ENDOCRINE ORGANS

Thyroid Gland

• Microscopy of Thyroid

  • Observations on high power microscopy show open circular areas, known as follicles.

  • Follicles serve as storage areas for thyroid hormones.

    • They store hormones extracellularly.

• Follicular Cells

  • Line the follicles; also called T thyrocytes.

  • Produce thyroglobulin, which is the main hormone stored in the follicle.

  • Follicular cells are characterized by nuclei visible as small purple dots along the follicle's border.

• Colloid

  • The pink-stained fluid material within the follicle that contains thyroglobulin and iodine.

• Parafollicular Cells

  • Unattached to the follicles and called C thyrocytes.

  • Responsible for secreting calcitonin, a hormone involved in calcium regulation.

Adrenal Gland

• Anatomy and Structure

  • Composed of two main regions: cortex (superficial) and medulla (deep).

  • Cortex regulated by anterior pituitary hormones, while the medulla is directly regulated by the hypothalamus.

• Capsule Layer

  • Connective tissue layer encasing the adrenal gland, indicating the superficial portion.

• Cortex Layers and Functions

  • Zona Glomerulosa

    • Superficial layer, darker purple.

    • Secretes mineralocorticoids for water balance.

  • Zona Fasciculata

    • Middle layer, lighter purple.

    • Secretes glucocorticoids such as cortisol and cortisone.

  • Zona Reticularis

    • Deepest layer near the medulla, pinkish color, secretes androgens.

• Medulla Characteristics

  • Contains blood and lymphatic vessels.

  • Secretes epinephrine and norepinephrine, activating the fight or flight response.

Pancreas

• Dual Function

  • Primarily exocrine (99% of pancreatic function) and secretes digestive enzymes into the small intestine.

• Microscopic Structure

  • Dark purple acinar cells dominate the tissue, representing exocrine function.

• Pancreatic Islets

  • Lighter stained clusters representing endocrine function.

  • Composed of four cell types:

    • Alpha Cells: Secrete glucagon (increases blood glucose levels).

    • Beta Cells: Secrete insulin (decreases blood glucose levels).

    • Delta Cells: Secrete somatostatin (inhibits hormone release).

    • F Cells: Secrete pancreatic polypeptide (regulates pancreatic secretions).