UB Endocrine System Lab Exercise 3 PDF

University of Bridgeport 1. Lab Exercise 3: Endocrine System Objectives: This week’s laboratory exercise was designed to prepare students to learn...

University of Bridgeport 1. Lab Exercise 3: Endocrine System Objectives: This week’s laboratory exercise was designed to prepare students to learn the Endocrine System. By the end of the lab, students should know: 1. Identify the major structures and glands of the endocrine system and the location of each. 2. List the hormones released by each endocrine gland and the target(s) and effect(s) of each. 3. Identify the growth and microscopic anatomy of specific endocrine organs and glands. List of Materials: This lab requires each student to have in addition to their normal supplies: 1. Personal Laptop/Table (No chrome) 2. Pen/Pencil 3. Notebook 4. Models and Model Posters. University of Bridgeport 2. Overview of the Endocrine System: The endocrine system works with the nervous system to maintain homeostasis and to regulate the functions of cells throughout the body. It consists of endocrine glands, organs, and tissues that secrete hormones. Hormones are powerful chemical substances released into the blood or interstitial fluid. The target specific cells produce a response. The release of hormones may be triggered by the content of the blood (humoral control), by other hormones (hormonal control), or by an action potential or nerve impulse (neural control). Hypothalamic control: The hypothalamus is a region of the forebrain that plays a major role in homeostasis, including acting as the control center for the autonomic nervous system by regulating body temperature, appetite, thirst, sleep cycles, and other functions. It also regulates the release of hormones from the anterior pituitary gland. The hypothalamus has a portal system that sends releasing and inhibiting hormones directly to the anterior pituitary. The hypothalamic control of the posterior pituitary functions differently from that of the anterior pituitary. Neuron cell bodies in the hypothalamus produce two hormones: antidiuretic hormone (ADH) and oxytocin (OT). These hormones are transported along the axons to axon terminals in the posterior pituitary, where they are stored until release. Figure 1. The endocrine system. University of Bridgeport 3. Figure 2. Hormones controlled by the hypothalamus. The hypothalamic control of the posterior pituitary functions differently from that of the anterior pituitary. Neuron cell bodies in the hypothalamus produce two hormones: antidiuretic hormone (ADH) and oxytocin (OT). These hormones are transported along the axons to axon terminals in the posterior pituitary, where they are stored until release. University of Bridgeport 4. Figure 3. Hormones controlled by the hypothalamus. In the figure above, it summarizes the releasing and inhibiting hormones that travel through the portal system from the hypothalamus to the anterior pituitary. Note that of the six hormones secreted by the anterior pituitary, four are tropic, meaning that they regulate other endocrine glands via negative feedback. Table 1. Pituitary Hormones of the Endocrine System. Hormone Secreted by Target(s) Effect(s) Growth hormone Anterior pituitary Liver, adipose, Stimulates growth and protein synthesis (GH) muscle, bone and cartilage Prolactin (PRL) Anterior pituitary Mammary glands Milk production Thyroid-Stimulating Anterior pituitary Thyroid gland Stimulates the thyroid gland to secrete T3 and T4 hormone (TSH) Adrenocorticotropic Anterior pituitary Adrenal Cortex Development and growth of adrenal cortex. Release of hormone (ACTH) adrenal cortex hormones and catecholamines. Luteinizing hormone Anterior pituitary Gonads In males, stimulates the interstitial cells to produce (LH) testosterone. In females, it stimulates ovulation and production of estrogen and progesterone. Follicle-stimulating Anterior pituitary Gonads In males, it indirectly stimulates sperm production in the hormone (FSH) seminiferous tubules of the testes. In females, stimulates development of follicles and oocytes in the ovaries and estrogen release. Antidiuretic hormone Posterior pituitary Kidney Stimulates water retention. Decreases urine output. Maintains (ADH) blood volume. Oxytocin (OT) Posterior Pituitary Kidney Stimulates uterine contractions. Milk flow (let-down reflex). University of Bridgeport 5. Table 2. Thyroid and Parathyroid Hormones Hormone Secreted by Target(s) Effect(s) Calcitonin Thyroid Bone and Kidney Causes decrease in blood calcium ion levels by: - Stimulating osteoblast and inhibiting osteoclast activity. -Causing secretion of excess calcium into urine. Parathyroid hormone Parathyroid Bone, kidney, and Causes increase in blood calcium ion levels by: (PTH) small intestine -Activating osteoclasts -Causing kidney tubules to reabsorb calcium back into the bloodstream -Promoting calcium absorption through the small intestine Triiodothyronine (T3) Thyroid All cells -Set basal metabolic rate. and thyroxine (T4) -Promote growth and development. -Regulate body temperature. Table 3. Adrenal Hormones Hormone Secreted by Target(s) Effect(s) Aldosterone Adrenal cortex Kidney -Causes retention of sodium ions and water to increase blood volume. -Causes potassium and hydrogen ion secretion into urine. -Regulates blood pressure. Androgens Adrenal cortex Reproductive organs, brain, -Can be converted to testosterone in the bone, and skeletal muscle circulation. Development of secondary sex characteristics such as pubic hair. Cortisol Adrenal cortex Liver, muscles, adipose -Works with thyroid hormones to regulate tissue and white blood cells glucose metabolism -Helps the body respond to long-term stress -Inhibits the inflammatory response Catecholamines Adrenal medulla All cells -Increase heart rate -Dilate airways -Vasoconstriction of blood vessels to the skin, digestive and urinary systems -Dilate pupils -Increase metabolic rate University of Bridgeport 6. Table 4. Pancreatic Hormones Hormone Secreted by Target(s) Effect(s) Insulin Pancreas (beta cells) Most cells -Decreases blood glucose levels (moves glucose from bloodstream into cells and promotes glycogen formation in liver and skeletal muscle) Glucagon Pancreas (alpha cells) Liver, muscles, and adipose -Increase blood glucose levels (causes tissue breakdown of glycogen and release of glucose into bloodstream Somatostatin Pancreas (delta cells)_ Alpha and beta cells of Inhibits insulin and glucagon secretion. pancreatic islets Table 5. Other Hormones Hormone Secreted by Target(s) Effect(s) Thymosin Thymus T lymphocytes Promotes T lymphocyte maturation Thymopoietin Thymus T lymphocytes Promotes T lymphocyte maturation Testosterone Testes Male reproductive organs Development and maintenance of male and other target tissues secondary sex characteristics Progesterone Ovaries Uterus and other target Prepares the body for pregnancy tissues Supports fetal development Estrogens Ovaries Female reproductive organs Development and maintenance of female secondary sex characteristics Melatonin Pineal gland Reticular formation of the Regulates the sleep/wake cycle brainstem Promotes sleep Anatomy of the Endocrine System: Hypothalamus, Pituitary and Pineal Glands: The hypothalamus, pituitary and pineal glands are located within the cranial cavity. The hypothalamus is part of the diencephalon. It is connected to the pituitary gland via the infundibulum. The pituitary gland (hypophysis) sits within the sella turcica and is composed of two distinct portions anterior and posterior. The anterior (adenohypophysis) is composed of true glandular epithelium , while the posterior (neurohypophysis) consists of nervous tissue. The anterior pituitary contains acidophil cells that produce GH and PRL. Basophils produce TSH, ACTH, FSH, and LH. The pineal gland is located in the posterior portion of the diencephalon. University of Bridgeport 7. Figure 4. Hypothalamus, pituitary and pineal gland. (a) head, midsagittal view; (b) structures of the pituitary gland; (c ) photomicrograph of the pituitary gland (160x) Thyroid, parathyroid and thymus: The thyroid gland is located in the anterior portion of the neck. It consists of right and left lobes connected by the isthmus. The gland is composed of follicles made of follicular cells that produce the thyroid hormones. Each follicle is filled with a fluid known as colloid, which contains precursor materials used to make thyroid hormones. Parafollicular cells fill the spaces between the follicles and secrete the hormone calcitonin. Most people have four parathyroid glands, located on the posterior surface of the thyroid. Parathyroid glands contain two types of cells. Hormone-secreting cells known as chief cells (also called parathyroid cells) are the most predominant and produce parathyroid hormone (PTH). Oxyphil cells are the second type, their function is unknown. The thymus is located in the mediastinum and it is rather large during infancy and childhood but shrinks during adulthood. It is divided into encapsulated lobules, each with a cortex and medulla. The epithelial reticular cells secrete the hormones thymosin and thymopoietin. University of Bridgeport 8. Figure 5. Parathyroid (a) gross structure (b) photomicrograph of parathyroid gland embedded in the thyroid (c ) photomicrograph of parathyroid tissue. University of Bridgeport 9. Figure 6. Thymus (a ) comparison of newborn and adult (b) gross structure (c ) photomicrograph of the thymic tissue showing a portion of a lobe. Pancreas: The pancreas consist of a head, body and tail (located posterior of the stomach). Clusters of endocrine cells form pancreatic islets (islets of Langerhans), which are surrounded by acinar cells that secrete digestive enzymes into the small intestine by way of the pancreatic duct. The islet contain three main types of hormone-producing cells: -Alpha cells secrete glucagon. -Beta cells secrete insulin. -Delta cells secrete somatostatin. University of Bridgeport 10. Figure 7. Pancreas (a) gross structure (b) histology of a pancreatic islet (c ) photomicrograph of a pancreatic islet Adrenal Glands: There are two adrenal glands. Each gland is surrounded by a capsule and sits on the superior surface of each kidney. The adrenal glands have two distinct regions: the cortex and medulla. The adrenal cortex is made up three zones: -Zona glomerulosa cells produce the mineralocorticoid aldosterone. -Zona fasciculata cells produce the glucocorticoid cortisol. -Zona reticularis cells produce the glucocorticoid cortisol and small amounts of androgenic steroids. University of Bridgeport 11. Figure 8. Adrenal gland (a) gross structure (b) histology of adrenal gland (c ) photomicrograph of adrenal gland tissue (160x) Testes and ovaries: The gonads are the primary male and female reproductive organs and are responsible for the production of the sex cells (gametes). The male gonads are the testes and the female gonads are the ovaries. Each testis is located outside of the pelvic cavity within the scrotum. The testes are divided internally into lobules, which contain several coiled seminiferous tubules where sperm are produced. Interstitial (Leydig) cells are found between the seminiferous tubules; these cells are responsible for the secretion of androgens, including testosterone. Sustentacular (sertoli) cells secrete the hormone inhibin, which is involved in regulating spermatogenesis. Other cells of the testes include sperm, spermatogenic, and myoid cells. The ovaries are located on the lateral walls of the pelvic cavity. Each ovary is divided into two regions: the cortex and medulla. The cortex contains the follicles, which are primarily responsible for the production of estrogens. The corpus luteum (an empty follicle after ovulation) secretes progesterone. University of Bridgeport 12. Figure 9. Ovary. (a) location of ovaries, (b) bisected view (c ) photomicrograph In-Lab Assignment 3: After reviewing with the instructor, complete the lab exercise. On canvas, go to “Assignments” tab and click on “In-Lab Assignment 3” This exercise is not a quiz but will be using a quiz template in order to grade automatically. Read each instruction carefully per question in order to complete the assignment. Complete this assignment before leaving class. This assignment is only open during the time of the class. You have three attempts. Answers will show at the end of the week. After completing the assignment, show the instructor or TA to mark you off. Use models to complete assignments.