Thoracic Cavity

Question 1

What are body cavities lined with

Answer 1

serous membranes
– Allows movement, expansion,
contraction of organs
– Compartmentalize
– With miniscule layer of fluid; lubricated potential space; friction free

Question 2

visceral layer

Answer 2

covers the organs

Question 3

parietal layer

Answer 3

outer layer

Question 4

what are the three compartments of the thoracic cavity

Answer 4

the left and right plural cavities and the mediastinum

Question 5

where does the parietal pleura attach to

Answer 5

• thorax wall (costal pleura)
• the fascia at the thoracic inlet (first rib + T1)
• fibrous pericardium and other mediastinal structures (mediastinal pleura)
• diaphragm (diaphragmatic pleura)

Question 6

mediastinum

Answer 6

✓Highly mobile region→volume and pressure changes

Question 7

what are the two areas of the mediastinum

Answer 7

superior, inferior (anterior, middle and posterior)

Question 8

superior mediastinum

Answer 8

behind manubrium, between the inlet and the plane through the sternal angle (and T4/5 disk)

Question 9

Inferior Mediastinum

Answer 9

inferior to the transverse plane through the sternal angle and the diaphragm

Question 10

structures to the right of the mediastinum

Answer 10

relate to the right atrium and veins:

• SVC
• Arch of the azygous
• IVC

Question 11

structures to the left of the mediastinum

Answer 11

relate to the left ventricle and its arteries:

• left common carotid artery
• left subclavian artery
• arch of the aorta
• thoracic aorta

Question 12

MIDDLE MEDIASTINUM

Answer 12

✓Contains
− Heart
− Pericardium

• Origins of great vessels (aorta, pulmonary trunk), terminal parts of SVC and IVC

• Smaller vessels (pulmonary veins)
− Phrenic nerves
− Branches of Vagus

Question 13

PERICARDIUM

Answer 13

✓ Fibro-serous sac that encloses the heart and the roots of the great vessels

✓ Comprises two layers:
– Fibrous pericardium (externally)
– Serous pericardium (internally)

Question 14

function of the pericardium

Answer 14

✓ Functions:
– Anchoring the heart to surrounding tissues without compromising cardiac movement
– Preventing overfilling (overexpansion) of the heart

Question 15

FIBROUS PERICARDIUM

Answer 15

✓ The apex is fused with the adventitia of the great vessels
✓ Anteriorly, related and attached by the sterno-pericardial ligament to the body of the sternum, and 3rd- 6th costal cartilages
✓ Posteriorly, related and attached by the pericardiovertebral ligaments to 5th - 8th thoracic vertebrae
✓ Inferiorly, blends with the central tendon of the diaphragm (Pericardiophrenic ligament)
✓ Attachment of fibrous pericardium to diaphragm halts descent of the diaphragm during inspiration

Question 16

SEROUS PERICARDIUM

Answer 16

✓ Has two layers: Parietal and visceral
✓ Parietal layer:
− Lines the inner aspect of
the fibrous pericardium
– Reflects onto itself around the roots of the great vessels and continues as the visceral layer
✓ Visceral layer = epicardium

Question 17

PERICARDIAL CAVITY & FLUID

Answer 17

✓ Pericardial cavity:
− Between parietal and visceral layers of serous pericardium
✓ Pericardial fluid: − 10-15 mL
− Produced by serous pericardium
− Reduce friction during contraction of the heart

Question 18

embryological development of the pericardium

Answer 18

the heart tube folds and invaginates into the serous pericardium (within the fibrous sac)→2 sinuses are formed within the serous pericardium

Question 19

what are the two sinus formed in the pericardium

Answer 19

the transverse pericardial sinus and the oblique pericardial sinus

Question 20

TRANSVERSE PERICARDIAL SINUS

Answer 20

✓ Sinus of Theile
✓ Separates the arterial and venous ends of the heart tube

✓ Posterior to the ascending aorta and pulmonary trunk, anterior to the superior vena cava.
✓ Superior to the left atrium and the pulmonary veins

Question 21

OBLIQUE PERICARDIAL SINUS

Answer 21

✓ Haller’s cul-de-sac
✓ Surrounded by the reflection of the serous pericardium around the right and left pulmonary veins and the inferior vena cava

Question 22

nerve supply to the pericardium

Answer 22

✓ Sensory fibers from the phrenic nerve

✓ Vasomotor fibers from vagus nerve and the cardiopulmonary splanchnic nerves (sympathetic).

Question 23

PHRENIC NERVE

Answer 23

✓ A branch of the cervical plexus
✓ Arises from ventral rami of C3,4,5
✓ Over scalenus anterior muscle
✓Enters the mediastinum between the venous and the arterial planes (subclavian a. and subclavian v.)

Question 24

location of the phrenic nerve

Answer 24

✓Passes anterior to the root of lung
✓Lies between fibrous pericardium and parietal pleura
✓Right phrenic nerve passes through the Caval opening
✓Adjacent to superior vena cava, then inferior vena cava
✓Passes through the Caval opening
✓Crosses the aortic arch
✓Over left ventricle

Question 25

function of the phrenic nerve

Answer 25

``` ✓Sole motor supply to the diaphragm ✓Also supplies sensory fibres to ✓the mediastinal parietal pleura ✓peritoneum and pleura related to the central tendon of the diaphragm ✓parietal pericardium ```

Question 26

phrenic nerve and referred pain

Answer 26

* Referred pain? * Supraclavicular Nerves: C3-4 * Lateral supraclavicular nerve supplies skin over shoulder, which is the C4 dermatome * Therefore, structures with a sensory supply via the phrenic may refer pain to the back of neck, the supraclavicular region, shoulder tip

Question 27

phrenic nerve injury

Answer 27

✓ Division of the phrenic nerve in the neck ✓ What if there is no paralysis ? ✓ Radial incisions in the diaphragm from the costal margin to the oesophageal hiatus ✓ Cardiac surgery: instillation of saline slush for myocardial preservation ✓ Thoracic surgery ✓ Lung tumours ✓ Mediastinal tumours ✓ Polio ✓ Iatrogenic?

Question 28

ANTERIOR MEDIASTINUM

Answer 28

``` T4 T5 ✓ Prevascular compartment ✓ Boundaries • Sternal body and xiphisternum • pericardium • lungs with pleura ✓ Contents • Thymus (±) • Internal mammary vessels • Lymph nodes (Terrible) • Connective tissue • Fat tissue • Lower pole of Thyroid • Ectopic parathyroid ```

Question 29

THYMUS

Answer 29

✓ Bi-lobed organ of lymphoid tissue ✓ Between the manubrium, sternum and pericardium ✓ Related to Pericardium; Superior vena cava and aorta; Left and Right brachiocephalic veins; Pleura; Phrenic nerves; Trachea ✓ Extends from lower neck (jugular notch) to 4th costal cartilage (sometimes below aortic arch) ✓ Active in childhood until puberty ✓ Increasing fibro-fatty infiltration with age

Question 30

trachea

Answer 30

starts at level C6 and ends as tracheal bifurcation, can rise and descend to the level of T4 and T6 with inspiration and expiration

Question 31

Posterior to the sternoclavicular joint

Answer 31

Formation of the brachiocephalic veins (BCV) by the Internal jugular (IJV) and subclavian (ScV) veins; division of Brachiocephalic trunk to its branches on the right side

Question 32

Posterior to 1st right CC

Answer 32

Formation of superior vena cava (SVC) by right and left BCVs

Question 33

Posterior to 2nd right CC

Answer 33

Arch of the azygos vein joins SVC

Question 34

Posterior to 3rd right CC:

Answer 34

SVC enters the right atrium

Question 35

what makes up the posterior mediastinum

Answer 35

``` ✓Vertebral bodies ✓Proximal (posterior) costal segments ✓Proximal segments of posterior intercostal vessels ✓Proximal segments of intercostal nerves ✓Sympathic chain with its ganglia ```

Question 36

thoracic aorta

Answer 36

begins at the level of the sternal angle and runs till the aortic hiatus (T12) lies on the left of the thoracic vertebral bodies, but moves to the midline in the lower thorax

Question 37

visceral branches of the thoracic aorta

Answer 37

``` ✓ Oesophageal arteries ✓ Bronchial arteries → usually 2 on the left + 1 on the right ✓ Pericardial branches ✓ Mediastinal branches ```

Question 38

role of the oesophagus

Answer 38

transport food and fluid to the stomach ✓ Starts in the midline as the continuation of the pharynx at C6, inferior border of cricoid cartilage ✓ It descends between the trachea and the vertebral column ✓ Enters the thorax behind trachea, with the arch of the aorta to its left in the superior mediastinum

Question 39

upper third of the oesophagus

Answer 39

striated muscle as swallowing is voluntary and rapid

Question 40

middle third of the oesophagus

Answer 40

mixed striated and smooth

Question 41

lower third of the oesophagus

Answer 41

smooth muscle

Question 42

what type of cells line the oesophagus

Answer 42

stratified squamous epithelium

Question 43

movement of the oesophagus in the posterior mediastinum

Answer 43

swings forwards and to the left and pierces the diaphragm at T10

Question 44

what cause the four constrictions of the oesophagus

Answer 44

upper oesophageal sphincter arch of the aorta left main bronchus diaphragm

Question 45

where do the upper and middle thirds of the oesophagus drain

Answer 45

azygous, hemiazygous, acessory hemiazygous (systemic)

Question 46

where does the lower third of the oesophagus drain to

Answer 46

left gastric vein (portal system) however ANASTOMOSIS between middle and lower thirds via; porto-systemic or portocaval anastomosis

Question 47

oesophagus nerve supply (thoracic part)

Answer 47

✓Left vagus→Anterior vagal trunk ✓Right vagus→Posterior vagal trunk ✓ Fibres from the anterior and posterior vagal trunks, together with sympathetic fibres form the oesophageal plexus around the oesophagus

Question 48

MEDIASTINAL LYMPH NODES

Answer 48

Superior and inferior tracheobronchial nodes ✓ Clustered around the trachea and oesophagus ✓ Receives the lymph from the lung→spread of lung tumour

Question 49

the anterior mediastinal nodes

Answer 49

are around the brachiocephalic veins

Question 50

The posterior mediastinal nodes

Answer 50

behind the heart and adjacent to the oesophagus

Question 51

THORACIC DUCT

Answer 51

✓ Carries the lymph from much of the body (except thorax, upper limb and head and neck of the right side) ✓ It starts at the cisterna chyli ✓ Lies between the aorta and azygos vein in the posterior mediastinum − Pulsation of the Aorta promotes lymph flow ✓ At T4/5 crosses behind the oesophagus to ascend on its left side ✓ Chylothorax - fluid leak between lung and chest wall ✓ Arches over the apex of the left lung and pleura ✓ Opens into the left brachiocephalic vein at the junction of the left internal jugular and the left subclavian vein (Pirogoff’s angle)