Male reprpduction Flashcards
Seminiferous Tubules
Located in the lobules of the testis. Convoluted loops, open at each end, in a loose CT (interstitial) which contains nerves, vessels, and interstitial (Leydig) cells. The combined length of the seminiferous tubules in one testis is about 200 meters. Production of the spermatozoa occurs here. Peritubular (myeloid) cells are smooth muscle-like and mildly contract the tubules.
Spermatogonia
Primitive germ cells resting on the basal lamina of the complex epithelium of the seminifrous tubules and at puberty begin to divide. Daughter cells will either remain as stem cell spermatogonia or become progenitor spermatogonia which will continue to divide and differentiate into primary spermatocytes.
Progenitor Spermatogonia
Divide and differentiate into primary spermatocytes.
Primary Spermatocytes
The first to proceed through meiosis I and become haploid secondary spermatocytes with two chromatids.
Secondary Spermatocytes
Two chromatids and goes through meiosis II to create haploid spermatids. Lifespan is so short it is not usually seen on slides.
Spermatids
Will not divide further but will be transformed into mature spermatozoa by spermatogenesis.
Spermatozoa
Mature. The cytoplasm division was never complete so they finally shed their extra cytoplasm and the bridges connecting them.
Spermatogenesis
Requires lower than normal temperature 37 degrees C. Shepherded along and controlled by the Seritoli cell. Formation of an acrosome, nuclear condensation/elongation, flagellum, loss of cytoplasm. The nuclei of the developing spematazoa point towards the base of the seminiferous tubule with their flagella pointing into the lumen. Mitochondria spiral around the proximal end of the flagellum for energy. Excess cytoplasm is shed as residual bodies.
Cryptorchid Testis
Undescended. Impaired spermatogenic potential and increased risk of cancer.
Sertoli Cell
Resides in the seminiferous epithelium and shepherds along spermatogenesis. The real epithelium of the seminiferous tubule attached to the basal lamina and nurtures cells. Extend inward to the lumen of the tubule. Euchromatic nuclei and distinct nucleus. Bound by tight junctions at their basolateral margins dividing the epithelium into basal and luminal compartments. Phagocytose residual body and failed differentiation. They also are sensitive to FSH which tells them to synthesize and secrete androgen-binding protein ABP which helps concentrate testosterone in the lumen of the seminiferous tubule for spermatogenesis.
Basal Compartment
Spermatogonia and early primary spermatocytes reside here. Between the basal lamina and the junctional complexes of the Sertoli cells. Prior to onset of meiosis I, a primary spermatocyte must migrate to the luminal side of the junctional complex where the remainder of the spermatogenesis takes place in the region protected from immunological attack.
Luminal Compartment
Remainder of spermatogenesis and protection from immunologic attack.
Blood-Testes Barrier
Junctional complexes formed by the Sertoli cells. Large molecules in the blood cannot cross. Fluid in the seminiferous tubules varies from the blood. Exchange of nutrients to and metabolites from the developing spermatogenic cells is a function of the Sertoli cells. The cytoplasmic bridges connecting the germ cells expedite. Haploid spermatids would be attacked but they are protected.
Acrosome
Hydrolytic enzymes that permit the sperm to penetrate the corona radiata and zona pellucida.
Residual Body
Excess cytoplasm shed and phagocytosed by Sertoli cells.
