Cardiovascular System Notes

Cardiovascular System

Functions

• Transport of gases: Oxygen (O2) and Carbon Dioxide (CO2).
• Distribution of nutrients.
• Transport of toxins and cell waste.
• Distribution of hormones.
• Regulation of body temperature.
• Defense against infections via specialized cells.
• Blood clot formation to repair broken blood vessels.
• Pumping blood to the lungs and the rest of the body.

Three Main Components

• Heart
• Blood
• Blood vessels: Veins, arteries, capillaries.

Blood Vessels

Arteries

• Carry blood away from the heart.
• Do not have valves because the pressure in arteries is higher than in veins.
• Thick-walled vessels.
• The largest artery is the aorta.

Veins

• Carry blood toward the heart.
• Have valves to prevent backflow due to lower pressure compared to arteries.
• The largest vein is the vena cava.

Capillaries

• Smallest type of blood vessel (microscopic).
• Permit exchange of materials with body tissues via diffusion.
• Composed of a single layer of cells where gas exchange happens.

Function of Blood Vessels

• Circulate blood throughout the body.
• Help keep blood flowing to and from the heart.

Vessel Structure

• Artery: Endothelium, smooth muscle, connective tissue.
• Vein: Endothelium, smooth muscle, connective tissue.
• Capillary: Endothelium.
• Red blood cells must pass through capillaries in single file.
• Capillary walls are thin and permeable to gases, nutrients, and cellular wastes.

Blood Flow in Veins

• The heart’s original pushing force has less effect on blood movement in the veins.
• Veins are located near skeletal muscles; contraction of these muscles assists in blood movement.

Human Heart Anatomy

• Right side receives deoxygenated blood from the body and pumps it to the lungs for oxygenation.
• Left side receives oxygenated blood from the lungs and pumps it to the body.

Key Structures

• Superior vena cava
• Inferior vena cava
• Right atrium
• Tricuspid valve
• Chordae tendineae
• Papillary muscles
• Right ventricle
• Trabeculae carneae
• Pulmonary semilunar valve
• Pulmonary artery
• Pulmonary trunk
• Left atrium
• Bicuspid (mitral) valve
• Aortic semilunar valve
• Left ventricle
• Interventricular septum
• Aorta
• Brachiocephalic trunk
• Left common carotid artery
• Left subclavian artery
• Ligamentum arteriosum
• Fossa ovalis
• Endocardium
• Myocardium
• Epicardium

Human Circulation

• Flow of fluids occurs through two routes:
  • Pulmonary circuit
  • Systemic circuit

Pulmonary Circuit

• Directs blood from the heart through the lungs for gas exchange (CO2 exchanged for O2) and back to the heart.

Systemic Circuit

• Carries blood between the heart and the rest of the body, where gas exchange (O2 exchanged for CO2) occurs.

Double Circulation

• An important circulatory adaptation in terrestrial vertebrates, creating two separate circuits of blood.

Human Heart Chambers

• Four chambers:
  • Two atria (superior): right atrium, left atrium.
  • Two ventricles (inferior): right ventricle, left ventricle.

Human Heart Valves

Purpose

• Prevent backflow of blood.

Types

• Two atrioventricular (AV) valves: Left and right AV valves.
• Two semilunar valves: Aortic valve, pulmonary valve.

Valve Function

• Atrioventricular valves allow blood flow from the atria into the ventricles and prevent backflow into the atria when the ventricles contract.
• Semilunar valves allow blood to enter the pulmonary artery and aorta during ventricular contraction and prevent backflow as the ventricles relax.

Blood Flow Through the Heart

• The four-chambered heart acts like two hearts beating as one, with completely isolated right and left atria and ventricles.

Right Heart

• Deals with oxygen-poor blood.
• The right atrium receives oxygen-depleted blood from the body via the superior and inferior vena cava.
• The right atrium contracts, forcing blood into the right ventricle.
• Contraction of the right ventricle sends oxygen-poor blood to the lungs through the pulmonary arteries.

Left Heart

• Deals with oxygenated blood.
• Oxygen-rich blood from the lungs enters the left atrium through the pulmonary veins and is squeezed into the left ventricle.
• A strong contraction of the left ventricle sends oxygenated blood through the aorta to the rest of the body.

Pulmonary Circuit

• Flow of blood from the heart to the lungs and back.
• Pulmonary arteries carry blood with CO_2 from the right side of the heart to the lungs.
• Gas exchange happens within the lungs.
• Pulmonary veins return blood with O_2 to the heart.

Systemic Circuit

• Flow of blood from the heart to the body and back.
• The heart pumps blood with O_2 into the aorta.
• Gas exchange occurs in body tissues.
• Blood with CO_2 from tissues returns to the heart through the superior and inferior vena cavae.

Cardiac Cycle (Heartbeat)

• Describes the series of events during a complete heartbeat: the contraction and relaxation of the atria and ventricles (0.8 seconds).
• Atria and ventricles alternately contract and relax.

Events

1. The two atria contract simultaneously (atrial systole).
2. Then the two ventricles contract simultaneously (ventricular systole).
3. All chambers then relax (diastole).

Systole

• Moment when the atria and ventricles contract, moving blood forward.

Diastole

• Moment when all chambers relax, filling up the heart with blood.
• The human heart beats about 100,000 times each day.

Detailed Cycle

1. Diastole: Relaxation, blood returning to the heart from the body and lungs.
2. The AV valves are open.
3. Blood passively flows by gravity into the ventricles.

• In a typical resting person, the complete cycle occurs in just under 1 second, or about 70 times per minute.

Atrial Systole

• The two atria contract in synchrony, emptying their contents into the ventricles.

Ventricular Systole

• The two ventricles contract simultaneously, forcing blood into arteries that exit the heart.

Heart Rate

• The number of cardiac cycles (heartbeats) per minute.

Cardiac Cycle Phases

1. Atrial systole: Both atria contract, forcing blood into the ventricles (0.1 sec).
2. Ventricular systole: Both ventricles contract, forcing blood through the pulmonary and systemic circuits. Systolic pressure is measured here (0.3 sec).
3. Diastole: The heart relaxes, ending the cycle. Blood fills both atria and begins to flow passively into the ventricles. Diastolic pressure is measured here (0.4 sec).

Blood Pressure

Systolic Blood Pressure

• Pressure in arteries when the heart beats (heart is contracting).
• The higher of the two measurements.
• Generated in the arteries by the muscular left ventricle as it pumps blood through the systemic circuit.

Diastolic Blood Pressure

• Pressure in arteries when the heart is being filled with blood (heart is relaxing).
• The lower of the two measurements.
• The pressure in the arteries as the heart rests between contractions.

Blood

Blood Components

• 55% Plasma
• 1% White Blood Cells and Platelets (for the immune system)
• 44% Red Blood Cells (for O_2 transport)

Plasma

• 90% water.
• Clear, pale-yellow fluid.
• Has more than 100 different types of molecules dissolved in it.
• Transports proteins, hormones, nutrients, and cellular wastes.
• Contains a variety of ions; some maintain blood pH, while others are crucial for nerve and muscle cell functioning.

Cell Origin

• All three cell-based components of blood—red blood cells, white blood cells, and platelets—originate from cells that reside in bone marrow, a tissue within the cavities of bones.

Cardiovascular System Disorders

Atherosclerosis

• Narrowing of the arteries due to the buildup of plaque.
• Two types of cholesterol:
  • HDL – “good” cholesterol
  • LDL – “bad” cholesterol
• If LDL > HDL, lipid deposition can occur.
• Lipids can be oxidized due to O_2 in blood.
• Oxidized lipids can calcify, forming plaque.
• Lipid deposition: when lipids accumulate in the walls of a blood vessel.
• Calcification: the accumulation of calcium salts in a body tissue.
• Plaque: a flat, often raised, patch on the skin or other organ, as on the inner lining of arterial walls in atherosclerosis

Angioplasty and Stenting

• Balloon angioplasty and the placement of a stent. After a balloon-like device is inflated in an artery to open it and flatten the plaque, a tube of metal (the stent) is inserted and left in place to keep the artery open.

Coronary Artery Disease

• Type of atherosclerosis that happens in the arteries that supply blood to the heart (coronary arteries).
• The aorta connects with the coronary arteries to give blood with O_2 to the cardiac muscle.

Coronary Bypass Surgery

• Veins from another part of the body are used to divert blood past the blockages.

Hypertension (“High Blood Pressure”)

• The blood pushing against the artery walls is consistently too high.
• Risk factors:
  • Family history
  • Atherosclerosis
  • Smoking/alcoholism
  • High sodium diet
  • Obesity
• Complications:
  • Stroke
  • Heart/kidney failure
  • Vision loss

Blood Pressure Values

• Normal: Less than 120 mmHg (systolic) and less than 80 mmHg (diastolic).
• Hypertension: 130 mmHg or more (systolic) or 80 mmHg or more (diastolic).