pulmonary ventilation Flashcards
What are the two forms of lung expansion?
- Movement of the diaphragm to lengthen and shorten the thoracic cavity. Normal breathing. 2. Expansion and depression of the rib cage. Heavy breathing-relies on the contraction of abdominal muscles.
What are the 4 most important muscles involved in expanding the rib cage?
- External intercostal muscles. 2. Sternocleidomastoid 3. Anterior serrati 4. Scaleni
What is the role of the sternocleidomastoid?
To raise the sternum.
What is the role of the anterior serrati and scaleni?
To lift the ribs. The scaleni lift the first two ribs.
What are the muscles of expiration?
- Abdominal recti 2. Internal intercostal muscles
What is the midline of the thoracic cavity called?
Mediastinum
What are the two pleural membranes called?
Visceral and parietal. Note they are the same membrane just on two different surfaces.
What surface is the visceral pleura found on?
Superficial surface of the lungs
What surface is the parietal pleura found on?
The inner surface of the thoracic cavity
What is found in the mediastinum section of the thoracic cage?
The hilum of the lungs.
What is the pleural pressure?
The pressure exerted by the pleural fluid between the visceral and parietal pleura.
What is the value of the pleural pressure at the beginning of inspiration? ii. Why is this?
- -5cm of water pressure ii. Due to the slight suction of pleural fluid into the lymphatic system.
What value does the pleural pressure reach on average during normal inspiration?
-7.5cm of water pressure
How many litres does the lung volume increase by during inspiration?
0.5 L
What does occlusion of a pathway mean?
BLOCKED- must remember this.
What is the alveolar pressure at the beginning of inspiration?
0 cm of water pressure. (atmospheric pressure)
In order for a pressure gradient to occur, what value does the alveolar pressure drop to?
-1 cm of water pressure.
In order for expiration to occur what value does the alveolar pressure rise to?
+1 cm of water pressure.
Define transpulmonary pressure.
It is the difference in pressure between the alveolar and pleural pressures. It is also a measurement of the elastic forces in the lungs which tend to collapse them at each instant of respiration. This is called recoil resistance.
Define Lung compliance.
The ability to for the lungs to expand for each unit increase of Transpulmonary pressure. This is provided that the lungs are given time to reach equilibrium.
What are the two types of elastic forces which affect lung compliance?
- Parenchymal elastic forces.I.e the collagen and elastin fibres found in the parenchyma of the lungs. 2. Elastic forces caused by surface tension.
What is a surfactant?
A mixture of Phospholipids, proteins, and ions. It is a surface-active agent of water.
Where is the surfactant secreted from?
Type ii alveolar epithelial cells. These cells are granular.
What are the most important factors of the surfactants?
- dipalmitoyl phosphatidylcholine 2. surface apoproteins 3. calcium ions
what is the equation for pressure in regards to occluded alveoli caused by surface tension?
Pressure= 2*surface tension/radius of alveolus
Define surface tension.
The characteristic of water particles on the surface to have a strong attraction to water particles on the inner surface due to cohesion. This maintains the rigidity of the shape and minimizes the surface area.
What is the average size of an alveolus?
100 micrometers
At roughly what period in gestation is surfactant made?
6-7 months
What is the name of the condition found in premature babies wherein the likelihood for their alveoli to collapse is 8 times greater then in normal people?
Newborn Respiratory distress syndrome.
What is the difference between the compliance of the lungs compared to the entire pulmonary system?
the pulmonary system’s compliance is exactly half the value in comparison to the lungs. ~110ml/cm of water pressure to 200ml/cm of water pressure.
What are the three forms of work in which inspiration requires energy to battle against?
- Elastic work - refers to the elastic fibres which prevent the expansion of lung. 2. tissue resistance work - refers to the viscosity of the lung and chest walls. 3. airway resistance work- refers to the resistance from the airways.
What machine can be used to measure pulmonary ventilation?
Spirometer.