Thorax, Pleural Cavity, Lungs Flashcards
What does the thorax protect?
Heart, lungs, liver on the right, spleen on the left, among other organs
What is the thoracic inlet?
The hole by which the thoracic cavity communicates with the front of the neck. Bounded by TV1, the first pair of ribs, and the upper margin of the manubrium
What is the thoracic outlet? What encloses it?
The means by which the thoracic cavity communicates with the abdomen.
Enclosed by diaphragm, TV12, ribs 12, and the edge of the lower 6 ribs + xiphisternal joint
What forms the costal margin?
The costal cartilages of 7-10. Ribs 8-10 are false ribs, 11-12 are floating ribs
What are the two joints formed by the body of the sternum?
- Manubriosternal - fibrocartilaginous joint between manubrium and sternum
- Xiphisternal - cartilaginous joint between xiphoid process and sternum
What are the two notches of the manubrium which are important?
- Suprasternal notch
2. Clavicular notch - site of sternoclavicular joint
What forms the body of the sternum?
Four fused sternebrae
What is the sternal angle?
Also called the angle of louis, it is the angle between the manubrium and sternum which is a palpable landmark for the second costal cartilage. Ribs and intercostal spaces are counted from here
How is the heart accessed for a heart surgery?
Via a median sternotomy - allows access to heart
What are the structures on a typical rib?
Head articulates with vertebral body of thoracic vertebrae.
Tubercle is a posterior projection at the junction of the neck and shaft, articulates with transverse costal facets
Subcostal groove on shaft which contains neurovascular bundle
Angle is where rib turns sharply anteriorly, right before shaft
What type of joint is the costovertebral joint and what does it articulate with?
Synovial - head of rib articulates with bodies of two adjacent vertebrae and the intervertebral disc, The tubercle articulates with transverse process of corresponding vertebrae
What are the sternocostal joints?
Synovial joints between costal cartilages 2-7 and lateral margin of sternum
What are costochondral joints?
Hyaline cartilage joints between ends of bony rib and costal cartilage
What are interchondral joints?
Synovial joints between cartilages of 7-10 at costal margin (to hold onto false ribs)
What is the function of the joints at the sternum + the costal cartilage?
Allow for respiration, add resilience to protect the sternum and ribs from more frequent fracture. With age, they may ossify with age
What is flail chest?
At least 2 fractures per rib and at least 2 ribs, making a section of chest wall no longer contribute to inspiration.
What are the external intercostal muscles and their function?
Muscles with fibers running downward and forward, from the superior rib to the rib below. They elevate during the ribs during inspiration.
They end anteriorly as the external intercostal membrane near the sternal articulation
What are the internal intercostal muscles and their function?
Muscles with fibers running upward, from the rib inferiorly to the rib superiorly. They are active in expiration
They end posteriorly as the internal intercostal membrane near the vertebral articulation
What are the innermost intercostal muscles and their function? What innervates all of these muscles?
Muscles with the same orientation as the internal intercostals, active in expiration.
Intercostal nerves innervates them all
What are the transverse thoracis muscles?
Muscles extending from posterior aspect of xiphoid process and lower sternum to costal cartilages 4-8, depressing costal cartilages
Where is the neurovascular bundle of the ribs located? Where should a needle be inserted during thoracentesis?
Between the inner and innermost intercostal muscles. The vein, artery, and nerve (VAN superior to inferior) are protected by the subcostal groove of the rib. Thus, inserting a needle above the upper border of the rib will prevent injury to vessels and nerve
What do the ventral rami of the thoracic spinal nerves become? Where do they travel?
The intercostal nerves. They are both sensory and motor, and they course around the chest wall in the neurovascular plane (subcostal groove)
What nerves supply the skin? The parietal pleura?
The anterior and lateral cutaneous branches, which are branches of the intercostal nerves. This supplies the costal and diaphragmatic parietal pleura.
What nerves supply the anterior abdominal wall including the skin, muscle, and parietal peritoneum?
Thoracic nerves 7-11 supply this area (the intercostal nerves).
What do the dorsal rami of the thoracic nerves supply?
Skin and muscle of the back
What intercostal nerves supply the skin at the level of the umbilicus? At the suprapublic level?
T10 - umbilicus
T12 - suprapubic
Where do the anterior intercostal arteries arise from?
Internal thoracic artery, off the first part of the subclavian
Where do the posterior intercostal arteries arise from? How about the first two specifically?
Thoracic aorta.
However, the first 2 PIAs arise from the supreme intercostal artery which is a branch of the costocervical trunk of subclavian
What is the fate of the internal thoracic artery?
Branches from 1st part of subclavian, descends lateral to sternal margin behind the upper 6 costal cartilages (gives off first 6 posterior intercostal arteries), before dividing into the musculophrenic and superior epigastric arteries
What is the pericardiophrenic artery?
An early branch of the internal thoracic artery, accompanying the phrenic nerve
What artery supplies the sternum, thymus gland, and overlying skin of chest wall?
Internal thoracic artery
Where do the posterior intercostal veins drain on the right and left?
Right: Azygos vein
Left: Hemiazygos vein
Where do the anterior intercostal veins drain?
Internal thoracic veins / musclophrenic veins
How can blood be supplied to the body whenever there is an obstruction of the thoracic aorta?
How will patients present?
Anastomoses between anterior and posterior intercostal arteries, as well as between superior and inferior epigastric arteries (drain into common femoral). Thus, ultimately this is a bypass of the obstruction via the internal thoracic artery (obstruction is distal to aortic arch)
-patients will have very prominent posterior intercostal arteries and lower pressures in lower limb
Where are lymph nodes of the thorax located?
Along internal thoracic artery
Where is the parietal layer of pleura continuous with the visceral layer? What does it form?
At the hilum of the lung (where it is supplied by the bronchi). It forms a cuff around the root of the lung, where structures enter and leave
What is the pulmonary ligament?
A loose fold of pleura extending inferiorly from the root, attaching to the mediastinum, which allows for expansion of pulmonary veins
What is sensory to the parietal plurae, and where is the phrenic nerve sensory to it?
Mostly the intercostal nerves. The phrenic nerve is just sensory to diaphragmatic pleura except at the periphery near the costal margin, which is supplied by the intercostal nerve
What are the subdivisions of the parietal plurae?
- Cervical pleura (cupola) - apical portion that projects into neck above medial 1/3 of clavicle
- Costal pleura - covering inner surface of thoracic wall
- Diaphragmatic pleura - covers the upper surface of the diaphragm
- Mediastinal pleura - covers the mediastinum between sternum and thoracic spine (basically between the costal pleura)
What is the endothoracic fascia?
The fascial layer the separates the costal pleura from the innermost intercostal muscles
What is the suprapleural membrane?
Fascial membrane that extends above the cervical pleura, between transverse process of CV7 to inner border of first rib
What is the visceral pleura and what innervates it?
It is the pleural layer which closely invests the lung, and it is insensitive except to stretching. Innervated by autonomics
-Analogous to pia mater / CNS
Why can the lung be injured in a supraclavicular injury?
The cupola (cervical parietal pleura) and apex of lung extends 2-3 cm above the medial 1/3 of clavicle
How can disease of apex of the lung affect nerves?
Since 1st thoracic nerve (T1) and sympatheti trunk lie behind the cupola and apex, disease of the lung can spread to these nerves and cause Horner’s syndrome (sympathetic) or disease of intrinsic muscles of hand (ulnar nerve)
What is the costomediastinal recess? What side is it larger?
The space formed between the parietal and visceral pleura which is formed by the anterior reflection (behind sternum) between costal pleura and mediastinal pleura
It is larger on the left
What is the costodiaphragmatic recess?
The space formed between the parietal and visceral pleura which is formed by the inferior reflection / union of the costal and diaphragmatic pleura
Allow expansions during deep inspiration
At what level is the costomediastinal recess and why is it larger on the left?
Extends down to 5th cartilage, but on the left side the reflection deviates laterally at about the 4th-5th costal cartilage and thus is larger on that side
What are the surface markers for the costal / diaphragmatic reflection?
Midclavicular line: 8th rib
Midaxillary line: 10th rib
Posteriorly (lateral border of erector spinae): 12th rib
What are the surface markers for the inferior border of the lung?
Midclavicular line: 6th rib
Midaxillary line: 8th rib
Posteriorly (lateral border of erector spinae): 10th rib
Always 2 above the parietal pleural reflection, to form the costodiaphragmatic recess
What is a pneumothorax?
A tear / defect in visceral or parietal pleura which allows space between them, letting air in the recess and collapsing the lung
What is thoracentesis?
A pleural tap - withdrawal of fluid from the pleural cavity via insertion of needle at upper border of rib. Normally above 10th rib in midaxillary line to avoid lung
Why might a patient feel shoulder pain when there is a subphrenic abscess in the diaphragm?
The phrenic nerve innervates the diaphragm, which arises from C3-C5. Thus, nerve stimulation from its target my emanate into the shoulder region and be referred to those spinal nerves
What are all the surfaces of the lung?
Apex - extends into root of neck
Base - diaphragmatic surface
Costal Surface - Related to ribs
Mediastinal surface - related to vertebral column posteriorly and mediastinum anteriorly
What do the anterior and posterior borders of the lung separate? (Surfaces)
Costal surface from mediastinal surface
What does the inferior border of the lung separate?
diaphragmatic surface from costal surface
What is the arrangement of the root of the lung with respect to bronchi, pulmonary arteries, and pulmonary veins?
Bronchi: Posterior
Pulmonary arteries: Anterior and superior
Pulmonary veins: Anterior and inferior
What is root vs hilum? What covers the root?
Hilum = area on mediastinal surface where structures pass Root = tubular collection of structures that attach the lung to structures in the mediastinum
Root is covered by mediastinal pleura, continuous with visceral pleura at the hilum
What are the contents of each root of the lung?
1 pulmonary artery
2 pulmonary veins
1 primary bronchus
Bronchial vessels (for blood to lung), autonomic nerves, and lymphatics
What is related to the root of the lung on the right?
Anterior: Superior vena cava, phrenic nerve
Posterior: Vagus nerve
Arching over: azygos vein
What is related to the root of the lung on the left?
Anterior: phrenic nerve
Posterior: vagus nerve, descending aorta
Superior: Arch of aorta
What is the oblique fissure and what does it separate in the right and left lungs?
Fissure in lung which starts high posteriorly and intersects inferior border of lung anteriorly, approximating the medial border of scapula with arm raised.
Right (has horizontal fissure): Separates superior and middle lobes from inferior lobe
Left: Separates superior and inferior lobes
What is the horizontal fissure?
In right lung only, follows 4th intercostal space to make superior and middle lobes of the lungs. Extends from oblique fissure posteriorly to anterior border of lung
Where are sounds for each of the right lung lobes best heard?
Superior lobe: Upper anterolateral chest wall
Middle lobe: Lower anterolateral chest wall
Inferior lobe: Lower 2/3 posterior chest wall
What structures are related on the medial surface and apex of the right lung?
Medial: IVC, SVC, azygos vein, esophagus, heart
Apex: Right subclavian vessels go over cupola and apex of lung
What is the cardiac notch?
Left lung is smaller than right because of cardiac notch. The lower medial surface of the superior lobe is notched by the projection of the heart to the leftside of the body
What is the lingula of the left lung?
The medially directed “tongue” projection of the anterior border of the superior lobe
What is related to the medial surface of the left lung?
Heart, arch of aorta, thoracic aorta, and esophagus
Where does the trachea bifurcate and what projection is there?
At the level of the sternal angle (~T4 spinal)), it bifurcates into the R and L main bronchi.
Carina - posterior projection of last trachael cartilage at bifurcation
How does the right main bronchus differ from the left, and why is this important?
Right is wider, shorter, and more vertical than left (thus, it is more in line with trachea). Most likely, material that is aspirated will enter the right lung.
What is the primary bronchi’s dividing pattern?
Primary: splits into lobar (secondary) bronchi, which supply each lobe. 3 on right, 2 on left
Lobar (secondary): splits into segmental (tertiary) bronchi, which aerate bronchopulmonary segments. 10 on each side
What are bronchopulmonary segments?
Pyramidal shaped with apex toward lung root: there are 10 in each lung. They are aerated by a specific tertiary bronchus, and are supplied by an accompanying branch of the pulmonary artery. The pulmonary veins mainly travel between these segments.
Which bronchopulmonary segment is most likely to have aspirated material enter in a supine individual?
Superior segment of inferior lobe, since it arises from the posterior aspect of the lower lobe bronchus. Probably on the right side (due to nature of primary bronchi).
How is blood supplied to the visceral pleura and walls of the bronchopulmonary segments?
Bronchial arteries from the upper thoracic aorta
What is the venous drainage from the blood supply to the lungs? Why is this interesting?
1/3 - enters azygos system to be put in right atrium
2/3 - enters pulmonary veins and thus left atrium (represents 2% of cardiac output, and adds a small amount of deoxygenated blood to left atrium)
What do the vagus and sympathetic nerves innervate in the lungs? What are their actions?
Distributed to visceral pleura and muscular walls of bronchi + blood vessels
Vagus - constrictor to bronchial muscles, stimulates glandular secretion (parasympathetic)
Sympathetics - relaxes bronchial muscles (bronchodilator), reduces secretion
Sympathetics increase oxygen uptake - sympathomimetic drugs are used to treat asthma, while parasympathetic antagonists also help
What extra muscles come into play during forced inspiration?
Accessory muscles of respiration - scalenes, SCM, and serratus anterior which modify the thoracic cavity / pull up the sternum / ripcage
What causes air to flow in to the lungs?
Movements of chest wall and diaphragm result in increase in vertical, anteroposterior, and transverse diameters of thorax. This leads to negative intrapleural pressure (since cavity is larger and it can expand) and thus the lung expands to put more pressure on the pleural cavity to equalize.
What accounts for 2/3 of the expansion of the thoracic cavity? What accounts for the rest?
The vertical diameter is increased when the diaphragm contracts and descends
The rest is accounted for by pump-handle and bucket-handle movement
What is meant by pump handle movement of the chest? What joint facilitates it?
Elevation of upper ribs via the external intercostals pushes the sternum forward, thus increasing the anteroposterior diameter of the thorax. The manubriosternal joint facilitates it via hinge movement, which is impedes thoracic expansion if ankylosed
What is meant by bucket-handle movement?
Elevation of lower ribs via external intercostals increases the transverse diameter of the thoracic cavity
What group of muscles comes into play during forced expiration?
i.e. sneezing, aided by contraction of abdominal muscle, which act through the viscera, forcing the diaphragm upward
What is the eparterial bronchus?
It is the only secondary bronchi to branch outside the lung. It is called eparterial because it is directly above a lower pulmonary artery going into the right lung, and is the most superior bronchus. (All other bronchi are posterior and inferior to the arteries)
What tends to be larger: upper or lower lobe pulmonary arteries?
Lower lobe, due to gravity
What are the orientations of the pulmonary arteries in transverse section? How does this relate to veins?
Left: Transversely, seen going down from CT
Right: Posteriorly more pointing
Arteries are higher than veins. They tend to point more vertically than the veins. The veins point more horizontally
