Y1B6M1L1 Functional Anatomy of the Thoracic Wall and Cavity PDF

Y1B6M1L1 CARDIOVASCULAR SYSTEM, RESPIRATORY LECTURER: DR. A. RUFON SYSTEM, BLOOD & LYMPHATICS INTEGRATION JANUARY 15, 2024 | 3:00-5:00 FUNCTIONAL ANATOMY OF THE T...

Y1B6M1L1 CARDIOVASCULAR SYSTEM, RESPIRATORY LECTURER: DR. A. RUFON SYSTEM, BLOOD & LYMPHATICS INTEGRATION JANUARY 15, 2024 | 3:00-5:00 FUNCTIONAL ANATOMY OF THE THORACIC WALL AND CAVITY b. Subcostals TABLE OF CONTENTS c. Transversus Thoracis ○ Diaphragm – located OUTSIDE the thoracic cavity I. The Thorax IV. Thoracic Cavity → Separates the thoracic cavity from the abdominal A. How to Open the Chest A. The Diaphragm cavity. B. Thoracic Cage B. Structures that Make C. Muscles of the Thorax up the Thoracic Cage B. THORACIC CAGE D. Anatomical Landmarks V. Summary II. Thoracostomy vs VI. Review Questions Thoracentesis VII. References III. Pleural Effusion, Hemothorax, Pneumothorax I. THE THORAX A. HOW TO OPEN THE CHEST 1. If you are in a scenario where the skin was already removed, what structure will you cut? Muscle, bone, cartilage? ○ Muscle – cut when the skin is already removed 2. Where will you cut? Midline, Lateral, or Paramedian? ○ Depends on what structure you wish to see inside. → e.g. If you are to look into the chest cavity, and would like to see the heart, then you may open it through the Figure 1. The Thoracic Cage sternum via midsternal incision. Ribs Midsternal Incision – done to see the heart ○ Type of Bone: Flat ⎻ Can be performed in medical school with the ○ Rib 1-7 (7 ribs) - attached directly to the sternum through right instruments their respective costal cartilages ○ Mediastinum – 1st structure to be most likely ○ Rib 11-12 (2 ribs) - vertebral ribs (theoretically) seen during midsternotomy ○ Costal Cartilage - type of hyaline cartilage ○ If cutting from lateral to the midline, it will involve cutting 1. If you wanted to open the thoracic cage, how would you go through the cartilages. about it? Which particular parts of the cage will you approach → If you are able to open through the costal cartilages, and why? you are able to lift upward the sternum. ○ Parts to approach depend on the availability of equipment 3. Will you be able to open up the chest by lifting the sternum (and on what particular structure you wish to see) upward? → Sternum - utilizes median sternotomy to access the ○ Yes – because you have the muscle to do so (especially if mediastinum you are strong) and given that you’ve already cut it. → Ribs - cutting the ribs, along with the contents of the 4. Why can you fracture the ribs if you open the chest? intercostal spaces, at the midaxillary line is essential in ○ Angle of the rib – thinnest and weakest part removing the anterior thoracic wall, which is needed to 5. If you will be able to open the chest by fracturing the ribs, will view the contents of the thoracic cavity you still be able to open the chest by lifting the anterior part of the rib cage superiorly? ○ Yes, it can be lifted. You can open the chest in many different ways depending on what particular structures you want to look at and what you wish to preserve. ○ If you lift the chest cavity superiorly, several blood vessels might be cut, unless you are careful enough. SURFACE ANATOMY Ribs - 12 pairs ○ Thoracic Vertebrae - 12 ○ Muscles that form the Thoracic Cage a. Intercostals External Internal Innermost Figure 2. Posterior View of the Thoracic Cage 🔊🗃️ MG 7 | MG 8 1 of 7  Y1B6M1L1: FUNCTIONAL ANATOMY OF THE THORACIC WALL AND CAVITY X-RAY VIEWS: POSTEROANTERIOR VS. ANTEROPOSTERIOR Posteroanterior View ○ Film is on the anterior part and the patient is hugging it. ○ Scapula - at the sides Anteroposterior View ○ Scapula - at the center PECULIARITIES OF THE THORACIC VERTEBRAE Size: Medium Shape: Heart Vertebral Foramen: Small and circular Spinous process: Long and inferiorly inclined (+) Costal facets on each side (EXCEPT for T11 and T12) ○ Flat facets that face: → Posteriorly and laterally on superior articular Figure 5. Posterior view of the Sternum processes → Anteriorly and medially on inferior articular processes When looking at the thoracic wall, it is also important to (-) Transverse foramen consider the nerve and blood supply of the muscles. Neurovascular Bundle – most likely to be encountered Lecturer notes/Nice-to-Know: ○ Located in the posteroinferior part of the ribs What are the peculiarities of the shoulder joint? ○ The superior part of the rib is more rounded and then ○ Most mobile joint in the body tapers off inferiorly to accommodate the neurovascular ○ Type of Joint: Synovial ball-and-socket joint bundle. → Serves as a guide during thoracotomy tube insertions C. MUSCLES OF THE THORAX and thoracentesis The Intercostals D. ANATOMICAL LANDMARKS ○ 3 Types: External, Internal and Innermost Subcostals 1. Lines Transversus Thoracis 2. Angles Muscles that do not comprise the thoracic wall, but are 3. Areas attached to it: ○ Pectoralis major ○ Pectoralis minor ○ Serratus anterior ○ Scalene muscles Figure 6. Surface Landmarks of the Chest LINES OF ORIENTATION Figure 3. Oblique view of the thoracic cage Table 1. Lines of Orientation LINE DEFINITION Midsternal Line Lies in median plane over sternum Midclavicular Line Runs vertically downward from the midpoint of the clavicle Anterior Axillary Line Runs vertically downward from the anterior axillary fold Posterior Axillary Line Runs vertically downward from the posterior axillary fold Figure 4. Anterior view of the ribcage MG 7 | MG 8 2 of 7  Y1B6M1L1: FUNCTIONAL ANATOMY OF THE THORACIC WALL AND CAVITY LINE DEFINITION Try not to open the abdomen when dissecting the chest. ○ As a guide, make sure that you do NOT enter the Midaxillary Line Runs vertically downward from a diaphragm. point situated midway between Tip of Scapula - important landmark the anterior and posterior axillary folds Scapular Line Runs vertically downward on the posterior wall of the thorax, passing through the inferior angle of the scapula (arms at the sides) Parasternal Line Midway between the midsternal and mammary lines Paravertebral Line Along the tips of the vertebral transverse processes SURFACE LANDMARKS OF THE ANTERIOR CHEST WALL Suprasternal Notch – the superior margin of the manubrium sterni Figure 8. Lines of pleural reflection ○ Lies opposite the lower border of the body of the 2nd thoracic vertebra The whole lung tissue does NOT fill up the chest cavity. Sternal Angle (Angle of Louis) – the angle made between the There are areas where tubes can be inserted or placed without manubrium and the body of the sternum fear of injuring the lung tissue. ○ It lies opposite the intervertebral disc between the 4th and 5th thoracic vertebra. II. THORACOSTOMY VS THORACENTESIS ○ All ribs may be counted from this point. Table 2. Difference Between Thoracentesis and Thoracostomy ○ The finger moved to the right or to the left will pass directly onto the 2nd costal cartilage and then the 2nd rib. DEFINITION Xiphisternal Joint – the joint between the xiphoid process and the body of the sternum Involves the insertion of a needle to ○ Lies opposite the body of the 9th thoracic vertebra Thoracentesis evacuate some amounts of fluid inside Subcostal Angle – situated at the inferior end of the sternum the thoracic cavity between the sternal attachments of the 7th costal cartilages Costal Margin – the lower boundary of the thorax and is Done when it is anticipated that a formed in: relatively long time is needed to Thoracostomy ○ Front: by the cartilages of the 7th, 8th, 9th and 10th ribs evacuate the contents of the thoracic ○ Behind: by the cartilages of the 11th and 12th ribs cavity ○ 10th rib - forms the lowest part of the costal margin Clavicle – subcutaneous throughout its entire length and can be easily palpated THORACENTESIS Figure 7. Posterior Landmarks of the Chest Figure 9. Thoracentesis MG 7 | MG 8 3 of 7  Y1B6M1L1: FUNCTIONAL ANATOMY OF THE THORACIC WALL AND CAVITY Figure 13. Thoracentesis needle-catheter device with 3-way stopcock. Figure 10. Cannula used in Thoracentesis At present, insertion of cannula during thoracentesis is aided with the use of ultrasound, but traditional methods like finger percussion were commonly utilized in the past. ○ Percussion Method → Using finger percussion to locate the dull sounding area to guide the practitioner where to inject the cannula. → Presence of fluid in the transparent compartment of the cannula lets you know that you inserted it correctly at the right place. Figure 14. Chest tube ○ Ultrasound Guidance - make thoracentesis no longer difficult to perform. Figure 15. Pleural Effusion showing Chest tube and Drainage Bottle Figure 11. Different Gauges Cannula During pleural effusion, make sure that: Cannula Gauges: ○ One end of the drainage bottle (attached to chest tube) is ○ Pink - 20G submerged or is located BELOW the fluid surface to ○ Green - 18G prevent pneumothorax ○ Grey - 16G ○ Other end tube of the drainage bottle should be ABOVE the fluid line, which serves in maintaining the negative pressure. Pneumothorax - air gets inside your chest cavity Figure 12. 3-way Stopcock 3-way Stopcock - used for regulation of fluid coming out of Figure 16. Different Sizes of Chest tubes: Bigger tubes - used to the chest. evacuate fluid; Smaller tubes - used to evacuate air MG 7 | MG 8 4 of 7  Y1B6M1L1: FUNCTIONAL ANATOMY OF THE THORACIC WALL AND CAVITY In evacuating a relatively small amount of fluid, a maximum of 200 cc per evacuation only and should be closed after, to prevent rebound hemothorax. ○ Rebound Hemothorax - occurs when the blood vessels in the chest dilate rapidly due to the accelerated evacuation of the fluid (e.g. evacuating 500 cc of fluid) inside the chest → The rapid dilation (due to the loss of pressure exerted by the fluid) will most likely lead the blood vessels to burst. ○ Thus, evacuating only as much as 200 cc of fluid per hour is recommended. → e.g. If the patient has 500 cc of fluid, evacuate the 400 cc during the first 2 hours. Then, it is advised to have a chest tube insertion (where you can regulate the evacuation of the remaining fluid) since it is hard to maintain the needle in place for such a long time. III. PLEURAL EFFUSION, HEMOTHORAX, PNEUMOTHORAX Table 3. Difference of Pleural Effusion, Hemothorax, & Pneumothorax DEFINITION Figure 17. One-bottle drainage system Pleural Effusion Accumulation of serous fluid in the pleural When you inhale, air from outside will also flow inside the cavity other tube. ○ So, if you are doing the assembly of your thoracostomy Hemothorax Accumulation of blood in the pleural cavity bottle, one end which is attached to your tube is submerged. Pneumothorax Accumulation of air within the pleural cavity Different Sizes of Chest Tubes: a. Bigger tubes – evacuate fluids (pus, blood, effusions) IV. THORACIC CAVITY b. Smaller tubes – evacuate air Tubes are usually placed at the 2nd intercostal When the chest is opened, the pericardium or pericardial space or superiorly, since air tends to move up. sac is seen surrounding the heart. 1. On which part of the chest should the needle and chest tube be inserted? ○ Usually placed at the midaxillary line. → (+) Discomfort if placed near the bed of the chest. ○ To evacuate fluid: → Needle and the chest tube should be inserted into the INFERIOR aspect of the chest. ○ To evacuate air: → Needle and the chest tube should be inserted into a more ANTERIOR aspect of the chest. Figure 19. Thoracic Cavity About Figure 19: ○ (1) Right lung - Middle lobe ○ (2) Thymus ○ (3) Pericardium ○ (4) Diaphragm muscle Figure 18. Position of the patient during thoracentesis MG 7 | MG 8 5 of 7  Y1B6M1L1: FUNCTIONAL ANATOMY OF THE THORACIC WALL AND CAVITY Figure 20. Thoracic Cavity Figure 22. Inferior View (Abdominal Surface) of the Diaphragm About Figure 20: ○ (1) Heart B. STRUCTURES THAT MAKE UP THE THORACIC CAGE ○ (2) Left lung - Upper lobe ○ (3) Right lung - Upper lobe 1. Sternum ○ (4) Mediastinum - between the right and left lung 2. Ribs 3. Thoracic vertebrae A. THE DIAPHRAGM Located at the floor of the thoracic cage Lecturer Notes: Major Structures that Pierce the Diaphragm: When dissecting the chest, try to consider preserving and ○ Esophagus locating the following: ○ Aorta ○ Internal mammary artery ○ Inferior vena cava ○ Phrenic nerve V. SUMMARY How to open the chest ○ Midsternal incision → Done to see the heart ○ Median sternotomy → Done to access the mediastinum ○ Fracturing the ribs → Done to view the contents of the thoracic cavity Angle of the rib - thinnest and weakest part Surface Anatomy ○ Ribs - 12 pairs ○ Thoracic vertebrae - 12 Muscles Forming the Thoracic Cage: ○ Intercostals (External, Internal, Innermost) ○ Subcostals Figure 21. Diaphragm ○ Transversus Thoracis Muscles that do not comprise the thoracic wall, but are Table 4. Major Structures that Pierce through the Diaphragm attached to it: STRUCTURE LEVEL ACCOMPANIED BY ○ Pectoralis major ○ Pectoralis minor Aortic Hiatus T12 → Aorta ○ Serratus anterior → Thoracic duct ○ Scalene muscles → Azygos vein Diaphragm - OUTSIDE the thoracic cavity; separates thoracic from abdominal cavity Esophageal T10 → Esophagus Thoracic Cage Hiatus → Right and left vagus nerve ○ Ribs - flat type of bone → Esophageal branches left → Rib 1-7 (7 ribs) - attached directly to the sternum gastric artery and vein through their respective costal cartilages → Lymphatics from lower → Rib 11-12 (2 ribs) - vertebral ribs third of the esophagus ○ Costal Cartilage - type of hyaline cartilage X-Ray Views of the Thoracic Cage Caval Hiatus T8 → Inferior vena cava ○ Posteroanterior View → Branches from right → Film is on the anterior part and the patient is hugging it. phrenic nerve → Scapula - at the sides MG 7 | MG 8 6 of 7  Y1B6M1L1: FUNCTIONAL ANATOMY OF THE THORACIC WALL AND CAVITY ○ Anteroposterior View D. Head → Scapula - at the center 2. The following are muscles that do not comprise the chest wall Anatomical Landmarks but attached to it, except: ○ Lines A. Pectoralis major → Midsternal, Midclavicular, Anterior Axillary, Posterior B. Serratus anterior Axillary, Midaxillary, Scapular, Parasternal, Paravertebral C. Pectoralis minor ○ Angles D. Serratus posterior ○ Areas Surface Landmarks 3. The following are structures that pierce the diaphragm except: ○ Suprasternal Notch A. Esophagus ○ Sternal Angle (Angle of Louis) B. Superior vena cava ○ Xiphisternal Joint C. Inferior vena cava ○ Subcostal Angle D. Aorta ○ Costal Margin 4. What do you call the accumulation of air within the pleural ○ Clavicle cavity? Thoracentesis - involves the insertion of a needle to evacuate A. Hemothorax some amounts of fluid inside the thoracic cavity. B. Pneumothorax Thoracostomy - a relatively long time is needed to evacuate C. Pleural Effusion the contents of the thoracic cavity 5. The neurovascular bundle is located _______ to the ribs. Neurovascular Bundle - located in the posteroinferior part of A. Posterosuperior the ribs B. Posteroinferior ○ Serves as a guide during thoracotomy tube insertions and C. Anterosuperior thoracentesis D. Anteroinferior Percussion method ○ Using finger percussion to locate the dull sounding area to 6. This procedure involves the insertion of a needle to evacuate guide the practitioner where to inject the cannula. some amounts of fluid inside the thoracic cavity. Ultrasound guidance - make thoracentesis no longer difficult A. Thoracostomy to perform. B. Paracentesis Cannula Gauges: C. Thoracentesis ○ Pink - 20G D. Paracolostomy ○ Green - 18G 7. Occurs when the blood vessels in the chest dilate rapidly due to ○ Grey - 16G the accelerated evacuation of the fluid 3-way Stopcock - used to regulate fluid coming out of the chest A. Pneumothorax During pleural effusion, one end of the drainage bottle B. Pleural effusion (attached to chest tube) is submerged or is located below the C. Rebound hemothorax fluid surface to prevent pneumothorax D. Pneumonia Bigger tubes - evacuate fluids (pus, blood, effusions) 8. What is the maximum volume of fluid to be evacuated to avoid Smaller tubes - evacuate air rebound hemothorax? The chest tube is usually placed at the midaxillary line. A. 100 cc To evacuate fluid, the needle and the chest tube should be B. 200 cc inserted into the inferior aspect of the chest. C. 250 cc To evacuate air, the needle and the chest tube should be D. 500 cc inserted into a more anterior aspect of the chest. Maximum of 200 cc of fluid to be evacuated is recommended 9. The following structures make up the thoracic cage, except: to prevent rebound hemothorax A. Diaphragm Rebound hemothorax - blood vessels in the chest dilate B. Sternum rapidly due to the accelerated evacuation of the fluid C. Ribs Pleural effusion - accumulated serous fluid in the pleural cavity D. Thoracic vertebrae Hemothorax - accumulation of blood in the pleural cavity 10. Which of the following pairs is mismatched? Pneumothorax - accumulation of air within the pleural cavity A. Aortic hiatus: T6 Diaphragm - located at the floor of the thoracic cage B. Esophageal hiatus: T10 Structures that pierce the diaphragm: C. Caval hiatus: T8 ○ Aorta D. ○ Esophagus ANSWERS: 1B, 2D, 3B, 4B, 5B, 6C, 7C, 8B, 9A, 10A ○ Inferior vena cava References: Structures that make up the thoracic cage: Dr. Rufon’s Lecture PPT (2024) ○ Sternum Snell’s Clinical Anatomy by Regions, 10th ed. ○ Ribs Dagitab Trans ○ Thoracic vertebrae VI. REVIEW QUESTIONS Trans Team: 1. What is the weakest part of the rib? MG 7: Alauig, Balleza, Calibjo, Herlandez, Llomo, Ollamina, A. Shaft Salisali, Salmorin, Villagracia, Villanueva B. Angle MG 8: Aranas, Borres, Bungay, Gabata, Labrador, Paniza, Rea, C. Tubercle Tupaz, Victoriano, Villavicencio MG 7 | MG 8 7 of 7