|
The
nervous system sends electrical messages to control
and coordinate the body. The endocrine system has
a similar job, but uses chemicals to “communicate”.
These chemicals are known as hormones. A hormone is
a specific messenger molecule synthesized and secreted
by a group of specialized cells called an endocrine
gland. These glands are ductless, which means that
their secretions (hormones) are released directly
into the bloodstream and travel to elsewhere in the
body to target organs, upon which they act. Note that
this is in contrast to our digestive glands, which
have ducts for releasing the digestive enzymes.
The
endocrine system consists of:
- pituitary
gland - secretes hormones to stimulate the adrenals,
thyroid, pigment-producing skin cells and gonads
(ovaries and testes). Also secretes
a growth hormone, an antidiuretic hormone, prolactin
(a hormone which affects milk production after childbirth)
and oxytocin (a hormone which plays a role in childbirth).
- hypothalamus
- secretes hormones that stimulate or suppress the
release of hormones in the pituitary gland.
- pancreas
- secretes insulin and glucagon, which affect the
body's absorption of glucose, the body's main source
of energy.
- adrenal
cortex - secretes hydrocortisone, which affects
metabolism. Also secretes androgen hormone and aldosterone,
which affect blood pressure and saline balance.
- thyroid
gland - secretes thyroxin, triiodothyronine
and calcitonin, which affect metabolism, body heat,
and bone growth.
- parathyroid
glands - secretes a parathyroid hormone, which
affects calcium levels in the blood.
- gonads
- the male and female reproductive glands (testes
and ovaries). The testes secrete testosterone, which
stimulate sperm production and other male characteristics.
The ovaries secrete estrogen and progesterone, which
affect many aspects of the female body, including
menstrual cycles and pregnancy.
|
caribbeanedu.com
