Question

1- Describe how the body transports CO2 in the blood.

2- Describe the role of haemoglobin in oxygen transport and the factors that affect its affinity for oxygen.

3- Give a short description of the lung volumes that can be measured with a spirometer.

Answer 1

Answer:

Answer 1. Carbon dioxide is one of the gas which remains produced within the human body due to the intense metabolic activities performed and it the moves out of the body to the atmosphere through the breathing pathway. CO2 is more soluble in the blood as compared to that of oxygen and the body has three mechanisms for its transportation. They are as given below;

a) In the dissolved state: nearly 7 % of the total carbon dioxide gets dissolved in the blood plasma and likewise gets transported to the different parts of the body

b) In the form of bicarbonate ions: majority of the cO2 (nearly 70%) gets transported to the different body parts in the form of bicarbonate ions. The underlying mechanism is as given below;

On the surface of the RBC; there is an enzyme named carbonic anhydrase. Carbon dioxide combines with water to form carbonic acid in the presence of the enzyme CA (carbonic anhydrase). However the carbonic acid is a weak acid and it immediately dissociates to form bicarbonate ions and H+ ions. The bicarbonate ions diffuse into the plasma of the blood from the RBC and in exchange the chloride ions get diffused inwards. This process is called as chloride shift and thus it leads to the transportation of the CO2 to the different body parts

c) In the form of carbaminoglobin: nearly 23% of the total CO2 gets bound with the amino group of the hemoglobin leading to the formation of the carbaminoglobin and thus results in the transportation of the CO2 to the different body parts

Thus, these are the different mechanisms for the transportation of the CO2 amongst the different body parts.

Answer 2. Role of hemoglobin in the oxygen transportation

Hemoglobin is a pigment protein which is present within the RBC of the blood. The pigment is having a very high binding efficiency for oxygen and one Hb molecule at a time can bind with 4 molecules of oxygen.

Nearly 97% of the total oxygen within the body gets transported by combining with hemoglobin and remaining 3 % gets bound with the plasma to facilitate their transportation.

Oxygen binds with hemoglobin within the lungs for its transportation to the distant body tissues and the product formed is called as oxyhemoglobin. It gets formed as within the lungs the partial pressure of oxygen is higher as compared to that of the Co2. So oxygen becomes successful in replacing the CO2 and thus gets bound.

However, within the body tissues oxyhemoglobin thus formed would need to get dissociated for the delivery of oxygen amongst the body cells. For this certain conditions needs to be prevalent thus favoring the process of oxyhemoglobin dissociation and this effect is called as Bohr’s effect.

The different factors favoring the oxyhemoglobin dissociation within the body tissues are;

a) High temperature due to metabolism

b) High concentration of CO2 due to tissue metabolism

c) High H+ concentration

d) High concentration of 2,3 BPG

e) Less concentration of oxygen within the body cells

All these processes thus lead to the dissociation of the oxyhemoglobin thus facilitating the oxygen delivery within the body cells.

Answer 3. Lung volumes are the respiratory volumes and they represent the total amount of the oxygen or the gas present within the lungs at a given period of time. They can be measured by the use of a device; spirometer and also they give us an idea regarding the assessment of the proper and effective functioning of the lungs.

The different respiratory volumes are the tidal volume, IRV, ERV, and the RV.

Tidal volume (TV): It represents the total volume of the air that can be inspired or expired during the normal breathing and its value is 500 ml

Inspiratory reserve volume (IRV): It is the maximum amount of air that can be inhaled after a forceful inspiration. Its value is 2500-3000 ml

Expiratory reserve volume (ERV): It is the maximum amount of air a person can expire after a forceful exhalation. Its value is 1000-1100 ml

Residual Volume (RV): It is the volume of the air which remains within the lungs after a forceful expiration. Its value is around 1100-1200 ml. It is due to the RV only that an individual does not die immediately during oxygen deficient conditions.

Thus, these were the pulmonary volumes which gets operated within the human lungs, can be assessed by a spirometer and they give us a clinical assessment on the functioning of the lungs.