Download The Endocrine System

The Endocrine System
Endocrine glands:
 These are ductless, or tubeless, structures that secrete
hormones
Major glands of the endocrine system include:
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Pituitary gland
Thyroid
Parathyroid
Pineal gland
Thymus
Adrenal
Pancreas
Gonads
Pituitary Gland:
 Regulates and controls the activities of all other endocrine
glands
 Known as the “Master Gland”
 Pea-sized gland located at the midpoint of the skull
 Three sections or lobes:
o Anterior
o Intermediate
o Posterior
Anterior Lobe:
 Means “front”
 Hormones produced by this lobe control a range of body
functions.
 They regulate metabolic activities of cells and stimulate
other endocrine glands.
 Anterior lobe produces 6 hormones:
o Somatotropic, or growth, hormone stimulates normal
body growth and development by altering chemical
activity in body cells.
o Thyroid-Stimulating hormone (TSH) stimulates
hormone productions by the thyroid glands.
o Adrenocorticotropic hormone (ACTH) stimulates
hormone production by the adrenal glands.
o Gonadotropic Hormones:
 Follicle-stimulating hormone (FSH)
 Triggers the development of egg cells, or ova, in the
ovary and stimulates cells in the ovary to produce
estrogen, a female sex hormone.
 Stimulates the testes to produce sperm cells
 Luteinizing hormone (LH)
 Responsible for ovulation, or the release of a mature
ovum from the ovary
 Stimulates cells in the ovaries to produce
progesterone, female sex hormones.
 Prolactin stimulates milk production in females
 Stimulates cells in the testes to produce testosterone,
a male sex hormone.
Intermediate Lobe:
 This lobe secretes melanocyte-stimulating hormone
(MSH)
 Controls the darkening of the skin by stimulating pigment
cells in the skin
Posterior Lobe:
 Secretes two hormones:
o Antidiuretic hormone (ADH):
 Principal function is to regulate the balance of water
in the body.
 Stimulates the kidneys to return water to the blood
o Oxytocin:
 Stimulates the smooth muscles in the uterus of a
pregnant female, causing contractions during the
birth of a baby.
Thyroid Gland:
 One of the largest glands of the endocrine system.
 Located in front of the neck, just below the larynx.
 Produces hormones that regulate metabolism, body heat,
and bone growth.
 Principal hormone produced by the thyroid gland is
Thyroxine.
o Regulates the way cells release energy from nutrients or
use energy to create other substances, such as proteins.
The Parathyroid Glands:
 Smallest glands of the endocrine system
 Regulates the body’s calcium and phosphorus balance.
Pineal Gland
 Secretes Melatonin
o Melatonin regulates sleep cycles and is thought to affect
the onset of puberty.
Thymus
 Regulates development of the immune system
The Adrenal Glands:
 Two glands located on the top of the kidneys.
o Adrenal cortex
o Adrenal medulla
Adrenal Cortex:
 Secretes a hormone that inhibits the amount of sodium
excreted in urine and serves to maintain blood volume and
pressure.
 Secretes hormones that aid metabolism of fats, proteins,
and carbohydrates.
 These hormones also play a role in immunity and the
body’s response to stress.
Adrenal Medulla:
 Highly dependent on the hypothalamus and the autonomic
nervous system
 Secretes the hormones epinephrine (adrenaline)
Pancreas:
 Largest gland in the endocrine system:
 Lies behind the stomach
 Attached to the first part of the small intestine
 Secrete two hormones:
o Glucagons
 Raises blood sugar levels
o Insulin
 Lowers blood sugar levels
Gonads:
 Only gland that is different in the male and female
 Hormones from these glands are responsible for the
development and maintenance of the secondary sex
characteristics.
Problems in the Endocrine System:
Diabetes Mellitus
 Disorder in which the pancreas produces too little or no
insulin, resulting in high blood pressure glucose levels.
o Symptoms include fatigue, weight loss, thirst, and
frequent urination.
Graves Disease
 Disorder in which an overactive and enlarged thyroid
gland produces excessive amounts Thyroxine.
o Hyperthyroidism:
 Symptoms include Nervousness, weight loss,
increased thirst, rapid heartbeat, and intolerance
for heat
o Hypothyroidism:
 Symptoms fatigue, dry skin, weight gain,
constipation, and sensitivity to cold.
Cushing’s Disease
 Results from the overproduction of adrenal hormones.
o Symptoms include: Round face, humped upper
back, thin and easily bruised skin, and fragile bones.
Goiter
 Caused mainly by a lack of iodine in the diet.