Lecture 2 (Muscles of the thoracic wall: pleural cavities and lungs)

Thorax

The chest, includes the thoracic wall and the thoracic cavity, it also contains internal organs such as the heart and lungs, as well as the esophagus, trachea, and large blood vessels

Trunk

Composed of the thorax, abdomen, and pelvis

Thoracic Wall

Made up of multiple parts, the skeletal part, and the skin, fascia, adipose tissue, and the muscle

Role of thoracic wall

It protects the thoracic cavity and the structures within it

What are the components of the skeletal part of the thoracic wall?

The sternum, ribs, and thoracic vertebrae

What muscles are a part of the thoracic cage?

The intercostal muscles and the diaphragm

What are the types of intercostal muscles?

External intercostal muscles, internal intercostal muscles, and innermost intercostal muscles

What direction do the external intercostal muscles run?

They run from lateral to medial and superior to inferior

What direction do the internal intercostal muscles and innermost intercostal muscles run?

They run from lateral to medial and inferior to superior

Where is the external intercostal membrane located?

Located anteriorly on the thorax

Where is the internal intercostal membrane located?

Located posteriorly on the thorax

What is the intercostal bundle and where is it located?

The intercostal bundle is the vein, artery, and nerve that run between the internal and innermost intercostal muscles, they sit in the costal groove below each rib

Where do intercostal nerves orginate from?

From spinal nerves

Where do the anterior intercostal arteries branch from?

The internal thoracic artery

Where do the posterior intercostal arteries branch from?

The aorta

What accompanies the anterior and posterior intercostal arteries?

Anterior and posterior intercostal veins

Pleura

A serous membrane

Parietal pleura

A serous membrane covering the inner walls of the thoracic cavity

Visceral pleura

A serous membrane covering the surface of the lung

What are the regions parietal pleura is divided into?

Costal pleura, diaphragmatic pleura, mediastinal pleura, and cervical pleura

Costal pleura

Covers the ribs and intercostal muscles

Diaphragmatic pleura

Covers the diaphragm

Mediastinal pleura

Covers the mediastinal surface

Cervical pleura

Extends into the neck

Pleural cavities

Small, and lie between visceral and parietal pleura, containing a small amount of serous pleural fluid

Pleural fluid

Lubricates the surface of the lungs, allowing movement of the lungs against the parietal surfaces during inspiration and expiration

Pleural reflection

The point where parietal pleura changes its position from one area to another, such as from the diaphragm to the costal surfaces

What are the two types of pleural reflections?

Costodiaphragmatic and costomediastinal

Costodiaphragmatic Reflection

Where the costal and diaphragmatic pleurae meet

Costomediastinal Reflection

Where the costal and mediastinal pleurae meet

Pleural recesses

Parts of the pleural cavity into which the lungs can expand on full inspiration *only used in a deep breath*

Costodiaphragmatic Recesses

About 2 rib spaces deep and are usually only filled with lung tissue in a deep breath

Costomediastinal Recesses

Very small spaces

Pleural Effusion

Excess fluid that accumulates in the pleural cavity, it can impair breathing by limiting the expansion of the lungs

Pneumothorax

The accumulation of air in the pleural space, commonly called a collapsed lung

What are the lobes of the left lung?

Superior and inferior lobes (and a lingula, part of superior lobe)

What are the lobes of the right lung?

Superior lobe, middle lobe, and inferior lobe

In the right lung, what separates the superior and middle lobe?

The horizontal fissure

In the right lung, what separates the middle and inferior lobe

The oblique fissure

In the left lung, what separates the superior and inferior lobes?

The oblique fissure

Hilum

The area on the medial aspect of the lung where blood vessels and other structures comprising the root of the lung either enter or leave the lung

What structures enter in the root of the lung, located at the hilum?

Bronchus and pulmonary artery

What structures leave the root of the lung, at the hilum?

The pulmonary veins

At what level does the trachea bifurcate?

At the sternal angle

Why is the right bronchus bigger in diameter, more vertical, and shorter than the left bronchus? What are the implications of this?

The heart is on the left of the midline. Inhaled peanuts and other food or foreign bodies tend to end up on the right bronchus

Segments of the lungs

Each are a functional unit with its own tertiary bronchus, artery, and vein

What are the primary muscles of respiration?

Diaphragm and intercostal muscles

What is the role of the diaphragm during breathing?

It depresses when it contracts (during inspiration) and when it relaxes it elevates (during expiration)

Accessory Muscles of Inspiration

Scalene muscles, sternocleidomastoid (SCM), pectoralis major, pectoralis minor, transversus thoracis, and abdominal muscles

What nerve innervates the diaphragm?

The left and right phrenic nerves (they are mixed; sensory and motor) combines fibers from C3,C4,C5

What happens to the lower ribs(8-12) during inspiration?

They move laterally when elevated (bucket handle movement)

What happens to the upper ribs(1-7) during inspiration?

They move anteriorly when they are elevated (pump handle movement)