Human Anatomy - Heart Overview

Human Anatomy - Heart

• Course register code: 498185
• Lecturer: Dr Lucy Smyth
• Email: [email protected]
• Topics covered will include heart location, structure (gross and micro anatomy), function (cardiac cycle), and the heart conduction system
• The cardiovascular system contains the heart, blood vessels, and blood

Heart Location

• Located in the thoracic cavity
• More specifically, the mediastinum region of the thorax

Heart Structure

• The heart has four chambers: two atria and two ventricles
• Gross Anatomy: External features of the heart
• Micro Anatomy: Microscopic detail, including cardiomyocytes (myocytes / cardiac muscle cells)
• Layers of the heart wall include the endocardium, myocardium, and epicardium (visceral pericardium).

Cardiac Muscle Cells (Myocytes / Cardiocytes)

• Features: single centrally located nucleus, branching structure, numerous mitochondria
• Other features: Abundant myoglobin reserves, myofibrils for contraction, intercalated discs for connection with other cells

Intercalated Discs

• Composed of adherens junctions, desmosomes, and gap junctions
• Support synchronized contraction of cardiac tissue

Adherens Junctions

• Anchoring sites for actin
• Connect sarcomeres together

Desmosomes

• Prevent cell separation during contraction
• Bind intermediate filaments to join cells together

Gap Junctions

• Allow action potentials to spread between cardiac cells
• Permit ion passage between cells

T-Tubules

• Deep invaginations of the cell plasma membrane

Heart Function (Cardiac Cycle)

• The heart's job is to pump blood.

• Systole: Contraction phase

• Diastole: Relaxation phase

• The cycle involves the movement of blood through the cardiac chambers, controlled by atrioventricular (AV) valves and semilunar valves

Cardiac Cycle Stages

• Atrial and ventricular diastole
• Atrial systole, ventricular diastole
• Ventricular systole, atrial diastole

Heart Valves

• AV valves: Tricuspid and mitral valves
• Semilunar valves: Pulmonary and aortic valves
• Valve closing creates heart sounds ("lub-dub") essential for one-way blood flow

Two Circulatory Circuits

• Pulmonary circuit: Right heart to lungs to left heart
• Systemic circuit: Left heart to body to right heart

Coronary Circulation

• Blood flow through vessels supplying the heart muscle
• Includes main coronary arteries: left main coronary artery, left circumflex coronary artery, left anterior descending coronary artery, right coronary artery, right marginal coronary artery, posterior interventricular artery

Pathologies

• Atherosclerosis: Narrowed artery lumen due to plaque buildup
• Heart attack: Blockage in coronary artery leading to damaged heart tissue
• Treatments: Percutaneous transluminal coronary angioplasty (PTCA), coronary artery bypass surgery (CABG)

Conduction System

• Composed of autorhythmic fibers (pacemaker cells and conduction fibres)
• Components: Sinoatrial (SA) node, atrioventricular (AV) node, Bundle of His, Bundle branches, Purkinje fibers
• ECG can detect pathologies in conduction system

Fetal Circulation

• Oxygen supplied from maternal blood
• Structures: Ductus arteriosus, foramen ovale, ductus venosus
• Structures close after birth

Congenital Heart Defects

• Atrial septal defect (ASD): Hole between atria
• Ventricular septal defect (VSD): Hole between ventricles
• Patent ductus arteriosus (PDA): Duct remains open after birth

12 Lead ECG

• Electrocardiogram (diagnostic tool for heart conditions)
• Electrode placement: V1-V6
• ECG trace: P wave, QRS complex, T wave
• Patterns reveal heart's electrical activity
• Used to diagnose conduction system disorders

Practise Questions

• Available for further study