anatomy of lungs and pleura

Cavities

Thoracic cavity sub divisions

-Medially= mediastinum

-Laterally= pleural cavities

a= parietal pleura

b= visceral pleura

c= pleural cavity

Histology of Pleura

Simple squamous epithelium

 Subserous fascia (loose areolar CT)

which part of the pleura is pain sensitive

parietal pleura

parietal pleura divisions

 Cervical: Covers the apex of the lung in the neck region

 Costal: Lines ribs and intercostal surfaces

 Diaphragmatic: Lines thoracic surface of diaphragm

 Mediastinal: Lines the mediastinum

phrenic nerve innervates

Mediastinal and central part of diaphragmatic pleura

Intercostal nerves innervates

Costal and peripheral part of diaphragmatic pleura

what is pleurisy

a condition where the pleura—the thin, double-layered membrane that surrounds the lungs and lines the chest cavity—becomes inflamed. This inflammation causes sharp chest pain, especially when breathing, coughing, or sneezing.

ignore

 Costal pleura: Local dermatomal pain through intercostal nerves

 Mediastinal pleura: Referred pain through phrenic nerve (C3-5)

-Diaphragmatic pleura (central):

Costal pleura pain

• Innervation: Intercostal nerves

• Pain pattern: Sharp, localized dermatomal pain along the chest wall

Mediastinal pleura pain

• Innervation: Phrenic nerve (C3–C5)

• Pain pattern: Referred to shoulder and neck

central Diaphragmatic pleura

Phrenic nerve (C3–C5) → referred pain to the shoulder and neck

peripheral diaphragmatic pain

Intercostal nerves → localized pain

what are Pleural Recesses

Potential spaces for lung expansion during forced inspiration and fluid collection and spaces from which fluid can be aspirated

what are the 2 pleural recesses

Costodiaphragmatic recesses: Found between costal and diaphragmatic pleura

Costomediastinal recess: Located between costal and mediastinal pleura (large on the left side)

pleural effusion

pneumothorax

Pleural Effusion

A pleural effusion is the accumulation of excess fluid in the pleural space, the area between the visceral and parietal pleura.

pneumothorax

A pneumothorax is the presence of air in the pleural space, causing partial or complete lung collapse.

tension pneumothorax

A tension pneumothorax occurs when air enters the pleural space during inspiration but cannot escape during expiration, leading to progressive pressure build-up.

This pressure compresses the lung, shifts the mediastinum, and obstructs venous return to the heart → can lead to cardiac arrest if untreated.

Thoracentesis

Safe triangle for needle in lung

Anterior

Lateral border of the pectoralis major

Posterior

Lateral border of the latissimus dorsi

Inferior

Line at the level of the nipple (5th intercostal space)

Superior

Base of the axilla (apex of triangle)

trachea position

Fibrocartilaginous tube from C6 to T4/T5

 In deep inspiration, reaches the level of T6

Anterolateral of trachea

U-shaped bars of hyaline cartilage

posterior part of trachea

Smooth muscle (trachealis)

Carina

Right vs left primary bronchi

 Right bronchus: Wider, shorter and more vertical

 Left bronchus: Narrower, longer and more horizontal

Secondary bronchi right vs left

 Right: Superior, middle and inferior

 Left: Superior and inferior

right lung lobes and fissures

3 lobes

2 fissures: oblique and horizontal

left lung lobes and fissures

2 lobes

1 oblique fissure

hilum and root of lung structures

horizontal fissure location

Follows curvature of 4th rib (only in right lung)

oblique fissure location

From 5th intercostal space at the midclavicular line (MCL) → curves along the 6th rib anteriorly toward the midaxillary line and posteriorly

Right Lung lobe location

• Superior lobe: Located above the 4th rib, anteriorly

• Middle lobe: Lies between the 4th and 6th ribs, anteriorly

• Inferior lobe: Lies below the 6th rib, posteriorly

Posteriorly, both lungs are mostly inferior lobes—important when auscultating for basal pneumonia or effusions.

Bronchopulmonary Segment

 Segment of the lung supplied by a tertiary bronchus

Respiratory bronchioles:

Lead to individual pulmonary lobule

Branch as alveolar ducts to alveolar sacs, alveoli

Branches of pulmonary arteries and pulmonary veins form capillary bedsaround alveoli for gas exchange

Elastic fibressurround alveoli, assist in expiration

Type I pneumocytes

form a simple squamous epithelium

Type II pneumocytes

secrete surfactant decrease surface tension, maintains alveolar patency

stem cells for regeneration

Alveolar macrophages

phagocytose pathogens

Pulmonary Circulation

 Pulmonary trunk divides into R and L pulmonary arteries, carry deoxygenated blood to alveoli Arteriole

Pulmonary veins (four) drain oxygenated blood from alveoli

Bronchial arteries

branches of thoracic aorta supply lung parenchyma, pleura and alveoli

bronchial veins

Drain into the azygous system

Parasympathetic Supply of lungs

Vagus nerve (CN X)

Parasympathetic action

• Bronchoconstriction 🫁

• Vasodilation (pulmonary vessels)

• Increased mucus secretion

Sympathetic Supply

Sympathetic trunk (T1–T5 spinal levels)

sympathetic effects

• Bronchodilation 🫁

• Vasoconstriction

• Decreased glandular secretion

Pulmonary Plexus

The pulmonary plexus is a network of nerves that provides autonomic (involuntary) innervation to the lungs and bronchi. It’s formed by sympathetic and parasympathetic fibers and is located around the main bronchi at the hilum of the lungs.

lymph drainage of lungs

Pulmonary Lymph Nodes —> Hilar Lymph Nodes —> Mediastinal Lymph Nodes —> right lymphatic duct or thoracic duct (left lung) —> right and left subclavian

-subcarinal lymph nodes that drain from both lungs

boundaries of inferior mediastinum

superior: sternal angle (T5 vertebrae)

inferior: diaphragm

anterior: sternum body

posterior: T5- T12

switch left and right

Course of the Thoracic Duct

• Origin: The thoracic duct begins at the cisterna chyli (a dilated sac) at the level of L1-L2 in the abdomen.

• Abdominal Course: It ascends along the right side of the aorta in the abdomen, passing through the diaphragm at the aortic hiatus at T12.

• Thoracic Course: In the thoracic cavity, it initially runs along the right side of the vertebral column, then crosses to the left side around T5-T6.

• Termination: The duct empties into the left venous angle, where the left internal jugular vein meets the left subclavian vein.