Thoracic Cavity 1 Flashcards
What do body cavities do?
Confine organs and systems that have related functions
– Allows movement, expansion,
contraction of organs
– Compartmentalize
– With miniscule layer of fluid; lubricated potential space; friction free
What lines body cavities?
Serous membranes
What lines the contents of the thoracic cavity?
Lungs and chest wall, lined by pleura; Heart covered by pericardium
What lines the content of the abdominal and pelvic cavities?
Abdominal and Pelvic cavities lined by the peritoneum
What is invagination?
Being folded inside out o form a cavity - The balloon punching effect
What are the two laters of the pleura of the lungs?
The visceral layer - facing viscera
The parietal layer - not facing viscera
Describe the divisions of the thoracic cavity
✓ The thoracic cavity is divided into three compartments
✓ The left and right pleural cavities are independent, with the mediastinum between them
✓ Pleura covers the lungs, reflects onto itself around the root of the lung and cover the diaphragm and the thoracic wall
What is parietal pleura attached to?
✓ Thorax wall (costal pleura)
✓ The fascia at the thoracic inlet, at 1st rib and T1
✓ Fibrous pericardium and other mediastinal structures (mediastinal pleura)
✓ Diaphragm (diaphragmatic pleura)
What are the divisions of the mediastinum?
✓ 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
✓ Inferior mediastinum is further subdivided into:
• Anterior mediastinum
• Middle mediastinum
• Posterior mediastinum
What structures are found on the right side of the mediastinum?
Structures on the right of the mediastinum are related to the right atrium and veins
- Superior Vena Cava
- Arch of the azygos
- Inferior Vena Cava
What structures are found on the left side of the mediastinum?
Structures on the left of the mediastinum are related to Left ventricle and arteries
- Left common carotid artery
- Left subclavian artery
- Arch of aorta
- Thoracic aorta
What is the pericardium?
✓ Fibro-serous sac that encloses the heart and the roots of the great vessels
✓ Functions:
– Anchoring the heart to surrounding tissues without compromising cardiac movement
– Preventing overfilling (overexpansion) of the heart
✓ Comprises two layers:
– Fibrous pericardium (externally)
– Serous pericardium (internally)
Describe the structure of the apex of the fibrous pericardium
The apex is fused with the adventitia of the great vessels
Describe the structure of the anterior aspect of the fibrous pericardium
Anteriorly, related and attached by the sterno-pericardial ligament to the body of the sternum, and 3rd- 6th costal cartilages
Describe the structure of the posterior aspect of the fibrous pericardium
Posteriorly, related and attached by the pericardiovertebral ligaments to 5th - 8th thoracic vertebrae
Describe the structure of the inferior aspect of the fibrous pericardium and what this do?
Inferiorly, blends with the central tendon of the diaphragm (Pericardiophrenic ligament)
Attachment of fibrous pericardium to diaphragm halts descent of the diaphragm during inspiration.
What are the two layers of the serous pericardium?
Parietal and visceral
Describe the two layers of the serous pericardium
✓ 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
Describe the pericardial cavity and its contents
✓ 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
Describe the embryological formation of the heart
During embryological development, the primordial heart tube folds and invaginates into the serous pericardium (within the fibrous sac)→2 sinuses are formed within the serous pericardium
What two sinuses are formed in the embryological development of the heart?
The transverse and oblique pericardial sinuses
Describe the 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
Describe the 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
What is the nerve supply of the pericardium?
✓ Sensory fibers from the phrenic nerve
✓ Vasomotor fibers from vagus nerve and the cardiopulmonary splanchnic nerves (sympathetic)
Describe the location of the phrenic nerve in the neck
✓ 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.)
Describe the location of the phrenic nerve in the thorax
✓Passes anterior to the root of lung
✓Lies between fibrous pericardium and parietal pleura
✓Right phrenic nerve passes through the Caval opening (thoracic diaphragm)
Describe the location of the right phrenic nerve in the thorax
✓Adjacent to superior vena cava, then inferior vena cava
✓Passes through the Caval opening
Describe the location of the left phrenic nerve in the thorax
✓Crosses the aortic arch
✓Over left ventricle
What does the phrenic nerve do?
✓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
Describe potential causes for 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?
Describe the boundaries of the anterior mediastinum
✓ Prevascular compartment ✓ Boundaries • Sternal body and xiphisternum • pericardium • lungs with pleura
What are the contents of the anterior mediastinum?
- Thymus (±) (Normally found in children - remnants in adults)
- Internal mammary vessels
- Lymph nodes (Terrible)
- Connective tissue
- Fat tissue
- Lower pole of Thyroid
- Ectopic parathyroid
What is the 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
Describe how the superior mediastinum is arranged?
✓Structures in the superior mediastinum are “arranged” in 3 planes
✓The vagus and phrenic nerves lie between these planes
What are the three planes in which structures in the superior mediastinum are arranged?
Venous plane
Arterial Plane
Visceral Plane
Describe the venous plane of the superior mediastinum
✓ The brachiocephalic veins (BCV) are formed by the Internal jugular (IJV) and subclavian (ScV) veins
✓ Left BCV passes anterior to the arch of the aorta; posterior to the manubrium
✓ Superior vena cava (SVC) is formed by right and left BCVs
✓ The arch of the azygos vein joins SVC
✓ SVC enters the right atrium
Describe the arterial plane of the superior mediastinum
✓ Ascending aorta with its braches (coronary arteries) are in the middle mediastinum
✓ Ascending aorta continues as the Aortic arch above the sternal angle - T4/5 plane
✓ Aortic arch curves up, backwards and slightly left behind the lower half of the manubrium
✓ Continues as the Thoracic (descending) aorta in the posterior mediastinum
Describe the arterial plane of the superior mediastinum in relation to the aortic arch
Aortic arch has 3 branches
1. Brachiocephalictrunk
• Divides into right subclavian and right common carotid arteries
2. Left common carotid artery
3. Left subclavian artery
• Posterior and to the left of the trachea
Describe the pulmonary arteries in the superior mediastinum
✓ The pulmonary trunk lies within the pericardium (hence middle mediastinum), to the left of the ascending aorta
✓ At the level of T4/5 disc, inferior to the Aortic arch, it divides into:
• Right pulmonary artery - Posterior to the ascending aorta and Superior vena cava
• Left pulmonary artery - Inferior to the arch of the aorta and anterior to the thoracic aorta
What is the trachea?
✓ Air-transport tube in midline of neck
✓ Starts at the level of C6 vertebra, ends at
tracheal bifurcation (carina)
− May rise and descend to the level of T4 and T6 with deep inspiration and expiration
What important structures can be found at the level of T3 in the superior mediastinum?
Brachiocephalic trunk
Right brachiocephalic trunk
Left common carotid artery
Where may pain in structures supplied by the phrenic nerve be referred to and why?
C4 Dermatome as ‘C3,4,5 keeps the diaphragm alive’ - C4 is the largest supplier of the phrenic nerve and so pain may be referred to its dermatome
This is from back of the neck to acromion process
What are the four Ts associated with pathology of the anterior mediastinum?
Thymoma
Lower pole of Thyroid tumour
Terrible Lymphoma
Teratoma
