Reproduction system: Sperm Flashcards
What is spermatogenesis?
The process of make sperm
Where does spermatogenesis occur?
In the seminiferous tubules of the testes
Label the diagram
When does sperm production begin?
After puberty
What is the rate of sperm production?
300-600 sperm per gram of testicle tissue per second
What are the three phases of spermatogenesis?
Mitotic division, meiotic division, cytodifferentiation
During puberty, what happens to the stem cells in the seminiferous tubules?
They become re-activated and begin to divide by mitosis
Explain what happens in spermatogenesis?
The spermatogonia (a sperm producing cell in the wall of the seminiferous tubules) divide by mitosis, one of these cells remains undifferentiated and on the wall to maintain the stem cell population and the other cell continues to divide by mitosis forming spermatogonia. The spermatogonia will undergo mitosis 6-7 times
Where does the mitotic division occur during spermatogenesis?
Basal compartment of the seminiferous tubules
How are the spermatogonia joined together?
In a chain
Where do the spermatogonia go to once they have completed their mitosis?
Move between adjacent sertoli cells to the adluminal comparmant of the seminiferous tubules
Label the diagram
What happens to the primary spermatocytes?
They undergo meiosis I producing… (FYI the chromosomes in the parent cell are duplicated to produce homologous chromosomes, these are re-shuffled due to independent assortment and recombination then separated evenly into…) 2 secondary spermatocytes with 23 chromosomes each with 2 chromatids
What happens tote secondary spermatocyte?
They undergo meiosis II and each secondary spermatocyte produces 2 spermatids each with 23 chromatids in each one
What is spermiogenesis?
The final stage of spermatogenesis where the spermatids differentiate and become spermatozoa (i.e. sperm) for a mail, a mid piece and a head
What is the mid-piece of the sperm packed with?
Mitochondria
What is the head packed with? What is on top of the head?
Contains the DNA
The acrosome
What is the acrosome?
A compartment filled with enzymes to penetrate the shell of the egg
What is the shape of the sperm? How does it get into this shape?
It is a pointy shape
It removes it’s residual body which contains all of its cytoplasm (which is unnecessary because it only has to swim to the fallopian tubes, no need to duplicate etc.)
What are the hormones that control spermatogenesis? what controls these?
FSH and LH control spermatogenesis, GnRH controls both of these
Where are FSH and LH produced?
In the anterior pituitary (FYI GnRH controls FSH and LH via the hypophyseal portal vein)
What does LH control?
The Leydig cells
What does LH cause the Leydig cells to do?
Causes it to produce androgens (testosterone and dihydrotestosterone (DHT))
What does DHT (dihydrotestosterone) cause?
Secondary sexual characteristic (i.e. hair, lowering of voice etc.)
What does FSH control?
The sertoli cells
What does the FSH cause the sertoli cells to do?
Produce androgen binding proteins
Why are androgen binding proteins produced?
Androgens are lipid based and to be transported in the blood they need binding proteins
What is the function of androgen binding protein (ABP)?
Helps transport androgen around the body and creates a store of androgen inside the testes (if ABP is bonded to androgen it cannot leave creating a store)
How does testosterone affect the sertoli cells?
Drives spermatogenesis
How is the amount of testosterone controlled?
There is a negative feedback loop where the more testosterone produced, the less GnRH (acting on the hypothalamus) and less FSH and LH (acting on the anterior pituitary) is produced
How can FSH be controlled separately from FH production?
The sertoli cells produce inhibin which can limit the production of FSH
What is the criteria of men being infertile?
Having less than 20 million sperm per ml
What is reduced fertility in men called? What is the condition called when men can’t produce any sperm?
Oligospermia = reduced fertility
Azoospermi = no fertility
