week 9

Question 1

Functions of the Respiratory System

Answer 1

1. Gas Exchange: Oxygen and carbon dioxide exchange in the lungs.
   
   2. Air Movement: Delivers air to lungs and removes air.
   3. Protection: Protects from dehydration, temperature changes, and pathogens.
   4. Sound Production: Assists in vocalization.
   5. Olfactory Sensation: Relays smell information to the CNS.

Question 2

Organs of the Respiratory System

Answer 2

• Upper Respiratory System: Nose, nasal cavity, paranasal sinuses, pharynx.
  
  • Lower Respiratory System: Larynx, trachea, bronchi, bronchioles, alveoli.

Question 3

Nose and Nasal Structures

Answer 3

• External Nares: Nostrils for air entry.
  
  • Nasal Vestibule: Space inside the nose with hair to trap particles.
  • Nasal Conchae: Filters, warms, and humidifies air.
  • Internal Nares: Openings into the nasopharynx.

Question 4

Pharynx

Answer 4

• Nasopharynx: Air passage with ciliated epithelium.
  
  • Oropharynx: Food and air passage, stratified epithelium.
  • Laryngopharynx: Resists abrasion and chemical attack.

Question 5

Larynx

Answer 5

• Glottis: Opening to trachea.
  
  • Thyroid Cartilage: Protects the glottis (Adam’s Apple).
  • Cricoid Cartilage: Protects glottis and trachea.
  • Epiglottis: Prevents food from entering the trachea.

Question 6

Trachea & Primary Bronchi

Answer 6

• Trachea: Flexible tube with C-shaped cartilage.
  
  • Primary Bronchi: Right bronchus wider and shorter, left bronchus narrower and longer.

Question 7

Lungs and Pulmonary Lobules

Answer 7

• Lung Structure: Left lung has 2 lobes, right lung has 3 lobes.
  
  • Pulmonary Lobules: Smallest lung compartments with terminal and respiratory bronchioles, and alveoli.

Question 8

Alveoli

Answer 8

• Type I Cells: Simple squamous epithelium for gas exchange.
  
  • Type II Cells: Secrete surfactant to reduce surface tension.
  • Alveolar Macrophages: Remove foreign particles.

Question 9

Respiratory Membrane

Answer 9

• Composed of:
  1. Squamous epithelium of alveolus
  2. Endothelial cells of capillary
  3. Fused basal laminae
  
  • Key Features:
    ○ Thin for fast diffusion.
    ○ Lipid-soluble gases move easily.
    ○ Large difference in partial pressure aids diffusion.
    ○ Large surface area (~30-50m²).
    ○ Coordinated blood and airflow.

Question 10

Pulmonary Volumes and Capacities

Answer 10

• Tidal Volume (TV): Air inhaled/exhaled during normal breathing.
  
  • Inspiratory Reserve Volume (IRV): Max air inhaled after normal breath.
  • Expiratory Reserve Volume (ERV): Max air exhaled after normal breath.
  • Residual Volume (RV): Air remaining after max exhalation.
  • Functional Residual Capacity (FRC): Air remaining after normal exhalation.
  • Inspiratory Capacity (IC): Max air inhaled after normal exhalation.
  • Total Lung Capacity (TLC): Total air capacity of the lungs.
  • Vital Capacity (VC): Max air exhaled after max inhalation.

Question 11

External vs Internal Respiration

Answer 11

• External Respiration: Gas exchange between blood and air in lungs.
  
  • Gas Transport: Transport of gases between lungs and tissues.
  • Internal Respiration: Gas exchange between blood and tissues of the body.

Question 12

Steps in External Respiration

Answer 12

1. Pulmonary Ventilation: Breathing.
   
   2. Gas Diffusion: Exchange of gases between alveolar air and blood in capillaries.

Question 13

Physical Principles of Pulmonary Ventilation

Answer 13

• Boyle’s Law: Inverse relationship between pressure and volume of gas (P α 1/V).
  
  • Air Movement: Air flows from high to low pressure.
  • Pleural Cavity:
    ○ Pleural fluid reduces friction.
    ○ Diaphragm and ribs control thoracic cavity volume.
    ○ Pressure: ↑ lung volume = ↓ pressure, ↓ lung volume = ↑ pressure.

Question 14

Respiratory Muscles and Movements

Answer 14

• Muscles for Inhalation:
  ○ Diaphragm: 75% of air movement.
  ○ External Intercostals: 25% of air movement.
  ○ Accessory muscles (sternocleidomastoid, pectoralis minor) for active breathing.
  
  • Muscles for Exhalation:
    ○ Elastic recoil mainly; internal intercostals and abdominal muscles assist.

Question 15

Gas Diffusion Principles

Answer 15

• Dalton’s Law: PN2 + PO2 + PCO2 = Total atmospheric pressure.
  
  • Henry’s Law: Gas solubility depends on partial pressure and solubility.
    ○ O2: Low solubility in blood.
    ○ CO2: 20x more soluble than O2.

Question 16

Partial Pressures of Gases

Answer 16

• Alveolar Air:
  ○ PO2 = 100mmHg
  ○ PCO2 = 40mmHg
  
  • Deoxygenated Blood:
    ○ PO2 = 40mmHg
    ○ PCO2 = 45mmHg
  • Oxygenated Blood:
    ○ PO2 = 95mmHg
    ○ PCO2 = 40mmHg
  • Metabolising Tissues:
    ○ PO2 = 40mmHg
    ○ PCO2 = 45mmHg

Question 17

Oxygen Transport in Blood

Answer 17

• Oxygen Solubility: ~1.5% of O2 dissolved in plasma.
  
  • Hemoglobin: ~98.5% of O2 bound to Hb (hemoglobin) in RBCs.
    ○ PO2 ↑ = Hb saturation ↑.
    ○ Carbon monoxide binds more strongly to Hb than O2.

Question 18

Carbon Dioxide Transport in Blood

Answer 18

• Bicarbonate Ions: CO2 + H2O ⇔ H+ + HCO3- (70% of CO2 carried this way).
  
  • Bound to Hemoglobin: ~23% of CO2.
  • Dissolved in Plasma: ~7% of CO2.

Question 19

Steps in Internal Respiration

Answer 19

1. Gas Exchange in Tissues: Oxygen detaches from Hb and diffuses into cells (PO2 lower in cells).
   
   2. Carbon Dioxide Diffusion: CO2 diffuses from cells into blood (PCO2 higher in cells).
      ○ CO2 is then converted to bicarbonate, bound to Hb, or dissolved in plasma.

Question 20

Central Nervous System Control of Respiration

Answer 20

• Respiratory Rate (RR): Number of breaths per minute (12-18 bpm resting, kids 18-30 bpm).
  
  • Tidal Volume (VT): Amount of air moved in/out per respiratory cycle (~500ml).

Question 21

Voluntary and Involuntary Control of Respiration

Answer 21

• Voluntary Control: Conscious control of rate and depth of breathing.
  
  • Involuntary Control: Brain regulates rate and depth of respiration, controls respiratory muscles.

Question 22

Respiratory Centres in the Brainstem

Answer 22

• Medulla Oblongata:
  ○ Dorsal Respiratory Group (DRG):
  § Inspiratory centre, controls diaphragm and external intercostals.
  § Maintains rhythm for quiet and forced inspiration.
  ○ Ventral Respiratory Group (VRG):
  § Active only in forced breathing.
  § Controls accessory muscles for forced inspiration and expiration.
  
  • Pons (Pontine Respiratory Group):
    ○ Apneustic Centre: Stimulates DRG, increases depth of inhalation.
    ○ Pneumotaxic Centre: Inhibits DRG, controls overall breathing rate.

Question 23

DRG and VRG Interaction

Answer 23

• DRG: Constant rhythm for normal and forced inspiration.
  
  • VRG: Involved only in forced breathing (expiration/inspiration).
  • Pons: Modulates DRG to adjust breathing rate and depth.

Question 24

Chemoreceptor Reflex

Answer 24

• Function: Chemoreceptors detect changes in pH (H+), CO2, and O2 to regulate respiration.

Question 25

Location of Chemoreceptors

Answer 25

* Peripheral Chemoreceptors: ○ Carotid artery (carotid bodies). ○ Aortic arch (aortic bodies). * Central Chemoreceptors: ○ Located in the Medulla Oblongata.

Question 26

Mechanism of Chemoreceptor Reflex

Answer 26

* CO2: ○ Most important factor in regulating respiration. ○ ↑CO2 → ↑H+ → activates central chemoreceptors → stimulates inspiration. ○ In blood, CO2 activates peripheral chemoreceptors, increasing ventilation. * O2: ○ Less important; needs to drop to 60mmHg before affecting respiration. ○ Only peripheral chemoreceptors involved.