1. No. 16

2. Section 3 The Arteries
Upon leaving the heart, the blood enters the vascular system, which is composed of numerous blood vessels. The vessels transport the blood to all parts of the body, permit the exchange of nutrients, metabolic end products, hormones, and other substances between the blood and the interstitial fluid, and ultimately return the blood to the heart.
The vessels of the circulatory system can be divided into two separate circuits, each of which leaves and returns to the heart.

3. The pulmonary circuit carries blood from the right side of the heart (right ventricle) to the lungs and back to the left side of the heart (left atrium).
The systemic circuit carries blood that has just left the pulmonary circuit (from the left ventricle) to the rest of the body and back to the right side of the heart (right atrium).

5. Vessels called arteries carry blood away from the heart
Vessels called arteries carry blood away from the heart. Compares to the other types of blood vessels, arteries must be able to withstand the greatest internal pressure. The major arteries divide into smaller arteries, then into still smaller arterioles, and finally into tiny capillaries.

6. Ⅰ. The Arteries of Pulmonary Circulation
Ⅰ) The Pulmonary Artery and its Branches
The pulmonary trunk conveys deoxygenated blood from the right ventricle of the heart to the lungs. In the concavity of the aortic arch it divides into right and left pulmonary arteries.

8. The right pulmonary artery runs to the hilum of the right lung, where it divides into three branches to distribute to the corresponding lobes of the lung.
The left pulmonary artery runs to the hilum of the left lung, where it divides into two branches, one for each lobe of the lung.

9. Ⅱ) The arterial Ligament
The left pulmonary artery is connected to the concavity of the aortic arch by a fibrous cord, termed the arterial ligament, which is found as the ductus arteriosus in the fetus. During fetal life, most of the blood in the pulmonary trunk passes through the ductus arteriosus into the aorta. After birth, the lumen of the ductus is gradually obliterated and it is transformed into the arterial ligament.
Occasionally the ductus arteriosus fails to close. In this acse tying the ductus is often successful in alleviating the condition.

10. Ⅱ. The Arteries of Systemic Circulation
Ⅰ) The Aorta
It is main trunk of the series of arteries which convey the oxygenated blood to the tissue of the body. For convenience, it is described in three portions, the ascending aorta, the aortic arch and the descending aorta.

11. 1. The ascending aorta (ascending part of aorta)
Route:
It begins at the base of the left ventricle, at a level with the lower border of the third costal cartilage, passes obliquely upwards, forwards and to the right. As high as the upper border of the second right costal cartilage, it continues with the aortic arch.
Branches:
The only branches of the ascending aorta are coronary arteries.

13. 2. The aortic arch
Route:
It begins at the level of the second right sternocostal joint, and runs at first upwards, backwards and to the left in front of trachea, it is then directed backwards on the left side of the trachea, and finally passes downwards on the left side of the body of fourth thoracic vertebra, at the lower border of which it is continuous with the descending aorta.
Branches:
Three branches are given off from the highest part of the aortic arch.

15. From right to left:
1) The brachiocephalic trunk (innominate artery)
It passes obliquely upwards, backwards and to the right, at the level of the right sternoclavicular joint, it divides into the right common carotid and right subclavian arteries.
2) The left common carotid artery
3) The left subclavian artery

16. 3. The descending aorta (descending part of aorta)
It is divided into two portions, the thoracic aorta and the abdominal aorta.
1) The thoracic aorta
It is contained in the posterior mediastinum. It begins at the level of the lower border of the fourth thoracic vertebra, where it is continuous with the aortic arch, and ends in front of the lower border of the twelfth thoracic vertebra at the aortic hiatus of the diaphragm.

18. 2) The abdominal aorta
It begins at the aortic hiatus of the diaphragm, in front of the lower border of the body of the last thoracic vertebra, descends in front of the vertebral column, and ends on the body of the fourth lumbar vertebra by dividing into two common iliac arteries.

19. Ⅱ) The Arteries of Head and Neck
The blood supply of the head and neck is chiefly from the branches of the common carotid arteries and partly from those of the subclavian arteries.

20. 1. The common carotid arteries
The right common carotid artery begins at bifurcation of the brachiocephalic trunk behind the right sternoclavicular joint, while the left common carotid artery springs from the aortic arch.
Each passes obliquely upwards and slightly laterally, along the side of the trachea and esophagus, to the level of the upper border of the thyroid cartilage, where it divides into the external and internal carotid arteries.

22. Carotid sinus and carotid body
A dilatation at the point of the bifurcation of common carotid artery is known as the carotid sinus, which usually involves, and may be restricted to the proximal part of the internal carotid artery. It acts as a pressure-receptor which is part of the blood pressure regulating mechanism. It reacts to changes of the arterial blood pressure reflexly.

23. A small, reddish-brown structure behind the point of division of the common carotid artery is termed the carotid body which acts as a chemoreceptor. It responds to changes in the composition of the blood, particularly the oxygen-carbon dioxide ratio.

24. 1) The internal carotid artery
It ascends along the pharynx to the base of the skull, and enters the cranial cavity through the carotid canal without giving off branches in the neck. This is the major artery to the brain and other intracranial and orbital structures.

25. 2) The external carotid artery
It begins oppsite the upper border of the thyroid cartilage, and, gaking a slightly curved course, passes upwards and forwards, and then inclines backwards to a point behind the neck of mandible, where, in the substance of the parotid gland, it divides into the superficial temporal and maxillary arteries.

26. Its main branches are as follows:
①The superior thyroid artery
It supplies the adjacent muscles and the thyroid gland.
Branch:
Superior laryngeal artery
It accompanies the internal branch of the superior laryngeal nerve and pierces the thyrohyoid membrane to supply the larynx.

28. ② The lingual artery
It is the principal vessel of the tongue and the structures on the floor of the mouth.
③ The facial artery
It supplies the submandibular gland, the tonsil and the structures of the face.
④ The occipital artery
It arises from the back of the external carotid artery, opposite to the facial artery, and runs upwards and backwards to the posterior part of the scalp.

29. ⑤ The maxillary artery
It is the larger terminal branch of the external carotid artery, arises behind the neck of the mandible and is at first embedded in the parotid gland. It passes forwards to the infratemporal fossa, and supplies the upper and lower jaws, teeth and gums, the muscles of mastication, the palate, the nasal cavity and the paranasal sinuses.

30. The middle meningeal artery is the most important branch of the maxillary artery. It ascends to the base of the skull to pass into the cranial cavity through the foramen spoinosum. Its branches fan out to supply the cerebral dura mater. Injury of this artery as in the case of cranial bone fracture in temporal region may result in the epidural haematoma.

31. ⑥ The superficial temporal artery
It is the smaller terminal branch of the external carotid artery, ascends over the zygomatic arch, and enters the superfiacial fascia of the temporal region. Many branches ramify over the temporal, auricular, zygomatic and facial regions from which the arteries receive their names.

32. 2. The subclavian artery
The right subclavian artery arises from the brachiocephalic trunk; the left, from the aortic arch. Each artery emerges from the superior aperture of the thorax. It ascends to the root of the neck and then arches laterally across the front of the cervical pleura and passes between the scalenus anterior and the scalenus medius to the outer border of the first rib, where it becomes the axillary artery. Hemorrhage of the upper limb can be controlled by compressing the vessel downwards and backwards against the first rib immediately above the mid-point of the clavicle.

35. Branches:
1) The vertebral artery
It arises from the upper and posterior part of the proximal end of the subclavian artery. It ascends through the foramina in the transverse processes of the upper six cervical vertebrae, and enters the skull through the foramen magnum.
It supplies the brain and spinal cord.

36. 2) The internal thoracic (mammary) artery
It arises from the inferior surface of the subclavian artery, opposite the vertebral artery. It descends behind the cartilage of the upper six ribs at a distance of 1.2 cm from the lateral border of the sternum, and at the level of the sixth intercostals space divides into the musculophrenic and superior epigastric arteries.

37. The superior epigastric artery enters the sheath of the rectus abdominis, at first lying behind the muscle, then perforating and supplying it, and anastomosing with the inferior epigastric artery from the external iliac artery.
The branches of the internal thoracic artery are distributed chiefly to the anterior thoracic and abdominal walls, the pleura, the pericardium and the diaphragm.

38. 3) The thyrocervical trunk
It is short, arises from the front of the subclavian artery, close to the medial border of the scalenus anterior, and divides almost immediately into three branches. One of them is the inferior thyroid artery. Its branches supply the lower part of the thyroid and parathyroid glands, larynx, trachea and esophagus.

39. 4) The inferior thyroid artery
5) The costocervical trunk
They supply the first two intercostals spaces and the muscles of the scapular region.
Dorsal scapular artery:

40. Ⅲ) The Arteries of Axilla and Upper Limb
The subclavian artery, after giving off its cervical branches, continues as the great arterial stem of the upper limb.

41. It is the continuation of the subclavian artery and begins at the outer border of the first rib, and ends at the lower border of the teres major, beyond which the artery takes the name of brachial artery. Its chief branches are:

42. 1) The thoracoacromial artery
It is a short branch and divides into several branches to supply the muscles of thorax and the scapular region.
2) The lateral thoracic artery
It follows the lateral border of the pectoralis minor to the side of the chest, and supplies the serratus anterior and the muscles of thorax, the axillary lymph nodes and the subscapularis.

44. 3) The subscapular artery
It is the largest branch of the axillary artery, usually it arises at the lower border of the subscapularis, runs to the inferior angle of the scapula, where it anastomoses with the lateral thoracic and intercostals arteries; finally it ends in the neighbouring muscles and adjacent part of the chest wall. After a short course it gives off the circumflex scapular artery and thoracodorsal artery.

45. The circumflex scapular artery is generally larger than the continuation of the subscapular. It curves round the lateral border of the scapula, traversing the triangular space; it enters the infraspinous fossa, and anastomoses with the suprascapular artery and other vessels to form an arterial network around the scapula.
The thoracodorsal artery continues downwards along the posterior axillary wall and is accompanied in its course by the thoracodorsal nerve (to the latissimus dorsi). It gives branches to muscles of the posterior wall of the axilla.

46. 4) The anterior humeral circumflex artery
It arises from the axillary at the lower border of the subscapularis. It runs horizontally in front of the surgical neck of the humerus, and anastomoses with the posterior circumflex humeral artery.

47. 5) The posterior humeral circumflex artery
It is larger than the anterior one. It arises from the axillary at the lower border of the subscapularis, and runs backwards through the quadrangular space. It winds the neck of the humerus and distributes branches to the shoulder joint and the adjacent muscles.

48. 2. The brachial artery
It is the continuation of the axillary artery. It begins at the lower border of the tendon of the teres major, and runs downwards on the medial side of the biceps brachii. It ends in the cubital fossa, opposite the neck of the radius, by dividing into the radial and ulnar arteries. The brachial artery gives off branches to the muscles of the arm and the humerus.

50. The deep brachial artery is a larger branch from the brachial artery, just below the lower border of the teres major. It follows the radial nerve closely, running at first backwards between the long and medial heads of the triceps brachii, then along the groove for the radial nerve. It supplies the triceps.

51. 3. The radial artery
It begins at the division of the brachial artery below the bend of the elbow, and passes along the radial side of the forearm to the wrist, where its pulsation can readily be felt and it is used clinically for taking the pulse.
Its branches are:
1) The muscular branches
2) The superficial palmar branch
3) The principal artery of theumb

53. 4. The ulnar artery
It begins at the level of the neck of the radius. Its branches are:
1) The muscular branches
2) The common interossous artery
3) The deep palmar branch

54. 5. The superficial palmar ch and deep palmar arch.
1) The superficial palmar arch
Formation: It is formed mainly by the ulnar artery, and is usually completed by the superficial palmar branch of the radial artery.
Location: It is covered by the palmar aponeurosis, and lies on the flexor tendons of the fingers. Its convexity is placed at the level of a line drawn across the hand from the distal border of the root of the extended thumb.

56. Branches: It gives off three common palmar digital arteries
Branches: It gives off three common palmar digital arteries. Each then divides into a pair of vessels, the proper palmar digital arteries, which run along the contiguous sides of the index, middle, ring and little fingers. An additional digital branch of the arch passes to the ulnar side of the fifth finger.

57. 2) The deep palmar arch
Formation: It is formed by the anastomsis of the terminal part of the radial artery with deep palmar branch of the ulnar artery.
Location: It lies upon the proximal ends of the metacarpal bones. It is about 2 cm proximal to the level of the superficial palmar arch. It covered by the flexor tendons of the finger.
Branches: The branches of the arch supply the bones and muscles of the hand, and join common digital branches of the superficial palmar arch.

59. Ⅳ) The Arteries of Thorax
The are chiefly from the thoracic aorta. For convenience, the arteries can be divided into the parietal and visceral branches.

60. 1. The parietal branches
1) The posterior intercostals arteries
There are usually nine pairs of posterior intercostals arteries derived from the thoracic aorta. They are distributed to the lower nine intercostals spaces, being supplied by the supreme insupreme intercostals artery.

62. 2) The subcostal arteries
They are the last pair of arteries arising from the thoracic aorta, in series with the posterior intercostals arteries, but are named subcostal because they are situated below the twelfth rib.
The posterior intercostals and subcostal arteries chiefly supply the wall of thorax, the upper part of the abdominal wall, the spinal cord and its coverings.

63. 2. The visceral branches
They are the bronchial, esophageal and pericardial arteries which supply arterial blood to the structures for which they are named.

64. Ⅴ) The Arteries of Abdomen
The abdominal aorta is the main trunk of the abdominal arteries.it also has the parietal and visceral branches.

65. 1. The parietal branches
1) The inferior phrenic artery
Three unpaired visceral arteries (the celiac trunk, the superior mesenteric artery and the inferior mesenteric artery) supply the abdominal organs of alimentary system.
Paired arteries are the middle suprarenal arteries, the renal arteries, and the testicular or ovarian arteries.
2) The lumbar arteries

66. 2. The visceral branches
Three unpaired visceral branches:
The celiac trunk,
The superior mesenteric artery,
The inferior mesenteric artery,
They supply the abdominal organs of alimentary system.
Four paires of arteries to the paires organs (suprarenal gland, kidney)

69. Ⅵ) The Arteries of Pelvis
Ⅶ) The Arteries of Lower Limb