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Anatomy (MPAS) > Anatomy of thorax and mediastinum > Flashcards

Anatomy of thorax and mediastinum Flashcards

1
Q

What is the function of the thorax?

A

Protects the lungs, great vessels, liver and spleen

Provides the mechanical function of breathing

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2
Q

What are the skeletal components of the thoracic wall?

A

12 thoracic vertebrae

12 pairs of ribs

Sternum (manubrium, body and diploid process)

See figure

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3
Q

Parts of the manubrium and the sternum

A

Manubrium:

Jugular notch

Clavicular notch

First costal notch

Sternal angle (angle of louis)

Manobriosternal joint

Sternum:

Body

2nd-7th costal notches

Xiphisternal joint

Xiphoid process

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4
Q

What passes to the right and behind the manubrium?

A

The aortic arch

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5
Q

What does the xiphisternal joint mark?

A

The centre of the diaphragm

Marks how high the liver goes

Left side of process = inferior border of the heart

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6
Q

What are the two parts of a rib?

A

Bony part (costo-)

Cartilage part (chondro-)

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7
Q

Where do the 12 pairs of ribs attach posteriorly? Type of joints?

A

Thoracic vertebrae

Mostly synovial

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8
Q

What is the diameter of the thoracic cage?

A

Not equal

More narrow superiorly

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9
Q

Parts of typical rib

A

Head

Neck

Costal tubercule

Costal angle

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10
Q

What do the facets of the head of the rib articulate with?

A

Two facets are separated by the crest of the head

One facet articulates with the body of the numerically corresponding vertebrae

Other facet articulates with the superior vertebrae

See figure

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11
Q

Role of costal tubercle of typical ribs

A

Located at the junction of the neck and body.

Has a smooth articular part for articulating with the corresponding transverse process of the vertebra (via a synovial joint)

Rough non-articular part for a fibrous attachment to the process via the costotransverse ligament

See figure

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12
Q

Typical and atypical ribs

A

Typical: 3-9

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13
Q

What are the true ribs? What joints to they form

A

aka Vertebrosternal ribs

1st to 7th ribs

attach directly to the sternum anteriorly through their own costal cartilages.

Form sternochondral joints

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14
Q

What are the false ribs?

A

aka Vertebrochondral ribs

8-10th ribs

cartilages on their anterior ends that are joined to the cartilage of the rib just superior to them

connection with the sternum is indirect.

synchondrosis (immovable joint)

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15
Q

What are the floating ribs?

A

11th and 12th, sometimes the 10th

Rudimentary cartilages on their anterior ends that do not connect even indirectly with the sternum

instead, they end in the posterior abdominal musculature.

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16
Q

What are the distinguishing features of the 2nd rib

A

Has formations for attachment of serrates anterior and posterior scalene muscles

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17
Q

What are the costal grooves of the ribs for?

A

To protect intercostal vessels and nerves

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18
Q

What is the role of the costal cartilage?

A

Prolong ribs anteriorly

Contribute to the elasticity of the thoracic wall

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19
Q

Thoracic cavity during inspiration

A

Inspiration: The vertical dimension (height) of the central part of the thoracic cavity increases during as the contracting diaphragm descends

Elevation of sternum causes the anteroposterior (AP) dimension of the thorax to increase considerably (pump-handle movement)

Elevation of the lateral portion of the lower ribs causes the transverse dimension of the thorax to increase (bucket-handle movement)

See figures

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20
Q

Which muscles of the thoracic wall work during inspiration?

A

Elevation of ribs

Scalenus muscles (forced inspiration)

External intercostal muscles

See figures

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21
Q

Which muscles of the thoracic wall work during forced expiration?

A

Internal intercostal muscles

Innermost intercostal muscles

Transverse thoracic muscle

Subcostal muscles

See figures

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22
Q

What are the muscles of the thoracic wall innervated by?

A

Intercostal nerves

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23
Q

What are the scalenus muscles innervated by?

A

Cervical plexus

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24
Q

What do the scalene muscles attach to?

A

1st rib: anterior and middle scalene

2nd rib: posterior scalene

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25
Q

Three layers of muscles in the intercostal spaces

A

outer layer: External intercostals

middle layer: internal intercostal

deepest: innermost intercostals

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26
Q

Orientation of muscle fibres of intercostal muscles?

A

External: infero-anterior (putting hands in pockets)

Internal: infero-posteriorly

Deepest: similar to internal (internal to the intercostal vasculature)

See figure

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27
Q

What structures form the thoracic inlet?

A

Thoracic inlet = superior aperture of thorax

First thoracic vertebra, upper margins of first ribs and manubrium of sternum

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28
Q

What structures form the thoracic outlet?

A

12th thoracic vertebrae behind

11th and 12th ribs on the sides

cartilages of the 10th, 9th, 8th and 7th ribs (ascend on each side and form an angle into the apex)

Outlet slopes obliquely downward and backward

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29
Q

What closes the thoracic outlet?

A

Diaphragm (forms floor of thorax)

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30
Q

What is the principal muscle of respiration?

A

Diaphragm

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31
Q

Diaphragm and respiration

A

Inspiration: diaphragm contracts and flattens. This increases the vertical diameter of the thoracic cavity, producing lung expansion and air is drawn in.

Expiration: diaphragm passively relaxes and returns to its original dome shape. Reduces volume of thoracic cavity

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32
Q

Dome of diaphragm? Need to ask about this

A

Level of T8 on right side

Level of T9 on left side

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33
Q

Parts of diaphragm

A

Central tendon: fused with the inferior part of the fibrous pericardium

Sternal part: two muscular slips that attach to posterior aspect of diploid process

Costal part: wide muscular slips that attach to the internal surfaces of the inferior six costal cartilages and their adjoining ribs on each side (forms domes of diaphragm)

Lumbar part

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34
Q

Actions of diaphragm

A

Principle muscle of respiration

Active part in coughing, forced defecation, weight lifting

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35
Q

Innervation of diaphragm

A

Phrenic nerve, C3, C4, C5

Keeps the diaphragm alive

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36
Q

3 major openings of the diaphragm

A

Vena cava aperture (level of T8)

Esophageal aperture (level of T10)

Aortic aperture (level of T12)

See figure

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37
Q

Changes in thoracic volume during inspiration

A

Inspiratory muscles contract

External intercostals elevate ribs

Diaphragm flattens

-> rib cage rises, increase in thoracic cavity in all of it’s dimensions (anterior-posterior and superior-inferior)

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38
Q

Changes in thoracic volume during expiration

A

Inspiratory muscles relax

External intercostals relax

Diaphragm rises

-> rib cage descends due to recall of costal cartilages, decrease in thoracic cavity volume

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39
Q

What do the arteries of the thoracic wall derive from?

A

Thoracic aorta -> posterior intercostal arteries

Subclavian artery -> internal thoracic -> anterior intercostal arteries

See figure

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40
Q

What are the intercostal veins? Branches?

A

Posterior intercostal -> azygous vein

Anterior intercostal -> internal thoracic vein

Both drain into superior vena cava

See figure

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41
Q

What are the veins of the thoracic wall?

A

Azygous vein (right)

Accessory Hemiazygous vein

Hemiazygous vein (drains into azygous)

See figure

42
Q

What do the veins of the thoracic wall drain into?

A

The superior vena cava

43
Q

How many pairs of spinal nerves does the thoracic wall have?

A

12 pairs of spinal nerves

44
Q

What types of innervation do the nerves of the thoracic wall provide?

A

Provide motor supply to muscles of thoracic and abdominal wall

Provide sensory supply to skin and costal parts of the diaphragm

Provide sympathetic innervation to the skin (e.g. sweat glands, blood vessels)

45
Q

What do the ventral rami of the thoracic spinal nerves supply?

A

The intercostal spaces of the thorax

46
Q

Which ventral rami form the intercostal nerves? Where do they run?

A

T1-T11

These nerves run along the extent of the intercostal spaces

See figure

47
Q

Where is the ventral rami of T12? What is it named?

A

Inferior to the 12th rib

Subcostal nerve

48
Q

Where do the dorsal rami of the spinal nerves run? What do they supply?

A

run posteriorly (clos to vertebrae)

supply bones, joints, muscles and skin of the back region of the thorax

49
Q

What is a dermatome?

A

An area of skin supplied by sensory neurons that arise from a spinal nerve ganglion.

Single nerve innervates single dermatome

50
Q

Which nerves innervate the dermatomes of the thoracic wall?

A

Sensory branches of intercostal nerves

51
Q

What is the content of the intercostal spaces?

A

Intercostal muscles (external, internal and innermost)

Blood vessels

Nerves

See figure

52
Q

How are intercostal spaces named?

A

Named after the rib superior to it

53
Q

What are the veins, arteries and nerves sandwiched between? where are they in relation to the rib?

A

The internal intercostal and the innermost intercostal

They are located in the costal groove

**order is vein, artery, nerve from superior to inferior

54
Q

Is there a 12th intercostal space:

A

No

55
Q

Inner linings of the thorax

A

Endothoracic fascia

Parietal pleura

See figure

56
Q

What is the end-thoracic fascia attached to?

A

Ribs and muscles

57
Q

What is the parietal pleura attached to?

A

Endothoracic fascia

58
Q

What is the pleura?

A

Serous epithelial layer with sub epithelial connective tissue

59
Q

What are the two parts of the pleura?

A

Visceral: attached to lung surface

Parietal: attached to the inner surface of the chest wall

These are separate cavities

Both are continuous at the root of the lung

60
Q

What is the pleural cavity?

A

A potential space lined by the visceral and parietal pleura

61
Q

What separates the visceral and parietal pleura?

A

A film of serous fluid

Reduces friction during breathing

62
Q

Different parts of the parietal pleura

A

Cervical part: near the cervical vertebrae

Costal part: related to the ribs and intercostal space

Diaphragmatic part: covers the diaphragm

Mediastinal part: covers mediastinum

See figure

63
Q

What are pleural recesses?

A

Potential spaces between the parietal and visceral pleura

64
Q

When do the lungs expand into the recesses?

A

Usually only during forced inspiration

65
Q

Clinical significance of recesses

A

provide potential spaces in which fluids can collect and from which fluids can be aspirated.

66
Q

Where are the costomediastinal recesses? Where is the largest one?

A

Occurs on each side where costal pleura is
opposed to mediastinal pleura.

The largest is on the left side in the region overlying the heart.

67
Q

Where are the costodiaphragmatic recesses?

A

Occur in each pleural cavity between the costal pleura and diaphragmatic pleura

68
Q

Which recesses are most clinically important?

A

Costodiaphragmatic

69
Q

Nerve innervation of the parietal pleura

A

Intercostal nerves: costal pleura

Phrenic nerve: mediastinal and diaphragmatic pleura

See figure

70
Q

Nerve innervation of the visceral pleura (lungs)

A

Autonomic innervation by PSNS and SNS fibres

71
Q

Does the parietal pleura have pain receptors?

A

No

72
Q

What are the three surfaces of the lungs?

A

Costal

Mediastinal

Diaphragmatic

73
Q

Anatomy of the costal surface of the lungs

A

Superior lobe

Middle lobe (right lung)

Inferior lobe

Oblique fissure

Horizontal fissure (right lung)

See figure

74
Q

Which structures does the right lung have that the left lung does not have?

A

Middle lobe

Horizontal fissure

75
Q

Impressions and grooves on the mediastinal surface of the lungs

A

Right: esophagus, azygous vein, right atrium

Left: Cardiac impression, aortic arch, left ventricle, lingula

Both have hilum and pulmonary ligament

See figure

76
Q

What is the only root/attachment to the lungs?

A

Hium

77
Q

What are the components of the hilum?

A

Pulmonary Artery (from pulmonary trunk)

Pulmonary Veins (drain into left atrium)

Bronchus

Autonomous nerves

Lymph nodes

Bronchial Arteries

Bronchial Veins

lymphatic vessels

78
Q

Where does aspiration of foreign bodies most likely occur?

A

Right bronchus

Straighter and shorter

79
Q

How many pulmonary veins per side enter the left atrium of the heart? How many pulmonary arteries exit?

A

2 pulmonary veins

One pulmonary artery

80
Q

Lymphatic drainage from lungs and bronchi

A

See figure

81
Q

Where do the lobes of the lungs drain?

A

The 3 lobes of the right lung and the lower lobe the left lung drain into the right lymphatic duct

The upper lobe of the left lung only drains into the left lymphatic (thoracic) duct.

82
Q

Where does the thoracic duct drain?

A

Into the left-jugular subclavian junction

83
Q

How does air enter the lungs during inspiration?

A

Muscles increase the thoracic space in all three of its dimensions

The parietal pleura is attached to the thoracic wall, forcing expansion of the lungs.

The pressure within the lungs drops below the atmospheric pressure outside, and the air passively rushes in (down the pressure gradient).

84
Q

How does air leave the lungs during expiration?

A

Muscles of respiration relax.

The air in the lungs is then forced to move out of the lungs because of the high elasticity and retractility of the lung tissue.

See figure

85
Q

What are the contours of the mediastinum?

A

Neck, arm

Left lung

Right lung

Abdomen

See figure

86
Q

What are the three parts of the mediastinum?

A

Posterior

Middle

Anterior

See figure

87
Q

What are the major organs of the mediastinum?

A

Thymus

Great vessels

Heart

Nerves

Trachea

Esophagus

Lymph vessels

88
Q

What are the branches of the aorta?

A

Coronary arteries

Brachiocephalic trunk

Left common carotid artery

Left subclavian artery

Posterior intercostal arteries

Bronchial arteries

Esophageal arteries

Superior phrenic arteries

89
Q

What are the branches of the aortic arch in ascending and descending order?

A

Ascending: Brachiocephalic (*), left common carotid (+), left subclavian (#)

See figure

90
Q

What is the origin of the phrenic nerve? What does it supply?

A

Origin: cervical plexus (C3-C5)

Motor: diaphragm

Sensory: pericardium, parietal pleura (mediastinal, diaphragmatic), parietal peritoneum (underside of diaphragm)

91
Q

What is the location of the phrenic nerve?

A

Ventral of anterior scalenus muscle

Descends anterior to the roots of the lungs

Between the fibrous pericardium and the mediastinal pleura

92
Q

What are the nerves of the mediastinum?

A

Vagus

Phrenic

Recurrent laryngeal

93
Q

Where does Vagus nerve run?

A

CN X

Runs posterior to root of lung

The right and left vagal trunks are adjacent to the esophagus

94
Q

What does the vagus nerve contribute to?

A

Cardiac, Esophageal and pulmonary autonomous nerve plexus

95
Q

Where does the recurrent laryngeal nerve branch from?

A

The vagus nerve

96
Q

What does the recurrent laryngeal nerve innervate?

A

Motor: most of the muscles of the larynx

Sensory: inferior larynx

97
Q

Course of the recurrent laryngeal nerve

A

Lateral to the trachea

98
Q

Clinical significance of the recurrent laryngeal nerve

A

Apical lung cancer may cause hoarseness resulting from invasion of the recurrent laryngeal nerve

99
Q

What provides sympathetic innervation of the mediastinum?

A

Sympathetic trunk (chain along the vertebral column)

Sphlanic nerves

100
Q

Where do the PSNS nerves in the mediastinum derive from?

A

Vagus nerve

101
Q

Function of SNS and PSNS nerves in the mediastinum

A

Pulmonary plexus

Esophageal plexus

Cardiac plexus

Anatomy (MPAS) (22 decks)

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