Thoracic Cavity - Rat (L4)

Question 1

Thoracic cavity

Answer 1

The chest. Opened by making incisions through the sides of the ribs.

Question 2

Diaphragm

Answer 2

Thin muscle anterior to the liver. Forms the caudal border of the thoracic cavity. Made of skeletal muscle fibers, divides the thoracic cavity from the abdominal cavity.

The contractions of the diaphragm create negative pressure in the thoracic cavity, this powers inflating the lungs.

Question 3

Lungs

Answer 3

The contractions of the diaphragm create negative pressure in the thoracic cavity, this powers inflating the lungs.

The lungs flank the heart. The right lung is divided into 3 lobes and the left is divided into two.

As the trachea approaches the lungs, it branches into 2 primary bronchi- one leading left, the other right. Further branching leads to progressively smaller tubes: secondary bronchi, bronchioles. Finally, respiratory bronchioles in the lungs terminate at the alveoli, where gas exchange takes place.

(Note that the lungs in this long-dead rat are collapsed.)

Question 4

Thymus

Answer 4

Wedge-shaped lymphoid organ that sits cranial to the heart and is attached to the trachea.

The site of T-cell maturation, and critical to the development of the immune system as a mammal matures.

After adolescence, slowly atrophies in adult humans due to increases in blood testosterone or estrogen.

Question 5

Trachea

Answer 5

From the pharynx and larynx, the trachea is the main air tube connecting to both lungs.

Stiffened with cartilaginous rings (made of hyaline cartilage) and lined with pseudociliated stratified columnar epithelium.

Branches into 2 primary bronchi as it approaches the lungs, one leads left, the other right.

Question 6

Why is the trachea stiff?

Answer 6

Stiffened with cartilaginous rings (made of hyaline cartilage).

Question 7

What cells is the trachea lined with?

Answer 7

Pseudostratified ciliated columnar epithelium.