Endocrine system (4,5,6)

• Pancreas -is a long soft organ that lies transversely along the posterior abdominal wall, posterior to the stomach, and extends from the region of the duodenum to the spleen
• Pancreas -is a gland in the exocrine portion that secretes digestive enzymes that are carried through a duct to the duodenum
• Pancreas -has an endocrine portion consists of pancreatic islets, which secrete glucagon and insulin
• Alpha cells in the pancreatic islets secrete the hormone glucagon in response to a low concentration of glucose in the blood
• Beta cells in the pancreatic islets secrete the hormone in response to a high concentration of glucose in the blood
• Gonads are the primary reproductive organs. Testes in male and ovaries in the female
• Testes is responsible for producing sperm. Ovaries are responsible for producing the ova. The ovaries and testes also secrete hormones and are considered endocrine glands
• Male sex hormones, as a group, are called androgens.
• The principal androgen is called testosterone, which is secreted by the testes. A small amount is also produced by the adrenal cortex
• Production of testosterone begins during fetal development, continues for a short time after the birth, nearly ceases during childhood, and then resumes at puberty
• The steroid hormone (under testes notes) is responsible for: The growth and development of the male reproductive structures, increased skeletal and muscular growth, enlargement of the larynx accompanied by voice changes, growth and distribution of body hair, increased male sexual drive
• Testosterone secretion is regulated by a negative feedback system that involves releasing hormones from the hypothalamus and gonadotropins from the anterior pituitary
• Two groups of female sex hormones are produced in the ovaries, the estrogens and progesterone
• These steroid hormones (estrogen and progesterone) contribute to the development and function of the female reproductive organs and characteristics
• At the onset of puberty, estrogen promotes: the development of the breast, distribution of fat evidenced in the hips, legs, and breast, maturation of reproductive organs such as the uterus and vagina
• Progesterone causes the uterine lining to thicken in preparation for pregnancy
• together, progesterone and estrogens are responsible for the changes that occur in the uterus during the female menstrual cycle
• In addition to the major endocrine glands, other organs have some hormonal activity as part of their function. These include the thymus, stomach, small intestines, heart, and placenta
• Thymosin, produced by the thymus gland, plays an important role in the development of the body's immune system
• The lining of the stomach, the gastric mucosa, produces a hormone called gastrin in response to the presence of food in the stomach. This hormone stimulates the production of the hydrochloric acid and the enzyme pepsin, which are used in the digestion of food
• The mucosa of the small intestine secretes the hormones secretin and cholecystokinin. Secreting stimulates the pancreas to produce a bicarbonate-rich fluid that neutralizes the stomach acid.
• Cholecystokinin stimulates contraction of the gallbladder, which releases bile. It also stimulates the pancreas to secrete digestive enzymes
• The heart also acts as an endocrine organ, in addition to its major role of pumping blood. Special cells in the wall of the upper chambers of the heart, called atria, produce a hormone called atrial natriuretic hormone or atriopeptin
• the placenta develops in the pregnant female as a source of nourishment and gas exchange for the developing fetus. It also serves as a temporary endocrine gland
• One of the hormones secreted by the placenta is human chorionic gonadotropin, which signals the mother's ovaries to secrete hormones to maintain the uterine lining so that it does not degenerate and slough off in menstruation