UNIT 2: pleura/ mediastinum

Question 1

what is the pleural sac?

Answer 1

two continous membranes (pleurae) that enclose the lungs

Question 2

what are the two parts of the pleura?

Answer 2

visceral: pulmonary pleura = covers lung and surface
parietal: lines pulmonary cavities adhering to thoracic wall, mediastinum and diaphragm

Question 3

what is the pleural sleeve?

Answer 3

area of continuity between visceral and parietal pleura which encloses the root of the lung

Question 4

what ligament do the pleurae form inferior to the root of the lung?

Answer 4

pulmonary ligament - extends between lung and mediastinum

Question 5

what is the pleural cavity and what does it contain?

Answer 5

space between visceral and parietal pleura
- contains pleural fluid which lubricates surfaces allowing them to slide smoothly during respiration and also produce surface tension

Question 6

where is the endothoracic fascia found?

Answer 6

thin fibro-areolayer between internal thoracic cage and parietal pleura

Question 7

how is the parietal pleura split?

Answer 7

• costal (cervical)/ diaphragmatic/ mediastinal

Question 8

what are the abrupt turns in parietal pleura called?

Answer 8

lines of pleural reflection

• sternal line - between costal/ mediastinal
• costal line - between costal/ diaphragmatic (anterior)
• vertebral line- between costal/ diaphragmatic (posterior)

Question 9

what is the mediastinum and what does it contain?

Answer 9

central compartment of thoracic cavity

- contains all thoracic viscera & structures except lungs and pleura

Question 10

where does the mediastinum extend from?

Answer 10

superior thoracic aperture to diaphragm

sternum/ costal cartilages to bodies of thoracic vertebrae

Question 11

how does the mediastinum accommodate movement, volume and pressure changes in the thoracic cavity?

Answer 11

looseness of the connective tissue, elasticity of lungs and parietal pleura

Question 12

how is the mediastinum divided?

Answer 12

superior/ inferior: anterior/ middle/ posterior

Question 13

what are the boundaries of superior mediastinum?

Answer 13

anterior: manubrium
posterior: t1 to t4 (IV disc between t4/5)
superior: thoracic inlet
inferior: sternal angle - tranverse thoracic plane

Question 14

what are the contents of the superior mediastinum?

Answer 14

Brachiocephalic veins
Arch of aorta/branches
Thymus
Superior vena cava
Thoracic duct
Esophagus
Nerves (vagus/ phrenic/recurrent laryngeal)
Trachea

Question 15

what is the thymus and what is its role?

Answer 15

lymphoid organ in lower neck involved in immune system - producing T cells/ secreting thymosin

Question 16

what are the three parts of the thoracic aorta?

Answer 16

ascending
arch
descending

Question 17

what arteries branch off from these tree parts?

Answer 17

• ascending: coronary
• arch: brachiocephalic trunk (right subclavian/ common carotid), left common carotid, left subclavian
• posterior: posterior intercostal

Question 18

describe the passage of the subclavian artery

Answer 18

• passes over upper surface of 1st rib and passes behind anterior scalene muscle

Question 19

what arteries does the subclavian artery divide into before passing behind the scalenes

Answer 19

• thyro-cervical
• vertebral
• internal thoracic

Question 20

where does the internal thoracic artery travel and what does it supply?

Answer 20

• dome of pleura behind 1st costal cartilage and inside of chest wall lateral to sternum in front of the tranverse thoracic muscle
• supplies anterior chest wall - its distal continuation (superior epigastric artery) supplies upper anterior abdominal wall

Question 21

what veins form the superior vena cava?

Answer 21

union of right/left brachiocephalic veins (in turn consist of subclavian and internal jugular vein

Question 22

where does the superior vena cava enter the heart an what structures does it return blood from?

Answer 22

into pericardial sac into right atrium of heart

- returns blood from all structures superior to diaphragm apart from lungs/heart

Question 23

what does the phrenic nerve supply? where can it be found?

Answer 23

motor/sensory innervation of diaphragm (c3, c4, 5)

in front of anterior scalene muscle/ behind subclavian vein

Question 24

what does the vagus nerve supply and what is its branch?

Answer 24

parasympathetic supply of all organs in thorax and abdomen

- branches off into recurrent laryngeal nerve which innervates the larynx, contributes to cardiac plexus

Question 25

what does the right vagus nerve contribute to?

Answer 25

pulmonary plexus and esophageal plexus

Question 26

what are the intercostal nerves?

Answer 26

direct continuation of anterior rami of spinal nerves which give motor innervation to intercostal msucles and sensory innervation to chest wall - run into sympathetic trunk which runs alongside vertebral column from t1 to sacrum

Question 27

what does the middle mediastinum contain?

Answer 27

pericardium /heart- ascending aorta, pulmonary trunk, SVC, arch of azygos vein and main bronchi

Question 28

what are the borders of the anterior mediastinum? (A/P/L/S/I)

Answer 28

- anterior: body of sternum/ transverse thoracic muscles - posterior: pericardium - lateral: mediastinal pleura - superior: sternal angle (continuous with superior mediastinum) - tranverse thoracic plane - inferior: diaphragm

Question 29

what is the acronym to remember the contents of the anterior mediastinum?

Answer 29

``` Bill Loves Long Fat Sausages ```

Question 30

what are the contents of the anterior mediastinum?

Answer 30

- branches of the internal thoracic vessels - lymphatic vessels - lymph nodes - fat - sternopericardial ligaments

Question 31

what are the borders of the posterior mediastinum? (A/P/S/I/L)

Answer 31

- anterior: pericardium - posterior: T5-T12 - superior: tranverse thoracic plane - inferior: diaphragm - lateral: mediastinal pleura

Question 32

what are the contents of the posterior mediastinum?

Answer 32

``` Descending aorta Azygos and hemiazygos veins Thoracic duct Esophagus/ plexus Symphathetic trunk/ganglia ```

Question 33

what is the acronym for remembering the branches of the descending aorta

Answer 33

``` Betty Eats Margherita Pizza Placed In Side Salad ```

Question 34

what are the branches of the descending aorta?

Answer 34

``` bronchial esophageal mediastinal pericardial posterior intercostal subcostal superior phrenic arteries ```

Question 35

what do the mediastinal branches of the descending aorta supply?

Answer 35

lymph nodes and other tissues

Question 36

what region of the oesophagus do the esophageal branches supply?

Answer 36

middle third

Question 37

how many pairs of posterior intercostal arteries are there and where do they run?

Answer 37

9 pairs | 3rd to 11th intercostal spaces

Question 38

where do the superior phrenic arteries run and what do they join?

Answer 38

thoracic side of diaphragm - join with musculophrenic/ pericardiophrenic branches of internal thoracic artery

Question 39

where does the thoracic duct lie? origin/ termination

Answer 39

bodies of inferior seven thoracic vertebrae - originates from cisterna chyli and drains into the left venous angle (union between left internal thoracic/jugular vein)

Question 40

where does it receive lymph from and what structures does it drain?

Answer 40

- drains back/ thoraco-abdominal and mediastinal viscera - receives lymph from collecting trunks in intercostal spaces and nearer to termination from jugular/ subclavian and bronchomediastinal veins

Question 41

what three structures is the oesophagus compressed by?

Answer 41

- aortic arch - left main bronchus - diaphragm

Question 42

describe the passage of the oesophagus

Answer 42

- down from superior mediastinum to posterior deviating to left and passes through esophageal hiatus into the diaphragm at level of t10 anterior to aorta

Question 43

what is the sympathetic trunk a continuation of?

Answer 43

cervical and lumbar trunks

Question 44

where does the sympathetic trunk lie?

Answer 44

superior: heads of ribs mid thoracic: costovertebral joints inferior: sides of ribs

Question 45

what are the names of the nerves at the lower end of the sympathetic trunk? and what do they supply?

Answer 45

lower thoracic sphlanic nerves (greater,lesser, least) | - supply viscera inferior to diaphragm