Introduction to Endocrine.pptx
- 1. Dr. Maria Idrees; PT MS (RIU) DPT(TUF)
- 2. The endocrine system helps to maintain internal homeostasis through the use of endogenous chemicals known as hormones. A hormone is typically regarded as a chemical messenger that is released into the bloodstream to exert an effect on target cells located some distance from the hormonal release site. Drugs can be used as replacement therapy during hormonal deficiency—for example, insulin administration in diabetes mellitus.
- 3. Primary Endocrine Glands and Their Hormones Hypothalamus and Pituitary Gland The pituitary gland is a small, pea-shaped structure. The pituitary can be subdivided into an anterior, an intermediate, and a posterior lobe. Anterior Lobe: Secrets six important peptide hormones 1) growth hormone (GH), 2) luteinizing hormone (LH), 3) follicle-stimulating hormone (FSH), 4) thyroid-stimulating hormone (TSH), 5) adrenocorticotropic hormone (ACTH), and 6) Prolactin (Pr).
- 5. Intermediate Lobe. In mammals, there is a small intermediate lobe of the pituitary (pars intermedia) that may secrete melanocyte-stimulating hormone (MSH). Although it can influence skin pigmentation in lower vertebrates, the intermediate lobe does not produce MSH in meaningful amounts in humans. Humans can, however, produce MSH from a precursor protein (proopiomelacortin) that is synthesized in central tissues (anterior pituitary, hypothalamus) and the periphery (skin, lymphoid tissues)
- 6. Posterior Lobe Secretes two hormones: 1) Antidiuretic hormone (ADH) (Exerts its effect primarily on the kidneys, where it increases the reabsorption of water from the distal renal tubules. 2) Oxytocin (important in parturition and stimulates the uterus to contract. It also promotes lactation by stimulating the ejection of milk from the mammary glands.
- 8. Thyroid Gland The thyroid gland is located in the anterior neck region, approximately at the level of the fifth cervical to first thoracic vertebrae. The thyroid synthesizes and secretes two hormones: Thyroxine (T4) and Triiodothyronine (T3) The primary effect of the thyroid hormones is to increase cellular metabolism in most body tissues
- 9. Parathyroid Gland Parathyroid glands are small, egg-shaped structures embedded in the posterior surface of the thyroid gland. There are usually four parathyroid glands The parathyroids synthesize and release parathyroid hormone (PTH). PTH is essential in maintaining normal calcium homeostasis in the body; the primary effect of PTH is to increase the concentration of calcium in the bloodstream.
- 10. Pancreas The pancreas is located behind the stomach in the lower left area of the abdomen. This gland is unique in that it serves both endocrine and exocrine functions. The exocrine aspect of this gland involves digestive enzymes that are excreted into the duodenum. As an endocrine gland, the pancreas primarily secretes two peptide hormones: 1) Insulin (Alpha cells) and 2) Glucagon (Beta cells)
- 11. Adrenal Gland Adrenal glands are located at the superior poles of each kidney. Each adrenal gland is composed of an outer cortex and an inner medulla.
- 12. Hormones of the Adrenal Cortex Synthesizes and secretes two primary groups of steroidal hormones: 1) Glucocorticoids 2) Mineralocorticoids (controlling electrolyte and fluid levels) 3) Small amounts of sex steroids (estrogens, androgens, progesterone) are also produced. Glucocorticoids are involved in the regulation of glucose metabolism and are important in enhancing the body’s ability to handle stress. Anti-inflammatory Immunosuppressive properties
- 13. Hormones of the Adrenal Medulla synthesizes and secretes Epinephrine and Norepinephrine To prepare the body for sudden physical activity. By the fight-or-flight reaction
- 14. Gonads In men, the testes produce testosterone and similar androgens that are responsible for spermatogenesis and the secondary sexual characteristics of adult males. In women, sexual maturation and reproductive function are governed by the production of estrogens and progestins from the ovaries
- 15. Hormone Chemistry Steroid hormones share a common chemical framework that is derived from lipids such as cholesterol. (e.g sex hormones, glucocorticoids, mineralocorticoids) Peptide hormones consist of amino acids linked together in a specific sequence (3-180 amino acids, e.g T3 and T4)
- 16. Feedback Control Mechanisms in Endocrine Function
- 17. Hormone Transport Hormones are usually carried from their site of origin to the target cell via the systemic circulation. During transport in the bloodstream, certain hormones such as steroids are bound to specific plasma proteins. These protein carriers appear to help prolong the half- life of the hormone and prevent premature degradation.
- 18. Hormone Effects on the Target Cell
- 19. Assignment Steroid hormone Mechanism of action?????????? Due date: 4-11-2022
Editor's Notes
- #10: PTH increases circulating calcium levels primarily by mobilizing calcium from storage sites in bone
- #11: In the islets of Langerhans, glucagon and insulin are synthesized by alpha and beta cells, respectively.
- #19: Peptide hormones tend to bind to surface membrane receptors (site I); steroid hormones bind to cytosolic receptors (site II); and thyroid hormones bind to receptors in the cell nucleus (site III)