Respiratory Anatomy - Thorax, Lungs, and Mediastinum PDF

The Respiratory System 1 Respiratory Anatomy – the Thorax, Lungs, Mediastinum Lecture Outline I. Divisions of the Respiratory System II. Thorax III. Muscles of the Respiratory System IV. Lungs V. Pleura VI. Mediastinum 2 Respiratory Anatomy – the Thorax, Lungs, Mediastinum Objectives 1.Identi...

The Respiratory System 1 Respiratory Anatomy – the Thorax, Lungs, Mediastinum Lecture Outline I. Divisions of the Respiratory System II. Thorax III. Muscles of the Respiratory System IV. Lungs V. Pleura VI. Mediastinum 2 Respiratory Anatomy – the Thorax, Lungs, Mediastinum Objectives 1.Identify major structures of the upper and lower respiratory system 2.Relate the structure of the thorax to its function 3.Identify three types of ribs and their defining characteristics 4.Relate the surface anatomy of the anterior thoracic wall to the sternum & sternal angle 5.Explain the structure and function of the diaphragm 6.Identify and describe the accessory muscles of respiration 7.Describe the structure, blood supply, lymphatics, and innervation of the lungs 8.Describe the structure and function of the pleurae 9.Explain the structural alteration and implication of a pneumothorax 10.Identify the divisions of the mediastinum and the contents of each 3 References Assigned reading from your text: Selections from Moore Chapters 4,5, 8, 9 4 I. Divisions of the Respiratory System 5 Respiratory System Terminology qRespiratory system includes the axial skeleton, extrapulmonary airways, and lungs • Extrapulmonary airways end at primary bronchus • Intrapulmonary airways lie inside the lungs qDivisions of the respiratory system include: • Upper and lower airways- lie above and below the vocal cords • Conducting and respiratory zones of airways are related to the presence of alveoli • Conducting airways have no alveoli, transmit bulk flow & end at terminal bronchioles • Respiratory airways have alveoli & participate in gas exchange (diffusion) Upper and lower airways Conducting and respiratory zones 6 Upper and Lower Divisions of the Respiratory System qUpper respiratory system •Nose •Mouth •Pharynx •Larynx above vocal cords qLower respiratory system •Larynx below vocal cords •Trachea •Bronchi - 1º - 1 per lung - 2º - 2 left / 3 right - 3º - ~ 10 per lung •Bronchioles - Terminal- end of conducting zone - Respiratory- beginning of respiratory zone (gas exchange) •Alveolar ducts •Alveolar sacs •Alveoli 7 II. Thorax 8 Characteristics of the Thorax q Functional characteristics of the thoracic skeleton • Skeletal components: – 12 thoracic vertebrae – 12 pairs ribs – Sternum • “Cone-shaped” – Thoracic inlet: • Narrow superior thoracic aperture – Thoracic outlet: • Broad inferior thoracic aperture • Strength to protect organs of thorax • Flexibility allows movement for ventilation • Scoliosis is an example of pathophysiology related to altered structure. – Severe kyphoscoliosis can compromise ventilation 9 Rib Anatomy: § A typical rib (costa) consists of the following parts: • • • Head- lies next to and articulates with vertebrae Neck- lies between the head and tubercle Body/shaft- extends from the tubercle • • Tubercles (also tuberosity)- a small elevation on a bone • • • Thin inferior border possesses a costal groove housing veins, arteries, and nerves Ribs 11 and 12 do not have tubercles Facets- small smooth areas on a bone Articulations -fixed or moveable joints where structures meet 10 Ribs (costae) and Their Posterior Articulations • Posteriorly, ribs articulate with thoracic vertebrae • Head and necks of ribs 2-9 articulate with 2 vertebral bodies • • • Centrum (body) of their associated vertebra and with centrum of next superior vertebra Rib 1 articulates with T1 only Ribs 11 & 12 have no tubercles and do not articulate with the sternum Tubercle of rib articulates with costal facets of adjacent thoracic vertebral transverse processes 11 Three Types of Ribs q Classified by sternal attachment • True ribs- 1st -7th ribs • Vertebrosternal • Attach directly to sternum via their own costal cartilage • False ribs- 8th,9th, & usually 10th • Vertebrochondral • Indirect attachment to the sternum via their cartilage • Floating ribs- 11th and 12th • Vertebral • No sternal connection • These ribs end in the posterior abdominal musculature 12 Ribs (costae) and Their Anterior Articulations q Anteriorly- Body of ribs 1-10 articulate with the sternum through their costal cartilages (hyaline) • 1st pair - articulates with manubrium • 2nd pair - articulates with manubrium & body • 3rd-6th pairs - articulate with the body of the sternum • 7th pair - articulates with body & xiphoid process • 8th-10th pairs - attach to the 7th costal cartilage 13 Rib Orientation is Oblique (at an angle) • In adults- ribs course in an oblique, inferior direction from their thoracic vertebral articulation to their anterior sternal articulation • Infants’ ribs are horizontal- they rely more on diaphragm than expansion of thoracic cavity • The sternal attachment is at a lower level than the vertebral articulation with the spine • “Pump-handle” movement: • • • • Vertebrosternal ribs slope anteriorly Orientation allows movement to raise the sternum superiorly/anteriorly Increases the anterior-posterior diameter and volume of thorax during inspiration “Bucket-handle” movement • • Middle of ribs 7-10 is lower than either anterior or posterior articulations Movement elevates the middle (lateral portion) of the rib to increase the transverse diameter 14 Sternum q The sternum consists of the manubrium, body, and xiphoid process (ensiform cartilage) • Manubrium- uppermost portion –Suprasternal or jugular notch – superior concave area • Can be palpated externally • Lies in same plane as 2nd thoracic vertebra= corresponds to mid-portion of the trachea • Radiographically where the tip of endotracheal tube should be located- above carina –Manubriosternal junction- corresponds to the carina • Body (aka gladiolus) - largest portion of sternum- formed by four sternabrae –Superficially, the intermammary cleft overlies the sternal body • Xiphoid process – lowermost and smallest portion of the sternum in the epigastric fossa –Begins as hyaline cartilage; ossifies into bone (>40 yo) –Potential site of injury: blunt trauma or CPR 15 Surface Anatomy of the Anterior Thoracic Wall q • • • • Clavicle and thoracic cage provide prominent surface landmarks Jugular notch is located between the medial ends of the clavicles The first rib is difficult to palpate-it lies deep to the clavicle and a thick layer of muscle The manubriosternal joint correlates with multiple structures The intermammary cleft (sulcus) superficially marks the division of the breasts q • • • Cutaneous innervation of the anterior thoracic wall is from ventral rami & forms dermatomes Nipple- T4 Xiphoid process- T6 dermatome (T9 vertebra) Umbilicus- T10 16 Sternal Angle qThe junction of the manubrium and body of the sternum is known by the following names: • Sternal angle • Sternal angle of Louis • Manubriosternal joint • Transverse thoracic plane qThis landmark correlates with: • Projected posteriorly- T4-T5 vertebrae • Carina (bifurcation) of the trachea into right and left primary bronchi • Start and end of aortic arch • 2nd rib articulates at this joint • Border between the superior and inferior mediastina • The thoracic duct shifting to the left of the esophagus 17 III. Muscles of the Respiratory System 18 Functions of the Diaphragm q Functions of the diaphragm include: • Respiration- The diaphragm is the primary muscle of inspiration- contribution varies based on body position – Flattens when contracted to increase the vertical dimension of the thoracic cavity • Venous return- Alternating contraction and relaxation causes pressure changes in the thoracic and abdominopelvic cavities that facilitate venous return to the heart • Barrier- “Dome-shaped” muscle separates the thoracic cavity from the abdominal cavity 19 Diaphragm • Functional characteristics of the diaphragm – Not a single muscle • Embryologically derived from two separate hemi-diaphragms that Fuse during gestation – Right hemi-diaphragm is normally slightly higher than the left • Right dome rests on liver • Heart pushes downward on the left side, and left dome rests on fundus of the stomach • Sniff test – Under abnormal conditions it is possible for one hemi-diaphragm to be incapacitated • Ipsilateral diaphragm paralysis a common side effect of an ISB – When viewed by fluoroscopy- Nonfunctional side will rise upward- paradoxical movement. 20 Apertures in the Diaphragm q Three openings allow passage of structures from thoracic cavity into abdominal cavity • Vena cava foramen (caval opening) located at T8 • Esophageal hiatus (and vagus nerve) located at T10 • Aortic foramen retrodiaphragmatic opening located at T12 • Created by the crus of the diaphragm 21 Origins and Insertion of the Diaphragm q Muscular portion of the diaphragm has three regions of origin (outlined with broken lines): • • • Lumbar part – two crura originate from the bodies of the upper two (left) or three (right) lumbar vertebrae Costal part- muscle fibers arise from the inner surfaces of the lower six ribs Sternal part- muscle fibers originate from the inner surface of the xiphoid q These fibers extend centrally to insert into its central tendon • • The central tendon is the structure the diaphragm’s muscle fibers primarily pull upon when they concentrically contract Central tendon is connected to the pericardial sac that lies on superior side of diaphragm 22 Congenital Diaphragmatic Hernia q Congenital defects occur when connective tissues of hemi-diaphragms do not fuse properly • Produces a communication between the thoracic and abdominal cavity • Herniation of abdominal viscera through a defect- usually occurs on left due to liver on right • Due to limited space, typically one lung does not develop • High mortality rate due to pulmonary hypoplasia 23 Innervation of Diaphragm q Motor innervation to the diaphragm is via the left and right phrenic nerves (C3,C4,C5) • Normally- adequate function maintained if one hemi-diaphragm is incapacitated • Phrenic nerves supply: • Motor (efferent) innervation to entire diaphragm • Sensory (afferent) innervation – except to peripheral edges • Lower intercostal nerves provide peripheral sensation (afferent) • Pain originating from the diaphragm is referred to shoulder area 24 Positions of Diaphragm in Relation to the Thorax q The dome (cupola) of the diaphragm may rise as high as the level of the 4th intercostal space at rest • 4th ICS on right and 5th ICS on the left • Domes descend 2 spaces bilaterally when contracted q Major factors affecting position of diaphragm • Recoil of lungs after expiration causes diaphragm to move higher into thoracic cavity • Force exerted on superior surface of diaphragm due to fluid in lungs (e.g. congestive heart failure); diaphragm does not return to normal resting position • Force exerted on abdominal surface of diaphragm by abdominal viscera when lying down or during pregnancy • Intra-abdominal tension caused by abdominal muscle contractions: standing causes abdominal muscle contractions that push abdominal contents upward on abdominal surface of diaphragm 25 Accessory Muscles of Respiration- Thorax q Some superficial anterior thoracic muscles function as accessory muscles of respiration • When inspiration is deep and forceful • Pectoralis major and pectoralis minor innervated by pectoral nerves in fascial plane • Serratus anterior innervated by the long thoracic nerve • Elevate ribs to expand thoracic cavity Regional Anesthesia of Accessory Muscles of Respiration- Thorax q Pectoralis nerve (pecs) and serratus anterior plane (SAP) blocks are fascial plane blocks placed for breast and lateral thoracic wall surgery/pain (eg rib fractures) • SAP targets the lateral cutaneous branches of intercostal nerves (see Moore 4.15, 4.16) • If patient has respiratory issues- these blocks may allow them to take deeper breaths • May decrease opioid use https://www.nysora.com/regional-anesthesia-forspecific-surgical-procedures/thorax/pectoralisserratus-plane-blocks/ Accessory Muscles of Respiration- Neck q Anterior, middle, and posterior scalene muscles act primarily on the vertebral column: • • • • Attach to the cervical transverse processes and first two ribs Can assist inspiration by elevating the first and second ribs Innervated by C3-C8 Both cervical and brachial plexuses exit between anterior and medial scalenes • Phrenic nerve descends vertically on the anterior scalene q Sternocleidomastoid is the largest muscle of the anterior neck • • • Named by its bony attachments- the mastoid process of the temporal bone superiorly and inferiorlythe medial clavicle and manubrium Can assist inspiration by elevating the rib cage Innervated by CN XI- spinal accessory nerve FIGURE 25-4 Muscles of the anterior cervical spine. (Reproduced, with permission, from Chapter 25. Overview of the Neck. In: Morton DA, Foreman K, Albertine KH. eds. The Big Picture: Gross Anatomy. New York, NY: McGraw-Hill; 2011.) Superficial and Middle Intercostal Muscle Layers of the Thoracic Wall q Most activity of the intercostal muscles is isometric and supports the intercostal space • They resists paradoxical movement during inspiration • Intercostals are innervated by anterior rami of T1-T11 spinal nerves q Superficial intercostal muscle layer • External intercostal muscles • Active during inspiration- eupnea or forced • • • • • Fibers pass downward/forward- elevate ribs Anteriorly replaced with membrane Continuous with external obliques Can maintain eupnea if diaphragm unable Contribution to eupnea is position dependent q Middle intercostal muscle layer • Internal intercostal muscles • Accessory muscles of active expiration • • • • Fibers oriented upward/backward- Depress ribs • Right angle to external intercostals Continuous with internal obliques Posteriorly replaced with membrane Separated from deep layer by nerves and vessels 29 Deep Intercostal Muscle Layer of the Thoracic Wall q Deep intercostal muscle layer depresses the ribs facilitating active expiration • The muscles of the deep layer vary by location: • Anteriorly- the transversus thoracis muscle • Laterally- the innermost intercostals • Posteriorly- the subcostal muscles cross one or two intercostal spaces 30 IV. Lungs 31 Gross Anatomy of the Lungs q Lungs are the organs of gas exchange • Cone-shaped structures located in the thorax • Lungs occupy most of the thoracic cavity except the mediastinum • Attach to the trachea and heart • Externally, the lungs have an apex and three other surfaces/regions and three borders 32 Surfaces of the Lung qEach lung surface corresponds to its respective region of the chest: •Apex of the lungs: uppermost portion; extends ~ 1” above the medial 1/3 of the clavicle • Projects into the root of the neck through the superior thoracic aperture • Needle placement can puncture and cause a pneumothorax •Costal surfaces of the lungs: Convex area related to inner surface of ribs •Mediastinal surface of the lungs: lies adjacent to the mediastinum (space between lungs) •Base of lungs: Diaphragmatic surface: concave surface that lies on the surface of diaphragm • Lowermost portion- auscultated laterally or posteriorly 33 Lung Borders q Borders or margins of the lung are associated with the hilum and mediastinum – Anterior border- thin layer of tissue on anterior side of lung from apex to base where anterior and mediastinal surfaces meet – Posterior border- thin layer of rounded tissue located at the boundary where posterior costal and mediastinal surfaces meet – Inferior border- thin layer of lung tissue at periphery of base of lung where costal surfaces and mediastinal surfaces meet 34 Levels of Inferior Border at End-Expiration • Anterior aspect: • 6th rib at mid-clavicular line • 8th rib at mid-axillary line • Posterior aspect: • 10th rib adjacent to vertebral column at the mid-clavicular line 35 Lobes of Lungs qThe right lung has 3 lobes and the left lung has 2 • Right lung: 3 lobes- Superior, Middle and Inferior • Separated by two fissures – horizontal fissure and oblique fissure • Greater width (no heart), volume, weight (due to more blood) than left lung • Left lung: 2 lobes- Superior and Inferior • Separated by an oblique fissure • Slightly greater height than right lung • A cardiac notch is present and part of the upper left lobe • The tongue-like lingula is an extension of the left superior lobe that slides in and out of the costomediastinal recess with respiration • Lower lobes can be easily visualized laterally and posteriorly 36 Hilum of the Lung q The hilum is the wedge-shaped area on the mediastinal surface of each lung • Structures of the root of the lung pass into or exit lung at the hilum • Pulmonary artery -superiormost on left • Superior pulmonary veins - anteriormost • Inferior pulmonary veins -inferiormost • Main bronchus - Against and in middle of posterior boundary with bronchial vessels coursing posteriorly q Mnemonic “RALS”: “Right Anterior, Left Superior” - Location of pulmonary artery in relationship to the primary bronchus 37 Innervation of the Lung- Pulmonary Plexuses q Right and left plexuses lie anterior and posterior to lung roots • Vagus nerve from posterior plexus contribute to esophageal plexus • Then reforms to vagal trunks q Pulmonary plexus follows the trachea and bronchial tree • Provides autonomic innervation to the smooth muscle and glands • Visceral afferent fibers transmit nociceptive and reflexive sensations via CNX q Visceral afferents consist principally of: • Bronchopulmonary stretch receptors • Irritant receptors of proximal airways • • • Nonspecific Stimulate cough, mucus, bronchoconstriction C fibers and juxtacapillary (J) receptors • Respond to mechanical and chemical stimuli 38 Pulmonary and Bronchial Vessels Provide a Dual Blood Supply q For gas exchange to occur, lung must be connected to the heart so that oxygenated blood and deoxygenated blood flow between both organs • Pulmonary vessels circulate blood between heart and lungs • Parenchymal tissue supply • Respiratory bronchioles to alveoli • Pulmonary arteries branch from the pulmonary trunk • Pulmonary veins (4) transport oxygenated blood to left atrium • Bronchial vessels are the vascular supply to lung stroma • Conducting airways and visceral pleura • Bronchial arteries branch from the descending aorta • Bronchial veins drain bronchi before emptying into: •Azygos (“unpaired”) vein on right •Accessory hemiazygos on the left •Finally SVC 39 Lung Lymphatics qLymphatic drainage of lungs predictably follows ipsilateral path to right lymphatic trunk and left thoracic duct – Exception- left inferior lobe drains to right pathway •Lymph proceeds from pulmonaryà hilarà carinalà paratracheal nodesà • Then right lymphatic duct (right lung) and thoracic duct (left lung) •Lymphatics are absent in the vicinity of alveoli • Arise at the level of the terminal bronchioles 40 V. Pleura 41 Two Pleural Membranes Create a Pleural Cavity qLungs are located within pleural sacs composed of two layers of serous membrane •Pleural sacs are composed of the following: • Parietal pleura- the external serous membrane lining the internal thoracic wall • Visceral pleura- the internal serous membrane attached to/covering the lung surface • Pleural cavity- a potential space containing a thin lubricating film of pleural fluid •Pleural space: • Contains only pleural fluid – no other structures • Secreted by both serous membranes • Surface tension of pleural fluid keeps lungs in contact with thoracic wall • The thin layer of pleural fluid does the following: • Couples the visceral and parietal pleura which prevents alveolar collapse • Reduces resistance during breathing movements • An intact pleural space is required to maintain lung inflation at end- expiration • Parietal pleura is continuous with visceral pleura at root of lung - Forms a collar around the structures at the hilum 42 Divisions of the Parietal Pleura Lining the Thoracic Cavity: q Areas of the parietal pleura are named according to the structures they line • Costal parietal pleura: – Lines internal surface of ribs • Diaphragmatic parietal pleura: – Lines superior surface of diaphragm • Mediastinal parietal pleura: – Lines lateral surface of mediastinum – • Pulmonary ligament is a reflection of mediastinal parietal pleura at the lung root (hilum) that allows for: • Inferior movement of the lung root with inspiration • Expansion of the pulmonary vein Cervical parietal pleura: – Forms a dome- cupula- over lung apex – Extends 2-3 cm above superior thoracic aperture 43 Lines of Pleural Reflections and Recesses q Pleural Reflections • Regions where parietal pleural membrane turns back and folds on itself • Most apparent during expiration • Costal reflections • Sternal reflections • Vertebral reflections q Pleural recesses • Potential spaces within pleural reflections • Sites where pleural fluid accumulates during eupnea (quiet breathing) • Lungs do not fully occupy pleural sac during expiration or eupnea • Two major recesses: § Costomediastinal recesses § Costodiaphragmatic recesses 44 Parietal Pleura Relative to Ribs q Anterior View: – Crosses 8th rib at mid-clavicular line – Crosses 10th rib at mid-axillary line q Posterior View: – Crosses at 12th Rib • Inferior border is 2 ribs lower than lung border 45 Innervation of Pleura is Sensory Only qParietal pleura is sensitive to pain • Intercostal nerves supply costal parietal pleura and peripheral portion of diaphragmatic parietal pleura • Phrenic nerves supply central portion of diaphragmatic parietal pleura and mediastinal parietal pleura • Parietal pleura contains general sensory receptors q Visceral pleura is insensitive to pain • Nerve fibers of CN X lie between the visceral pleura and lung surface • No pain receptors in visceral pleura qBlood supply: • Parietal pleura• Receives its blood supply from branches of adjacent structures Parietal Pleura Blood Supplied by Arteries of Thoracic Wall q Parietal pleura receives its vascular supply via: • Internal thoracic • Intercostal, and • Musculophrenic arteries • Venous drainage by intercostal veins and internal thoracic veins 47 Visceral Pleura Supplied by Bronchial Arteries, Drained by Pulmonary Veins qVisceral pleura receive blood from bronchial arteries which branch off of aorta •Blood drained by pulmonary veins •Blood vessels enter/leave by hilum 48 Disruption of Pleural Cavity q Air or fluid can disrupt the coupling of the parietal and visceral pleura and cause pulmonary collapse • • • • Pneumothorax- entry of air into pleural cavity Bronchopulmonary fistula- rupture of a pulmonary lesion into the pleural cavity Hemothorax- blood in pleural cavity Hydrothorax- fluid accumulation in pleural cavity 49 VI. Mediastinum 50 Mediastinum q Mediastinum is the central compartment of the thoracic cavity • Contains all thoracic viscera except lungs q Boundaries of this anatomic region are: • Superior: rib 1 • Anterior: sternum (posterior surface) • Lateral: mediastinal parietal pleurae • Posterior: thoracic vertebral column- the anterior surface of centra • Inferior: diaphragm 51 Transverse Thoracic Plane Divides the Mediastina qTransverse plane corresponding to T4-T5 defines the: •Superior mediastinum above – contains the trachea and great vessels •Inferior mediastinum below- is further divided into anterior, middle, and posterior mediastinum 52 Superior Mediastinum q Superior mediastinum is situated between the sternal angle and thoracic inlet q Contents: – Trachea – Aortic arch and its three branches • Brachiocephalic artery or trunk- aka known as innominate artery • Left subclavian artery • Left common carotid artery – – – – – SVC Brachiocephalic veins Esophagus Vagus and phrenic nerves Part of thymus 53 Divisions of the Inferior Mediastinum q Inferior mediastinum has three subdivisions: § • Anterior mediastinum lies between the pericardium and sternum Contents: fat and part of the thymus or its remnant § • Middle mediastinum is occupied by the heart Contents: heart and pericardial sac § • • Posterior mediastinum lies deep to the pericardial sac Contents: Structures vertically traversing thorax See next slide Inferior Mediastinum 54 Posterior Mediastinum Contains Structures Vertically Traversing Thorax q Posterior Mediastinum Contains: • Esophagus • Carina/ primary bronchi • Descending thoracic aorta • Azygos system of veins • Vagus and sympathetic nerves *For practice- Draw the divisions of the mediastina on the images. 55 1. A runner uses which muscles during expiration? a. Diaphragm and external intercostals b. Diaphragm and internal intercostals c. Sternocleidomastoid d. Internal intercostals 2. Which ribs are most responsible for the pump-handle effect? a. Vertebrosternal b. Vertebrochondral c. Vertebral d. All ribs contribute to this effect 3. Which of the following is the reason you would not place bilateral interscalene brachial plexus blocks? a. The proximity of the phrenic nerves to the brachial plexus b. The diaphragm is partially innervated by the brachial plexus c. The primary motor innervation to the diaphragm is from the brachial plexus d. There is no reason to avoid bilateral interscalene blocks 4. Phrenic nerve provides pain (sensory) innervation to which of the following regions of pleura? a. Diaphragmatic visceral pleura b. Mediastinal parietal pleura c. Costal visceral pleura d. Peripheral diaphragmatic parietal pleura 5. The heart is located in which mediastinum? a. Superior b. Anterior c. Middle d. Posterior 56