Lecture 11: Male Reproduction Flashcards
How are males and females genetically dimorphic?
The presence of two X chromosomes in females instead of an X and a Y in a male
What disadvantage has the Y chromosome developed through evolution?
The Y chromosome lost much of it’s genetic data since it is far smaller, and the significant change in genetic material means that the X and Y cannot swap genetic material during meiosis. Therefore cannot be repaired.
What is X-Inactivation?
X-Inactivation means that female cells will deactivate one copy of this X chromosome.
The X inactivation is random in each cell and therefore can result in X linked diseases
Why will X-linked conditions affect men more than women?
Because the faulty gene carried on the X has no other X chromosome to correct this mistake and therefore will only display this faulty gene in all cells that use it.
In X-linked recessive conditions the recessive gene has no dominant alternative to override it and therefore the faulty recessive gene is used.
Does sex play a role on medical treatment? If so how?
Yes, it can affect required drug dosage, for example males may require more.
Treatment may affect two sexes differently?
Under-diagnosis due to gender bias, e.g. breast cancer in males.
Certain drugs cannot be given to pregnant females to avoid damaging the foetus. e.g. Thalidomide.
What gene is responsible for determining sex in a foetus?
The SRY Gene.
What is the SRY Gene?
It is a transcription factor that triggers embryonic development as a male.
What are two abnormalities associated with the SRY Gene?
Mutation of the SRY gene or other sex-determining genes downstream of SRY can result in an XY female.
If the SRY gene is copied to the X chromosome, an XX male results.
What week during pregnancy does differentiation occur?
What special cells are formed in male sexual differentiation?
What happens to differentiate males from females?
At 6 weeks differentiation will occur.
A group of special cells called germinal cells will form.
These germinal cells will be attracted towards the two urogenital ridges (which are cells developing near the baby’s developing kidneys)
Testosterone and anti-Mullerian hormone are secreted.
What produces sperm in males?
The testes produce sperm and the ducts transport, store and assist in maturation of the sperm.
What produces the seminal fluid portion of semen?
The seminal vesicles, prostate gland and the bulbourethral glands.
What are the testes and their function?
They produce sperm and steroid hormones.
Divided into lobules by septa of tunica albuginea
What in the testes is responsible for producing sperm?
The sperm is produced by seminiferous tubules, there are roughly 600 per teste.
Describe the structure of the seminiferous tubule.
A basement membrane, lined with smooth muscle to aid movement of sperm through tubule, surrounds a complex of epithelial cells known as sertoli cells, with clusters of spermatogonia around them. The spermatogonia become more differentiated the closer to the centre of the tubule they are until mature spermatozoa in the middle.
Adjacent to these tubules are Leydig cells responsible for production of testosterone and blood capillaries.
What are Sertoli cells?
Epithelial cells which are part of the seminiferous tubules that are connected by tight junctions (small gaps between cells). Assist in progression of germ cells to spermatozoa (sperm cells). Also secretes anti-Mullerian hormone.
What are Leydig cells?
Interstitial cells adjacent to seminiferous tubules that produce testosterone.
