Respiratory System of Rat

Anatomy of Earthworm,Cockroach & Frog of Class 11

  • Rat respire with the lungs only, located in thoracic cavity. Respiratory system includes the respiratory tract and respiratory organ (lungs)
  • Nose is located at the tip of the snout and bear two large openings — external nares or nostrils which appear connected with mouth due to ‘harelip’ cleft of upper lip.
  • Nasal passage is partitioned into 2 nasal cavities by nasal septum and open internally by internal nares or choanae. Each nasal cavity consists of three parts — nasal chamber or vestibule, respiratory region and olfactory organ.
  • Vestibular part has hair, sebaceous gland and sweat gland to filter incoming air. Respiratory part has scroll-like projections or conchae to increase surface area and is lined by respiratory epithelium.
  • Olfactory region is lined by olfactory epithelium or schneiderian membrane for olfaction or sense of smell. Choanae open into pharynx which opens into the windpipe.
  • Wind pipe is made up of anterior small chamber larynx or the voice box and a long, thin tube-like trachea behind. Trachea is supported by a series of C-shaped hyaline cartilage bands.
  • Lungs are soft, elastic structures, each surrounded by its pleural cavity. Within the lung, bronchi undergo extensive branching and rebranching, ultimately resulting in formation of a large number of lobules or alveoli which form sponging mass.
  • Normal inspiration in rat is brought about by contraction of diaphragm (becoming flat) and external intercostal muscles (pulling the ribs and sternum outwards and forwards). The chest expands, lungs get stretched and distention of alveoli occurs therefore, air is sucked into alveoli.
  • The relaxation of same muscle move the chest to its normal position, moving the air out, causing expiration.
  • Abdominal muscles and internal intercostal muscles are involved in forceful expiration.
  • Blood is involved in the transport of gases. Oxygen is transported in the form of oxyhemoglobin in RBCs or dissolved in plasma (less than 2%).
  • CO2 is transported in the form of bicarbonates (70%), carbamino-Hb (23%) or dissolved in plasma (7%).
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