Spermatogenesis Flashcards
What is the role of the testes?
- Produce Sperm
- Store sperm
- Produce hormones which regulate spermatogenesis
Approximately How much Sperm is produced each second?
- Approximately 1500 produced per second
- Around 5.5 million in an hour
- Estimated to be around 130 million sperm per day
Where are the testes located?
- Lie in the scrotum outside the body cavity
What is the optimum temperature for sperm production?
1.5°c to 2.5°c below body temperature
What happens if the temperature exceeds the optimum?
Overheating of testes reduces sperm count
What is the normal volume of the testes?
- Normal volume of testes approximately 15-25ml
- Measured by orchidometer
- Well vascularised and well innervated
How are the testi’s arranged?
- Testi’s are 90% seminiferous tubules
- Which is the site of spermatogenesis
How long are these tubules?
How are these tubules structured?
- 600 meters long in each testi
- Tubules are tightly coiled
Where do these tubules lead to?
All lead to the epididymis and ultimately vas deferens
What is the vas deferens?
The vas deferens, also known as the ductus, is a tube through which spermatozoa travel through
Where are primary germ cells or spermatogonia found?
On the basement membrane
What are the walls of the tubules made up off in the cross section of the seminiferous tubule?
Walls of tubules made up of tall columnar endothelial cells called Sertoli cells
Where are Adluminal compartments formed?
Tight junctions between these Sertoli cells form Adluminal compartments
What is the advantage of the formation of Adluminal compartments?
Allows specific enclosed environment for spermatogenesis which is filled with secretions from Sertoli cells
What are the spaces between the seminiferous tubules filled with?
Filled with
- Blood
- Lymphatic vessels
- Leydig cells
- Interstitial fluid
Describe the steps that occur in meiosis (PART 1)
- During interphase, (S-phase) each chromosome is duplicated
- The replicated chromosomes stay attached to the originals forming two pairs of sister chromatids (tetrads) for each chromosome
- Tetrads align at the metaphase plate and crossing over occurs. The sister chromatids move to the opposite poles of the cell
Describe the steps that occur in meiosis (PART 2)
- After the meiosis I division, There is one sister chromatid pair in each cell. They are no longer identical due to crossing over
- MII (Meiosis 2) is another cycle of cell division in which the sister chromatids separate to give a single unique chromosome in each daughter cell
What are the different sperm stages during spermatogenesis?
Spermatogonia -> Primary spermatocytes -> Secondary spermatocytes -> Spermatids -> Spermatozoa
Describe the Spermatogonia stage
Germ cell is on the basement membrane
- Capable of mitotic or meiotic division to produce primary spermatocytes or more spermatogonia
- They are diploid
Describe the Primary Spermatocytes stage
- They move into the Adluminal compartment
- Duplicate their DNA to produce sister chromatids which exchange genetic material before entering meiosis 1
- They are 46 XY diploid
Describe the Secondary Spermatocytes stage
- Secondary Spermatocytes have undergone meiosis 1 to give 23X + 23Y haploid number of chromosomes
- Arranged as sister chromatids
Describe the Spermatids stage
- Meiosis 2 occurs to give 4 haploid spermatids
- Round Spermatid to elongated spermatid differentiation
Describe the Spermatozoa stage
Mature sperm extruded into the lumen
How long does the process of Spermatogenesis last?
New cycle every 16 days
Entire process takes approximately 74 days
