Class 5: Male Reproduction

Question 1

Testis

Answer 1

the male gonad and site of spermatogenesis. Composed of seminiferous tubules.

Question 2

Vas deferens

Answer 2

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.

Question 3

Seminal vesicle

Answer 3

contributes the majority of the fluid volume of the ejaculate (~70%)

Question 4

Prostate

Answer 4

Prostatic secretions also contribute to the fluid volume of the ejaculate (~25%)

Question 5

Epididymis

Answer 5

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.

Question 6

T (testosterone) and DHT (dihydrotestosterone)

Answer 6

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).

Question 7

Interstitial space

Answer 7

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.

Question 8

Seminiferous tubule

Answer 8

• 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).

Question 9

Lumen

Answer 9

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.

Question 10

Adlumenal compartment -

Answer 10

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)

Question 11

Leydig cell

Answer 11

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.

Question 12

Sertoli cell :

Answer 12

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.

Question 13

Spermatogonia

Answer 13

diploid cells (2N,2C) from mitotic division of spermatogonial stem cells

Question 14

Spermatocyte

Answer 14

diploid cells (2N,2C) differentiated from spermatogonia; Primary spermatocyte (2N,2C)–> DNA replication (2N, 4C)–> Meiosis 1–> Secondary spermatocyte (1N,2C)

Question 15

Spermatid

Answer 15

haploid cells (1N,1C) (from Meiosis II of Secondary Spermatocyte)

Question 16

Spermiogenesis:

Answer 16

permatids change shape from round to elongated. Condensation of nucleus - DNA packaging.

Question 17

Blood-testis barrier

Answer 17

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.

Question 18

Vasectomy, IVD

Answer 18

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.

Question 19

Mechanisms of action of male hormonal contraception

Answer 19

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.

Question 20

Challenges for male hormonal

contraception

Answer 20

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.

Question 21

Spermatogonial stem cells-

Answer 21

the SSC’s originate from primordial germ cell during fetal development due to sex differentiation, they continuously renew via mitotic divisions (2N,2C)

Question 22

Basal compartment -

Answer 22

(basal=bottom) the lower compartment where spermatogonial stem cells convert to spermatogonia and then differentiate to primary spermatocytes before traveling through the Blood Testis Barrier into the adlumenal compartment.