Tag: zoology

During inspiration, the diaphragm contracts and moves downward and when the diaphragm relaxes it becomes dome shaped and moves upward during expiration. 

Nasal cavity opens to outside through external nares or nostrils. Nasal cavity occurs between palate and cranium. Nasal cavity is divisible into two nasal chambers by a nasal septum. Each nasal chamber has three parts - (a) Vestibule- It has hairs to filter out the dust particles, (b) Conditioner - respiratory region. It has bony projections and sinuses. It is abundant in blood capillaries, (c) Olfactory region- perceives sense of smell. The two nasal cavities condition the air to be received by the other areas of the respiratory tract.

During quiet breathing, there is little or no muscle contraction/relaxation involved in expiration. This process is simply driven by the elastic recoil of the lungs in healthy individuals. In certain conditions the elasticity of the lung can be lost, such as in emphysema. Forced or active expiration occurs in such individuals as well as occurring during exercise. The abdominal muscles and the internal and innermost intercostal muscles help expel air.

Coughing is an airway reflex mediated by airway receptors, that react to either pressure or chemical stimuli. The function of coughing is to assist the removal of material from the airways. This material may have been inhaled or produced in the airways. Coughing also prevents additional inhalation of material, or movement of inhaled material into the peripheral airways. Once material comes in contact with ciliated epithelium, it is transported by ciliary beating towards the trachea, where there is the highest density of cough receptors. Coughing then propels the material into the oropharynx, where it is swallowed. Coughing is an extremely important protective mechanism for the respiratory system.

Respiration is the process by which oxygen and carbon dioxide diffuse in and out of the blood. Respiration is also referred to as gas exchange, and it occurs in two areas of the body. External respiration refers to gas exchange across the respiratory membrane in the lungs. Internal respiration refers to gas exchange across the respiratory membrane in the metabolizing tissues, like your skeletal muscles. Expiration and inspiration are not the related terms of respiration. Thus, option C is correct.

Inhalation involves a contraction of the muscles, an increase in the size or volume of thoracic cavity, an expansion of the lungs with a drop of pressure inside them and entrance of atmospheric air into lungs through the air passages. Thus during inspiration the lungs act as suction pump. Inhalation is followed by exhalation, which is effected by the contraction of the lungs.

The diaphragm, located below the lungs, is the major muscle of respiration. It is a large, dome-shaped muscle that contracts rhythmically and continuously, and most of the time, involuntarily. Upon inhalation, the diaphragm contracts and flattens and the chest cavity enlarges. This contraction creates a vacuum, which pulls air into the lungs. Upon exhalation, the diaphragm relaxes and returns to its dome like shape, and air is forced out of the lungs. Thus, option B is correct. 

External respiration occurs in the lungs where oxygen diffuses into the blood and carbon dioxide diffuses into the alveolar air. Internal respiration occurs in the metabolizing tissues, where oxygen diffuses out of the blood and carbon dioxide diffuses out of the cells. Inspiration and expirations are breath in and breath out processes. 

Inhaled air contains more oxygen used to create energy and less CO$ _2$. It contains 21% O$ _2$, 0.04% CO$ _2$ and 79% Nitrogen. Exhaled air contains 16% O$ _2$, 4% CO$ _2$ and 79% Nitrogen. Thus, option C is correct.