Vertebrate Anatomy: Heart Structure and Function

Cardiovascular System (CVS)

• The CVS is made up of the heart and vessels (veins and arteries)
• The heart has two sides, each acting as a pump:
  • One side pumps to the body (systemic circulation), taking oxygen and nutrients to the tissues
  • One side pumps to the lungs (pulmonary circulation), taking deoxygenated blood to the lungs

Heart Anatomy

• Located in the cranioventral thorax, between the 3rd and 6th/7th ribs, to the left side (behind the elbow)
• Surrounded by lungs and ribs
• Apex beat: where you can palpate (feel) the heart beat, best place to put a stethoscope to auscultate (hear) the heartbeat

Heart Chambers

• Four heart chambers: 2 atria (upper) and 2 ventricles (lower)
• Valves separate the atria from the ventricles
• Muscular walls enable coordinated contractions of cardiac muscle to pump blood
• Atria:
  • Two smaller chambers at the base of the heart
  • Receive blood from the body/lungs when relaxed
  • Pump blood into the ventricles when contracted
• Ventricles:
  • Two large chambers at the apex of the heart
  • Receive blood from the atria when relaxed
  • Pump blood out of the heart (to body/lungs) when contracted

Cardiac Valves

• Function: prevent backflow of blood during ventricular contraction and relaxation
• Ensure one-way flow of blood through the heart
• Made up of "leaflets" or "cusps"
• Two types of valves:
  • Atrioventricular (AV) valves: between atria and ventricles
  • Semi-lunar valves: in the arteries leaving the heart (pulmonary artery and aorta)

Blood Vessels

• Arteries: always carry blood away from the heart, usually carry oxygenated blood
• Veins: always carry blood towards the heart, usually contain deoxygenated blood
• Exceptions: pulmonary arteries and veins, which are the opposite of the usual oxygenation rule

Coronary Circulation

• The heart muscle itself receives oxygen and nutrients through the coronary arteries
• Coronary arteries originate from the base of the aorta and supply oxygenated blood to the heart muscle
• Coronary veins drain deoxygenated blood from the heart muscle back into the right atrium

Structure of the Heart Wall

• Layers of the heart:
  • Pericardium: outer connective tissue layers
  • Myocardium: middle, muscular layer (cardiac muscle)
  • Endocardium: inner-most epithelial lining

Blood Flow through the Heart

• The heart acts as a pump to supply blood to the body
• Two pumps: systemic (left side) and pulmonary (right side)
• Systemic circulation: takes oxygenated blood from the lungs to the body for cellular respiration, and returns depleted blood to the heart
• Pulmonary circulation: takes deoxygenated blood from the body to the lungs, where it releases CO2 and picks up more O2

Test your knowledge of the heart's structures and functions, including atria, ventricles, valves, and blood flow through the systemic and pulmonary circulations.