Breathing and Exchange of Gases Test 63

Internal respiration refers to gas exchange across the respiratory membrane in the metabolizing tissues. External respiration refers to gas exchange across the respiratory membrane in the lungs. Pulmonary ventilation is the process by which oxygen enters and carbon dioxide exits the alveoli. Respiration is the process by which oxygen and carbon dioxide diffuse in and out of the blood. 

Experiments have shown that an average human being at rest inhales and exhales about 7 or 8 liters of air per minute. That totals to more than 11,000 liters of air in a day. Thus, the correct answer is option A.

As exercise intensifies and the body’s need for fresh oxygen increases, the ventilation rate responds accordingly. The metabolic byproducts of exercise build up as a result of cellular respiration, and the amount of carbon dioxide (CO$$_2$$) in the system also increases to act as a buffer against these acidic byproducts. As the concentration of CO$$_2$$ increases, the body responds by breathing deeper and more frequently to dispel the CO$$_2$$. Working muscles also require fresh oxygen. The rate of respiration also increases to facilitate the delivery of oxygen to the bloodstream, where it is then transported to the working muscles. The rate at which cellular respiration takes place (and hence oxygen is consumed) varies with the general state of activity of the body. Vigorous exercise may increase by 20 to 25 times the demands of the tissues for oxygen. This increased demand is met by increasing the rate and depth of breathing. 

Lung ventilation is the breathing process. Lung ventilation movement are due to the movements of coastal muscles and diaphragm. During inhalation, internal intercoastal muscles relax and external intercoastal muscles contract. This results in outward and upward movement of ribcage.  During inhalation, diaphragm contracts and moves downwards. During exhalation, external intercostal muscles relax and the internal intercostal muscles contract. This results in downward  and inward movement of ribcage. During inhalation, diaphragm relaxes and moves upwards.

The lungs which form the main respiratory system is a pair of spongy, air-filled organs which is located on either side of the chest in the rib cage. The inhaled air passes through the trachea (windpipe) into the lungs through its tubular branches known as bronchi which further divide into numerous smaller tubes known as the bronchioles. 

The thoracic diaphragm consists of the peripheral muscle and central tendon. The peripheral muscle is made up of many radial muscle fibers that originate on the ribs, sternum, and spine and  converge on the central tendon. On the basis of origin, the peripheral muscular part is separated into sternal, costal and lumbar. When we breathe, the diaphragm is drawn downward until it is flat. the thoracic cavity becomes deeper and larger, making more air space. when air is drawn into the lungs, the muscles in the diaphragm contract pulling the central tendon down. This process enlarges the thoracic cavity, and air then passes into the lungs to fill the larger space.

Carbon dioxide combines with water to form carbonic acid (H$$_2$$CO$$_3$$), which dissociates to give $$H^+$$ and HCO$$_3$$$$^-$$ and this reaction is catalyzed by the enzyme carbonic anhydrase. $$H^+$$, which are released contribute to lowering of pH.

Pulmonary ventilation is commonly referred to as breathing. It is the process of air flowing into the lungs during inspiration (inhalation) and out of the lungs during expiration (exhalation).

Swallowing or deglutition is the process that transfers the food taken in by the mouth move down to the pharynx and to the esophagus. However, swallowing is an important part of the food intake process in human beings, the body carries out an automatic temporary closing of the epiglottis which is controlled by the swallowing reflex. This protects the food, water or medicines from entering the trachea and prevents choking or pulmonary aspiration.

This respiratory surface, also known as the respiratory membrane, includes the alveolar epithelial cells as well as the pulmonary capillary endothelial cells. The respiratory membrane consists of the alveolar and capillary walls. Gas exchange occurs across this membrane and is diffusion of oxygen into and carbon dioxide out of the blood.