Lecture Notes: Human Body Systems Overview

Topic I: Respiratory System

Key Terms

• Respiration: Cellular process breaking down glucose with oxygen to release energy (ATP).
• Gas Exchange: Oxygen transfer into blood and carbon dioxide out, occurring in alveoli.

Respiratory Pathway

• Air Passage Route: Nostrils → Nasal Cavity → Pharynx → Larynx → Trachea → Bronchi → Bronchioles → Alveoli

Structure and Function Overview

• Nasal Cavity: Air entry, warms, moistens, and filters air.
• Septum: Divides nasal cavity.
• Cilia: Trap particles and pathogens.
• Mucous Membrane: Moistens air and traps dust.
• Pharynx: Passage for air and food.
• Epiglottis: Prevents food from entering the trachea.
• Larynx (Voice Box): Contains vocal cords, sound production.
• Thyroid Cartilage: Protects vocal cords.
• Trachea: Windpipe, maintains open airway.
• Main Bronchi: Two branches entering each lung.
• Bronchioles: Smaller branches of bronchi.
• Alveoli: Site of gas exchange.
• Pleura: Double membrane around lungs.
• Lungs: Contains bronchi, bronchioles, alveoli.
• Diaphragm: Main breathing muscle.

Breathing Mechanics

• Inhalation: Diaphragm contracts, chest cavity enlarges, air enters lungs.
• Exhalation: Diaphragm relaxes, chest cavity reduces, air exits lungs.

Gas Exchange Process

• Oxygen moves from alveoli to bloodstream.
• Carbon dioxide is exhaled from blood to alveoli.

Hyperventilation

• Excessive breathing reduces CO₂ levels, causing dizziness and tingling.
• Can lead to respiratory alkalosis.

Topic II: Excretory System

What is Excretion?

• Removal of metabolic wastes to maintain homeostasis.

Main Waste Products

• Urea: From protein metabolism.
• Water & Mineral Salts: General waste.
• Bile Pigments: From hemoglobin breakdown.

Urine Formation Pathway

• Kidneys → Ureters → Urinary Bladder → Urethra

Kidney Structure & Function

• Cortex: Outer layer, contains nephrons.
• Medulla: Middle layer, contains pyramids.
• Renal Pyramids: Transport urine into pelvis.
• Renal Pelvis: Collects urine for ureter.

Nephron Anatomy

• Malpighian Corpuscle: Filters blood.
• Bowman’s Capsule: Encloses glomerulus, initial filtration.
• Convoluted Tubules: Reabsorb useful substances, secrete wastes.

Urine Formation Steps

1. Filtration: Blood plasma enters Bowman’s capsule.
2. Reabsorption: Water, glucose, salts reabsorbed in tubules.
3. Secretion: Toxins added to filtrate before urine exits.

Topic III: Cardiovascular System & Hematology

Heart Anatomy

• Endocardium: Inner lining.
• Myocardium: Thick cardiac muscle layer.
• Epicardium: Outer surface layer.
• Pericardium: Protective sac.
• Septum: Divides left and right heart halves.

Heart Chambers & Valves

• Atria: Receive blood (Right from body, Left from lungs).
• Ventricles: Pump blood out (Right to lungs, Left to body).
• Atrioventricular Valves: Tricuspid (right), Bicuspid/Mitral (left).
• Semilunar Valves: Aortic and pulmonary valves.

Circulatory Circuits

• Pulmonary Circuit: Right heart → lungs → left heart.
• Systemic Circuit: Left heart → body → right heart.

Cardiac Cycle

• Systole: Contraction, blood pumped.
• Diastole: Relaxation, chambers refill.

Blood Vessels

• Arteries: Carry blood away from heart.
• Capillaries: Gas/nutrient exchange.
• Veins: Return blood to heart.
• Coronary arteries: Supply heart muscle with oxygen.

Blood Composition

• Plasma: Liquid portion, contains water and proteins.
• RBCs (Erythrocytes): Carry oxygen, biconcave shape.
• WBCs (Leukocytes): Fight infection.
• Platelets (Thrombocytes): Aid in clotting.

Lymphatic System

• Lymph: Fluid filtering through tissues.
• Lymph Nodes: Filter lymph, trap pathogens.
• Tissue Fluid: Bathes cells, part of lymphatic return system.

Blood Groups & Immunity

• ABO System: A, B, AB, O blood types, antigen-antibody compatibility.
• Rh System: Rh+ or Rh–, important in pregnancy and transfusions.
• Immunity: Body’s defense; vaccines stimulate antibody production.

Topic IV: Endocrinology

Endocrine System Overview

• Endocrine Glands: Secrete hormones into blood.
• Hormones: Chemical messengers.
• Hyperfunction: Overproduction.
• Hypofunction: Underproduction.

Pituitary Gland (“Master Gland”)

• TSH: Stimulates thyroid.
• ACTH: Stimulates adrenal cortex.
• Gonadotropins: Regulate ovaries/testes.
• Somatotropin: Growth hormone.
• ADH: Water balance (kidney).
• Oxytocin: Childbirth, milk release.
• Disorders: Gigantism, dwarfism, acromegaly, cachexia.

Pineal Gland

• Melatonin: Controls sleep-wake cycles.

Thyroid & Parathyroids

• Thyroxine: Regulates metabolism.
• Parathormone: Regulates calcium levels.
• Disorders: Goitre, cretinism, hyperthyroidism, hypothyroidism.

Thymus

• Thymosin: T-cell development, active in children.

Pancreas (Heterocrine)

• Insulin: Lowers blood sugar.
• Glucagon: Raises blood sugar.
• Disorder: Diabetes mellitus.

Adrenal Glands

• Adrenaline/Noradrenaline: “Fight or flight” response.

Gonads

• Testes: Produce testosterone, male traits, sperm production.
• Ovaries: Produce estrogen and progesterone, female traits, menstrual cycle.

Study Tips

• Use diagrams to label parts of systems (heart, kidney, alveoli, etc.).
• Practice flowcharts for respiratory, circulatory, and urinary pathways.
• Compare disorders, especially endocrine diseases.
• Quiz yourself on hormone functions and anatomical parts.
• Use mnemonics to remember sequences and functions.