Question

Explain in detail the mechanism of breathing.Discuss briefly about respiration and acid base balance. Discuss briefly about the structural layers of alimentary tube.

Answer 1

Mechanism of breathing:-

Breathing consists of two phases called inspiration and expiration.

Inspiration-In order for air to be drawn into the lungs during inspiration the volume of the thorax must increase. This is brought about due to the contraction of respiratory muscles. The diaphragm contracts and flattens and the intercostal muscles contract to pull the ribs up and out. The increased volume within the thoracic cavity lowers the pressure within the lungs with respect to the atmospheric pressure. Consequently, air is drawn into the lungs down a pressure gradient.

Expiration- The next step is expiration. The diaphragm relaxes and moves up and the relaxation of the intercostal muscles moves the ribs in and down. This has the effect of decreasing the volume within the thoracic cavity and increasing the pressure within the lungs with respect to atmospheric pressure. As a result, air moves out of the lungs down a pressure gradient.

Respiration and acid-base balance:-

Blood needs the right balance of acidic and basic (alkaline) compounds to function properly. This is called the acid-base balance. Our kidneys and lungs work to maintain the acid-base balance. When the levels of acid in our blood are too high, it’s called acidosis. When our blood is too alkaline, it is called alkalosis. Respiratory acidosis and alkalosis occur due to a problem with the lungs.

When we respire,our lungs remove excess carbon dioxide from our body. When they cannot do so(during hypoventilation),our blood and other fluids become too acidic and blood pH is reduced, this condition is known as Respiratory acidosis. Respiratory alkalosis is a medical condition in which increased respiration elevates the blood pH beyond the normal range (7.35–7.45) with a concurrent reduction in arterial levels of carbon dioxide.

Structural layers of alimentary tube:-

There are 4 layers to the alimentary canal that are made up of different tissue types. From inner most to outmost the order goes mucosa, submucosa, muscularis, and serosa. Mucosa - innermost, produces mucous which helps food move along and protects more delicate tissues from being digested. Submucosa-The submucosa is a dense, irregular layer of connective tissue with large blood vessels, lymphatics, and nerves that supports the mucosa.The absorbed elements that pass through the mucosa are picked up from the blood vessels of the submucosa. Muscularis- The muscularis is responsible for the segmental contractions and peristaltic movements in the gastrointestinal (GI) tract. Serosa- The serous layer provides a partition between the internal organs and the abdominal cavity.Serosa consists of a secretory epithelial layer and a thin connective tissue layer that reduce the friction from muscle movements.