 ejaculations and smooth muscle contractions upon sexual stimulation) - epididymis tail
