Endocrine Glands Overview

Endocrine Glands Overview

• Glands classified as exocrine (with ducts) and endocrine (without ducts).
• Exocrine glands secrete into ducts; examples include sweat, saliva, and digestive enzymes.
• Endocrine glands release hormones directly into the bloodstream, regulating metabolic and physiological activities.

Hormonal Functions

• Hormones play vital roles in metabolism, reproduction, and growth.

Endocrine Organs

• Cranial Cavity:
  • Pituitary gland
  • Pineal gland
• Neck Region:
  • Thyroid gland
  • Parathyroid glands
  • Thymus
• Abdominal Cavity:
  • Pancreas
  • Adrenal (supra-renal) glands
• Gonads:
  • Ovaries
  • Testes

Pituitary Gland (Hypophysis)

• Size of a pea, located at the base of the brain, attached to hypothalamus.
• Comprised of two lobes:
  • Anterior Lobe (Adenohypophysis): Produces hormones such as FSH, LH, ACTH, TSH, GH, and Prolactin.
  • Posterior Lobe (Neurohypophysis): Releases oxytocin (uterine contractions) and ADH (kidney function).

Pineal Gland

• Resembles a pine cone, located at the roof of the third ventricle.
• Produces melatonin, which regulates sleep-wake cycles.

Thyroid Gland

• Located in the neck, has a butterfly shape with two lobes connected by isthmus.
• Produces thyroid hormones (T3 and T4) affecting metabolism and growth.
• Parafollicular C cells produce calcitonin, which lowers blood calcium levels.
• Disorders include goiter (enlargement) and congenital deficiencies causing cretinism.

Parathyroid Glands

• Consist of two pairs located behind the thyroid gland.
• Produce parathyroid hormone (PTH) that increases blood calcium levels.

Thymus Gland

• Located behind the sternum, involved in immune system development.
• Produces thymosin, which stimulates T cell production.

Adrenal Glands

• Located atop kidneys, composed of cortex and medulla.
• Adrenal Medulla: Secretes adrenaline (epinephrine) and norepinephrine, enhancing fight-or-flight response (increases heart rate and blood pressure).
• Adrenal Cortex: Consists of three zones:
  • Zona Glomerulosa: Produces mineralocorticoids (aldosterone) for sodium and water retention.
  • Zona Fasciculata: Produces glucocorticoids (cortisol) to increase blood glucose levels.
  • Zona Reticularis: Produces gonadocorticoids (androgens, estrogens, progesterones).

Pancreas

• Functions as both an exocrine and endocrine organ.
• Endocrine Functions:
  • Alpha cells produce glucagon, raising blood glucose levels.
  • Beta cells produce insulin, lowering blood glucose levels and crucial for carbohydrate metabolism.

Gonads

• Testes: Produce androgens and testosterone, promoting male secondary sex characteristics.
• Ovaries: Produce estrogen (female secondary sex characteristics) and progesterone (maintaining uterine lining for pregnancy).