AMA 176 - Anatomy

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AMA 176 - Anatomy Physiology/Medical
Terminology/Pathology 7 Endocrine System
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Endocrine System

• Function an information signaling system (like
  nervous system) that uses blood vessels as
  information channels (rather than nerves). Glands
  located all over the body release chemical
  messengers called hormones which regulate
  specific bodily functions e.g. growth, puberty,
  metabolism, reproduction, etc. Help to maintain
  homeostasis or balance in the body.
• Hormones work by binding to sites on various
  tissues that recognize them causing the intended
  biological effect, somewhat like a lock and key.
  Each receptor is the lock and the specific
  hormone that is attracted to that receptor is the
  key that opens that lock and causes the intended
  biological effect. (e.g. the pituitary gland
  secretes growth hormone that opens the lock in
  bones and tissues and causes growth).

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Structure of the Endocrine System

• Two types of glands
• Endocrine secrete hormones into the bloodstream.
  (examples pineal, thymus, thyroid, parathyroid,
  adrenal, pancreas, pituitary, ovaries, testes)
• Exocrine send chemical substances (tears, sweat,
  saliva) via ducts to the outside of the body.
  (examples sweat, mammary, mucous, salivary,
  lacrimal (tear) glands)

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Pineal Thymus

• Pineal located in the brain. Secretes melatonin
  to regulate the bodys biological clock.
• Thymus located behind the sternum. Produces
  thymosin and T-cells and is responsible for
  immune responses (more so in childhood, shrinks
  as we age).

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Thyroid

• Located in the neck.
• Secretes thyroxine (tetraiodothyronine) (T4) and
  triiodothyronine (T3).
• These are hormones synthesized from iodine from
  the bloodstream necessary to maintain metabolism
  by helping cells take in oxygen.

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Parathyroid

• Located on either side of the thyroid in the neck
  (four small oval bodies).
• Parathyroid hormone (PTH) takes calcium from
  bones and puts it into the bloodstream to help
  with proper functioning of body tissues,
  especially the muscles.

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Adrenal

• Two small glands on top of each kidney. Composed
  of two parts an inner (medulla) and outer
  (cortex) portion.
• Cortex secretes corticosteroids (complex
  chemicals made from cholesterol)
• Cortisol to regulate glucose, fat and protein
  metabolism
• Aldosterone to regulate electrolytes or salts
• Androgens and Estrogens to regulate male and
  female sex characteristics
• Medulla secretes catecholamines (chemicals made
  from amino acids).
• Epinephrine to increase heart rate and BP, dilate
  bronchial tubes, release glucose and glycogen for
  more energy flight or fight
• Norepinephrine constricts blood vessels to raise
  BP)

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Pancreas

• Located near stomach
• Made of specialized hormone producing cells
  called the islets of Langerhans that produce
  insulin and glucagon which regulate blood sugar
  levels.
• Also secretes digestive enzymes into the
  digestive tract.

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Pituitary

• Also called hypophysis small pea-sized gland
  located in brain.
• The hypothalamus in the brain sends signals to
  cause the pituitary to release or inhibit many
  hormones such as growth, thyroid stimulation,
  pregnancy, etc.
• Basically the pituitary hormones tell other
  glands what to do.

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Ovaries Testes

• Ovaries located in the lower abdomen in females.
  Produce eggs (gamete or ovum) as well as hormones
  responsible for female sex characteristics and
  regulation of the menstrual cycle.
• Testes located in the inguinal region of the
  male, suspended in the scrotum. Produce sperm and
  testosterone responsible for male sex
  characteristics.

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