Endocrine System There are three general classes of hormones Lipid soluble derivatives – steriods- derived from cholesterol and are synthesized in the smooth ER • sex hormones- estrogen, progesterone, testosterone – eicosanoids- derived from fatty acids • leukotrienes- has mostly local action and is involved in tissue inflammation • prostaglandins-has local action and is involved in inflammation, smooth muscle contraction, blood flow, intensify pain, and promote fever. (Aspirin and ibuprofen [Motrin] inhibit prostaglandin synthesis.) Water soluble derivatives • Amino acid derivatives • Peptide and Proteins Endocrine Glands • The body has two types of glands – Exocrine glands- secrete their products into ducts that carry the secretions into body cavities or on to body surfaces. • Sweat glands (sudoriferous glands) • oily glands (sebaceous glands) • mucous glands • digestive galnds – Endocrine glands- ductless glands that secrete their products (hormones) into the extracellular space around the secretory cells (local action) which then diffuse into the blood vessels (distant action) Endocrine System Endocrine glands of the body that constitute the endocrine system • Pituitary gland • Thyroid • Parathyroid • Adrenal • Pineal Tissues that contain cell that secrete hormones but not considered endocrine glands exclusively – Hypothalamus – Thymus – Pancreas – Ovaries – Testes – kidneys – Stomach – Liver – Small intestine
– Skin – Heart – Adipose tissue – placenta Circulating and Local Hormones Circulating hormones-hormones that pass into the blood stream and act on distant target cells. • Linger in the blood and exert their effects for a few minutes or a few hours – Are inactivated by the liver and excreted by the kidney Local hormones-those that act locally without first entering the bloodstream. – Paracrines- hormones that act on neighboring cells – Autocrines- those that act on the same cell that secreted them. • Are usually inactivated quickly • Ex: nitric oxide (NO)- released by endothelial cell which causes relaxation of nearby vascular smooth muscle, in turn causing vasodilation and increased blood flow Chemical Classes of Hormones Water –soluble Hormones • Monoamine (biogenic amines) hormones- synthesized by modifying certain amino acids – Catecholamines- (made from tyrosine) epinephrine, norepinephrine, and dopamine – Histamine- from histadine by mast cells and platelets – Serotonin and melatonin- from tryptophan • Peptide and protein hormones- synthesized on the rough ER and consist of chains 3-200 amino acids – Ex: Thyroid-stimulating hormone (TSH) Chemical Classes of Hormones Eicosanoid hormones- chemical mediators derived from arachidonic acid (a 20-carbon fatty acid) located in the phospholipids in the plasma membrane • leukotrienes- mediates allergic reactions – derived from the enzyme lipoxygenase action on arachidonic acid cyclooxygenase converts arachidonic acid to three other types of eicosanoids
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