Sertolli and Leydig cells, functional anatomy and spermatogenesis
What happens when a spermatogonia is stimulated to divide?
- Stay on BM as spermatogonia - Go into the spermatogenic pathway - Spermatogonia is phagocytosed into the Sertoli cell cytoplasm - Brought back out of the Sertoli cell - Class 1 spermatocyte --> class II --> spermatid --> mature spermatogia
What % of sperm should be viable for reproduction?
10-14%
What is the axonemal motor?
9+2 for sperm tail movement
What allows the sperm to digest the granulosa cells?
Acrosin, allows it to clear the granulosa cells and allow digestion through zona pellucida
What contributes to abnormal sperm production?
Age, drugs, alcohol, diet, lack of exercise They should divide in the Sertoli cell but sometimes they do not separate Red circle is normal
What do Sertoli cells make?
Androgen binding protein which grabs testosterone
Where do spermatogonia rest?
Basement membrane along with Sertoli cells
How many germ cells attach to Sertoli cells?
Between 40-200+
What is the significance of Sertoli cells being an epithelial layer?
Everything inside the seminiferous tubules has to enter via diffusion (no blood supply)
What stimulates Sertoli cells?
F*S*H
Hormones for spermatogenesis?
FSH and testosterone
What is required for spermatogenesis?
FSH and testosterone (not dihydrotestosterone)
What is the major stimuli for early spermatogenesis?
FSH on the germ cell and Sertoli cell
What does inhibin do?.
Feeds back on FSH
What does the sperm use for metabolism and where is it made?
Fructose, made by the seminal vesicles
What is the general outline of the production of hormones from GnRH --> Inhibin?
GnRH --> LH and FSH LH --> testosterone and dihydrotestosterone (from Leydig) FSH --> Sertoli nursing the germ cells Sertoli make inhibin when they have enough sperm Inhibin decreases FSH to lower spermatogenesis
What is inside the acrosome?
Golgi-derived lysosome that stains lighter Contains the enzyme acrosin
What is the purpose of Sertoli cells producing ABP (androgen binding protein)?
It concentrates testosterone from the Leydig cells in the ECS
What is unique with the Sertoli cell nucleus?
It has a weird shape, has infolding of the nuclear envelope with two smaller satellite bodies that are the same size as the primary nucleolus Red circles are the tight junctions
What is the significance of the testicular appendix?
It is the remnant of the Mullerian duct (mesonephric)
What provides the ATPase activity for the energy release for the axonemal motor?
Kinesin containing arms
What simulates the Leydig cells?
LH
What is the difference between LH and FSH?
LH stimulates Leydig FSH stimulates Sertoli
What happens when there is a low number of sperm on a Sertoli cell (less than ~50)
Less inhibin is made allowing for the production of more FSH --> increased spermatogenesis
What do the Leydig cells do?
Make the major male steroids, testosterone and dihydrotestosterone
What are the black dots in the body of the sperm?
Mitochondria
Is the tunica albuginea more or less thick than the dura mater?
More thick
Are the Leydig cells covered with lymphatics?
No
Are the seminiferous tubules vascularized?
No they are avascular and epithelial, they rest on a basement membrane
Where are Sertoli cells situated?
On the basement membrane
What is unique about the position of the Sertoli cells?
Only non-germinal cell inside the basement membrane of the seminiferous tubules
Where are the germ cells?
Seminiferous tubules
What is another name for Sertoli cells that outlines their importance for the production of sperm?
Sustanacular cells (nurse cells) that are important in the production of sperm
What are the tight junctions between Sertoli cells also known as?
Testes blood barrier
What does the male accessory reproductive structures *NOT* include?
Testis
What is required for meiosis I and II?
Testosterone
What is required for the final maturation of sperm cells?
Testosterone
What is the difference between testosterone and dihydrotestosterone?
Testosterone stimulates Sertoli cells Dihydrotestosterone stimulates secondary sexual characteristics
What makes inhibin in the male?
The Sertoli cells
Where are Leydig cells?
The periphery in the ECS
What is the benefit of the tubules being avascular and lacking lymphatics?
The steroids made are not taken out rapidly, also it prevents the proteins from the sperm getting out into the circulation
What is the primary male sex gland?
The testis
What is the acrosome?
The tip of the head of the sperm
What do neighboring Sertoli cells do?
They act together to bring batches of sperm along in synchronous waves
Where are the limited lymphatic vessels concentrated in the tubules?
They are concentrated in the interstitial space
Where are the Leydig cells situated?
They are in the ECS along with the circulation for the seminiferous tubules
Where are the Sertoli cells?
They are the in the seminiferous tubules
What are the septa?
They divide the lobules containing the seminiferous tubules
What do the Sertoli cells do?
They have tight junctions with germ cells until they are released into the lumen
What happened to the chernobyl workers?
They lacked organization in the seminiferous tubules with few germ cells, had RBCs in the interstitial space and lacked Leydig cells there
What happens when spermatogonium are stimulated by FSH?
They reproduce into 2 Either both can go on and make sperm Or one or both of the new ones can stay behind
What is the adluminal part formed by?
Tight junctions welding lines between the Sertoli Cells that seal off the innermost portion of the Seminiferous tubules (adluminal compartment) from the peripheral Seminiferous tubules (basal compartments)
What is the thick outer covering of the testis?
Tunica albuginea
How many tight junctions do the Sertoli cells have?
Up to 50
When is inhibin made?
When the Sertoli cells are saying "I already have as many sperm as I can handle"
Is there genetic material in the acrosome?
Yes, although it appears flat and stains light
Do men have lymphocytes against their own sperm?
Yes, during the development of the immune system they do not select against spermatic proteins as they do not make sperm yet
What does acrosin do?
allows the sperm to penetrate the protective layers around the ovum from the ovary
Where are spermatogonium cells situated?
basement membrane Yellow circle
What are the male secondary sex glands?
prostate, seminal vesicle, bulbourethral
What is the final step of spermatogenesis?
spermiogenesis
