- Is the thick fibrous connective tissue capsule of the testis.
- Is thickened posteriorly to form the mediastinum testis from which connective tissue septa arise to divide the organ into approximately 250 compartments (lobuli testis).
- Are pyramidal-shaped incomplete compartments that intercommunicate.
- Contain from 1 to 4 seminiferous tubules each, embedded in a meshwork of loose connective tissue where nerves, vessels, and scattered interstitial cells of Leydig are present.
Interstitial Cells of Leydig
- Are round to polygonal in shape, possessed a large central nucleus, many mitochondria, a well-developed Golgi apparatus, smooth endoplasmic reticulum, and many lipid droplets.
- Are endocrine cells that produce the male sex hormone testosterone, when stimulated by luteinizing hormone (interstitial cell stimulating hormone) from the pituitary gland.
- Are the sites where spermatozoa are produced.
- Are lined by a complex, stratified epithelium.
- Are enveloped by a fibrous connective tissue tunic, composed of several layers of fibroblasts. Myoid cells, resembling smooth muscle, are present in the inner layer of some species
- Have a narrow lumen lined by a simple cuboidal epithelium.
- Lead into the rete testis, a network of epithelial-lined channels located in the mediastinum.
Lead from the rete testis into the epididymis.
- Is composed of two different types of cells, the spermatogenic cells from which the germ cells eventually develop and the Sertoli cells, which support and provide nutrition to the spermatogenic cells.
- Is 4 to 8 cell layers thick.
- The division of the spermatogonia to provide a continuous supply of cells that will give rise to primary spermatocytes.
- Is cytodifferentiation and transformation of spermatids to form spermatozoa.
What cells form the blood - testis barrier?
What are the functions of Sertoli cells?
- Support, protect, and nourish developing spermatozoa.
- Phagocytose excess cytoplasm discarded by spermatids in the process of spermiogenesis.
- Secrete a fluid into the seminiferous tubules that transports spermatozoa to the genital ducts.
- Contain FSH receptors and under FSH influence synthesize androgen-binding protein (ABP) that binds testosterone, concentrating it to permit sperm maturation.
- Secrete inhibin, a hormone that inhibits synthesis and release of FSH from the anterior pituitary.
- Include several characteristic cell types in the seminiferous epithelium: spermatogonia, primary spermatocytes, secondary spermatocytes, spermatids, and spermatozoa.
- Each of these cells represents a distinct stage in the differentiation of male germ cells. The entire process is known as spermatogenesis.
Spermatogenesis - List the 3 phases
- In man takes approximately 74 days
- Its cell divisions are unusual, in that the daughter cells remain connected to each other via intercellular bridges (forming a syncytium).
- Are the diploid germ cells that sit upon the basal lamina.
Are of three types:
- Pale type A - Euchromatic
- Dark type A - Heerochromatic
- Type B.
Pale Type A
At puberty these cells undergo mitosis and give rise to either more pale type A spermatogonia (to maintain the supply of spermatogonia) or type B spermatogonia (which undergo mitosis and give rise to primary spermatocytes).
Dark Type A