Definition Mechanism of respiration is the process by which air moves into (inspiration) and out of (expiration) the lungs due to pressure changes created by changes in the volume of the thoracic cavity. Phases of Respiration 1. Inspiration (Inhalation) Definition: Entry of air into the lungs. Mechanism Diaphragm contracts → becomes flat. External intercostal muscles contract. Ribs move upward and outward. Sternum moves forward. Thoracic cavity volume increases. Lungs expand due to pleural attachment. Intrapulmonary pressure decreases (about −1 to −2 mmHg below atmospheric pressure). Air enters the lungs until pressures become equal. Muscles of Forced Inspiration Sternocleidomastoid Scalenes Pectoralis minor Serratus anterior 2. Expiration (Exhalation) Definition: Exit of air from the lungs. Mechanism Diaphragm relaxes → dome-shaped. External intercostal muscles relax. Elastic recoil of lungs occurs. Ribs move downward and inward. Thoracic cavity volume decreases. Intrapulmonary pressure increases (about +1 to +2 mmHg). Air is expelled from the lungs. Muscles of Forced Expiration Internal intercostal muscles Abdominal muscles Rectus abdominis External oblique Internal oblique Transversus abdominis Types of Breathing Quiet breathing – Normal breathing at rest. Forced breathing – During exercise or respiratory distress. Factors Affecting Respiration Diaphragm movement Intercostal muscle activity Elasticity of lungs Airway resistance Lung compliance Surfactant Flow Chart Inspiration Diaphragm contracts ↓ Thoracic cavity expands ↓ Intrapulmonary pressure ↓ ↓ Air enters lungs Expiration Diaphragm relaxes ↓ Thoracic cavity volume decreases ↓ Intrapulmonary pressure ↑ ↓ Air leaves lungs Difference Between Inspiration and Expiration Inspiration Expiration Active process Passive (normal) Diaphragm contracts Diaphragm relaxes Ribs move upward & outward Ribs move downward & inward Thoracic volume increases Thoracic volume decreases Pressure decreases Pressure increases Air enters lungs Air leaves lungs Clinical Importance Seen in asthma, COPD, emphysema, and pneumothorax. Diaphragmatic paralysis causes difficulty in breathing. Spirometry is used to assess respiratory function handwritten page ganrate kro
Handwritten medical notes page on "Mechanism of Respiration" in a student notebook style with ruled lines. The page should look like neat handwritten biology notes with a blue pen on white lined paper. Include all of the following content clearly written: Title: MECHANISM OF RESPIRATION (underlined, large) DEFINITION: Process by which air moves into (inspiration) and out of (expiration) the lungs due to pressure changes caused by changes in thoracic cavity volume. PHASES OF RESPIRATION 1. INSPIRATION (Inhalation) — Entry of air into lungs Mechanism: • Diaphragm contracts → becomes flat • External intercostal muscles contract • Ribs move upward & outward; sternum moves forward • Thoracic cavity volume increases • Lungs expand (pleural attachment) • Intrapulmonary pressure decreases (−1 to −2 mmHg) • Air enters lungs until pressures equalize Muscles of Forced Inspiration: Sternocleidomastoid, Scalenes, Pectoralis minor, Serratus anterior 2. EXPIRATION (Exhalation) — Exit of air from lungs Mechanism: • Diaphragm relaxes → dome-shaped • External intercostal muscles relax • Elastic recoil of lungs • Ribs move downward & inward • Thoracic volume decreases • Intrapulmonary pressure increases (+1 to +2 mmHg) • Air expelled from lungs Muscles of Forced Expiration: Internal intercostal muscles, Rectus abdominis, External oblique, Internal oblique, Transversus abdominis FLOW CHART (drawn with arrows): Inspiration: Diaphragm contracts → Thoracic cavity expands → Intrapulmonary pressure ↓ → Air enters lungs Expiration: Diaphragm relaxes → Thoracic volume decreases → Intrapulmonary pressure ↑ → Air leaves lungs COMPARISON TABLE (Inspiration vs Expiration): Active process | Passive process Diaphragm contracts | Diaphragm relaxes Ribs up & out | Ribs down & in Volume increases | Volume decreases Pressure decreases | Pressure increases Air enters | Air leaves CLINICAL IMPORTANCE: • Seen in asthma, COPD, emphysema, pneumothorax • Diaphragmatic paralysis → breathing difficulty • Spirometry assesses respiratory function