Endocrine system part 1-1 - converted.pdf

Endocrine System (Part 1) Dr. Hayder Naji Sameer Msc in Clinical Pharmacy Endocrine System Endocrine tissue is made up of cells that release chemicals directly into bloodstream. Some organs are entirely endocrine in function. They are r...

Endocrine System (Part 1) Dr. Hayder Naji Sameer Msc in Clinical Pharmacy Endocrine System Endocrine tissue is made up of cells that release chemicals directly into bloodstream. Some organs are entirely endocrine in function. They are referred to as endocrine glands like pituitary glands, pineal body, thyroid gland, parathyroid glands, and adrenal glands.  Groups of endocrine cells may be present in organs that have other functions like islets of pancreas, the interstitial cells of the testes, the kidneys, and the follicles and corpora lutea of ovaries. Endocrine glands  The chemicals release by endocrine cells are called hormones. Hormones travel through blood to target cells. Some hormones act only on one organ or on one type of cell, while other hormones may have widespread effects. The endocrine organs co-ordinate and control the metabolic activities and the internal environment of the body. General structure of endocrine glands  Pituitary Gland The pituitary gland is located in the base of the brain. It controls many body functions and as well as other endocrine glands. Pituitary gland is divided into two major lobes: a) Anterior lobe (Adenohypophysis) b) Posterior lobe (Neurohypophysis)  Adenohypophysis (Anterior Pituitary gland)  Anterior lobe of pituitary gland It secrets many hormones: 1. Growth hormone (GH) promotes bone growth specially during adolescents. 2. Thyroid stimulating hormone (TSH) stimulates thyroid gland to secret thyroid hormone (thyroxin hormone). 3. Adenocorticotropic hormone (ACTH) acts on adrenal cortex to secret its hormones. 4. Follicle stimulating hormone (FSH) promotes ovarian follicle development and estrogen secretion in women and stimulates spermatogenesis in men. 5. Luteinizing hormone (LH) – I t stimulates the maturation of corpus luteum and progesterone secretion in women. – Leyding cell stimulation and androgen secretion in men. 6. Prolactin hormone promotes milk secretion.  Pituitary gland Histology Pars Distalis The pars distalis accounts for 75% of the adenohypophysis and has a thin fibrous capsule. The main components are cords of well-stained endocrine cells interspersed with fenestrated capillaries and supporting reticular connective tissue. Common stains suggest two broad groups of cells in the pars distalis with different staining affinities: chromophils and chromophobes. Types of cells Chromophils Chromophobes in pars distalis Percentage 48% 52% Size Larger Smaller Cytoplasm Granular Non-granular Function Hormone Act as a reserve production Chromophils are secretory cells in which hormone is stored in cytoplasmic granules. They are also called basophils or acidophils, based on their affinities for basic and acidic dyes, respectively.  Acidophils secrete either growth hormone (somatotropin) or prolactin. The basophilic cells are the corticotrophs, gonadotrophs, and thyrotrophs, with target cells in the adrenal cortex, gonads, and thyroid gland, respectively. Basophils are three types: 1. Thyotrophs secret thyroid stimulating hormone (TSH) 2. Gonadotrophs secret two hormones: a. Follicle stimulating hormone (FSH) b. Luteinizing hormones (LH) 3. Corticotrophs which secret adenocoticotrophic hormone (ACTH) Types of Acidophils Basophils chromophils Percentage 37% 11% Hormone Protein Glycoprotein Nature PAS (periodic Negative Positive acid schiff) Size Smaller Larger Granules Larger Smaller Secretion Somatotrophs (Growth hormones Mammotrophs (Prolactin) A: acidophils B: basophils C: chromophobes Pars Tuberalis The pars tuberalis is a smaller funnel- shaped region surrounding the infundibulum of the neurohypophysis. Most of the cells of the pars tuberalis are gonadotrophs. Pars Intermedia The pars intermedia is a thin zone of basophilic cells between the pars distalis and the pars nervosa of the neurohypophysis. The pars intermedia usually contains colloid-filled cysts of various sizes that represent remnants of that structure’s lumen.  Neurohypophysis (Posterior Pituitary gland) Posterior Lob of pituitary gland It lies posterior to the hypophyseal cleft It consists of three parts: 1. The median eminence: a funnel shaped downward extension of the hypothalamus 2. The infundibular stalk 3. The pars nervosa: It is connected to the base of the brain by the infundibular stalk and the median eminence  Pars Nervosa It consists of the following: 1. Unmyelinated axon of neurosecretory cells. 2. Herring bodies 3. Pituicytes 4. Fenestrated blood capillaries  Posterior lobe of Pituitary gland It secrets of two hormones: 1. Vasopressin = Antidiuretic hormone (ADH) it controls reabsorption of water by kidney tubules. 2. Oxytocin hormone it controls the contraction of the smooth muscles of uterus and also of the mammary glands. Control the secretion of pituitary gland Thank You Q1: What is the difference between acidophilic cells and basophilic cells? Q2: What is the role or function of pars Tuberalis?