Spermatogenesis and accessory sex glands

Question 1

Anatomy of spermatozoan and process of spermatogenesis 1

Answer 1

• Order of movement of sperm: seminiferous tubules-> rete ducts-> efferent ducts-> epididymis (spermatozoa move thru ducts via fluid flow)
• Spermatogonia: stem cell from which spermatozoa are derived (up against basal lamina)
• Spermatogonia are adjacent to basal lamina of the seminiferous tubules (tubules look like stratified epithelium, but are really rows of spermatozoa at different stages of development)
• Spermatogonia replicate into one daughter spermatogonia (to maintain the stem cell pop) and one daughter primary spermatocytes (both are 2n)
• Primary spermatocytes (already have replicated DNA) divide into secondary spermatocytes (1n, 2c)

Question 2

Anatomy of spermatozoan and process of spermatogenesis 2

Answer 2

• Secondary spermatocytes undergo second meiotic division to be spermatids (1n, 1c), these cells are located close to the lumen of the tubule
• Spermatids are released from the seminiferous epithelium into the lumen and become spermatozoa, which will mature in the epididymis
• Anatomy of spermatozoa: head contains acrosomal cap (made in golgi phase) and nuclear contents, middle piece contains mito, tail is flagellum
• Since spermatozoa are haploid they must be protected from the body’s immune system, this is accomplished by tight junctions btwn sertoli cells

Question 3

Anatomy of spermatozoan and process of spermatogenesis 3

Answer 3

• Basal compartment: lower 1/3rd of the developing spermatozoa and the surrounding sertoli cells, contains only diploid cells (spermatogonia, primary spermatocytes, and sertoli cells)
• Tight junctions btwn sertoli cells (blood-testes barrier) at the top of the basal compartment protect the haploid spermatozoa above the basal compartment (in adluminal compartment)
• Adluminal compartment: contains primary spermatocytes (in both compartments, still diploid) and its subsequent cell types (which will all be haploid)
• Only cells we need to identify are primary spermatocytes (outermost cell w/ granulated nuclei) and sertoli cells (elongated pale nuclei w/ round and dark nucleolus)

Question 4

Endocrine control of spermatogenesis

Answer 4

• Leydig cells producing T are clustered around and in the spaces btwn seminiferous tubules
• Sertoli cells secrete inhibin in response to T from leydig cells and high FSH levels, inhibin acts on pit to decrease FSH release
• Sertoli cells release androgen binding protein (ABP) and release it into ductal lumen to maintain a high T concentration in the lumen of the ducts and epididymis

Question 5

Blood-testes barrier

Answer 5

• Sertoli cells create and maintain the blood testes barrier by tight junctions btwn sertoli cells that separate the basal and adluminal compartments
• The basal compartments contain only diploid cells, whereas the adluminal compartments contain haploid cells that are protected from nl immune surveillance
• Plasma proteins and Abs are excluded from the adluminal compartment

Question 6

Contributions of accessory sex glands to seminal fluids

Answer 6

• Seminal vesicles: contribute 75-80% of seminal fluid, they secrete a watery fluid rich in fractures and PGs
• They are sensitive to androgens in systemic circulation
• Prostate: encircles uretra and contributes about 20% of seminal fluid
• Prostatic fluid rich in proteolytic nzs, citrate, phostphatase, and Zn (has a pH of 6.5)
• 5a reductase nz is present in prostate, leading to prostate increase in size over time due to constant exposure to DHT

Question 7

Histo of seminal vesicles and prostate

Answer 7

• Seminal vesicles have highly unfolded structure lined by simple columnar epithelium and surrounded by SmM
• Prostate: have nests of papillae-like structures (lined by simple columnar epithelia) surrounded by a SmM stroma
• Prostatic concretions increase w/ age