Endocrine System

Created by: Alyssa Jonet

What does it do?

The Endocrine System is composed of specialized glands and cells that secrete chemicals, known as hormones, directly into the blood. It provides long lasting control by hormone secretion. Hormones are also the main regulators of metabolism, reproduction, and other body activities. They play important roles in fluid balance, acid-base balance, and energy metabolism.

SPECIAL GLANDS

Pituitary Gland

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  • No larger than a pea.
  • Located deep in the cranial cavity, in the small depression of the sphenoid bone. The stalk-like structure of the gland attaches to the undersurface of the brain (hypothalamus).
  • Two kinds - Adenohypophysis and neurohypophysis
  • Adenohypophysis (Anterior Pituitary)- Structure of an Endocrine gland. Acts as the adrenal cortex. Increase amount of cortisol. Exerts control over the structure and function of the thyroid gland, adrenal cortex, the ovarian follicles, and the corpus luteum.
  • Neurohypophysis (Posterior Pituitary) - Structure of a nervous tissue. Releases two hormones-antidiuretic hormone and oxytocin.

Pineal Gland

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  • Small gland near the roof of the third ventricle of the brain.
  • Named "pineal" because it resembles the pine nut.
  • Becomes encrusted as a person ages
  • Produces melatonin
  • Melatonin inhibits the tropic hormones that affect the ovaries. Regulates the onset of puberty and the menstrual cycle in women.

Hypothalamus

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  • It plays an important role in the regulation of many body functions related to homeostasis such as: The regulation of body temperature, appetite, and thirst.
  • Production of ADH and oxytocin occurs in the Hypothalamus
  • Also produces substances called releasing hormones and inhibiting hormones.

Thyroid Gland

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  • Lies in the neck just below the larynx.
  • Secretes two thyroid hormones: Thyroxine and triiodothyronine
  • Also secretes the hormone calcitonin
  • Stores considerable amounts of the thyroid hormones in the form of a colloid compound.
  • Thyroid hormones stimulate cellular metabolism

Parathyroid

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  • Usually four glands found on the back of the thyroid gland.
  • Secrete parathyroid hormone (PTH)
  • PTH increases the concentration of calcium in the blood.

Thymus

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  • Located in the mediastinum, and in infants it may extend up into the neck as far as the lower edge of the thyroid gland
  • Plays a critical part in the body's defenses against infections
  • The hormone thymosin is a group of hormones that work together in the development and function of the body's immune system.

Adrenal

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  • Curves over the top of each kidney.
  • Two separate endocrine glands: Adrenal cortex and Adrenal medulla
  1. Hormones secreted by 3 layers in the adrenal cortex are called corticoids.
  2. The outer layer secretes hormones called mineralocorticoids
  3. The main hormone is aldesterone
  4. The middle zone secretes glucocorticoids
  5. Deepest zone of the cortex secretes sex hormones
  • The adrenal medulla (inner portion of the adrenal gland) secretes the hormones epinephrine and norepinephrine
  • Nephrine is also known as adrenaline

Pancreas

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  • Located behind the stomach, surrounded by small intestines, liver, and spleen
  • Plays the role of converting the food we eat into fuel for the body's cells
  • Exocrine function and endocrine function
  • Exocrine: the pancreas has exocrine glands that produce enzymes important to digestion
  • Endocrine: Islet cells that create and release hormones directly into the bloodstream
  • Hormones produced: Insulin and glucagon (which acts to lower and raise blood sugar levels)

Ovaries and Testes

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  • Ovaries: (female sex glands) two different glandular structures
  • Ovarian follicles: little pockets where the eggs develop
  • secrete estrogen (feminizing hormone)
  • Corpus luteum: secretes progesterone but also some estrogen
  • Testes: (male sex gland) Some cells in the testes produce male sex cells called sperm. Others in the testes, reproductive ducts, and glands produce the reproductive fluid called semen.
  • The cells in the testes secrete the male sex hormone called testosterone (Masculinizing hormone) directly into the blood

Diseases/Disorders