Download Adrenal glands

General objectives : After this lecture the students must be know : 1- The importance of the endocrine system . 2- List the endocrine glands and described the main function . 3- The histological structure of the glands in this system .

Behavior objectives : The aims of this lecture are : 1- Explain the components and the main functions of the endocrine system . 2- Show the structure of the endocrine system . 3- Types and the histological structure of the endocrine glands .

Contents : 12345-

The endocrine system . Adrenal (suprarenal ) gland . Pituitary gland . Thyroid gland . Parathyroid gland .

Endocrine system The endocrine system consists of cells , tissues and organs that synthesize and secrete hormones directly into the blood and lymph capillaries. as the result ,the endocrine glands are ductless further more. The cells in most endocrine organs are arranged into cords and clumps, and surrounded by an extensive capillary network.

*Adrenal glands The adrenal glands are paired organs that are situated near the superior pole of the kidney, embedded in adipose tissue, the general histological appearance of adrenal gland is typical of an endocrine gland in which cell of both cortex and medulla are grouped in cords along capillaries , adense connective tissue capsule that covers the a renal sends thin septa to the anterior of the gland as trabeculae ,the stroma consist mainly of a rich network of reticular fibers that supports the secretory cells. The Adrenal Cortex this part of the adrenal gland is derived from the mesoderm can be divided into three zones based on the arrangement of the cells and their functions. Using cholesterol as a precursor, the cells of the adrenal cortex secrete steroid hormones the steroid hormones secreted by the cells of the adrenal cortex are not stored in the cells. It appears that the steroids are manufactured at released as needed this part can be divided into three zones: Zona glomerulosa : This zone is found right beneath the capsule. The cells are appear as clusters, have eosinophilic cytoplasm with lipid droplets. The cells of the zona glomcrulosa secrete aldosterone a mineralocorticoid important in the maintenance of electrolytes in the body. It causes the reabsorption of sodium in the kidney in exchange of potassium and hydrogen ions. This

takes place in the distal convoluted tubules and the collecting ducts of the kidney.

Zona Fasciculata : This is usually the widest zone in the cortex. The cells here are arranged in cords usually made up of one cell thick. The cuboidal cells contain numerous small lipid droplets in the cytoplasm. In routine histological preparations, the lipids were extracted and the cytoplasm appears vacuolated. Sinusoids run between the cords of cells exposing them to blood on two sides. The main hormones produced in this zone are cortisone, cortisol, and corticosterone. Zona retienlaris : The cells here are arranged in a less organized manner than those in the fasciculate. the cells have less lipid droplets but more lipofuscin pigments bodies. The cells of the reticularis produce small amounts of sex hormons. The Adrenal Medulla This portion of the adrenal gland is derived from the neuroectoderm and forms the ''Center'' of gland. It is made up of irregular cords and clusters of cells supported by a reticular fiber network. The hormones secreted by the medulla are biogenic amines and the cells are also called chromaffin cells. The chromaffin cells are actually modified sympathetic postganglionic neurons . These cells do not have processes .

Location of the adrenal (suprarenal) gland, human

Adrenal (suprarenal) gland

(LM, human adrenal cortex, stained with H&E. From left to right, capsule , zona glomerulosa, zona fasciculata, zona reticularis, medulla)