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Endocrine System

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on 28 January 2014

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Transcript of Endocrine System

The Endocrine System
The Thyroid Glands
a butterfly-shaped gland located at the base of the neck and wrapped around the lateral sides of the trachea
produces 3 major hormones:
The Endocrine Glands
Glands are composed of cells that specialize in creating highly complex chemical substances called hormones.
Some glands pour out their secretion through tubes; duct glands.
Other glands secretes hormones directly into the bloodstream; ductless or endocrine glands.
A hormone is a secretion of a gland that is carried by the blood all over the body and regulates certain body processes.
Hormones act as "messengers", and are carried by the bloodstream to different cells in the body, which interpret these messages and act on them.
In the normal organism, there is a delicate balance of hormones present in the blood stream.
Excess Secretion- hyperfunction
Inadquate secretion-hypofunction
The Pituitary Gland
located in the center of the skull
about the size of a pea
sometimes called "the master gland"
The hypothalamus is a tiny cluster of brain cells just above the pituitary gland, which transmits messages from the body to the brain
Hypophyseal veins are veins that receive hormones from the pituitary gland
The pituitary gland has two distinct parts, the anterior and the posterior lobes, each of which releases different hormones that affect bone growth and regulate activity in other glands.
The anterior lobes secretes several hormones
One of these are growth hormones which promote and control normal increase in size and body
excess and under secretion of the growh hormones
Other hormones produced by Anterior lobe:
Gonadotrophic hormones
Adenotrophic-cotrophic hormones
Thyrotrophic hormones
Lactogenic hormone (prolactive)
The posterior lobe produces two hormones, vasopressin and oxytocin. These hormones are released when the hypothalamus sends messages to the pituitary gland through nerve cells.

Vasopressin is also known as antidiuretic hormone (ADH). It acts on the kidney to conserve water and is important in fluid and electrolyte balance.

Oxytocin stimulates the contraction of the smooth muscles of the uterus, which is important during childbirth. Oxytocin also contracts the smooth muscle of the breast for milk production.
Triiodothyronine (T3)
Thyroxine (T4)

influences the rate of body metabolism especilly oxidative or respiratory processes in all cells of the body
delivered to the blood and circulates in extremely small amounts
a decrease in this lowers metabolic activity and an increase secretion speeds up activity
Thyroxin deficiency, if severe, result in myxedeme, a disease characterized by decreased bodily vigor, sluggish mentality,puffing of the skin, and often anemia.
Goiter, a swelling of the thryroid gland and of the neck region is a manifestation of undersecretion of the thyroid hormone.
Oversecretion of the thyroxin leads to a condition called hyperthyroidism- characterized by loss of weight, nervousness and irritability, fast pulse rate, and excessive sweating
It may alo result in exopthalmic goiter- symptoms are protrusion of the eyeball, high blood pressure, nervous tension, irritability, profuse sweating, loss of weight and fatigue.
Undersecretion of this hormone during infancy or early childhood causes cretinism, a condition marked by stunted physical and mental growth. The child becomes a mentally subnormal dwarf called a cretin.
released when calcium ion levels in the blood rise above a certain set point.
functions to reduce the concentration of calcium ions in the blood by aiding the absorption of calcium into the matrix of bones.
its function is usually not significant in the regulation of normal calcium homeostasis
increases the basal metabolic rate and, thus, increases the body's oxygen and energy consumption
acts on the majority of tissues within the body
The Parathyroid Glands
4 small masses of glandular tissue found on the posterior side of the thyroid gland
secrete parathormore

a hormone necessary to control the balance of various minerals in the bloodstream especially calcium
essential to the maintenance of proper level of calcium in the blood and for the control of calcium metabolism in the cells
a slight deficiency of this hormone causes tension and irritability
if there is an oversecretion of parathormone in the blood, calcium is removed from the bones and the excess calcium is excreted
if the mineral balance is not maintained, the organism cannot survived for long
The Thymus
a soft, triangular-shaped organ found in the chest posterior to the sternum
continues to grow in size from infancy to puberty
"gland of childhood"- inhibits sexual development during childhood
produces hormones called thymosins
help to train and develop T-lymphocytes during fetal development and childhood
The T-lymphocytes produced in the thymus go on to protect the body from pathogens throughout a person’s entire life
The thymus becomes inactive during puberty and is slowly replaced by adipose tissue throughout a person’s life.
The Adrenals
a pair of roughly triangular glands found immediately superior to the kidneys
The adrenal glands are each made of 2 distinct layers, each with their own unique functions: the outer adrenal cortex and inner adrenal medulla
Adrenal Cortex
essential to life
an amazing endocrine factory- it produces very many different hormone
cortical hormones in 3 classes: glucocorticoids, mineralocorticoids, and androgens.
have many diverse functions, including the breakdown of proteins and lipids to produce glucose
also function to reduce inflammation and immune response
a group of hormones that help to regulate the concentration of mineral ions in the body
act primarily in regulating salt and water balance
are produced at low levels in the adrenal cortex to regulate the growth and activity of cells that are receptive to male hormones
In adult males, the amount of androgens produced by the testes is many times greater than the amount produced by the adrenal cortex, leading to the appearance of male secondary sex characteristics
Adrenal medulla
secretes adrenalin also known as epinephrine and nor-adrenalin or nor-epinephrine
Adrenalin is referred to as the emergency hormone because it enables individual to cope with emergency situations
Secretion of Adrenalin causes:

an increase in the glucose content of the blood
a decrease in the glycogen content of the liver
an increase in muscular power
resistance to fatigue
makes the pupil of the eyes dilate
the hair "stand on end"
skin blanch
if there is a lock of these hormones, sodium and water are excreted in excessive amounts and potassium is lost from the cell
decrease in blood volume and lowering of blood pressure
drop in blood sugar
Hyper-functioning of the adrenal cortex caused by tumors
Islets of Langerhans
group of cells located in the pancreas
Within these islets are 2 types of cells—alpha and beta cells
secrete insulin which is needed in the regulation of blood sugar by the the cells
control the metabolism of glucose
Under-secretion of insulincauses disease known as sugar diabetes or diabetes melitus due to abnormally large amounts of sugar in the blood plasma
there is no known cure for diabetes but periodic injection of insulin counteracts the symptoms
Excess of insulin causes the blood sugar level drops so low- cells of the brain are affected and the person suffers from insulin shock. Convulsion, unconsciousness and death may follow
The Gonads
ovaries in females and testes in males—are responsible for producing the sex hormones of the body
These sex hormones determine the secondary sex characteristics of adult females and adult males.
a pair of ellipsoid organs found in the scrotum of males that produce the androgen testosterone in males after the start of puberty
Testosterone has effects on many parts of the body, including the muscles, bones, sex organs, and hair follicles
This hormone causes growth and increases in strength of the bones and muscles, including the accelerated growth of long bones during adolescence
During puberty, testosterone controls the growth and development of the sex organs and body hair of males, including pubic, chest, and facial hair. In men who have inherited genes for baldness testosterone triggers the onset of androgenic alopecia, commonly known as male pattern baldness.
a pair of almond-shaped glands located in the pelvic body cavity lateral and superior to the uterus in females.
The ovaries produce the female sex hormones progesterone and estrogens.
Progesterone is most active in females during ovulation and pregnancy where it maintains appropriate conditions in the human body to support a developing fetus.
Estrogens are a group of related hormones that function as the primary female sex hormones
The release of estrogen during puberty triggers the development of female secondary sex characteristics such as uterine development, breast development, and the growth of pubic hair. Estrogen also triggers the increased growth of bones during adolescence that lead to adult height and proportions
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