L03: Testicular Function Flashcards
What is the definition of a gamete
A mature haploid reproductive cell
What is the gamete in males
Sperm
What is the gamete in females
Egg
Up to what week can you not tell the difference between a male and female
7 weeks
What process is occurring during the first 7 weeks
Primordial germ cells arise that give rise to sperm and eggs
Which gene on chromosome triggers testis development
SRY gene
How can people be genetically male but female
Due to SRY gene mutation or deletion
How can people be genetically female but male
Due to translocation of SRY gene
After week 7 when there are primordial germ cells what happens to them
They migrate to the gonadal ridges
What process occurs in the gonadal ridge when the PGS migrate to it
1) cells form the colemic epithelium penetrate into the medullary mesenchyme
2) this forms the primitive sex cord (that express SRY)
3) PGS then come in
4) primitive secs cords surround the PGCs to form seminiferous tubules
5) migrating ells from mesonephric primordia which from the vasculature of the testis and form leydig cells around the seminiferous tubules
When the seminiferous tubules form what are the 2 components of it
1) within the seminiferous tubule:
PCGs are called prospermatogonia
Sex cord cells from Sertoli cells
2) between seminiferous tubules:
Vascularisation occurs by leydig cells
When seminiferous tubules form what happens to SRY gene that are expressed by sex cord cells
SRY gene is no longer expressed
When seminiferous tubules have formed what 2 hormones are developed
Androgen
Anti mullerian hormone
What forms the sperm inside the seminiferous tubules
Primitive germinal cells
What structure divides the seminiferous tubules into 2 further sub compartments
Blood testis barrier
When does the blood testis barrier form
During puberty PRIOR to spermatogenesis
What are the 2 functions of the blood testis barrier
1) separate sperm from the immune system to prevent an immune response
2) selective transport ions and small molecules
What are the 3 phases of spermatogenesis
1) proliferation
2) division
3) differentiation
Describe what occurs at the proliferation phase starting with prospermatogonia (from PGCs)
1) at puberty the rested prospermatogonia becomes activated and undergoes mitosis at the basal component of the seminiferous tubule
2) reactive prospermatogonia is referred to as As spermatogonia
3) As spermatogonia constantly renew to form A spermagonium
3) A spermatogonium becomes committed to spermatogenesis
4) A spermatogonium undergo mitosis again to form B spermatogonium
5) B spermatogonium divide again to form primary spermatocytes
What occurs as the division phase of spermatogenesis
1) primary spermatocytes move to the luminal component of the seminiferous tubule by passing the blood testis barrier
2) primary spermatocytes undergone 1st meiotic division
4) this forms the secondary spermatocytes
5) secondary spermatocytes undergone 2nd meiotic division to form the round spermatids
What occurs at the differentiation phase of spermiogeneis
Round spermatids elongate to from elongated spermatids which mature into spermatozoa (sperm)
List the key features of a sperm
Acrosome Flagellum Mitochondria Nucleus Cytoplasm
What does the acrosome contain
Hydrolytic enzymes for acrosome reaction
After the acrosome reaction what structure becomes available
Inner acrosomal membrane receptors to fuse with egg
What is the flagellum
Tail that allows movement of the sperm
What does the mitochondria of the sperm provide
Energy for motility
What does the nucleus of the sperm determine
Sex of the embryo (X or Y chromosome)
What is the sperm DNA packaged into
Protein called protamines
How much cytoplasm does the sperm have
Not much
What is spermiation
What the cells are released into the lumen of the seminiferous tubule
In humans how long does spermatogenesis take
64 days
What does the spermatogenic wave mean
Sperm is constantly produced
Apart from sperm what are the other products of the testis
Androgens: mainly testosterone
Oestrogens: in small amounts
Cytokines: inhibin and AMH
Which cell produces testosterone in the testis
Leydig cells
What happens to the androgen/testosterone that is produced in the leydig cells
- some are released into the lymph
- some are released into the blood
- some remain in the seminiferous tubules
What happens to the testosterone that remains in the seminiferous tubule
1) Testesterone is converted to dihydrotestosterone (DHT) in Sertoli cells (within the seminiferous tubule) as they express the enzyme 5-alpha Reductase for the conversion
2) some of this then binds to androgen receptors in Sertoli cells to drive spermatogenesis
3) some of this binds to androgen binding protein that remain in the testis
Which cell in the testis produced inhibin
Sertoli cells
When inhibin is produced by Sertoli cells what is the role of inhibin
Supress the anterior pituitary gland to decrease FSH production
Which cell in the testis produced AMH
Sertoli cells
What role does AMH have when it is produced
Embryonic role in reproductive system
Describe the HPG axis in puberty
1) hypothalamus secrets GNRH to the anterior pituitary gland
2) anterior pituitary gland produces and releases LH/FHS
3) LH binds to LHCGR on leydig cells
4) leydig cells produce testosterone which move to the seminiferous tubules to become converted to dihydrotestosterone via Sertoli cells
5) some bind to androgen receptor on Sertoli cells for stimulation of spermatogenesis
6) FSH that is released binds to FSHR on Sertoli cells
7) this causes Sertoli cells to increase androgen receptor to increase sensitivity to testosterone production by leydig cells
8) Sertoli cells also stimulate the prouction of inhibin which supress the HPG axis.
When spermatozoa is made in the testis are they mature
No
How does the spermatozoa mature
When they are released in the lumen and undergone maturation in the male tract
When sperm is released in the lumen of the testis where does it enter
Rete testis
After the rete testis where does the sperm go
Epididymis
What occurs at the epididymis for the sperm to mature
Epididymis provided molecules for sperm to acquire fertility and maturity
What are the 3 regions the epididymis is split into
Head
Body
Tail
After the epididymis where does the sperm pass into
Vas deferens
What is the vas deferens for sperm
Storage reservoir
At ejaculation what is released
Sperm
Seminal plasma
Where does the seminal plasma come from
Accessory sex glands
What is the seminal plasma involve
Fructose
Buffer
Anti-oxidants
What are the 2 main accessory glands
Seminal vesicle
Prostate
Where does the seminal vesicles empty into during ejaculation
Ejaculatory duct
What does the seminal vesicles secret to stop ejaculate clotting
Fibrinogen like substrate
What does the prostate secrete
Fluid that is alkaline high in zinc
What does the alkaline high in zinc protect the sperm from
Acidic environment
What else does the prostate secrete
Ejaculate clotting enzymes
And
Enzymes that cause liquefaction (so the sperm doesn’t stay in the vagina forever)
At what phase does the prostate secrete
Capulation
What does the bulbo-urethral gland produce
The pre-ejaculate
Why is a pre-ejaculate secrete into the urethra
For lubrication and neutralisation for acidic urine in the urethra before ejaculation
Where does capacitation of the sperm occur
In the vagina
What are the 2 components of capacitation
1) Change in sperm motility- hypermotility of the sperm to allow it into the cervix
2) acrosome reaction when the sperm gets to the egg
