Tag: human physiology

Mature egg secretes a chemical known as fertilizin, which is composed of glycoprotein (monosaccahride and fatty acid substance). Sperm has on its surface a protein substance known as antifertilizin, which is composed of acidic amino acids. The fertilizin and antifertilizin interacts together and this interaction makes the sperms stick to the egg surface. Hence, option B is correct answer.

The average length of the menstrual cycle is about 28 days. By convention the days of the cycle are numbered from the beginning of the menstrual phase of the menstrual cycle, which usually lasts about 4 days. This is followed by the proliferative phase (about 10 days), then by the secretory phase (about 14 days). 

Estrogens are the primary female sex hormones. They promote the development of female accessory/secondary sexual characteristics, such as breasts, and are also involved in the thickening of the endometrium and other aspects of regulating the menstrual cycle.

A cross section of ovary reveals a cortex and a vesicular medulla. The cortex contains round epithelial vesicle or follicles; follicles are actual center of ovum production or oogenesis. Each primary oocyte is surrounded by a layer of granulosa cells and then called the primary follicle. Follicles are usually located directly beneath the cortex of the ovary. They secret estrogen. But once they begin to mature, they migrate towards the inner medulla. The medulla consists of layers of soft stromal tissue. The stromal tissue contains rich supply of blood vessels, nerves and lymph vessels.

In humans, the menstrual cycle starts with the menstrual phase, when menstrual flow occurs and it lasts for 3-5 days. The menstrual flow results due to breakdown of endometrial lining of the uterus and its blood vessels which forms liquid that comes out through vagina. Menstruation only occurs if the released ovum is not fertilised. 

When a woman is born there are usually one million eggs in each ovary and one egg will be released, when she ovulates every month during her menstrual cycle, which is approximately 400-500 eggs over her lifetime. As a woman gets older the rest of the eggs disappear, break down or deteriorate and by the time she reaches menopause, there are no eggs left. Thus, the correct answer is option B.

Progesterone is produced in large amounts in the ovaries by the corpus luteum. It begins producing at the stage of puberty and produced till menopause. It is involved in the menstrual cycle, pregnancy and embryogenesis of humans and other species.