AORTA

AORTA

• Aorta receives oxygenated blood from the left ventricle & distributes it to all parts of the body.
• The thoracic aorta is divided into three parts:

1. ASCENDING AORTA

• It is 5 cm long, arises from the left ventricle & is entirely intrapericardial. It begins at the level of the lower border of third costal cartilage, behind the left half of sternum.
• At the sternal end of the upper border of second costal cartilage, it continues as the arch of the aorta.
• There are three dilatations in the roots of ascending aorta, called Aortic Sinuses of Valsalva:- One anterior & two posterior.
• The right coronary artery arises from anterior aortic sinus. 
• The left coronary artery arises from the left posterior aortic sinus.

2. ARCH OF AORTA

• It lies in the superior mediastinum, behind the lower half of manubrium sterni.
• It begins as a continuation of ascending aorta at the level of the upper border of right second sternocostal junction (sternal angle) & continues as a descending aorta on the left side at the lower border of T4 vertebra.
• Tracheal bifurcation also lies at the level of the arch of aorta (25cm from incisor both crosses oesophagus).
• The left common carotid artery arising from the brachiocephalic trunk is the commonest variation in the arteries arising from the arch of the aorta.
• Thus beginning & end of the arch of the aorta are at the same level, although it begins anteriorly & ends posteriorly.

Arch of Aorta has the following features:

1. The left surface is crossed by 4 nerves from anterior to posterior: Left phrenic, the superior cervical cardiac branch of the left sympathetic trunk, the inferior cervical cardiac branch of the left vagus, and left vagus nerve.
2. Left recurrent laryngeal nerve winds around the arch.
3. Three branches arise from convexity:  Brachiocephalic trunk,   Left common carotid artery  &   Left subclavian artery.

3. DESCENDING THORACIC AORTA

• It begins as a continuation of the arch of the aorta to the left lower border of the T4 vertebra.
• The aortic arch ends and the descending aorta begins at the level of left 2nd costal cartilage between the fourth and fifth thoracic vertebrae.
• It descends through the posterior mediastinum & enters the abdomen bypassing through aortic hiatus of the diaphragm at the T12 level.

Branches of descending aorta are:

1. Pericardial, mediastinal & esophagal branches
2. Left bronchial (right bronchial usually arises from 3rd posterior intercostal artery)
3. Right & left lower nine posterior intercostal arteries
4. Right & left superior phrenic arteries
5. Right & left subcostal arteries 

• It also, supplies sequestrated lung lobe. 

VASA VASORUM of Ascending aorta & Arch of aorta arise from:

1. Coronary arteries
2. Brachiocephalic trunk
3. Bronchial artery 

VASA VASORUM of Descending aorta arise from:

1. Intercostal arteries (Thoracic part)
2. Lumbar & mesenteric arteries (Abdominal part)

ABDOMINAL AORTA

• It begins at the aortic hiatus (aorta with thoracic duct & azygous vein) of the diaphragm.
• Anterior to the lower border of vertebra T-12.
• Median arcuate ligament passes anterior to the aorta. 

 BRANCHES OF ABDOMINAL AORTA:

• 4 pairs of lumbar arteries arise from the aorta & the small fifth pair is usually represented by the lumbar branches of iliolumbar arteries or from the median sacral artery. 

Branch	Artery	Origin	Parts Supplied
Anterior	Celiac trunk	Immediately inferior to the aortic hiatus	Foregut
	Superior   mesenteric	Immediately inferior to the celiac trunk	Midgut
	Inferior   mesenteric	Inferior to the renal arteries	Hindgut
Paired anterior	Testicular or   ovarian   arteries	Inferior to the renal arteries	Testes in male and ovaries in female
Lateral & Paired	Middle   suprarenal   Artery	Immediately superior to the renal arteries	Suprarenal glands
	Renal arteries	Immediately inferior to the superior mesenteric artery	Kidneys
	Inferior phrenic   artery	Immediate inferior to aortic hiatus	Diaphragm
Posterior paired	Lumbar arteries	Usually four pairs	Posterior abdominal wall and spinal cord
Posterior	Median sacral   arteries	Just superior to the aortic bifurcation
Terminal	Common iliac   arteries	Bifurcation at the level of L4	It’s external   branch   Make anastomosis   with superior   epigastric artery

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