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Cardiovascular System - Complete Anatomy (BAMS Syllabus)

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1. Introduction and Overview

• The heart - a muscular pump
• Blood vessels - arteries, veins, and capillaries
• Blood - the transport medium

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2. Position and Location of the Heart

• It has the general shape of a pyramid that has fallen over on one of its sides
• The apex projects forward, downward, and to the left - located deep to the left 5th intercostal space, 8-9 cm from the midsternal line (site of apex beat)
• The base (posterior surface) faces posteriorly and consists primarily of the left atrium + small portion of the right atrium

• Right border: Right atrium
• Left border: Left ventricle + left auricle
• Superior border: Atria, auricles, great vessels
• Inferior border: Right ventricle + apex of left ventricle

• Gray's Anatomy for Students, p.225-226

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3. Pericardium

A. Fibrous Pericardium

• Tough connective tissue outer layer
• Cone-shaped bag with its base on the diaphragm and its apex continuous with the adventitia of the great vessels
• Attachments:
  • Base attached to the central tendon of the diaphragm (also small muscular area on the left)
  • Anteriorly attached to the posterior sternum by sternopericardial ligaments
  • Posteriorly attached by bands to the trachea and vertebral column
• Functions: retains heart in thoracic position; limits cardiac distension

B. Serous Pericardium (two layers)

Pericardial Sinuses

• Transverse pericardial sinus: A groove lying between the arterial opening (aorta + pulmonary trunk anteriorly) and the venous opening (great veins posteriorly). Important in cardiac surgery - a finger placed in this sinus can compress both the aorta and pulmonary trunk.
• Oblique pericardial sinus: A blind recess posterior to the left atrium, bounded by the inferior pulmonary veins and inferior vena cava.

Nerve and Blood Supply of Pericardium

• Arterial supply: Pericardiacophrenic artery (branch of internal thoracic artery)
• Venous drainage: Pericardiacophrenic vein → brachiocephalic vein
• Innervation: Phrenic nerve (C3-C5), vagus nerve, sympathetic trunk

Clinical note: The phrenic nerve passes through the fibrous pericardium on its way to the diaphragm. Pericarditis with referred pain to the shoulder is mediated via this phrenic pathway. Pericardial effusion (fluid accumulation) can compress the heart - called cardiac tamponade.

• Gray's Anatomy for Students, p.221-224
• Color Atlas of Human Anatomy Vol. 2, p.67-68

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4. Walls of the Heart (Layers)

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5. Chambers of the Heart

A. Right Atrium

• Receives deoxygenated blood from the body via:
  • Superior vena cava (SVC) - from head, neck, upper limbs
  • Inferior vena cava (IVC) - from trunk, lower limbs
  • Coronary sinus - from heart muscle itself
• Internal features:
  • Crista terminalis: A vertical muscular ridge separating the smooth posterior wall (sinus venarum) from the rough anterior wall with musculi pectinati
  • Fossa ovalis: An oval depression in the interatrial septum; remnant of the fetal foramen ovale
  • Tricuspid valve orifice: Leads to right ventricle
• Right auricle: A small muscular pouch projecting from the right atrium

B. Right Ventricle

• Pumps blood to the lungs via the pulmonary trunk
• Forms most of the anterior surface of the heart
• Internal features:
  • Trabeculae carneae: Muscular ridges and bridges on the inner wall
  • Papillary muscles (anterior, posterior, septal): Attach to the tricuspid valve via chordae tendineae
  • Chordae tendineae: Tendinous cords preventing valve eversion
  • Moderator band (septomarginal trabecula): A muscular band crossing the right ventricle from the septum to the anterior papillary muscle; carries part of the right bundle branch of the conduction system
  • Infundibulum (conus arteriosus): Smooth-walled outflow tract leading to the pulmonary valve

C. Left Atrium

• Receives oxygenated blood from the lungs via 4 pulmonary veins (2 right, 2 left)
• Forms the base (posterior surface) of the heart
• Internal features:
  • Posterior (smooth) wall receives the pulmonary veins
  • Anterior half continuous with the left auricle, contains musculi pectinati
  • Valve of foramen ovale: Thin area in the interatrial septum; may remain probe patent in some adults
• Mitral valve orifice: Leads to the left ventricle

D. Left Ventricle

• Pumps oxygenated blood to the entire body via the aorta
• Forms the apex of the heart
• Has the thickest myocardium (wall ~3× thicker than right ventricle) due to the high pressure of systemic circulation
• Internal features:
  • Fine, delicate trabeculae carneae
  • 2 papillary muscles (anterior and posterior) - larger than those of right ventricle
  • Chordae tendineae attached to mitral valve cusps
  • Aortic vestibule: Smooth-walled outflow tract (posterior to right ventricular infundibulum) leading to the aortic valve

• Muscular part: Thick; forms the major portion
• Membranous part: Thin, upper portion; site of ventricular septal defect (VSD)
• The superior (atrioventricular) part lies between the left ventricle and right atrium
• Gray's Anatomy for Students, p.226-248

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6. Valves of the Heart

• Right coronary sinus → gives off right coronary artery
• Left coronary sinus → gives off left coronary artery
• Non-coronary (posterior) sinus → no coronary artery
• Color Atlas of Human Anatomy Vol. 2

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7. Coronary Circulation

Right Coronary Artery (RCA)

• Arises from the right aortic sinus
• Runs in the right atrioventricular (coronary) groove
• Main branches:
  • SA nodal artery (in ~60% of people) - supplies the sinoatrial node
  • Right marginal artery - supplies right ventricle margin
  • Posterior interventricular (posterior descending) artery - supplies posterior interventricular septum
  • AV nodal artery (in ~80% of people)
• Supplies: Right atrium, right ventricle, SA node, AV node (usually), posterior 1/3 of interventricular septum

Left Coronary Artery (LCA)

• Arises from the left aortic sinus
• Short trunk that divides into:
  1. Left Anterior Descending (LAD) artery (anterior interventricular artery) - runs in the anterior interventricular groove; supplies the anterior 2/3 of the interventricular septum, anterior left and right ventricles, and the apex
  2. Left Circumflex artery - runs in the left atrioventricular groove; supplies left atrium and left ventricle posterior wall
• Supplies: Most of the left ventricle, most of the interventricular septum, left atrium, and (in ~40%) SA node

Coronary Dominance

• Right dominant (~70%): RCA gives posterior descending artery
• Left dominant (~10%): LCA gives posterior descending artery
• Co-dominant (~20%)

Venous Drainage of the Heart

• Coronary sinus: The main venous drainage channel; lies in the posterior AV groove; drains into the right atrium
  • Great cardiac vein → coronary sinus
  • Middle cardiac vein → coronary sinus
  • Small cardiac vein → coronary sinus
• Anterior cardiac veins: Drain directly into the right atrium
• Thebesian veins (smallest cardiac veins): Drain directly into chambers

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8. Conducting System of the Heart

• SA node: 60-100/min
• AV node: 40-60/min
• Bundle of His/Purkinje: 20-40/min

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9. Nerve Supply of the Heart (Cardiac Innervation)

• Sympathetic is the "fight or flight" system
• Parasympathetic (vagal) is the "rest and digest" system; dominant at rest

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10. Great Vessels

A. Aorta

• Ascending aorta: Gives off left and right coronary arteries
• Aortic arch: Gives off 3 branches (right to left):
  1. Brachiocephalic trunk → right subclavian + right common carotid arteries
  2. Left common carotid artery
  3. Left subclavian artery
• Descending thoracic aorta: Gives off posterior intercostal arteries, bronchial arteries
• Passes through the aortic hiatus of the diaphragm at T12 to become the abdominal aorta

B. Pulmonary Trunk

• Arises from the right ventricle (infundibulum)
• Divides into right and left pulmonary arteries beneath the aortic arch at the level of sternal angle (T4/T5) - also called the carina level
• Carries deoxygenated blood to the lungs

C. Venae Cavae

• Superior vena cava (SVC): Formed by union of the two brachiocephalic veins behind the first right costal cartilage; drains head, neck, upper limbs, thorax
• Inferior vena cava (IVC): Drains lower limbs, abdomen; enters right atrium through the caval hiatus of the diaphragm at T8

D. Pulmonary Veins (4 total)

• 2 right (superior and inferior) + 2 left (superior and inferior)
• Carry oxygenated blood from lungs to the left atrium

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11. Circulatory Pathways

Systemic (Greater) Circulation

Pulmonary (Lesser) Circulation

Portal Circulation

Fetal Circulation (Special Shunts)

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12. Blood Vessels - General Classification

Arteries

• Carry blood away from the heart (usually oxygenated, except pulmonary artery)
• Elastic arteries (aorta, pulmonary trunk): Large; distensible; act as pressure reservoirs
• Muscular arteries (coronary, femoral): Medium; control blood flow by vasoconstriction/dilation
• Arterioles: Small; major site of peripheral resistance

Capillaries

• Single-cell-thick walls (endothelium only)
• Site of gas, nutrient, and waste exchange between blood and tissues
• Types: Continuous, fenestrated, sinusoidal (discontinuous)

Veins

• Carry blood toward the heart
• Thinner walls, larger lumens than corresponding arteries
• Contain valves (especially in limbs) to prevent backflow
• Act as capacitance vessels (hold ~70% of total blood volume)

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13. Lymphatic System (Related to CVS)

• Drains excess interstitial fluid back to venous circulation
• Thoracic duct: The largest lymphatic vessel; drains from below the diaphragm + left side of body → left subclavian vein
• Right lymphatic duct: Drains right side of head, neck, thorax, right upper limb → right subclavian vein
• Lymph nodes filter lymph and house immune cells

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14. Applied Anatomy (Clinical Points for BAMS)

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Quick Revision Summary

Heart location: Middle mediastinum, behind sternum, left of midline
Apex: Left 5th ICS, 8-9 cm from midsternal line
Pericardium: Fibrous + serous (parietal + visceral/epicardium)
Chambers: RA, RV, LA, LV
Right side: Deoxygenated blood (systemic veins → lungs)
Left side: Oxygenated blood (lungs → systemic circulation)
Valves: AV valves (tricuspid/mitral) + Semilunar valves (pulmonary/aortic)
Coronary arteries: RCA + LCA (from aortic sinuses)
Conduction: SA node → AV node → Bundle of His → Bundle branches → Purkinje fibers
Great vessels: Aorta, Pulmonary trunk, SVC, IVC, 4 pulmonary veins