Endocrine System Lecture Notes 2024-2025 PDF

First Term, 2024-2025 Anatomy (ANAT231) Candidates: RC Students Lecture: By: Staff Members of Anatomy Dept. College of Medicine, IAU After participating successfully in this session and related activities, you should be able to: Enumerate the glands...

First Term, 2024-2025 Anatomy (ANAT231) Candidates: RC Students Lecture: By: Staff Members of Anatomy Dept. College of Medicine, IAU After participating successfully in this session and related activities, you should be able to: Enumerate the glands of the endocrine system Describe the position, parts, hormones, and major relations of each gland Correlate the basic anatomical data with their clinical application 2 ✓The endocrine system is a major control system of the body. ✓Through hormones, it stimulates such long- term processes as growth and development, metabolism, reproduction, and body defense. ✓Endocrine organs are either mixed glands (both endocrine and exocrine in function) or purely hormone producing (endocrine). ✓Hormones are either fat-soluble (steroid) or water-soluble (amino acid-based) hormones. 3  Purely endocrine organs: Pituitary gland Pineal gland Thyroid gland Parathyroid glands Adrenal glands: Adrenal Cortex Adrenal Medulla Endocrine cells in other organs: Pancreas Thymus Gonads (Testis & Ovary) Hypothalamus 4  It is the maestro of the endocrine system. It is pea-sized, weighing about 0.5 gram. The pituitary gland lies in the cranial cavity hanging from the hypothalamus by a stalk and is enclosed by bone (pituitary fossa of sphenoid bone). It consists of: a glandular anterior lobe (adenohypophysis): It has endocrine cells. a neural posterior lobe (neurohypophysis): It has no endocrine cells, but axon terminals from hypothalamic neurons 5 It is under the control of the hypothalamus: The anterior lobe (adenohypophysis) is connected to the hypothalamus by the hypothalamo-hypophyseal portal veins, through which hypothalamic stimulating and inhibiting hormones approach the endocrine cells of the anterior lobe. While the posterior lobe (neurohypophysis) is connected to the hypothalamus by the hypothalamo-hypophyseal tract. It is formed of axons of the hypothalamic neurons secreting oxytocin and vasopressin. These hormones are released in the posterior lobe and then transmitted by blood to the target organs. 6 It secretes 9 hormones: 1. TSH (thyroid stimulating hormone) Anterior pituitary 2. ACTH (adrenocorticotropic hormone) (adenohypophysis) 3. FSH ( follicle stimulating hormone) 4. LH ( luteinizing hormone) ________ The first four are “tropic” hormones, 5. GH (growth hormone) they regulate the function of other 6. PRL (prolactin) endocrine glands 7. MSH (melanocyte-stimulating hormone) _________________________________________________________________ 8. ADH (antidiuretic hormone), or vasopressin Posterior pituitary 9. Oxytocin (neurohypophysis) 7  clinical application Gigantism –too much GH in childhood Acromegaly – too much GH in adulthood Pituitary dwarfism – too little GH in childhood Diabetes insipidus - Less ADH 8  It is a part of the epithalamus, located at the posterior wall of the third ventricle. It is pine-cone shaped measuring about 6 mm. It has two types of cells : Pinealocytes – hormone secreting cells. Glial cells – supporting cells. In middle age, the gland commonly becomes calcified, and can be subsequently identified on radiographs and CT scans of the head (brain sand) The pineal gland produces melatonin hormone, a sex-glands inhibitor and anti-free radicals’ hormone. in children, a pineal gland tumour (which invades and destroys the gland), produces an accelerated onset of puberty (precocious puberty). 9  The thyroid gland is located in the lower anterior part of the neck. It is butterfly-shaped, formed of two lobes connected to each others by an isthmus. Each lobe is pyramidal in shape and lies lateral to the larynx, trachea, pharynx and esophagus. The isthmus lies in front of the upper trachea. The thyroid gland plays a vital role in metabolism and regulates the body’s metabolic processes. 10  Thyroid is composed of spherical follicles Follicle cells: produce thyroglobulin, the precursor of thyroid hormone (thyroxin) Colloid lumen is of thyroglobulin Parafollicular “C” cells: produce calcitonin Goiter Hyperthyroidism hypothyroidism 11  Four glands, two on each side Embedded on the posterior surface of the thyroid lobes it is composed of Chief cells: parathyroid hormone Oxyphil cells (unknown function) 12  On the upper pole of each kidney Formed of two glands Adrenal cortex Adrenal medulla The adrenal cortex is formed of three layers which produce three groups of steroid hormones: 1. Zona glomerulosa: Mineralocorticoids. 2. Zona fasciculata: Glucocorticoids. 3. Zona reticularis Sex steroids (androids) The adrenal medulla has chromaffin cells which produce catecholamines (epinephrine and norepinephrine) in response to sympathetic nervous system stimulation. Cushing syndrome 13  Gross anatomy discussed before in digestive system. The endocrine portion of the pancreas is the islets of Langerhans, scattered between the acini. The islets have the following cells: 1. Alpha cells: produce glucagon. 2. Beta cells: produce insulin. 3. dlta cells: produce somatostatin. Diabetes mellitus 14 Gonads: This will be discussed in male’s and female’s reproductive systems Thymus gland: Discussed with lymphatic system Hypothalamus This is a part of the diencephalon; it represents a higher control center for the endocrine system. Its gross anatomy will be discussed in CNS lecture. 15 16