OAP Prelims: Thorax and Chest Cavity

Thoracic Cage Mechanism

• Thoracic cage is formed by sternum, ribs, and thoracic vertebrae
• Functions to protect organs in the thoracic cavity
• Divided into anterior (sternum), posterior (thoracic vertebrae), and lateral (ribs) parts

Ribs

• Typical ribs (2-12): long, twisted, flat bones with a rounded, smooth superior border and a sharp, thin inferior border
• Atypical rib (1st rib): small and flattened from above downward
• Costal cartilage: contributes to elasticity and mobility of the thoracic wall; calcification can occur due to calcium deposits

Thoracic Cavity

• Bounded by the thoracic wall and diaphragm
• Extends upward into the root of the neck, one fingerbreadth above the clavicle on each side
• Divided into medialistinum and two pleural cavities

Mediastinum

• Thick, movable partition between the lungs
• Divided into superior and inferior parts
• Has several divisions, including middle (heart and pericardium), anterior (body of sternum and spaces of pericardium), and posterior (T5-T12, heart, and pericardium) mediastinum

Diaphragm

• Dome-shaped, thin muscular and tendinous septum that separates the thoracic cavity from the abdominal cavity
• Origins: sternal, costal, and vertebral
• Functions to oxygenate blood; surrounded by a pleural cavity

Muscles of Respiration

• Inspiratory muscles: diaphragm, external intercostals, sternocleidomastoid, upper trapezius, pectoralis major and minor, anterior, middle, and posterior scalene, and serratus anterior
• Expiratory muscles: abdominal muscles, serratus posterior inferior, internal intercostals
• Forced expiration: sterocleidomastoid, upper trapezius, pectoralis major and minor, anterior, middle, and posterior scalene, and serratus anterior

Lungs and Pleural Cavity

• Lungs: located in the thorax, mediastinum; function to oxygenate blood
• Pleural cavity: protects and cushions the chest; has a thin layer; lies in the anterior wall of the chest cavity
• Pleural space: space between visceral and parietal pleura

Bronchopulmonary Segments

• Portion of the lung supplied by a segmental bronchus and its vessels
• Divisions of one lobe of a lung
• Right lung has 10 segments, left lung has 8 segments

Heart

• Located in mediastinum; 5-inch length, 3.5-inch width, 2.5-inch thickness; weighs 250g for women, 300g for men
• Layers: fibrous pericardium, parietal pericardium, epicardium, myocardium, endocardium

Chambers of the Heart

• Atrium: receiving chamber; right atrium receives blood from upper extremities
• Ventricle: pumping chamber; right ventricle pumps blood to the lungs
• Interventricular septum: divides ventricles of heart
• Atrioventricular valve: passage way between atrium and ventricle; prevents backflow

Heart Valves

• AV valves: right and left AV valves; chordae tendinae only attaches to AV valves
• Semilunar valve: between right ventricle and pulmonary artery, and left ventricle and aorta

Coronary Circulation

• Right coronary artery: divided into marginal branch and inferior/posterior interventricular branch
• Left coronary artery: divided into circumflex and anterior interventricular branch

This quiz covers the basics of the thorax region, chest cavity, and lungs. It explores the anatomy and structure of the thoracic cage and its components.