Endocrine System

Endocrine System
  • Anatomy: The endocrine glands include:
    1. Hypothalamus
    2. Pituitary gland
    3. Pineal gland
    4. Thyroid
    5. Parathyroid
    6. Adrenals
  • Physiology- Responsible for communication within the body using hormones made by the endocrine glands.
Endocrine Glands
  • A gland is a group of cells that produces and secretes chemicals.
  • These glands are ductless*, which means that their secretions (hormones) are released directly into the bloodstream and travel to elsewhere in the body to target organs and cells. Many different hormones move through the bloodstream. Each type of hormone is designed to affect only certain cells.
    • *This is in contrast to our digestive glands, which have ducts for releasing the digestive enzymes.
  • Links the nervous and endocrine systems via the pituitary gland
Pituitary – “The master gland”
  • Most pituitary secretions are controlled by the hypothalamus.
  • It is the size of a grape.
  • It consists of anterior and posterior lobes.
Anterior Lobe
  • Growth hormone (GH)- GH causes growth in almost all tissues in the body that are capable of growing.
  • Thyroid-stimulating hormone (TSH)- TSH stimulates the thyroid gland.
  • Follicle-stimulating hormone (FSH)- FSH promotes development of eggs within the ovaries. In men, FSH is important for sperm production in the testes.
  • Luteinizing hormone (LH)- LH causes ovulation in women and prepares the uterus for pregnancy.
  • Prolactin (PRL)- Prolactin causes the development of breast tissue and the production of milk.
Posterior Lobe
  • Anti-diuretic hormone (ADH)- ADH causes the kidneys to keep more water in the body.
  • Oxytocin- This causes contractions in the uterus of a pregnant woman and also causes the release of milk from the breasts.
Pineal Gland
  • The pineal gland secretes melatonin. Melatonin promotes sleep and is involved in the regulation of circadian rhythms. It is secreted when it’s dark (secretes more in the winter).
  • Regulates calcium levels
Adrenal Gland
  • Located on top of the Kidneys
  • There are two parts of the adrenal gland:
    • Adrenal Cortex
      • Secretes Cortisol and Aldosterone
      • Cortisol is a stress hormone that is measured in many massage studies, often inaccurately.
    • Adrenal Medulla
      • Controls the levels of:
        • Epinephrine – adrenaline
        • Norepinephrine – noradrenaline
          • These increase heart rate, blood glucose, and breathing rate and decrease digestive activities.
Thyroid Gland
  • The thyroid gland helps regulate metabolism (Hormones T3 and T4).
Endocrine Pancreas
  • The islets of Langerhans are the regions of the pancreas that contain hormone-producing cells. The islets of Langerhans produce two important hormones:
    1. Glucagon
      • This hormone stimulates the liver to convert glycogen into glucose, causing the blood glucose to rise.
    2. Insulin
      • Insulin is designed to lower blood sugar levels when they become too high.