Tag: zoology

Progesterone is a natural female hormone. It is called as the pregnancy hormone, it is essential before and during pregnancy. After ovulation occurs, the ovaries start to produce progesterone needed by the uterus. Progesterone causes the uterine lining or endometrium to thicken. This helps prepare a supportive environment in the uterus for a fertilized egg. After 8 to 10 weeks of pregnancy, the placenta takes over progesterone production from the ovaries and substantially increases progesterone production.

The secretion of pituitary gonadotrophic hormones is stimulated by gonadotropin hormone-releasing hormone (GnRH) from the hypothalamus and modulated by testicular hormones. At the onset of puberty, the pituitary gland secretes GnRH, or gonadotropin-releasing hormone. In response, the hypothalamus release follicle stimulating hormone (FSH) and luteinizing hormone (LH) into the male system. LH enters the testes, stimulating the Leydig cells to release testosterone. Testosterone hormone is responsible for the secondary sexual characteristics like deepening of the voice, the growth of facial, axillary, and pubic hair, and the beginnings of the sex drive.

Insulin and glucagon work synergistically to keep blood glucose concentrations normal. An elevated blood glucose concentration results in the secretion of insulin which leads to glucose transportation into body cells. Glucagon is secreted by the alpha cells of the pancreas when blood glucose is low. Glucagon's function is to cause the liver to release stored glucose from its cells into the blood. Corticoids are also responsible for the regulation of glucose metabolism. 

Alpha cells are endocrine cells in the islets of Langerhans of the pancreas. Thy are responsible for synthesizing and secreting the peptide hormone glucagon, which elevates the glucose levels in the blood.

Most birth control pills are combination pills containing a combination of the hormones oestrogen and progesterone to prevent ovulation. A woman cannot get pregnant if she doesn't ovulate because there is no egg to be fertilized. The pill also works by thickening the mucus around the cervix, which makes it difficult for sperm to enter the uterus and reach any eggs that may have been released. The hormones in the pill can also sometimes affect the lining of the uterus, making it difficult for an egg to attach to the wall of the uterus.

The third ventricle (ventriculus tertius) is one of four connected fluid-filled cavities comprising the ventricular system within the rabbit's brain. The third ventricle is a narrow vertical cleft between the 2 lateral ventricles.

The main hormone secreted by the testes is testosterone, an androgenic hormone. The placenta is an endocrine gland, that is only present during pregnancy. It secretes human chorionic gonadotrophin hormone (hCG), which is present only during pregnancy.

The thymus gland is an integral part of immune system. It helps in the maturation of lymphocytes. The thymus serves a vital role in the training and development of T-lymphocytes or T-cells, an extremely important type of white blood cell. So, the correct answer is option B.

The hypothalamus is a mass of grey matter present at the base of the cerebrum. The centre for thirst and drinking regulation is present in lateral hypothalamus while that for hunger and satiety is present in the arcuate nucleus, ventral nucleus and lateral hypothalamic area. The anterior hypothalamic region regulates body temperature.

The hypothalamus is the control centre for many autonomic functions of the peripheral nervous system. Connections with structures of the endocrine and nervous systems enable the hypothalamus to play a vital role in maintaining homeostasis. The hormones produced by this area of the brain govern body temperature, thirst, hunger, sleep, circadian rhythm, moods, sex drive, and the release of other hormones in the body. Hence, if hypothalamus is damaged in an accident, control of water balance, hunger and body temperature will be lost.