Blood Flow Through the Heart Quiz

Blood Flow Through the Heart

• Blood from the body enters the heart through the vena cava (superior - upper body, inferior - lower body).
• Blood enters the right atrium (upper-right chamber).
• Blood passes through the tricuspid valve to the right ventricle.
• The right ventricle pumps blood through the pulmonary valve to the pulmonary artery.
• The pulmonary artery carries blood to the lungs for oxygenation.
• Oxygenated blood returns to the heart via the pulmonary veins.
• Blood enters the left atrium (upper-left chamber).
• Blood passes through the bicuspid (mitral) valve to the left ventricle.
• The left ventricle pumps blood through the aortic valve to the aorta.
• Oxygenated blood is carried to the body via the aorta.

Heart Size and Muscle

• The average heart size is roughly the size of a fist.
• Adult heart weight: 250-350 grams (9-12 ounces).
• Adult heart dimensions: approximately 12 cm long, 8 cm wide, and 6 cm deep.
• The other term for cardiac muscle is myocardium.
• The myocardium forms the heart walls, responsible for blood pumping.

Double Pump and Circulatory Systems

• The heart acts as a "double pump," with two circulatory loops.
• The right side pumps blood to the lungs for oxygenation (pulmonary circulation).
• The left side pumps oxygenated blood to the body (systemic circulation).
• Pulmonary circulation: deoxygenated blood is pumped to the lungs via pulmonary arteries. Oxygen is picked up, and carbon dioxide is released.
• Systemic circulation: oxygenated blood is pumped throughout the body via the aorta.

Blood Colour Representation

• The right side of the heart and its vessels are depicted in blue to represent deoxygenated blood.
• The left side of the heart and its vessels are depicted in red to represent oxygenated blood.

Path of Blood

• Superior and Inferior Vena Cava to Right Atrium to Tricuspid Valve to Right Ventricle.
• Then to Pulmonary Valve, Pulmonary Artery, to the Lungs, Pulmonary Veins, Left Atrium, Bicuspid/Mitral Valve, Left Ventricle.
• Finally to Aortic Valve and then Aorta.

Systole and Diastole

• Systole: The heart contracts to pump blood (specifically, the ventricles contract).
• Diastole: The heart relaxes and fills with blood (the atria contract and ventricles prepare to contract again).

Arteries and Veins

• Arteries typically carry oxygen-rich blood from the heart (except pulmonary arteries which carry oxygen-poor blood to the lungs).
• Veins generally carry oxygen-poor blood back to the heart (except pulmonary veins which carry oxygen-rich blood from the lungs).

Blood Pressure

• Low pressure is around 5 mm Hg (e.g., right atrium, pulmonary arteries).
• Pulmonary arteries have lower pressure (15-30 mm Hg) due to lower resistance.
• Ascending aorta has higher pressure (90-120 mm Hg) due to blood being pumped to the whole body (facing more resistance).

Heart's Electrical Activity

• Sinoatrial (SA) node: Heart's pacemaker, located in the right atrium.
• Atria contraction: Pushing blood to the ventricles (from top down).
• Atrioventricular (AV) node: Passes electrical signals from atria to ventricles.
• Purkinje fibers: Help ventricles contract (from bottom up), pushing blood to the body and lungs.
• ECG (electrocardiogram): P wave (atria contraction), QRS complex (ventricle contraction), T wave (ventricle recovery).

Blood Flow Regulation

• Arterioles: Regulate blood flow by constricting or dilating, adjusting blood supply.
• Exercise increases blood flow to muscles, decreases blood flow elsewhere (digestion, for example).
• Orthostatic hypotension: Causes lightheadedness after heavy exercise, when blood pools in the lower body, leading to reduced blood flow to the brain.
• Capillaries: Allow gas and nutrient exchange between blood and tissues.
• Mixed capillary blood: Contains both oxygen-rich and oxygen-poor blood.
• Most significant blood pressure drop occurs in arterioles due to resistance.
• Measurement: Sphygmomanometer is used.

Coronary Circulation

• Coronary arteries: Supply blood to the heart muscle (branch off aorta).
• Left coronary artery: Larger than right, as it supplies a larger area.
• Cardiac venous blood return: Oxygen-poor blood returns via the inferior and superior vena cava.

Cardiovascular Disease and Heart Attack

• CVD: Conditions caused by plaque buildup in arteries, reducing blood flow.
• Heart attack: Blockage in coronary arteries reduces blood flow to the heart; causing damage to heart muscle.

Veins and Blood Return

• Vein diameter control: Smooth muscles constrict or dilate veins.
• Valves in veins: Prevent backflow, ensuring blood flows toward the heart.
• Venous blood return is aided by:
  • Skeletal muscle pump: Muscle contractions push blood.
  • Thoracic pump: Breathing pressure changes aid in return.
  • Nervous system can signal veins to constrict.
  • Venous pooling: Veins act as blood reservoirs.

Oxygen Transport

• Erythrocytes (red blood cells): Transport oxygen (O₂) and carbon dioxide (CO₂) with hemoglobin.

Cardiovascular Dynamics

• Cardiac output (Q): Heart's volume pumped per minute
  • At rest: 5-6 L/min
  • During exercise: 30 L/min
• Increased venous return: Caused by constriction of veins and muscle activity.
• Cardiovascular drift: Gradual increase in heart rate and decrease in stroke volume during extended exercise. Usually due to dehydration.
• Oxygen utilization during exercise: At rest, muscles use 21%. During activity, muscles use 88% of the body's blood oxygen.

Aerobic Training and Adaptations

• Aerobic training improves cardiac output and oxygen delivery.
• Leads to lower resting heart rate and blood pressure.
• Bradycardia (safe, slow heart rate) vs tachycardia (potentially risky, fast heart rate, especially in untrained individuals).

Cardiovascular Formulae

• Cardiac output (Q) formula: Q = HR (heart rate) x SV (stroke volume)
• VO2 max formula: VO2max = 15 * (HRmax / HRrest) with HRmax = 220 - age.

Respiratory System Basics

• Main functions: supply O₂, remove CO₂, regulate blood pH.
• External respiration (lung gas exchange) vs Internal respiration (tissue gas exchange).
• Conductive zone: transports air; respiratory zone: where gas exchange occurs.
• Breathing mechanism: inspiration (active diaphragm contraction) vs expiration (passive diaphragm relaxation).
• Diaphragm: accounts for 75%.

Diffusion & Gas Exchange

• Diffusion: Movement of gases from high to low pressure.
• Partial pressure of O₂ is affected by altitude.
  • Sea level PO₂ is approximately 159.1 mmHg.
  • PO₂ at 5,000 ft is approximately 132.3 mmHg.
• O₂ moves from alveoli to blood; CO₂ moves from blood to alveoli.

Oxygen Transport

• 98% of O₂ is carried by hemoglobin.
• 2% is dissolved in plasma.
• Hemoglobin saturation is around 95-100% at a PO₂ of 100 mmHg.

Pulmonary Ventilation

• VE (pulmonary ventilation): Volume of air breathed per minute.
• Rapid VE increase immediately after exercise onset.
• Steady-state phase: VE levels off during prolonged, moderate exercise.

Internal Respiration

• Increased PO₂ gradient during exercise helps muscle oxygen diffusion from the blood.

Acclimatization and Hypoxia

• Acclimatization at high altitudes leads to increased red blood cell production and oxygen efficiency.
• Types of hypoxia (low tissue oxygenation): hypoxic (low air O₂), anemic (low hemoglobin), circulatory (poor blood flow), histotoxic (cells cannot effectively use O₂).

Oxygen Consumption (VO₂) and Workload

• VO₂: Amount of oxygen used during activity – reflects aerobic fitness and efficient oxygen delivery/use.
• As workload increases, VO₂ increases to meet metabolic demands; greater for intense exercise.

VO₂ Max

• VO₂ max: Maximum oxygen consumption during intense exercise; A key measure of aerobic capacity and cardiovascular fitness.
• Calculated directly or estimated (e.g., heart rate formulas).
• Higher values indicate a robust cardiovascular system.

Athletic VO₂ Max

• Top athletes (cross-country, cycling, rowing) have higher VO₂ max values.

Sport-Specific VO₂ Max Variations

• Variations amongst hockey and football players are common due to different levels of required short burst and endurance.

Gender Differences in VO2 Max

• Males typically exhibit higher VO₂ max values due to differences in muscle mass, larger hearts and hemoglobin levels.

Data Limitations

• Lack of data for female athletes in some sports (such as certain hockey players) can limit knowledge and generalisations.

Test your knowledge on the journey of blood through the heart with this quiz. Explore how blood travels from the body to the lungs and back, and learn about heart size and muscle structure. Perfect for students studying human anatomy!