Download THORACIC CAVITY

THORACIC CAVITY
Learning objectives
At the end of lecture the student should be able to :
1. Describe the boundaries of mediastinum.
2. Describe the division of mediastinum in superior and inferior parts.
3. Describe the boundaries and contents of superior mediasinum.
4. Describe the further division of inferior mediastinum in anterior , middle and posterior
mediastina , their boundaries and contents .
Lecture outline
Thoracic cavity:
• Thoracic cavity is completely filled laterally by the lungs, each lying in its pleural cavity
• The space between the pleural cavities occupying the center of thoracic cavity is the
mediastinum
BOUNDARIES OF MEDIASTINUM
• Anteriorly
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sternum
Posteriorly
vertebral column
Superiorly:
thoracic inlet
Inferiorly
diaphragm
On each side:
lungs & pleura
DIVISION OF MEDIASTINUM
Mediastinum is divided into
• superior and
• inferior mediastinum by imaginary line passing anteriorly through sternal angle to the lower
border of body of fourth thoracic vertebra posteriorly.
INFERIOR MEDIASTINUM
• ANTERIOR MEDIASTINUM
Lies In front Of The Pericardium
• MIDDLE MEDIASTINUM
Contains Heart And Pericardium
• POSTERIOR MEDIASTINUM
Lies Behind The Pericardium
•
SUPERIOR MEDIASTINUM
BOUNDARIES;
• Anteriorly:
Manubrium Sterni
• Posteriorly:
Upper four thoracic vertebrae
• Superiorly:
Plane of the thoracic inlet
• Inferiorly:
An imaginary plane passing through sternal angle in front, and the lower border of
the body of the fourth thoracic vertebra behind
• On each side:
Medisatinal pleura
CONTENTS
• Tubes : trachea and esophagus.
• Muscles: origins of: (1) sternohyoid and (2) sternothyroid, and (3) lower ends of longus colli.
• Arteries: (1) arch of aorta (2) brachiocephalic artery,(3) left common carotid artery, and (4) left
subclavian artery
• Veins: (1) right and left brachiocephalic veins (2) upper half of the superior vena cava, and (3) left
superior intercostal vein.
• Nerves: (1) vagus (2) phrenic (3) cardiac verves of both sides and (4) left recurrent laryngeal
nerve.
• Thymus
• Thoracic duct
• Lymph nodes: paratracheal, brachiocephalic and tracheobronchial
INFERIOR MEDIASTINUM
The inferior mediastinum is divided into
• Anterior
• Middle and
• Posterior mediastina.
ANTERIOR MEDIASTINUM
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Anterior mediastinum is a very narrow space in front of the pericardium
Overlapped by the thin anterior border of both lungs.
It is continuous through the superior mediastinum with the pretracheal space of the neck.
BOUNDARIES
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Anteriorly: body of sternum
Posteriorly: pericardium
Superiorly: imaginary plane separating the superior mediastinum from the inferior mediastinum.
Inferiorly: superior surface of diaphragm.
On each side: Mediastinal pleura
CONTENTS
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Sternopericardial ligaments
Lymph nodes with lymphatics
Small Mediastinal branches of the internal thoracic artery.
The lowest part of the thymus, and
loose areolar tissue
MIDDLE MEDIASTINUM
• Middle mediastinum is occupied by the pericardium and its contents, along with the phrenic
nerves and the pericardiophrenic vessels.
CONTENTS
• Heart enclosed in pericardium
• Arteries: (1) ascending aorta
(2) pulmonary trunk
(3) two pulmonary arteries
• Veins: (1) lower half of the superior vena cava
(2) terminal part of the azygos vein
(3) right and left pulmonary veins
• Nerves: (1) phrenic
(2) deep cardiac plexus
• Lymph nodes: tracheobronchial nodes
• Tubes: (1) bifurcation of trachea
(2) the right and left principal bronchi
POSTERIOR MEDIASTINUM
BOUNDARIES
•
Anteriorly: (1) pericardium (2) bifurcation of trachea (3) pulmonary vessels, and (4) posterior part
of the upper surface of the diaphragm
•
Posteriorly: lower eight thoracic vertebrae and intervening discs.
•
On each side: mediastinum pleura
CONTENTS
• Oesophagus
• Arteries
descending thoracic aorta and its branches
• Veins:
(1) azygos vein
(2) homozygous vein
(3) accessory hemiazygos vein
• Nerves:
(1) vagi,
(2) splanchnic, nerves
• Lymph nodes
• Thoracic duct
JOINTS OF THORAX
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Manubrosternal joint
Interchondral joints
Costochondral joints
Costovertebral joints
Costotransverse joints
Intervertebral joints
1. Articulation of the Manubrium and Body of the Sternum
Manubrium is united to body of the sternum either by an
amphiarthrodial joint or by a diarthrodial joint
Sternocostal Articulations
 Articulations of cartilages of true ribs with sternum are
arthrodial joints.
 Except first, in which cartilage is directly united with sternum
called as synarthrodial articulation.
 The ligaments connecting them are:
1. The Articular Capsules
2.The Interarticular Sternocostal.
3.The Radiate Sternocostal.
4.The Costoxiphoid.
1.The Articular Capsules
 It surrounds joints between cartilages of true ribs
and sternum.
 Very thin, intimately blended with radiate Sternocostal ligament.
2. The Interarticular Sternocostal Ligament
 Found between second costal cartilages and sternum.
 Connects cartilage of second rib with sternum.
3. The Radiate Sternocostal Ligaments:
 Consists of broad and thin membranous bands.
 These radiate from front and back of sternal ends of cartilages of true ribs to
anterior and posterior surfaces of sternum.
4.The Costoxiphoid Ligaments:
 Connect anterior and posterior surfaces of seventh costal cartilage,
sometimes those of the sixth, to front and back of xiphoid process.
 Vary in length and breadth in different subjects
Synovial Membranes
 None between first costal cartilage and sternum.
 Two in articulation of second costal cartilage and generally one in each of
other joints.
 Disappear after middle life as articular surfaces lose their polish and become
roughened.
 In old age, cartilages of most of the ribs become continuous with sternum, and
joint cavities are consequently obliterated.
 Movements:
Slight gliding movements are permitted in the sternocostal articulations.
2. INTERCHONDRAL ARTICULATIONS
 Contiguous borders of sixth, seventh, eighth, sometimes ninth and tenth
costal cartilages articulate with each other by small, smooth, oblong facets.
Each articulation:
 Is enclosed in a thin articular capsule
 Lined by synovial membrane.
3.Costochondral Articulations:
 Lateral end of each costal cartilage is
received into a depression in the sternal end
of the rib.
 Two are held together by the periosteum.
4. COSTOVERTEBRAL ARTICULATIONS
Articulations of ribs with vertebral column may be divided into
two sets:
 One connecting heads of ribs with bodies of vertebrae.
 Another uniting necks and tubercles of ribs with transverse processes.
Articulations of the Heads of the Ribs:
 constitute a series of gliding or arthrodial joints.
 Formed by articulation of heads of typical ribs with facets on contiguous
margins of bodies of thoracic vertebrae and with Intervertebral fibrocartilages
between them.
 First, tenth, eleventh and twelfth ribs each articulate with a single vertebra.
The ligaments of the joints are:
1.The Articular Capsule.
2.The Radiate.
3.The Interarticular.
Synovial Membranes
 There are two in each of the articulations where
an interarticular ligament exists
 One above and one below this structure
 However, only one in those joints where there is
single cavity.
5. COSTOTRANSVERSE ARTICULATIONS
 Articular portion of tubercle of rib forms an arthrodial joint with articular
surface on adjacent transverse process.
 In the eleventh and twelfth ribs this articulation is
wanting.
The ligaments of the joint are:
1. The Articular Capsule.
2. The Posterior Costotransverse.
3. The Anterior Costotransverse.
4. The Ligament of the Neck of the Rib.
5. The Ligament of the Tubercle of the Rib.
6. INTERVERTEBRAL JOINTS
 Adjoining vertebrae are connected to each other
at three joints.
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 A median joint between the vertebral bodies
 Two joints right and left between the articular processes.
The joints between the articular processes are plane synovial joints
Between vertebral bodies are secondary cartilaginous verities.
Surfaces of vertebral bodies are lined by thin layers of hyaline cartilage.
Between these layers there is a thick plate of fibro-cartilage, called
intervertebral disc.