L27 Anatomy of the Major Blood Vessels PDF

Anatomy of the major blood vessels ILOs By the end of this lecture, students will be able to 1. Appraise the surface projection of the major vessels in relation to their anatomical position and course. 2. Correlate the different parts of the aorta with its anatomical features & the branches originat...

Anatomy of the major blood vessels ILOs By the end of this lecture, students will be able to 1. Appraise the surface projection of the major vessels in relation to their anatomical position and course. 2. Correlate the different parts of the aorta with its anatomical features & the branches originating from each part. 3. Describe the subclavian artery regarding its origin, termination & distribution. 4. Differentiate between the carotid arteries regarding their location, origin & termination relevant to their distribution. 5. Know the major veins attached to the heart and how they are formed. CLINICAL PROBLEM A specialist registrar is performing his first ductus arteriosus ligation. The consultant supervising him instructs him to be careful when placing a clamp on the ductus to avoid injury to an important structure intimately related to it. Which structure is meant by the consultant? Ascending aorta - Origin : left ventricle at the left sternal margin opposite the left third intercostal space. Course : it ascends upwards. It lies on the right side of the pulmonary trunk. Termination : at right second costal cartilage where it continues as the arch of aorta. Branches : right and left coronary arteries. (Figure 1) Figure 1. Ascending aorta. Page 1 of 9 Arch of aorta - Origin : continuation of the ascending aorta at right second costal cartilage. - Course : it passes upwards, backwards and to the left. - Relations : a. superiorly : the origin of its branches (innominate, left common carotid and left subclavian arteries). b. inferiorly : 1- termination of the pulmonary trunk. 2- ligamentum arteriosum. It connects the arch of aorta with the pulmonary trunk. It represents the obliterated ductus arteriosus that was functioning in the embryo. 3- left recurrent laryngeal nerve. It is a branch of the left vagus nerve and curves below the arch of aorta to lie behind the ligamentum arteriosum. (Figure 2) - Termination : it continues as the descending aorta opposite the fourth thoracic vertebra (T4). - Branches : 1- innominate artery (the largest branch). It divides into right common carotid and right subclavian arteries. 2- left common carotid artery. 3- left subclavian artery. Figure 2. Arch of aorta. Descending aorta - Origin : it is a continuation of the arch of aorta opposite the fourth thoracic vertebra (T4). - Course : it descends in the thorax and pierces the diaphragm. - Termination : it continues as the abdominal aorta opposite the twelfth thoracic vertebra (T12). (Figure 3) - Branches : 1- esophageal arteries. 2- diaphragmatic (phrenic) arteries. 3- pericardial arteries. 4- intercostal arteries. Page 2 of 9 Figure 3. Descending aorta. Pulmonary trunk - Origin : right ventricle opposite the left third costal cartilage. - Course : it ascends upwards. It lies on the left side of the ascending aorta. (Figure 2) - Termination and branches : It ends by dividing into right and left pulmonary arteries. Innominate (brachiocephalic) artery - Origin : it is the largest branch of the arch of aorta.. - Termination and branches : It ends behind the right sternoclavicular joint by dividing into right subclavian and common carotid arteries. (Figure 2) Common carotid artery - Origin : - On the left side : branch of the arch of aorta. - On the right side : branch of the innominate artery. (Figure 2) - Course : 1- it passes behind the sternoclavicular joint. 2- it ascends in the neck inside the carotid sheath. - Termination and branches : It ends opposite the disc between C3 and C4 (upper border of thyroid cartilage) by dividing into external and internal carotid arteries. N.B. the carotid sheath is a facial sheath in the neck that contains the common carotid artery, internal jugular vein and vagus nerve). (Figure 4) Page 3 of 9 Figure 4. Common carotid artery. External carotid artery - Origin : a branch of the common carotid artery opposite the disc between C3 and C4 (upper border of thyroid cartilage) - Course : - it ascends upwards in the neck outside the carotid sheath. (Figure 4) - Termination: It ends behind the neck of the mandible inside the parotid gland. (Figure 5) Figure (5) External and internal carotid arteries Internal carotid artery - Origin : a branch of the common carotid artery opposite the disc between C3 and C4 (upper border of thyroid cartilage) - Course : - it ascends upwards in the neck inside the carotid sheath. (Figure 4) - Termination: It enters the skull to supply the brain. Page 4 of 9 Subclavian artery - Origin : - On the left side : branch of the arch of aorta. - On the right side : branch of the innominate artery. (Figure 2) - Course : (Figure 6) 1- it passes behind the sternoclavicular joint. 2- it passes to the neck where it is divided by a muscle called scalenus anterior into 3 parts : a. the first part lies medial to the muscle. b. the second part lies behind the muscle. c. the third part lies lateral to the muscle. 3- it curves laterally to reach the upper limb. - Termination : It continues as the axillary artery at the outer border of the first rib. N.B. the first rib has outer and inner borders and upper and lower surfaces. Figure 6. Subclavian artery. Page 5 of 9 Right innominate vein - Origin : union of the right internal jugular and subclavian veins behind the right sternoclavicular joint. (Figure 7) - Course : vertical course. - Termination : by joining the left innominate vein opposite the right first costal cartilage to form the superior vena cava. Figure 7. Veins of the thorax. Left innominate vein - Origin : union of the left internal jugular and subclavian veins behind the left sternoclavicular joint. (figure 7) - Course : oblique course. - Termination : by joining the right innominate vein opposite the right first costal cartilage to form the superior vena cava. Superior vena cava - Origin : union of the right and left innominate veins opposite the right first costal cartilage. (Figure 7) Course : vertical course. Termination : into the right atrium opposite the right third costal cartilage. Tributaries : Page 6 of 9 1- Right and left innominate veins. 2- arch of azygos vein that opens in the superior vena cava opposite the right second costal cartilage. (Figure 2) Inferior vena cava - Origin : union of the right and left common iliac veins opposite the fifth lumbar vertebra (L5). (Figure 7) - Course : 1- it passes through the abdomen. 2- it pierces the diaphragm. - Termination : into the right atrium opposite the right sixth costal cartilage. Azygos vein - it is a connection between the superior vena cava and inferior vena cava. (Figure 8) - Origin : inferior vena cava in the abdomen opposite the first lumbar vertebra (L1). - Course : 1- it passes through the abdomen. 2- it pierces the diaphragm. 3- it ascends in the thorax and curves anteriorly forming an arch. - Termination : into the superior vena cava opposite the right second costal cartilage. Figure 8. Azygos vein. Page 7 of 9 Ligamentum arteriosum - It is fibrous band connecting the arch of aorta and pulmonary trunk. - During embryonic life, it was patent and was called ductus arteriosus. In the embryo, the lungs are collapsed and the blood passes from the pulmonary trunk to the arch of aorta. - After birth, it becomes closed and fibrosed forming ligamentum arteriosum. - It may remain patent after birth and blood passes from the aorta to the lungs with pulmonary hypertension. Figure 9. Ductus arteriosus. Sternoclavicular joint and the blood vessels Figure 10. Sternoclavicular joint and the blood vessels. Page 8 of 9 1- Arteries passing behind the joint : a. Termination of innominate artery. c. Common carotid arteries. C. Subclavian arteries. 2- Veins passing behind the joint : internal jugular and subclavian veins join to form the innominate vein. Carotid sheath - The upper part of the sheath contains : 1- Internal carotid artery. 2- Internal jugular vein. 3- Vagus nerve. - The lower part of the sheath contains : 1- Common carotid artery. 1- Internal jugular vein. 2- Vagus nerve. Page 9 of 9