Cardiovascular System and Blood Composition

Blood Flow and Oxygenation

• Oxygen from the lungs enters capillaries and merges into a blood vessel leading to the left side of the heart.
• This blood vessel is high in oxygen and low in carbon dioxide.
• The blood enters the left atrium.
• The blood vessel carrying blood from the lungs to the heart is the pulmonary vein.

Chambers and Vessels

• From the left atrium, blood flows to the left ventricle.
• Blood leaves the left ventricle through the aorta, the largest artery in the body.
• The aorta descends, branches off, and brings blood throughout the body.
• The aorta branches into capillaries, where oxygen diffuses out and carbon dioxide diffuses in.
• Capillaries merge to form veins, which carry blood back to the heart.

Pulmonary vs. Systemic Circulation

• Pulmonary circulation: Blood flow from the heart to the lungs and back to the heart.
• Systemic circulation: Blood flow from the left side of the heart to the entire body and back to the heart.
• The right side of the heart pumps blood low in oxygen to the lungs.
• The left side of the heart receives blood high in oxygen from the lungs and pumps it to the body.

Heart Valves

• The valve between the right atrium and right ventricle is the right atrioventricular valve.
• The valve between the left atrium and left ventricle is the left atrioventricular valve, also known as the bicuspid valve or mitral valve.
• Valves ensure blood flows in one direction and prevent backflow.
• When ventricles contract, valves prevent blood from flowing back into the atria.

Blood Pressure

• Pressure in systemic arteries is around 100 mmHg.
• Pressure in capillaries is around 30-40 mmHg (sometimes as low as 16 mmHg).
• Pressure in veins is around 10-20 mmHg.
• Low pressure in veins requires valves to prevent backflow, especially in the legs.
• Skeletal muscles help push blood through veins towards the heart.
• Standing at attention for too long can cause blood to pool in the legs, leading to fainting due to insufficient blood flow to the brain.

Four Chambers of the Heart

• The right side of the heart receives blood and pumps it to the lungs.
• The left side of the heart receives blood from the lungs and pumps it to the rest of the body.
• When the heart contracts, blood is ejected from the right ventricle to the lungs and from the left ventricle to the body simultaneously.

Resting Heart Rate

• Typical resting heart rate is between 60 and 80 beats per minute.
• To measure heart rate, count pulses for 15 seconds and multiply by 4.
• Fitness level affects resting heart rate; more fit individuals tend to have lower resting heart rates.

Maximum Heart Rate

• Maximum heart rate can be estimated using the formula: 220 - \text{age}.
• The heart must contract and relax to fill with blood; it cannot beat too rapidly.

Newborn Heart Rate

• Newborns have a higher heart rate (around 140 bpm) to fuel growth and compensate for greater heat loss.
• Newborns have a higher metabolic rate.

Blood Composition

• Spinning blood in a centrifuge separates it into cells (hematocrit) and plasma.
• Hematocrit: The percentage of blood that is cells.
• The cells in the blood are primarily red blood cells (erythrocytes) and white blood cells (leukocytes).
• Erythrocytes: Red blood cells, responsible for oxygen transport via hemoglobin.
• Leukocytes: White blood cells, immune cells that defend the body.
• Platelets: Cell fragments that aid in blood clotting.
• Red blood cells make up about 99.9\% of the blood cells.
• Plasma: Mostly water, contains nutrients, glucose, dissolved gases, amino acids, and hormones.
• Function: Transports Nutrients and waste that are soluble in it ex) amino acids, glucose, oxygen, and carbon dioxide.

Hemoglobin and Oxygen Transport

• Red blood cells transport oxygen bound to the protein hemoglobin.
• Sickle cell anemia: A disease where abnormal hemoglobin impairs oxygen binding and causes cells to become sticky.

Plasma Composition and Function

• Plasma is mostly water and contains dissolved nutrients, gases, and wastes.

Heart Attack

• A heart attack occurs when blood doesn't properly reach the heart muscle tissue.

Coronary Blood Vessels

• Coronary blood vessels supply blood to the heart muscle.
• If these vessels become clogged (atherosclerosis), the heart muscle cells die, leading to a heart attack.
• Heart muscle tissue that dies during a heart attack is replaced by scar tissue.
• Arteries: Take blood away from the heart.
• Veins: Bring blood to the heart.

Blood Pressure and Vessel Structure

• Arteries have thicker walls and more elastic tissue than veins.
• Arterial elasticity aids in expansion and recoiling during heartbeats.
• Veins have one-way valves to prevent backflow.

Capillaries

• Capillaries have thin walls (single layer of cells) for nutrient and waste exchange.
• Red blood cells pass through capillaries in single file.

Systemic and Pulmonary Circulation

• Pulmonary Circulation: Blood goes from the lungs where it becomes oxygenated then goes to the heart.
• Systemic Circulation: Blood circulates between the heart and the rest of the body.
• SA (Sinoatrial) node generates intrinsic heartbeat.
• SA node is located on the right atrium.

Heart Rate Control

• The heart can generate its own electrical signal via the SA node for heartbeat control.
• The heart rate is modulated by nerves that can either increase or decrease it.

Atherosclerosis and Stroke

• Atherosclerosis: Plaque buildup in blood vessels, damaging the tunica intima and leading to occlusion.
• A stroke is caused by a blood clot in the brain.
• A heart attack is caused by a clot in a coronary blood vessel.
• Stroke causes cell death in the brain tissue. Whereas a heart attack causes tissue death in heart tissue.