Cardiovascular Anatomy Quiz

Gross Anatomy of the Thorax

• The thorax is located between the root of the neck and abdomen.
• It protects the heart, lungs, and upper abdominal organs (liver, stomach, spleen).
• The subcutaneous fat can move over the underlying thoracic wall due to Scarpa's fascia.

Surface Markings

• Palpable bony prominences include:
  • T2: Superior angle of scapula
  • T2/T3: Upper border of manubrium sterni (suprasternal notch) - Trachea is palpable here.
  • T3: Spine of scapula
  • T4 (or 2nd costal cartilage): Sternal angle of Louis
  • T8: Inferior angle of scapula
  • T9: Xiphisternal junction (junction of body and xiphoid process of sternum)
• Spinous processes of thoracic vertebrae are palpable posteriorly, but the first palpable spinous process is C7.
• In males, the nipple usually lies at the level of the 4th intercostal space, but this position varies in females.
• The apex beat of the heart lies at the level of the 5th left intercostal space, 9cm from the midline.

Trachea and Thoracic Wall

• The trachea begins at the lower border of C6 and bifurcates at the sternal angle of Louis.
• The thoracic wall consists of the sternum, 12 ribs & costal cartilages, 12 thoracic vertebrae, muscles, vessels, and nerves.
• The sternum is made up of the manubrium, body, and xiphoid process.
• The manubrium has a jugular notch and clavicular notch for articulation with the clavicle. It fuses with the body at the sternal angle of Louis (T4 or 2nd rib).
• The body articulates with the 2nd-7th costal cartilage and xiphoid process at the level of T9 vertebra.
• The xiphoid process unites with the body after middle age.

Ribs

• There are 12 pairs of ribs.
• Ribs 1-7 are true ribs.
• Ribs 8-10 are false ribs.
• Ribs 11 and 12 are false floating ribs.
• Each rib is divided into head, neck, tubercle, and body (shaft). The 1st, 2nd, 10th, 11th, and 12th ribs are atypical ribs.

Thoracic Cavity

• The thoracic cavity is kidney-shaped and is bounded anteriorly by the sternum, posteriorly by the 12 thoracic vertebrae, laterally by the 12 ribs, and inferiorly by the thoracic diaphragm.
• The inlet is bounded by the manubrium sternum, T1 vertebra, and the 1st rib.
• The outlet is bounded by the xiphoid process, T12 vertebra, and the 11th and 12th floating ribs.

Cutaneous Vessels and Nerves

• Cutaneous veins do not run with the arteries, but receive blood from anastomosing collections that originate from the umbilicus.
• Above the umbilicus, the veins drain into the lateral thoracic vein and empty into the axillary vein.
• Cutaneous lymphatics run with the veins and drain into the axillary lymph nodes.
• Cutaneous nerves above the 2nd rib come from the C4 supraclavicular branch of the cervical plexus.
• Cutaneous nerves below the 2nd rib come from the anterior cutaneous branches of T2-L1 spinal nerves posteriorly.

Intercostal Space

• The intercostal space is the area between two ribs and contains intercostal muscles, nerves, and vessels.
• Intercostal muscles include external intercostal, internal intercostal, innermost intercostal, transversus thoracis, subcostalis, and levator costarum.
• The neurovascular bundle (vein, artery, and nerve) is located between the internal and innermost intercostal muscles, with the artery and nerve above the inferior rib.

Intercostal Nerves

• There are 12 pairs of thoracic nerves.
• Branches of intercostal nerves are lateral cutaneous branch, anterior cutaneous branch, and muscular branch.
• T1 and T2 nerves are atypical.
• T3-6 nerves are typical.
• The lateral cutaneous branch of T2 is called the intercostobrachial nerve

Intercostal Arteries and Veins

• The intercostal arteries arise from the internal thoracic artery and descending thoracic aorta.
• The superior intercostal artery arises from the costocervical trunk.
• The posterior intercostal arteries supply the posterior and lateral portions of the 2nd-11th intercostal spaces.
• Intercostal spaces are drained by anterior and posterior intercostal veins, arteries are accompanied by intercostal veins.
• Anterior intercostal vein accompanies the musculophrenic and internal thoracic arteries.
• Posterior intercostal veins accompany the posterior intercostal arteries.

Thoracic Diaphragm

• The diaphragm is a fibromuscular sheet between the thorax and abdomen.
• It is composed of muscular parts at the periphery and a trifoliate central tendon.
• It originates from the xiphoid process, the lower 6 costal cartilages, and the medial and lateral arcuate ligaments. Its insertion is into the central tendon.
• The crura of the diaphragm attach medially and laterally to the arcuate ligaments, with a larger right crus originating from the upper 3 lumbar vertebrae and a smaller left crus arising from the upper 2 or 3 lumbar vertebrae.
• The diaphragm has a pericardiophrenic ligament that connects the central tendon to the interior surface of the fibrous pericardium.
• Openings in the diaphragm include the vena caval opening at the level of T8, the esophageal opening at the level of T10, and the aortic opening at the level of T12.

Contents of the Thoracic Cavity

• The thoracic cavity contains the pleurae and lungs (laterally) and the mediastinum (connective tissue septum).

Pleura

• The pleura is a fibrous tissue that lines the lung and, consists of parietal and visceral layers.
• Parietal pleura lines the thoracic wall, diaphragm, and mediastinum and is attached to the suprapleural membrane.
• Costal pleura covers the internal surfaces of the sternum, costal cartilages, ribs, and intercostal muscles.
• Mediastinal pleura is continuous with costal pleura anteriorly, diaphragmatic pleura inferiorly, and the cupola (or apex) of the pleura superiorly.
• It encloses structures at the hilum of the lung, becomes a double-layered pulmonary ligament inferior to the hilum.
• Diaphragmatic pleura covers the superior surface of the diaphragm.
• Visceral pleura lines the surface of the lungs and the lobes.
• Between the parietal and visceral pleura is a potential space (pleural cavity) that contains pleural fluid.

Surface Marking of the Pleura

• Lines of pleural reflections occur where costal pleura becomes continuous with the mediastinal pleura anteriorly and the diaphragmatic pleura inferiorly.

Lungs

• Lungs are respiratory organs that oxygenate mixed venous blood.
• They are conical, soft, spongy, and elastic, typically pinkish in healthy individuals and darker in city dwellers due to dust particles.
• The right lung weighs approximately 600g, while the left weighs around 550g when filled with air.
• Lungs are connected to the mediastinum via bronchi and pulmonary vessels at the hilum.
• The lung has a convex costal surface, a concave diaphragmatic surface, and a posterior surface that lies within the paravertebral gutter. It includes an apex, a base, three surfaces, three borders, a root, lobes, and fissures.

Roots of the Lungs

• The right lung root lies within the groove of the arch of the azygos veins, and it includes eparterial, hyparterial bronchi, the right pulmonary artery, two right pulmonary veins, and hilar lymph nodes.
• The left lung root lies within the concavity of the arch of the aorta, and it includes left main bronchus, left pulmonary artery, two left pulmonary veins, and hilar lymph nodes.

Lobes and Fissures of the Lungs

• The right lung has three lobes (upper, middle, and lower), separated by oblique and horizontal fissures.
• The left lung has two lobes (upper and lower), separated by an oblique fissure. The visceral pleura extends into the fissures, allowing lobes to move freely during respiration.

Bronchi and Bronchopulmonary Segments

• The trachea bifurcates at T4 into the right and left main bronchi.
• The right main bronchus is shorter, wider, and more vertically oriented than the left main bronchus (5 cm vs 2.5 cm).
• The right secondary bronchi subdivide into 10 bronchopulmonary segments (BPS); the left into 8 BPS.

Blood Supply and Lymphatics of the Lung

• Bronchial arteries (2 left from descending thoracic aorta, 1 right from the 3rd right posterior intercostal artery) supply the bronchial tree from the main bronchi to the respiratory bronchioles.
• Pulmonary arteries carry deoxygenated blood to the alveoli (anastomose with bronchial arteries at precapillary level).
• Right bronchial vein drains into azygos vein; left bronchial vein drains into accessory hemiazygos vein.
• Four pulmonary veins drain the lungs and open into the left atrium.
• Lymph vessels accompanying the bronchial and pulmonary arteries drain into hilar (BP) nodes and efferent lymphatics, ultimately draining into the BCV.

Nerve Supply of the Lungs

• Nerves are supplied by parasympathetics from the vagus nerve and sympathetics from the thoracic sympathetic trunk.
• Vagal efferents are bronchoconstrictors and secretomotor to bronchial glands (for cough reflex). Sympathetic efferents are bronchodilators and produce an inhibitory effect on the bronchial glands.

Mediastinum

• The mediastinum is a highly mobile, bulky connective tissue septum that is centrally located between the right and left pleural cavities.
• It's superior to the diaphragm, inferior to the root of the neck, and anterior to the vertebral column and behind the sternum.
• The mediastinum is divided into superior and inferior parts at the level of T4.
  • The inferior mediastinum is further divided into anterior, middle and posterior mediastinum.

Superior Mediastinum Boundaries and Contents

• Boundaries: Superior: A line drawn from T1 to manubrium sternum, Inferior: A line across T4, Anterior: Manubrium sternum, Posterior: T1-T4 vertebrae and anterior longitudinal ligament.
• Contents: Brachiocephalic vein (BCV); superior vena cava (SVC); arch of aorta, brachiocephalic trunk, trachea, upper part of esophagus, thymus and thoracic duct.

Anterior Mediastinum

• Boundaries: Superior: A line across T4, Inferior: Diaphragm, Anterior: Body of sternum, Posterior: Anterior part of pericardium.
• Contents: Thymus and fatty tissues ( prominent in children but reduced in adults).

Middle Mediastinum

• Boundaries: Superior: A line across T4, Inferior: Diaphragm, Anterior: Anterior mediastinum, Posterior: Posterior mediastinum.
• Contents: Pericardium and heart, ascending aorta, pulmonary trunk, part of phrenic nerve, and main bronchi.

Posterior Mediastinum

• Boundaries: Superior: A line drawn across T4, Anterior: Middle mediastinum and diaphragm, Posterior: Lower border of T4 to T12 vertebrae and anterior longitudinal ligament of T4 - T12.
• Contents: Oesophagus, descending thoracic aorta, azygos system of veins, thoracic duct and sympathetic trunk.

Pericardium and the Heart

• The pericardium is a fibroserous sac that encloses the heart and the root of the great vessels. It is located behind the sternum and 2nd-6th costal cartilages and in front of the T5-T8 vertebrae.
• The fibrous pericardium is the outer layer of tissue, surrounding the heart and the large vessels.
• The serous pericardium is a thin elastic tissue that lines the fibrous pericardium and consists of parietal and visceral layers.
• Parietal pericardium lines and fuses with the fibrous pericardium while the visceral pericardium forms the epicardium of the heart.
• Between the parietal and visceral layers is the pericardial cavity, which contains pericardial fluid.
• The heart is a double self-adjusting muscular pump with four chambers: right and left atria and right and left ventricles. It is situated at a 2/3rd angle towards the left. The external wall consists of epicardium, myocardium and endocardium.
• The heart's dimensions are different in males and females (12/10cm in base to apex; 6/5cm in anteroposterior; and 9/8cm in transverse) with different weighs
• The heart is typically positioned with its base situated posteriorly, mainly made up of the left atrium and directed superiorly; its apex is situated inferolaterally and is primarily comprised by the left ventricle, being posterior to the 5th left intercostal space. -The sternocostal surface is mainly formed by the right ventricle and it receives contributions from the right atrium and the right atrioventricular (AV) groove. The diastolic surface is shaped concavely, chiefly formed by the right atrium and receiving parts from the right AV groove and the right and left ventricles. The pulmonary surface is formed by the left ventricle and is located in the cardiac notch of the left lung.

Heart Valves

• Pumonary valve is located at the 3rd costal cartilage. The aortic valve is at the 4th rib; and the tricuspid valve is at the 5th-7th ribs.
• The bicuspid valve (also called the mitral valve) lies above the tricuspid valve and is slightly higher.

Conducting System of the Heart

• Specialized myocardial and conducting tissues control heart contraction and initiate the normal heartbeat. It includes the sinoatrial (SA) node, atrioventricular (AV) node, and atrioventricular (AV) bundle of His.

Blood Vessels of the Thorax

• Great vessels of the thorax: Include the Brachiocephalic vein (BCV), Superior vena cava (SVC), aorta, pulmonary trunk and brachiocephalic trunk.
  • The BCV is formed by union of internal jugular and subclavian veins behind the sternoclavicular joint and is located in superior mediastinum. It receives the vertebral, inferior thyroid, internal thoracic, left superior intercostal and right and left supreme intercostal veins.
• SVC: Formed by the union of the right and left BCV and is situated behind the sternum. It pierces the pericardium at the 2nd right costal cartilage and opens into the right atria at the 3rd right costal cartilage. It receives blood from the head, neck, upper limbs, thorax and upper abdomen.
• Aorta: Largest artery in the thorax, arising from the aortic orifice of the left ventricle behind the 3rd left intercostal space. It's composed of ascending aorta, arch, descending thoracic and abdominal aorta. The ascending aorta, originating from the aortic orifice of the left ventricle, has three swellings (posterior, right and left) at its origin. The arch of the aorta extends from the right side of T4 to the left side and continues with the descending aorta. The pulmonary trunk divides at the inferior concavity of the aortic arch with the ligamentum arteriosus connecting to the left pulmonary artery's inferior concave side.
• The right and left recurrent laryngeal branches of the vagus nerve loop around the subclavian arteries. The arch of the aorta has baroreceptors in its adventitia that control heart rate and aortic bodies that control respiratory functions. Branches from its anterior surface include 2 left bronchial, oesophageal, pericardial and diaphragmatic branches; those from the posterior surface include 9 pairs of intercostal arteries and one pair of subcostal arteries.

Thoracic Duct and Azygos Vein

• Thoracic duct: The longest lymphatic duct conveying lymph to the circulatory system. It's an upward continuation of the cisterna chyli at T12, located in the posterior mediastinum on the right side of the esophagus. It ascends behind the esophagus to lie on the left in the superior mediastinum and empties into the BCV at the venous angle. It contains multiple valves with no valve at its termination. Tributaries drain lymph from the lower limbs, pelvis, perineum, abdomen, left side of thorax, left upper limb, and left side of neck, face and head.
• Azygos Vein: It represents the embryonic right posterior cardinal vein. Formed by union of right ascending lumbar and right subcostal veins at L2 and enters the thorax at T12. It is located behind the esophagus in the posterior mediastinum and arches over the right main bronchus at T4. It empties into the SVC forming a communication between SVC and IVC.

Clinical Importance

• Clinical implications for the thorax are covered in the notes, including: Angina pectoris, Pulmonary embolism, and Thoracic Rib Fractures.

Other Structures (Thymus & Oesophagus)

• The thymus, a lymphoid organ, is prominent in children but gradually diminishes in size into adulthood. Its location extends from the lower pole of thyroid gland to the 4th costal cartilage, with anterior relations (pretracheal fascia, sternohyoid and sternothyroid muscles, manubrium and upper part of body of sternum) and posterior relations (arch of aorta and its branches, left BCV, trachea). It receives blood supply from inferior thyroid and thymic arteries; its venous drainage flows into subclavian vein. Lymphatic drainage is into parasternal, tracheobronchial and brachiocephalic lymph nodes. Nerve supply involves sympathetic and parasympathetic fibers.

• The esophagus is a muscular tube (25cm) extending from C6 to the cardiac orifice of the stomach, lying in the superior and posterior mediastinum. It has cervical, thoracic, and abdominal parts, and isn't a perfectly straight structure. It's situated to the left in the neck, returns to the midline at thoracic inlet, and continues to the left in the superior mediastinum, deviating left as it enters the diaphragm at T10. Related structures include the prevertebral fascia in the cervical portion and the azygos vein and aorta in the thoracic portion. It has four constrictions; the first at its origin (C6, 15cm from incisor tooth), the second where the arch of aorta lies anterior to it (T4, 22cm from incisor tooth), the third at the trachea bifurcation (27cm from incisor tooth), and the fourth at T10, 38-40cm from incisor tooth. It receives blood supply from the inferior thyroid artery, esophageal branches of descending thoracic aorta, and left gastric artery.

Test your knowledge on the anatomical structures of the heart and thoracic cavity. This quiz covers topics such as the apex of the left ventricle, the boundaries of the heart, and the anatomical features associated with the lungs. Perfect for students studying cardiovascular anatomy.