WEEK 13: Endocrine System

• Endocrine glands secrete signaling molecules called hormones into a neighboring vascularized compartment for uptake by capillaries and distribution throughout the body, rather than directly into an epithelial duct-like exocrine glands
• Ductless glands: distinct clusters of cells with certain organs of the body

  examples: pituitary gland, thyroid and parathyroid gland, adrenal gland, pineal gland
• endocrine cells are specialized cells that secrete hormones into the bloodstream

  examples: islets of Langerhans in the pancreas, corpus luteum of the ovary, interstitial cells of Leydig in the testis
• the endocrine system and the nervous system interact to modulate and coordinate the metabolic activities of the body
• major endocrine organs - major function is the synthesis, storage, and secretion of hormones
• endocrine components within other solid organs - in the form of clusters of endocrine cells within other tissues

  example: the endocrine components of the pancreas, ovary, testis, and kidney
• diffuse endocrine system - scattered individual hormone cells (small clumps) usually within an extensive epithelium

  examples: gastrointestinal and respiratory tract
• Endocrine glands secrete signaling molecules called hormones into a neighboring vascularized compartment.
• distinct clusters of cells with certain organs of the body

  Ductless glands
• Examples of this gland: islets of Langerhans in the pancreas, corpus luteum of the ovary and the interstitial cells of Leydig in the testis

  Endocrine cells
• TRUE/FALSE: The endocrine system and the nervous system are not affiliated in any way

  FALSE, Because they modulate and coordinate the metabolic activities of the body
• The sole or major function of the organ is the synthesis, storage, and secretion of hormones

  Major Endocrine Organs
• Example: the endocrine components of the pancreas, ovary, testis and kidney, in the form of clusters of endocrine cells within other tissues.

  Endocrine components within other solid organs
• These are scattered individual hormone cells (small clumps) usually within an extensive epithelium

  diffuse endocrine system
• Examples of the diffuse endocrine system?

  gastrointestinal and respiratory tract
• These type of cells are always very close to blood capillaries

  specialized or endocrine cells
• They usually aggregate as endocrine glands where they typically arrange themselves as CORDS of cells


  specialized or endocrine cells
• This pertains to endocrine glands and are components of endocrine system that secrete chemicals directly into the blood stream

  endocrine tissues or organs
• Secretory organs


  Various organs that synthesize substances needed by the body and release it through ducts or directly into the blood stream
• Ectoderm


  Germ layer with the hypothalamus, pituitary gland, pineal gland, andrenal medulla
• Endoderm


  Germ layer with the thyroid gland, parathyroid glands, pancreas, and thymus
• Mesoderm


  Germ layer only with the andrenal cortex
• All secretory glands whether exocrine or endocrine develop from the epithelia
• Hormones


  Frequently hydrophilic molecules such as proteins, glycoproteins, peptides, or modified amino acids
• Hormones


  Receptor proteins on the surface of target cells
• Hydrophobic steroid, thyroid hormones


  Must circulate on transport proteins but can diffuse through the membrane of cells and activate cytoplasmic protein receptor in target cells
• Paracrine


  Localized dispersal in interstitial fluid/short loops of blood vessels and the hormones produced act QUICKLY but only at a SHORT distance
• Juxtacrine


  Signaling molecule that remains on the secreting cell's surface or adjacent extracellular matrix, effects target cells when the cells make contact, and is important in developmental tissue interactions
• Autocrine


  Endocrine secretion where cells may produce molecules that act on themselves or on cells of the same type. Example: IGF
• Sella turcica


  Bony cavity at the base of the skulls where the pituitary gland is sitting
• The pituitary gland is located 1 cm across from the base of the brain beneath the third ventricle
• The weight of the pituitary gland in adults is 0.5 grams
• Pituitary Gland

  Also called Hypophysis
• Pituitary gland


  Develops from the oral ectoderm and developing brain
• Neural Component


  Arises as a bud growing down from the floor of the diencephalon and caudally as a stalk or infundibilum that is still attached to the brain
• Oral component


  Arises as an out pocketing of ectoderm from the roof of the primitive mouth that grows cranially
• Rathke's (hypophyseal) pouch


  Formed by the oral component
• Rathke's pouch


  Its base constricts and separates it from the pharynx
• Pituitary-dependent endocrine glands

  Thyroid gland, andrenal cortex, and gonads
• Pituitary Gland aka Hypophysis

  Divided into anterior and posterior parts which have different embryological origins, functions, and control mechanisms