4.1 Sexual Reproduction in Humans Flashcards
Give a brief overview of what the male reproductive system consists of:
- A pair of testes contained in an external sac, the scrotum
- The penis
- Ducts connecting the testes with the penis
- Accessory glands, i.e. the prostate gland etc. These glands secrete fluids that mix with the sperm to make semen.
Where does sperm formation occur?
Seminiferous tubules are where sperm formation occurs. Seminiferous tubules are about a thousand coiled tubes found within the testis.
During sperm formation where do the cells FIRST go?
The cells move towards the space running through the middle of the tubule and collect in the vasa efferentia. These are coiled tubes that carry sperm to the head of the epididymis. The sperm remain in the epididymis for a short time while they become motile, and then they pass into the vas deferens during ejaculation.
Where does the vas deferens carry the sperm to and what happens during this journey?
The vas deferens carries the sperm towards the penis from the epididymis. On the way the seminal vesicles secrete mucus into the vas deferens. The mucus contains a mixture of chemicals including fructose, respired by the sperm for energy.
After receiving the chemicals such as fructose from the seminal vesicles mucus, where does the sperm go?
The sperm and now seminal liquid (mucus from seminal vesicle) move through the ejaculatory duct, which passes through the prostate gland, where zinc-containing prostate fluid is secreted (ALKALINE)
Why is it that it’s important the zinc containing prostate fluid thats secreted into the sperm is alkaline?
It needs to be alkaline to neutralise the acidity of any urine remaining in the urethra and neutralises the acidity of the vaginal tract.
What does the zinc-containing prostate fluid do for the sperm?
-It maintains sperm mobility
- it provides nutrients for the sperm, including fructose, their main energy source, amino acids and zinc ions.
- neutralises any acidity in the urethra or vaginal duct as it’s alkaline.
In the female reproductive system how many ovaries are there?
Two
Where do oocytes come from?
Oocytes mature in follicles, which develop from cells in the germinal epithelium, around the periphery of the ovary. Mature follicles migrate to the surface of the ovary, from where a secondary oocyte is released at ovulation. The ovaries alternate each month in realising the oocyte.
Where does the secondary oocyte go after formation?
Cilia at the entrance of the oviducal funnel sweep the secondary oviduct from the peripheral of the ovaries into the oviduct/fallopian tube. These ciliated epithelial cells lining the oviduct convey the secondary oocyte to the uterus.
What are the the three layers of the uterus and give a brief description of them:
- The perimetrium is a thin layer around the outside.
- The myometrium is the muscle layer.
- The endometrium is the innermost layer. It is a mucous membrane, which is well supplied with blood. It is the layer that builds and is shed in a monthly cycle, unless an oocyte is fertilised, in which case, the embryo implants in the endometrium.
What is gametogenesis?
The production of gametes in the sex organs is gametogenesis.
What is spermatogenesis?
The formation of sperm in the testis.
What is oogenesis?
The formation of the secondary oocytes in the ovary.
Both the testis and the ovary undergo mitotic and meiotic divisions to form haploid gametes, why is it important that the gametes are diploid at fertilisation?
So the diploid number is restored and the chromosome number does not double in every generation.
What happens in spermatogenesis? (Big answer)
Cells of the germinal epithelium cells are diploid. They divide by mitosis to make diploid spermatogonia and more germinal epithelium cells. These spermatogonia divide many times by mitosis and enlarge, making diploid primary spermatogonia and more spermatogonia. These primary spermatogonia undergo meiosis 1, making secondary spermatocytes, which are haploid. Secondary spermatocytes undergo meiosis 2, making haploid spermatids. These spermatids mature into spermatozoa or sperm.
