Gross Anatomy of the Lower Airways and Lungs

Question 1

Trachea anatomy

Answer 1

The trachea extends from the inferior border of the larynx at vertebral level C6/7 to bifurcation of trachea into right and left main bronchi at T4/5 (the level of the sternal angle). The trachea consist of many C-shaped cartilage rings with the trachealis muscle (smooth m) located posteriorly.

Question 2

Location of the trachea in the neck

Answer 2

The trachea is situated in the midline, partially covered anteriorly by infrahyoid (strap) muscles and isthmus of thyroid gland. Posterior to the trachea is the oeseophagus and vertebral bodies.

Question 3

Anatomic relationship between arch of aorta and trachea

Answer 3

The arch of aorta is located anterior and to the left of the trachea.

Question 4

Trachea bifurcation

Answer 4

The trachea bifurcates into the main (primary) bronchi at vertebral level T4/5.

Question 5

The difference between the right and left main bronchus.

Answer 5

The right main bronchus is more vertical and wider than the left main bronchus therefore aspirated objects are more likely to go into the right bronchus.

Question 6

The carina

Answer 6

A cartilaginous ridge located at the bifurcation of the trachea, slightly to the left of the midline. It is particularly sensitive to irritation producing a strong cough reflex.

Question 7

The thoracic cavity

Answer 7

Is divided into two pulmonary cavities (laterally) containing the lungs with the mediastinum, located centrally, containing the heart, great vessels, trachea, oeseophagus etc.

Question 8

The pleura

Answer 8

A continuous seorus membrane (simple squamous epithelium and underlying CT) covering the lungs (visceral pleura) and the thoracic wall, diaphragm and mediastinum (parietal pleura). The visceral and parietal pleura are continuous at the hilum of the lung.

Question 9

Pleural cavity

Answer 9

A potential space between visceral and parietal pleural layers containing a thin film of serous fluid. It surrounds lung but the lung is not ‘in’ it. The left and right pleural cavities are separate and not connected.

Question 10

Pleural effusion

Answer 10

Excess fluid in the pleural cavity

Question 11

Haemothorax

Answer 11

Blood in the pleural cavity

Question 12

Pneumothorax

Answer 12

Air in pleural cavity

Question 13

Parietal pleura

Answer 13

Is divided into:

• Cervical (superior)
• Costal
• Diaphragmatic; and
• Mediastinal

Question 14

Innervation of parietal pleura

Answer 14

The parietal pleura is innervated by pain fibres (but visceral pleura isn’t).

• Inercostal nn invervate the costal and peripheral diaphragmatic pleura
• Phrenic n (C3-5) innervates the mediastinal and central diaphragmatic pleura - pain referred ot neck, shoulder.

Question 15

Lines of pleural reflection and recess

Answer 15

Occur where the parietal pleura reflects from one surface to another.

• Costodiaphragmatic recess is located at the junction of teh costal and diaphragmatic pleura.
• Costomediastinal recess is located at the border of the mediastinal pleural and costal pleura.

Question 16

Lung borders and surfaces

Answer 16

The lung has three surfaces (costal, diaphragmatic, mediastinal) an apex and three borders (anterior, posterior, inferior).

Question 17

Hilum of lungs

Answer 17

Also known as the ‘root’ of the lung.

• Connects the lungs to the mediastinum.
• The parietal and visceral pleura are coninuous at the hilum.
• Contains pulmonary veins, pulmonary artery, bronchus, nerves, bronchia aa vv, lymphatic vessels and nodes.

Question 18

Right lung anatomy

Answer 18

The right lung has three lobes (upper, middle, lower) and two fissures oblique and horizontal.

The pulmonary a, vv and bronchus are located in the hilum with the pulmonary ligament extending inferiorly from the hilum.

Question 19

Left lung anatomy

Answer 19

The left lung has two lobes separated by an oblique fissure

• Upper: with lingual and cardiac notch
• Lower

Question 20

Lobar bronchi

Answer 20

The main (primary) bronchi divide into two secondary bronchi to upper and lower lobes on the left and three secondary bronchi to the upper, middle and lower lobes on the right.

Question 21

Segmental bronchi

Answer 21

Secondary bronchi divide into tertiary (segmental) bronchi which supply bronchopulmonary segments. Tertiary bronchi divide many times to eventually become bronchioles (lack cartilage).

Question 22

Bronchopulmonary segments

Answer 22

There are 10 segments on the right and 8 (or 10) on the left.

One segmental (tertiary) bronchus and one segmental pulmonary artery supply each bronchopulmonary segment. Each bronchopulmonary segment is pyramidal in shape with the apex towards the lung hilum and the base at the pleural surface, and each segment is separated by CT.

Question 23

Pulmonary circulation

Answer 23

• Right atrium
• Right ventricle
• Pulmonary trunk
• Pulmonary arteries
• Lobar arteries
• Segmental arteries…
• Arterioles
• Capillaries (gas exchange)
• Venules…
• Pulmonary veins
• Left atrium
• Left ventricle

Question 24

Bronchial arteries and veins

Answer 24

Bronchi and large bronchioles receive blood supply from the systemic circulation.

Bronchial aa arise from the aorta or posterior intercostal a.

Bronchial veins drain into the azygous system and pulmonary veins.

Question 25

Lymphatics of the lung.

Answer 25

Pulmonary (intrapulmonary) lymphatics have a diffuse distrivution, they drain into the hilar (bronchopulmonary) nodes –> carinal (inferior tracheobronchial) nodes –> superior tracheoronchial nodes –> tracheal (paratracheal) nodes –> bronchomediastinal lymph trunks to the right lymph duct or thoracic duct or directly into the brachiocephalic vein (R/L). May also drain to inferior deep cervical nodes.

The left lower lobe drains to carinal nodes, then predominanly across the midline to the right paratracheal nodes.

Question 26

Efferent innervation of lungs

Answer 26

Parasympathetic: vagus (CN X).

Preganglionic cell bodies are located in the medulla of the brainstem. Ganglia are intramural - within lungs, trachea.

Actions: bronchoconstriction, vasodilation, secretomotor to glands of bronchial tree.

Sympathetic

Preganglionics in T1-T5 spinal cord, synapse in sympathetic chain, postganglionic axons travel through pulmonary plexus located anterior and posterior to primary bronchi.

Actions: bronchodilator, vasocontrictor, inhibits gland of bronchial tree.

Question 27

Afferent innervation of lungs

Answer 27

Visceral afferents

• Stretch, irritants: travel with vagus n to brainstem (neuron cell bodies in inferior ganglion of vagus n), pressure receptors in pulmonary aa and chemoreceptors in pulmonary vv also travel via the vagus.
• Pain (nociceptive): travel with sympathetics to T1-T5 spinal cord, except via dorsal root (neuron cell bodies in dorsal root ganglia of T1-T5). The exception is the trachea which travels via the vagus.

Question 28

Surface anatomy apex

Answer 28

1-2 cm above medial 1/3 of clavicle

Question 29

Surface anatom of anterior border

Answer 29

Deep to sternum, except cardiac notch on left (ribs 4-6)

Question 30

Surface anatomy inferior border

Answer 30

Rib 6

Question 31

Surface anatomy lateral border

Answer 31

Mid axillary line, rib 8

Question 32

Surface anatomy posterior border

Answer 32

Rib 10

Question 33

Surface anatomy horizontal fissue

Answer 33

On the right side, is found anteriorly at the level of rib 4, and ends at the midaxillary line at the level of rib 5 when it meets the oblique fissure.

Question 34

Surface anatomy oblique fissure

Answer 34

Begins anteriorly at rib 6 at the midclavicular line, and travels upwards to rib 5 or 5th intercostal space at the midaxillary line.

Posteriorly the oblique fissure travels towards T4.

Also runs parallel to the vertebral border of scapula when teh arms are abducted.

Question 35

Surface anatomy of costomediastinal pleural reflection

Answer 35

Near the midline deep to sternum.

Question 36

Surface anatomy of costodiaphragmatic pleural reflection.

Answer 36

Midclavicular line - rib 8.

Midaxillary line - rib 10

Posteriorly - rib 12

Question 37

Level of lungs and pleura on quiet respiration

Answer 37

Lungs 6-8-10

Pleura 8-10-12