Human Adrenal Glands (part of the Endocrine
System)
Knowledge of the Endocrine System is an essential part of training
in many
therapies
- such as Massage, Aromatherapy, Accupuncture, Shiatsu, and others.
This page is a simple summary of information about the Adrenal
Glands. The information on this page is likely to be sufficient
to meet the requirements of first-level courses such as ITEC Anatomy
and Physiology Exams.
The
location(s) of the Adrenal Glands:
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The human body normally* includes two
adrenal glands. |
These are located immediately anterior
to the kidneys, and are encased in a connective tissue
capsule that is usually partially
buried in an island of fat. The adrenal glands lie beneath
the peritoneum (that is, they are "retroperitoneal"). |
Click |
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for a diagram of the positions of
the Adrenal Glands - and other major endocrine
glands of the human body. |
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*
In some circumstances (e.g. in the cases of
certain types of tumours), one or more of
the adrenal glands may be surgically removed.
For further information about this see: http://www.endocrineweb.com/adrenal.html (Norman
Endocrine Surgery Clinic).
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The
Structure of the Adrenal Glands: |
The most obvious aspect of the structure of
the adrenal glands is their partitioning
into
two distinctive components:
the paler medulla (centre), and the
darker cortex (surround).
Both of these tissues contain many blood vessels,
hence they may be described as "richly vascularized". |
Adrenal Medulla |
The medulla consists
of many large columnar cells called
"chromaffin cells".
These synthesize and secrete
catecholamines.
There are also some
Ganglion cells are also observed.
Blood from throughout
the adrenal gland collects into large medullary
veins to exit
the gland. |
Adrenal Cortex |
The adrenal cortex consists of three concentric
zones of steroid-synthesizing cells: glomerulosa,
fasiculata and reticularis. Although the boundaries
between these zones are indistinct, each
of these zones has a characteristic arrangement
of cells. |
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Simple Diagram representing
the Adrenal Medulla (centre) and the Adrenal Cortex
(surround):
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Hormones
secreted by the Adrenal Glands: |
Adrenal Medulla |
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Adrenalin
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Prepares
the body for "fright, fight or flight"
and has many effects: |
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Action
of heart increased.
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Rate
and depth of breathing increased.
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Metabolic
rate increased.
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Force
of muscular contraction improves.
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Onset
of muscular fatigue delayed.
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Blood
supply to the bladder and intestines
reduced, their muscular walls relax,
the sphincters contract.
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Noradrenalin
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Similar
effects to adrenalin: |
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Constriction
of small blood vessels leading to increase
in blood pressure.
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Increased
blood flow through the coronary arteries
and slowing of heart rate.
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Increase
in rate and depth of breathing.
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Relaxation
of the smooth muscle in the intestinal
walls.
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Adrenal Cortex |
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Corticosteroids
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Glucocorticoids (e.g. cortisol, cortisone, corticosterone) |
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Utilization
of carbohydrate, fat and protein by the
body.
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Normal
response to stress.
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Anti-inflammatory
effects.
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Hypersecretion
of cortisol results in Cushings Syndrome.
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| Mineralocorticoids (e.g.
aldosterone) |
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Regulation
of salt and water balance.
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Hypersecretion
of Alderosterone decreases the potassium
in the body (affecting nerve impulse
transmission and leading to muscular
paralysis).
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This is the end of this page but an Introduction
to the Endocrine System and information about other aspects
of it -
such the Locations of and Hormones secreted
by the main Endocrine
Glands, Conditions that Affect the Endocrine
System, and a page about Diabetes are
also included
on
this
website.
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