The Endocrine System
Mrs. Degl
1
The human endocrine system is made up of glands, that
secrete hormones into the blood. Hormones are
transported by the circulatory system to organs and tissues
on which they act.
Glands of human endocrine system:
1. Hypothalamus
2. Pituitary
3. Thyroid
4. Parathyroid
5. Adrenal
6. Islets of Langerhans
7. Gonads (ovaries and testes)
Mrs. Degl
2
Hypothalamus is a small part of the brain the secretes
hormones.
Pituitary Gland is located at the base of the brain. It
secretes many hormones.
1. Growth Stimulating Hormone is a pituitary hormone
that has widespread effects in the body as well as
growing long bones.
2. Thyroid Stimulating Hormone (TSH) is a pituitary
hormone that stimulates the secretion of the thyroid
hormone thyroxin.
3. Follicle Stimulating Hormone (FSH) is a pituitary
hormone that stimulates the development of follicles in
the ovaries of females. In males, it influences sperm
production.
Mrs. Degl
3
Thyroid Glands are
located in our necks. It
secretes thyroxin, which
contains iodine, and
regulates the
metabolism of the body
cells. A normal level is
essential for appropriate
mental and physical
development
Parathyroid Glands are embedded in back of the
thyroid gland. They secrete parathormone. This
controls calcium metabolism, which is required for
normal nerve function, blood clotting, and proper
growth of teeth and bones.
Mrs. Degl
4
Adrenal Glands
•An adrenal gland is located on top of each kidney.
•The outer layer is the adrenal cortex
•The inner layer is the adrenal medulla
•The adrenal cortex secretes two types of steroid
hormones.
•One type increases glucose levels in the blood.
•One type stimulates the absorption of sodium from the
kidney into the bloodstream. This affects blood
pressure.
•The adrenal medulla secretes the hormone adrenaline,
which increases the blood glucose levels and
accelerates the heartbeat and breathing rates.
Adrenaline is released during times of stress and heavy
exercise.
Mrs. Degl
5
Islets of Langerhans
•Small groups of cells that
are found throughout the
pancreas.
•Secretes the hormones
insulin and glucagon.
•Insulin promotes the
absorption of glucose into
the body.
•Glucagon increases the blood glucose level.
•Through their opposite effects, insulin and glucagon
maintains homeostasis in the body by keeping the blood
glucose levels within certain limits.
Mrs. Degl
6
Gonads
•The gonads (testes and ovaries) are endocrine
glands.
•The testes secrete testosterone, which stimulates
the growth of male sex organs, sex characteristics,
and production of sperm.
•The ovaries secrete estrogen and progesterone.
•Estrogen influences the development of the female
sex characteristics and egg production.
•Progesterone stimulates the thickening of the
uterus for pregnancy.
Mrs. Degl
7
Negative Feedback
Negative Feedback is how the endocrine system
regulates hormone levels.
•The level of one hormone in the blood stimulates
or inhibits the production of a second hormone.
•The blood level of the second hormone in turn
stimulates or inhibits the production of the first.
•TSH (secreted by the pituitary gland) and thyroxin
(secreted by thyroid) is a classic example of
negative feedback.
This helps maintain homeostasis.
Mrs. Degl
8
Disorders of the Endocrine System
•Goiter is the enlargement of the thyroid gland and
is most commonly caused by a lack of iodine in the
diet.
•Diabetes is a disorder in which the islets of
Langerhans do not secrete enough insulin into the
blood so the body’s blood glucose levels are too
high.
•Growth problems can usually be attributed to the
pituitary gland.
•Recent technology had allowed scientists to create
insulin, human growth hormone, and thyroxin to
combat some of these disorders.
Mrs. Degl
9