E

A&P2 — Endocrine System, 1/28/25.

Pineal Gland

  • Location: Located in the posterior portion of the brain.

  • Function: Known as the "third eye" due to its light sensitivity.

    • Receives information from retinal nerves to detect light exposure.

    • Produces melatonin from specialized cells known as pinealocytes.

  • Regulation of Melatonin Production:

    • Light Exposure: More melatonin is secreted in darkness.

    • Timing: The pineal gland functions best on a set schedule, thus adapting to regular sleep patterns.

      • Consistency in sleep schedules can improve overall sleep quality.

  • Calcification: The pineal gland accumulates calcifications over time (referred to as brain sand), which show as white spots on X-rays and assist in orientating surrounding brain structures.

Gonads (Testes and Ovaries)

  • Testes:

    • Main hormone produced: Testosterone.

    • Involved in growth and development beyond the reproductive system, influencing skeletal and muscular growth.

  • Ovaries:

    • Main hormones produced: Estrogen and Progesterone.

    • Play a critical role in the reproductive system and overall growth and development.

Thymus Gland

  • Location: Superior to the heart and bilobed (two connected sections).

  • Function:

    • Shrinks with age due to apoptosis (programmed cell death).

    • Produces T cell-related hormones that are essential for the immune system, particularly T lymphocyte differentiation.

Novel Endocrine Contributors

  • Smaller tissues that produce hormones functioning locally within the body:

Heart

  • Hormone: Atrial Natriuretic Peptide (ANP)

    • Function: Lowers blood pressure by targeting the kidneys and adrenal glands.

Gastrointestinal Tract

  • Hormone: Gastrin

    • Function: Initiates digestion in response to food by stimulating digestive tissues to produce enzymes and acids.

Kidneys

  • Hormone: Erythropoietin (EPO)

    • Function: Stimulates red blood cell production in response to low oxygen levels in tissues.

  • Another hormone: Renin

    • Function: Plays a role in regulating blood pressure.

Skin

  • Hormone: Cholecalciferol

    • Function: Serves as a precursor to activated vitamin D, essential for various bodily functions. Activated by sunlight exposure.

Placenta

  • Function: Acts as a temporary endocrine organ during pregnancy, producing hormones including Human Chorionic Gonadotropin (HCG).

    • HCG is associated with pregnancy tests; elevated levels indicate pregnancy.

Adipose Tissue

  • Hormone: Leptin

    • Function: Suppresses appetite; levels of leptin correlate with adipose tissue mass, but it is often overridden by the brain's hunger signals.