Tag: zoology

Cutaneous respiration or cutaneous gas exchange, is a form of respiration in which gas exchange occurs across the skin or outer integument of an organism rather than gills or lungs. Cutaneous respiration may be the sole method of gas exchange, or may accompany other forms, such as ventilation. Cutaneous respiration occurs in a wide variety of organisms, including insects, amphibians, fish, sea snakes, turtles, and to a lesser extent in mammals, including humans. 

Gas exchange and respiration are essential if cells are to stay active, grow and divide. All the structures for gas exchange have common as follows:

• They have a large surface area relative to the volume of the organism. 
  
• They are thin and so have a short diffusion pathway. 
  
• They have a moist surface where gases can dissolve first before they diffuse in or out. 
  
• They are able to maintain the diffusion gradient down which the gases can diffuse.
  

Nicotinamide adenine dinucleotide phosphate, abbreviated NADP is a cofactor used in anabolic reactions, such as lipid and nucleic acid synthesis, which require NADPH as a reducing agent.

Respiration can be cellular and physiological. Cellular respiration takes place in individual cells while physiological respiration is a bulk process. Cellular respiration takes place through a set of metabolic reactions and in the cells which converts biochemical energy from the nutrients into ATP and releases wastes. These reactions are catabolic reactions that releases energy and heat in the process.

The end product of glycolysis is pyruvic acid. The next step is the formation of acetyl coenzyme A (acetyl CoA). Acetyl CoA is the initiator of the citric acid cycle. In carbohydrate metabolism, acetyl CoA is the link between glycolysis and the citric acid cycle. The initiating step of the citric acid cycle occurs when a four-carbon compound (oxaloacetic acid) condenses with acetyl CoA (2 carbons) to form a citric acid (6 carbons).

• Relaxation of the diaphragm and the inter-costal muscles returns the diaphragm and sternum and ribs move into their normal positions and reduce the thoracic volume and thereby the pulmonary volume. 
  
• This leads to an increase in intra-pulmonary pressure to slightly above the atmospheric pressure causing the expulsion of air from the lungs, i.e., expiration. Hence, ribs move out in during exhalation.

Breathing is an act of ventilating a respiratory surface with air. Breathing is usually accomplished through muscular movements that can be divided into inspiration (intake of air ) and expiration (outflow of air). The composition of inhaled air is 20.94 % oxygen, 0.04 % carbon dioxide, 79.02 % nitrogen and trace gases. The composition of exhaled air is 16.49 % oxygen, 4.49 % carbon dioxide, 79.02 % nitrogen and other trace gases. The nitrogen is an inert gas, during breathing, there is no change in nitrogen percentage in inhaled as compared to exhaled air.