BIO 290 (JMU Walker) Lab 3

What does the thoracic cavity contain?

two pleural cavities and a mediastinum surrounded by thoracic body wall muscles and the rib cage

What does each pleural cavity contain?

a lung

What is the mediastinum?

the subregion of the thorax located between the pleural cavities and contains the esophagus, trachea, and primary bronchi, pericardial cavity, the heart and its great vessels, phrenic and vagus nerves, and the descending thoracic aorta

What are the muscles of the thoracic body wall?

external intercostal mm, internal intercostal mm, innermost intercostal mm, and transverses thoracis mm

Are the muscles of the thoracic body wall epaxial or hypaxial?

hypaxial

Where do the muscles of the thoracic body wall develop?

they develop ventral to transverse processes and occur in three distinct layers

external intercostal muscles

origin/insertion: lower margin of superior rib to upper margin of inferior rib (obliquely downward, from vertebrae towards sternum)

Action: elevates ribs during inspiration; stabilizes thoracic wall

Innervation: intercostal nn. (thoracic ventral rami)

internal intercostal muscles and innermost intercostal

origin/insertion: lower margin of superior in to upper margin of inferior rib (obliquely downward from sternum towards vertebra)

Action: depresses ribs during expiration; stabilizes thoracic wall

innervation: intercostal nn. (thoracic ventral rami)

transversus thoracis muscles

origin: body and xiphoid process of sternum (internal surface)

Insertion: costal cartilages 2-6 (internal surface)

Action: depresses ribs during expiration

Innervation: intercostal nn. (thoracic ventral rami)

Where is the esophagus located in the mediastinum?

dorsal, lying on the anterior surface of the thoracic vertebral bodies

What is the esophagus?

a muscular tube (smooth muscle) that moves food from the pharynx to the stomach

Where does the trachea lie?

ventral to the esophagus

What is the trachea composed of?

C-shaped rings of cartilage joined one to another by intervening membranes of connective tissues, it is flexible but not collapsible

What happens to the trachea during inhalation?

the trachea stretches and descends

What happens to the trachea during exhalation?

it recoils to its original position

Where does the trachea divide into left and right bronchi?

At about T4 vertebral level

What are characteristics of the bronchi?

-run obliquely and then plunge into the hilus (medial depression) of each lung

-the right bronchus is wider, shorter and more vertical than the left bronchus

What are bronchial trees?

the bronchi branch profusely in the lungs

What are the blind sacs at the ends of the bronchial trees called?

alveoli