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The Respiratory system (overview (Principal organs (nose, pharynx, larynx,…
The Respiratory system
Anatomy
Nose
Function: warms, cleanses and humidifies inhaled air, detects odor and resonating chamber to modify voice.
Nasal cavity: extends from the anterior (external) nares to posterior (internal) nares or choanae. The dilated chamber inside the ala nasi is the vestibule
The vestibule is lined with stratifies squamous epithelium and has guard hairs that block inhalation of large particles
Nasal septum divides nasal cavity into right and left chambers called nasal fossae. There is little open space in nasal fossa because its lateral wall gives rise to superior, middle and inferior conchae that project toward septum and occupy most of the fossa
Conchae consists of mucous membranes supported by thin scroll - like turbinate bones. Beneath each concha are narrow air passages (meatus). The narrowness of the passage and turbulence of conchae make sure air contacts the mucous membrane on its way through enagling the nose to cleanse, warm and humidify it.
cilia of the respiratory epithelium beat and drive debris - laden mucus toward the posterior nares to the pharynx and down the oesophagus
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Larynx- cartilaginous chamber. Primary function: keep food and drink out of the airway and additional role of producing sound
Glottis: superior opening, guarded by a flap of tissue called epiglottis. During swallowing, extrinsic muscles of larynx pull it upward to the glottis and epiglottis directs food and drink into esophagus
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Walls of larynx are muscular: deep intrinsic muscles operate vocal cords and superficial extrinsic muscles connect larynx to hyoid bone and elevate larynx during swallowing
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overview
Principal organs
nose, pharynx, larynx, trachea, bronchi and lungs
These organs serve to draw in air, exchange gases with blood and expel the modified air
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Anatomy
Trachea - rigid tube, 12cm, C - shaped cartilage rings to keep it from collapsing during inhalation
Trachea and larynx lined with pseudostratified epithelium, provides mucociliary escalator for removal of debris trapped in the mucus
Lungs, Bronchial tree and Alveoli
Each lung is a conical organ, with the broad concave base resting on the diaphragm. Lung received the bronchus, blood and lymphatic vessels, and nerves through its hilum Left lung (3 lobes) and right lung (2 lobes)
Bronchial tree: highly branched air tubes. Primary > Secondary > Tertiary > bronchopulmonary segment. Tertiary bronchi give rise to bronchioles (lack cartillage but contain smooth muscle). Each bronchiole divides into 50-8- terminal bronchioles. Each terminal bronchioles gives off smaller respiratory bronchioles that divide into alveolar ducts ending in alveolar sacs
Alveoli: contains squamous alveolar cells (thin cells for rapid gas diffusion). Alveolar macrophages (dust cells) that are last line of defense against inhaled matter. Each alveolus is surrounded with a basket of capillaries. Respiratory membrane is made up of the wall of the alveolus, endothelial wall of the capillary and fused basement membranes.
Pulmonary circulation has a very low blood pressure to prevent the alveoli from filling with fluid. The osmotic uptake of water overrides filtration and keeps alveoli dry.
Pleurae
A surface of each lung is covered by visceral pleura. The chest cavity is lined with parietal pleura. between the two is the space of the pleural cavity containing pleural fluid.
The pleura and pleural fluid serve to reduce friction during chest expansion, to create a pressure gradient, and for compartmentalisation (to prevent infections)