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Anatomy of the thorax > The thoracic wall > Flashcards

The thoracic wall Flashcards

1
Q

Can the body be divided equally posteriorly and anteriorly

A

No

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2
Q

What do the terms proximal and distal apply to

A

The limbs
Proximal- towards body along a limb
Distal- away from body along a limb

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3
Q

What is meant by the thoracic wall

A

Skeletal components that surround the structures inside the chest.

12 thoracic vertebrae

12 pairs of ribs and costal cartilages

Sternum

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4
Q

Describe the thoracic wall

A

Posteriorly- 12 thoracic vertebrae and their intervening disks
Laterally- the wall is formed by the ribs (12 on each side) and three layers of flat muscles, which span the intercostal spaces between the adjacent ribs, move the ribs and provide support for the intercostal spaces
Anteriorly- the wall is made up of the sternum- which consists of the manubrium of the sternum, body of sternum and xiphoid process.

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5
Q

How many ribs are there

A

12 pairs
1-7 reach sternum (true)
Ribs 8-10 reach costal cartilage above (false)
11 and 12 lack anterior attachment (floating)

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6
Q

What do the ribs form articulations with

A

Articulations (= joints)
with vertebral column via head and tubercle
with costal cartilages

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7
Q

Describe the articulations of the ribs

A

All ribs articulate with the thoracic vertebrae posteriorly. Most ribs (2-9) have 3 articulations with the vertebral column.
The head of each rib articulates with the body of its own vertebra and with the body of the vertebra above.
As the ribs curve posteriorly, each rib also articulates with the transverse process of its vertebra.
Anteriorly, the costal cartillages of ribs 1-8 articulate with the sternum.
The costal cartillages of ribs 8-10 articulate with the costal cartillages above them.
Ribs 11 and 12 are floating as they do not articulate with other ribs, costal cartillages or the sternum. Their costal cartillages are only small, just covering their tips.

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8
Q

What does the skeletal framework of the thoracic wall provide

A

It provides extensive attachment sites for muscles of the neck, abdomen, back and upper limbs.
A number of these muscles attach to ribs and function as accessory respiratory muscles; some also stabilise the position of the first and last ribs.

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9
Q

Why do ribs have different shapes and sizes

A

Due to differences in their location.

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10
Q

Describe the basic structure of ribs

A

A typical rib consists of a curved shaft with anterior and posterior ends. The anterior end is continuous with its costal cartilage. The posterior end articulates with the vertebral column and is characterised by head, neck and tubercle.

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11
Q

Describe the structures of the rib.

A

Head- somewhat expanded and typically represents two articular surfaces separated by a crest. The smaller superior surface articulates with the inferior costal facet on the body of the vertebra above, the larger inferior facet- articulates with the superior costal facet of its own vertebra.
Neck- short, flat region that separates the head from the tubercle (posterior region of the rib)
Tubercle- projects posteriorly from the junction of the head with the shaft and consists of an articular and a nonarticular part:
articular- medial- has an oval facet for articulation with the corresponding facet on the transverse process of its associated vertebra
raised nonarticular part- roughened by ligament attachments.

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12
Q

Describe the shaft of the rib

A

The shaft is normally thin with internal and external surfaces.
The superior margin is smooth and rounded, whereas the inferior margin is sharp.
The shaft bends forwards at a site termed the angle.
It also has a gentle twist around its longitudinal axis so that the external surface of the anterior part of the shaft appears superior to the posterior part.
The inferior margin of the internal surface is marked by a distinct costal groove

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13
Q

Describe the distinct features of rib 1

A

Flat in horizontal plane
From its articulation with T1 it slopes inferiorly to its attachment to the manubrium. The head only articulates with the body of its own vertebra and so only has one articular surface.
The superior surface of the rib is characterised by a distinct tubercle, the scalene tubercle., which separates the two smooth grooves that cross the rib approximately midway along the shaft.
Anterior groove is due to the subclavian vein.
Posterior groove- subclavian artery.
The shaft is roughened by muscle and ligaments.

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14
Q

Describe rib 2

A

Flat but twice as long as rib 1

Articulates with the vertebral column in a way typical to most ribs.

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15
Q

Describe rib 10

A

The head of rib 10 has a single facet for articulation with its own vertebra.

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16
Q

Describes ribs 11 and 12

A

Articulate only with the bodies of their own vertebra and have no tubercles or necks. Both are short, have little curve and are pointed anteriorly.

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17
Q

What happens to the rib cage as you get towards the bottom

A

Gets wider

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18
Q

What are found at different vertebral levels

A

Different structures

Expected location and morphology- get smaller as they die.

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19
Q

Describe the manubrium of the sternum

A

The superior surface is expanded laterally and bears a distinct and palpable notch- the jugular notch, in the midline.
On either side, there are large oval fossae for articulations with the clavicle.
Immediately inferior to these fossae, on each lateral surface of the manubrium are facets for attachment to the first costal cartilage.
At the lower end of the lateral border is a demifacet for articulation with the upper half of the anterior end of the second costal cartilage.

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20
Q

Describe the body of the sternum

A

Flat
The lateral margins of the body have articular facets for costal cartillages.
Superiorly, each lateral margin has a demifacet for articulation with the inferior aspect of the costal cartilage.
inferior to this are 4 facets for articulation with large ribs (3-11).
The inferior end of the body is a demifacet for articulation with the upper demifacet of the seventh costal cartilage. The inferior end of the body is attached to the xiphoid process.

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21
Q

Describe the xiphoid process

A

Smallest part of the sternum
Variable shape (wide, thin, pointed, curved or perforated)
Begins as cartilage which becomes ossified in the adult.
On each side of the upper lateral margin is a demifacet for articulation with the inferior end of the seventh costal cartilage.

22
Q

Describe the superior thoracic aperture

A

Ring formed of:
1st thoracic vertebra (T1)
1st ribs
Manubrium

Contents of thoracic inlet:
Great vessels heading for neck and upper limb, oesophagus, trachea, nerves and lymphatics

23
Q

Describe the dimensions of the superior thoracic aperture

A

Consists of vertebral body of T1 posteriorly; the medial margin of rib 1 on each side and the manubrium anteriorly.
The superior margin of the manubrium is in approximately the same horizontal plane as the intervertebral disc between vertebrae T2 and T3.
the first ribs slope inferiorly from their posterior articulation with T1 to their anterior attachment of the manubrium. Consequently, the plane of the superior thoracic aperture is at an oblique angle, facing somewhat anteriorly.

24
Q

Where is most lung tissue and lung capacity for expansion found

A

Most lung tissue and most capacity for lung expansion is in the lower parts of the thorax

25
Q

Describe the diaphragm

A

The musculotendinous diaphragm seals the inferior thoracic aperture.
Muscle fibres of the diaphragm arise radially from the margins of the inferior thoracic aperture, and converge into a large central tendon.
Because of the oblique angle of the inferior thoracic aperture, the posterior attachment of the diaphragm is inferior to the anterior attachment.
Has a flat central tendon with muscle radiating to costal margin and vertebrae.

26
Q

Describe the actions of the diaphragm in breathing

A

The diaphragm is not flat, rather it balloons superiorly, on both sides, to form domes.
Right dome higher than the left- reaching as high as rib 5.
As diaphragm contracts- height of domes decreases- thoracic volume increases.
pulls costal margin up to increase transverse and antero-posterior diameters

27
Q

Describe the basic actions of the intercostals in breathing

A

Intercostals – have a secondary role – stiffen chest wall to improve efficiency of breathing movements
Ensures air only comes through the airways
if too stiff- difficulty breathing.

28
Q

What is the diaphragm attached peripherally to

A 
Xiphoid process
costal margin
end of ribs 11 and 12
lumbar spine
ligaments that span across structures of the abdominal wall.
29
Q

What converges from the peripheral attachments of the diaphragm

A

Muscle fibres converge to join the central tendon.
The pericardium is attached to the middle part of the central tendon.
In the medial saggital plane, the diaphragm slopes inferiorly from its anterior attachment to the xiphoid, approximately at vertebral level T8/9, to its posterior attachment to the median arcuate ligament, crossing anteriorly to the aorta at T12.

30
Q

Describe the pump handle movement of the ribs during breathing

A

As the anterior ends of ribs are inferior to the posterior ends, when the ribs are elevated, they move the sternum upwards and forwards. Also, the sternal angle may become less acute
When the ribs are depressed, the sternum moves downwards and inwards.
This pump handle movement- changes the dimensions of the thorax in the anteroposterior direction.

31
Q

Describe the bucket handle movement of the ribs during breathing

A

Middles of the shafts tend to be lower than the two ends. When the shafts are elevated, the middle of the shafts move laterally.
This bucket handle movement of the thorax increases its lateral dimensions.

32
Q

What causes elevation and depression of the ribs

A

Elevation- diaphragm contracts

Depression- diaphragm relaxes

33
Q

Describe the external intercostal muscle

A

downwards and laterally from lower border of rib above to rib below.
Replaced by anterior intercostal membrane at costo-chondral (rib-cartilage) junction
moves ribs superiorly during inspiration
extend from tubercles to each costal cartillage

34
Q

Describes the internal intercostal muscle

A

Superiorly attached to the lateral edge of the costal groove of the rib above.
Inferiorly attached to the superior margin of the rib below deep to the attachment of the related external intercostal muscle
attachments begin anteriorly at the sternum
run superiomedially
moves ribs inferiorly during expiration
Replaced by membrane posteriorly

35
Q

Describe the innermost intercostal muscles

A

Same orientation as the internal intercostals
Superiorly attached to the medial edge of the costal groove of the rib above
Inferiorly attached to the internal aspect of superior margin of the rib below.
Acts with the internal intercostals.

36
Q

Describe the intercostal muscles

A

arranged in layers at right angles for stiffening of the chest to improve the efficiency of breathing; all innervated by intercostal nerves (T1-T11)
External- most superficial
Internal- sandwiched between external and innermost
Innermost- deepest.

37
Q

Describe the intercostal spaces

A

exist between the ribs, with three layers of intercostal muscles and neurovascular bundles directly inferior/superior to the bone

38
Q

What may damage to the intercostal nerves cause

A

Loss of sensation and movement.

39
Q

Summarise the intercostal nerves

A

11 pairs T1-T11 (+ 1 subcostal – T12)
Mixed (= motor + sensory)
Supply the intercostal spaces
Lateral cutaneous branch - anterior and posterior
Anterior cutaneous branch - medial and lateral

40
Q

Which ramus is larger

A

The posterior

41
Q

Describe the innervation of the thorax (intercostal nerves)

A

Posterior rami of spinal nerves T1-T11 and lie in the intercostal spaces between ribs.
Subcostal nerve for T12- below rib 12.
A typical intercostal nerve passes laterally around the thoracic wall. the largest of the branches is the lateral cutaneous branch, which pierces the lateral thoracic wall and divide into the anterior and posterior branch which innervate the overlying skin.

The intercostal nerves end as anterior cutaneous branches, which emerge either parasternal (between adjacent costal cartillages) or lateral to the midline on the abdominal wall to supply the skin.

Small collateral branches can be found in the intercostal space running along the superior border of the lower rib.

42
Q

What do the intercostal nerves carry

A

Somatic motor innervation to the muscles to the thoracic wall (intercostal, subcostal and transversus thoracis muscles)
Somatic sensory innervation from the skin and parietal pleura
Postganglionic sympathetic fibres to the periphery.

43
Q

Which other regions to the intercostals innervate

A

Anterior ramus of T1 contributes to brachial plexus.
Lateral cutaneous branch of 2nd intercostal nerve contributes to cutaneous innervation of the upper arm
Lower intercostal nerves supply the muscles, skin and peritoneum of the abdominal wall.

44
Q

Describe the neurovascular bundles

A

Intercostal nerves and associated major arteries and veins lie in the costal groove along the inferior margin of the superior rib and pass in the plane between the inner two layers of muscles
in each space, the vein is the most superior structure; artery is inferior to the vein, nerve inferior to the artery and so is often not protected by the groove- nerve is most at risk
Small collateral branches of the nerves and vessels may be found superior to the inferior rib.

45
Q

What are the implications for putting a chest drain or needle through the thoracic wall

A

Keep away from inferior margin of superior rib
he safe area to insert a chest drain is at:
* Anterior border of latissimus dorsi.
* Lateral border of pectoralis major.
* Superior line to axial level of nipple.
* 5th intercostal space anterior to mid-axillary line.

46
Q

Describe the intercostal neurovascular bundles

A

Anastomoses – The joining of vessels supplying the same territory.

  • Each intercostal artery joins (anastomoses) with a major artery at each end of the intercostal space.
  • This means there are 2 routes for the blood to flow.
  • Nerves, however, only come from the spinal cord.
47
Q

Summarise the intercostal arterial supply

A

Consist of mainly anterior and posterior branches
pass around the wall between adjacent ribs in intercostal spaces
Originate from aorta and internal thoracic arteries- which in turn arise from the subclavian arteries in the root of the neck.
Form a basket-like pattern.

48
Q

Describe the posterior intercostal arteries

A

Originate from vessels associated with the posterior thoracic wall
Upper 2- derived from supreme intercostal artery which descends into the thorax as a branch of the costocervical trunk (posterior to the subclavian artery) in the neck.
Remaining 9- posterior surface of the thoracic aorta

49
Q

Describe the anterior intercostal arteries

A

Originate directly or indirectly as lateral branches from the internal thoracic arteries
Upper 6- lateral branches of the internal thoracic
Lower- musculophrenic artery

In each space, they usually have two branches (see neurovascular bundle)

50
Q

Where does the internal thoracic artery derive from

A

Subclavian artery
6th intercostal space:
branches into the :
superior epigastric- continues inferiorly to the anterior abdominal wall- anastomoses with vessels from groin
musculophrenic- passes along costal margin- goes through diaphgram- ends near last intercostal space

51
Q

What are the contents of the thoracic cavity

A

Filled laterally by the lungs - each lying in its pleural cavity

Space between the pleural cavities = mediastinum
Heart (lying in its pericardial sac)
Great vessels 
Oesophagus
Trachea 
Thymus
Thoracic duct and other major lymph trunks
Lymph nodes
Phrenic and vagus nerves
52
Q

Describe the importance of the pleural cavity

A

must remain intact for air to enter the lungs through the airways
ribs move out- lungs stay deflated
fluid leak- creates surface tension- as the lungs move out- the others move out.

Anatomy of the thorax (11 decks)

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