thorax topography

What does the costal arch connect?

It caudally connects the costal cartilages to the sternum.

At what level is the thoracic inlet?

The first rib.

Where do the ribs articulate with the thoracic vertebrae?

At the costal fovea.

How many thoracic vertebrae and rib/costal cartilage pairs do dogs have?

13

How many thoracic vertebrae and rib/costal cartilage pairs do cattle have?

13

How many thoracic vertebrae and rib/costal cartilage pairs do horses have?

18

What forms the ventral thoracic wall in dogs?

The sternum and costal cartilages.

How many sternebrae do dogs have?

8

How many sternebrae do horses have, and how do they differ from dogs?

8, the same as dogs, but horses have more costal cartilages because they have more ribs (18 pairs).

What forms the lateral thoracic wall?

The ribs and their associated muscles.

What forms the dorsal thoracic wall?

The vertebrae and their associated muscles.

What forms the ventral thoracic wall?

The sternum and costal cartilages.

What type of membrane is the pleura?

A serous membrane.

What does the pleura line or form?

It lines the thoracic wall, heart, and lungs, and it forms the mediastinum.

What is the pleural space?

A potential space containing a few milliliters of fluid.

What is the function of the pleural space fluid?

It keeps the lungs adhered to the thoracic wall.

What are the 2 main divisions of the pleura?

Parietal and visceral.

What are the 3 parts of the parietal pleura?

Costal, mediastinal, and diaphragmatic.

What does the visceral pleura cover?

The lungs.

What is the mediastinum?

The central compartment of the thorax that houses all the organs except the lungs.

What does “mediastinum” mean?

Middle, or partition.

What is the cupula pleura?

The small, dome-like cranial extent of the parietal pleura.

Where does the cupula pleura extend in large animals?

A few inches into the base of the neck, on the right side.

Why is the cupula pleura clinically important?

It’s susceptible to injury, which can cause a pneumothorax (collapsed lung).

What are the 3 divisions of the mediastinum?

Cranial, middle, and caudal.

What does the cranial mediastinum contain?

Trachea, esophagus, cranial vena cava, brachiocephalic trunk, lymph nodes, thymus, vagus nerve, and phrenic nerve.

What does the middle mediastinum contain?

The heart, root of the lungs, esophagus, lymph nodes, vagus nerve, and phrenic nerve.

What does the caudal mediastinum contain?

Aorta, azygous vein, esophagus, caudal vena cava, vagus nerve, phrenic nerve, and lymph nodes.

Which structures run through ALL 3 parts of the mediastinum?

The esophagus, vagus nerve, phrenic nerve, and lymph nodes.

Which mediastinal section contains the thymus?

The cranial mediastinum.

Which mediastinal section contains the heart?

The middle mediastinum.

Which mediastinal section contains the cranial vena cava and brachiocephalic trunk?

The cranial mediastinum.

Which mediastinal section contains the aorta, azygous vein, and caudal vena cava?

The caudal mediastinum.

Which mediastinal section contains the trachea?

The cranial mediastinum. In the middle mediastinum it becomes the root of the lungs.

What is the order of thoracic lymphatic drainage?

caudal mediastinal, middle mediastinal, cranial mediastinal, thoracic duct

Horse: where do you auscultate the mitral (left AV) valve?

Low in the left 5th intercostal space.

Horse: where do you auscultate the aortic valve?

High in the left 4th intercostal space.

Horse: where do you auscultate the pulmonic valve?

Low in the left 3rd intercostal space.

Horse: where do you auscultate the tricuspid (right AV) valve?

Low in the right 4th intercostal space.

Cow: where do you auscultate the mitral (left AV) valve?

Low in the left 4th intercostal space.

Cow: where do you auscultate the aortic valve?

High in the left 4th intercostal space.

Cow: where do you auscultate the pulmonic valve?

Low in the left 3rd intercostal space.

Cow: where do you auscultate the tricuspid (right AV) valve?

Low in the right 3rd or 4th intercostal space.

Dog: where do you auscultate the mitral (left AV) valve?

Low in the left 5th intercostal space.

Dog: where do you auscultate the aortic valve?

High in the left 4th intercostal space.

Dog: where do you auscultate the pulmonic valve?

Low in the left 3rd intercostal space.

Dog: where do you auscultate the tricuspid (right AV) valve?

Low in the right 4th intercostal space.

Which valve is auscultated HIGH, and which are LOW?

The aortic valve is high. The pulmonic, mitral, and tricuspid valves are low.

How does the cow’s mitral valve location differ from the horse and dog?

In the cow it’s in the left 4th ICS. In the horse and dog it’s in the left 5th ICS.

How does the cow’s tricuspid location differ from the horse and dog?

In the cow it’s the right 3rd or 4th ICS. In the horse and dog it’s the right 4th ICS.

Which valve location is the same in all 3 species?

The aortic valve (high, left 4th ICS) and the pulmonic valve (low, left 3rd ICS).