Enhance your knowledge with our comprehensive guide and curated study materials.
Mnemonic: “Come Down My Chest”
C → Costal pleura
D → Diaphragmatic pleura
M → Mediastinal pleura
C → Cervical pleura
These are the four regions of the parietal pleura lining the thoracic wall, diaphragm, mediastinum, and the apex of the lung respectively.
Mnemonic: “Cool Cat”
C → Costomediastinal recess
C → Costodiaphragmatic recess
These are potential spaces of the pleural cavity into which the lungs expand during deep inspiration.
Mnemonic: “I Miss Pain”
I → Intercostal nerves (for costal and peripheral diaphragmatic pleurae)
M → Mediastinal pleura (by phrenic nerve)
P → Phrenic nerve (C4) for central diaphragmatic pleura
A → Autonomic nerves for visceral pleura (sympathetic and parasympathetic)
I → Insensitive to pain (visceral pleura)
N → Nerve roots from T2–T5 (sympathetic) and vagus nerve (parasympathetic)
Mnemonic: “Some Doctors Intervene Carefully, Preventing Pain”
S → Skin
D → Deep fascia
I → Intercostal muscles (external, internal, innermost)
C → Costal parietal pleura
P → Pleural cavity
This sequence helps recall the structures traversed by the needle during pleural tapping.
Mnemonic: “PHEHE”
P → Pneumothorax – Air
H → Haemothorax – Blood
E → Empyema – Pus
H → Hydropneumothorax – Air + Fluid
E → Effusion (Pleural) – Serous fluid
Mnemonic: “Ribs Dine Medially”
Ribs → Costal pleura (outer wall)
Diaphragm → Diaphragmatic pleura (floor)
Medially → Mediastinal pleura (medial wall)
Mnemonic: “Shoulder for Phrenic, Chest for Intercostal”
Irritation of phrenic nerve → pain at shoulder tip (C4 dermatome).
Irritation of intercostal nerves → pain along thoracic wall.
These mnemonics simplify recall of pleural anatomy, innervation, and clinical procedures, making them ideal for quick revision during viva or exams.
The thoracic cavity is divided into three parts: right pleural cavity, left pleural cavity, and the mediastinum in the centre.
Each pleural cavity is lined by a serous membrane called the pleura, which has two layers — parietal and visceral.
The pleural cavity contains a thin film of serous fluid, which lubricates the surfaces and allows smooth movement of lungs during respiration.
Parts of parietal pleura:
Costal pleura — lines ribs and intercostal spaces.
Diaphragmatic pleura — covers diaphragm’s upper surface.
Mediastinal pleura — forms lateral wall of mediastinum.
Cervical pleura (cupula) — extends into the root of neck.
The pleural reflections mark the junctions of various parts of the pleura; they form recesses where the lungs expand during deep inspiration.
The costodiaphragmatic recess is the deepest part of pleural cavity, situated between the 8th and 10th ribs along the midaxillary line.
The costomediastinal recess is more prominent on the left side, near the cardiac notch of the left lung.
The pulmonary ligament is a double fold of pleura below the lung root that allows descent of the lung root during inspiration.
The parietal pleura is pain sensitive, supplied by intercostal nerves and phrenic nerve.
Costal and peripheral diaphragmatic pleurae → intercostal nerves.
Mediastinal and central diaphragmatic pleurae → phrenic nerve.
The visceral pleura is pain insensitive, supplied by autonomic nerves (sympathetic and vagal).
Blood supply:
Parietal pleura → intercostal, internal thoracic, and musculophrenic arteries.
Venous return → azygos and internal thoracic veins.
Lymphatic drainage:
Anteriorly → internal mammary nodes.
Posteriorly → posterior intercostal nodes → thoracic duct.
Clinical conditions:
Pleurisy → inflammation of pleura with severe pain due to parietal pleural irritation.
Pleural effusion → collection of fluid in pleural cavity.
Pneumothorax → air in pleural cavity causing lung collapse.
Haemothorax → accumulation of blood.
Empyema → pus in pleural cavity.
Referred pain:
Intercostal nerve supply → pain along chest wall.
Phrenic nerve supply → pain referred to shoulder tip (C4 dermatome).
Pleural tap (paracentesis thoracis):
Needle inserted in lower intercostal space, just above the upper border of a rib, to avoid injury to intercostal vessels and nerve.
The pleura is derived embryologically from mesoderm — parietal pleura from somatopleuric layer, and visceral pleura from splanchnopleuric layer.
The pleural cavity is a potential space — under normal conditions, it contains only a minimal amount of fluid to reduce friction between the pleural surfaces.
These facts give a concise yet complete overview of the thoracic cavity and pleura, integrating their structure, nerve supply, and clinical significance for quick revision.
Problem:
A 40-year-old patient presents with severe, sharp pain on the right side of the chest that worsens during deep breathing and coughing.
Diagnosis:
Acute Pleurisy (Pleuritis)
Anatomical Explanation:
The parietal pleura (especially costal part) is supplied by intercostal nerves, making it pain-sensitive.
Inflammation causes friction between pleural layers, producing sharp, localized pain along the affected intercostal dermatome.
The visceral pleura is insensitive to pain, so discomfort is absent if only it is involved.
Problem:
A patient with right-sided pleural effusion complains of pain in the right shoulder tip.
Diagnosis:
Referred pain due to diaphragmatic pleurisy
Anatomical Explanation:
The central diaphragmatic pleura and mediastinal pleura are supplied by the phrenic nerve (C4).
The C4 dermatome corresponds to the shoulder tip, hence irritation is perceived as shoulder pain.
Problem:
A 50-year-old man develops breathlessness and dullness on percussion over the right lower chest. X-ray shows fluid level in the pleural cavity.
Diagnosis:
Pleural Effusion
Anatomical Explanation:
Fluid collects in the costodiaphragmatic recess, the most dependent part of the pleural cavity.
As the fluid accumulates, it compresses the underlying lung, reducing expansion and causing dyspnea.
Problem:
A young man develops sudden breathlessness following a stab wound to the chest.
Diagnosis:
Pneumothorax
Anatomical Explanation:
The penetrating wound allows air to enter the pleural cavity, destroying the negative intrapleural pressure and causing lung collapse.
If air enters during inspiration but cannot escape during expiration, tension pneumothorax develops — a medical emergency causing mediastinal shift.
Problem:
Where should the needle be inserted for safe aspiration of pleural fluid?
Answer:
The needle should be introduced in the lower intercostal space, just above the upper border of a rib (commonly in the 8th intercostal space, midaxillary line).
This avoids injury to the intercostal vein, artery, and nerve lying in the costal groove of the rib above.
Problem:
A patient with pneumonia develops fever, chest pain, and accumulation of pus in the pleural cavity.
Diagnosis:
Empyema Thoracis
Anatomical Explanation:
Infection spreads from the lung parenchyma through the visceral pleura into the pleural cavity.
The pleural cavity becomes filled with purulent fluid, often requiring drainage.
Problem:
After a road accident, a patient’s X-ray reveals fluid level consistent with blood in the pleural cavity.
Diagnosis:
Haemothorax
Anatomical Explanation:
Rupture of intercostal vessels or internal thoracic artery causes bleeding into the pleural cavity.
The costodiaphragmatic recess fills first, leading to respiratory distress.
Problem:
A patient with penetrating chest injury shows collapsed right lung with tracheal deviation to the opposite side.
Diagnosis:
Tension Pneumothorax
Anatomical Explanation:
One-way entry of air into the pleural cavity raises intrathoracic pressure.
This compresses the opposite lung and shifts the mediastinum, compromising venous return and causing respiratory failure.
Problem:
A 30-year-old patient with tuberculosis presents with recurrent right-sided pleural effusion.
Anatomical Explanation:
Tubercular infection causes exudation into the pleural cavity and thickening of the pleura.
Repeated inflammation leads to pleural adhesions and restricted lung expansion.
Problem:
A patient with lower lobe pneumonia experiences shoulder pain and hiccups.
Diagnosis:
Irritation of phrenic nerve due to diaphragmatic pleurisy
Anatomical Explanation:
The phrenic nerve (C3–C5) supplies the diaphragm and its pleura.
Inflammation irritates the nerve, producing referred pain to the shoulder (C4) and hiccups due to diaphragmatic spasm.
Problem:
A patient complains of sharp, stabbing chest pain on deep inspiration but no fluid collection is found on imaging.
Diagnosis:
Dry (Fibrinous) Pleurisy
Anatomical Explanation:
Inflammation of the parietal pleura causes its roughened surfaces to rub against the visceral pleura during breathing, producing pleuritic friction rub and severe localized pain.
Since the parietal pleura is supplied by intercostal and phrenic nerves, the pain is sharp and well localized.
Problem:
A patient who had recurrent pleurisy now shows thickened, adherent pleural layers with restricted lung movement.
Diagnosis:
Pleural Adhesion (Fibrosis)
Anatomical Explanation:
Repeated inflammation leads to fibrosis of the parietal and visceral pleura, obliterating the pleural cavity.
The normally smooth movement of pleurae is lost, leading to stiff lungs and reduced ventilation.
Problem:
After an injury to the neck, a patient develops accumulation of milky white fluid in the pleural cavity.
Diagnosis:
Chylothorax
Anatomical Explanation:
Damage to the thoracic duct (especially near its termination in the left venous angle) causes leakage of lymph (chyle) into the left pleural cavity.
The fluid has a characteristic milky appearance due to its high fat content.
Problem:
Following a penetrating chest wound, air enters and escapes freely through the chest wall during respiration.
Diagnosis:
Open Pneumothorax
Anatomical Explanation:
Air moves in and out of the pleural cavity with each breath, preventing normal lung expansion.
Negative intrapleural pressure is lost, and the affected lung collapses.
The mediastinum may swing with respiration (mediastinal flutter), impairing venous return.
Problem:
A patient develops severe dyspnea, tracheal deviation, and cyanosis following chest trauma.
Diagnosis:
Tension Pneumothorax
Anatomical Explanation:
Air enters the pleural cavity during inspiration but cannot escape during expiration due to a flap-valve effect.
The pressure rises, compressing the opposite lung and shifting the mediastinum to the opposite side, reducing venous return and cardiac output — a life-threatening emergency.
Problem:
A patient with basal pneumonia complains of pain in the right upper abdomen.
Diagnosis:
Referred pain due to diaphragmatic pleurisy
Anatomical Explanation:
The diaphragmatic pleura (central part) is supplied by the phrenic nerve (C4).
Irritation refers pain to the right shoulder and upper abdomen, simulating gallbladder or hepatic pain.
Problem:
A patient with congestive heart failure develops fluid accumulation in both pleural cavities.
Diagnosis:
Hydrothorax
Anatomical Explanation:
Increased venous pressure in systemic and pulmonary circulation leads to transudation of fluid into the pleural cavity.
The costodiaphragmatic recess fills first, restricting lung expansion.
Problem:
A patient recovering from tuberculous pleurisy shows dense pleural fibrosis causing mediastinal shift.
Diagnosis:
Fibrothorax
Anatomical Explanation:
Chronic infection or effusion leads to organization of exudate, forming a thick fibrous layer.
This causes lung entrapment and restricted ventilation, with possible deviation of mediastinum toward the affected side.
Problem:
A patient complains of severe pain over the chest wall after thoracotomy.
Diagnosis:
Intercostal nerve irritation or entrapment
Anatomical Explanation:
The intercostal nerves lie in the costal groove under each rib.
If sutures or retractors compress these nerves, neuralgic pain arises along the thoracic wall dermatomes.
Problem:
An X-ray shows elevation of the diaphragm due to fluid under the lower lung base.
Diagnosis:
Subpulmonic Pleural Effusion
Anatomical Explanation:
Fluid collects between the diaphragmatic pleura and the base of the lung, often misinterpreted as diaphragmatic elevation.
The costophrenic angle becomes blunted on imaging.
Problem:
A patient with lung cancer involving the mediastinum presents with unilateral diaphragmatic paralysis and shoulder pain.
Diagnosis:
Phrenic nerve involvement secondary to mediastinal pleural irritation
Anatomical Explanation:
The mediastinal pleura is supplied by the phrenic nerve.
Tumor infiltration irritates the nerve, leading to referred shoulder pain and diaphragmatic paralysis on the same side.
Problem:
A young, tall, thin man develops sudden breathlessness without trauma.
Diagnosis:
Spontaneous Pneumothorax
Anatomical Explanation:
Rupture of a subpleural bleb (small air blister) allows air into the pleural cavity.
The resulting loss of negative intrapleural pressure causes partial or complete lung collapse.
Problem:
A patient treated for empyema develops a non-expanding lung despite clear X-ray.
Diagnosis:
Trapped Lung due to Pleural Thickening
Anatomical Explanation:
Organization of pus in the pleural cavity forms a fibrous peel on the visceral pleura, preventing lung expansion even after drainage.
Problem:
A patient with known bronchogenic carcinoma develops massive right-sided pleural effusion.
Diagnosis:
Malignant (Secondary) Pleural Effusion
Anatomical Explanation:
Tumor invasion of parietal pleura or blockage of pleural lymphatics causes accumulation of malignant exudate.
Cytological examination of pleural fluid confirms malignant cells.
Problem:
A patient develops sudden dyspnea and decreased breath sounds after attempted subclavian vein catheterization.
Diagnosis:
Iatrogenic Pneumothorax
Anatomical Explanation:
The cervical pleura (cupula) projects into the neck above the first rib.
Accidental puncture during central line insertion allows air to enter the pleural cavity, collapsing the lung apex.
Get the full PDF version of this chapter.
Continue with Google