Thorax Flashcards
What is the thorax?
Region of the trunk that includes the sternum (breastbone), costal cartilages, ribs, thoracic vertebrae and the structures they enclose.
Name of cartilage that connects ribs to sternum
Costal cartilages (hyaline)
What are the boundaries of the thorax?
the superior thoracic aperture (root of neck) and inferior thoracic aperture / thoracic outlet (closed by diaphragm)
3 compartments of the thorax
left and right pleural cavities (location of lungs) and mediastinum (location of heart)
Why the superior thoracic aperture continuous with the neck?
To allow a communication between the neck and thorax for blood supply and drainage.
What structures make up the border of the superior thoracic aperture?
1st thoracic vertebrae (T1), 1st pair of ribs, manubrium
What is the name of the indent at the superior border of the manubrium?
Jugular notch
How many ribs are there?
12 pairs - 7 are true ribs, 3 are false ribs, 2 are floating ribs
Name of the structure that connects the upper limbs to the thoracic cage
pectoral girdle
What are the bones of the pectoral girdle?
Clavicle (collarbone) and scapula (shoulder bone)
3 parts of the sternum
Manubrium, body, xiphoid process
What is the sternum?
Bone that lies in the anterior midline of thorax and forms part of the ribcage.
What is the sternal angle?
Where the 2nd rib costal cartilage attaches and the manubrium articulates with the body of the sternum. The sternal angle can be palpated.
Name of the joint between rib and costal cartilage
costochondral joint
What is the space between the ribs called?
Intercostal space
Why are rib pairs 1-7 known as true ribs?
They attach directly to the sternum via their own costal cartilage
Why are rib pairs 8-10 known as false ribs?
They articulate indirectly to the sternum by connecting to the costal cartilages of the ribs above.
Why are rib pairs 11 and 12 known as floating ribs?
They do not articulate with the sternum or the costal cartilages of other ribs and instead terminate in musculature.
Why is the thorax described as being unusually shaped?
The inferior thoracic aperture, bordered by the diaphragm, has a curved, unsymmetrical shape (due to liver).
What are the intervertebral discs?
Made of fibrocartilage which compress under weight - weight bearing role
What is the mediastinum?
Area found in midline of thoracic cavity, surrounded by the left and right pleural cavities.
How is the mediastinum divided?
Superior mediastinum extends from the first rib to T4. Inferior mediastinum extends from T4 - T9 (superior to inferior) and from the sternum to pericardium (anterior to posterior). Inferior mediastinum is further divided into anterior, middle and posterior mediastinum.
Which structures are found in the superior mediastinum?
Trachea, carotid artery, aortic arch, pulmonary artery, subclavian artery, thymus.
What structures are found in the anterior mediastinum?
remnants of thymus
What structures are found in the middle mediastinum?
Heart, pericardium, ascending aorta, pulmonary trunk
What structures are found in the posterior mediastinum?
descending aorta and oesophagus
Names of great vessels
venae cava, pulmonary trunk which bifurcates into L and R pulmonary arteries, pulmonary veins (usually 2 on each side), aorta
Which vessels branch from the arch of aorta?
Brachiocephalic trunk which branches into the right subclavian and right common carotid arteries. The left common carotid artery and left subclavian artery directly branch off the aortic arch.
What structures do the left and right subclavian arteries supply?
Arms and part of the head and neck.
What structures do the left and right common carotid arteries supply?
Head and neck
Where does the aorta originate from?
Left ventricle
Where do the coronary arteries originate?
From the sinuses near the aortic valves.
Where does the pulmonary trunk originate from?
Right ventricle
Which veins drain the head and neck?
The left and right internal jugular veins
Which veins merge to form the superior vena cava?
The left internal jugular vein merges with the left subclavian vein to form the left brachiocephalic vein. The same happens on the right. The left and right brachiocephalic veins merge to form the superior vena cava.
Which great vessels penetrate the diaphragm?
inferior vena cava and descending aorta
Which veins drain the arms?
the left and right subclavian veins
How many pulmonary veins are there typically?
4 - 2 on the right and 2 on the left.
What is the name of the paired muscle that causes neck movement?
Longus colli
Where is the longus colli found?
Anterior vertebral column
What happens if there is unilateral contraction of the longus colli?
Neck rotates to contralateral (opposite) side - e.g. if left side contracts, neck turns to the right
What happens if there is bilateral contraction of the longus colli?
This flexes the neck bringing the chin to the chest
What is the biggest lymphatic vessel in the body?
Thoracic duct - drains lymph from most of body
Where does the sympathetic trunk extend from and to?
Arises from T1 and extends towards L2
Function of sympathetic trunk
responsible for flight or fight response (increases heart rate, increases respiratory rate and decreases blood flow to GIT)
What is the left vagus nerve?
CNX and a parasympathetic nerve
Function of the left vagus nerve
rest and digest - decreases heart rate and respiratory rate and increases gut motility and digestion.
Which veins unite to form the hemiazygos vein?
Left lumbar ascending vein (lumbar veins from lower back) and left subcostal vein (drains region beneath 12th rib)
Where does the hemiazygos vein drain into?
Azygos vein
Where does the accessory hemiazygos (aka superior hemiazygos) vein pass through?
Moves through the posterior mediastinum where it receives tributaries. Usually crosses the midline and drains into the azygos vein at level of T7 vertebra.
Tributaries that join the accessory/superior hemiazygos vein
5th, 6th, 7th, 8th posterior intercostal veins, left superior intercostal vein and left bronchial veins.
What area does the hemiazygos vein drain?
posterior trunk muscles and skin
What is the greater splanchnic nerve?
Paired visceral nerves carrying autonomic fibres and sensory fibres from the internal organs (abdominal organs specifically). Receives contributions from T5-8 spinal nerves.
What are the 3 main thoracic splanchnic nerves?
greater, lesser and least splanchnic nerve. all carry sympathetic fibres.
Which is the largest and most superior splanchnic nerve?
greater splanchnic nerve
Which structures do the internal thoracic vessels supply and drain?
skin and muscles of anterior thoracic cage and superior abdominal wall (ribs, breasts, parietal pleura, sternum, pericardium, thymus)
What is the left auricle?
extension of the left atrium utilised in times of stress.
Where does the phrenic nerve originate?
C 3, 4, 5 (cervical nerves)
Which nerve innervates the diaphragm?
Phrenic nerve
What is the pulmonary trunk?
Structure that carries deoxygenated blood from the right ventricle to the lungs and bifurcates into the left and right pulmonary arteries.
What is the recurrent laryngeal nerve?
Part of the vagus nerve innervating the muscles of the larynx and provides sensation to the larynx and below the vocal cords.
Why is the diaphragm described as a musculotendinous structure?
It is composed of muscle which converge to insert into a central tendon
Where do the muscle fibres of the diaphragm arise from?
From the costal margins (triangular part of costal cartilages) and the muscle fibres converge to insert into the central tendon
What is the shape of the diaphragm?
Dome-shaped on each side but higher on the right than the left
Why is the right dome of the diaphragm higher than the left dome?
the liver is positioned under the right dome
What type of muscle is the diaphragm made up of?
Skeletal muscle
What nerve fibres does the phrenic nerve contain?
Motor (movement) and sensory (sensation) fibres
What happens to the diaphragm during inhalation?
The diaphragm contracts and flattens which increases the volume of the thoracic cavity and decreases the pressure. So air flows in.
What happens during exhalation?
Diaphragm relaxes becoming dome-shaped, which alongside the elastic recoil of the lungs, expels the air.
Where does the aorta penetrate the diaphragm?
At the aortic hiatus which is anterior to the vertebral column
What is the name of the fold where tissue can accumulate in clinical cases?
Costodiaphragmatic recess
What forms the costodiaphragmatic recess?
Diaphragmatic pleura converges with the costal pleura creating the fold.
