A site for medical students - Practical,Theory,Osce Notes


Normal process of respiration, Oxygen uptake in the blood and elimination of CO2 from the body

Respiration is the process by which living organisms take in oxygen from the environment and release carbon dioxide. In humans, respiration involves two main processes: external respiration and internal respiration.

External respiration occurs in the lungs and involves the exchange of gases between the air in the lungs and the bloodstream. When we inhale, air enters the respiratory system and reaches the alveoli, which are tiny air sacs in the lungs. The alveoli are surrounded by a network of capillaries, where the exchange of gases takes place.

Oxygen (O2) from the inhaled air diffuses across the thin walls of the alveoli and enters the bloodstream. It binds to hemoglobin, a protein in red blood cells, forming oxyhemoglobin. This oxygenated blood is then transported to the body's tissues.

Internal respiration occurs at the tissue level, where oxygen is delivered to cells and carbon dioxide (CO2) is produced as a waste product of cellular metabolism. In the tissues, oxygen detaches from hemoglobin and diffuses into the cells, where it is used in the process of cellular respiration to produce energy.

During cellular respiration, glucose and oxygen react to produce carbon dioxide, water, and energy in the form of adenosine triphosphate (ATP). The carbon dioxide generated as a byproduct diffuses out of the cells into the surrounding capillaries.

The oxygen-depleted blood returns to the heart and is pumped to the lungs through the pulmonary artery. In the lungs, carbon dioxide diffuses from the capillaries into the alveoli, and it is then exhaled out of the body during the process of exhalation.

Oxygen uptake in the blood is facilitated by the high affinity of hemoglobin for oxygen. Hemoglobin binds to oxygen in the lungs, and this binding is reversible, allowing for oxygen to be released in the tissues where it is needed. The oxygen-carrying capacity of blood is influenced by factors such as hemoglobin concentration, blood pH, temperature, and partial pressure of oxygen.

The elimination of carbon dioxide occurs through the lungs during exhalation. Carbon dioxide in the bloodstream combines with water to form carbonic acid (H2CO3), which quickly dissociates into bicarbonate ions (HCO3-) and hydrogen ions (H+). The bicarbonate ions are transported back to the lungs through the bloodstream, where they are converted back into carbon dioxide, which is then exhaled.

Hypoxia refers to a condition in which the body or a region of the body is deprived of adequate oxygen supply. There are various forms of hypoxia, including:

  1. Hypoxic hypoxia: This occurs when there is a decrease in the oxygen concentration in the air, such as at high altitudes or in poorly ventilated environments.
  2. Anemic hypoxia: It results from a decrease in the oxygen-carrying capacity of blood due to a decrease in the number of red blood cells or a decrease in the amount of hemoglobin.
  3. Ischemic hypoxia: It happens when there is a reduction in blood flow to tissues, leading to inadequate oxygen supply. It can be caused by conditions such as circulatory disorders or blockages in blood vessels.
  4. Histotoxic hypoxia: This occurs when the cells are unable to utilize oxygen effectively due to the presence of toxins or metabolic poisons, impairing cellular respiration.
  5. Hypoxemic hypoxia: It results from a decrease in the oxygen content of the blood, usually caused by respiratory disorders, such as lung diseases or impaired gas exchange in the lungs.

These forms of hypoxia can have varying degrees of severity and can lead to symptoms ranging from mild breathlessness and fatigue to more severe complications affecting vital organs. Prompt medical attention and appropriate interventions are necessary to address hypoxic conditions and restore oxygen supply to the body's tissues.