Respiratory System

Functions of the Respiratory System 1.Pulmonary ventilation – movement of gases into/out of lungs for exchange 2.Gas conditioning 3.Sound production 4.Olfaction 5.Defense

Divisions of the Respiratory System Structurally divided into: upper and lower respiratory tracts Functionally divided into: – Conducting portion – Respiratory portions

Upper Respiratory Tract 1.Nose and nasal cavities – Nasal conchae – condition air 2.Paranasal sinuses 3.Pharynx – Nasopharynx contains: Opening of eustachian tube Pharyngeal tonsil – Oropharynx contains: Palatine tonsils Lingual tonsils – Laryngopharynx All are part of conducting portion

Lower Respiratory Tract Conducting portion – Larynx – Trachea – Bronchi – Bronchioles Respiratory portion – Respiratory bronchioles – Alveolar ducts – Alveoli

Larynx Connects pharynx to trachea Three major cartilages: – Thyroid cartilage – Cricoid cartilage – Epiglottis Covers opening to airway when swallowing

Larynx Arytenoid cartilages - important in sound production

Sound Production vocal ligaments – covered by mucous membrane – Ligaments + membrane = vocal folds (“true” vocal cords) vestibular ligaments – Vestibular folds (“false” vocal cords) Opening between vocal folds - rima glottidis – vocal folds + rima glottidis = glottis Air forced thru rima glottidis  vibration of vocal folds  sound – Muscles pivot arytenoid cartilages – abduct or adduct folds Vocal folds in action

Trachea Supported by C-shaped tracheal cartilages – Keep airway open – Posteriorly, connected by trachealis muscle Lined with PSCC and goblet cells trachealis

Bronchial Tree primary bronchi  secondary bronchi  tertiary bronchi – All bronchi lined with PSCC – Rings of cartilage get smaller and smaller Bronchi  bronchioles – < 1 mm diameter – No cartilage – Lining simple ciliated columnar  cuboidal

Bronchioles Walls composed of relatively thick layer of smooth muscle – Allows for bronchoconstriction/dilation Bronchioles  terminal bronchioles – last part of conducting portion Terminal bronchioles  respiratory bronchioles  alveolar ducts  alveoli – Primary location of gas exchange between blood and air – Surface area of each lung is approx. half a tennis court

Alveoli 1.Alveolar type I cells – simple squamous ET – rapid diffusion of gases 2.Alveolar type II cells – produce pulmonary surfactant decreases surface tension w/in alveolus prevents collapse of alveoli

Alveolar Macrophages Third type of cell, alveolar macrophage (dust cell) – engulfs microorganisms or particulate matter

Lungs and Pleura Lungs located in pleural cavities serous membrane called pleura – Visceral pleura – Parietal pleura

Left Lung Slightly smaller than right lung – b/c of heart – cardiac notch Oblique fissure divides lung into superior and inferior lobes

Right Lung oblique and horizontal fissures – divide lung into superior, middle and inferior lobes

Thoracic Wall Dimensional Changes During Respiration 1.Vertical – movement of diaphragm 2.Lateral – muscles attached to ribs 3.Anterior/Posterior – muscles attached to ribs Expansion of cavity  inhalation Compression of cavity  exhalation

Muscles Attached to Ribs Muscles attached to ribs: 1.Scalenes (inhalation) Elevate ribs 1 &2 2.External intercostal (inhalation) Elevate ribs 3.Internal intercostal (forced exhalation) Depress ribs

Respiratory Control Centers in the Brainstem Respiratory rhythmicity center in medulla oblongata – controls rate and depth of breathing – Dorsal respiratory group (DRG) stimulates muscles of inspiration – Ventral respiratory group (VRG) controls forced exhalation – Inactive during normal breathing

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