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 :
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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)