Download Endocrine ,cells are distributed in three different ways

Endocrinology
Endocrine tissue, is made up essentially of cells that synthesize
hormones and release them at specific time in small amounts
into the connective tissue or vascular system. So the endocrine
cells lie near the blood capillaries .
Hormones travel through the blood to the target cells, some
hormones act only on one type of cells or on one organ, while
others may have wide spread effects.
Chemically hormones can be classified to:1-Steroid hormones: such as estrogen ,testosterone, progesterone
, steroid hormones, corticosteroids.
2-Peptide hormones: hypothalamus hormones, glucagon,
insulin, parathyroid hormones.
3-Protein hormones: GH , LH, FSH, TRH.
4- Hormones derived from Tyrosine: adrenaline, nor adrenaline,
thyroxin, triiodothyronine.
Along with the nervous system the endocrine organs coordinate
and control the metabolic activities and the internal environment
of the body.
Endocrine ,cells are distributed in three different ways:-
A-Groups of endocrine cells may be present in organs that have
other functions , such as the islets of pancreas, interstitial cells
of the testis, the follicles and corpora lutea of the ovary , some
cells of the kidney ,and of the thymus ,and the placenta.
B-Isolated endocrine cells may be distributed in the epithelial
lining of an organ, such as the cells in the gut , and the
epithelium of respiratory passages.
C-Some organs are entirely endocrine in function, they are
referred as endocrine glands, or ductless glands those include
pituitary gland(hypophysis),thyroid gland, parathyroid glands ,
adrenal glands(suprararinal glands), pineal gland(pineal body).
The hypothalamus:Is apart of the brain base near the pituitary gland, connect with it
by the infundibular stalk.
The hypothalamus is the source of many hormones or factors
(what is the difference between the hormone and the factors ?)
which are secreted from specialized cells and act as releasing or
inhibiting factors (hormones) to the pituitary hormone. So the
hypothalamus regulated and control the pituitary secretion.
These hormones (factors) are:1-Growth hormone Releasing Factor (GRF) or Somatotrophine
Releasing Factor (SRF)
2- Growth hormone Inhibiting Hormone(GIH) or (SIH)
3-Corticotrophine Releasing Factor (CRF)
4-Thyroid stimulating hormone Releasing Hormone or
Thyrotrophin Releasing Hormone (TRH)
5-Prolactin Releasing Factor (PRF)
6- Prolactin Inhibiting Factor (PIF)
7-Gonadotrophin Releasing Hormone (Gn-RH):a-Luteinizing hormone Releasing Hormone (LRH)
b-Follicle stimulating hormone Releasing Hormone(FRH)
8-Melanocyte Releasing Hormone(MRH) or Melanocyte
stimulating hormone Releasing Hormone(MSH-RH)
9- Melanocyte Inhibiting Hormone(MIH) or Melanocyte
stimulating hormone Inhibiting Hormone(MSH-IH)