endocrine system - minia.edu.eg · dr. sara mohammed naguib assistant professor of histology minia...
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Endocrine system
By
Dr. Sara Mohammed Naguib Assistant professor of Histology
Minia university
Characters of endocrine gland:
=Sites of synthesis and secretion of hormones.
= Composed of secretory cells of epithelial origin
supported by CT.
= Cells are polyhedral and arranged in irregular cords
or clumps.
= Thin highly vascular CT rich in fenestrated blood
capillaries.
=Ductless.
Pituitary gland
Main endocrine organ.
Affects every organ directly or indirectly.
Site: sella turcica and connected with brain by
infundibular stalk.
Have neural and non neural components.
Parts:
1- Anterior lobe "adenohypophysis".
2-Posterior lobe "neurohypophysis".
Pars Nervosa
-No secretory cells. It consists of:
1. Unmyelinated axons of secretory neurons from
supraoptic and paraventricular nuclei of hypothalamus. Some
axons end blindly in median emenince of hypoyhalamus,
other extend to lower region of posterior lobe.
2. Herring bodies: fusiform swellings of terminal ends of
unmyelinated axons filled with neurosecretory granules.
3. Pituicytes "glial cells": supportive.
Thyroid gland
Formed of 2 lobes connected by isthmus.
Thyroid parenchyma: Formed of thyroid follicles which are spherical with
lumen filled with gelatinous "colloid". They are lined with simple cuboidal
epithelium and are of "2 types":
Follicular or principal cells: Cuboidal cells with central rounded nucleus
and junctional complexes between cells.
Function: synthesis thyroid hormones (T3 and T4).
Parafollicular or C cells: present in the interfollicular spaces. Paler
than follicular cells so termed "clear or C".
Function: Synthesis of calcitonin hormone "lowers serum Ca level by
inhibiting bone resorption".
Parathyroid gland
4 small bodies embedded in posteromedial aspect of thyroid
gland.
Parynchema:
3 types of cells separated by fenestrated blood capillaries.
I. Chief or principal cells
II. Oxyphil cells
III. Adipose cells:
Suprarenal (adrenal) gland
Small paired glands lie on superior pole of kidney and
embeded in adipose tissue.
Parynchema:2 zones different embryologically and
functionally:
outer cortex.
Inner small medulla.
Adrenal cortex: formed of three zones: Zona
glomerulosa , Zona fasciculata &Zona reticularis