Respiratory L3.2 Flashcards
1) What is the pleura?
2) Layers of pleura
3) What is in bewteen 2 layers of pleura?
4) Intrapleural space What is it? What does it contain?
1) Continuous double layered membrane, surrounds lungs
2) Patietal pleura: outer layer, in contact with chest wall cavity
Visceral layer: Inner layer, attached to surface of lungs
3) Pleural fluid. Reduce frction between lung + chest wall during breathing
4) Between parietal + visceral pleura
Intrapleural fluid. Creates negative pressure to lock lungs and chest walls together, allowing them to move in sync
(UNDERSTANDING: negative pressure: negative relative to atmospheric pressure, helps create suction effect, keeping lungs expanded + adhered to chest wall_
1) What is ventilation?
2) Describe inspiration
3) What is Boyle’s law?
4) Describe expiration
5) What is the purpose of elastic recoil?
1) Prcoess of air moving in and out of lungs through bulk flow. Air flows from regions of higher pressure to lower pressure
2) Ribs + sternum rise: increase vol of thoracic cavity
Diapghragm contracts: move downwards, further increasing volume of thoracic cavity
Thoracic pressure decreases: Air flows into lungs as pressure inside is lower than atmospheric pressure
Boyle’s Law: Inverse relationship between vol and pressure.
4) Ribs and sternum lower: Decrease vol of thoracic cavity
Diaphragm relaxes: moves upwards, reducing thoracic vol
Thoracic pressure increases: air flows of lungs as pressire inside is higher than atmospheric pressure
5) Elastic recoil: Helps in PASSIVE EXHALATION. Reduces energy required during expiration
1) Describe inspiration during relaxed ventilation
1) During relaxed ventilation: Diaphragm contraction responsible for go-75% of inspired air vol
Remaining 25-40% comes from upward and outward movement if rib cage, facilitated by external inercostal muscles
This leads to:
-Chest expansion, pulls lung outwards, increasing thoracic vol
-So, intrapleural pressure becomes more negative
- Negative pressure keeps pleural layers tightly adhered
1) What is forced expiration?
2) State two factors affecting forced expiration
1) Active process requiring abdominal muscles and internal intercostal muscles. Involves pushing air out og lungs with more effort than during relaxed breathing
2) Pregnancy - diapghram limited movement due to abdominal pressure
COPD (and asthma) - narrowing of airways. Difficult to puiush air out.
1) What factors cause lung recoil during expiration?
2) What would happen if the alveoli were lined only with water?
3) How is collapse prevented?
1) - Elastic connective tissue: elasticity, allows recoil + shrink after inhalation stretching
- Alveolar surface tension: Attraction between water molecules at water-air interface in alveoli. Creates force, this collapses alveoli during expiration
2) Surface tension too strong. Complete collapse of alveoli during expiration.
3) Surfactant. Produced by lungs. Reduces alveolar suface tension. Ensure alveoli remain open during expiration, preventing collapse. makes breathing easier.
What is the relationship between collapsing pressure and radius of alevolus?
Inversely proprtional. As the radius decreases, the pressure needed to prevent collapse increases.
Smaller alveoli (with a smaller radius) have higher collapsing pressure compared to larger alveoli. This means that during expiration, smaller alveoli are more prone to collapse.
1) Describe the location of capillaries within the alveoli
2) Where are Septal cells / Type II pneumocytes found? Function?
3) What type of molecule is surfactant? Function?
1) run around margins of alveolus. Facilitate gas exchange.
2) aka Type II alveolar cells. Found in septa (thin walls between adjascent alveoli).
Primary function = produce surfactant
3) Phospholipoprotein. Reduces surface tension within alveoli. Which helps prevent alveolor collapse during expiration (ensures alveoli stay open, makes breathing easier). Surfactant also keels alveoli dry by reducing fluid accumulation.
1) What happens to alveoli without surfacant?
What happens to alveoli with surfactant?
Respiratory Distress Syndrome of Newborn (RDS)
Describe how it happens
- Fetal lungs do not produce surfactant until late pregnancy
- Premature babies (<28 weeks) do not produce enough surfactant
- Lack of surfactant = RDS
- Insufficient surfactant = highsurface tension = difficult for lungs to inflate
Alveoli fail to open during inspiration = INEFFICIENT GAS EXCHANGE
= Severe difficulty breathing - Baby must make STRENUOUS INSPIRATORY EFFORTS to overcome high surface tension + inflate lungs
Mechanics of breathing
Talk about pressure differences + airflow
If Patm = PA, there is no airflow.
If PA < Patm, air flows into the lungs (inspiration).
If PA > Patm, air flows out of the lungs (expiration).
PA: alveoar pressure in lungs
Patm: atmospheric pressure
- Normal pressure in pleural cavity
Pressure slightly less than atmospheric pressure. Creates negative pressure, keeps ;ungs inflated.
What is pneumothorax?
How does it happen?
Collapsed lung
- Pleural cavity damaged
- Air enters pleural sapce (because pressure in pleural space less than atmospheric)
- Intrapleural pressure becomes equal to or greater than Patm
- Therefore, pressure surrounding lung increases (no longer negative)
- Causes lung collapses completely / partially
- Lung no longer properly function, inflate, deflate, impairs gas exchange
What is pleurisy? (Pleuritis)
What are the main causes?
What are key symptoms?
- Inflammation of parietal pleura.
- Causes parietal layer + visceral layer to rub against each other during breathing
- Leads to SHARP LOCALISED CHEST PAIN
- Mainly during inspiration
Causes:
-Viral(influenza),bacterial (pneumonia), fungal infections, autoimmune disorder (rheumatoid arthritis)
SYMPTOMS
- Pain felt on one side of chest, radiates to shoulder + back
- Sharp, localised chest pain, worse when inhaling deeply
1) What is lung compliance?
1) Ability of lungs to stretch + expand. Change in lung vol per unit of pressure.
Slope of pressure-volume curve
Steep slope = high compliance
Normal state - lungs are highly compliant - easily expand with small increase in pressure
At higher pressures, lungs become stiffer, due to limit of elasticity, compliance decreases, represented by flattened slope of pressure volume curve
Which conditions reduce lung compliance?
- Pulmonary fibrosis
- Atelectasis
- Increased pulmonary venous pressure
1) What is emphysema?
2) What is the difference between emphysema and pulmonary fibrosis
1) Type COPD (chronic obstrucive pulmonary disease). Destruction of elastic fibres (allows lungs to recoil) + collagen (structural support).
2. Loss of recoil, lungs do not deflate easily in exhalation
3. Leads to air trapping. Air stuck in alveoli, overdistension of lungs
4. Increased lung compliance: lungs expand more easily, recoil less effectively
Pulmonary fibrosis
-scarring of lungs
-scar tissue replaces normal lung tissue
-scar tissue less elastic
-harder for lungs to expand
-therefore, less compliant (stiffer)
Lung compliance formula
Compliance (C) = Change in Volume (V) / Change in Pressure (P)
Lung compliance refers to how easily the lungs can expand with a given pressure change.
C=V/P : Normal lung compliance
Give an example of a structural change in the thorax which affects lunng compliance
Kyphoscoliosis
Structural changes in thorx
Leads to reduced lung compliance
Kyphoscoliosis involves both, kyphosis (exaggerated forward curvature of spine) + scoliosis (lateral/sideways curvature of spine)
- What is turbulent flow?
- Give 2 characteristics
- Where does it primarily occur and why?
- What is the flow pressure relationship?
- Most common circumstance
- Air mocement chaoric, irregular. Creates more resistance
- NOT SMOOTH, NO PARALLEL LAYERS, NOT PREDICTABLE
- Larger airways (trachea, bronchi), air flow is fast
- nonlinear. Small increase in pressure = disproportionately large increases in resistance, making it less predictable than laminar flow.
- Heavy breathing / high ventilation rate
What is Poiseuille’s Law and Airflow?
Poiseuille’s Law describes the relationship between the driving pressure, the flow of a fluid (in this case, air), and the radius of the tube through which the fluid moves. It is often applied to understanding laminar flow in airways, and it shows that the radius of the tube (airway) is the most significant factor affecting airflow.
KEY POINT: The most important factor in determining airflow is the radius of the airway.
State two sites of airway resistance
What is a common sign of patients with nasal obstruction when exercising?
Airway resistance: opposition to airflow in resp system
- Upper tract (nose, pharynx, larynx)
SIGNIFICANT RESISTANCE IN NOSE (because prone to nasal congestion from inflammation due to cold etc)
Mouth breathing. Mouth offers larger airway, less resistance
- Lower respiratory tract (MOST IMPORTANT: BRONCHIAL TREE)
Most important part of bronchial tree: small bronchi, bronchioles
They physiologically control airwat reistsance
Because innervated by smooth muscle (this regulates airway diameter)
MOST AIRWAY RESISTANCE IS IN UPPER TRACT. But, small bronchi, bronchioles in lower respiratory tract are important for regulating resistance due to smooth muscle innervation (can dilate + constrict airways)
1) How does asthma affect air way resistance?
1) Increases airway resistance (therefore, breathing difficulties)
Asthma = airway narrowing (reduction of airway diameter). Due to:
a) Contraction of smooth muscle
b) inflammation (+ swelling)
