Spermatogenesis
The term spermatogenesis describe and include all the process involve in the production of gametes. Spermatogenesis is the process by which precursor germ cell turned spermatogonea undergo a complex series of division to give rise to spermatozoa . Spermatogenesis take place in the tubular compartment, consisting of the seminiferious tubules. For quantitatively and qualitatively normal production of sperms, the integrity of tubular compartments, is necessary. The function of testis and of its other compartments are governed by the by the hypothalamus and the pituitary gland. These endocrine effects are mediated and attuned at the testicular level by local control mechanism. The interstitial compartment between the seminiferious tubules plays and inevitable role in regulating the over all process of spermatogenesis till ejaculation.
The Hypothalamo-Pituitary System ; Functional organization
The successful initiation of testicular function is dependent on the hypothalamic secretion of GnRH which in turn stimulates FSH and LH to act on the testis from anterior pituitary. These action initiate spermatogenesis and testosterone production. Due to pulsatile nature of GnRH secretion, the release of gonadotropins also occurs in discreet peaks ,more obvious in case of LH , because of its shorter half life (20 minutes) as compared to FSH in circulation . Where as the activation of GPR54 receptor,located on the surface of the GnRH neurons are responsible for the secration of GnRH. The function of pituitary gland is also under control of gonadal steroids and peptides eithe directly or via hypothalamus.
LH and FSH
LH targets the leydig cells to stimulate androgen biosynthesis, and the resulting androgen ( testosterone and its androgen metabolites ) act on receptor within the seminiferious epithelium to stimulate and report spermatogenesis.FSH target receptor in the sertoli cells directly to support spermatogenesis . however the role of either endocrine factors, such as vitamin A and its metabolic retionoic acid,are emerging while both androgen and FSH are required for optimal spermatogenesis, spermatogenesis relies on the local production of growth factors, signaling molecules and other intransic mechanism.
Teststerone
Leydig cells are the site of production of androgen in the Testis,The synthesis and secretion both are under control of pituitary LH.In the absence of androgen, spermatogenesis would not produce beyond meiosis. Testosterone is the most abundent androgen in the blood.In normal healthy man about 66-7 grams of testosterone is synthesized daily by leydig cells in the intestinal sapace of the testis. The transformation of testosterone into DHT take place in prostrate. A small amount of testosterone is store in the testis because very high level does not support spermatogenesis. Testosterone bind eith albumin nor sex harmone binding globulin for the transportation (SHBG) for the transportation in the plasma produced by hypatocytes
Feedback Mechanism
At the onset of puberty, the hypothalamus cause the release of FSH and LH into the male system for the first time. FSH enters the testes and stimulate the sertoli cells to begin facilitating spermatogenesis using negative feedback, as illustrated. Testosterone the hormone responsible for the secondry sexual characteristic that devlop in the male during adolescence, stimulate spermatogenesis
In response to FSH release, which stimulate sertoli cell sertoli cell produce two factor- one inhabition ( which regulate the production of FSH from pituatiary ) second androgen binding- globulin (ABG)
Leydig Cells
Leydig cells are present in the interstitial compartment of testes. These cells are approx. A class of hormone called androgen and peptide hormones INSL-3 are secreted by leydig cell under the influence of Leueinizing hormones. A class of hormone called androgen (19 c steroid ) and peptide hormones INSL-3 are secreted by the Leydig cell under the influence of Leteinizing hormones (LH) stimulated by anterior pituitary.
Sertoli Cells
Sertoli Cells are found within the germinal epithelium of basal membrane. These cells represent approximately 35-40%of total volume of germinal epithelium.
Stage Of Spermatogenesis
There are following stage of spermatogenesis
* Spermatogoniogenesis (mitosis)
* Spermatidogenesis (meiosis1 and meiosis 2)
* spermiogenesis
* spermiation
Mitotic Division
Spermatocytogenesis term is refered to as the male gametocytogenesis and result in the formation of spermatocytes possessing half the normal complement of the genetic material . spermatocytogenesis starts with the mitotic division of diploid spermatogonium ( from the basal compartment of the seminiferious tubules ) and produces two primery spermatocytes ( diploid intermediate cells).
Spermatidogenesis
The formation of spermatids from secondary spermatocytes is called spermatidogenesis
Spermiogenesis and Spermiation
During spermiogenesis the spermatids begin to form a tail by growing microtubules on one of the centrioles , which turns into basal body. These microtubules form an axonema. Later the centriole is modified in the process of centrosome reduction
Semen Analysis
Semen primery atributes two parameters
* The total number of spermatozoa present in the ejaculate,which reflects the proper functioning of testes and post testicular duct system
* The total fluid volume assures the secretory activity of various accessory gland
The first cohert of semen ejaculate hjas prosthatic fraction and basically sperm rich. There is noticeable difference in the quality of sperm ejaculated in a laboratory setup
Semen Analysis
It can divided in two steps ;
* Macroscopic Analysis
* Microscopic Analysis
* Macroscopic Analysis
Collected semensample should be kept at 370C for 5 minutes, volume, PH apperence pf the semen sample, liquification should be mesured between 30 to 60 minutes
Volume To mesure the ideal volume of collectd semen saampe
Liquefaction The time at which the heterogenous mass of fluid starts to liquify at room tempreture is known as liquification time
PH PH should me measured after 30 minutes and consensus value of 7.2 is the lower threshold
Microscopic Analysis
Microscopic analysis can be done by making a wet preparation of sample under phase contrast microscope
* Aggregation
* Agglutination
* Sperm mortility
* Progressive mortality ( PR)
* Non progressive mortality (NP)
* Immotility
* Sperm concentration and number
* Staining
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