29 - Collin College

29 - Collin College

Lab Exercise 33 Endocrine System 1 Major Endocrine Organs 2 Figure 16.1 Hormones

3 Hormones chemical substances secreted by cells into the extracellular fluids Regulate the metabolic function of other cells The precise response depends on the type of the target cell Target Cell Specificity

4 Hormones circulate to all tissues but only activate cells referred to as target cells Target cells must have specific receptors to which the hormone binds Gross Anatomy -Hypophysis

Pituitary gland two-lobed organ that secretes nine major hormones Neurohypophysis posterior lobe (neural tissue) and the infundibulum Receives, stores, and releases hormones from the hypothalamus Adenohypophysis anterior lobe, made up of glandular tissue Synthesizes and secretes a number of hormones

5 Pituitary (Hypophysis) 7 Figure 16.6 Pituitary-Anterior Lobe 8

There is a vascular connection, the hypophyseal portal system, consisting of: The primary capillary plexus The hypophyseal portal veins The secondary capillary plexus Adenophypophyseal Hormones 9

The six hormones of the adenohypophysis: Abbreviated as GH, TSH, ACTH, FSH, LH, and PRL Activity of the Adenophypophysis 10 The hypothalamus sends a chemical stimulus to the anterior pituitary

Releasing hormones stimulate the synthesis and release of hormones Inhibiting hormones shut off the synthesis and release of hormones Activity of the Adenophypophysis 11 The tropic hormones Stimulates an endocrine gland instead

of a target organ. They are: Thyroid-stimulating hormone (TSH) Adrenocorticotropic hormone (ACTH) Follicle-stimulating hormone (FSH) Luteinizing hormone (LH) Thyroid Stimulating Hormone (Thyrotropin) 12

Stimulates the normal development and secretory activity of the thyroid Triggered by hypothalamic thyrotropinreleasing hormone (TRH) Adrenocorticotropic Hormone (Corticotropin) 13

Stimulates the adrenal cortex to release corticosteroids Triggered by hypothalamic corticotropinreleasing hormone (CRH) in a daily rhythm Gonadotropins 14 Gonadotropins follicle-stimulating hormone (FSH) and luteinizing hormone (LH)

Regulate the function of the ovaries and testes FSH stimulates gamete (egg or sperm) production Triggered by the hypothalamic gonadotropin-releasing hormone (GnRH) Functions of Gonadotropins

15 In females LH promotes synthesis and release of estrogens and progesterone In males LH stimulates synthesis of testosterone by the testes Adenohypophysis- Growth Hormone (GH)

16 Stimulate most cells, but target bone and skeletal muscle Promote protein synthesis and encourage the use of fats for fuel Dwarfism, gigantism, acromegaly Prolactin (PRL)

17 In females, stimulates milk production by the breasts Regulated by the hypothalamic prolactinreleasing hormone (PRH) and prolactininhibitory hormone (PIH) Pituitary - Posterior Lobe

The posterior lobe is a downgrowth of hypothalamic neural tissue Has a neural connection with the hypothalamus (hypothalamic-hypophyseal tract) Nuclei of the hypothalamus synthesize oxytocin and antidiuretic hormone (ADH) These hormones are transported to the posterior

pituitary 18 The Posterior Pituitary and Hypothalamic Hormones ADH stimulates reabsorption of water from the urine Produced by the supraoptic nuclei of the hypothalamus

Oxytocin stimulates smooth muscle contraction in breasts and uterus Produced by the paraventricular nuclei of the hypothalamus 19 Thyroid Gland Consists of two lateral lobes connected by the isthmus

20 Thyroid Gland 21 Figure 16.8 Thyroid Hormone Consists of two related iodine-containing

compounds T thyroxine has four iodine atoms 4 T triiodothyronine; has three iodine atoms 3 22 Effects of Thyroid Hormone

TH is concerned with: Increasing metabolic rate Heat production Cellular oxidation Hyperthyroidism Hypothyroidism

23 Calcitonin 24 Produced by the parafollicular, or C, cells Lowers blood calcium levels Antagonist to parathyroid hormone

(PTH) PART 2 25 Parathyroid Glands 26

Tiny glands embedded in the posterior aspect of the thyroid PTH (parathormone) increases the level of calcium in the blood Parathyroid Glands 27 Figure 16.11 Effects of Parathyroid Hormone

28 PTH release increases Ca2+ in the blood as it: Stimulates osteoclasts to digest bone matrix Enhances the reabsorption of Ca 2+ and the secretion of phosphate by the kidneys Increases absorption of Ca2+ by

intestinal mucosal Hyperparathyroidism Hypoparathyroidism Effects of Parathyroid Hormone 29 Figure 16.12 Adrenal (Suprarenal) Glands

30 Adrenal glands paired, pyramidshaped organs atop the kidneys Structurally and functionally, they are two glands in one Adrenal medulla neural tissue that acts as part of the SNS Adrenal cortex glandular tissue Adrenal Cortex

Synthesizes and releases steroid hormones called corticosteroids Different corticosteroids are produced in each of the three layers Zona glomerulosa mineralocorticoids (chiefly aldosterone) Zona fasciculata glucocorticoids (chiefly cortisol) Zona reticularis gonadocorticoids (chiefly androgens) 31

Aldosterone 32 Electrolyte balance in extracellular fluids Stimulates reabsorption of Na+ by the kidneys

Stimulates secretion of K+ by the kidney Glucocorticoids (Cortisol) 33 Help the body resist chronic stress by: Keeping blood sugar levels relatively constant

Cortisone, hydrocortisone, corticosterone: Rises in blood glucose, fatty acids, and amino Gonadocorticoids (Sex Hormones) 34

Most gonadocorticoids secreted are androgens (male sex hormones), and the most important one is testosterone Androgens contribute to: The onset of puberty The appearance of secondary sex characteristics Sex drive in females Adrenal Medulla

35 Secrete epinephrine and norepinephrine Secretion of these hormones causes: Blood glucose levels to rise Blood vessels to constrict The heart to beat faster Blood to be diverted to the brain, heart, and skeletal muscle Pancreas

Mixed gland, which has both exocrine and endocrine cells Acinar cells produce an enzyme-rich juice used for digestion (exocrine product) Pancreatic islets (islets of Langerhans) produce hormones (endocrine products) The islets contain two major cell types:

Alpha () cells that produce glucagon Beta () cells that produce insulin 36 Insulin and Glucagon 37 Glucagon major target is the liver, where it promotes:

Release of glucose to the blood from liver cells Insulin: Lowers blood glucose levels Enhances transport of glucose into body cells Gonads: Female

38 Paired ovaries in the abdominopelvic cavity produce estrogens and progesterone and the ova Estrogen: Appearance of secondary sexual characteristics Breast development and cyclic changes in the uterine mucosa Gonads: Female

39 Progesterone: Cycling changes of the uterine lining Keeps pregnancy Prepares breast for lactation Gonads: Male

40 Testes located in an extra-abdominal sac (scrotum) produce testosterone Testosterone: Initiates maturation of male reproductive organs Causes appearance of secondary sexual characteristics and sex drive Is necessary for sperm production Maintains sex organs in their functional state

Pineal Gland 41 Small gland hanging from the roof of the third ventricle of the brain Secretory product is melatonin Melatonin is involved with: Day/night cycles

Physiological processes that show rhythmic variations (body temperature, sleep, appetite) Thymus 42 Lobulated gland located deep to the

sternum Secrete thymosins These hormones are essential for the development of the T lymphocytes (T cells) of the immune system Microscopic anatomy of the glands 43 Thyroid gland

Follicles simple squamous or cuboidal cells Colloid contain thyroglobulin, T3 and T4 Parafollicular cells (C cells) Between follicles Secrete calcitonin Microscopic anatomy of the glands 44

Parathyroid Fibrous capsule surrounds the organ Chief cell Small cells, round nuclei, arranged in clusters, secret PTH Oxyphil cells Lager than chief cells Scattered Unknown function Microscopic anatomy of the glands

45 Pancreas Exocrine acini Darker cells Endocrine with Islets of Langehans Beta cells located at the center and secrete insulin Alpha cells located at the periphery and secrete glucagon

Microscopic anatomy of the glands 46 Anterior Pituitary gland Chromophils Acidophils- reddish-brown. GH and PRL Basophils deep-blue. Tropic hormones Chromophobes

Do not take collor (Pale) Controversial role Microscopic anatomy of the glands 47 Posterior pituitary gland Nerve fibers Pituicytes (glial cells)

Microscopic anatomy of the glands 48 Adrenal gland- cortex Zona glomerulosa outermost, spherical clusters of cells, secrete mineralocorticoids Zona fasciculate Next layer, cells arranged in parallel cords, secrete glucocorticoids

Zona reticularis Inneremost, cells arranged in branches, produces mainly sex hormones Microscopic anatomy of the glands 49 Adrenal gland medulla The core of the gland

Modified neurons Secrete E and NE Microscopic anatomy of the glands 50 Ovary Vesicular follicle Ovum

Microscopic anatomy of the glands 51 Testes Seminiferous tubules Produce sperm Interstitial cells Between seminiferous tubules. Secrete testosterone

Cats Glands to Identify Thyroid Thymus Pancreas Adrenal Gonads Testes Ovaries 52

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