(Transcribed from Dr. Kalliecharan’s lecture, 31 Mar 2000 by Brian Buschman)
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The broad category of the male reproductive system encompasses the production of sperm and the pathway of it’s ejaculation.
The epithelium of the testes are lined by Sertoli cells and cells of the spermatogenic lineage. The spermatogenic cells at the early stages are in the layers of the walls of the testes adjacent to the lumen. They are in varying stages of development.
Spermatogenesis is divided into three stages:
1) Spermatocytogenesis is the stage where mitosis of the spermatocytes (stem cells) takes place. The mitosis conserves the original chromosome number (2N).
2) Meiosis is when the spermatocytes change into spermatids while their chromosome number is reduced to 1N.
3) Spermiogenesis is when the spermatids differentiate into spermatozoa.
Spermatids are rounded cells that enter spermiogenesis and end up as spermatozoa. The process of sperm production is carried out in three phases.
1) The golgi phase is the phase where the acrosomal vesicle is formed.
2) The acrosomal phase is when the spermatid elongates and the acrosome becomes complete. One of the centrioles grows to form the flagellum with it’s 9+2 arrangement.
3) The maturation phase is characterized by the shedding of excess cytoplasm and the release of the spermatozoa.
Sertoli cells are found at the edge of the lumen. Some have tight junctions between them to form a proactive barrier for cells in the spermatogenic process up till they become spermatids. The Sertoli cells function to:
1) Support, protect and regulate nutrients available to the developing sperm.
2) Uptake the excess cytoplasm by phagocytosis.
3) Secrete testicular fluid and inhibin. Testicular fluid acts to transport the developing sperm towards the rete ductuli efferentes. It also acts to nourish developing sperm. The inhibin is a negative regulator to repress FSH production to act in a negative feedback system.
4) Produce Mullerian inhibiting substance in the male fetus to prevent the development of the paramesonephric duct.
The Sertoli cells are stimulated by FSH to carry out their job of producing androgen binding protein (ABP) and inhibin. ABP binds testosterone to keep it nearby to carry out it’s functions.
These encompass the ducts that are found within the testis and include the tubuli recti, rete testes and ductuli efferentes (in that order).
The seminiferous tubules are loops where spermatids are formed with both ends of the loops emptying into the tubuli recti. It is composed of walls of simple cuboidal epithelia. They empty into rete testes that are histologically similar to the tubuli recti. The main difference for us is that the tubuli recti combine to empty into about ten rete testes.
The rete testes empty into ductuli efferentes that are made of ciliated columnar epithelia and non-ciliated cuboidal cells. The ciliated columnar cells have the purpose of moving the developing sperm towards the ductus epididymis. The cuboidal cells function to absorb the testicular fluid that was secreted by the Sertoli cells. The ductuli efferentes also have a layer of smooth muscle around them.
The ductuli efferentes empty into the ductus epididymis which is the first passage for the sperm outside of the testes. It will them empty into the vas deferens and then to the ductus deferens on it’s way to the prostatic urethra.
The ductus epididymis is made of a pseudostratified columnar epithelia with sterocilia. Below the basal lamina is a smooth muscle layer with loose connective tissue containing capillaries. The epididymis helps digest residual bodies that are left around from the formation of spermatids. It also secretes glycerophospho-choline that inhibits capacitation (the activation of sperm).
They have a pseudostratified columnar epithelia with sterocilia like the epididymis but they have a thick muscular wall with an inner longitudinal, middle circular and outer longitudinal layers. Outside all that is an adventitia.
The accessory glands include the seminal vesicles, the prostate and the bulburethral glands.
The seminal vesicles are not reservoirs for sperm but are a folded set of tubes with pseudostratified columnar epithelia with secretory granules. They have a lamina propria full of elastic fibers. It’s function is to secrete fructose, amino acids, ascorbic acid and prostaglandin to support the sperm.
The prostate is a branched tubuloalveolar gland which empties into secretory ducts that carry it’s production to the prostatic urethra. It has three groups of glands:
1) Mucosal glands that are centrally located.
2) Submucosal glands that secrete glycoproteins which may be calcified with age. These secretions are what are referred to as prostatic concretions.
3) Main glands make acid phosphatase, proteolytic enzymes and other molecules and enzymes to support the sperm.
With age the prostate often undergoes some level of benign hypertrophy which can occlude the urethra. It is present in about 50% of males by the age 50.
Also called Cowper’s glands. They are tubuloalveolar glands of simple cuboidal epithelia. They secrete a clear mucus that acts as a lubricant.
It contains three cylindrical masses of erectile tissue. The two dorsal corpora cavernosa of the penis and one ventral corpus spongiosum. The three are bundles together by a fibrous tunica albugenia. The blood supply of the penis is via a deep artery which branches into nutrient and helicine arteries. The nutrient arteries provide the blood supply that brings nutrients to the penile tissues. The helicine arteries provide the erectile supply to the erective tissues. They have AV shunts that go from the helicine arteries to the deep veins. When these shunts are open the flaccid state is maintained. Under parasympathetic stimulation (S2, 3, 4 keeps the ding-dong off the floor) the AV shunts close and erection is attained.
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