Human Biology Quiz

Thyroid Gland

• Bilobed gland, shaped like a shield of cartilage
• Produces calcitonin (decreases blood calcium levels), thyroxine (T4), and triiodothyronine (T3)
• T4 and T3 are vital for energy production and growth/development, especially in children
• Regulates metabolic rate of all tissues
• Essential for nervous system development

Parathyroid Glands

• Composed of four small glands (usually two pairs)
• Secrete parathyroid hormone (PTH)
• PTH increases blood calcium levels by stimulating osteoclasts (cells that break down bone) and releasing calcium into the bloodstream.

Adrenal Glands

• Located above the kidneys
• Adrenal medulla (inner part)
  • Secretes epinephrine (adrenaline) and norepinephrine, modified amino acids
  • Released during stress and exercise
  • Causes vasoconstriction (narrowing of blood vessels)
• Adrenal cortex (outer part)
  • Secretes various steroid hormones
    • Mineralocorticoids (e.g., aldosterone)
      • Regulate water and electrolyte balance, primarily sodium, prompting kidneys to retain more sodium and water, which increases blood volume
    • Glucocorticoids (e.g., cortisol)
      • Increase blood glucose levels, critical for brain function
      • Important during stress responses
    • Gonadocorticoids
      • Converted to testosterone and estrogens in peripheral tissues

Pineal Gland

• Secretes melatonin
• Involved in regulating circadian rhythms

Pancreas

• Has both endocrine and exocrine functions
• Endocrine portion contains clusters of cells (Islets of Langerhans)
  • Alpha cells secrete glucagon
    • Increases blood sugar levels
  • Beta cells secrete insulin
    • Decreases blood sugar levels
    • Promotes glycogen formation (glycogenesis)
    • Breaks down glycogen to release glucose (glycogenolysis)

Thymus

• Secretes thymic hormones (e.g., thymosin, thymopoietin)
• Crucial in immune system development

Gonads

• Testes (male) produce sperm but mature elsewhere
• Ovaries (female) produce eggs -Secrete estrogen (feminizing hormone) -Secrete progesterone(preparation for pregnancy)

Blood Anatomy

• Plasma: Fluid matrix (90% water) containing nutrients, wastes, proteins (e.g., albumin, fibrinogens, globulins), and hormones
• Formed Elements
  • Erythrocytes (RBCs): Biconcave discs, contain hemoglobin, essential for oxygen transport
  • Leukocytes (WBCs): Include granulocytes (neutrophils, eosinophils, basophils)—involved in inflammatory responses and phagocytosis, and agranulocytes (lymphocytes, monocytes)—part of the immune system; monocytes become macrophages in tissues
  • Platelets: Cell fragments involved in blood clotting

Additional Information

• Monocytes: Phagocytic cells that transform into macrophages in tissues. They are part of the immune system
• T cells and B cells: Types of lymphocytes involved in different aspects of acquired immunity; T cells attack foreign cells and B cells secrete antibodies
• WBCs (white blood cells): various types with different functions in the immune system and inflammatory responses.