Respiration and Gas Transport

Each body cell releases carbon dioxide into nearby capillaries by diffusion, because the level of carbon dioxide is higher in the body cells than in the blood. In the capillaries, some of the carbon dioxide is dissolved in plasma and some is taken by the haemoglobin, but most enters the red blood cells where it binds with water to form carbonic acid.

Blood is sometimes considered to be a fluid connective tissue because of the mesenchymal origin of its cells and a low ratio of cells to liquid intercellular substance, the blood plasma.

Respiration is the biological process of gas exchange - oxygen enters tissues and carbon dioxide is removed through blood circulation. Excretion removes waste, perspiration cools the body through sweat.

Hemoglobin is the iron-containing pigment in red blood cells that transports oxygen from the lungs to body tissues and carries carbon dioxide back to the lungs. It gives blood its red color and is essential for respiration.

CO combines with haemoglobin to form carboxyhaemoglobin.

Sickle cell disease (sickle cell anemia) causes red blood cells to assume a sickle shape due to abnormal hemoglobin S. These misshapen, rigid cells have reduced oxygen-carrying capacity and block blood vessels, causing tissue hypoxia. Hemophilia impairs clotting, thrombocytopenia reduces platelet count, and 'blood transfusion' is a procedure, not a disease.

Mammalian erythrocytes are non-nucleated cells in their mature form. They have nuclei during early phases of erythropoiesis, but extrude them during development as they mature in order to provide more space for haemoglobin. The colour of erythrocytes is due to the heme group of haemoglobin.

Hemoglobin has the highest affinity for carbon monoxide (CO), binding it approximately 200-250 times more strongly than oxygen. This is why CO poisoning is so dangerous - it displaces oxygen from hemoglobin and prevents oxygen transport to tissues.

CO₂ is the cellular waste that needs to be excreted out by the cell. It accumulates in high concentrations inside the cell. In the cell’s external environment, the concentration of CO₂ is low as compared to that inside the cell. As soon as there is a difference of concentration of CO₂ inside and outside a cell, CO₂ moves out of the cell, from a region of high concentration to a region of low concentration outside the cell by the process of diffusion. Thus, this is the correct answer.  

The Hamburger phenomenon (or Hamburger shift) refers to the chloride shift in red blood cells during CO2 transport. When CO2 enters blood, bicarbonate ions move out and chloride ions move in to maintain electrical neutrality, facilitating CO2 transport from tissues to lungs.

Wintrobe's method is used for ESR and hematocrit determination, not hemoglobin estimation. Drabkin's method converts hemoglobin to cyanmethemoglobin for colorimetric measurement, Sahli's method uses acid hematin formation, and spectrometry directly measures hemoglobin's light absorption.

Wintrobe's method is used for determining erythrocyte sedimentation rate (ESR) and packed cell volume (hematocrit), not for hemoglobin estimation. Hemoglobin is measured by Drabkin's method (cyanmethemoglobin), Sahli's method (acid hematin), or by spectrophotometry/spectrometry methods.

Ketamine is unique among anesthetic agents in that it increases cerebral metabolic rate of oxygen (CMRO2) and cerebral blood flow. This occurs because ketamine is a dissociative anesthetic that maintains or even stimulates cerebral activity, unlike most other anesthetics which depress cerebral metabolism. Propofol significantly decreases CMRO2 and is used for neuroprotection. Atracurium is a neuromuscular blocker with minimal direct cerebral effects. Fentanyl is an opioid that also decreases CMRO2.

The binding of oxygen to one haemoglobin sub-unit induces conformational changes that are relayed to the other sub-units.