The Respiratory System

Question 1

Name the five functions of the respiratory system

Answer 1

1. Gas exchange SA between air and circulating blood
2. Move air across exchange surfaces of lungs
3. Protect respiratory surfaces from outside environment
4. Produce sounds
5. Olfactory sense

Question 2

Describe the alveoli

Answer 2

• Air-filled pockets
• For gas exchange
• Large SA increases diffusion rate

Question 3

Describe the alveolar epithelium

Answer 3

• Simple squamous epithelium
• Type I pneumocytes: gas exchange
• Type II pneumocytes: produce surfactant
  
  • contains phospholipids and proteins
  • reduces surface tension
  • prevents lung collapse

Question 4

Describe the four types of respiration

Answer 4

• Pulmonary respiration
  
  • process of breathing in the lungs
• External respiration
  
  • gas exchange between blood and environment
  • involves alveoli and capillaries
• Internal respiration
  
  • gas exchange between blood and body tissues
  • involves capillaries and tissues
• Cellular respiration
  
  • metabolic process of cells converting glucose and oxygen into energy
  • occurs in mitochondria

Question 5

How does pulmonary ventilation work?

Answer 5

• Physical movement of air into and out of the lungs
• air flows from high to low pressure
• diaphragm contracts —> volume of thoracic cavity increases —> lung pressure decreases

Question 6

Factors affecting compliance of pulmonary ventilation

Answer 6

• Compliance
  
  • ability of the lung to stretch and expand
• Factors
  
  • Connective tissue structure
  • Surfactant production
  • Mobility of thoracic cage
• Low compliance: fibrosis
  
  • excessive scar tissue formed
  • lung tissue thickens and stiffens
  • rigid and less elastic
• High compliance: emphysema
  
  • elastic fibres destroyed
  • lungs expand easily - overinflate
  • struggle to expel air

Question 7

Explain the control of respiration (eg respiratory groups, muscles involved)

Answer 7

• Inhlation
  
  • Respiratory centers of medulla oblongata become active
  • Signals sent down phrenic nerve
  • Diaphram contracts
  • External intercostal muscles contract
  • Increased thoracic cavity volume
  • Forced breathing: Accessory muscles elevate ribs (Ventral RG)
• Exhalation
  
  • Ventral RG inhibits Dorsal RG, diaphragm and external intercostal muscles relax
  • Forced breathing: Internal intercostal and transversus thoracis: depress the ribs; Abdominal muscles: compress abdomen, force diaphragm upwards

Question 8

What are the diseases associated with the respiratory system?

Answer 8

• Asthma
  
  • Inflammation of bronchi and bronchioles
  • Restricts airflow into alveoli
• Chronic obstructive pulmonary disease (COPD)
  
  • Caused by toxins in cigarettes smoke
  • Increasingly difficult to breathe
• Lung cancer
  
  • Uncontrolled growth of abnormal cells
• Respiratory infections
  
  • eg tuberculosis from bacterial infection
  • eg pneumonia from bacteria/virus/fungi infection

Question 9

Factors affecting oxygen-hemoglobin saturation

Answer 9

• standardized at pH 7.4, 37°C
• partial pressure of O2
  
  • the level of dissolved oxygen in plasma
  • higher PO2 → greater Hb sat
  • each O2 bound makes next O2 binding easier
• blood pH
  
  • pH drops → decreased affinity (shift right)
  • pH rises → increased affinity (shift left)
  • caused by CO2 that dissociates into H+ and HCO3-
• temperature
  
  • temp drops → increased affinity
  • temp rises → decreased affinity

Question 10

Describe CO2 gas transport

Answer 10

• by-product of cellular respiration
• carried three ways
  
  • reaction with H2O forms carbonic acid catalyzed by carbonic anhydrase (70%) → H+ bind to hemoglobin, HCO3- move into plasma: chloride shift
  • bound to hemoglobin in RBC (23%) → carbaminohemoglobin
  • dissolved in plasma (7%)

Question 11

Describe the respiratory reflexes that control respiration

Answer 11

• Chemoreceptors: PCO2, PO2, blood pH in cerebrospinal fluid (CSF)
  
  • Glossopharyngeal nerve from carotid bodies
  • Vagus nerve from aortic bodies
  • Chronic stimulation decreases sensitivity
• Baroreceptors (in aortic/carotid sinus): blood pressure
• Stretch receptors: lung volume
• Irritating physical/chemical stimuli in nasal cavity/larynx/bronchial tree
• Others eg pain, body temp

Question 12

Describe the four pulmonary volumes

Answer 12

• Resting tidal volume (TV): air exchanged during quiet breathing
• Inspiratory reserve volume (IRV): additional air inhaled after forced inspiration
• Expiratory reserve volume (ERV): additional air exhaled after forced exhalation
• Residual volume (RV): air remaining after forced exhalation (NOT expelled from lungs)

Question 13

Describe the four lung measurements

Answer 13

• Inspiratory capacity (IC)
  
  • Maximum volume of air inspired
  • IC = IRV + TV
• Functional residual capacity (FRC)
  
  • Volume of air in the lungs after normal tidal expiration
  • FRC = ERV + RV
• Vital capacity (VC)
  
  • Maximum volume of air exhaled after maximum inspiration
  • VC = TV + IRV + ERV
• Total lung capacity (TLC)
  
  • TLC = VC + RV

Question 14

Describe the organization of the respiratory system

Answer 14

• Upper respiratory system
  
  • Nose
  • Nasal cavity
  • Sinuses
  • Pharynx
• Lower respiratory system
  
  • Larynx
  • Trachea
  • Bronchus
  • Bronchioles
  • Alveoli
• Conducting portion
  
  • From nasal cavity to terminal bronchioles
• Respiratory portion
  
  • Respiratory bronchioles and alveoli