Human Body Systems: Anatomy & Physiology Essentials

Posted on Jul 11, 2025 in Biology

Chapter 17: The Special Senses

Olfaction (Sense of Smell)

  • Receptors: Olfactory receptor cells in the nasal epithelium.
  • Pathway: Odorants → Olfactory nerves → Olfactory bulb → Olfactory tract → Temporal Lobe.
  • Adaptation: Rapid; sensitivity decreases quickly.

Gustation (Sense of Taste)

  • Taste Buds: Located on papillae; contain gustatory receptor cells.
  • Primary Tastes: Sweet, sour, salty, bitter, umami.
  • Pathway: Taste buds → Cranial Nerves VII, IX, X → Medulla → Thalamus → Gustatory Cortex.

Vision

  • Eyeball Structure: Fibrous tunic (sclera, cornea), vascular tunic (choroid, ciliary body, iris), retina (photoreceptors).
  • Photoreceptors: Rods (dim light) and cones (color vision).
  • Pathway: Photoreceptors → Bipolar cells → Ganglion cells → Optic Nerve → Thalamus → Visual Cortex.

Audition (Hearing)

  • External Ear: Auricle, auditory canal, tympanic membrane.
  • Middle Ear: Ossicles (malleus, incus, stapes).
  • Inner Ear: Cochlea (hearing), vestibule and semicircular canals (equilibrium).
  • Pathway: Hair cells → Cranial Nerve VIII → Medulla → Thalamus → Auditory Cortex.

Equilibrium (Balance)

  • Static Equilibrium: Utricle and saccule in vestibule; detect head position.
  • Dynamic Equilibrium: Semicircular canals; detect rotational movements.
  • Pathway: Hair cells → Cranial Nerve VIII → Brainstem → Cerebellum.

Chapter 18: The Endocrine System

Hypothalamus

  • Releases hormones that regulate the pituitary gland (Antidiuretic Hormone (ADH), Oxytocin, releasing and inhibiting hormones).

Pituitary Gland

  • Anterior Pituitary: Growth Hormone (GH), Thyroid-Stimulating Hormone (TSH), Adrenocorticotropic Hormone (ACTH), Follicle-Stimulating Hormone (FSH), Luteinizing Hormone (LH), Prolactin.
  • Posterior Pituitary: Antidiuretic Hormone (ADH), Oxytocin.

Thyroid Gland

  • Thyroxine (T4) and Triiodothyronine (T3) regulate metabolism.
  • Calcitonin lowers blood calcium levels.

Parathyroid Glands

  • Parathyroid Hormone (PTH) increases blood calcium levels.

Adrenal Glands

  • Cortex: Cortisol (stress response), Aldosterone (sodium/potassium balance), Androgens (secondary sexual characteristics).
  • Medulla: Epinephrine, Norepinephrine (fight-or-flight response).

Pancreas

  • Insulin (lowers blood sugar), Glucagon (raises blood sugar), Somatostatin (inhibits insulin and glucagon).

Gonads

  • Ovaries: Estrogen, Progesterone, Relaxin.
  • Testes: Testosterone, Inhibin.

Other Key Hormones

  • Erythropoietin (red blood cell production), Leptin (appetite control), Melatonin (sleep regulation).

Chapter 19: The Cardiovascular System: Blood

Blood Composition

  • Plasma: Water, proteins, nutrients, hormones, and waste products.
  • Formed Elements: Red Blood Cells (RBCs), White Blood Cells (WBCs), and Platelets.

Hemostasis

  • Vascular Spasm: Constriction of blood vessels.
  • Platelet Plug Formation: Platelets adhere to the injury site.
  • Coagulation: Clotting cascade involving fibrinogen conversion to fibrin.

Blood Types

  • Blood Groups: A, B, AB, O; Rh factor determines positive or negative.

Chapter 20: The Cardiovascular System: The Heart

Heart Structure

  • Layers: Epicardium, Myocardium, Endocardium.
  • Heart Chambers: Right and Left Atria, Right and Left Ventricles.
  • Valves: Tricuspid, Pulmonary, Mitral, Aortic.

Cardiac Cycle

  • Systole: Contraction of the ventricles.
  • Diastole: Relaxation of the ventricles.
  • Heartbeat Regulation: SA Node → AV Node → Bundle of His → Purkinje Fibers.

Cardiac Output

  • Cardiac Output (CO) = Stroke Volume × Heart Rate.

Chapter 21: The Cardiovascular System: Blood Vessels & Hemodynamics

Blood Vessels

  • Arteries: Carry blood away from the heart; possess thicker walls.
  • Veins: Carry blood toward the heart; possess thinner walls and valves to prevent backflow.
  • Capillaries: The primary site of exchange between blood and tissues.

Hemodynamics

  • Blood Pressure (BP): The force exerted by blood on vessel walls.
  • Resistance: Opposition to blood flow.
  • Flow = Pressure ÷ Resistance.

Chapter 22: The Lymphatic System and Immunity

The Lymphatic System

  • Lymph vessels, lymph nodes, spleen, tonsils, and thymus.
  • Functions: Fluid balance, immunity, and absorption of dietary fats.

The Immune System

  • Innate Immunity: The body’s first line of defense (skin, phagocytes, inflammation).
  • Adaptive Immunity: T-cells (cell-mediated immunity), B-cells (antibody-mediated immunity).

Chapter 23: The Respiratory System

Respiratory Anatomy

  • Upper Respiratory Tract: Nasal cavity, pharynx, and larynx.
  • Lower Respiratory Tract: Trachea, bronchi, bronchioles, and alveoli.
  • Lungs: The primary site of gas exchange.

Mechanics of Breathing

  • Inhalation: Diaphragm contracts, thoracic volume increases, and pressure decreases.
  • Exhalation: Diaphragm relaxes, thoracic volume decreases, and pressure increases.

Gas Exchange

  • External Respiration: Exchange of Oxygen (O2) and Carbon Dioxide (CO2) between alveoli and blood.
  • Internal Respiration: Exchange between blood and body tissues.

Chapter 24: The Digestive System

Digestive Tract Anatomy

  • Mouth: Site of mechanical and chemical digestion (saliva).
  • Esophagus: Transports food to the stomach.
  • Stomach: Secretes acid and enzymes for digestion.
  • Small Intestine: Primary site of nutrient absorption.
  • Large Intestine: Water absorption and waste formation.

Accessory Organs of Digestion

  • Liver: Produces bile and metabolizes nutrients.
  • Pancreas: Secretes digestive enzymes and bicarbonate.
  • Gallbladder: Stores bile.

Chapter 25: Metabolism and Nutrition

Metabolism

  • Catabolism: The breakdown of molecules to release energy.
  • Anabolism: The synthesis of molecules from smaller units.

Essential Nutrients

  • Carbohydrates: Primary energy source.
  • Proteins: Essential building blocks of tissues.
  • Lipids: Energy storage and membrane structure.
  • Vitamins and Minerals: Essential for enzyme function and metabolic pathways.

Chapter 26: The Urinary System

Kidneys

  • Structure: Cortex, Medulla, and Nephron.
  • Functions: Filtration of blood, regulation of fluid and electrolytes, and acid-base balance.

Urine Formation

  • Glomerular Filtration: Movement of substances from blood to the nephron.
  • Tubular Reabsorption: Movement of substances from the nephron to blood.
  • Tubular Secretion: Movement of substances from blood to the nephron for excretion.

Fluid and Electrolyte Balance

  • Antidiuretic Hormone (ADH): Regulates water balance by increasing water reabsorption.
  • Aldosterone: Regulates sodium and potassium balance.

Chapter 27: Fluid, Electrolyte, and Acid-Base Homeostasis

Fluid Balance

  • Intracellular Fluid (ICF): Fluid found inside cells.
  • Extracellular Fluid (ECF): Fluid found outside cells, including interstitial fluid and plasma.

Key Electrolytes

  • Sodium (Na+): The major extracellular cation.
  • Potassium (K+): The major intracellular cation.
  • Calcium (Ca2+): Important for bone health and muscle contraction.

Acid-Base Balance

  • Buffer Systems: The Bicarbonate Buffer System regulates pH in blood.
  • Respiratory and Renal Compensation: Mechanisms that regulate pH by adjusting CO2 or bicarbonate levels.

Chapter 28: The Reproductive Systems

Male Reproductive System

  • Testes: Produce sperm and testosterone.
  • Accessory Glands: Seminal vesicles, prostate, and bulbourethral glands.
  • Penis: Facilitates sperm delivery.

Female Reproductive System

  • Ovaries: Produce eggs (oocytes), estrogen, and progesterone.
  • Uterus: The primary site of fetal development.
  • Menstrual Cycle: Regulated by hormones such as Follicle-Stimulating Hormone (FSH), Luteinizing Hormone (LH), Estrogen, and Progesterone.

Pregnancy and Birth

  • Gestation: The process of fetal development.
  • Labor: Uterine contractions and cervical dilation during birth.