Intro to Respiratory Physiology
Define Respiration
Respiration refers to all steps in the interchange of gases between the atmosphere and the cells of the body
What reduces surface tension within alveoli?
Surfactant
How does gas exchange occur?
Diffusion
What is the primary factor in the control of breathing?
CO2
What is the primary limiting factor for athletic performance in the health horse
Respiratory System
Define Cellular Respiration
Intracellular process in which organic materials are oxidised to produce ATP, water and CO2
Define Minute Ventilation
Volume of air moved in or out of the total respiratory tract each minute
What happens to atmospheric pressures and hence partial pressures at altitude?
Reduced
Name the 3 basic elements of the respiratory control system
Sensors, Central controller, Effectors
How does gas exchange occur during fetal life
Through the placenta – diffusion across blood-blood barrier between maternal & fetal blood vessels.
Supplies deoxygenated blood to alveoli for oxygenation
Pulmonary artery
Air leaks into the pleural space causing the partial vacuum to be lost resulting in lung collapse.
Pneumothorax
Define hypoxaemia and name at least 1 of the 4 listed causes
Deficiency of oxygen in the blood
Causes: Diffusion limitation
Ventilation/perfusion (V/Q) inequality
Shunting of blood (bypasses ventilated areas of the lungs)
Hypoventilation
What controls the basic rhythm of breathing?
Respiratory centres in the medulla and pons
What is the stimulus to take the first breath?
Hypoxaemia and hypercapnia from loss of placental gas exchange.
Where is blood flow preferentially distributed in quadrupeds?
Dorsal regions
Expansion of the thoracic cavity during inspiration is due to:
Diaphragm, External intercostal muscles, Volume increases therefore pressure inside is less than atmospheric.
Rightward shift (higher P, higher temp., lower pH) in the Oxyhaemoglobin dissociation curve causes:
Decreased affinity, oxygen is unloaded more easily off haemoglobin
What acid-base disturbance results from hypoventilation
Respiratory acidosis
Adaptations (acclimatisation) to altitude
Hyperventilation
Polycythemia
Rightwards shift of O2-Hb dissociation curve
Increased capillarization of tissues
Changes in oxidative enzymes.
Name the non-specific (innate) defences of the respiratory system
Cough/sneeze
Deposition of particulate matter in the URT
Mucociliary System
Resident phagocytic cells
Define Lung Compliance. What is it dependent on?
A measure of elasticity or ease with which lungs inflate.
Surface tension within alveoli, elasticity of tissues within the lung & thoracic cage.
How can CO2 be transported in blood?
Chemical combination:
- Bicarbonate
- Protein bound
Where are the most important chemoreceptors for control of ventilation situated?
Ventral surface of the medulla
Fetal lung is inflated with fluid (around 40% total lung capacity) – what happens to it?
Fluid squeezed out during passage through birth canal
Remainder of fluid aids initial lung inflation by reducing pressures required.
Fluid removed via capillaries and lymphatics