Respiration Flashcards
What are the two zones of the lungs and respiratory system?
Conducting zone and respiratory zone
What generation is the conducting zone?
Generation 0-16
Trachea –>bronchioles
What generation is the respiratory zone?
Generation 17-23
In which zone does gas exchange occur?
Respiratory zone only
What is the function of the conducting zone?
Conditions incoming air:
- Filters
- Warms
- Humidifies
Structure of bronchial wall
- Cartilage rings
- Smooth muscles
- Mucous glands
- Elastic tissue
Respiratory epithelium
- Ciliated epithelia
- Goblet cells
- Sensory nerve endings
Where do the sensory nerve endings lie and what do they do?
Lie underneath tight junctions and detect noxious stimuli
What do goblet cells do?
Produce musin –> dissolves in fluid layer to form mucuous
What are bronchioles lined by?
Respiratory epithelium
What is the air-blood barrier?
A ‘sandwich’ created by flattened cytoplasm of type 1 pneumocytes and the capillary wall
Type 1 pneumocytes
- Squamous alveolar cells
- Organelles clustered around nucleus
- Reduced thickness
Type 2 pneumocytes
- Produce surfactant
- Reduce alveolar surface tension
- Can replicate and produce type 1
Which type of pneuomcytes produce surfactant?
Type 2
Which muscles are used in quiet inspiration?
Primary muscles of inspiration
- contraction of diaphragm and external intercostal muscles
Mechanism of quiet inspiration
Thoracic and lung volume increase
Therefore pressure decreases and air moves in down the pressure gradient
- follows Boyle’s law: absolute pressure ∝ 1/volume
Which muscles are used in forced inspiration?
Primary muscles of inspiration and accessory muscles
involves:
- scalene muscles (move ribcage up)
- sternocleidomastoids (attached to sternum)
- neck/back muscles
- upper respiratory tract muscles
Quiet expiration mechanism
Passive process using elastic recoil
Relaxation of diaphragm and external intercostal muscles
What are the primary muscles of expiration?
There are none
Forced expiration mechanism
Involves; accessory muscles, internal intercostals, abdominal muscles, neck/back muscles
What is the pleura?
Serous membrane. Pleural cavity between two pleura membranes filled with secretions
What is the function of the pleura?
Prevents lungs from sticking to chest wall
What is the pressure of the inter pleural space at rest?
Sub-atmospheric
What is a pneumothorax?
Collapsed lung due to presence of air in the pleural cavity
What would happen if inspired during pneumothorax?
Due to inter pleural space equaling atmospheric pressure, elastic nature of lungs would take over and collapse to minimal volume
How would you treat a pneumothorax?
Path the puncture in the membrane and put a chest tube in to allow the lungs to reinflate gradually expelling air from the pleural cavity
What is compliance?
A measure of elasticity in lung
C = ∆V/∆P
What does a low compliance means in terms of ventilation?
More work needed for inspiration
What does a high compliance means in terms of ventilation?
Difficulty expiring - loss of elastic recoil
What are the two components to elastic recoil?
- Elastic nature of cells/ECM
- Recoil due to surface tension generated at air-fluid interface from fluid layer on alveoli
Which equation the relationship between water and air on alveoli surface tension?
Laplace’s equation
Are all the air sacs in the lung the same volume?
No, many air sacs of different volumes
What does Laplace’s equation show about smaller and larger air sace?
Pressure in larger sacs is lower so air flows from smaller alveoli to larger, collapse
What is Laplace’s equation?
P = 2T/r
Role of surfactant lining alveoli
- Reduce surface tension
- Prevents alveoli collapsing
- Prevents over-inflation
What is the surfactant lining alveoli composed of?
Lipids and proteins, produced by type 2 pneumocytes
What is lung volume measure by? What can’t be measured by this?
Spirometer
Residual lung volume cannot be measure
What are the two types of dead space?
Anatomical: volume of conducting zone
Physiological: volume of lung not participating in gas exchange
What is tidal volume?
Normal volume of air displaced during normal inspiration and normal expiration
What is FEV1?
The volume of air displaced in a forced expiration in one second
What is the inspiration capacity?
The total volume of air that can be inspired after normal expiration
What is the expiration reserve volume?
The additional amount of air that can expelled after a normal exhalation
What is the residual volume?
The amount of air that is left after expiratory reserve volume is exhaled
What is vital capacity?
The maximum volume of air that can be inhaled or exhaled during a respiratory cycle
IC + ERV
Using lung volumes, what can be a good health indicator?
FEV1/VC
Which technique is used to measure functional residual capacity?
Helium dilution technique
Lung volumes during exercise
- Tidal volume increases
- Reserve volumes decreases
- TLC and RV remain the same
Two factors that affect the airflow in the lung
- Difference of pressure
- Resistance
V = ∆P/R
Which law is the impact of resistance on flow determined by?
Poiseuille’s Law: Airway resistance is proportional to gas viscosity and the length of the tube but is inversely proportional to the fourth power of the radius
What is the airway resistance inversely proportional to?
The fourth power of the radius
Factors affecting resistance
- Airway diameter
- Mucous secretion
- Oedema
- Airway collapse
Control of bronchial smooth muscle: Constriction
ANS and humoral factor
Parasympathetic - ACh released from vagus and acts on muscarinic receptors
(humoral factor) histamine - released during inflammatory response
Control of bronchial smooth muscle: Dilation
ANS and humoral factor
Sympathetic - Norepineprine released - weak agonist
(humoEral factor) Epinephrine - better agonist
Is the inter pleural pressure greater at the apex or the base?
The apex
What is Dalton’s law?
The total pressure of a mixture of gases is the sum of their individual partial pressures
Which law is used for gases in solution?
Henry’s Law
What kind of structure does haemoglobin have?
Tetrametric structure with a mW of 68kD
Haem unit and global chain
2 alpha and 2 beta chains
What chains are in children’s haemoglobin?
2 alpha and 2 gamma chains
What is the haem unit in haemoglobin?
Porphyrin rin containing single iron atom
Which enzyme converts Fe3+ —> Fe2+?
Methaemoglobin reductase
What two states does haemoglobin exist in? What are their affinities for O2?
Tense - Low affinity for O2
Relaxed - High affinity for O2
Haemoglobin dissociation curve: Temperature
Increase - shifts curve right
Decrease -shifts curve left
Haemoglobin dissociation curve: pH
Increase - shifts curve left
Decrease - shifts curve right
What is the Bohr shift?
Shift in dissociation curve caused by pH
What binds with a higher affinity to haemoglobin?
2, 3-diphosphoglycerate
What occurs in tissues undergoing respiration which shifts the dissociation curve right?
- Increased temperature
- Increased CO2 production
- Increased production of 2, 3-DPG
- Decrease in pH
What replaces the ß-globin chains in foetal haemoglobin?
Gamma chains (these aren’t sensitive to 2, 3-DPG)
Which has a higher affinity for oxygen: haemoglobin of foetal haemoglobin?
Foetal haemoglobin - curve is leftwards or normal Hb
How does the blood carry CO2?
- Dissolved CO2
- Carbonic acid
- Bicarbonate ions
- Carbonate ions
- Carbamino compounds
How and where is CO2 converted to carbonic acid?
Carbonic anhydrase in lungs
