endocrine system

Endocrine system –
The endocrine system consists of cells jues and organs that synthesIze and secrete hormones directly into the blood and lymph capiliaries as ,the result,the endocrine glands are ductless further more. The it s In most endocrine organs are arranged into cords and clumps, and surrounded by an extensive capillary network.
Hypophysis (pituitary gland):
Adenohypophsis
This part consists of three part;pars distalis,pars tuberalis,and, pars intermedia.
Pars details:
The main components of pars distalis are cords of epithelial cells interspersed with capillaries the hormons produced by these cells are stored as secretory granules the few fibroblasts that are present produce reticular fibers that support the cords of hormons secreting cells the pars distalis accounts for 75% of the mass of the hypophysis .common stains allow the recognition of three cell types in pars distalis:chromophobes and two types of chromophils (called basophil and aeidophil according to their affinity for basic and acid dyes,respectiyely).chromopbobes do not stain intensely.
Pars tuberalis The pars tuberalis is afunnel-shaped region surrounding the infundibulum of the neurohypophysis most of the cells of the pars tuberalis secrete gonadotropins (follicle-stimulating hormone and luteinizing hormone) and are arranged in cords alongside the blood vessels.
Pars intermedia
A region made up of cords and follicles of weakly basophile cells that contain small secretory granules.the melanocyte-stimulating hormone is probably produced in the intermediate zone.
Neurohypophysis:
The neurohypopysis consists of the pars nervosa and the neural stalk. Which is composed of some 100.000 unmylinated axons of secretory neurons. The secretory neurons have all the charaeteristics of typical neurons, and well-developed Nissl bodies related to the production of the neurosecretory material although this part consist mainly of axons from hypothalamic neurons, about 25% of its volume consists of specific type of highly branched glial cell called pituicyte.
Adrenal glands
The adrenal glands are paired organs that are situated near the superior pole of the kidney, embeded 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 cell.
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 giomcrulosa 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 usuaaly 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
Tins 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
THYROID GLAND
This endocrine gland, located in the cervical region, is made up of two lateral lobes united by an isthmus. It is surrounded by a connective tissue capsule and is divided into Iobules by septa. The gland contains follicles that are the basic histological units of the thyroid. Each follicle consists of a simple epithelial sphere containing a gelatinous colloid. A network of fenestrated capiIlaries surrounds each follicle. The sizes of the follicles as well as the heights of the epithelial cells can be quit variable.
Follicular Cells
The epithelial cells of the thyroid follicle rest on a basal lamina , Each cell has abundant rER, large Golgi apparatus, secretory granules and lysosomes. Thus they have the characteristics of cells that synthesize, secrete, absorb and digestion proteins.


Parafollicular cells:
These are also Known as C cells, They are found either as clusters of cells between follicles or part of the follicular epithelium. When they are part of the epithelium, the cytoplasm of the C cells is not in contact with the colloid. The cells contain numerous secretory granules that contain the hormone calcitonin.
PARATHYROID GLANDS
These are small glands attached to or even embedded in the thyroid gland. Each gland is encased in a connective tissue capsule. Septa of connective tissue extend into
The glands and merge with reticuler fibers
Two types of cells the chief (princepile and oxyphil from the parenchyma of the parethyroid. The clusters or cords of cells are richly endowed with capillaries.
Chief Cells:
Pale staining small cells with slight acidophilic cytoplasm. They have secretory granules containing parathyroid hormone in the cytoplasm. The amount of secretory granules in the cytoplasm determines if the cells stains are dark (active) or light (inactive).
Parathyroid hormone stimulates the reabsorption of the classified bone matrix by osteoclasts and the release of Ca2+ into the blood stream.
Oxyphil Cells:
These cells are larger than chief cells and occur either singly or in clusters. The cytoplasm in rich in mitochondria and is eosinophilic. The function of this cell type is not known.