What is the bony thorax made up of?
- The thoracic vertebrae posteriorly
- The ribs and intercostal spaces laterally
- The sternum and costal cartilages anteriorly
What happens to the thoracic cage superiorly?
It is continuous with the neck, at the thoracic inlet
What happens to the thoracic cage inferiorly?
The diaphragm separates it from the abdominal cavity
How many ribs are there?
12
What do the ribs articulate with posteriorly?
The vertebral column
How do the ribs articulate with the vertebral column?
Via the costo-vertebral joints
What do the ribs articulate with anteriorly?
- Ribs 1-7 are connected to sternum
- Ribs 8-10 are connected to costal cartilage alone
- Ribs 11-12 have ends free in the abdominal muscles
How do ribs 1-7 connect to the sternum?
Via costal cartilages
What are ribs 11 and 12 known as?
Floating ribs
What ribs are considered ‘typical’?
3-9
What do typical ribs have?
- Head
- Neck
- Tubercle
- Shaft
What does the head of the rib have?
Two articular facets
What are articular facets at the head of the rib for?
Articulation with the body of the corresponding vertebrae, and the vertebrae above
What does the neck of the rib do?
Connects the head of the rib with the body
At what level does the neck of the rib connect the head and the body?
The level of the tubercle
What does the tubercle of the rib contain?
One articular facet
What is the purpose of the articular facet of the tubercle of the rib?
For articulation with the transverse processes of the corresponding thoracic vertebrae
What shape is the shaft of the rib?
Thin, flat, curved
What happens at the angle of the rib?
The shaft twists forward to form its characteristic curve
What does the shaft contain?
A costal groove
Where is the costal groove located?
Close to the lower border of the shaft of the rib
What does the costal groove do?
Protects the intercostal vessels and nerve
Label this diagram of a typical rib
- A - Crest of head
- B - Superior articular facet
- C - Tubercle
- D - Angle
- E - Cup for costal cartilage
What are the typical features of most thoracic vertebrae?
- Independant
- Have bodies, vertebral arches and seven processes
What are the 7 processes of the thoracic vertebrae for?
Muscular and articular connections
What are the characteristic features of thoracic vertebrae?
- Bilateral costal facets (demifacets)
- Costal facets
- Spinous processes
Where do the demifacets of thoracic vertebrae occur?
On the vertebral bodies, usually occuring in inferior and superior pairs
What is the purpose of the vertebral body demifacets?
Articulation with the heads of ribs
Where are the costal facets of thoracic vertebrae found?
On the transverse processes
What is the purpose of the costal facets of thoracic vertebrae?
Articulation with the tubercles of the ribs
Which ribs are atypical?
With respect to costal facets
The inferior two or three, as they do not articulate with costal facets
Describe the spinous process of thoracic vertebrae?
Long, inferiorly slanting
What connects ribs with thoracic vertebae?
Costovertebral joints
What kind of joints are costovertebral?
Synovial
When does movement take place at the costovertebral joints?
Movement of the ribs during respiration
What does the costovertebral joint consist of?
- Joint of the rib head
- Costotransverse joint
What articulates at the joint of the rib head?
The head of the rib articulates with the corresponding vertebrae, and the vertebrae above
What articulates at the costotransverse joint?
The articular facet of the tubercle of the rib and the transverse process of the corresponding vertebrae
Which ribs are atypical?
1, 2 and 10
Describe the shape of the first rib
Broadest, shortest, and most sharply curved rib
Describe the features of the first rib
- Single articular facet for articulation with the T1 vertebrae
-
Two transversely directed grooves crossing its superior surface for the subclavian vessels
- The grooves are seperated by the scalene tubercle
Label this diagram of the first rib
- A - Single facet on head
- B - Tubercle
- C - Scalene tubercle
- D - Grooves for…
- di - Subclavian vein
- dii - Subclavian artery
Describe the features of the second rib
- Two articular facets for articulation with the bodies of T1 and T2 vertebrae
- Rough area on its upper surface, the tuberosity for serratus anterior
Label this diagram of the second rib
- A - Head
- B - Neck
- C - Tubercle
- D - Tuberosity for serratus anterior
- E - Body
Describe the features of the 10th-12th ribs
Single articular facet (like 1st rib) for articulation with a single vertebrae
Describe the features of the 11th and 12th rib?
Short, with no neck or tubercle
What does each intercostal space contain?
Regarding muscles
3 muscles
What are the 3 muscles of the intercostal spaces?
- External intercostals
- Internal intercostals
- Innermost intercostals
When are external intercostals used?
During breathing
Inspiration
In which direction do the fibres of the external intercostal muscles run?
Downwards and anteriorly from above rib, to the one below
What is the action of the external intercostal muscles?
Elevate the ribs in a ‘bucket handle’ type movement, to increase anteroposterior and transverse diameters of the chest
What are the external intercostal muscles responsible for during quiet respiration?
30% of chest expansion
When are the internal intercostal muscles used?
During breathing
During forced expiration
In which direction do the fibres of the internal intercostal muscles run?
Downwards and posteriorly, from above rib to the one below
What is the action of the internal intercostal muscles?
Pulls rib down from the position of chest expansion
When are the innermost intercostals used?
During forced expiration
What are the innermost intercostal muscles similar to?
Internal intercostals, but less well developed
What is the nerve supply of the intercostal muscles?
Intercostal nerves
Label this diagram
- A - Anterior ramus (intercostal nerve)
- B - Muscular branch
- C - Internal intercostal muscle
- D - External intercostal muscle
- E - Internal intercostal muscle
- F - Lateral cutaneous branch
- G - Innermost intercostal muscle
- H - Transversus thoracis muscle
- I - External intercostal membrane
- J - Posterior ramus
- K - Sympathetic trunk
- L - Sternum
What is the main muscle of inspiration?
The diaphragm
What is the result of contraction of the diaphragm?
Descent
What does the diaphragm contraction account for during quiet respiration?
70% of chest expansion
Where are the openings in the diaphragm?
- T8 - Vena Cava
- T10 - Oesophagus
- T12 - Aorta (Aortic hiatus)
What is the diaphragm made up of?
- Vertebral part
- Costal part
- Sternal part
What does the vertebral part of the diaphragm arise form?
The crura and the Arcuate ligaments
What does the costal part of the diaphragm arise from?
The inner aspects of the 7-12 costal cartilages
What does the sternal part of the diaphragm arise from?
The deep surface of the xiphisternum
What is the nervous supply of the diaphragm?
From the phrenic nerve, C3, 4, 5.
Remember, C3, 4, 5, keeps you alive
What is the motor function of the phrenic nerve?
Supplies the diaphragm
What is the sensory function of the phrenic nerve?
Supplies both sides of the diaphragm, and the mediastinal/diaphragmatic part of the parietal pleura
What lies in the intercostal groove of the rib?
The intercostal vein, artery and nerve
In that order- remember VAN
Where do the intercostal vein, artery, and vein?
Which part of the rib
Along the lower border
What is the clinical importance of the intercostal vein, artery and nerve running along the lower border of the rib?
Important to remember when carrying out pleural aspiration or insertion of a chest drain, when the needle should be inserted at the upper border of the rib to avoid injury
Label this diagram
- A - Subcostal muscle
- B - Posterior intercostal vein and artery
- C - External intercostal muscle
- D - Internal intercostal muscle
- E - Innermost intercostal muscle
- F - Intercostal nerve
- G - Collateral nerve and vessels
- H - Costal groove
How many intercostal nerves are there?
12
Where do the intercostal nerves originate from?
The anterior rami of the thoracic spinal nerves T1 - T12
What do the intercostal nerves supply?
The intercostal muscles in the corresponding space, the parietal pleura, and the overlying skin
What does each intercostal space contain?
Regarding arteries
An anterior intercostal artery (except the last two)
What do the anterior intercostal arteries anastomose with?
A posterior intercostal artery
What do the intercostal arteries supply?
The intercostal muscles, parietal pleura, and overlying skin
How do the anterior intercostal arteries arise?
Brachiocephalic/aortic arch → Subclavian → Internal thoracic/musculophrenic → anterior intercostal
What do the posterior intercostal arteries arise from?
- 1st- 2nd spaces; Brachiocephalic/aortic arch → Subclavian → Costocervical trunk → Superior intercostal → Posterior intercostal
- Other spaces; Thoracic aorta → Posterior intercostal
What does each intercostal space contain?
Regarding nerves
Two anterior and one posterior vein accompanying the arteries
How do the anterior intercostal veins drain?
Via the Internal Thoracic Vein, into the right subclavian vein
How do most posterior intercostal veins drain?
Via the Azygous vein on the right, and the Hemiazygous on the left, into the superior vena cava
Label the veins on this diagram
- A - Right internal jugular
- B - Left brachiocephalic
- C - Right subclavian
- D - Right brachiocephalic
- E - Right superior intercostal
- F - Superior vena cava
- G - Left superior intercostal
- H - Azygous
- I - Posterior intercostal
- J - Accessory hemiazygous
- K - Anterior intercostal
- L - Hemiazygous
- M - Internal thoracic
- N - Subcostal
- O - Right renal
- P - Inferior vena cava
What is the pleura?
A serous membrane
What does the pleura consist of?
A single layer of mesothelial cells, with a thin layer of underlying connective tissue
What does the parietal plerua line?
The inside of each hemithorax
What does the hemithorac consist of?
The bony thoracic cage, diaphragm, and mediastinal surface
What does the perietal pleura become continuous with?
The visceral pleura
Where does the parietal pleura become continuous with the visceral plerua?
At the hilum of the lung
What does the visceral pleura line?
The outside of the lung
Where does the visceral pleura extend?
Between the lobes of the lung, into the depth of the oblique and horizontal fissures
What is the blood supply of the pleura?
Via the intercostal and internal thoracic arteries and veins
What is the innervation of the perietal pleura?
Both somatic (Intercostal and Phrenic nerves) and autonomic
What is innervation of the visceral pleura?
Autonomic
No somatic innervation
What is the pleural cavity (or space)?
A potential space between the two layers of pleura that are continuous at the hilum
What are both layers of pleura covered with?
A common film of fluid
What is the fluid covering the layers of pleura produced from?
The parietal surface
What is the fluid covering the layers of pleura absorbed by?
The parietal lymphatic vessels
What does the pleural fluid allow?
The two layers to slide on one another, thus in health the pleura allows movement of the lung against the chest wall while breathing
What does the surface tension of the pleural fluid provide?
The cohesion that keeps the lung surface in contact with the thoracic wall
What is the result of the surface tension of the pleural fluid keeping the lung surface in contact with the thoracic wall?
When the thorax expands in inspiration, the lung expands along with it and fills with air
Do the lungs occupy all the available space in the pleural cavity?
No, even in deep inspiration
Label this diagram
- A - Pleural cavity
- B - Collapsed lung
- C - Visceral pleura
- D - Perietal pleura
- E - Thoracic wall lined with endothoracic fascia
- F - Phrenicopleural fascia (part of endothoracic fascia
- G - Mediastinum (contains heart)
- H - Diaphragm
- J - Visceral pleura
- K - Parts of parietal pleura
- ki - Diaphragmatic part
- kii - Costal part
- kiii - Medistinal part
- kiv - Cervical pleura
- L - Suprapleural membrane
- M - Hilum of lung (site of entry of root of lung)
- Orange - Visceral pleura
- Purple - Perietal pleura
- Blue - Costal pleura
- Green - Diaphragmatic pleura
- Red - Mediastinal pleura
- Yellow - Cervical pleura
- Solid - Fascial membranes (Suprapleural and mediastinal fascia, fibrous pericardium)
- Dotted - Endothoracic fascia
What are the lines of pleural reflection?
The relatively abrupt lines along which the perietal pleura changes direction (reflects) as it passes from one wall of the pleural cavity to another
How many lines of pleural reflection are there?
3 on each side
Name the lines of pleural reflection
- Sternal
- Costal
- Diaphragmatic
Label this diagram
- A - Common carotid artery
- B - Internal jugular artery
- C - Subclavian artery
- D - Subclavian vein
- E - 1st rib
- F - 4th rib
- G - Horizontal fissure
- H - Right lung (covered with visceral pleura)
- I - 6th rib
- J - Oblique fissure
- K - Right vertebral line of pleural reflection
- L - Costal attachment of diaphragm
- M - 10th rib
- N - Vertebral attachment of diaphragm
- O - Vertebrae (T12)
- P - Left costal line of pleural reflection
- Q - Lingula (of superior lobe)
- R - Apex of heart
- S - Bare area of pericardium
- T- Oblique fissure
- U - Cardiac notch of left lung
- V - Left lung (covered in visceral pleura)
- W - Right and left sternal lines of pleural reflextion
- X - Apex of left lung covered by cervical pleura (pleural cupula)
- Red - Lines of (parietal) pleural reflection
- Yellow - Outline of heart (pericardium)
What does each lung have?
- An apex
- A base
- Lobes
- Three surfaces
- Three borders
Where does the apex of each lung extend?
Above the level of the 1st rib into the neck
What is the base of the lung?
A concave, inferior surface
Where is the base of the lung?
Resting on the diaphragm
How many lobes does the lung have?
- Left has two
- Right has three
What are the lobes of the lungs created by?
One (left) or two (right) fissures
What are the surfaces of the lungs?
- Costal
- Mediastinal
- Diaphragmatic
What are the borders of the lungs?
- Anterior
- Inferior
- Posterior
What divides the right lung into it’s three lobes?
A right oblique and horzontal fissure
What divides the left lung into its two lobes?
A single left oblique fissure
What are the lobes of the right lung named?
- Superior
- Middle
- Inferior
What are the lobes of the left lung named?
- Superior
- Inferior
What is the hilum of the lung?
A wedge-shaped area on the mediastinal surface of each lung
What is the function of the hilum of the lung?
It is a passageway through which structures forming the roots of the lung enter or exit
What do the roots of the lung consist of?
- Bronchi
- Pulmonary arteries
- Superior and inferior pulmonary veins
- Pulmonary plexus of nerves and lymphatics
Label this diagram
- A - Horizontal fissure
- B - Superior lobe
- C - Middle lobe
- D - Inferior lobe
- E - Oblique fissure
- F - Lingula
- G - Inferior lobe
- H - Cardiac notch
- I - Superior lobe
- J - Oblique fissure
Where does the trachea begin?
At the lower border of the cricoid cartilage in the neck
How does the trachea terminate?
By dividing into the right and left main bronchi at the level of sternal angle
What holds the trachea open?
By C-shaped cartilage rings, supported posteriorly by the trachealis muscle
What is the trachea lined with?
Pseudostratified ciliated epithelia
What is the carina?
The angle between the right and left main bronchi
How does the right main bronchus differ from the left?
It is shorter, wider and more vertical
What is the consequence of the differences between left and right bronchi?
Any inspired objects are more likely to fall into the right main bronchus
How long is the right main bronchus?
2.5cm
What happens to the right main bronchus before reaching the hilum of the lung?
It gives off its upper lobar branch
How long is the left main bronchus?
5cm
Where does the left main bronchus pass?
Below the arch of the aorta, anterior to the descending aorta and oesophagus
What do the left and right main bronchi divide into?
Lobar bronchi, one for each lobe
What do the lobar bronchi divide into?
Segmental bronchi
What do the segmental bronchi branch into?
Sub-segmental bronchi
What do the sub-segmental bronchi divide into?
Bronchioles
What do the bronchioles divide into?
Terminal bronchioles
What do the terminal bronchioles divide into?
Alveolar ducts
What do the alveolar ducts divide into?
Alveoli
What blood vessels service the lung?
Each lung has a pulmonary artery supplying blood to it, and two pulmonary veins draining blood from it
What do the pulmonary arteries arise from?
The pulmonary trunk
Where do the pulmonary arteries arise from the pulmonary trunk?
At the level of the sternal angle
What do the pulmonary arteries carry?
Low-oxygen blood to the lungs
What is the purpose of the pulmonary arteries carrying low-oxygen blood to the lungs?
For oxygenation
What course do the pulmonary arteries take?
They become part of the root of each lung before splitting into lobar arteries, and subsequently segmental arteries
How are the arterie and bronchi related in each lung?
They are paired, branching simulataneously and running parallel courses
Name the pulmonary veins
- Superior
- Inferior
What do the pulmonary veins do?
Carry oxygen-rich blood back to the heart
Where is the middle lobe vein found?
In the right lung
What is the middle lobe vein a tributary of?
The right superior pulmonary vein
How are the pulmonary veins related to the pulmonary arteries and bronchi?
They are not- they are independant
What do the bronchial arteries supply blood too?
- The structures making up the root of the lungs
- Suppoting tissues of lungs
- Visceral pleura
Where do the bronchial arteries pass?
Typically, along the posterior aspects of the main bronchi
How many left bronchial arteries are there?
2
Where do the left bronchial arteries arise from?
Directly from the thoracic artery
How many right bronchial arteries are there?
1
Where does the right bronchial artery arise from?
The 3rd intercostal artery, arising from the thoracic aorta
What are the groups of the bronchial veins?
- Superficial
- Deep
What do the superficial group of the bronchial veins do?
Drain visceral pleura and the bronchi in the hilar region to the Azygous vein on the right, and the accessory Hemiazygous on the left
What do the deep group of the bronchial veins do?
Drain the rest of the bronchi (deep in the lung, not in the hilar region) into the main pulmonary vein, or directly into the left atrium
How is most of the blood supplied by the bronchial arteries returned?
Via the pulmonary veins, rather than the bronchial ones
Label this diagram
- A - Right superior posterior intercostal artery
- B - Run on posterior aspect of main bronchi
- C - Arch of aorta
- D - Left superior intercostal artery
- E - Bronchial arteries
- F - Esophageal artery
- G - Thoracic aorta
What is the mediastinum?
The central compartment of the thoracic cavity
What covers the mediastinum on each side?
The mediastinal pleura
What does the mediastinum contain?
All of the thoracic visceea and structures, except the lungs
What is true of the mediastinum in living people?
It is highly mobile
Why is the mediastinum highly mobile in living people?
As it consists primarily of hollow, visceral structures, united only by loose connective tissue, often infiltrated by fat
Where does the mediastinum extend?
- From the superior thoracic aperture to the diaphragm
- From the sternum and costal cartilages anteriorly to the bodies of the thoracic vertebrae posteriorly
What is the mediastinum divided into?
Superior and inferior parts
Label this diagram
- A - Cervical pleura
- B - Apex of lung
- C - Manubrium
- D - Sternal angle
- E - Sternum (body)
- F - Xiphoid process
- G - Superior mediastinum
- H - Inferior mediastinum
- I - Superior thoracic aperture
- J - Superior mediastinum
- K - Sternum
- ki - Manubrium
- kii - Angle
- kiii - Body
- L - Inferior mediastinum
- li - Anterior mediastinum
- lii - Middle mediastinum
- liii - Posterior mediastinum
- M - Xiphoid process
- N - Diaphragm
- O - Transverse thoracic plane
Where does the superior mediastinum extend?
Inferiorly from the superior thoracic aperture to the transverse thoracic plane
What is the transverse thoracic plane?
A horizontal plane
What does the transverse thoracic plane include anteriorly?
The sternal angle
Where does the transverse thoracic plane pass posteriorly?
Approximately through the junction of the T4 and T5, through the intervertebral disk
Where does the inferior mediastinum extend?
Inferiorly from the transverse thoracic plane to the diaphragm
What further subdivides the inferior mediastinum?
The pericardium
What is the inferior mediastinum further subdivided into?
- Anterior
- Middle
- Posterior
What does the middle inferior mediastinum contain?
The heart, and roots of its great vessels
How can some structures lie in more than one mediastinal compartment?
They pass vertically through the mediastinum, for example the oesophagus
How much of the cardiac output must the pulmonary circulation accept?
All of it
At what resistance does the pulmonary circulation operate?
Low
What allows the pulmonary circulation to work at low resistance?
- Short, wide vessels
- Lots of capillaries connected in parallel
- Arterioles with relatively little smooth muscle
What is the result of the low resistance of the pulmonary circulation?
It operates at a lower pressure