Vessels and Nerves Flashcards
What are the features of the aorta?
Largest vessel of the body and carries oxygenated blood from the heart to the body.
Originates from the aortic orifice in the left ventricle where blood flows through the aortic valve.
Ascending aorta - coronary arteries branch from here
Arch of the aorta (sternal angle, ends at T4) - goes over the top of the left lung and has three branches (brachiocephalic trunk which gives right subclavian and right common carotid, the left common carotid and the left subclavian arteries)
Phrenic and vagus cross arch
Descending aorta - continues through the diaphragm at T12 to abdomen
How can an aneurysm in the aorta affect the left lung?
The arch of the aorta hooks over the left bronchus and lies on the left side of the trachea and oesophagus with the left recurrent laryngeal nerve lying between the two. Aneurysm of the aorta can occlude the left bronchus and collapse the left lung.
What is an aortic dissection?
Aortic dissection refers to a tear in the aorta which creates two channels for blood flow. One is the normal lumen, the other creating a stationary pocket in the wall. This can constrict the lumen and cause dilation of the wall, which may lead to an aortic aneurysm (dilation greater than 50%) which can lead to rupture.
What are the features of the pulmonary arteries?
Pulmonary arteries receive deoxygenated blood from the right ventricle and deliver it to the lungs for gas exchange to take place. The arteries begin as the pulmonary trunk which leaves the right ventricle via the pulmonary valve. At around the level of T5-T6, the pulmonary trunk splits into the right and left pulmonary arteries. The left pulmonary artery supplies blood to the left lung, bifurcating into two branches to supply each lobe of the lung. The right pulmonary artery is the thicker and longer artery of the two, supplying blood to the right lung. It also further divides into two branches.
What are the features of the pulmonary veins?
Pulmonary veins receive oxygenated blood from the lungs, and enter the pericardium to deliver it to the left atrium for it to be pumped around the body. There are four pulmonary veins, with one superior and one inferior for each of the lungs.
What are the features of the superior vena cava?
The superior vena cava receives deoxygenated blood from the upper body (superior to the diaphragm, excluding the lungs and heart), delivering it to the right atrium.
It is formed by merging of the brachiocephalic veins, travelling inferiorly through the thoracic region until draining into the superior portion of the right atrium at the level of the 3rd rib.
What are the features of the inferior vena cava?
The inferior vena cava receives deoxygenated blood from the lower body (all structures inferior to the diaphragm), delivering it back to the heart.
It is initially formed in the pelvis by the common iliac veins joining together. It travels through the abdomen, collecting blood from the hepatic, lumbar, gonadal, renal and phrenic veins. The inferior vena cava then passes through the diaphragm, entering the pericardium at the level of T8. It drains into the inferior portion of the right atrium.
What is the phrenic nerve?
A bilateral, mixed nerve that originates from nerve roots C3, C4, C5.
What does the phrenic nerve innervate?
It is the only source of motor innervation to the diaphragm, but provides sensory innervation for the central part of the diaphragm, the pericardium and the mediastinal part of the parietal pleura.
Where does the phrenic nerve run?
It runs downwards anterior to the lung and on towards the dome of the diaphragm. On the right it runs adjacent to the right brachiocephalic vein, the superior vena cava and the right side of the heart. On the left it descends in front of the root of the lung then lies on the pericardium as it descends to reach the diaphragm.
What is the vagus nerve?
10th cranial nerve, originating from the medulla in the brainstem and exits the skull via the jugular foramen. In the neck the vagus nerve travels with the internal jugular vein and common carotid artery before it splits into left and right vagus nerves.
Where does the vagus nerve run in the thorax?
In the thorax, the right vagus nerve forms the posterior vagal trunk, and the left forms the anterior vagal trunk.
The right vagus nerve lies on the trachea and crosses behind the root of the lung and breaks up into branches on the oesophagus forming the oesophageal plexus.
The left vagus nerve crosses the arch of the aorta, crosses behind the root of the left lung. It also breaks into branches which contribute to the oesophageal plexus, which innervates the smooth muscle of the oesophagus.
Passes through the diagram at oesophageal hiatus (T10).
What are 2 other branches of the vagus nerve in the thorax?
Left recurrent laryngeal nerve – it hooks under the arch of the aorta, ascending between trachea and oesophagus to innervate the majority of the intrinsic muscles of the larynx.
(Right recurrent laryngeal is in the neck, not the thorax).
Cardiac branches – these innervate regulate heart rate and provide visceral sensation to the organ.
What are the functions of the vagus nerve?
Sensory functions: innervates the laryngopharynx, superior larynx, heart and gastro-intestinal tract.
Special sensory functions: Afferent fibres from root of tongue and epiglottis.
Motor functions: Pharynx and Larynx
Parasympathetic functions: Innervation to the SAN and AVN of the heart, stimulate smooth muscle contraction and glandular secretions in the majority of the abdominal organs (foregut and midgut).
What is the ligament arteriosus?
The ligamentum arteriosum is a fibrous connection between the left pulmonary artery and the arch of the aorta. It is a remnant of the ductus arteriosum, a temporary structure (unused within 3 weeks after birth) which shunts blood from the pulmonary trunk to the aorta in the fetus to avoid it circulating through the inactive lungs.
