Cellular respiration requires oxygen and produces carbon dioxide. Oxygen must be dissolved in water before animals can take it up. Therefore, the lung surface must always be moist. The surface area of a human lung is 60 to 80 sq. meters.
- Nasal cavity : hair and cilia filter dust and particles. The air in the nasal cavity gets warmed and moistened before it enters the lungs.
- Pharynx : from the nasal cavity the air enters the pharynx. It serves as a common passage for both air and food. The glottis is protected against the entrance of food by a triangular flap of tissue, the epiglottis.
- Larynx(voice box) : it is the first part of trachea present in the neck. When air is forced into the larynx, the vocal cords present in it vibrate and sound is produced.
- Trachea : it is a four and a half inch long tube with c shaped ring of cartilage in its walls. The trachea branches into two bronchi on to each lung and these branches within the lung into many small bronchioles.
- Lungs : surrounding each lung is a double walled sac, the pleural cavity. Hence, the covering of lungs is called pleural membrane.
- The right lung is divided into two lobes and left into two.
- The left lung is smaller than the right and has a concavity, the cardiac notch, where the heart lies.
- Inside the lung each bronchi divides into numerous bronchioles, each of which terminates into an elongated saccule, the alveolar duct, which bears on its surface air sac or alveoli.
- Gas exchange occurs in alveoli.
- Hemoglobin is a protein that carries oxygen and is found in the blood of most animals. 95% of the oxygen is transported by hemoglobin, 5% in blood plasma.
- Cigarette smoke kills phagocytic cells in respiratory epithelium.
- 7% of carbon dioxide is transported as dissolved in plasma, 23% as carbaminohemoglobin and 70% as bicarbonates.
Respiratory Organs Of Animals
Lungs – reptiles and mammals
Skin – frog,earthworms and leeches
Gills – fishes, tadpoles and prawns
Trachea – Insects, centipedes and millipedes
Body surface – protozoans, porifera and coelenterates
Book lungs – spider, scorpion, ticks and mites
Mental – lungfish, bony fishes
Book gills – king crab, prawns and Crayfish daphnia
Birds – Air sacs lungs
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