Gaseous Exchange | Free Demo Test

The amount of air that is inhaled/exhaled at rest (normally) is called
Tidal Volume. The average tidal volume is 500ml.

arbonic acid (H2CO3) is a weak acid and is therefore in equilibrium with bicarbonate (HCO3−) in solution.
· When significant amounts of both carbonic acid and bicarbonate are present, a buffer is formed.
· This buffer system can be written as H2CO3+ H2O –> H3O+ + HCO3−.

· Under normal circumstances there is much more bicarbonate present than carbonic acid (20 : 1).
· As normal metabolism produces more acids than bases, the blood with its high base concentration, is able to neutralize the metabolic acids produced.

Blood is the medium of transport for oxygen and carbon dioxide. About 97 per cent of oxygen is transported by RBCs in the blood. The remaining 3 per cent of oxygen is
carried in a dissolved state through the plasma. Nearly 20- 25 per cent of carbon dioxide is transported by RBCs, whereas 70 per cent of it is carried as bicarbonate
ions. About 7 per cent of carbon dioxide is carried in a dissolved state through plasma.

Blood buffers play an important role in CO2 transport
Although much CO2 is carried in the blood, yet blood does not become acidic. It is due to CO2 transport and buffering action of blood. The main buffer present in the blood is bicarbonate. Bicarbonates exist in equilibrium with carbonic acid which in turn can be converted
to CO2 and water. H2O+CO2⇋H2CO3⇋H++HCO

Residual Volume(RV)
It is the volume of air remaining in the lungs after maximal exhalation. Normal adult value is averaged at 1200ml(20‐25 ml/kg) . It is indirectly
measured from summation of FRC and ERV and cannot be measured by spirometry.

Alveoli are small airbags present in the lungs. These are the site of the gas exchange. The oxygen and carbon dioxide gas are separated from the blood by alveolar epithelium and capillary
endothelium.

Emphysema is a long-term, progressive disease of the lungs that primarily causes shortness of breath due to over- inflation of the alveoli.
Pneumonia usually starts when one breathes the germ into their lungs. One is more likely to get the disease after having a cold or the flu.

210 times greater
Carbon monoxide has 210 times greater affinity for hemoglobin than oxygen1.

Rising CO2 mainly stimulates the respiratory center of the brain and
increase the inspiratory and expiratory signals to the respiratory muscles.

Expiration:
1. The exit of air (CO2) from the lungs is called expiration or exhalation.
2. It involves:
∙ Relaxation of the muscles of the diaphragm, As a result, the diaphragm moves upwards & resumes dome shape.
∙ Contraction of internal intercostal muscles and relaxation of external intercostal muscles. As a result, the ribs move inward & backwards i.e. posterior — the dorsal movement of the ribs. The above changes in the factors cause a decrease in the thoracic volume but the thoracic pressure is increased. Hence, due to increased pressure air comes out of the lungs.

The sinus node continuously generates electrical impulses, thereby setting the normal rhythm and rate in a healthy heart. Hence, the SA node is referred to as the natural pacemaker of the
heart.

Bundle of His is a muscle fibre that carries electrical impulses to the ventricles. It is distributed only through walls of ventricles only.

Your mitral valve is one of four valves in your heart. It’s located between the upper left chamber of your heart (left atrium) and your lower left chamber (left ventricle). Your mitral valve opens
and closes to make sure blood flows in the correct direction.

The pulmonary artery conducts blood from the right ventricle to the lungs, where oxygen is loaded into it. This blood then returns to the left atrium through the pulmonary vein and is then pumped
by the left ventricle through the systemic circuit

At rest, the heart is in diastole for approximately 60% of the cardiac cycle. As heart rate increases, both systole and diastole decrease, but there is a proportionately greater decrease in
diastole. At a heart rate of 180 bpm, diastole would account for only about 30% of the cardiac cycle