Endocrine System

• Endocrine System: Help control mood, growth and development, and the way our organs work, metabolism, and reproduction.
• Endocrine Gland: A group of secretory cells that release their products, chemical signals called hormones, usually into circulation. The secretion never pass through ducts.
• Endocrine glands include the pituitary gland, thyroid gland, parathyroid glands, adrenal glands, and pineal glands.
• Endocrine organs include hypothalamus, thymus, pancreas, liver, small intestine, skin, heart, adipose tissue, and placenta also have endocrine function.
• The pituitary gland is also known as the hypophysis.
• The pituitary gland is located in the hypophyseal fossa of the sphenoid bone.
• The pituitary gland is considered as the 'Maestro Gland' because it releases various hormones that control all the major endocrine glands of the body.
• The pituitary gland is formed of two anatomical and functional parts:

  • The Adenohypophysis (Anterior pituitary)
  • The Neurohypophysis (Posterior pituitary)
• The hypothalamus is part of the diencephalon of the brain.
• The hypothalamus is located inferior to the thalamus.
• The hypothalamus is a major link between the nervous and the endocrine systems.
• The hypothalamus is connected to the pituitary gland by blood vessels and nerve fibers.
• The hypothalamus secrets a number of hormones that control the secretions of the pituitary gland.
• Anterior pituitary is made up of pars tuberalis, pars, intermedia, and pars distalis.
• Posterior pituitary is made up of infundibular stalk and pars nervosa.
• The blood supply of the pituitary glands comes off the internal carotid artery.
• Two groups of vessels that supply blood to the pituitary gland:

  1. Inferior Hypophyseal Arteries
  2. Superior Hypophyseal Arteries
• The inferior hypophyseal arteries provide blood mainly for the neurohypophysis.
• The superior hypophyseal arteries provide blood mainly for adenohypophysis.
• Hormone-rich venous blood leaves the pituitary gland by the anterior and posterior hypophyseal veins.
• Anterior pituitary has three types of cells: acidophils, basophils, and chromophobes (unstained cells)
• The synthesis and release of hormones of the anterior pituitary are controlled by releasing and inhibiting hormones from the hypothalamus.
• The synthesis and release of hormones of the anterior pituitary are controlled by feedback regulation.
• Hypothalamic hormones made by neurosecretory cells transported by axons to the hypophyseal portal system.
• Anterior pituitary hormones act on other endocrine glands.
• Growth Hormone (GH): One of the hormones secreted by the anterior pituitary that targets several area.
• Thyroid Stimulating Hormone (TSH): One of the hormones secreted by the anterior pituitary that targets the thyroid gland.
• Adrenocorticotropic Hormone: One of the hormones secreted by the anterior pituitary that targets the adrenal cortex.
• Follicle Stimulating Hormone (FSH): One of the hormones secreted by the anterior pituitary that targets the ovaries.
• Leutinizing Hormone (LH): One of the hormones secreted by the anterior pituitary that targets the testes.
• Prolactin: One of the hormones secreted by the anterior pituitary that targets the breast.
• Posterior pituitary does not synthesize hormones. It only releases oxytocin and antidiuretic hormone (ADH) when needed.
• Antidiuretic Hormone (ADH) = Vasopressin
• Posterior pituitary contains nerve endings and astrocyte-like cells called Pituicytes.
• Hormones in the posterior pituitary are transported through axons in the hypothalamus-hypophysial tract to the nerve endings.
• The thyroid gland is a butterfly-shaped gland.
• The thyroid gland is located inferior to larynx.
• Lobes of the Thyroid Gland: Left and right.
• The lobes of the thyroid gland extend from the thyroid cartilage to the level of the 5th tracheal cartilage.
• The thyroid gland is related to the common carotid artery and internal jugular veins.