The Respiratory System

Major Functions of the Respiratory System

• Primary Function: To supply the body with oxygen (O2) and remove carbon dioxide (CO2).

• Additional Functions: Involved in speech, olfaction (smell), and regulation of blood pH.

Processes of Respiration

• Pulmonary Ventilation: Movement of air into and out of the lungs (breathing).

• External Respiration: Gas exchange between air in alveoli and blood in pulmonary capillaries.

• Transport of Gases: Movement of O2 and CO2 in the blood between lungs and tissues.

• Internal Respiration: Gas exchange between systemic blood and tissue cells.

Upper and Lower Respiratory Organs

• Upper Respiratory Tract: Nose, pharynx, larynx

• Lower Respiratory Tract: Trachea, bronchial tree, lungs

• Bronchial Tree: Series of branching airways including bronchi, bronchioles (contain smooth muscle and cuboidal epithelial cells), and alveoli.

Conducting Zone vs. Respiratory Zone

• Conducting Zone: All respiratory passageways that provide conduits for air to reach gas exchange sites (nose to terminal bronchioles).

• Respiratory Zone: Site of gas exchange (respiratory bronchioles, alveolar ducts, alveoli).

• Alveoli: Thin-walled sacs specialized for gas exchange; surrounded by capillaries; contain type I and II cells.

The Pleurae

• Visceral Pleura: Covers the lungs.

• Parietal Pleura: Lines the thoracic cavity.

• Pleural Cavity: Space between pleurae containing lubricating fluid.

Homeostatic Imbalances

• Laryngitis: Inflammation of the larynx.

• Rhinitis: Inflammation of the nasal mucosa.

• Pleurisy: Inflammation of the pleurae.

Respiratory Physiology

Pulmonary Ventilation

• Inspiration: Diaphragm contracts, thoracic volume increases, pressure decreases, air flows in.

• Expiration: Diaphragm relaxes, thoracic volume decreases, pressure increases, air flows out.

• Gas Law: Boyle's Law () – pressure and volume are inversely related.

Gas Exchange

• Dalton's Law: Total pressure of a gas mixture is the sum of the partial pressures of each gas.

• Henry's Law: The amount of gas dissolved in a liquid is proportional to its partial pressure and solubility.

• External Respiration: Influenced by partial pressure gradients, gas solubility, membrane thickness, and surface area.

• Internal Respiration: Driven by partial pressure gradients between blood and tissues.

Gas Transport

Oxygen Transport

• Transport Mechanisms: 98.5% bound to hemoglobin, 1.5% dissolved in plasma.

• Partial Pressure: High in alveoli and arterial blood; low in tissues and venous blood.

• Types of Hypoxia: Anemic, ischemic, histotoxic, hypoxemic.

• Hemoglobin Affinity: Affected by pH, CO2, temperature, and 2,3-BPG.

Carbon Dioxide Transport

• Transport Mechanisms: 70% as bicarbonate ion (), 23% bound to hemoglobin, 7% dissolved in plasma.

• Partial Pressure: High in tissues and venous blood; low in alveoli and arterial blood.

• Imbalances: Excess CO2 leads to acidosis; too little leads to alkalosis.

Lung Diseases (General Descriptions)

• Obstructive Diseases: Asthma, chronic bronchitis, emphysema (airflow limitation).

• Restrictive Diseases: Pulmonary fibrosis (reduced lung expansion).

Blood

General Functions

• Transport: O2, CO2, nutrients, wastes, hormones.

• Regulation: pH, temperature, fluid volume.

• Protection: Against blood loss (clotting) and infection (immune cells).

Components of Blood

• Plasma: Liquid matrix; 90% water, contains proteins, nutrients, hormones, wastes.

• Formed Elements: Erythrocytes (RBCs), leukocytes (WBCs), platelets (thrombocytes).

Erythrocytes (Red Blood Cells)

• Function: Transport O2 and some CO2.

• Regulation: Controlled by erythropoietin (EPO) in response to hypoxia.

Leukocytes (White Blood Cells)

• Function: Defense against pathogens.

• Types: Neutrophils, lymphocytes, monocytes, eosinophils, basophils.

Platelets

• Function: Essential for blood clotting (hemostasis).

Phases of Hemostasis

• Vascular Spasm: Vasoconstriction to reduce blood loss.

• Platelet Plug Formation: Platelets adhere and aggregate at injury site.

• Coagulation: Fibrin mesh forms, stabilizing the clot.

Blood Grouping (Types)

• Agglutinogens: Antigens on RBC surface (A, B, Rh).

• Agglutinins: Antibodies in plasma against A or B antigens.

• Blood Types: A, B, AB, O (based on presence/absence of A/B agglutinogens).

• Rh Factor: Presence (+) or absence (–) of D antigen; Rh– individuals can develop anti-Rh antibodies after exposure.

• Transfusions: Incompatible transfusions cause agglutination and hemolysis.

• Pregnancy: Rh– mother with Rh+ fetus can develop hemolytic disease of the newborn.

The Heart

Pulmonary and Systemic Circuits

• Pulmonary Circuit: Right side of heart pumps blood to lungs for gas exchange.

• Systemic Circuit: Left side pumps oxygenated blood to body tissues.

General Structure of the Heart

• Coverings: Pericardium (fibrous and serous layers).

• Chambers: 2 atria (receiving), 2 ventricles (pumping).

• Valves: Atrioventricular (tricuspid, bicuspid/mitral), semilunar (pulmonary, aortic).

Pathway of Blood Through the Heart

1. Right atrium → tricuspid valve → right ventricle → pulmonary valve → pulmonary trunk → lungs

2. Lungs → pulmonary veins → left atrium → mitral valve → left ventricle → aortic valve → aorta → body

Cardiac Muscle Fibers

• Characteristics: Striated, branched, intercalated discs, involuntary.

• Nutrition/Gas Supply: Coronary arteries supply O2 and nutrients.

Electrical Events of the Heart

• Sequence of Excitation: SA node → AV node → AV bundle (bundle of His) → bundle branches → Purkinje fibers.

• Electrocardiogram (ECG): P wave (atrial depolarization), QRS complex (ventricular depolarization), T wave (ventricular repolarization).

Mechanical Events of the Heart

• Cardiac Cycle Phases: Atrial systole, ventricular systole, diastole.

• Heart Rate Regulation: Autonomic nervous system, hormones, ions, fitness, age.

Homeostatic Imbalances

• Myocardial Infarction: Heart attack due to blocked coronary artery.

• Fibrillation: Rapid, irregular heart contractions.

Blood Vessels

Tunics of Blood Vessels

• Tunica Intima: Endothelial lining.

• Tunica Media: Smooth muscle and elastic fibers.

• Tunica Externa: Connective tissue.

Types of Blood Vessels

• Arteries: Carry blood away from heart; thick walls.

• Capillaries: Exchange vessels; thin walls for diffusion.

• Veins: Carry blood toward heart; thinner walls, valves present.

Types of Arteries

• Elastic Arteries: Largest, near heart, withstand pressure fluctuations.

• Muscular Arteries: Distribute blood to organs, more smooth muscle.

• Arterioles: Smallest, control flow into capillary beds.

Types of Capillaries

• Continuous: Most common, uninterrupted lining.

• Fenestrated: Pores for increased permeability (kidneys, intestines).

• Sinusoidal: Large gaps, allow passage of large molecules (liver, spleen).

Capillary Exchange and Pressures

• Mechanisms: Diffusion, filtration, osmosis, transcytosis.

• Pressures: Hydrostatic and osmotic pressures regulate movement.

General Characteristics of Veins

• Thinner walls, larger lumens, contain valves to prevent backflow.

Pulse and Blood Pressure

• Pulse: Rhythmic expansion of artery due to heartbeat.

• Blood Pressure: Force of blood against vessel walls; measured as systolic/diastolic (e.g., 120/80 mmHg).

• Influencing Factors: Cardiac output, blood volume, resistance, vessel elasticity.

Additional info: Where details were not explicit in the original file, standard academic context was added for completeness (e.g., types of hypoxia, details of capillary exchange, and the cardiac cycle phases).