Flashcards in Class 5: Male Reproduction Deck (22):
the male gonad and site of spermatogenesis. Composed of seminiferous tubules.
They transport sperm from the epididymis in anticipation of ejaculation. Primary function is to transport mature spermatazoa and seminal vesicle secretions to the prostatic urethra prior to ejaculation.
contributes the majority of the fluid volume of the ejaculate (~70%)
Prostatic secretions also contribute to the fluid volume of the ejaculate (~25%)
one single coiled tube that leads out of the testis. The function of the epididymis is to bring testicular spermatozoa, that are non-motile and incapable of fertilization, to functional maturity. Sperm are stored in the tail of the epididymis.
T (testosterone) and DHT (dihydrotestosterone)
The DHT conversion is catalyzed by 5 a-reductase (the pharma intervention is to inhibit 5 a-reductase)
Sertoli cells can help convert DHT or estrogen from testosterone (T).
the fluid filled areas that surround the cells of a given tissue. Interstitial cells are the cells of the connective tissue surrounding the ovary or the testis (leydig cells) which furnish the internal secretion of those structures.
- Spermatogenesis occurs within the seminiferous tubules which make up the testis– the process whereby germ cells progress from haploid cells (spermatogonia) to meiotic cells (spermatocytes) to diploid cells (spermatids).
the inner cavity or canal of an organ; germ cells (primary spermatocytes) move through the seminiferous tubules from the basal compartment to the adlumenal compartment.
Adlumenal compartment -
Destination of primary spermatocytes in the seminiferous tubule - have to pass through barriers to slowly move up the tubule. Once in the adlumenal compartment, primary spermatocytes start to move through meiotic prophase I → meiotic recombination → secondary spermatocytes complete meiosis II and become spermatids (1N, 1C)
Interstitial cells within the Testis. (target cell for LH, have the LH-Receptor) LH will result in increased testosterone production, some secreted into blood stream (endocrine) for secondary sex characteristics. Some will go to Seminiferous tubules (paracrine) to support spermatogenesis., some go back onto leydig cell (autocrine) to support cell functions.
Sertoli cell :
Called "Nurse cells" because main function is to nurture developing sperm cells throughout spermatogenesis.
Sertoli cells express the androgen receptor. The action of the AR leads to expression of the FSH receptor.
Target cell for FSH, have FSH-R leads to new RNA and protein synthesis. Stimulation of fxn that support spermatogenesis.
Sertoli cells shuttle testosterone into the fluid in the lumen of the seminiferous tubule. Can also make estrogen and dihydrotestosterone (DHT) form testosterone.
diploid cells (2N,2C) from mitotic division of spermatogonial stem cells
diploid cells (2N,2C) differentiated from spermatogonia; Primary spermatocyte (2N,2C)--> DNA replication (2N, 4C)--> Meiosis 1--> Secondary spermatocyte (1N,2C)
haploid cells (1N,1C) (from Meiosis II of Secondary Spermatocyte)
permatids change shape from round to elongated. Condensation of nucleus - DNA packaging.
formed between Sertoli cells of the seminiferous tubule. (A more correct name would be sertoli-cell barrier.) The barrier is formed by tight junctions - made of specialized cytoskeletal structures and sertoli cell-sertoli cell connections. A temporary disruption of tight junctions allows the spermatocyte to move from the basal compartment to the adjumenal compartment.
Both function by blocking the vas deferens and therefore keeping sperm out of the ejaculate. Vasectomy cuts and seals vas deferens, considered irreversible. IVD (intra vas device) is a vas deferens plug. Thought to be more easily reversed.
Mechanisms of action of male hormonal contraception
Works by negative feedback through the introduction of an exogenous hormone similar to female contraception, suppressing gonadotropins (LH and FSH) and inhibiting spermatogenesis. LH normally acts on Leydig cells to stimulate testosterone production. FSH normally acts on Sertoli cells to support spermatogenesis. Reduced LH and FSH suppress spermatogenesis and reduce sperm count.
Challenges for male hormonal
Significant variation from patient-to-patient in responsiveness and differences between ethnic groups. To contrast to female hormonal contraception - if women take their pill faithfully ovulation will not occur. With men, sperm count is reduced, but only in some men are they azoospermic.
Spermatogonial stem cells-
the SSC’s originate from primordial germ cell during fetal development due to sex differentiation, they continuously renew via mitotic divisions (2N,2C)