Organs of the Respiratory System

Introduction Respiration ▫ Entire process of gas exchange between the atmosphere and body cells ▫ Includes:  1. movement of air in and out the lungs (breathing or ventilation)  2. gas exchange between blood and air in the lungs  3. gas transport in blood between lungs and body cells  4. gas exchange between blood and body cells

Upper Respiratory Tract Nose Nasal cavity Paranasal sinuses Pharynx

Nose Bone and cartilage support it internally 2 nostrils = openings for air to enter and leave Internal hairs for protection

Nasal Cavity Hollow space behind nose Nasal septum divides cavity into right and left portions Nasal conchae = bones that curl out from lateral walls of cavity and divide the cavity into passageways (figure 16.2) Mucous membranes line cavity ▫ Temperature regulation ▫ Moistens and protects

Paranasal Sinuses Air-filled spaces within the maxillary, frontal, ethmoid and sphenoid bones of the skull and opening into the nasal cavity Mucous membranes line the sinuses Reduce the weight of the skull Affect quality of the voice

Pharynx Behind the oral cavity and between the nasal cavity and larynx Passageway for food ▫ Oral cavity to esophagus Passageway for air ▫ Between nasal cavity and larynx Helps produce sounds of speech 3 parts: naso-, oro- and laryngo-

Lower Respiratory Tract Larynx Trachea Bronchial tree Lungs

Larynx Enlargement in airway at top of trachea and below pharynx Conducts air in and out of the trachea Prevents foreign objects from entering trachea Houses vocal cords Epiglottis = flaplike structure ▫ Stands upright, allows air to enter larynx ▫ During swallowing, presses downward to partially cover opening into larynx  Prevents foods and liquids from entering air passages

Trachea Flexible, cylindrical tube About 2.5 cm in diameter, 12.5 cm long Extends downward in front of esophagus and into the thoracic cavity Splits into right and left bronchi Mucous membrane lines trachea About 20 c-shaped pieces of hyaline cartilage

Bronchial Tree Branched airways leading from trachea to air sacs in lungs Primary bronchi ▫ Secondary bronchi  Tertiary bronchi  Alveolar ducts ▫ Alveolar sacs = clusters of smaller microscopic air sacs called alveoli (lie within capillary nets)

Structure of bronchus similar to trachea ▫ But, as tubes become smaller, cartilage lessons and smooth muscle becomes more prominent Function: Air passages ▫ Large surface area for gas exchange ▫ Oxygen diffuses through and enters blood in capillary networks ▫ Carbon dioxide diffuses from blood through walls and enters alveoli ▫ Adult lung: about 300 million alveoli, total surface area half the size of a tennis court

Lungs Soft, spongy, cone-shaped organs in thoracic cavity Mediastinum separates right and left lungs medially Diaphragm and thoracic cage enclose them

Bronchi enter lungs on medial surface Visceral pleura (serous membrane) attaches to each lung ▫ Folds back to become parietal pleura ▫ Forms part of the mediastinum ▫ Potential space between membranes = pleural cavity  Contains some fluid to reduce friction during breathing

Right lung is larger than the left ▫ Right has 3 lobes ▫ Left has 2 lobes Major branch of bronchial tree supplies each lobe Lung includes: ▫ Air passages, alveoli, blood vessels, connective tissues, lymphatic vessels and nerves