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ESA3 > Resp S2 - Anatomy & Lung Ventilation > Flashcards

Resp S2 - Anatomy & Lung Ventilation Flashcards

0
Q

What is the sternal angle?

A

Where the manubrium meets the body of the sternum, there is a change in angle which is useful for locating the level of the 2nd rib and the arch of the aorta

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1
Q

What does the sternum consist of?

A

Manubrium - articulates to 1st & 2nd costal cartilages
Body - articulates to 2nd to 7th costal cartilages
Xiphersternum - remains cartilaginous to adult life

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2
Q

Describe ribs and their articulation

A

There are 12 ribs, all of which articulate posteriorly to the vertebral column. Anteriorly, their joints are as follows:
1-7 are connected to the sternum via the costal cartilages
8-10 are connected to the costal cartilage above
11-12 are “floating ribs” which end free in the abdominal muscles

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3
Q

What are the intercostal muscles?

A

External intercostal muscles
Internal intercostal muscles
Innermost intercostal muscles

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4
Q

Describe the external intercostal muscles

A

Outermost layer. Run anteriorly and inferiorly to the rib below. “Bucket handle” type movement. Responsible for ~30% of chest expansion during quiet breathing.

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5
Q

Describe inner intercostal muscles

A

Run posteriorly and inferiorly to the rib below

Active during forced expiration

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6
Q

Describe innermost intercostal muscles

A

Similar to the inner intercostal muscles but less developed

Act with the inner intercostal muscles during forced expiration

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7
Q

Where does the intercostal neurovascular bundle run and why is this clinically relevant?

A

They run along the lower border of the ribs, in the intercostal grooves between the internal and the innermost intercostal muscles.
Clinically relevant when inserting a chest drain or doing a pleural aspiration because we want to avoid damaging neurovascular bundles

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8
Q

Describe the intercostal arteries

A

Supply the intercostal muscles, parietal pleura and overlying skin
Each intercostal space (except the last two) have anterior intercostal arteries which arise from the musculophrenic->internal thoracic-> subclavian arteries and anastomose with the posterior intercostal arteries. These arise from the aorta and superior intercostal artery->costo-cervical trunk-> subclavian artery

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9
Q

Describe the intercostal veins

A

Each intercostal space has two anterior and one posterior intercostal vein. The anterior drain into the internal thoracic->subclavian arteries. The posterior drain into the azygous vein on the right and the hemiazygous vein on the left into the IVC

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10
Q

Describe the intercostal nerves

A

From the anterior rami of the thoracic spinal nerves (T1-T12)
They supply the intercostal muscles, parietal pleura and overlying skin

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11
Q

Describe the diaphragm

A

A dome shaped muscle which divides the thoracic cavity from the abdominal cavity
The dome lies at ~5th rib, lower on the LHS
Consists of central tendon and peripheral muscular parts.
Responsible for 70% of chest expansion
Innervated by the phrenic nerve (C3, 4, 5)

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12
Q

What is the peripheral muscular part of the diaphragm comprised of?

A 
Sternal part (from xiphisternum)
Vertebral part (from arcuate ligament & crura)
Costal part (from 7-12th costal cartilages)
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13
Q

What are the arcuate ligaments?

A

Thickening of fascia over the muscles of the posterior abdominal wall

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14
Q

What are the crura?

A

Strong tendons attached to the anterolateral surfaces of the upper 3 vertebral bodies (2 on the left)

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15
Q

Where and for what structures are the openings in the diaphragm?

A

T8 - inferior vena cava
T10 - oesophagus
T12 - aorta

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16
Q

What makes up the thoracic cavity?

A

2 lateral pulmonary cavities

1 central compartment called the mediastinum

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17
Q

How is the mediastinum sub-divided?

A 
Divided into sub compartments:
Superior
Middle
Anterior
Posterior
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18
Q

Describe the pleura

A

Serous membrane consisting of a single layer of mesothelioma cells and a thin underlying layer of connective tissue
The parietal pleura lines the inside of each hemi thorax and is continuous at the hilum with the visceral pleura which lines the outside of the lung

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19
Q

Describe the pleural space

A

Space between the parietal and visceral layers of the pleura
Contains a small amount of pleural fluid to allow the layers to move against each other and to maintain surface tension so the lung is pulled with the ribs whilst breathing
Fluid produced by parietal surface and drains into parietal lymphatic vessels

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20
Q

What are the costodiaphragmatic recesses?

A

The pleural-lined gutters at the base of the diaphragms upward convexities

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21
Q

Describe the blood supply to the pleura

A

Parietal: intercostal and internal thoracic arteries and veins
Visceral: bronchial arteries and veins

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22
Q

Describe innervation of the pleura

A

Parietal: somatic, including pain fibres from the intercostal and phrenic nerves, as well as autonomic
Visceral: autonomic only

23
Q

Describe the trachea

A

Commences at the lower border of the cricoid cartilage and terminates by dividing into the right and left bronchi at the level of the sternal angle, called the carina.
18-22 U-shaped cartilages with trachealis muscle posteriorly where the cartilage is lacking
Lined with pseudostratified ciliated columnar epithelium

24
Q

Describe the bronchi

A

Right: shorter, wider and more vertical. 2.5cm long. Gives off first branch (the upper lobar branch) before the hilum
Left: 5cm long. Passes under the arch of the aorta, anterior to the descending aorta and oesophagus

25
Q

Briefly describe the bronchial tree

A

The primary bronchi divide into the lobar bronchi (one for each lobe of the lung)
These divide into segmental bronchi, one for each bronchopulmonary segment
Segmental bronchi divide into subsegmental bronchi -> terminal bronchioles -> respiratory bronchioles -> alveolar ducts -> alveoli

26
Q

What is a bronchopulmonary segment and why are they clinically relevant?

A

An area of lung supplied by a segmental bronchus and accompanying bronchial artery and segmental branches of the pulmonary artery and vein.
Important in surgery because they can be isolated and removed with little bleeding, air leakage or interference with other segments

27
Q

Describe a bronchoscopy

A

Can be used to visualise the inner trachea, carina, main bronchi, lobar bronchi and origins of the segmental bronchi
Used in diagnosis of bronchial carcinoma for histology sampling and visualisation

28
Q

Describe the arterial blood supply to the bronchial tree

A

Bronchial arteries arise from the aorta on the left and the 3rd intercostal artery on the right
Supply visceral pleura, connective tissue and bronchial tree from the carina to the respiratory bronchioles

29
Q

Describe the venous blood supply to the bronchial tree

A

Most blood drains into the pulmonary veins
Superficial bronchial veins drain visceral pleura & hilar region bronchi to the azygous vein (RHS) & the hemiazygous accessory vein (LHS)
Deep bronchial veins drain drain the rest of the bronchi to the pulmonary vein or directly into the left atrium

30
Q

Briefly describe lung divisions

A

Left: two lobes (upper and lower) which are separated by the oblique fissure
Right: three lobes (upper, middle and lower) which are separated by the oblique fissure (middle from lower) and the horizontal fissure (middle from upper)

31
Q

What is the hilar region of the lung?

A

Where almost everything enters and leaves the lung: air in bronchi, blood in bronchial and pulmonary arteries and veins, lymphatics and nerves

32
Q

Describe pulmonary artery

A

Divides into right and left pulmonary arteries which enter the lung with the main bronchi. These further subdivide with the bronchi to the alveolar level to supply the alveoli, NOT the bronchi
Some anastomoses with bronchial arteries at capillary and precapillary level which maintain blood supply after pulmonary embolism

33
Q

Describe the pulmonary veins

A

Tend to follow the inter segmental septa
Drain the alveoli
Leave at the hilum

34
Q

Describe nerve supply to the lung

A

Parasympathetic fibres from the vagus for bronchial smooth muscle (bronchoconstriction), vasodilation in the pulmonary artery and secremotor in mucous glands
Vagal afferent fibres for cough reflex and some subserving pain
Sympathetic efferents for bronchodilator and vasoconstrictor

35
Q

Describe pulmonary lymphatics

A

Sub pleural lymphatic plexus drains lung parenchyma and visceral pleura along the surface to the hilar lymph nodes
Deep bronchopulmonary plexus lies in the submucosa of the bronchi and peribronchial tissue and eventually drains to the hilar region too
Enlarged tracheobronchial nodes may cause widening of the carina

36
Q

What are the normal values for CO2 and O2 in alveolar gas?

A

CO2: 5.3 kPa
O2: 13.3 kPa

37
Q

What factors affect gas exchange?

A

Available exchange area
Resistance/distance to diffusion
Partial pressure gradient

38
Q

Discuss exchange area as a factor for gas exchange

A

Lungs contain many alveoli, which total ~80m^2 of exchange area, therefore area available is rarely a limiting factor for gas exchange

39
Q

Discuss diffusion distance as a factor for gas exchange

A

Gases must diffuse through: alveolar cell, interstitial fluid, capillary cell, plasma and a red blood cell membrane
However, overall this is less than 1 micron in distance

40
Q

Discuss resistance as a factor for gas exchange

A

The resistance is not the same for the two gases. CO2 diffuses 21x as fast as O2 because it is more soluble. Therefore anything affecting diffusion will only affect O2 because this is limiting

41
Q

Discuss partial pressure gradient as a factor for gas exchange

A

O2 and CO2 must be kept very close to their normal values. This occurs through a process called ventilation

42
Q

Describe ventilation

A

Fresh atmospheric air does not enter the alveoli: diffusion of gases occurs in terminal and respiratory bronchioles
This means that alveolar gases remain at a very constant level, so blood gases remain constant

43
Q

How can the movement of air during breathing be measured?

A

With spirometry

44
Q

Define “tidal volume”

A

A certain volume enters the lungs with each breath - the tidal volume

45
Q

Define inspiratory reserve volume

A

The difference between normal (tidal) breathing and maximal inhalation

46
Q

Define expiratory reserve volume

A

The different between normal ‘tidal’ breathing and maximal exhalation

47
Q

What is residual volume?

A

We cannot completely empty our lungs, so the remainder after we exhale as much as we can is known as the residual volume

48
Q

Define inspiratory capacity

A

From quiet respiration to maximum respiration

Aka inspiratory reserve + tidal volume

49
Q

Define functional inspiratory capacity

A

The volume of air in the lungs at the end of quiet respiration

50
Q

Define vital capacity

A

Inspiratory capacity + expiratory reserve
OR
Tidal volume + inspiratory reserve + expiratory reserve

51
Q

Define total lung volume

A

Vital capacity + reserve volume

52
Q

Describe anatomical dead space

A

The volume of the conducting airways is called dead space because the air in these parts of the lung at the end of inspiration isn’t available for gas exchange. This volume is usually ~150ml and can be measured by the nitrogen washout test

53
Q

Describe alveolar dead space

A

The volume of air contained by alveoli which do not take part in gas exchange for any reason (eg poor blood supply, damage due to accident or disease)

54
Q

Describe physiological dead space

A

Anatomical dead space + alveolar dead space

May be determined by measuring the pCO2 (or pO2) of expired and alveolar air

55
Q

Define the pulmonary ventilation rate

A

Comprised of two components: alveolar ventilation and dead space ventilation

56
Q

Define empyema

A

Pus in the pleural space

ESA3 (17 decks)

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