ENDOCRINE SYSTEM
TYPES OF GLANDS
EndocrineExocrine
Endocrine glands; Endocrine tissue
Pineal gland Pituitary gland Thyroid gland Parathyroid glands Thymus Adrenal gland Pancreas Ovaries / Testes
Stomach Duodenum Kidney
Chemistry of Hormones Amines - simple hormones synthesized
from tyrosine Proteins and Peptides - chains of
amino acids hooked together Steroids - lipid soluble hormones
derived from cholesterol Eicosanoids - hormones derived from
arachidonic acid (from lipids)
Mechanisms of Hormone Action
Alters plasma membran permeability
Stimulates synthesis of protein Activates or deactivates enzymes Induces secretory activity Stimulates mitosis
Lipid Soluble Hormones Thyroid and steroid hormones cross the
cell membrane and bind to INTRACELLULAR receptors in the cytoplasm or nucleus
The hormone- receptor complex triggers activation or inactivation of specific genes
Synthesis of new protein alters cellular activity causing a physiological response
Water Soluble Hormones Protein and catecholamine hormones act
by binding to receptors located on the cell membranes of target cells
Hormones act as the 1st messenger which in turn activates a series of events involving cAMP as the 2nd messenger
cAMP activates protein kinases G-proteins link the first messenger and
the second messenger
Hormone Release Humoral - hormones released in
response to changing blood levels
Neural - nerve fibers stimulate release
Hormonal - one hormone stimulates the release of another
Endocrine Glands
Pituitary Gland Master gland Located within the sella turcica of the
sphenoid bone Associated closely with the hypothalamus Differentiated into the anterior pituitary,
or glandular portion, the posterior pituitary, or nervous portion and the avascular pars intermedia located in between
Posterior lobe - Neurohypophysis
Connected with the hypothalamus via the supraopticohypophyseal tract
Oxtocin (OT) Antidiuretic hormone (ADH)
diabetes insipidus
Anterior lobe (Adenohypophysis)
Controlled by releasing and inhibiting hormones produced by the hypothalamus
Growth hormone (GH) somatotropin dwarfism, giantism, acromegaly
Thyroid - stimulating hormone (TSH) Adrenocorticotropic hormone (ACTH)
Acromegaly
Anterior lobe of the Pituitary
Follicle - stimulating hormone (FSH)
Luteinizing hormone (LH)
Prolactin (PRL)
Melanocyte - stimulating hormone (MSH)
Thyroid Gland
Located below the larynx, two lobes connected by an isthmus
Hormones synthesized from iodine and tyrosine
Follicle cells manufacture thyroglobin and store it as colloid
Triiodothyronine (T3) / Thyroxine (T4) Goiter, Graves Disease, Cretinism, Myxedema
Calcitonin (CT) - lowers calcium levels
Parathyroid gland Four tiny glands located on
posterior thyroid Parathyroid hormone (PTH) Raises blood calcium
Adrenal Glands Located retroperitoneally and
superior to the kidney Can be subdivided into outer cortex
and inner medulla
Adrenal Medulla Consists of hormone-producing cells
called chromaffin cells Epinephrine / Norepinephrine (NE) Sympathomimetic hormones Released under stress by direct
innervation from the autonomic nervous system
Adrenal Cortex Manufactures steroid hormones called
corticosteroids Divided into three regions: zona
glomerulosa, zona fasciculata, zona reticularis
Zona glomerulosa (outer) - releases mineralocorticoids, principally aldosterone which controls electrolyte balance in the kidneys
Adrenal Cortex Zona fasciculata (middle) - produces
glucocorticoids such as cortisol and cortisone; controlled by ACTH Addison’s Disease, Cushing’s
Disease Zona reticularis (inner) - produces
adrenal sex hormones such as estrogens and androgens virilism, gynecomastia
Cushings Disease
Thymus Pineal Gland Located
posterior to the sternum and between the lungs
Thymosin
Located in the roof of the 3rd ventricle of the brain
Melatonin
Pancreas Located posterior and inferior to the
stomach Both exocrine and endocrine Islets of Langerhans
Alpha cells - glucagon Beta cells - insulin Delta cells - somatostatin
Diabetes mellitus - Type I, TypeII
Ovaries Located in the pelvic cavity Estrogens
Estradiol, estriol, estrone Progesterone Inhibin Relaxin
Testes Located in the scrotum Testosterone Inhibin
