Flashcards in Male Reproductive System Deck (73)
What type of gland is the exocrine component of the testes? What is the mechanism of sperm secretion?
Compound tubular gland which secretes sperm via holocrine secretion (production of residual bodies)
What is the name of the dense irregular connective tissue capsule around the testes?
What is the innermost layer of the testes capsule called and what does it contain?
Tunica vasculosa - contains loose connective tissue with blood vessels called tunica vasculosa
What happens to the tunica albuginea posteriorly?
Thickens to form mediastinum testis. The septae will divide each testis into lobules.
What is the organization of a lobule of the testes?
Each lobule contains 1-4 seminiferous tubules, beginning and ending near the mediastinum testes
What is contained in the interstitial connective tissue / stroma?
Lymphatic vessels, blood vessels, and nerves
How can Leydig cells be identified? Why is their cytoplasm acidophilic?
Leydig cells can be identified as the largest cells of the interstitium, with eosinophilic cytoplasm, vesicular nucleus, prominent nucleolus, and a cytoplasm of lipid droplets.
They are acidophilic due to their mitochondria with tubulo-vesicular cristae + smooth ER
What is the function of Leydig cells and what is the function of their product?
They produce testosterone via stimulation by LH. Testosterone is important for development, secondary male sex characteristics, reproductive tract function, and maturation / maintenance of gamete production.
What is the tunica propria and what cell type does it contain? What is the function of this cell type?
Layer of dense connective tissue surrounding the seminiferous tubule. Contains contractile myoid cells which have characteristics of smooth muscle cells and fibroblasts. Contracts to propel secreted spermatozoa along seminiferous tubule.
What separates the tunica propria from the seminiferous epithelium?
A basal lamina
What is a primary cause of male infertility?
Sperm production must happen at 34-35 degrees C, which is 2-3 degrees below body temperature. Undescended testicles may lead to elevated temperature of testes and infertility. Also, mutagens, steroids, infections, and radiation can cause this.
What are Sertoli cells and what is their function?
They are part of the seminiferous epithelium. They function to form compartments to organize the spermatogenic cells, and have microenvironments needed for the development of the different types of cells.
How can Sertoli cells be identified?
They are columnar and stretch from basal lamina to lumen of tubule. 3 main characteristics
1. Indistinct plasma membrane boundaries
2. Vesiculated nucleus - pale staining center
3. Prominent nucleolus
What type of junctions create the blood-testis barrier and why is this important?
Sertoli-Sertoli cell junctions. This is important because developing sperm may be recognized as foreign by immune cells and must be kept separate from the blood (much like the thymus)
What are the two compartments of the seminiferous epithelium and what is contained in them? What divides these two compartments?
The two compartments are divided by the projections of interconnecting Sertoli-Sertoli junctions.
Basal: Spermatogonium, and briefly primary spermatocytes
Adluminal: Spermatocytes and spermatids
What is the function of the Sertoli-spermatid junctions?
Sertoli cells bind spermatids within the seminiferous epithelium to help anchor the spermatid to the Sertoli cell during sperm development
How do Sertoli cells function to keep high levels of testosterone for spermatogenesis?
They produce testosterone binding protein under the control of FSH to keep testosterone levels about 200x higher than normal blood levels
What do Sertoli cells secrete other than testosterone binding protein and what is its function?
Fluid which functions to help move spermatozoa along the lumen of the seminiferous tubule
What are two mechanisms of autoimmunity to sperm?
1. If Sertoli-Sertoli junctions are compromised, immune system may detect foreign particles of spermatozoa since they have different genetic makeup from host.
2. Vasectomy allows sperm to leak out of reproductive tract and can have autoimmunity to their sperm
What are the three phases of spermatogenesis and how long does it take?
65-75 days in humans.
1. Spermatogonial phase - mitosis & spermatocyte production via spermatogonia
2. Spermatocyte phase - meiosis 1 and 2 to make haploid
3. Spermatid phase - differentiate of sperm to give mature structure
What are the three types of spermatogonia and where do they reside? How can they be identified?
Ad(ark) -> Ap(ale) -> B, do not have to distinguish between them.
They are next to the basal lamina in the basal compartment. They are identified as any cell resting on basal lamina but lacking Sertoli cell morphology.
What are Ad cells and what are their possible fate?
A-dark spermatogonia. They are the stem cells. They divide by mitosis to become either two Ad or two Ap
What are type Ap spermatogonia and what is a cohort?
Spermatogonia formed by Ad which are now committed to becoming sperm. They will do several rounds of mitosis, but all remained linked by cell bridges and are called a cohort. These cells develop together.
They will differentiate to become B type spermatogonia.
What do type B spermatogonia become and how do they move to the adluminal compartment?
They divide by mitosis to produce preleptotene primary spermatocytes. They move into the adluminal compartment when Sertoli-Sertoli junctions break, and new ones form beneath them, pushing them up.
What cells have the largest nuclei in the seminiferous epithelium and why?
Primary spermatocytes. This is because they have strands of condense and very basophilic chromatin, and have twice the total amount of DNA compared to interphase cells since they are about to undergo the reductional division of meiosis 1, and each chromosome has a sister chromatid
When does crossing over occur and how long does this take?
Four chromatids form tetrads (two homologous chromosomes with sister chromatids). This takes 2 weeks during the extended prophase of meiosis 1.
Why will meiosis I produce secondary spermatocytes with the same amount of DNA as the parent cell?
There are now only 23 chromosomes; however, they now have 2 sister chromatids, which is the same amount of DNA as the 46 chromosomes of the parental primary spermatocyte prior to the DNA replication before prophase I.
Why is it unlikely to see any secondary spermatocytes in a histological section?
The equatorial division, Meiosis II, happens in only a few hours, whereas Meiosis I takes weeks.
What does each diploid type B spermatogonium yield?
A preleptotene spermatocyte which will form four haploid, genetically distinct spermatids which have 1/2 the DNA of this parental cell