Theme 1: Lecture 1 - The Lungs and Pleura

Question 1

What are the cavities that the thoracic cavity is divided into?

Answer 1

Left pleural cavity - contains left lung

Right pleural cavity - contains right lung

Mediastinum - space between the 2 pleural cavities, contains trachea, heart, oesophagus, blood vessels and nerves

Question 2

From which germ layer does the lung bud develop?

Answer 2

Endoderm

Question 3

Pericardioperitoneal canal

Answer 3

The space between the parietal and visceral pleura that develops into the pleural cavity

Question 4

How do the lungs and pleura develop?

Answer 4

• The respiratory system begins to develop at 4-6 weeks from the endoderm layer
• Endodermal out pouches form lung buds and bronchial buds
• Rapid division of the airways occurs
• Hence the lungs push their way out into the primitive thoracic cavity. As they do they take the lining (visceral pleura) with them.

Question 5

Visceral pleura

Answer 5

• Closely adheres to the lungs including the fissures
• Creates a smooth and slippery surface
• Connects to the parietal pleura at the hilum (root of lung)

Question 6

Parietal pleura

Answer 6

Lines the internal aspect of the thoracic wall

Question 7

What are the parts that the parietal pleura are divided into?

Answer 7

• Costal (internal rib cage - outer edge)
• Mediastinal (lateral wall of mediastinum - inner edge)
• Diaphragmatic (superior diaphragm -bottom edge)
• Cervical (cervical region - top edge)

Question 8

Pleural cavity

Answer 8

-Space between the two layers of pleura
-Contains a thin layer of serous fluid
-Surface tension of the serous fluid holds lungs against thoracic wall
Lungs expand as thoracic cavity expands

Question 9

Pneumothorax

Answer 9

Air in the pleural cavity causing lung to collapse due to loss of surface tension between pleural layers

Question 10

Haemothorax

Answer 10

Blood in the pleural cavity, can cause surface tension between the pleural layers to be lost

Question 11

Pleural cavity recesses

Answer 11

• Areas where the visceral and parietal pleura aren’t touching
• These recesses can be occupied by the lung but only during forced inspiration
• They aren’t symmetrical because of the heart

Question 12

Costomediastinal recess

Answer 12

Found on the left hand side due to the heart sitting over to the left creating the cardiac notch

Question 13

Costodiaphragmatic recess

Answer 13

Area behind the dome of the diaphragm that the parietal pleural enters into, but no lung tissue enters into

Question 14

What is the parietal pleura innervation?

Answer 14

Cervical - 1st intercostal nerve
Costal - intercostal nerves
Mediastinal - phrenic nerve
Diaphragmatic - lower intercostals and phrenic nerves

Question 15

What is the visceral pleura innervation?

Answer 15

Autonomic (sympathetic and parasympathetic) from pulmonary plexus

Question 16

Features of the left lung

Answer 16

• 2 lobes
• Oblique fissure
• Impression for the heart (the cardiac notch)
• Lingua

Question 17

Features of the right lung

Answer 17

• 3 lobes

- Horizontal and oblique fissues

Question 18

What are the lobes of the left lung?

Answer 18

Superior and inferior

Question 19

What are the lobes of the right lung?

Answer 19

Superior, middle and inferior

Question 20

What are the surfaces of the lung?

Answer 20

Costal, mediastinal and diaphragmatic

Question 21

What are the borders of the lung?

Answer 21

Anterior (thinner), posterior (thicker) and inferior

Question 22

Hilum/Root of lungs

Answer 22

The area where everything that needs to travel to and from the lung passes into and out of the lung, it’s also the place where the viscera and parietal pleura meet

Question 23

Pulmonary ligament

Answer 23

Formed from parietal pleura and hangs inferiorly from the hilum of the lung. It allows the hilum to move up and down with lung movement

Question 24

What is the organisation of vessels in the hilum?

Answer 24

-Bronchi most posterior
-Arteries most superior
-Veins most inferior
(generally)

Question 25

Which arteries supply the lung and visceral pleura?

Answer 25

Bronchial arteries

Question 26

Where do the left bronchial arteries come from?

Answer 26

Branch from the descending aorta

Question 27

Where do the right bronchial arteries come from?

Answer 27

Branch from the intercostal arteries (the intercostal arteries have branched from the descending aorta and travelled in the intercostal groove)

Question 28

Where do the bronchial veins terminate?

Answer 28

The azygos system of veins

Question 29

What is the innervation of the lungs?

Answer 29

It comes from the ANS like all viscera

Sympathetic from the sympathetic trunk:

• Bronchial musculature dilates
• Pulmonary vasculature constricts

Parasympathetic from vagus:

• Bronchial musculature constricts
• Pulmonary vasculature dilates

Question 30

Through where does lymph drain?

Answer 30

Lymph drains towards the hilum via Bronchopulmonary (Hilar) nodes then Tracheobronchial nodes and then Paratracheal nodes

Question 31

Trachea

Answer 31

• Flexible tube, distal to larynx
• Runs from C6 to T4/5
• Anteriorly has C-shaped cartilage rings
• Posteriorly has trachealis muscle
• Bifurcates at level of sternal angle
• Lined by mucus membrane and cilia

Question 32

Carina

Answer 32

The piece of cartilage that separates the two main bronchi where the trachea bifurcates

Question 33

Primary bronchi

Answer 33

• One for each lung
• Passing through lung at hilum
• Right main bronchus is wider, shorter and runs more vertically
• Contains cartilage

Question 34

Secondary (lobar) bronchi

Answer 34

Supply one lung each, therefore there’s 3 in the right and 2 in the left

Question 35

Tertiary bronchi

Answer 35

Each supplies a bronchopulmonary segment

Question 36

Bronchopulmonary segments

Answer 36

There’s usually 10 in the right and 8-10 in the left

Each segment is:

• Supplied by a single tertiary bronchus
• Receives a single branch of the pulmonary artery
• Separated by connective tissue
• Surgically resectable (removable in isolation)

Question 37

Bronchioles

Answer 37

• 20-25 generations of conducting bronchioles
• No cartilage in walls
• Terminal bronchioles gives rise to several generations of respiratory bronchioles
• Respiratory bronchioles characterized by by out pockets of alveoli

Question 38

Alveoli

Answer 38

Alveolar ducts are elongated airways lined by alveoli which leads to common places called alveolar sacs. Each alveolus is surrounded by capillaries

Question 39

What are the alveoli cell types?

Answer 39

• Type 1 pneumocytes (95%)

- Type 2 pneumocytes (5%), these secrete pulmonary surfactant

Question 40

What is the purpose of pulmonary surfactant?

Answer 40

There is a thin film of fluid present in the alveoli, this could cause the alveoli to collapse due to the surface tension from that fluid. The pulmonary surfactant prevents the surface tension from collapsing the alveoli.