Spermatogenesis Flashcards
What do the testes produce and store?
Testes produce sperm and store it
What do the hormones produced by testes do?
These hormones regulate spermatogenesis
Where do the testes lie?
Lie in the scrotum outside the body cavity
What is the optimum temperature for sperm production?
Optimum temperature for sperm production is 1.5-2.5 degrees below body temperature
What is the testes welly done?
Well vascularised and well inervated
What is the normal volume of testes
Normal volume of testes approximately 15-25 ml measured by an orchidometer
In the testicular structure, where do the tubules lead to?
Tubules lead to an area on one side called the rete
In the testicular structure, where does the rete lead to?
Rete leads to the epididymis and vas deferens
In the testicular structure, what is the testis 90% made up of?
Testis is 90% seminiferous tubules
What is the seminiferous tubules the site of?
Site of spermatogenesis
Where are spermatogonia or primary germ cells located?
Spermatogonia or primary germ cells are on the basement membrane
What are the walls of the tubules made up of and what do tight junctions between them form?
Walls of the tubules are made up tall columnar endothelial cells called sertoli cells. Tight junctions between these form adluminal compartments
What do adluminal compartments allow?
Allow a specific enclosed environment for spermatogenesis which is filled with secretions from srtoli cells
What are the spaces between tubules filled with?
Spaces between the tubules are filled with blood and lymphatic vessels, leydig cells and interstitial fluid
After how many days is there a new cycle in spermatogenesis
New cycle every 16 days
Steps involved in spermatogenesis
- Mitotic proliferation of spermatogonia
- Meiosis and development of spermatogonia
- Spermatogenesis, elongation, loss of cytoplasm, movement of cellular contents
What is incomplete in spermatogenesis?
Each cell division from a spermatogonium to a spermatid is incomplete
What do the cells in spermatogenesis remain connected with and what does this allow?
The cells remain connected to one another by cytoplasmic bridges forming a syncytium allowing synchronous development
What do syncytia at various stages of development throughout seminiferous tubules give?
Syncytia at various stages of development throughout seminiferous tubule give continuous supply
Oogonia vs spermatogenesis
- Both oogonia and spermatogonia laid down in foetus
- Both oogonia and spermatogonia begin meiosis to make oocyte and spermatocyte respectively
- You cannot make more oocytes by mitosis whereas you can make more spermatogonia mitotically
- There’s a limited supply of oogonia whereas there’s a lifetime supply of spermatogonia
How are steroids produced in testis?
- Leydig cells contain LH receptors and primarily convert cholesterol into androgens. Intra-testicular testosterone levels are 100x those in plasma
- Sertoli cells contain FSH receptors and convert androgens to oestrogen
What stimulate sertoli cells and what do they control?
Androgens cross over to testis and stimulate sertoli cell function and thereby control spermatogenesis
What does FSH establish compared to androgen?
FSH establishes a quantitatively normal sertoli cell population, whereas androgen initiates and maintain sperm production
What do anabolic steroids reduce and what does this eventually lead to?
Anabolic steroids reduce FSH/LH from pituitary due to negative feedback, leading to testicular atrophy
How do you get an erection?
By the vasodilation of the corpus cavernosum and partial constriction of the venous return
What is an erection under the control of?
Under parasympathetic control
ANS in ejaculaiton?
By the ANS causing coordinated smooth muscle contractions of the vas deferens, glands and urethra
Sympathetic nervous system in ejaculation?
Sympathetic nervous system controls movement of sperm into epididymis, vas deferens and penile urethra
Somatic nervous system in ejaculation?
Somatic nervous system control expulsion of the glandular secretions and evacuations of urethra
(Seminal fluid)
What is produced by the bulbourethral gland and what is it known as?
Produces a clear viscous secretion high in salt, known as pre-ejaculate
What does the fluid produced by the bulbourethral gland helps?
This fluid helps to lubricate the urethra for some spermatozoa to pass through, neutralising traces of acidic urine
(Seminal fluid)
What does the secretions from the seminal vesicles contain and what percentage does the secretion compromise of the ejaculate?
- Contains proteins, enzymes, fructose, mucus, vitamin C and prostaglandins
- Secretions compromise 50-70% of the ejaculate
Why does the secretions from the seminal fluid have a great amount of fructose?
High fructose in order to provide an energy source
Why does the secretion from the seminal fluid have a high pH?
High pH protects against acidic environment in vagina
(Seminal fluid)
What does the prostate secrete and how much does it compose of the seminal fluid?
Secretes milky or white fluid roughly 30% of the seminal fluid
What does the secretion from the prostate contain?
Protein content less than 1% and includes proteolytic enzymes, prostatic acid, phosphatase and prostate-specific antigens which are involved in liquefaction
High zinc concentration
