Anatomy
MBBS Anatomy question bank: general anatomy and osteology, regional gross anatomy (upper limb, lower limb, thorax, abdomen, pelvis, head and neck), neuroanatomy, histology and embryology.
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Definition
The thoracic wall forms a bony cage protecting the heart and lungs and enabling respiration; the intercostal spaces lie between the ribs.
Bony Framework
- 12 pairs of ribs
- Sternum (manubrium, body, xiphoid)
- 12 thoracic vertebrae
- Costal cartilages
Intercostal Muscles
- External — elevate ribs (inspiration)
- Internal — depress ribs (expiration)
- Innermost
Neurovascular Bundle (VAN)
- Runs in the costal groove
- Order top→bottom: Vein, Artery, Nerve
- Lies just below the rib
The rib cage protects the viscera; the neurovascular bundle runs in the costal groove. Muscle Action External Inspiration (elevate ribs) Internal Expiration Innermost Support Applied
- Chest drain above the rib (avoid the bundle)
- Intercostal nerve block
🔑KEY POINTS TO REMEMBER- Thorax: 12 ribs, sternum, 12 vertebrae, costal cartilages.
- Intercostal bundle (VAN) in the costal groove, below the rib.
- Chest tube above the lower rib.
📚SOURCES: BD Chaurasia’s Human Anatomy; Gray’s Anatomy; Snell’s Clinical Anatomy.Definition
The diaphragm is the dome-shaped musculotendinous partition separating thorax from abdomen; it is the chief muscle of respiration.
Attachments (Origin)
- Sternal — xiphoid process
- Costal — lower 6 ribs
- Vertebral — crura (L1–L3), arcuate ligaments
Openings
- T8 — IVC (+ right phrenic)
- T10 — oesophagus (+ vagi)
- T12 — aorta (+ thoracic duct, azygos)
Nerve Supply
- Motor — phrenic nerve (C3, 4, 5)
- ‘C3, 4, 5 keep the diaphragm alive’
Contraction flattens the diaphragm to draw air in; three openings pass key structures. Level Opening Structures T8 Caval IVC, right phrenic T10 Oesophageal Oesophagus, vagi T12 Aortic Aorta, thoracic duct Applied
- Phrenic injury → diaphragmatic paralysis
- Hiatus hernia (T10)
- Referred pain to shoulder (C3, 4)
🔑KEY POINTS TO REMEMBER- Diaphragm: chief respiratory muscle; phrenic nerve (C3,4,5).
- Openings: T8 IVC, T10 oesophagus, T12 aorta.
- Hiatus hernia at T10.
📚SOURCES: BD Chaurasia’s Human Anatomy; Gray’s Anatomy; Snell’s Clinical Anatomy.Definition
The mediastinum is the central compartment of the thorax between the two pleural sacs; it contains the heart and great vessels.
Divisions
- Superior mediastinum (above the sternal angle)
- Inferior — anterior, middle (heart), posterior
Heart
- Four chambers (2 atria, 2 ventricles)
- Enclosed in pericardium (middle mediastinum)
- Apex — left 5th intercostal space, midclavicular line
Borders (on X-ray)
- Right — right atrium
- Left — left ventricle
- Inferior — right ventricle
The heart occupies the middle mediastinum, within the pericardium. Chamber Forms Right atrium Right border Left ventricle Left border, apex Right ventricle Most of the front Applied
- Mediastinal masses
- Apex beat displaced in cardiomegaly
🔑KEY POINTS TO REMEMBER- Mediastinum: superior + inferior (anterior, middle, posterior).
- Heart in the middle mediastinum; apex at left 5th ICS, MCL.
- Right border = RA; left border/apex = LV.
📚SOURCES: BD Chaurasia’s Human Anatomy; Gray’s Anatomy; Snell’s Clinical Anatomy.Definition
The lungs are the paired organs of respiration; the pleura is the serous membrane covering them.
Lungs
- Right — 3 lobes (upper, middle, lower)
- Left — 2 lobes (+ cardiac notch, lingula)
- Hilum — root of lung (bronchi, vessels)
- Divided into bronchopulmonary segments
Pleura
- Visceral — covers the lung
- Parietal — lines the thoracic wall
- Pleural cavity — thin fluid, negative pressure
Root of Lung
- Bronchus, pulmonary artery & veins
- Right and left arrangements differ
A thin pleural cavity separates the two layers of pleura. Lung Lobes Feature Right 3 Shorter, wider bronchus Left 2 Cardiac notch, lingula Applied
- Pneumothorax, pleural effusion
- Aspiration → right lung (wider, vertical bronchus)
🔑KEY POINTS TO REMEMBER- Right lung 3 lobes; left 2 lobes (cardiac notch, lingula).
- Pleura: visceral (lung) + parietal (wall).
- Aspiration favours the right lung.
📚SOURCES: BD Chaurasia’s Human Anatomy; Gray’s Anatomy; Snell’s Clinical Anatomy.Definition
The great vessels arise from or enter the heart; the posterior mediastinum lies behind the pericardium and contains the descending aorta, oesophagus and thoracic duct.
Great Vessels
- Ascending aorta → arch → descending aorta
- Pulmonary trunk → pulmonary arteries
- Superior & inferior vena cava
Aortic Arch Branches
- Brachiocephalic trunk
- Left common carotid
- Left subclavian
Posterior Mediastinum Contents
- Descending thoracic aorta
- Oesophagus
- Thoracic duct
- Azygos vein, sympathetic chain
The aorta arches over, giving three branches, then descends through the posterior mediastinum. Vessel Carries Aorta Oxygenated blood to body Pulmonary trunk Deoxygenated to lungs Pulmonary veins Oxygenated to heart Applied
- Aortic aneurysm / coarctation
- Oesophageal relations (tracheo-oesophageal fistula)
🔑KEY POINTS TO REMEMBER- Aorta: ascending → arch (3 branches) → descending.
- Arch branches: brachiocephalic, L common carotid, L subclavian.
- Posterior mediastinum: aorta, oesophagus, thoracic duct.
📚SOURCES: BD Chaurasia’s Human Anatomy; Gray’s Anatomy; Snell’s Clinical Anatomy.Definition
An intercostal space lies between two ribs, containing three muscle layers and the neurovascular bundle.
Muscles (3 layers)
- External intercostal
- Internal intercostal
- Innermost intercostal
Neurovascular Bundle (VAN)
- Runs in the costal groove
- Order (top→bottom): Vein, Artery, Nerve
- Lies just below the rib
The bundle runs in the costal groove, vein-artery-nerve from top down. Structure Order Vein Highest Artery Middle Nerve Lowest Applied
- Insert chest tube just ABOVE the lower rib
- Avoids the neurovascular bundle
🔑KEY POINTS TO REMEMBER- Three muscle layers; bundle in the costal groove.
- Order VAN (vein, artery, nerve), top to bottom.
- Chest tube above the lower rib.
📚SOURCES: BD Chaurasia’s Human Anatomy; Gray’s Anatomy; Snell’s Clinical Anatomy.Definition
The diaphragm has three major openings transmitting structures between thorax and abdomen, at vertebral levels T8, T10, T12.
Openings
- T8 (caval) — IVC + right phrenic nerve
- T10 (oesophageal) — oesophagus + vagus nerves
- T12 (aortic) — aorta + thoracic duct + azygos vein
Three openings at T8, T10 and T12 pass the IVC, oesophagus and aorta. Level Opening Structures T8 Caval IVC, right phrenic T10 Oesophageal Oesophagus, vagi T12 Aortic Aorta, thoracic duct, azygos Applied
- Hiatus hernia (T10 oesophageal opening)
- Number of vowels = number of structures
🔑KEY POINTS TO REMEMBER- T8 = IVC; T10 = oesophagus + vagi; T12 = aorta + thoracic duct.
- Hiatus hernia at T10.
📚SOURCES: BD Chaurasia’s Human Anatomy; Gray’s Anatomy; Snell’s Clinical Anatomy.Definition
The coronary arteries supply the heart muscle, arising from the ascending aorta at the aortic sinuses.
Right Coronary Artery (RCA)
- Right atrium and right ventricle
- SA node (~60%) and AV node
- Inferior wall of the heart
Left Coronary Artery (LCA)
- Divides into LAD + circumflex
- LAD — anterior wall, interventricular septum
- Circumflex — lateral wall, left atrium
Two coronary arteries arise from the aorta; blockage causes an infarct. Artery Supplies RCA RA, RV, SA/AV node LAD Anterior wall, septum Circumflex Lateral wall Applied
- LAD block = the ‘widow-maker’
- MI localised by the artery involved
🔑KEY POINTS TO REMEMBER- RCA → RA/RV, SA/AV node, inferior wall.
- LCA → LAD (anterior/septum) + circumflex (lateral).
- LAD = widow-maker.
📚SOURCES: BD Chaurasia’s Human Anatomy; Gray’s Anatomy; Snell’s Clinical Anatomy.Definition
The conducting system generates and conducts impulses for the heartbeat, made of specialised cardiac muscle.
Components
- SA node — pacemaker (right atrium)
- AV node — delays the impulse
- Bundle of His + bundle branches
- Purkinje fibres
The impulse runs SA node → AV node → His → Purkinje to the ventricles. Structure Location SA node Right atrium AV node Interatrial septum Purkinje Ventricular walls Applied
- Heart block (AV node)
- Artificial pacemaker
🔑KEY POINTS TO REMEMBER- SA node (pacemaker) → AV node → His → Purkinje.
- SA in right atrium; AV in interatrial septum.
- AV block → pacemaker.
📚SOURCES: BD Chaurasia’s Human Anatomy; Gray’s Anatomy; Snell’s Clinical Anatomy.Definition
The pericardium is the double-layered fibroserous sac enclosing the heart in the middle mediastinum.
Layers
- Fibrous pericardium — tough outer layer
- Serous — parietal + visceral (epicardium)
- Pericardial cavity — serous fluid (lubrication)
Sinuses
- Transverse sinus
- Oblique sinus
A tough fibrous sac plus a serous lining, with fluid, surrounds the heart. Layer Feature Fibrous Tough, protective Serous Parietal + visceral Applied
- Pericardial effusion → cardiac tamponade
- Pericarditis
🔑KEY POINTS TO REMEMBER- Pericardium: fibrous + serous (parietal + visceral).
- Pericardial cavity has lubricating fluid.
- Effusion → tamponade.
📚SOURCES: BD Chaurasia’s Human Anatomy; Gray’s Anatomy; Snell’s Clinical Anatomy.Definition
The pleura is a serous membrane covering the lungs; pleural recesses are spaces where the lung does not fully fill the pleural cavity.
Layers
- Visceral (covers the lung)
- Parietal (lines the wall)
- Pleural cavity (thin fluid film)
Recesses
- Costodiaphragmatic — largest, at the lung base
- Costomediastinal
- Fluid collects here (effusion)
Recesses are potential spaces where the lung does not reach, collecting fluid. Recess Location Costodiaphragmatic Base (rib–diaphragm) Costomediastinal Front Applied
- Pleural tap at the costodiaphragmatic recess
- Effusion, empyema
🔑KEY POINTS TO REMEMBER- Pleura: visceral + parietal; thin fluid between.
- Costodiaphragmatic recess = largest, at the base.
- Site for pleural tap.
📚SOURCES: BD Chaurasia’s Human Anatomy; Gray’s Anatomy; Snell’s Clinical Anatomy.Definition
The thoracic duct is the largest lymphatic channel, draining lymph from most of the body into the venous system.
Course
- Begins at the cisterna chyli (L1–L2)
- Enters thorax through the aortic opening (T12)
- Ascends the posterior mediastinum
- Drains into the left subclavian–internal jugular junction
Drainage Area
- Whole body EXCEPT the right upper quadrant
- (right side drained by the right lymphatic duct)
The thoracic duct carries lymph from most of the body to the left venous angle. Feature Detail Origin Cisterna chyli Ends Left venous angle Drains All except right upper quadrant Applied
- Injury → chylothorax
- Left supraclavicular node (Virchow’s node)
🔑KEY POINTS TO REMEMBER- Thoracic duct: cisterna chyli → T12 → left venous angle.
- Drains all but the right upper quadrant.
- Injury → chylothorax.
📚SOURCES: BD Chaurasia’s Human Anatomy; Gray’s Anatomy; Snell’s Clinical Anatomy.