The Thorax 2

Question 1

What is the mediastinum?

What structures are found in the mediastinum?

Answer 1

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.

Question 2

Label this image including the mediastinum

Answer 2

Question 3

What are the 4 regions of the mediastinum?

Answer 3

1. The superior mediastinum (manubriosternal junction to T4) – contains the arch of the aorta
2. The anterior mediastinum
3. The middle mediastinum – contains bifurcation of the trachea and the main bronchi
4. The posterior mediastinum

Question 4

Label this image with soft tissue anatomy and mediastinum regions

Answer 4

Question 5

What does the superior mediastinum contain?

Answer 5

The arch of aorta

Question 6

What does the middle mediastinum contain?

Answer 6

• Bifurcation of trachea
• Main bronchi
• Oseophagus

Question 7

What does the anterior mediastinum contain?

Answer 7

Lymph vessels and nodes

Question 8

What does the posterior mediastinum contain?

Answer 8

1. Thoracic part of descending aorta
2. Azygos & hemiazygos veins
3. Vagus nerve
4. Oesophagus
5. Thoracic duct
6. Lymph glands

Question 9

Label this image

Answer 9

Question 10

Label this image

Answer 10

Question 11

Label this image

Answer 11

Question 12

Label this image

Answer 12

Question 13

Label this image

Answer 13

Question 14

Label this image

Answer 14

Question 15

At what level do the main brochi commence?

Describe the structure of them?

Where does the left main bronchus pass?

Answer 15

• 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

Question 16

Explain the division of the bronchial tree?

Answer 16

• 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.

Question 17

Label the lobes of the lungs

Answer 17

Question 18

Label the x-ray with the lobes of the lungs

Answer 18

Question 19

What are the lungs?

Separated by what?

Answer 19

•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.

Question 20

What are each lung divided into?

Answer 20

• 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

Question 21

Label the lung fissures

Answer 21

Question 22

What is a fissure?

Explain the membranous layers of the lungs?

Answer 22

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.

Question 23

Expalin the fissure divisions of each lung?

Answer 23

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.

Question 24

What’s strange about this image

Answer 24

Question 25

Point out the strange difference in this image

Answer 25

Question 26

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?

Answer 26

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. - -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.

Question 27

Label the heart

Answer 27

Question 28

Explain the chambers of the heart?

Answer 28

* 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**.

Question 29

Describe the diffences in chamber wall thickness and why?

Answer 29

* 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

Question 30

Label the heart valves

Answer 30

Question 31

What do you see here?

Answer 31

Question 32

How is the heart beat controlled? Does anything else effect the rate of contraction?

Answer 32

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.

Question 33

Explain the process of a heart beat?

Answer 33

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)

Question 34

Label this image

Answer 34

Question 35

Explain the pathway of the left coronary artery?

Answer 35

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.**

Question 36

Explain the pathway of the right coronary artery?

Answer 36

**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.**

Question 37

Label this image What imaging technique is this?

Answer 37

Angiogram

Question 38

Label this image

Answer 38

Question 39

How was this image taken? What do the abbreviations stand for?

Answer 39

Contrast through the venous circulation system