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Anatomy of the Thorax

Anatomy of the Thorax

LSS Year 1

Anil Chopra

Contents

1Thorax 1 Anatomy of the Chest Wall

7Thorax 2 Lungs, Pleura and Diaphragm

14Thorax 3 Superior Mediastinum and Great Vessels

23Thorax 4 Organisation of Nerves in the Thorax Mon 26th Feb 2007

33Thorax 5 Lymphatic System, Breasts and Breast Cancer

37Thorax 6 The Posterior Mediastinum

Thorax 1 Anatomy of the Chest WallAnil Chopra

1. Demonstrate the position of the pectoralis major on the chest wall.

Large Muscle that covers the anterior (front) aspect of the chest wall and has two heads.

2. Define the attachments of the pectoralis major.

Consists of the clavicular head (originates from the clavicle) and the sternocostal head (originates from the sternum and costal cartilages).

3. Outline the actions of the pectoralis major.

Contracts when pushing.

4. Name the space between adjacent ribs

Intercostal Spaces

5. Name and summarise the functions of the muscles which are found between ribs

Intercostal muscles. There are 3: External intercostal muscles articulates downward and laterally Internal intercostal muscles articulates perpendicular to external intercostals. Innermost intercostal muscles fairly trivial.

Their job is to move the ribs as well as stiffen the chest wall improving efficiency of breathing movements. Just below each rib in the Costal groove, starting from the top, there is the intercostal vein, artery and then the nerve (VAN).

6. Identify a rib and be able to determine which part of the rib is placed posteriorly and which anteriorly.Head of rib is on posterior, then neck and angle.

Costal cartilage is anterior.

7. Name the structures with which a rib articulates.

Posteriorly the ribs articulate with the thoracic vertebra. (T1-T12)

Anteriorly

Rib 1 has costal cartilage attached to manubrium.

Rib 2 has costal cartilage attached to the manubriosternal joint.

Ribs 3 6 have costal cartilage attached to body of sternum.

Rib 7 has costal cartilage attached to xiphisternal joint.

Ribs 8 10 have costal cartilage attached to that of above rib.

Ribs 11 & 12 do not join to anything.

All the joints between the costal cartilages and the sternum are smooth synovial joints.Ribs 1-7 are True ribsRibs 8-10 are False ribsRibs 11&12 are Floating ribs

8. Identify the clavicle and demonstrate how it is positioned in the body. Clavicle is also known as the collarbone and is found on the anterior side of the body, just superior to the first rib.

Medially, it articulates with the manubrium of the sternum (breast-bone) at the sternoclavicular joint. Laterally end it articulates with the acromion of the scapula (shoulder blade) at the acromioclavicular joint.9. Identify the scapula and demonstrate how it is positioned in the body.

Scapula is also known as the shoulder blade and is found on the posterior side of the body.

Together with the clavicle it makes up the pectoral girdle. The scapula connects the humerus (arm bone) with the clavicle (collar bone).10. Identify a thoracic vertebra. There are 12 thoracic vertebrae T1- T12.

Each corresponds to a rib. 11. Name the different parts of a thoracic vertebra.

12. Explain how ribs are related to the thoracic vertebrae. Each vertebra articulates using the inferior and superior facets (at the head of the rib) and also the articular part of the tubercle. The head of the rib articulates the superior demifacet (near the body of the vertebrae)

The articulate part of the tubercle articulates with a facet on the transverse process (the wing like projections)

The articulations between the thoracic vertebrae and the ribs are called vertebrocostal joints.

The vertebrae also attach to each other via the facets of the superior articular process.

13. Explain how vertebrae articulate with each other and how they support loads and absorb jolts. Vertebrae articulate with each other by thin intervertebral discs between them (which also limits movement)

The disk is made of cartilage. It is therefore a synovial joint.

Each disc has an outer fibrous ring consisting of fibrocatilage called annulus fibrosus and an inner soft, pulpy, highly elastic substance called the nucleus pulposus.

The discs form strong joints, permit various movements of the vertebral column and absorb vertical shock. Under compression, they flatten, broaden and bulge from their intervertebral spaces.

Thorax 2 Lungs, Pleura and Diaphragm

Anil Chopra

1. Name the contents of an intercostal space.

Intercostal space contains:

External intercostal muscles

Internal intercostal muscles

Innermost intercostal muscles

Intercostal Vein (in costal groove)

Intercostal Artery (in costal groove) Intercostal Nerve (in costal groove)

Collateral branches

2. Define the pleura.

The pleura is a layer of flattened cells supported by connective tissue that lines each pleural cavity and covers the exterior of the lungs.

3. Name the layers of the pleura.

Pleura consist of 2 layers:

Visceral Pleura: this covers the surface of the lungs and is the innermost layer.

Parietal Pleura: this lines the innermost surface of the chest wall and is in contact with the ribs and intercostal muscles. It is the outermost layer.

These 2 layers are separated by the pleural cavity which contains serous fluid produced by the cells in the pleura. This helps the lungs glide as they expand and collapse.

4. Define the extent of the lungs.

The lungs are conical in shape:

The apex (top) of the lungs reach as high as 3-4 cm above the first costal cartilage, in the base of the neck.

The base (bottom) of the lungs is concave and rests on the diaphragm.

5. Define the extent of the pleura.

The parietal pleura consists of 4 parts:

the part relating to the intercostal spaces is the costal part the part relating to the diaphragm is the diaphragmatic part the part covering the mediastinum is the mediastinal part the part lining the cervical extension of the cavity is the cervical pleuraIn the mediastinal part, there is a space which is made for the root or hilum of the lung.

The visceral pleura is continuous with the parietal pleura all the way around the lungs attached to the outside of them, including running into both opposed surfaces of the fissures.

Superiorly the pleural cavity projects 3-4cm above the first costal cartilage.

Anteriorly the pleural cavities approach one another in the upper part of the sternum. In the lower part the right side is closer to the midline than the left side because of the space made by the pericardium etc.

Inferiorly the pleura reflects onto the diaphragm.

On the left side the diaphragm separates the left lobe of the liver, the spleen and the stomach.

On the right side the diaphragm separates the right lobe of the liver.

During quiet breathing

The inferior margin of the lungs comes down to as far as about rib VI in the midclavicular line (middle of clavicle) rib VIII in the midaxillary line (runs down side of body) and reaches the vertebral column at TX.

The inferior margin of the pleural cavity comes down as far as rib VIII on the midclavicular line, rib X on the midaxillary line, and reaches the vertebral column at TXII.

The space between the two margins is the costodiaphragmatic recess.6. State how the right and left lungs are normally distinguishable.

The right lung:

Has 3 lobes, the inferior lobe, the superior lobe and the middle lobe.

Has 2 fissures, the oblique fissure, separating the inferior lobe from the superior and middle lobes; and the horizontal fissure separating the superior lobe from the middle lobe.

On its mediastinal surface in contact with the heart, inferior vena cava, superior vena cava, azygos vein oesophagus.

Is larger than the left lung.

The left lung:

Has only 2 lobes, the inferior lobe and the superior lobe.

Has 1 fissure, the oblique fissure, that separates the superior and inferior lobes.

On its mediastinal surface is in contact with the heart, aortic arch, thoracic aorta, and oesophagus. It contains a notch where the heart projects into the pleural cavity from the middle mediastinum.

7. Identify the structures present at the Hilum of the lung.

All the structures at the Hilum are enveloped in the pleura: Principal bronchus Pulmonary artery (carry deoxygenated blood from Right ventricle)

2 Pulmonary veins (carry oxygenated blood to left atrium)

Bronchial arteries and veins (carry oxygenated blood from aorta to lung tissue)

Pulmonary plexus of nerves (mainly autonomic)

Lymph vessels.

8. Explain the term pulmonary circulation.

Right atrium ( Pulmonary Artery ( Lung capillaries (Pulmonary Vein (Left Atrium.

Blood is oxygenated in the lungs.

Resistance is an eighth of the systemic circulation and blood pressure is only 25/10mmHg.

9. Demonstrate the landmarks of the chest wall on a living chest.

Between the medial ends of the clavicles is the jugular notch.

If you feel down from the jugular notch where the sternum changes direction slightly, this is the sternal angle. (this marks the top of the aortic arch, the tracheal bifurcation and the level of the 2nd costal cartilage.

In men the nipple lies in the 4th intercostal space (between 4th and 5th ribs)