Region: Thorax

Sinoatrial Node

Sinoatrial Node The structure indicated is the sinoatrial node The conduction system of the heart is responsible for the coordinated contraction of the atria and ventricles and is comprised of the following main structures: Sinoatrial node Atrioventricular node Atrioventricular bundle of His Right and left bundle branches Purkinje fibres The sinoatrial node, often referred to as the SA node, is the pacemaker of the heart. It is located in the right atrium and is responsible for generating normal sinus rhythm. The sinoatrial node is located lateral to the junction where the superior vena cava enters the right atrium. Electrical signals generated …

Sinoatrial Node Read More »

sinoatrial node

Sternal Angle

Sternal Angle The diagram indicates the sternal angle of Louis. The sternal angle is the angle formed between the manubrium of the sternum and the body of the sternum (manubriosternal junction), and is an important anatomical landmark. It marks the level of the 2nd pair of costal cartilages which lies at the level of the intervertebral disc between thoracic vertebrae 4 and 5. This level represents several important anatomical features: Beginning and end of the aortic arch Bifurcation of the trachea Bifurcation of the pulmonary trunk Left recurrent laryngeal loops under arch of aorta Ligamentum arteriosum lies at this level …

Sternal Angle Read More »

sternal angle

Aortic Arch

Aortic Arch The structure indicated is the arch of the aorta. The aorta arises from the left ventricle of the heart and supplies the body with oxygenated blood. The aorta can be divided into thoracic and abdominal parts (the thoracic aorta pierces the diaphragm to enter the abdominal cavity, becoming the abdominal aorta). The thoracic aorta consists of: Ascending aorta Aortic arch Descending (thoracic) aorta The aortic arch lies in the superior mediastinum and begins and ends at the level of the angle of Louis (sternal angle) which lies at the level of the intervertebral disc between T4/T5. The arch …

Aortic Arch Read More »

aortic arch

Pectoralis Minor

Pectoralis Minor The structure indicated is the pectoralis minor muscle. The pectoralis minor muscle lies deep to the much larger, powerful pectoralis major muscle. The pectoralis minor muscle is covered anteriorly by the clavipectoral fascia. This muscle divides the axillary artery into three parts. Part 1 lies proximally to the pectoralis minor, part 2 is the part of the axillary artery covered by the pectoralis minor, and the third part lies distal to the pectoralis minor. The pectoralis minor inserts onto the coracoid process of the scapula. There are three muscles which attach to the coracoid process: Short head of …

Pectoralis Minor Read More »

pectoralis minor

Xiphoid Process

Xiphoid Process The highlighted structure is the xiphoid process of the sternum. The sternum consists of three parts: Manubrium of the sternum Body of sternum Xiphoid process The xiphoid process is the most inferior part of the sternum and is the smallest part. Learn more about the sternum in this tutorial!

xiphoid process

Serratus Anterior

Serratus Anterior The structure indicated is the serratus anterior muscle. The serratus anterior muscle originates on the first to eighth ribs laterally on the chest and inserts medially on the scapula. The serratus anterior is divided into three parts: Serratus anterior superior Serratus anterior intermediate Serratus anterior inferior The serratus anterior is often called the “boxer’s muscle” as it is responsible for protraction of the scapula – a movement which occurs when throwing a punch. Origin: fleshy slips from lateral parts of 1st to 8th ribs Insertion: Medial margin of scapula on anterior surface Innervation: Long thoracic nerve Action: Protraction …

Serratus Anterior Read More »

Serratus Anterior

Tricuspid Valve

Tricuspid Valve The structure indicated is the tricuspid valve of the heart. There are four sets of valves in the heart. Between the atria and the ventricles are the atrioventricular valves; on the right is the tricuspid valve, on the left is the mitral (bicuspid) valve. Between the ventricles and the aorta/pulmonary trunk are the semilunar valves. The pulmonary valve is located between the right ventricle and the pulmonary trunk, and the aortic valve is located between the left ventricle and the aorta. The atrioventricular valves are controlled by papillary muscles, which are specialised structures in the ventricles that attach …

Tricuspid Valve Read More »

Tricuspid Valve

Great Cardiac Vein

Great Cardiac Vein The structure indicated is the great cardiac vein. The coronary sinus lies posteriorly on the heart in the coronary sulcus and receives four cardiac veins: Great cardiac vein Middle cardiac vein Small cardiac vein Posterior cardiac veins The great cardiac vein lies in the anterior interventricular sulcus together with the anterior interventricular artery (left anterior descending), and for this reason it is sometimes referred to as the anterior interventricular vein. The great cardiac vein begins at the apex of the heart and ascends in the anterior interventricular sulcus to reach the coronary sulcus, where it then runs …

Great Cardiac Vein Read More »

Great Cardiac Vein

Posterior Interventricular (Descending) Artery

Posterior Interventricular (Descending) Artery The structure indicated is the posterior interventricular artery (posterior descending artery) of the heart. The posterior interventricular artery determines the “dominance” of the coronary blood supply to the heart. For example, if the posterior interventricular artery arises from the right coronary artery, the heart is said to be “right coronary dominant”. In the majority of people, the posterior interventricular artery will usually arise from the right coronary artery. If the posterior interventricular artery arises from the left coronary artery, it will branch from the circumflex coronary artery. Co-dominance occurs when the posterior interventricular artery arises from …

Posterior Interventricular (Descending) Artery Read More »

Posterior Interventricular (Descending) Artery

Left Subclavian Artery

Left Subclavian Artery The structure indicated is the left subclavian artery. The subclavian arteries are located under (“sub”) the clavicle (“clavian”) and receive blood from the aortic arch. The subclavian arteries supply the arms, with some branches that extend to supply the head. The branches of the aortic arch are: Brachiocephalic artery Left common carotid artery Left subclavian artery The left subclavian artery comes directly off the arch of the aorta, whereas on the right side of the body, the brachiocephalic artery splits, giving rise to the right subclavian artery, and the right common carotid artery. The subclavian artery becomes …

Left Subclavian Artery Read More »

Left Subclavian Artery