1. Endocrine glands are glands of internal secretion. These glands are also called ductless glands. Hormones are the secretions produced by endocrine glands. Target organs are the specific organs or tissues to which hormones are carried by the bloodstream. This is a feedback mechanism because the activity of the target organ affects the activity of the endocrine organ. (para 10-1)
2. The fundamental control "system" is the interaction of heredity and environment. Genes determine the range of potentiality. Environment develops it. Controlling the tissues and organs in general are the hormones of the endocrine system. Providing more precise and immediate control of the body structures is the nervous system. (para 10-2a)
3. Endocrine organs are richly supplied with blood vessels because hormones must be carried to their target organs by the bloodstream. (para 10-2b)
4. a. Pituitary body.
b. Thyroid gland.
c. Parathyroid glands.
d. Pancreatic islets.
e. Suprarenal (adrenal) glands.
f. Gonads (female--ovaries, male--testes). (para 10-2c)
5. The pituitary body is a small pea-sized and pea-shaped structure. It is attached to the base of the brain in the region of the hypothalamus. In addition, it is housed within a hollow of the bony floor of the cranial cavity. The pituitary body is actually two glands: the posterior pituitary gland and the anterior pituitary gland.
6. The posterior pituitary gland is that portion of the pituitary body which comes from and retains its connection with the base of the brain. The hormones of the posterior pituitary gland are actually produced in the hypothalamus of the brain. The two recognized hormones of the posterior pituitary gland are ADH (antidiuretic hormone) and oxytocin. The first is involved with the resorption or salvaging of water within the kidneys; it is produced under thirst conditions. The second is concerned with contraction of smooth muscle in the uterus and with milk production. (para 10-4)
7. The anterior pituitary gland originates from the roof of the embryo's mouth. It then attaches itself to the posterior pituitary gland. By means of a venous portal system, the anterior pituitary gland is connected to the hypothalamus. Here, certain chemicals known as releasing factors are produced. These are carried to the anterior pituitary by the venous portal system. They stimulate the anterior pituitary gland's cells to secrete their specific hormones. In turn, these hormones stimulate the target organs to produce their own products. This stimulating effect is referred to as trophic. Two of the hormones produced by the anterior pituitary gland are somatotrophic hormone and ACTH (adrenocorticotrophic hormone). The target organs of the first are the growing structures of the body. The second stimulates the cortex of the suprarenal (adrenal) gland to produce its own hormones. (para 10-5)
8. The thyroid gland is in the neck region just below the larynx and surrounds the trachea. The masses on either side of the trachea are the right and left thyroid lobes. The tissue connecting the two lobes is called the isthmus. It is found across the front of the trachea. Each lobe of the thyroid gland is supplied by the superior and inferior thyroid arteries. The primary hormone of the thyroid gland is thyroxin, which affects the basal metabolic rate (BMR), the level of activity of the body. (paras 10-6--10-8)
9. The parathyroid glands are located on the posterior aspects of the thyroid lobes. The hormone produced by these glands is called parathyroid hormone or parathormone. It is involved with calcium metabolism. (paras 10-9, 10-10)
10. Within the pancreas are distributed small groups of cells known as islets. The two most commonly recognized hormones of the islets are insulin and glucagon. Theses hormones are involved with glucose metabolism. (paras 10-11, 10-12)
11. The suprarenal glands are embedded in the fat above the kidney on each side. Each suprarenal gland has an internal medulla and an external cortex. The inner portion produces a pair of hormones: epinephrine (adrenalin) and norepinephrine (noradrenalin). These are involved in the mobilization of energy during the stress reaction ("fight or flight"). Each suprarenal cortex produces hormones which can be grouped into three different categories:
a. Mineralocorticoids (for example, aldosterone), which are concerned with the electrolytes of the body.
b. Glucocorticoids (for example, cortisol), which are concerned with many metabolic functions and are anti-inflammatory in nature.
12. In humans, the primary sex organs are known as gonads. These organs produce sex cells (gametes) and sex hormones. (para 10-16)
13. During the first half of the menstrual cycle, the ovaries produce estrogens. During the second half, they produce progesterone. These hormones are concerned with female sexuality and with the preparation of female sex organs for reproduction. (para 10-17)
14. The testes produce the male sex hormones known as androgens (for example, testosterone). These hormones are concerned with male sexuality. (para 10-18)
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