· Only Aerial respiration takes place by the lungs.
· Respiratory Tract:
· It consists of the following organs:
1. External nares:
· These are located near the fleshy tip of the snout as a pair of small openings for drawing air from the atmosphere.
· It consists of the following organs:
1. External nares:
· These are located near the fleshy tip of the snout as a pair of small openings for drawing air from the atmosphere.
2. Nasal chamber or olfactory chamber:
· Two nasal chambers are separated from the buccal cavity by the hard palate and also separated by the bony nasal septum.
· Internal surface of each nasal chamber is increased greatly by scroll-like turbinal bones.
· Function:
· Nasal chambers are lined by vascular mucous epithelium and sensory epithelium which serve as a sensory organ of smell or olfaction as well as filler the dust or act as an air conditioner (air becomes moist and warm here)
· It opens posteriorly into the pharynx through internal nares.
3. Internal nares: They open into the nasopharynx those present dorsally on the soft palate.
4. Pharynx: It opens into the larynx through the glottis.
5. Larynx:
· It serves as a sound-producing organ or voice box.
· It is composed of 4 pieces of cartilages: Thyroid, Cricoid and Paired Arytenoid Cartilage.
· A nodule like cartilage of Santorini is attached at arytenoids cartilage.
· Vocal cords are present which are a pair of membranous folds that extends dorsolaterally in the laryngeal chamber from arytenoid to thyroid cartilage.
· These are developed from the lateral wall of the larynx and consists of elastic connective tissue covered by mucous membrane.
· It is related to sound production or phonation.
· Glottis is the opening present between inner free edges of the vocal cords.
· In normal resting condition the vocal cord lie apart at an acute angle so that glottis is opened to allow the passage of respiratory air whereas at the sound production stage these vocal cords are closed together and vibrate when air rushes out from the narrowed slit-like glottis under pressure from the lungs.
· Note: True vocal cords are absent in Hippopotamus.
· Slurring sound in the cat is due to vibration of false vocal cords.
· It serves as a sound-producing organ or voice box.
· It is composed of 4 pieces of cartilages: Thyroid, Cricoid and Paired Arytenoid Cartilage.
· A nodule like cartilage of Santorini is attached at arytenoids cartilage.
· Vocal cords are present which are a pair of membranous folds that extends dorsolaterally in the laryngeal chamber from arytenoid to thyroid cartilage.
· These are developed from the lateral wall of the larynx and consists of elastic connective tissue covered by mucous membrane.
· It is related to sound production or phonation.
· Glottis is the opening present between inner free edges of the vocal cords.
· In normal resting condition the vocal cord lie apart at an acute angle so that glottis is opened to allow the passage of respiratory air whereas at the sound production stage these vocal cords are closed together and vibrate when air rushes out from the narrowed slit-like glottis under pressure from the lungs.
· Note: True vocal cords are absent in Hippopotamus.
· Slurring sound in the cat is due to vibration of false vocal cords.
6. Trachea or windpipe
· It starts from the glottis and runs parallel with the oesophagus through the neck and bifurcates in the thorax as bronchi near the heart.
· It is formed by a series of C-shaped cartilages which prevent collapsing and provide flexibility.
· Trachea is divided into right and left bronchi at the level of 4 or 5 thoracic vertebrate
· Last C- shaped cartilage where the trachea is divided into 2 bronchi is called Carina.
· These are internally lined with ciliated mucous epithelium.
· Mucous keeps the surface moist and slimy and holds bacteria and dust particles swept towards the pharynx.
· Trachea, bronchi and bronchioles are internally lined by ciliated mucus epithelium.
· Trachea, bronchi and bronchioles are internally lined by ciliated mucus epithelium.
7. Bronchi, Bronchioles, Alveolar ducts, Alveolar sacs, Alveoli
· Trachea divides into right and left bronchi
· Bronchi divide into bronchioles which in turn are divided into alveolar ducts. Alveolar ducts divide into atria which terminates into alveoli.
8. Lungs:
· They are located on either side of the heart and occupy most of the thoracic cavity called the pleural cavity.
· Lungs are surrounded by pleural membranes.
· They are located on either side of the heart and occupy most of the thoracic cavity called the pleural cavity.
· Lungs are surrounded by pleural membranes.
· The outer pleural membrane is called a parietal pleural membrane and inner visceral (pulmonary) pleural membrane. In between them, pleural fluid is present.
Structure of Lungs
· The lungs are spongy light and pink coloured respiratory organs which are divided into following lobes:
· The lungs are spongy light and pink coloured respiratory organs which are divided into following lobes:
· After entering the lungs, the primary bronchus divides into smaller secondary and tertiary bronchi.
· Then into terminal bronchi which are again divided into alveolar ducts and finally terminate into delicate blind air sac or infundibula.
· The wall of air sac is evaginated to form tiny sacculations called alveoli.
· Alveolus is the structural and functional unit of lungs where gaseous exchange occurs through diffusion.
· Alveolus is the structural and functional unit of lungs where gaseous exchange occurs through diffusion.
Mechanism of Respiration
A. Inspiration
· It is an active process in which atmospheric air is inhaled into the lungs.
· Contraction (flattening) of the radial muscle of the diaphragm increases the length of the thoracic cavity and contraction of obliquely arranged external intercoastal muscle help the rib cage to move upward and outward.
· So that volume of the thoracic cavity is increased and pressure is decrease than the atmospheric pressure.
· Now Atmospheric Oxygen enters into lungs till the pressure inside the lungs becomes equal to that of the air outside.
· Oxygen is transported to tissue for biological oxidation in the form of oxyhaemoglobin by blood and Carbon dioxide carries back to alveoli by blood in the form of carboxyhaemoglobin.
· Oxygen is transported to tissue for biological oxidation in the form of oxyhaemoglobin by blood and Carbon dioxide carries back to alveoli by blood in the form of carboxyhaemoglobin.
B. Expiration
· It is a passive process in which Carbon dioxide is released out into the atmosphere from the lungs.
· Relaxes the diaphragm to regain normal dome-shaped position.
· It is a passive process in which Carbon dioxide is released out into the atmosphere from the lungs.
· Relaxes the diaphragm to regain normal dome-shaped position.
· Meanwhile, Internal intercostal muscles contract to the lower rib cage.
· So the volume of the thoracic cavity is decreased and increases air pressure to expel air or Carbon dioxide in the atmosphere.
· Alveoli of mammals are less efficient than birds because the lungs of mammals never become empty after each expiration due to residual air which mixes with the fresh air after every inspiration.
· Respiratory rate in rabbits is 36/min.
· Respiration is controlled by respiratory centres i.e. Pons and Medulla Oblongata.
· Alveoli of mammals are less efficient than birds because the lungs of mammals never become empty after each expiration due to residual air which mixes with the fresh air after every inspiration.
· Respiratory rate in rabbits is 36/min.
· Respiration is controlled by respiratory centres i.e. Pons and Medulla Oblongata.
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