Transport of Respiratory Gases:

• The transport of respiratory gases, specifically oxygen (O2) and carbon dioxide (CO2), between the lungs and the tissues of the body is a crucial physiological process.

• This transport is essential for cellular respiration, which is the process by which cells produce energy.

Oxygen Transport

1. Oxygen Uptake in the Lungs:

• Oxygen is inhaled into the lungs, where it diffuses across the alveolar-capillary membrane into the blood.

2. Binding with Hemoglobin:

• In the blood, oxygen binds to hemoglobin, a protein found in red blood cells.

• Hemoglobin can carry up to four oxygen molecules at a time. This oxygen-hemoglobin complex is referred to as oxyhemoglobin.

3. Transport to Tissues:

• Oxygenated blood is then circulated through the body via the arteries and arterioles to the capillaries, where oxygen is released to the tissues.

4. Oxygen Release:

• The release of oxygen from hemoglobin is influenced by factors such as:

  • Oxygen and carbon dioxide concentrations in the blood.

  • Blood pH and temperature.

  • Presence of 2,3-bisphosphoglycerate (2,3-BPG), a molecule that reduces hemoglobin's affinity for oxygen, facilitating oxygen release to tissues.

Oxygen Transport

Carbon Dioxide Transport

Carbon Dioxide Transport

1. CO2 Production:

• Carbon dioxide is produced as a waste product of cellular respiration and must be removed from the body to maintain homeostasis.

2. Transport Forms:

CO2 is transported in the blood from the tissues to the lungs in three main forms:

1. Dissolved CO2: A small amount of CO2 is transported dissolved in the plasma.

2. Bicarbonate (HCO3-): The majority of CO2 is transported in the form of bicarbonate ions. CO2 reacts with water in the presence of the enzyme carbonic anhydrase, forming carbonic acid, which then dissociates into bicarbonate and hydrogen ions.

3. Carbaminohemoglobin: CO2 also binds directly to hemoglobin, but at a different site than oxygen, forming carbaminohemoglobin.

3. CO2 Release in the Lungs:

• When blood reaches the lungs, the processes that converted CO2 into bicarbonate and carbaminohemoglobin are reversed.

• CO2 is released from hemoglobin, converted back from bicarbonate to CO2 gas, and then exhaled.

Regulation of Gas Transport

• The transport and release of O2 and CO2 are finely regulated to meet the body's metabolic demands.

• Regulation involves changes in:

  • Blood flow

  • Hemoglobin's affinity for oxygen

  • The rate and depth of breathing

• These processes are controlled by neural and chemical mechanisms that adapt to changing conditions such as physical activity or oxygen availability.