Lecture 1 Anatomy PDF

Chapter 7 Head 955 The Bottom Line PTERYGOPALATINE FOSSA Root The pterygopalatine...

Chapter 7 Head 955 The Bottom Line PTERYGOPALATINE FOSSA Root The pterygopalatine fossa is a major distributing cen Dorsum ter for branches of the maxillary nerve and the ptery of nose gopalatine (third) part of the maxillary artery. It is Apex located between, and has communications with, the Naris (nostril) infratemporal fossa, nasal cavity, orbit, middle cranial Nasal septum fossa,pharyngeal vault, maxillary sinus, and oral cavity (palate). The contents of the pterygopalatine fossa Ala of nose are the maxillary nerve (CNV), the parasympathetic pterygopalatine ganglion, the third part of the maxil lary artery and accompanying veins, and a surrounding (A)) Lateral view fatty matrix. Nasal part of frontal bone NOSE Nasal bone Frontal process of maxilla The nose is the part of the respiratory tract superior to the Lateral process hard palate and contains the peripheral organ of smell. It -Accessory nasal cartilage includes the external nose and nasal cavity, which is divided Septal nasal cartilage into right and left cavities by the nasal septum (Fig. 7.101A). Major alar cartilage The functions of the nose include olfaction (smelling), res piration (breathing), ltration of dust, humidification of Fibro-areolar tissue inspired air, and reception and eliminationof secretions from the paranasal sinuses and nasolacrimal ducts. Naris (nostril) External Nose (B) Anterior view The external nose is the visible portion that projects from the face; its skeleton is mainly cartilaginous (Fig. 7.10IB). FIGURE7.101. External nose. A.The surface anatomy of the nose is shown. The nose is attached to the forehead by its root. The rounded bor Noses vary considerably in and shape, mainly because size der between the apex and the root is the dorsum. B. The cartilages of the of differences in these cartilages. The dorsum of the nose nose are retracted inferiorly to expose the sesamoid cartilages. The lateral extends from the root of the nose to the apex (tip) of the nasal cartilages are fixed by sutures to the nasal bones and are continuous nose. The inferior surface ofthe nose is pierced bytwo piri with the septal cartilage. form (L. pear-shaped) openings, the nares (nostrils, ante rior nasal apertures), which are bound laterally by the alae (wings) of the nose. The superior bony part of the nose, the bony partsof the nasal septum. The cartilaginous part of including its root, is covered by thin skin. the nose consists of five main cartilages: two lateral cartilages, The skin over the cartilages of the nose is covered with two alar cartilages, and one septal cartilage. The U-shaped alar thicker skin, which contains many sebaceous glands.The skin cartilages are free and movable; they dilate or constrict the extends into the vestibule of thenose (Fig.7.103A), where nares when the muscles acting on the nose contract. it has a variable number of stiff hairs (vibrissae). Because they are usually moist, these hairs filter dust particles from NASAL SEPTUM entering the nasal cavity. The junction of the skin and air mucousmembrane is beyond the hair-bearingarea. : The nasal septum divides the chamber of the nose into two nasal cavities. The septum has a bony part and a soft mobile cartilaginous part. The main components of the nasal sep SKELETON OF EXTERNAL NOSE tum are the perpendicular plate ofthe ethmoid, the vomer, The supporting skeleton of the nose is composed of bone and and the septal cartilage. The thin perpendicular plate of hyaline cartilage. Thebony part of thenose (Figs. 7.101B and the ethmoid bone, forming the superior part of the nasal 7.102) consists ofthe nasal bones, frontal processes of the mar septum, descends from the cribriforn plate and is continued illae, the nasal part of the frontal bone and its nasal spine, and superior to this plate as the crista galli. The vomer,a thin 985/1170  / Head Chapter Bones: Frontal OEthmoid Nasal Palatine Maxilla Sphenoid Inferior concha Vomer Cribriform plate of Sphenopalatine Crista galli -Perpendicular ethmoid bone foramen plate of ethmoid Frontal bone Crest of bone sphenoid Superior concha bone Nasal bone Superior meatus -Nasal spine of Middle concha - frontal bone Frontal process Medial pterygoid Septal Lacrimal bone Vomer plate cartilage Middle meatus -Horizontal Inferior concha plate of Vomeronasal palatine Inferior meatus bone cartilage Nasal crest of Palatine Pterygoid palatine bone Nasal crest of maxilla process hamulus of maxilla (A) Lateral wall of nasal cavity (B)Nasal septum Medial view Lateral view FIGURE 7.102. Lateral and medial (septal) walls of right side of nasal cavity. The walls are separated and shown as adjacent pages of a book. The medial view shows the right lateral wall of the nasal cavity, and the lateral view shows the nasal septum. The nasal septum has a hard (bony) part located deeply (posteriorly) where it is protected and a soft or mobile part located superficially (anteriorly) mostly in the more vulnerable external nose. flat bone, forms the postero-inferiorpart of the nasal septum, BOUNDARIES OF NASAL CAVITIES with some contribution from the nasal crests of the maxillary The nasal cavities have a roof, loor, and medial and lateral and palatine bones. The septal cartilage has a tongue-and walls. groove articulation with the edges the bony septum. of The roofof the nasal cavities is curved and narrow, except Nasal Cavities at its posterior end, wherethe hollow body the sphenoid of forms the roof. It is divided into three parts (frontonasal, The term nasal cavity refers to either the entire cavity or to ethmoidal, and sphenoidal) named from the bones form the right or left half, depending on the context. The nasal ing each part (Fig. 7.102). cavity is entered anteriorly through the nares (nostrils). It The floor of the nasal cavities is wider than the roof and opens posteriorly into the nasopharynx through the choanae isformed by the palatineprocesses ofthe maxilla and the (Fig. 7.9). Mucosa lines the nasal cavity, except for the nasal horizontal plates thepalatine bone. of vestibule, which is lined with skin (Fig. 7.103A). The medial wall of the nasal cavities is formed by the nasal The nasal mucosa firmly bound to the periosteum septum. and perichondrium of the supporting bones and cartilages The lateral walls of the nasal cavities are irregular owing to of the nose. The mucosa is continuous with the lining of all three bony plates, the nasal conchae, which project inferi the chambers with which the nasal cavities communicate: orly, somewhatlike louvers (Figs. 7.102A, 7.103,and 7.108). the nasopharynx posteriorly,the paranasal sinuses supe riorly and laterally, and the lacrimal sac and conjunctiva FEATURES OF NASAL CAVITIES superiorly.The inferior two thirds of the nasal mucosa is the respiratory area, and the superior one third is the olfactory The nasal conchae (superior, middle, and inferior) curve area (Fig. 7.106B). Air passing over the respiratory area inferomedially,hanging like louvers or short curtains from is warmed and moistened before it passes through the rest the lateral wall. The conchae (L. shells) or turbinates of many of the upper respiratory tract to the lungs. The olfactory mammals (especially running mammals and those existing in area contains the peripheral organ of smell; sniffing draws extreme environments) are highly convoluted, scroll-like struc air to the area. tures that offer a vast surface area for heat exchange. In both 986/1170 958 Chapter 7 Head humans with simple plate-like nasal conchae and animalswith When infected or irritated, the mucosa covering the conchae complex turbinates, a recess or nasal meatus (singular and may swell rapidly, blockingthe nasal passage(s) on that side. in the nasalcavity) underlies each of the bony plural: passage(s) The spheno-ethmoidal recess, lying superoposteriorto formations.The nasal cavity is thus divided into five passages: the superiorconcha, receives the opening of the sphenoidal a posterosuperiorly placed spheno-ethmoidal recess, three lat sinus,an air-flled cavity in the body of the sphenoid. The erally located nasal meatus (superior, middle, and inferior), superior nasal meatus is a narrow passage between the and amediallyplaced common nasal meatus into which the superior and the middle nasal conchae into which the pos four lateral passages open. The inferior concha is the longest terior ethmoidal sinuses open by one or more orifices (Fig. and broadestof theconchae and is forned by an independent 7.103A). The middle nasal meatus is longer and deeper bone (ofthesame name, inferior concha) covered bya mucous than the superior one. The anterosuperior part of this pas membrane that contains large vascular spaces that can enlarge sage leads into a funnel-shaped opening, the ethmoidal to control the caliber of the nasal cavity. The middle and infundibulum, through which it communicates with the superior conchae are medial processes tlhe ethmoid bone. frontal sinus (Fig.7.104).The passage that leads inferiorly of from each frontal sinus to the infundibulum is the fronto anterior part of the nasal septum is the site of an anastomotic nasal duct (Fig. 7.103B). The semilunar hiatus (L.hiatus arterial plexus involving all five arteries suppling the septum semilunaris)is a semicirculargroove into which the frontal (Kiesselbach area). The external nose also receives blood from sinus opens. The ethmoidal bulla (L. bubble), a rounded first and arteries listed, plus nasal branches of the infra fifth elevation located superiorto the semilunar hiatus, is visible and the lateral nasal branches ofthe facial artery. orbital artery when the middle concha is removed. The bulla is formed by A rich submucosal venous plexus, deep to the nasal middle ethmoidal cells that form the ethmoidal sinuses. mucosa, providesvenous drainage of thenose via the spheno The inferiornasal meatus is a horizontal passage infero palatine, facial, and ophthalmic veins.The plexus is an impor lateral to the inferior nasal concha. The nasolacrimal duct, tant part of the body'sthermoregulatory system, exchanging which drains from the lacrimal sac,opens into the ante tears heat and warming air before it enters the lungs. Venous blood rior part of this meatus (see Fig. 7.46A, p. 892). The com from the external nose drains mostly into the facial vein ia mon nasal meatus is the medial part of the nasal cavity the angular and lateral nasal veins (see Fig, 7.25). However, between the conchae and the nasal septum, into which the recall that it lies within thedanger area"ofthe face because lateral recesses and meatus open. of communications with the cavernous (dural venous) sinus (seethe blue box "Thrombophlebitis of Facial Vein," p. 875). Vasculature and Innervation of Nose Regarding its nerve supply ofthe nose, thenasal mucosa can be divided into postero-inferior and anterosuperior portions The arterial supply of the medial and lateral walls of the by an oblique line passing approximately through the ante nasal cavity (Fig. 7.105) is from five sources: rior nasal spine and thespheno-ethmoidal recess (Fig.7.106). The nerve supply of the postero-inferior portion the nasal of 1. Anteriorethmoidal artery (from the ophthalmic artery). mucosa is chiefly from the maxillary nerve, by way of the 2. Posteriorethmoidal artery (from the ophthalmic artery). nasopalatinenerve to the nasal septum,and posterior supe 3. Sphenopalatine artery (from the maxillary artery). rior lateral nasal and inferior lateral nasal branches of the 4. Greater palatineatery (from the maxillary artery). greaterpalatinenerve to the lateral wall. The nerve supply 5. Septalbranch of thesuperior labial artery (from the facial of the anterosuperiorportion is from the ophthalmic nerve artery). (CN V) by way the anterior and posterior ethmoidal of The first three arteries divide into lateral and medial (septal) nerves, branches of the nasociliary nerve. Most of the exter branches. The greater palatine artery reaches the septum nal nose (dorsum and apes) is also supplied by CN V, (via via the incisive canal through the anterior hard palate. The the infratrochlear nerve and the external nasal branch of the anteriorethmoidal nerve),but the alae of thenose are sup in the median plane. The frontal sinuses vary in size from pliedby the nasal branches ofthe infra-orbital nerve (CN V,). approximately 5 mm to large spaces extending laterally into The olfactory nerves,concermed with smell,arise from cells the greaterwings of the sphenoid. Often a frontal sinus has in the olfactory epithelium in the superior part of the lat two parts: a vertical part in the squamous part of the frontal eral and septal walls of the nasal cavity. The central processes bone,and a horizontalpart in the orbital part of the frontal of these cells (forming the olfactory nerve) pass through the bone. One or both parts may be large or small. When the cribriform plate and end in the olfactory bulb, the rostral supra-orbital part is large, its roof forms the ffoor theante of rior cranial fossa and its floor forms the roof of the orbit. expansion of theolfactory tract (Fig.7.102A). Paranasal Sinuses ETHMOIDAL CELLS The paranasal sinuses are air-filled extensionsof the respi The ethmoidal cells (sinuses)are small invaginations of the ratory partof the nasal thefollowingcranial bones: cavity into mucous membrane ofthe middle and superior nasal meatus into frontal, ethmoid, sphenoid, and maxilla. They are named the ethmoid bone between the nasal cavity and the orbit (Figs. according to the bones in which they are located. The sinuses 7.104, 7.107, and 7.10S). The ethmoidal cells usually arenot visi continue to invade the surrounding bone, and marked exten ble in plain radiographsbefore 2years of agebut arerecognizable sions are common in the crania of older individuals. in CT scans. The anteriorethmoidal cells drain directly or indi rectly into the middle nasal meatus through theethmoidal infun FRONTAL SINUSES dibulum. The middle ethmoidal cells open directly into the middle meatus and are sometimes called "bullar cells because The right and left frontalsinuses are between the outer and they form theethmoidalbulla, a swelling on the superiorborder inner tables of the frontal bone, posterior to the superciliary of the semilunarhiatus (Fig. 7.103B).The posteriorethmoidal arches and the root of the nose (Figs. 7.103,7.104,and 7.107). cells open meatus.The ethmoidalcells directly into the superior Frontal sinuses are usually detectable in children by 7 years of are supplied by and posterior ethmoidalbranches of the anterior age.The right and left each drain through a frontonasal sinuses the nasociliary nerves (CN V) (Figs. 7.19 and 7.106). duct into the ethmoidal infundibulum,which opens into the semilunarhiatus themiddle nasal meatus.The frontal sinuses of SPHENOIDAL SINUSES areinnervatedby branches of the supra-orbital nerves (CN V). The right and left frontal sinuses are rarely of equal size, The sphenoidal sinuses are located in the body of the and the septum between them is not usually situated entirely sphenoid, but they may extend into the wings this bone of 990/1170 (Figs. 7.103 and 7.107). They are unevenly divided and sepa posterior ethmoidal cell that begins to invade the sphenoid at rated by a bony septum. Because of this extensive pneuma approximately2years ofage.In some people,several posterior tization (formation of air cells), the body of the sphenoid is ethmoidal cells invade the sphenoid, giving rise to multiple fragile. Only thin plates of bone separate the sinuses from sphenoidal sinuses that open separately into the spheno severalimportant structures: the optic nerves and optic chi ethmoidal recess (Fig.7.103A).The posteriorethmoidal arter asm, thepituitary gland,the internal carotid arteries, and the ies and the posteriorethmoidal nerves that accompany the cavernous sinuses. The sphenoidal sinuses are derived from a arteries supply the sphenoidal sinuses(Fig.7.105). 991/1170  Chapter 7 Head 963 MAXILLARY SINUSES particularly the first two molars, often produce conical elevations in the floor of the sinus. The maxillary sinuses are the largest oftheparanasalsinuses. They occupy the bodies ofthe maxillae and communicate with Each maxillary sinus drains by one or more openings, the the middle nasal meatus (Figs. 7.104, 7.107, and 7.108). maxillary ostium (ostia), into the middle nasal meatus of the nasal cavity by way of the semilunar hiatus. The apex of the maxillary sinus extends toward and often The arterial supply of the maxillary sinus is mainly into the zygomatic bone. from superior alveolar branches of the maxillary artery The base of the maxillarysinus forms the inferior part of (Fig. 7.73; Table 7.12); however, branches of the descending the lateral wall of the nasal cavity. and greaterpalatine arteries supply the Hoor ofthe sinus (Figs. The roofof the maxillary sinus is formed by the floor of 7.98B). Innervation of the maxillary sinus is from the the orbit. anterior, middle, and posterior superior alveolar nerves, The floor of the maxillary sinus is formed by the alveo which are branches of the maxillary nerve (Fig. 7.79A). lar part of the maxilla. The roots of the maxillary teeth, THE NOSE epistaxis (bleedingfrom the nose)usually occurs. In severe frac tures, disruption of the bones and cartilages results in displace Nasal Fractures ment of the nose.When the injury results froma direct blow,the cribriforn plate ofthe ethmoid bone may also fracture. Because of the prominence of the nose, fractures of the nasal bones are common in automobile accidents and contact sports (unless face guards are worn). Deviation of Nasal Septum Fractures usually result in deformation ofthe nose,particularly The nasal septum is usually deviated to one side or when a lateral force is applied by someone's elbow, for example; the other (Fig. B7.40).This could be the result of a birth injury, but more often the deviation occurs during adolescence and adulthood from trauma (e.g, during a fist fight). Sometimes the deviation is so severe that the nasal septum is in contact with the lateral wall of the nasal cavity and often obstructs breathing or exacerbates snoring, The deviation can be corrected surgically. Nasal septum deviated to left side Anterior view, CT scan Inferior view,MRI FIGUREB7.40. Deviated nasal septum. 993/1170 20 Cha Head Rhinitis superomedial walls (Fig. 7.108). When the mucous mem brane the sinus is congested,the maxillary ostia areoften of The nasal mucosa becomes swollen and inflamed obstructed. Because of the high location of the ostia, when (rhinitis) during severe upper respiratory infections the head is erect it is impossiblefor the sinuses to drain and allergic reactions (e.g, hayfever). Swelling of the until they are full. Because the ostia of the right and left mucosa occurs readily because of its vascularity. Infections of sinuses lie on the medial sides (i.e., are directed toward the nasal cavities may spread to the: each other), when lying on one's side only the upper sinus Anterior cranial fossa through the cribriform plate. (e.g. the right sinus if lying on the left side) drains. A cold Nasopharynx and retropharyngeal soft tissues. or allergy involving both sinuses can result in nights of roll. Middle ear through the pharyngotympanic tube (auditory ing from side to side in an attempt to keep the sinuses tube), which connects the tympaniccavity and nasopharynx. drained. A maxillary sinus can be cannulatedand drained by Paranasal sinuses. passing a cannula from the naris through the maxillary ostium into the sinus. Lacrimalapparatusand conjunctiva. Epistaxis Relationship of Teeth Epistaxis (nosebleed) is relativelycommon because of to Maxillary Sinus the rich blood supplyto the nasal mucosa. In most The close proximity of the three maxillary molar cases, the cause is traumaand the bleeding is from an teeth to the floor of the maxillary sinus poses poten area in the anterior third of the nose (Kiesselbach area tially serious problems.During removal of a mail Fig, 7.105B).Epistaxis is also associated with infections and lary molar tooth, a fracture of a root of the tooth may occur. hypertension. Spurting of blood from the nose resultsfrom If proper retrieval methods are not used, a piece of the root rupture of arteries. Mild epistaxis may also result from nose may be driven superiorly into the maxillary sinus. A commu picking, which tears veins in the vestibule ofthe nose. nication may be created between the oral cavity and the max illary sinus as a result, and an infection may occur. Because Sinusitis the superior alveolar nerves (branchesofthe maxillary nerve) supply both the maxillary teeth and the mucous membrane Becausethe paranasal sinuses are continuous with the of the maxillary sinuses, inflammation of the mucosa of the nasal cavities through apertures that open into them, sinus is frequently accompanied by a sensation oftoothache infection may spread from the nasal cavities, produc in the molar teeth. ing inflammation and swelling of the mucosa of the sinuses (sinusitis) and local pain. Sometimes several sinuses are inflamed Transillumination of Sinuses (pansinusitis),and the swelling of the mucosamay block one or more openings ofthe sinuses into the nasal cavities. Transillumination of the maxillary sinuses is per formed in a darkenedroom.A bright light is placed in Infection of Ethmoidal Cells the patient's mouth on one side of the hard palate or firmly against the cheek (an in Fig. B7.41A). The light passes If nasal drainage is blocked, infections of the eth through the masillary sinus and appearsas a crescent-shaped, moidalcells may break through the fragile medial wall dull glow inferior to the orbit. Ifa sinus contains excess fluid, a of the orbit. Severe infections from this source may mass, or a thickened mucosa,the glow is decreased. The frontal cause blindness because some posterior ethmoidal cells lie sinuses can also be transilluminated by directing the light supe close to the optic canal, which gives passage to the optic nerve riorly under the medial aspect of the eyebrow, normally pro and ophthalmicartery. Spread of infection from these cells ducing a glow superior the orbit (Fig, B741B). Because of to could also affect the dural sheath of the optic nerve, causing the great variation in the development of the sinuses, the pat optic neuritis. tern and extent of sinus illumination differs from person to per son (Swartz, 2009). Infection of Maxillary Sinuses The maxillary sinuses are the most commonly infected,probably because their ostia (openings) are commonly small and are located high on their VISCERA OF THORACIC CAVITY (Fig. 1.30A). The thoracic cavity is divided into three com partments (Figs. 1.30A & C): When sectioned transversely, it is apparent that the thoracic Right and left pulmonary cavities, bilateral com cavity is kidney shaped: a transversely ovoid space deeply partments that contain the lungs and pleurae (lining indented posteriorly by the thoracic vertebral column membranes) and occupy the majority of the thoracic and the heads and necks of the ribs that articulate vwith cavity. it 136/1170 Chapter Thorax 107 1 Cervical pleura Trachea -Cervical pleura 7 8 Bronchial tree (representing root of lung) Costal part Costal pleura Costal surface of left lung Pleural covered with cavity visceral pleura Visceral Cardiac notch pleura Mediastinal part Lingula -Diaphragmatic part Transverse CT scan Sternum 7 Right pulmonary cavity 1 Costodiaphragmatic 2 Vertebral body 8 pulmonary Left cavity recesses 9 Mediastinum t 3-6 Ribs (A)Inferior views (B) Anterior view Layers Collapsed lung Hilum of lung (site of Inflated lung Visceral pleura entry of root of lung) Parietal pleura -Suprapleural membrane Costal pleura Pleural cavity Cervical pleura Diaphragmatic pleura Mediastinal pleura Mediastinal Cervical pleura Collapsed lung part Fascial membranes Visceral pleura Costal part (Suprapleural and mediastinal fascia, fibrous pericardium) Parietal Endothoracic fascia pleura Parts of parietal pleura Thoracic wall lined with endothoracic fascia Parts of Diaphragmatic part parietal pleura Endothoracic fascia Phrenico Mediastinum Visceral pleura pleural fascia (contains heart) (part of Diaphragm endothoracic fascia) The right and left pulmonary cavities, separated by the mediastinum, are lined with parietal pleura that reflects onto the lungs as visceral pleura. (C) Anterior view FIGURE1.30. Divisions of thoracic cavity and lining of pulmonary cavities. A. The CT scan and interpretive diagram above are transverse cross it sectional views of the thoracic cavity demonstrating kidney-like shape, resulting from the protruding vertebral bodies, and division into three compart its ments. The dimensional (B)and coronal cross-sectional (C) diagrams demonstrate the linings of the pleural cavities and lungs (pleurae). Each lung is invested by the inner layer of a closed sac that has been invaginated by the lung. Inset: A invaginating an underinflated balloon demonstrates the fist relationship of the lung (represented by the to walls of the pleural sac (parietal and visceral layers of pleura). fist) 137/1170 108 Chapter Thorax 1 A central mediastinum, a compartment intervening when the thorax expands while still allowing sliding to occur, between and completely separating the two pulmonary much like a film of water betweentwo glass plates. cavities, which contains essentially all other thoracic The visceral pleura (pulmonarypleura) closely cov structures- the heart, thoracic parts of the great ves ers the lung and adheres to all its surfaces, including those sels, thoracic part of the trachea, esophagus, thymus, and within the horizontal and oblique fissures (Figs. 1.30B & C other structures (e.g., lymph nodes). It extends vertically and 1.31A). In cadaver dissection,the visceral pleura cannot from the superior thoracic aperture to the diaphragm and usually be dissected from the surface of the lung. It provides anteroposteriorly from the sternum to the thoracÍc verte the lung with a smooth slippery surface, enabling it to move bral bodies. freely on the parietal pleura. The visceral pleura is continu ouswith the parietal pleura at the hilum ofthe lung, where structures making up the root of thelung (e.g,, bronchus and Pleurae, Lungs, and pulmonaryvessels)enter and leave the lung (Fig. 1.30C). Tracheobronchial Tree The parietal pleuralines the pulmonarycavities, thereby Each pulnonary cavity (right and left) is lined by a peu adhering to the thoracic wall, mediastinum, and diaphragm. ral membrane (pleura) that also reflects onto and cov It is thicker than the visceral pleura, and during surgery and cadaver dissections,it may be separated from the surfaces it ers the external surface of the lungs occupying the cavities (Fig. 1.30B & C). To visualize the relationship of the pleu covers. The parietal pleura consists of three partscostal, rae and lungs, push your fist into an underinflated balloon mediastinal, and diaphragmatic- -andthe cercical plura. (Fig.1.30C). The inner part of the balloon wall (adjacent to The costal part of the parietal pleura (costovertebral your fist, which represents the lung), is comparable to the or costal pleura) covers the internal surfaces of the thoracic visceral pleura; the remaining outer wall of the balloon rep wall (Figs. 1.30B &C and 1.32). separated from the It is internal surface of the thoracic wall (stemum,ribs and costal resents the parietalpleura. The cavity between the layers of the balloon, here illed with air, is analogous to the pleural cartilages, intercostal muscles and membranes,and sides of thoracic vertebrae) by endothoracic fascia. This thin, extra cavity, although the pleural cavity contains only a thin film of pleural layer of loose connective tissue forms a natural cleav fluid.At your wrist (representing the root of the lung), the inner and outer walls of the balloon are continuous, as are ageplane for surgical separation of the costal pleura from the thoracic wall (see the blue box "Extrapleural Intrathoracic the visceral and parietal layers of pleura, together forming a pleural sac. Note that the lung is outside of but surrounded Surgical Access," p. 96). by the pleural sac,just as your fist is surrounded by but out The mediastinal part of the parietal pleura(media side of the balloon. stinal pleura) covers the lateral aspects of the mediastinum, the partition of tissues and organs separating the pulmonary The inset in Figure 1.30C is also helpful in understand ing the development of the lungs and pleurae. During the cavities and their pleural sacs. It continues superiorly into the root of the neck as cervical pleura. It is continuous with costal embryonic period, the developing lungs invaginate (grow into) the pericardioperitoneal canals, the precursors of pleura anteriorlyand posteriorly, and with the diaphragmatic the pleural cavities. The invaginated coelomic epithelium pleura inferiorly. Superior to the root of the lung, the medi pleura is a continuous sheet passing anteroposteriorly astinal covers the primordia of the lungs and becomes the visceral betweenthe sternum and the vertebral column. At the hilum pleura in the same way that the balloon covers your fist. The epithelium lining the walls of the pericardioperitoneal canals of the lung, it is the mediastinal pleura that reflects laterally onto the root of the lung to become continuous with the vis forms the parietal pleura. During embryogenesis, the pleural cavities become separated from the pericardial and perito ceral pleura. neal cavities. The diaphragmaticpart of the parietal pleura (dia phragmatic pleura)covers the superior (thoracic)sufaceof PLEURAE the diaphragm on each side of the mediastinmum, except along its costal where the diaphragm is attachments (origins)and Each lung is invested by and enclosed in a serous pleural fused to the pericardium, membrane sur the fibroserous sacthat consists of two continuous memnbranes: the visceral rounding the heart (Figs. 1.30B & Cand 1.32). A thin,mnore pleura, which invests all surfaces of the lungs forming their elastic layer of endothoracic fascia, the phrenicopleural shiny outer surface, and the parietalpleura, which lines the fascia, connects the diaphragmatic pleura with the muscular pulmonarycavities (Fig. 1.30B & C). fibers of the diaphragm (Fig. 1.30C). The pleural cavity -thepotential space between the lay The cervical pleura covers the apex of the lung (the ers of pleura -contains a capillary serous pleural layer of part of the lung extending superiorly through the superior fluid, which lubricates the pleural surfaces and allows the thoracic aperture into the root of the neck -Figs. 1.30B & layers of pleura to slide smoothly over each other during res Cand 1.31A). It is a superior continuation of the costal and piration. The surface tension of the pleural fuid provides the mediastinal parts of the parietalpleura. The cervical pleura cohesion that keeps the lung surface in contact with the tho forms a cup-like dome (pleural cupula) over the apex racie wall, consequently, the lung expands and fills with air that reaches its summit 2-3 cm superior to the level of the medial third of the clavicle at the level of the neck of the lst The relatively abrupt lines along which the parietal pleura rib. The cervical pleura is reinforced by a fibrousextension changes direction as it passes (reflects) from one wallof the of the endothoracie fascia, the suprapleural membrane pleural cavity to another are the lines ofpleural reflection (Sibson fascia). The membrane attaches to the internal bor (Figs.1.3l and 1.32). Three lines of pleural reflection out der of the lst rib and the transverseprocess of C7 vertebra line the extent of thepulmonary cavities on each side: ster (Fig. 1.30C). nal, costal, and diaphragmatic. The outlines of the right and 139/1170 leftpulmonary cavities are asymmetrical (i.e., are not mir The costal lines of pleural reflection are sharp contin ror images of each other) because the heart is turned and uationsof the sternal lines, occurring where the costal pleura extends toward the left side, imposing on the left cavity more becomes continuous with diaphragmatic pleura inferiorly. markedly than on the right. The right costal line proceeds laterally from the AML. How Deviation of the heart to the left side primarily affects the ever, because of the bare area of pericardium on theleft side, right and left sternal ines of pleural refection, which the left costal line begins at the midclavicularline; otherwise, are asymmetrical.The sternal lines are sharp or abrupt and the right and left costal lines are symmetrical as they proceed occur where the costal pleura is continuous with the medias laterally. posteriorly, and then medially,passing obliquely pleura anteriorly. Starting tinal superiorly from the cupulae across the Sth rib in the midclavicularline (MCL)and the (Fig,l.31A), the right and left lines of stemal reflection run 10th rib in the midaxillary line (MAL), becoming continu inferomedially,passing posterior tothestermoclavicular joints ous posteriorly with the vertebral lines at the necks of the to meet at the anteriormedian line (AML), posterior to the 12th ribs inferior to them. sternum at the level of its sternal angle. Between the levels of The vertebral lines of pleural reflection are much costal cartilages 2-4, the right and left lines descend in con rounder, gradual reflectionsand occur where the costal tact. The pleural sacs may even slightly overlapeach other. pleura becomes continuous with the mediastinalpleura pos The sternal line of pleuralreflection on the right side con teriorly. The vertebral lines of pleural reflection parallel the tinues to pass inferiorly in the AML to the posterior aspect of vertebral column, running the paravertebralplanes from in the xiphoid process (level of the 6th costal cartilage), where vertebral level Tl through T12,where they become continu it turns laterally (Fig. 1.31). The sternal line of reflection on ous with the costal lines. the left side, however, descends in the AML only to the level The lungs do not fully occupythepulmonary cavities dur of the 4th costal cartilage. Here it passes to the left margin ing expiration; thusthe peripheral diaphragmatic pleura is of thestermum and continues inferiorly to the 6th costal car in contact with the lowermost parts of the costal pleura.The tilage, creating a shallow notch as it runs lateral to an area potential pleural spaces here are the costodiaphragmatic of direct contact between the pericardium (heart sac) and recesses, pleura-lined "gutters," which surround the the anteriorthoracic wall. This shallow notch in the pleural upward convexity of the diaphragm inside the thoracicwll sac, and the bare area" of pericardial contact with the ante (Figs. 1.30B, 1.32, and 1.33C). Similar but smaller pleural rior wall, are important for pericardiocentesis (see blue box, recesses are located posterior to the sternum where the "Pericardiocentesis," later in this chapter). costal pleura is in contact with the mediastinal pleura.The 140/1170  Chapter1 Thorax 111 potential pleural spaces here are the costomediastinal into close relation with the venous blood in the pulmonary recesses. The left recess is larger (less occupied) because capillaries. Although cadavericlungs may be shrunken, firm the cardiac notch in the left lung is more pronounced than or hard, and discolored., healthy lungs in living people are the corresponding notch in the pleural sac. The inferior bor normally and spongy, and fully occupy the pul light, soft, ders of the lungs move farther into the pleural recesses dur monary cavities. They are also elastic and recoil to approxi ing deep inspiration and retreat from them during expiration mately one third their size when opened the thoracic cavity is (Fig. 1.33B & C). (Fig.1.30C).The lungs areseparated from each other by the mediastinum. Each lung has (Figs.1.33 and 1.34): LUNGS An apex, the blunt superior end of the lung ascending The lungs are the vital organs of respiration. Their main above the level of the lst rib into the root of the neck; the function is to oxygenate the blood by bringing inspired air apex is covered by cervical pleura.  Chapter 1 Thorax 113 A base, the concave inferior surface of the lung, opposite matic surface is bounded by a thin, sharp margin (inferior the apex, resting on and accommodatingthe ipsilateral border) that projects into the costodiaphragmatic recess of dome the diaphragm. the pleura (Figs. 1.33C and 1.34). of Two or three lobes, created by one or two fissures. The anterior border of the lung is where the costal Threesurfaces (costal, mediastinal, and diaphragmatic). and mediastinal surfaces meet anteriorly and overlap the Three borders (anterior, inferior, and posterior). heart. The cardiac notch indents this border of the left lung, The border of the lung circumseribes the dia inferior The right lung features right oblique and horizontal fis phragmatic surface of the lung and separates this surface sures that divide it into three right lobes: superior, mid from the costal and mediastinal surfaces. The posterior dle, and inferior. The right lung is larger and heavier than border of the lung is where the costal and mediastinal the left, but it is shorter and wider because the right dome surfaces meet posteriorly; it is broad and rounded and lies in of the diaphragm and the heart and pericardium is higher the cavity at the side of the thoracic region of the vertebral bulge more to the The anterior border of the right lung left. column. is relatively straight. The left lung has a single left oblique The lungs are attached to the mediastinum by the roots fissure dividing it into two left lobes, superiorand infe of the lungsthat is, the bronchi (andassociated bronchial rior. The anterior border of the left lung has a deep car vessels), pulmonaryarteries, superior and inferior pulmo diac notch, an indentation consequent to the deviation of nary veins, the pulmonaryplexuses of nerves (sympathetic, the apex of the heart to the left side. This notch primarily parasympathetic, and visceral afferent fibers), and lymphatic indents the antero-inferior aspect of the superior lobe. This vessels (Fig. 1.34). If the lung root is sectioned before the indentation often shapes the most inferior and anterior part (medial to) branching of the main (primary) bronchus and of the superior lobe into a thin, tongue-like process, the lin pulmonary artery, its general arrangement is gula (L. dim. of lingua, tongue), which extends below the cardiac notch and slides in and out of the costomnediastinal Pulmonary artery: superiormost on left (the superior recess during inspiration and expiration (Figs. 1.30B, 1.31A, lobar or "eparterial"bronchus may be superiormost on the right). and 1.34C). The lungs of an embalmed cadaver, usually firm to the Superior and inferior pulmonaryveins: anteriormost and inferiormost, respectively. touch, demonstrate impressions formed by structures Main bronchus: against and approximately in the middle adjacent to them, such as the ribs, heart, and great vessels (Figs. 1.33A and 1.34A & C). These markings provide clues of the posterior boundary, with the bronchial vessels to the relationships of the lungs; however, only the cardiac coursing on its outer surface (usually on posterior aspect at this point). impressions are evident during surgery or in fresh cadaveric or postmortem specimens. The hilum of the lung is a wedge-shaped area on the The costal surface of the lung is large, smooth,and mediastinal surface each lung through which the struc of convex. It is related to the costal pleura, which separates it tures forming the root of the lung pass to enter or exit the from the ribs, costal cartilages, and innermost intercostal lung (Fig. 1.34B & D). The hilum ("doorway") can be likened muscles (Fig. 1.33C). The posterior part the costal sur to the area of earth where a plant's roots enter the ground. of face is related to the bodies of the thoracic vertebrae and Medial to the hilum, the lung root is enclosed within the area is sometimesreferred to as the vertebral part of the costal of continuity between the parietal and the visceral layers of surface. pleura thepleural sleeve (mesopneumonium). The mediastinal surface of the lung is concave because Inferior to the root of the lung, this continuity between it is related the middle mediastinum, which contains the parietal and visceral pleura formsthe pulmonary ligament, pericardium and heart (Fig. 1.34). The mediastinal surface extending between the lung and the mediastinum, immedi includes the hilum, which receives the root of the lung. If ately anterior to the esophagus (Fig. 1.34A-D). The pulmo embalmed,there is a groove for the esophagus and a cardiac nary ligament consists of a double layer of pleura separated impression for the heart on the mediastinal surface of the by a small amount of connective tissue. When the root of right lung, Because two thirds of the heart lies to the left of the lung is severed and the lung is removed, the pulmonary the midline, the cardiac impression on the mediastinal sur ligament appears to hang from the root. To visualize the root face of the left lung is much larger. This surface of the left of the lung, the pleural sleeve surrounding it, and the pul lung also features a prominent, continuous groove for the monary ligament hanging from it, put on an extra-large lab arch of the aorta and the descending aorta as well as a smaller coat and abduct your upper limb. Your forearm is compa areaforthe esophagus (Fig. 1.34C). rable to the root of the lung, and the coat sleeve represents The diaphragmaticsurface of the lung, which is also the pleural sleeve surrounding it. The pulmonaryligament is concave, forms the base of the lung, which rests on the comparable to the slack of the sleeve as it hangs from your dome of the diaphragm. The concavity is deeper in the right forearm; and your wrist, hand, and abducted fingers repre lung because of the higher position of the right dome,which sent the branching structures of the root-the bronchi and overlies the liver. Laterally and posteriorly, the diaphrag pulmonary vessels. 114 Chapter Thorax TRACHEOBRONCHIAL TREE later in this chapter), located within the superior mediasti num, constitutes the trunk of the tree. It bifurcates at the Beginning at the larynx, the walls of the airway are sup level of the transverse thoracic plane (or sternal angle) into ported by horseshoe- or C-shaped rings of hyaline cartilage. main bronchi,one to each lung, passing inferolaterally to The sub-laryngeal airway constitutes the tracheobronchial enter the lungs at the hila (singular= hilum) (Fig, 1.35E). tree. The trachea (described with the superior mediastinum, Trachea Rightmain bronchus Left main bronchus Right superior. Left lobar (eparterial") superior lobar bronchus bronchus Right -Left Bronchialmiddle inferior tree lobar