Thoracic Cavity Flashcards
What are body cavities lined with
serous membranes – Allows movement, expansion, contraction of organs – Compartmentalize – With miniscule layer of fluid; lubricated potential space; friction free
visceral layer
covers the organs
parietal layer
outer layer
what are the three compartments of the thoracic cavity
the left and right plural cavities and the mediastinum
where does the parietal pleura attach to
- thorax wall (costal pleura)
- the fascia at the thoracic inlet (first rib + T1)
- fibrous pericardium and other mediastinal structures (mediastinal pleura)
- diaphragm (diaphragmatic pleura)
mediastinum
✓Highly mobile region→volume and pressure changes
what are the two areas of the mediastinum
superior, inferior (anterior, middle and posterior)
superior mediastinum
behind manubrium, between the inlet and the plane through the sternal angle (and T4/5 disk)
Inferior Mediastinum
inferior to the transverse plane through the sternal angle and the diaphragm
structures to the right of the mediastinum
relate to the right atrium and veins:
- SVC
- Arch of the azygous
- IVC
structures to the left of the mediastinum
relate to the left ventricle and its arteries:
- left common carotid artery
- left subclavian artery
- arch of the aorta
- thoracic aorta
MIDDLE MEDIASTINUM
✓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
PERICARDIUM
✓ Fibro-serous sac that encloses the heart and the roots of the great vessels
✓ Comprises two layers:
– Fibrous pericardium (externally)
– Serous pericardium (internally)
function of the pericardium
✓ Functions:
– Anchoring the heart to surrounding tissues without compromising cardiac movement
– Preventing overfilling (overexpansion) of the heart
FIBROUS PERICARDIUM
✓ 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
SEROUS PERICARDIUM
✓ 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
PERICARDIAL CAVITY & FLUID
✓ 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
embryological development of the pericardium
the heart tube folds and invaginates into the serous pericardium (within the fibrous sac)→2 sinuses are formed within the serous pericardium
what are the two sinus formed in the pericardium
the transverse pericardial sinus and the oblique pericardial sinus
TRANSVERSE PERICARDIAL SINUS
✓ 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
OBLIQUE PERICARDIAL SINUS
✓ 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
nerve supply to the pericardium
✓ Sensory fibers from the phrenic nerve
✓ Vasomotor fibers from vagus nerve and the cardiopulmonary splanchnic nerves (sympathetic).
PHRENIC NERVE
✓ 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.)
location of the phrenic nerve
✓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
function of the phrenic nerve
✓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
phrenic nerve and referred pain
- 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
phrenic nerve injury
✓ 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?
ANTERIOR MEDIASTINUM
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
THYMUS
✓ 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
trachea
starts at level C6 and ends as tracheal bifurcation, can rise and descend to the level of T4 and T6 with inspiration and expiration
Posterior to the sternoclavicular joint
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
Posterior to 1st right CC
Formation of superior vena cava (SVC) by right and left BCVs
Posterior to 2nd right CC
Arch of the azygos vein joins SVC
Posterior to 3rd right CC:
SVC enters the right atrium
what makes up the posterior mediastinum
✓Vertebral bodies ✓Proximal (posterior) costal segments ✓Proximal segments of posterior intercostal vessels ✓Proximal segments of intercostal nerves ✓Sympathic chain with its ganglia
thoracic aorta
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
visceral branches of the thoracic aorta
✓ Oesophageal arteries ✓ Bronchial arteries → usually 2 on the left + 1 on the right ✓ Pericardial branches ✓ Mediastinal branches
role of the oesophagus
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
upper third of the oesophagus
striated muscle as swallowing is voluntary and rapid
middle third of the oesophagus
mixed striated and smooth
lower third of the oesophagus
smooth muscle
what type of cells line the oesophagus
stratified squamous epithelium
movement of the oesophagus in the posterior mediastinum
swings forwards and to the left and pierces the diaphragm at T10
what cause the four constrictions of the oesophagus
upper oesophageal sphincter
arch of the aorta
left main bronchus
diaphragm
where do the upper and middle thirds of the oesophagus drain
azygous, hemiazygous, acessory hemiazygous (systemic)
where does the lower third of the oesophagus drain to
left gastric vein (portal system)
however ANASTOMOSIS between middle and lower thirds via; porto-systemic or portocaval anastomosis
oesophagus nerve supply (thoracic part)
✓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
MEDIASTINAL LYMPH NODES
Superior and inferior tracheobronchial nodes
✓ Clustered around the trachea and oesophagus
✓ Receives the lymph from the lung→spread of lung tumour
the anterior mediastinal nodes
are around the brachiocephalic veins
The posterior mediastinal nodes
behind the heart and adjacent to the oesophagus
THORACIC DUCT
✓ 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)
