Case 1 + 2- anatomy Flashcards
Borders of the thorax
Superior border- superior thoracic aperture
Inferior border- diaphragm
Anterior border- sternum
Posterior border- thoracic vertebrae
What’s in the thorax
Its split into the pleural cavity which contains the lungs and pleura. The other section is the mediastinum which is the mass of tissue in the thorax between the lungs and pleura.
What is the mediastinum split into
The superior mediastinum and inferior mediastinum. The inferior mediastinum is further split into the anterior, middle and posterior mediastinum.
How the location of the mediastinum changes
In the upright position, gravity causes the soft structures in the mediastinum to sag such that they fall to a lower vertebral level than when the patient is lying down. When a patient is lying on their side, gravity will also pull the mediastinal structures down towards that side.
Boundaries of superior mediastinum
Superiorly- superior thoracic inlet
Posteriorly- thoracic vertebra
Anteriorly- sternum
Blood vessels within the superior mediastinum
Contains the arch of Aorta which splits into the Brachiocephalic artery, the left common carotid artery and the left subclavian artery. Also contains the superior vena cava with the Braciocephalic vein, the left superior intercostal vein, the supreme intercostal vein (below BV) and the Azygos vein (drains the posterior thoracic wall).
Structures which are’nt blood vessels in the superior mediastinum
There is also the right vagus nerve which runs parallel to the trachea and passes posteriorly to the superior vena cava and the right primary bronchus. The left vagus nerve ascends anteriorly to the aortic arch before travelling posteriorly to the left bronchus. There are also the phrenic nerves, the cardiac nerves and the sympathetic trunk. You also have the thymus which lies flush against the sternum, the trachea which is posterior to the ascending aorta. There is also the oesophagus and the thoracic duct on its left.
Anterior mediastinum
Contains a bit of the Thymus (gets smaller in adults). It is posterior to the sternum and anterior to the middle mediastinum. No major structures just fat, connective tissue and lymph nodes.
Middle mediastinum blood vessels
Contains the start of the Aortic arch which then goes into the ascending aorta. Also contains the pulmonary trunk which gives rise to the left and right pulmonary arteries. Has the superior vena cava which is formed from the left and right brachiocephalic veins
Middle mediastinum structures which aren’t blood vessel
Contains the heart, pericardium and left and right bronchi. Contains the cardiac plexus which is a group of nerves at the base of the heart, the sympathetic nerves are from the spinal cord and the parasympathetic nerves are supplied by the vagus nerves. There are also phrenic nerves and the tracheobronchial lymph nodes which are associated with the trachea and bronchi
Posterior mediastinum borders
Posterior to the middle mediastinum and anterior to the thoracic vertebrae.
Posterior mediastinum blood vessels
Contains the thoracic aorta (descending aorta) which branches into the posterior intercostal arteries, the bronchial arteries, the oesophageal arteries and the superior phrenic arteries. It also contains the Azygos, hemiazygos, and accessory hemiazygos veins. The hemiazygos vein drains into the azygos vein at T8 and at T7 the accessory hemiazygos vein drains into azygos.
Posterior mediastinum structures which aren’t blood vessels
The oesophagus is posterior to the thoracic aorta, it exits at the oespheagal plexus. This is a network of nerves surrounding the oesophagus including branches from the left and right vagus nerves they converge to form the anterior vagal trunk and posterior vagal trunk, which travel along the surface of the oesophagus as it exits the thorax.
There is also the thoracic duct which originates from the cisterna chyli in the abdomen and enters the mediastinum through the aortic hiatus. It is to the right of the oesophagus.
The thoracic vertebra
They become bigger as you go down. C1-C7 is cervical, T1-T12 is thoracic, L1-L5 is lumbar, S1-S5 is sacral.
Aortic arch
Splits into the brachiocephalic trunk which splits further into the right common carotid artery and the right subclavian artery. The second branch is the left common carotid artery, the third branch is the left subclavian artery
The branching after the aortic arch
The common carotid artery supplies the head and neck, it splits into the internal and external carotid artery. The subclavian artery supplies the upper limb on each side of the body. The subclavian artery becomes the axillary artery and then the brachial artery. Numerous branches are also given off these arteries to supply the structures of the upper limbs.
Descending aorta
The descending thoracic aorta splits into the POSTERIOR INTERCOSTAL arteries, meaning they go in between the ribs, supplying the muscles of the thoracic walls. It then branches into the BRONCHIAL arteries. There are also OESOPHAGEAL branches and the MEDIASTINAL branches. The branches are named after the locations they are travelling to or supplying.
When does the abdominal aorta start
When it passes through the aortic hiatus of the diaphragm
Abdominal aorta
The aorta becomes the abdominal aorta when it passes through the aortic hiatus of the diaphragm. It first branches into the COELIAC trunk at T12, this supplies the stomach and the liver. The next branch is the SUPERIOR MESENTERIC artery at L1, this supplies the intestine. You also have the LUMBAR arteries which come of at each Lumbar section, to supply the posterior muscles. The INFERIOR MESENTERIC artery comes of at L3, supplies part of the intestine. You then have the COMMON ILIAC ARTERY (left and right) which supply the lower limb, it comes of at L5. You also have the GONADAL arteries. RENAL arteries come of at L1
What are the inferior and superior vena cava
Drain deoxygenated blood into the right atrium. Superior vena cava carry’s blood from the upper limbs, head and neck. The inferior vena cava drains from the lower limbs, abdomen and pelvis
Superior vena cava
The left internal jugular vein and left subclavian vein form the left brachiocephalic vein. The right internal jugular vein and right right subclavian vein form the right brachiocephalic vein. Both brachiocephalic veins join to for the superior vena cava
Inferior vena cava
The right and left common iliac vein join together. The lumbar and renal veins will then drain into the inferior vena cava. The Hepatic veins which drain the liver are a major tributary of the IVC. There are less veins then arteries as most will go through the liver and form the hepatic vein. The inferior vena cava passes through the diaphragm at T8 at the caval opening.
Connective tissue
Supports and binds structures in the body. It also insulates, stores reserve fuel and transports substances around the body. Specialised connective tissue may have other functions.
Connective tissue structure
Consists of cells that are far apart and surrounded by the extracellular matrix. Cell types and ECM components depend on type of connective tissue (CT). The extracellular matrix is made of collagen and elastin fibre (produced by fibroblasts). Within the outside of the substance you will have a ground substance which is made of water and glycosaminoglycans.
Loose connective tissue
They have large amounts of ground substance and fewer fibres, i.e. adipose (fat).
Dense connective tissue
They have large amounts of fibre and less ground substance, They are split into dense regular and dense irregular. The dense regular is very uniform with parallel fibres. The dense irregular is not tightly packed in straight line and is in a random order. This will be stuff like ligaments and collagen as its very strong
Specialised connective tissue
Cartilage and bone as well as blood and blood vessels. Have a particular function and structural makeup.
What is the pericardium
A fibrous sac which contains the heart and the route to the great vessels
Function of pericardium
- Fixes the heart in the mediastinum and limits its motion.
- Prevents overfilling of the heart.
- Lubrication. A thin film of fluid between the two layers of the serous pericardium reduces the friction of heart movement
- Protection from infection. The fibrous pericardium serves as a physical barrier between the muscular body of the heart and adjacent organs prone to infection, such as the lungs.
Layers of the pericardium
Fibrous pericardium- outer layer, continuous with the diaphragm and adventitia of the great vessels
Serious pericardium- inner layer
Serious pericardium is split into the viscera layer which is the innermost layer then we have the parietal layer which is on the inside of the fibrous pericardium.
