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Endocrinology of the male and spermatogenisis - Coggle Diagram
Endocrinology of the male and spermatogenisis
Endocrin control/ regulation
Successful testis function requires: pulsatile GnRH secretion (every 3-6 hours), high concentrations of testosterone in the seminiferous tubule, low concentrations of testosterone in systemic blood, adequate LH receptors in Leydig cells
LH acts on Leydig cells- when LH binds to receptors Leydig cells synthesize progesterone which can be converted to testosterone
Leydig cells are the male equivalent of the follicular theca interna cells
Sertoli cells are the male equivalent of follicular granulosa cells
Endocrine requirements 1) adequate secretion of GnRH from the hypothalamus, 2) FSH and LH secretion from the anterior lobe of the pituitary, 3) secretion of gonadal steroids (testosterone and estradiol)
Production of normal numbers of fertile spermatozoa require: endocrine regulation of the testis, mitotic divisions of spermatogonia, meiotic divisions resulting in haploid spermatids, morphologic transformation of spermatids into spermotozoa
Sertoli cells - convert testosterone to estradiol
The goals of spermatogenisis are to:
provide a continuous supply of male gametes (up to decades) through stem cell renewal
provide genetic diversity
provide billions of sperm each day (domestic animals) to maximize reproduction by both natural service and artificial insemination
Steps of artificial insemination are: collection of semen from the male, preservation and extension of sperm, insemination of female
Immediately after collection the following information is needed: ejaculate volume, concentration of spermatozoa in the ejaculate (sperm/ mL ejaculate), percentage of motile sperm
Good seminal extenders must: be isotonic, be good buffers, minimize cold damage ("cold shock"), provide appropriate nutrients, prevent microbial growth, maintain viability, be relatively low cost
provide an immunologically privileged site where developing germ cells are not destroyed by the males immune system
Spermatogenisis
spermatogenisis = proliferation + meiosis + differentiation
Differentiation consists of: Golgi phase, cap phase, acrosomal phase, maturation phase
The golgi phase= acrosomic vesicle formation
The cap phase = acrosomic vesicle spreading over the nucleus
The acrosomal phase = nuclear and cytoplasmic elongation
The maturation phase = final assembly that forms spermatozoon
Spermatozoa = head + tail
head = nucleus + acrosome + post-nuclear cap
Tail = middle piece + principle piece + terminal piece
The sperm tail is a self-powered flagellum
In order to comprehend the cycle of the seminiferous epithelium you must first understand: cellular generations, stages of the cycle, duration of one cycle, how the cycle is repeated
Germ cell generations are cells of the same type located at one site within the seminiferous epithelium
Stage = specific cellular associations
stages of the cycle are arbitrarily defined cellular associations that transition one to the next at predictable intervals
stage duration = time required for completion of one stage (cell association)
cycle= progression through sequence of all stages
cycle duration= time required to complete one cycle
Lifespan of cells and duration of the cycle vary among species
