Test: Breathing and Exchange of Gases & Body Fluids and Circulation (August 26) - NEET MCQ

In the alveoli, where there is high pO₂, low pCO₂, lesser H⁺ concentration and lower temperature, the factors are all favourable for the formation of oxyhaemoglobin, whereas in the tissues, where low pO₂, high pCO₂, high H⁺ concentration and higher temperature exist, the conditions are favourable for dissociation of oxygen from the oxyhaemoglobin.

Expiratory capacity is the total volume of air a person can expire after normal inspiration. It includes tidal volume and expiratory reserve volume.
EC = TV + ERV = 500 + 1000 = 1500 mL

The very thin alveolar wall (about 0.0001 mm) is composed of moist, nonciliated, squamous epithelial cells.

It is the relationship between the percentage saturation of haemoglobin (by volume) in the blood and the oxygen tension (in partial tension) PO₂ of the blood.
It is usually a sigmoid plot. Haemoglobin molecules can bind up to four oxygen molecules in a reversible way. The shape of the curve results from the interaction of bound oxygen molecules with incoming molecules. The binding of the first molecule is difficult. However, this facilitates the binding of the second and third molecules, and it is only when the fourth molecule is to be bound that the difficulty increases, partly as a result of crowding of the haemoglobin molecule, partly as a natural tendency of oxygen to dissociate.

The O₂-Hb dissociation curve is a sigmoidal curve that represents the relationship between O₂ concentration and the percentage saturation of Hb. As the concentration increases from about 90% there is a significant plateau in the curve, which has several important biological repercussions.

Carbon dioxide is transported via blood to lungs mostly as carbaminohaemoglobin and carbonic acid. It is released in lungs in exchange with oxygen.

The total volume of air that can be expelled from the lungs after maximum inspiration and then expiring to the maximum is known as the vital capacity. The volume of air that remains inside lungs at the end of maximum forceful expiration is the residual volume. Expiratory reserve volume is the maximum extra volume of air that can be expired by forceful expiration after a normal tidal expiration. Total lung capacity is the maximum volume of air that can be contained in the lungs after maximum inspiration.

Gaseous exchange between blood (dissolved phase) and alveolar air (gaseous phase) across respiratory membrane occurs by simple diffusion. Obviously, it depends upon the concentration gradient (=partial pressure) of the concerned gases in blood and alveolar air.

Fibrins are formed by the conversion of inactive fibrinogens in the plasma by the enzyme thrombin.

Stroke volume = End diastolic volume - End systolic volume
= 100 - 50 = 50 mL
Cardiac output = Heart beat x stroke volume
∴ Heart beat = Cardiac output/Stroke volume = 5000 / 50 = 100 beats per minute

B-lymphocytes cells are involved in antibody production.

70% to 75% CO₂ is transported as primary buffer of the blood. Bicarbonate ion (HCO₃) in blood plasma. When CO₂ diffuses from tissues into blood then it is acted upon by the enzyme carbonic anhydrase.

Arteries are best defined as the vessels which break up into capillaries which reunite to form a vein.
Arteries are the blood vessels which carry oxygenated blood from the heart to the organs. It breaks up into several branches of capillaries before entering the organs. These capillaries again reunite to form venules and ultimately veins which carry the deoxygenated blood towards the heart. 

In the given figure the exchange of respiratory gases occurs in alveolar cavity.

The pulmonary alveoli are the terminal ends of the respiratory tree, which are the gas exchange sites. The alveolar membrane is the gas exchange surface. Carbon dioxide rich blood is pumped from the rest of the body into the alveolar blood vessels where, through diffusion, it releases its carbon dioxide and absorbs oxygen.

In a standard ECG, the P-wave is a small upward wave that indicates the depolarisation of the atria. This is caused by the activation of SA node.

The ABO blood group system is the most important blood type system (or blood group system) in human blood transfusion. It is named ABO and not ABC, because blood group O (or blood group zero in some countries) individuals do not have either A or B antigens on the surface of their RBCs, but their blood serum contains IgM anti-A antibodies and anti-B antibodies against the A and B blood group antigens. Therefore, a group O  individual can receive blood only from a group O individual, but can donate blood to individuals of any ABO blood group (ie A, B, O or AB).