The Thorax 2 Flashcards
What is the mediastinum?
What structures are found in the mediastinum?
The mediastinum is a broad median partition – actually a mass of tissues – medial to the lungs that extends from the sternum to the vertebral column – it includes all of the contents of the thoracic cavity except the lungs themselves – among the structures in the mediastinum are the heart, oesophagus, trachea, thymus gland, and many large blood and lymphatic vessels.
Label this image including the mediastinum
What are the 4 regions of the mediastinum?
- The superior mediastinum (manubriosternal junction to T4) – contains the arch of the aorta
- The anterior mediastinum
- The middle mediastinum – contains bifurcation of the trachea and the main bronchi
- The posterior mediastinum
Label this image with soft tissue anatomy and mediastinum regions
What does the superior mediastinum contain?
The arch of aorta
What does the middle mediastinum contain?
- Bifurcation of trachea
- Main bronchi
- Oseophagus
What does the anterior mediastinum contain?
Lymph vessels and nodes
What does the posterior mediastinum contain?
- Thoracic part of descending aorta
- Azygos & hemiazygos veins
- Vagus nerve
- Oesophagus
- Thoracic duct
- Lymph glands
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At what level do the main brochi commence?
Describe the structure of them?
Where does the left main bronchus pass?
- The right and left main bronchi commence at the bifurcation of the trachea, at the level of the upper border of T5
- The right main bronchus is wider, shorter and more ‘vertical’ than the left main bronchus – hence any foreign bodies that enter the respiratory system are more likely to lodge in the right pulmonary bronchus
- The left main bronchus passes behind the arch of the aorta and in front of the oesophagus and descending aorta
Explain the division of the bronchial tree?
- The bronchi within each lobe of the lung divide and subdivide to form smaller and smaller branches
- The main bronchi subdivide to form the secondary or lobar bronchi which supply each lobe of the lungs
- The secondary bronchi subdivide to form tertiary bronchi which then subdivide to form the terminal bronchioles
- This extensive branching is frequently referred to as the bronchial tree
- Superior / Upper and Inferior / Lower can be used interchangeably.
Label the lobes of the lungs
Label the x-ray with the lobes of the lungs
What are the lungs?
Separated by what?
•The lungs are paired cone-shaped organs lying in the thoracic cavity. – separated from each other by the heart and other structures in the mediastinum.
What are each lung divided into?
- The right lung is divided into superior, middle and inferior lobes
- The left lung is divided into superior and inferior lobes
- Each lobe is further divided into bronchopulmonary segments - Composed of many lobules. Each lobule is wrapped in elastic connective tissue.
Each lobule is composed of:
- A terminal bronchiole
- Alveoli
- Small branches of the pulmonary and bronchiole arteries
- Lymphatic vessels
- Nerves
Label the lung fissures
What is a fissure?
Explain the membranous layers of the lungs?
Fissures - Infolding of pleural membrane
Two layers of serous membrane (pleural membrane) enclose and protect each lung. The superficial layer lines the wall of the thoracic cavity and is called the parietal pleura. The deep layers, the visceral pleura, covers the lungs themselves.
•Between the visceral and parietal pleurae is a small potential space, the pleural cavity which contains a lubricating fluid secreted by the membranes. This fluid reduces friction between the membranes and allows them to slide easily on one another during breathing.
Expalin the fissure divisions of each lung?
Each lung is divided into lobes by one or more fissures, both lungs have an oblique fissure which extends inferiorly and anteriorly.
The right lung also has a horizontal fissure.
The oblique fissure separates the superior lobe from the inferior lobe. The superior part of the oblique fissure of the right lung separates the superior lobe from the inferior lobe, whereas the inferior part of the oblique fissure separates the inferior lobe from the middle lobe.
The horizontal fissure of the right lung subdivides the superior lobe thus forming a middle lobe.
What’s strange about this image
Point out the strange difference in this image
What is the azygos lobe?
What shape does it take and what level is it found?
What percentage of people does it appear in?
Why does it develop?
Azygos lobe- small accessory lobe sometimes found on the upper part of the right lung; separated from the rest of the upper lobe by a deep groove lodging the azygos vein, of little clinical significance.
-Appears starting in a tear drop shape at around T5 to the right of the midline as a pale line curving outward and upward and then back in to meet the root of the neck, the line is the infolding of the pleura.
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-Appears in about 1% of people.
It develops when the apical bronchus grows superiorly medial to the arch of the azygos vein instead of lateral to it. As a result the azygos vein comes to lie at the bottom of a deep fissure in the superior lobe of the right lung.
Label the heart
Explain the chambers of the heart?
- Heart is divided into 4 chambers
- Upper chambers = right & left atria
- Lower chambers = R & L ventricles
- Upper chambers = 1 functional unit
- Lower chambers = 1 functional unit
- R & L atria separated by interatrial septum
- R & L ventricles separated by the interventricular septum
- Great blood vessels separated from the atria by semi-lunar valves
- Atria & ventricles separated by the tricuspid valve on the right and the bicuspid valve on the left.
Describe the diffences in chamber wall thickness and why?
- The thickness of the muscle wall varies depending on pressure generated in each chamber
- The pressure is least in the atria so they have the thinnest walls
- The right ventricle has thicker walls as it must pump blood through the pulmonary circulation
- The left ventricle has the thickest wall as it must pump blood around the whole body
Label the heart valves
What do you see here?
How is the heart beat controlled?
Does anything else effect the rate of contraction?
By the sinoatrial node and the atrioventricular node
An inherent and rhytmical electrical activity is the reason for the hearts continuous beating.
Certain cardiac muscles repeatedly fire spontaneous action potentials (impulses) that trigger heart contractions. Signals from the autonomic nervous system and hormones etc modify the heart beat but they don’t establish the rhythm.
Explain the process of a heart beat?
Cardiac excitation begins in the SA node – each action potential (Ap) from the Sa node travels throughout both atria via gap junctions in the intercalated discs of atrial fibres. – in wake of the Ap, the atria contract
Cardiac ap also spreads from Sa node down the Av node – located in the septum between the two atria
From the av node, the ap enters the bundle of his – only electrical connection between the atria and the ventricles (elsewhere fibrous rings and sheets of connective tissue act as electrical insulation between the atria and ventricles.
After conducting along the av bundle – the ap then enters the right and left bundle branches that course through the interventricular septum toward the apex of the heart.
Finally large diameter conduction myofibers rapidly conduct the alp to the apex of the ventricular myocardium and upward to the remainder of the ventricular myocardium.
Pacemaker sets the rhythm for the entire heart. (normally Sa node)
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Explain the pathway of the left coronary artery?
The left coronary artery passes inferior to the left auricle and divides into the ant. ventricular and circumflex branches.
The anterior interventricular branch or left ant. descending artery is in the anterior interventricular sulcus and supplies oxygenated blood to the walls of both ventricles and the interventricular septum.
The circumflex branch lies in the coronary sulcus and distribues oxygenated blood to the walls of the left ventricle and left atrium.
Explain the pathway of the right coronary artery?
Right coronary artery supplies small branches to the right atrium.
Continues inf. to the right auricle and divides into the posterior interventricular and marginal branches.
The posterior interventricular branch follows the post. interventricular sulcus and supplies the walls of the two ventricles and the interventricular septum with oxygenated blood.
The marginal branch in the coronary sulcus transports oxygenated blood to the myocardium of the right ventricle.
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What imaging technique is this?
Angiogram
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How was this image taken?
What do the abbreviations stand for?
Contrast through the venous circulation system
