Thorax Anatomy Flashcards
Describe the boundaries of the thorax.
- Cranially the thoracic inlet
- Dorsally the thoracic vertebrae
- Laterally the ribcage
- Ventrally the sternum
- Caudally the diaphragm
Describe the ribcage of a dog.
- 13 ribs, each one articulating with a thoracic vertebra.
- The dorsal 2/3 of each rib is bone, and the ventral 1/3 is cartilage, with the junction between the two tissues known as the costochondral junction.
- The first 9 ribs join the sternum ventrally, with the remainder joining one another to form the costal arch.
- The last rib is not connected ventrally - floating rib.
Describe the sternum in a dog.
- Made up of 8 little bones (sternebrae).
- First known as the manubrium
- Last is known as the xiphoid process, which has a cartilaginous extension (xiphoid cartilage).
What is contained within the thorax?
Heart, distal airways and lungs, thoracic oesophagus, thymus, blood vessels, nerves, lymph nodes and lymphatic vessels.
Describe the lobes of the left and right lungs in most domestic animals, and then the difference in a horse.
- Lung has two lobes; cranial and caudal with the cranial further divided into cranial and a caudal portion.
- Right lung has 4 lobes; cranial, middle, caudal and accessory.
- Horse lacks middle lobe.
Describe how pigs lungs look in comparison to other species.
- Less obvious divisions between lobes
- Surface appears marbled
- Rings of cartilage look like they overlap
How is a lung lobe determined?
Has a lobar bronchi (secondary bronchi)
What is the thorax lined with?
A serous membrane - the pleura.
What two parts make up the pleura?
Visceral and parietal
Describe the pleura in detail.
The visceral pleura invests the lungs and is reflected back at the root of the lung on to the organs in midline to form the mediastinal pleura, the diaphragm at the caudal extent of the thorax creating the diaphragmatic pleura and laterally on to the ribs to become the costal pleura. These last three constitute the
parietal pleura.
Describe the space between the pleura.
Visceral and parietal layers form a potential space, separated only by a few ml of serous fluid. This eliminates friction and facilitates negative pressure within the pleural space.
Describe the capsule of the heart in detail.
Invested by as serous membrane called the pericardium. Pericardium has visceral and parietal layers, separated by a few ml of serous fluid.
Describe the body of the heart.
Consists of an inner layer of endocardium, the muscular myocardium and the outer serosal epicardium which is confluent with the visceral pericardium.
How are the atrium and ventricles separated?
Muscular walls; interatrial/interventricular septum.
Describe the route of the blood through the heart.
- Right atrium receives deoxygenated blood from the body via the cranial and caudal vena cava.
- AV valve –> right ventricle –> pumps into the pulmonary artery through the pulmonic/semi-lunar valve.
- Left atrium receives deoxygenated blood via the pulmonary veins.
- Left ventricle pumps blood into the aorta via the aortic valve.
Compare the left and right ventricles.
Left is very muscular; right is thinner walled and weaker than the left, and wraps around the left ventricle.
What are the contraction and relaxation stages of the cardiac cycle know as?
Contraction - systole
Relaxation - diastole
Describe the position of the heart in the thorax of a dog.
- Located wiwithin the mediastinum; between the lungs.
- Extends approximately from the third to sixth intercostal space.
- Base directed dorsally and cranially, and the apex pointing caudally and slightly to the left.
Define the key features of the auricular and atrial view of the heart.
Auricular:
- Auricles and outflows are prominently visible
- Emphasises the cranial view of the heart from the front left aspect.
- Pulmonary trunk
- Aortic arch
- Left ventricle more prominent than right
Atrial:
- Highlights the atria and venous outflows
- Emphasises the caudal view of the heart from the back right aspect.
- Cranial and caudal vena cava; pulmonary veins
- Right ventricle more prominent than left
