Lungs and Pleural Cavity

Where is the visceral pleura found?

Adherent to all external surfaces of the lungs. Continuous with parietal pleura (mediastinal surface) at the hilum of the lung.

Deep pulmonary plexus - what does it drain and what is its path?

Drains larger bronchioles and bronchi. Drain to pulmonary nodes > then same path as subpleural plexus.

What are the surface projections of the right and left lung for apex, MCL, MAL, and scapular line?

Apex - extends to level of neck of first rib. MCL - lung projects inferiorly to rib 6. MAL - lung projects inferiorly to rib 8. Scapular line - lung projects inferiorly to rib 10.

What is a pleural recess? Give two examples.

Areas of pleural cavity which the lungs do not completely occupy during quiet respiration - 2 layers of parietal pleura come into contact with each other. Costomediastinal - mediastinal pleura reflects to become costal pleura anteriorly. Costodiaphragmatic - costal pleura reflects to become diaphragmatic pleura inferiorly.

How is the cardiac notch of the left lung created?

At midsternal line the lung projects inferiorly to rib 4 and then turns inferolaterally at the MCL to rib 6. The sharp lateral turn creates the notch.

Where would one perform a pericardiocentesis?

Bare area of the heart - small part of pericardium in direct contact with the anterior thoracic wall.

Where does trachea originate and course? What type of cartilage and muscle is it composed of? What is the carina? Innervation? Vascular and lymphatic supply?

Begins at CV6 and runs through neck and superior mediastinum along midline > bifurcates into right and left primary bronchi at the transverse thoracic plane. Is composed of hyaline cartilage bars and filled in posteriorly with longitudinal smooth muscle known as trachealis. Carina is the last cartilage ring located at the bifurcation and projects into the lumen. Innervated by recurrent laryngeal nerves. Vascular supply by the bronchial and inferior thyroid vessels. Lymphatic supply to paratracheal lymph nodes.

Where is the pleural cavity and what does it contain?

Between the visceral and parietal pleura. Contains a minimal amount of serous fluid secreted by the pleura.

What is the smallest functional unit of the lung? How are these units separated?

Bronchopulmonary segment - area supplied by 1 tertiary bronchus and associated branch of pulmonary artery. Pulmonary veins run between the segments. The segments are separated by CT septa.

Bronchial veins - course and termination?

Course with the bronchial arteries and terminate in the azygos veins.

Superficial lymphatic system aka subpleural plexus - what does it drain and what is its path?

Drains visceral pleura and lung parenchyma. Drains to bronchopulmonary nodes > tracheobronchial nodes > bronchomediastinal trunk > thoracic duct on left and right lymphatic duct on the right.

Clinical correlation - how do pathologies such as bronchial carcinoma cause the carina to be distorted?

Due to spread of metastatic cancer cells into inferior tracheobronchial (carinal) lymph nodes.

To where does the cervical extension extend to and what is it reinforced by? How may this be implicated in wounds of the neck?

Extends superiorly into root of neck slightly superior to the neck of the first rib. Reinforced by Sibson's fascia/the suprapleural membrane. In neck wounds, the cervical extension may be punctured and result in a pneumothorax.

How is there drainage between the two lungs?

Left inferior lobe can drain to the right tracheobronchial nodes and vice versa.

Where is the parietal pleura found? What are its 4 surfaces?

Lines the internal surface of the thoracic wall. Costal surface, diaphragmatic surface, mediastinal surface, cervical extension.

Contents of the pulmonary cavities?

Lungs, pleura, and pleural cavity.

What is the tracheobronchial tree? What structures does it involve?

Multiple levels of airway branching from trachea to alveoli (18-22 divisions). Includes trachea, bronchi, and lungs.

What are the courses of the fissures? Where is the middle lobe of the right lung located?

Oblique fissures run to 4th rib posteriorly and to the 6th rib anteriorly. Horizontal fissure follows the course of the 4th rib. Thus middle lobe lies between the 4th and 6th ribs anteriorly.

Pulmonary arteries - where do they originate and course? What type of blood do they carry? What structures do they supply?

Originate from pulmonary trunk at the level of the sternal angle and then branch and course with the bronchial airways. Carry poorly oxygenated blood from right ventricle to lungs. Supply distal portions of the tracheobronchial tree (small bronchioles and alveoli) and the visceral pleura.

Bronchial arteries - where do they originate and course? What do they supply?

Originate from thoracic aorta - usually two on the left and one on the right. Course with the bronchial tree to supply the trachea and bronchii.

Explain parasympathetic innervation? Its function?

Preganglionic nerve cell bodies in the brainstem with processes traveling in the vagus nerve. In the thorax the vagus nerve gives off thoracic cardiac parasympathetic branches which contribute to the pulmonary and cardiac plexuses. Postganglionic nerve cell bodies are in the wall of the airways. Cause bronchoconstriction, vasodilation, and gland secretion.

Explain sympathetic preganglionic and postganglionic innervation? Function of sympathetic innervation?

Preganglionic nerve cell bodies located in T2-T6 spinal cord segments will nerve cell processes going to the sympathetic chain. Postganglionic bodies in cervical and thoracic sympathetic chain with nerve cell processes forming cardiac branches known as cardiopulmonary splanchnic nerves. Cause bronchodilation, vasoconstriction, and inhibit gland secretion. GVA fibers transmit acute pain.

Course of the primary bronchi? Branching of secondary bronchi?

Primary bronchi pass inferolaterally within the root of the lung > within lung give rise to secondary/lobar bronchi - 3 lobes on the right and 2 lobes on the left > secondary bronchi further branch into tertiary/bronchopulmonary segmental bronchi - 10 segments of the right and 8 segments of the left.

What structures pass through the root of the lung? What is their orientation in the root of the lung?

Pulmonary artery and veins, primary bronchi, bronchial arteries and veins (usually 1 on right and 2 on left), pulmonary plexus of nerves, lymphatic vessels and lymph nodes. Pulmonary artery usually most superior. Pulmonary veins inferior and anterior. Primary bronchi usually posterior. Nerves on posterior surface of bronchi.

What are the lymph nodes found at the lung?

Pulmonary nodes - within the substance of the lung. Bronchopulmonary (hilar) nodes - at hilum of lung. Superior and inferior tracheobronchial nodes - at tracheal bifurcation.

How does a pneumothorax occur? What is the treatment for it? What is a tension pneumothorax?

Puncture of the visceral or parietal pleura allows air to enter the pleural cavity. When pleural cavity is compromised, the natural elasticity of the lung causes it to collapse. Treatment is chest tube placement. Tension pneumothorax is caused by loss of integrity of the visceral or parietal pleura - air enters the pleural space and is unable to exit. Air continues to accumulate in pleural space and increases the intrathoracic pressure.

Compare/contrast right primary versus left primary bronchi?

Right bronchus is shorter and wider and more vertically oriented - foreign bodies more commonly get lodged in right bronchus.

What are the lobes and fissures of the right lung? The left lung? What additional features does the left lung have?

Right lung: 3 lobes - superior, middle, inferior. 2 fissures - oblique and horizontal. Left lung: 2 lobes - superior and inferior. 1 fissure - oblique. Left lung also has cardiac notch and lingula.

Pulmonary veins - where do they originate and course? What type of blood do they carry?

Superior and inferior veins that originate from capillary beds around alveoli and course intersegmentally. Return oxygenated blood to the left atrium.

What are the 3 surfaces of the lungs? What is the hilum?

Surfaces: costal, mediastinal, and diaphragmatic. Hilum - area where all structures enter and leave the lung - located on mediastinal surface.

What is a segmentectomy?

Surgical removal of a bronchopulmonary segment - diseases of the lung often localize to a segment(s), and these segments can be removed without altering the function of other segments.

Branching that occurs within the lung?

Tertiary bronchi branch 18-20 times > bronchioles give rise to alveolar ducts > alveolar ducts give rise to alveoli.

Describe the pleura and its composition? What does it do for the lungs? What does it secrete?

Thin serosal membranes that surround the lung (parietal and visceral layers). Composed of simple squamous epithelial cells and a thin layer of loose CT. It provides a smooth surface for the lungs to move on during respiration. Secretes serosal fluid which fills the pleural cavity (this fluid is the only thing in the pleural space).

Where does drainage from parietal pleura go?

To the thoracic wall - mainly that intercostal nodes but also the parasternal, diaphragmatic, and axillary nodes.

Summary: components of the airway conduction system/tracheobronchial tree?

Trachea, right and left primary bronchi, lobar bronchi, segmental bronchi.

Upper respiratory tract versus lower respiratory tract?

Upper - nose/paranasal cavities, pharynx, larynx. Lower -

What are the 3 lines of reflection?

Vertebral - costal surface becomes continuous with mediastinal surface posteriorly. Sternal - costal surface becomes continuous with mediastinal surface anteriorly. Costal - costal surface becomes continuous with diaphragmatic surface inferiorly.

How do nerves distribute to the lungs?

Via the anterior and primarily the posterior pulmonary plexuses located along the primary bronchi - these plexuses are a continuation of the deep cardiac plexus.

What forms the pulmonary ligament and what does this ligament do?

Visceral pleura and parietal pleura mediastinal surface form the pulmonary ligament which is an inferior extension of pleura that assists in lung fixation in the thoracic cavity.

Explain sensory innervation of visceral and parietal pleura? How is this implicated in pleuritis/pleurisy?

Visceral pleura sensory nerves travel with autonomic fibers. Parietal pleura receive sensory innervation from intercostal and phrenic nerves - if pleura membrane becomes inflamed pain may be referred to area of thoracic wall and shoulder innervated by phrenic nerve.