W34N Respiratory System

Five Main Functions of the Respiratory System

• Gas exchange (O2 and CO2) is a primary function; inability to perform this leads to blood pH change, resulting in respiratory acidosis
• pH regulation is achieved through CO2 accumulation; lower pH, and the enzyme requires pH 7.4 for proper function, becoming dysfunctional in an acidic environment
• Defence against pulmonary pathogens is a key role; stage 2 involves asthma, COPD, and cystic fibrosis, while stage 4 involves advanced lung cancer
• Vocalisation occurs as air passes through the larynx
• Facilitating the sense of smell occurs through sniffing

Metabolism and Respiration

• Metabolism consumes O2 and produces CO2, requiring oxygen for aerobic respiration
• The body requires a constant oxygen supply for metabolic reactions, generating ATP, and the breakdown and conversion of molecules
• CO2 waste products are generated and expelled through breathing
• Respiration involves providing O2 and removing CO2, a process managed by the respiratory system
• Aerobic respiration involves consuming sugar and breathing in O2 to breathe out CO2

Stages of Respiration

• Ventilation (breathing) involves causing the lungs to move; actual mechanical breathing
• Pulmonary gas exchange includes inflating and deflating to exchange gas
• Transport of O2 and CO2 occurs via blood into tissues
• Systemic gas exchange sees tissues exchanging O2 and CO2
• Cellular respiration is the final stage
• Disorders like Hb issues or heart problems can disrupt gas exchange

Anatomy of the Respiratory System

• The upper respiratory tract includes the nose, nasal cavity, pharynx (throat), and larynx (voice box); the epiglottis prevents food from entering the lungs
• The lower respiratory tract facilitates breathing mechanics, including the trachea (windpipe), lungs, bronchi, alveoli (site of chemical reaction and reoxygenation), and the diaphragm muscle
• Alveoli are tiny air sacs where oxygen is supplied and colour changes indicate oxygen levels diagnosed clinically, aided by iron n oxygen chemical reaction

Protection and Structure

• Rib bones protect the lungs, allowing expansion and contraction
• Pleural membrane facilitates lubrication via a thin mesothelial layer with a double membrane (visceral against lungs, parietal against surrounding tissues)
• Pleural cavity contains pleural fluid for lubrication; fluid removal can occur

Pleural Conditions

• Pneumothorax is air in the pleural cavity and is pneumatic
• Pleural effusion involves fluid accumulation
• Haemothorax is blood in the cavity and potentially serious

Gas Laws and Ventilation

• Ventilation is the mechanical flow of air in and out of the lungs
• Boyle's Law means that as pressure increases, volume decreases
• Charles's Law means that temperature increases as volume increases
• Dalton's Law means that all component gases make up total pressure
• Lungs change internal pressure while breathing
• Alveolar pressure increases during inspiration and decreases during expiration
• Intrapleural pressure, within the pleural cavity, is responsive to the diaphragm

Diaphragm and Pressure

• The diaphragm is a dome-shaped muscle that separates the thoracic and abdominal cavities and is the primary muscle used in inspiration
• Nervous system controls the process where diaphragm contraction helps expansion of thoracic cavity and lungs
• Increased cavity volume leads to decreased intrathoracic pressure

Respiratory Control

• The lungs lack muscles for inflation/deflation
• The respiratory muscles and diaphragm control pressure
• Respiratory centres control the rate of contraction

Control Centres and Receptors

• At rest, body cells utilize 200 mL of O2 per minute, increasing 15-20 fold during exercise
• The respiratory system maintains CO2 and O2 levels, responding to bodily fluids such as exercise, illness, and drug therapy
• Chemoreceptors respond to CO2, H+, and O2 levels, providing input to the respiratory centre
• Ventilation increases with PaCO2 rise, and ventilation decreases with PaCO2 fall via respiratory control centres

Gas Exchange

• The respiratory quotient (RQ) is the ratio of carbon dioxide production to oxygen consumption, reflecting fat, carbohydrate, and protein in the diet
• High PO2 is found in the lungs in alveoli and high PCO2 in blood
• Arterial Blood Gases (ABG) enable measurement of blood exchange
• CO2 is the main waste product from respiration

Haemoglobin and Oxygen Transport

• Hemoglobin protein carries oxygen in red blood cells
• Fetal haemoglobin has a higher affinity for O2, absorbing more oxygen
• Muscle transports O2 using myoglobin, which has a higher oxygen affinity than haemoglobin and stores/releases oxygen in muscles
• High temperature and increased acidity (pH decreases) reduce haemoglobin's affinity for O2

Forms of Transport

• Waste CO2 is transported in three forms; as dissolved CO2 (7% in blood plasma), bound to haemoglobin (23%), and as bicarbonate ions (70% in blood plasma)
• A key equation governs respiration-controlled blood pH through carbonic anhydrase
• Hypoxia describes inadequate oxygen support in tissue, causing impaired oxygenation and impaired blood supply