Chapter 22 - Respiratory System Flashcards
Respiration - major function
To supply O2 to tissues and remove CO2 from body
Pulmonary ventilation
(breathing)-
movement of air into and out
of lungs
External respiration
O2 and CO2
exchange between lungs and blood
Circulatory System
Transport-O2 and CO2 in blood
Internal respiration-O2 and CO2
exchange between systemic blood
vessels and tissues
Conducting zone
conduits to gas exchange sites
Respiratory zone
site of gas exchange
The Nose
Provides an airway for respiration
Moistens and warms entering air
Filters and cleans inspired air
Resonating chamber for speech
Houses olfactory receptors
Isthmus of fauces
Part of OroPharynx
opening to oral cavity
Respiratory Membrane
Alveolar and capillary walls and their fused basement membranes
~0.5- m-thick; gas exchange across membrane by simple diffusion
Cells of Alveolar Walls
Single layer of squamous epithelium (type I alveolar cells)
Scattered cuboidal type II alveolar cells secrete surfactant and antimicrobial proteins
Pulmonary circulation
(low pressure, high volume)
Pulmonary arteries deliver systemic venous blood to lungs for oxygenation
Pulmonary veins carry oxygenated blood from respiratory zones to heart
Bronchial arteries
provide oxygenated blood to lung tissue
Part of systemic circulation (high pressure, low volume)
Supply all lung tissue except alveoli
Pulmonary veins carry most venous blood back to heart
Pleurae
thin, double-layered serosa; divides thoracic cavity into two pleural compartments and mediastinum
Pleural fluid fills pleural cavity
Provides lubrication and surface tension assists in expansion and recoil
Atmospheric pressure (Patm)
Pressure exerted by air on the body
760 mm Hg at sea level = 1 atmosphere
Respiratory pressures are relative to Patm
Intrapulmonary (intra-alveolar) pressure (Ppul)
pressure in alveoli
Fluctuates with breathing
Always eventually equalizes with Patm
Intrapleural pressure (Pip)
Pressure in pleural cavity
Fluctuates with breathing
Always a negative pressure (
Atelectasis
(lung collapse) due to plugged bronchioles - collapse of alveoli
Inhalation
Diagphragm contracts intercostal muscles contract Lungs expand Volume Changes Pressure changes Gases flow to equalize pressure change
Boyle’s Law
Relationship between pressure and volume of a gas
Gases fill container; if container size reduced increased pressure
Forced Inspiration
During exercise - accessory muscles (scalenes, sternocleidomastoid, pectoralis minor) further increase in thoracic cage size
Exhalation
Diagphragm relaxes intercostal muscles relax Lungs recoil Volume Changes Pressure changes Gases flow to equalize pressure change
3 Factors Hinder Pulmonary Ventilation
Airway resistance
Alveolar surface tension
Lung compliance
(require energy)
Surfactant
Detergent-like lipid and protein complex produced by type II alveolar cells
Reduces surface tension of alveolar fluid and discourages alveolar collapse
Non respiratory Air movements
Most result from reflex action; some voluntary
Examples include-cough, sneeze, crying, laughing, hiccups, and yawns
External respiration
diffusion of gases in lungs
O2 and CO2 across respiratory membrane
Influenced by
Thickness and surface area of respiratory membrane
Partial pressure gradients and gas solubilities
Ventilation-perfusion coupling
Internal respiration
diffusion of gases at body tissues
Capillary gas exchange in body tissues
Partial pressures and diffusion gradients reversed compared to external respiration
Tissue Po2 lower than arterial blood oxygen from blood to tissues and CO2 - from tissues to blood
Dalton’s Law of Partial Pressures
Total pressure exerted by mixture of gases = sum of partial pressures exerted by each gas = directly proportional to its percentage in mixture
Henry’s Law
When gas mixtures are in contact with liquid, each gas dissolves in proportion to its partial pressure and depends on:
Solubility–CO2 20 times more soluble than O2
Temperature–as it rises, solubility decreases
Composition of Alveolar Gas
Alveoli contain more CO2 and water vapor than atmospheric air
Gas exchanges in lungs
Humidification of air
Mixing of alveolar gas with each breath
Ventilation-Perfusion Coupling
Perfusion-blood flow reaching alveoli
Ventilation-amount of gas reaching alveoli
Ventilation and perfusion matched (coupled) for efficient gas exchange
Oxyhemoglobin
hemoglobin-O2 combination
Reduced hemoglobin (deoxyhemoglobin)
hemoglobin that has released O2
Factors affecting loading and unloading of Hemoglobin
Facilitated by change in shape of Hb
As O2 binds, Hb affinity for O2 increases
As O2 is released, Hb affinity for O2 decreases
Po2
Temperature increase - affinity decreases
Decrease Blood pH (more H+) - affinity decreases
Pco2
Concentration of BPG–produced by RBCs during glycolysis; levels rise when oxygen levels chronically low
Venous reserve
Oxygen remaining in venous blood
Just in case oxygen
Bohr effect
Relationship between O2 affinity to bind with Hb is inversely related to the both pH and carbon dioxide concentration. CO2 becomes bicarbonate ion and H+ which binds with Hb and changes shape decreasing O2 affinity to bind. Reason O2 goes to tissues.
Equation for Co2 & Water
Co2 + H2o = H2Co3 (carbonic acid) = turns into H+ (hydrogen ion (basic) and HC03 (bicarbonate ion)
Anemic Hypoxia
Too few RBCs abnormal or too little Hemoglobin
Ischemia Hypoxia
impaired or blocked circulation
Histotoxic Hypoxia
cells unable to use 02, metabolic poison
Hypoxemic Hypoxia
abnormal ventilation, pulmonary disease
How is Co2 transported in the blood
7-10% dissolved in plasma
20% bound to globin of hemoglobin (carbaminohemoglobin)
70% transported as bicarbonate ions in plasma (HC03-)
What happens in systemic capillaries
HC03- Quickly diffuses from RBCs into plasma
Chloride Shift
Outrush of HC03- from RBCs balanced as Chloride moves into RBCs from plasma
What happens in pulmonary capillaries
HC03- moves into RBCs (Chloride leaves)
Bdins with H+ to form H2C03 which is split by carbonic anhydrase into H2O and C02 which diffuses into alveoli
Haldane Effect
Amount of Co2 transported affected by P02
COPD
Exemplified by chronic bronchitis and emphysema
Irreversible decrease in ability to force air out of lungs
History of smoking in 80% of patients
Dyspnea - labored breathing Coughing and frequent infections
Most develop respiratory failure (hypoventilation) accompanied by respiratory acidosis, hypoxemia
Emphysema
Destruction of alveolar walls, enlargment; decreased lung elasticity
Accessory muscles necessary for breathing - exhaustion
Hyperinflation flattened diaphragm - reduced ventilation efficiency
Damaged pulmonary capillaries - enlarged right ventricle
Chronic bronchitis
Inhaled irritants
chronic excessive mucus
Inflamed and fibrosed lower respiratory passageways
Obstructed airways
Impaired lung ventilation and gas exchange
pulmonary infections
Tuberculosis (TB)
Infectious disease caused by bacterium
Symptoms-fever, night sweats, weight loss, racking cough, coughing up blood
Treatment- 12-month course of antibiotics
Lung cancer: Leading cause of cancer deaths in North America, 90% smokers
Adenocarcinoma: peripheral lung areas - bronchial glands, alveoli
Squamous cell carcinoma: bronchial epithelium
Small cell carcinoma: lymphocyte-like cells that originate in primary bronchi and subsequently metastasize
Cystic fibrosis
Most common lethal genetic disease in North America
Viscous mucus clogs passageway, bacterial infections in lungs, clogged pancreatic ducts, reproductive ducts
Cause = abnormal gene for Cl- channel
