Respiratory System PDF

FUNCTIONS OF RESPIRATORY SYSTEM Provides an extensive area for gas exchange between air & circulating blood Moving air to & from the exchange surfaces of the lungs Protects respiratory surfaces from dehydration, temperature changes & other environmental variations...

FUNCTIONS OF RESPIRATORY SYSTEM Provides an extensive area for gas exchange between air & circulating blood Moving air to & from the exchange surfaces of the lungs Protects respiratory surfaces from dehydration, temperature changes & other environmental variations Defend respiratory system & other tissues from invasion by pathogenic micro- organisms Produce sounds involved in speaking, singing or non-verbal communication Assists in regulation of blood volume, blood pressure & the control of body fluid pH ORGANIZATION OF RESPIRATORY SYSTEM Upper respiratory system Nose Nasal cavity Paranasal sinuses Pharynx Filters, warms & humidifies air Lower respiratory system Larynx Trachea Bronchi Lungs RESPIRATORY TRACT Consists of airways that carry air to & from exchange surfaces of lungs. Conducting portion: Extends from entrance to nasal cavity to smallest bronchioles of lungs Respiratory portion : Includes respiratory bronchioles & air sacs (alveoli) By the time air reaches lung alveoli, most foreign particles & pathogens have been removed due to filtering, warming & humidification of air- due to properties of respiratory epithelium RESPIRATORY EPITHELIUM Consists of pseudostratified, ciliated, columnar epithelium with goblet cells. Lines entire respiratory tract except for finest conducting portions & alveoli Goblet cells & mucus glands beneath epithelium produce a sticky mucus that bathes exposed surfaces. In nasal cavity, cilia sweep any debris trapped in mucus or micro-organisms toward pharynx where it will be swallowed & exposed to enzymes & acids of stomach UPPER RESPIRATORY SYSTEM NOSE & NASAL CAVITY Nose is primary passageway for air entering respiratory system. Air enters paired external nares that open into nasal cavity. Vestibule: portion of nasal cavity contained within flexible tissues of external nose Vestibule contains coarse hair that trap foreign particles Nasal septum : divides cavity into right & left halves  Bony portion of nasal septum is formed by perpendicular plate of ethmoid & vomer. Anterior portion of septum is formed by hyaline cartilage. Bones of the nasal cavity Maxillary, nasal, frontal, ethmoid & sphenoid bones form lateral & superior walls of nasal cavity. NASAL CAVITY… Lateral wall Projecting from lateral wall are: Superior, middle & inferior conchae Air flows between adjacent conchae through superior, middle or inferior meatuses (narrow grooves) Incoming air bounces off conchal surfaces creating turbulence which causes small air borne particles to come into contact with mucus that lines cavity In addition to promoting filtration, turbulence allows extra time for humidifying & warming incoming air. NASAL CAVITY… Floor Formed by hard palate (maxillary & palatine bones) Soft palate extends posterior to hard palate marking boundary line between superior nasopharynx & rest of pharynx Nasal cavity opens into nasopharynx at internal nares. THE PHARYNX Nose, mouth, throat connect each other by a common passageway called pharynx. Pharynx is shared by digestive & respiratory systems. Extends between internal nares & entrance to larynx & oesophagus. Has three regions: nasopharynx, oropharynx, laryngopharynx NASOPHARYNX Superior part of pharynx Connected to posterior portion of nasal cavity via internal nares Separated from oral cavity by soft palate Lined by respiratory epithelium. Pharyngeal (adenoid) tonsil is located on posterior wall Lateral walls contain openings of auditory tubes OROPHARYNX Extends between soft palate & base of tongue at level of hyoid bone Posterior portion of oral cavity & posterior & inferior portions of nasopharynx communicates directly with oropharynx At boundary between naso & oropharynx epithelium changes from respiratory epithelium to stratified squamous epithelium Soft palate supports uvula & two pairs of pharyngeal arches Anterior palatoglossal arch Posterior palatoglossal arch Palatine tonsil lies in between LARYNGOPHARYNX Includes that portion of pharynx lying between hyoid bone & entrance to esophagus Most inferior portion of pharynx Lined by stratified squamous epithelium. THE LARYNX Inspired air leaves pharynx by passing through a narrow opening – glottis Larynx surrounds & protects glottis Larynx begins at C4 & ends at C7 vertebral levels Larynx essentially is a cylinder whose cartilaginous walls are stabilized by ligaments & muscle CARTILAGES OF LARYNX Thyroid Cricoid Epiglottis THYROID CARTILAGE Largest laryngeal cartilage Forms most of anterior & lateral walls of larynx Commonly called Adams Apple (laryngeal prominence) Inferior surface articulates with cricoid. Superior surface has ligamentous attachments to epiglottis & other smaller laryngeal cartilages. CRICOID CARTILAGE Ring shaped. Posterior portion greatly expanded providing support in absence of thyroid cartilage. Cricoid & thyroid cartilages protect glottis & entrance to trachea & their broad surfaces provide sites for laryngeal muscles & ligaments Superior surface of cricoid articulates with arytenoid cartilages. EPIGLOTTIS Leaf shaped. Projects above glottis Has attachments to thyroid cartilage & hyoid bone During swallowing, larynx is elevated, epiglottis fold back over glottis, preventing entry of liquid or solid food into respiratory passageways PAIRED Arytenoid Corniculate Cuneiform  Arytenoid cartilages (ladle shaped) : articulate with superior border of enlarged portion of cricoid cartilage Corniculate cartilages (horn shaped): articulate with arytenoid cartilages. Corniculate & arytenoid cartilages are involved in opening & closing the glottis & production of sound Cuneiform cartilages (wedge shaped): Lies within aryepiglottic fold that extends between lateral aspects of each arytenoid cartilage & epiglottis LARYNGEAL LIGAMENTS Intrinsic ligaments bind all 9 cartilages together to form larynx Extrinsic ligaments attach thyroid cartilage to hyoid bone & cricoid cartilage to trachea Ventricular & vocal ligaments extends between thyroid cartilage & arytenoids. Ventricular & vocal ligaments covered by folds of laryngeal epithelium that project into glottis Ventricular ligaments lie within superior pair of folds – ventricular folds (inelastic & help prevent foreign objects from entering glottis & provide protection for more delicate vocal folds THE TRACHEA Trachea is a tough, flexible tube with diameter of 2.5cm & length of 11cm Begins anterior to C6 vertebra in a ligamentous attachment to cricoid cartilage Ends in mediastinum at level of T5 vertebra Branches to form right & left primary bronchi Lining of trachea consists of respiratory epithelium overlying a layer of looser connective tissue (lamina propria) Trachea contains tracheal cartilages Each tracheal cartilage is bound to neighboring cartilages by elastic annular ligaments Tracheal cartilages stiffen tracheal walls & protect airway Also prevent its collapse or overexpansion as pressures change in respiratory system Each tracheal cartilage is C shaped. Closed portion of C protects anterior & lateral surfaces of trachea. Open portion of C faces posteriorly toward oesophagus Because cartilages do not continue around trachea, posterior tracheal wall can easily distort during swallowing permitting passage of large masses of food Trachealis: An inelastic ligament & band of smooth muscle connecting ends of each tracheal cartilage PRIMARY BRONCHI Right & left primary bronchi Carina marks line of separation between 2 bronchi Has cartilaginous C shaped supporting rings Right primary bronchus – larger diameter than left & descends towards lung in steeper angle Hilum of lung : Access for entry of pulmonary vessels, nerves, bronchi THE PLEURA Pleura is a serious membrane lined by mesothelium. Two pleural sacs – one on either side of mediastinum Pleural sac invaginated from medial side by lung so it has outer layer (parietal pleura) & inner layer (visceral pleura) Two layers continuous with each other around hilum of lung & enclose between them a potential space (pleural cavity) PULMONARY PLEURA Covers surfaces & fissures of lung except at hilum & along attachment of pulmonary ligament where it is continuous with parietal pleura Firmly adherent to lung & cannot be removed from it PARIETAL PLEURA Lines pulmonary cavities & thus adheres to thoracic wall, mediastinum & diaphragm. Has 4 parts THORACIC CAVITY Cavity of thorax contains right & left pleural cavities completely invaginated & occupied by lungs. Right & left pleural cavities separated by thick median partition called mediastinum. Heart lies in mediastinum. PULMONARY LIGAMENT DEFINTION: Parietal pleura surrounding root of lung extending downward beyond root as a fold. Function: Provides space into which pulmonary veins can expand during increased venous return; lung root also descends into it with descent of diaphragm PULMONARY VENTILATION REFERS TO PHYSICAL MOVEMENT OF AIR INTO & OUT OF BRONCHIAL TREE RESPIRATORY MUSCLES Contraction of diaphragm – increases volume of thoracic cavity – draws air into lungs. Inspiration: elevate ribs External & internal intercostal SCM; pectoralis minor; scalenes Serratus anterior Expiration: depress ribs transversus thoracis Abdominal obliques Rectus abdominis  THE LUNGS Lungs: pair of respiratory organs situated in thoracic cavity Each lung invaginates corresponding pleural cavity. Right & left lungs separated by mediastinum. Right & left lungs situated in right & left pleural cavities. Each lung is a blunt cone with apex pointing superiorly. Base of lung rests on diaphragm FISSURES & LOBES OF LUNG … RIGHT LUNG 3 lobes – viz.: superior, inferior, middle lobes Superior lobe separated from middle lobe by horizontal fissure. Middle lobe is separated from inferior lobe by oblique fissure. Horizontal fissure runs at level of 4th costal cartilage; meets oblique fissure in midaxillary line FISSURES & LOBES OF LUNG … LEFT LUNG 2 lobes viz.: superior & inferior Separated by oblique fissure. Tongue shaped projection of left lung below cardiac notch is called LINGULA; corresponds to middle lobe of right lung. DIFFERENCES BETWEEN RIGHT & LEFT LUNGS RIGHT LUNG Has 2 fissures, 3 lobes Anterior border straight Larger, heavier (700g) Shorter, broader LEFT LUNG 1. 1 fissure, 2 lobes 2. Anterior border interrupted by cardiac notch 3. Smaller, lighter (600g) 4. Longer, narrower STRUCTURES RELATED TO MEDIASTINAL SURFACE OF RIGHT LUNG Right atrium & auricle A small part of right ventricle Superior vena cava Lower part of right brachiocephalic vein Azygos vein Oesophagus Inferior vena cava Trachea Right vagus nerve Right phrenic nerve STRUCTURES RELATED TO MEDIASTINAL SURFACE OF LEFT LUNG Left ventricle, auricle, infundibulum & adjoining part of right ventricle Pulmonary trunk Arch of aorta Descending thoracic aorta Left subclavian artery Thoracic duct Oesophagus Left brachiocephalic vein Left vagus nerve Left phrenic nerve Left recurrent laryngeal nerve DIFFERENCES BETWEEN RIGHT & LEFT BRONCHI RIGHT BRONCHUS LEFT BRONCHUS Shorter Longer Wider Narrower Runs more vertically. Wider angle TERTIARY BRONCHI WHAT IS A BRONCHOPULMONARY SEGMENT? Largest subdivision of a lobe Separated from adjacent segments by septa Supplied by segmental bronchus & tertiary branch of pulmonary artery Drained by intersegmental parts of pulmonary veins Surgically resectable BRONCHOPULMONARY SEGMENTS Each lobe of lungs can be divided into smaller units – bronchopulmonary segment; Have names that correspond to tertiary bronchi. BRONCHIOLES ALEVOLAR DUCTS & ALVEOLI Respiratory bronchioles connected to alveoli along regions called alveola ducts. Passageways end at alveolar sacs. Each lung has 150 million alveoli – gives lung spongy appearance. ALEVOLUS & RESPIRATORY MEMBRANE Type 1 cells: squamous epithelial cells Type II cells: septal or surfactant cells. Type II cells secrete surfactant which coats inner surface of each alveolus which reduces surface tension in fluid coating alveolar surface without surfactant alveoli would collapse ARTERIAL SUPPLY OF LUNGS Bronchial arteries arise from systemic circulation & supply lung & its associated tissues with nutrients. Left bronchial artery arises from descending thoracic aorta; right bronchial artery arises from 3rd posterior intercostal artery. VENOUS DRAINAGE OF LUNGS Bronchial veins drain lung tissues Right bronchial vein drains into azygos vein; left bronchial vein drains into accessory hemiazygos vein or left superior intercostal vein SUPERFICIAL LYMPHATICS OF LUNG SUPERFICIAL (SUBPLEURAL) LYMPHATIC PLEXUS (drains lung tissue & visceral pleura BRONCHOPULMONARY (HILAR) LYMPH NODES