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Endocrinology of the male and spermatogenisis - Coggle Diagram
Endocrinology of the male and spermatogenisis
endocrine control/regulation is different than in the female
before spermatozoa can be produced, certain endocrine requirements must be met.
FSH and LH secretion from the anterior lobe of the pituitary
secretion of gonadal steroids (testosterone and estradiol)
adequate secretion of GnRH from the hypothalamus
luteinizing hormone acts on the leydig cells within the testes
successful testies function requires
high concentrations of testosterone in the seminiferous tubule
low concentration of testosterone in a systemic blood
pulsatile GnRH secretion (every 3-6 hours)
pulsatile discharge of LH is important for normal testicular function
prevents sustained concentrations of LH to which the Leydig cells become refractory (unresponsive or not yielding to treatment)
adequate LH receptors in Leydig cells
normally, intratesticular concentrations of testosterone are 100-599 times higher than that of systemic blood flow
production of normal numbers of fertile spermatozoa requires
mitotic divisions of spermatogonia
meiotic divisions resulting in haploid spermatids
endocrine regulation of the testis
morphologic transformation of spermatids into spermatozoa
leydig cells
testes also secrete estradiol and other estrogens
male equivalent of the follicular theca interna cells
sertoli cells
sertoli cells are the male equivalent of the follicular granulosal cell
convert testosterone to estradiol utilizing a mechanism identical to the granulosal cells of the antral follicule in the female
high concentrations of estradiol result in suppression of GnRH and LH discharges
goals of spermatogenesis are to
provide an immulogically privileged sites where developing germ cells are not destroyed by the male's immune system
provide billons of sperm each day (domestic animals) to maximize reproduction by both natural service and artificial insemination
provide genetic diversity
provide a continual supply oof male gametes (up to decades) through stem cell renewal
spermatogenesis is the process of producing spermatozoa
spermatogenisis: takes place entirely within the seminiferous tubules and consists of all cell divisions and morphologic changes that occur to developing germ cells
meiotic phase
conclusion of meiotic phase produces haploid
differentiation phase
no further cell divisions take place during this phase
proliferation phase
important part is stme cell renewal
most immature germ cells (spermatogonia are located at the periphery of a seminiferous tubule near the basement membrane)
proliferation generates spermatogonia that are committed to become more advanced cell types
specialized diploid cells are located in the basal compartment of the seminiferous epithelium
there are 3 types of spermatogonia
I-spermatagonia
B-spermatogonia
A-spermatogonia
undergoes several mitotic divisions
meiotic divisions produce haploid spermatids
crossing-over results in a random assortment of different segments of each chormosomes
prophase of the first miotic division insures genetic heterogeneity and that each secondary spermatocyte and that which secondary spermatocyte and subsequently each spermatid will be genetically unique
secondary spermatocyte resulting from the first meiotic division of a primary spermatocyte is short-lived
differentiation produces a highly sophisticated, self-propelled package of enzymes and DNA
role of spermatozoon is to deliver the male's genetic material to an oocyte during fertilization
differentiation consists of
cap phase: acrosomic vesicle spreading over the nucleus
acrosomal phase: nuclear and cytoplasmic elongation
maturation phase: final assembly that forms a spermatozoon
golgi phase: acrosomic vesicle formation
spermatozoa are released continually into lumen of the seminiferous tubules
spermatozoa are released continually into the lumen of the seminiferous tubules
female gamete supply is produced entirely before birth
6-12 weeks are required before restoration of normal spermatogenesis can be accomplished
cycle of the seminiferous epithelium
progression though a complete series of cellular associations (stages) at one location along a seminiferous tubule
germ cells generations are cells of the same type located at one site within the seminiferous epithelium
stages of the cycle are arbitrarily defined cellular associations that transition one to the next at predictable intervals
lifespan of cells and duration of the cycle vary among species
types of abnormal spermatozoa
this i based off of the shape
this can cause reduced fertility, but some has not affect or little to none
usually originate in the testes because case of faulty differentiation or in the epididymis transit and/or maturation
the major steps of artificial insemination are
preservation and extension of sperm
insemination of the female
collection of semen from the male
right after collection of semen info needed
percentage of motile sperm
concentration of spermatozoa in the ejaculation (sperm/mL ejaculation)
ejaculation volume
vitro preservation is obligatory for successful AI
preservation and dilution of sperm requires an environment that minimizes death of sperm
need to know the concentration of the sperm in the ejaculated so they know the number
evaluation of the semen is needed before diluting
total number of sperm in ejaculation
high percentage of motile sperm indicates good quiality
good seminal extenders must:
be isotonic
be good buffers
marked changes in pH
cryprotectants: materials that protect the cells against cold famage that would occur between 0 and -50degreesC
glycerol
dimethyl sulfide (DMSO)
spermatozoa have no anabolic capability
minimize cold damage ("cold shock")
provide appropriate nutrients
prevent microbial growth
maintain viability
be relatively low in cost
ejaculated semen is not sterile
bacteria can be found in the sheath and on the penis, occasionally in the urethra and vesicular glands
semen contains variety of microorganisms
prevention of spermatozoa can be accomplished using two methods
freezing and thawing