Cardiovascular System

Circulatory System The circulatory system includes the heart and all the blood vessels that circulate throughout the body.

Circulation is divided into two circuits: The pulmonary circuit carries blood between the lungs and the heart. The systemic circuit carries blood between the heart and the rest of the body.

Arteries carry blood away from the heart. Smaller lumen, thicker wall with more smooth muscle. Veins carry blood towards the heart. Larger lumen, thinner wall.

Veins have built-in valves to prevent blood from flowing back down, since they usually flow against gravity. Skeletal muscle will also “milk” or squeeze the veins to help the blood move up.

Capillaries are the smallest blood vessels, many only allow erythrocytes through single-file. Found anywhere oxygen and carbon dioxide are exchanged.

The heart provides the force that propels blood through the body. The heart is a double-pump. Each side beats separately: The right side (pulmonary) pumps blood to the lungs. The left side (systemic) pumps blood to the rest of the body.

Right Atrium Left Atrium Right Ventricle Left Ventricle Superior Vena Cava Inferior Vena Cava Aorta Pulmonary Trunk L. Pulmonary Artery R. Pulmonary Artery R. Pulmonary Veins L. Pulmonary Veins Coronary Artery

Aorta Right Pulmonary Artery Left Pulmonary Artery Superior Vena Cava Left Pulmonary Veins R. Pulmonary Veins Left Atrium Coronary Sinus Pulmonary Semilunar Valve Aortic Semilunar Valve Right Atrium Bicuspid Valve Tricuspid Valve Left Ventricle Right Ventricle Inferior Vena Cava

The heart has four valves that allow blood to move forward while preventing backflow.

The Pacemaker Cardiac muscle cells are able to contract in a regular pattern without any input from the brain. The sinoatrial node, also known as the pacemaker, creates an electrical impulse that spreads through the rest of the heart.

The impulse from the SA node stimulates the left and right atria to contract first. The atrioventricular node then receives the signal and passes it through the ventricles. The heart will naturally contract at a rate of 60-100 beats per minute.

Electrocardigrams Electrocardiograms, or ECGs, measure the electrical impulses coming from the heart, creating a graph of the output.

Reading an ECG Each change on the ECG is given a letter label and corresponds to a specific change in the heart. P wave: Atria contract. QRS wave: Ventricles contract. T wave: Ventricles relax and reset.

An arrhythmia is any irregular heartbeat pattern that does not follow the normal P-QRS-T pattern. Atrial fibrillation is a rapid and irregular heartbeat. Bradycardia is a heart rate that is too slow (below 60 beats/min at rest) Tachycardia is a heart rate that is too fast (above 100 beats/min at rest)

Blood Pressure Blood pressure is the force that blood exerts on the blood vessels. Systolic pressure is measured when the ventricles contract and push blood through the arteries. Diastolic pressure is when the ventricles relax and begin refilling. The normal blood pressure range is 120-140 / 80-90.

If a blockage occurs in a coronary artery, this causes a heart attack. Atherosclerosis a buildup of lipids, calcium, or cell debris that gradually restricts bloodflow. If a blockage occurs in a coronary artery, this causes a heart attack. The portion of the heart supplied by its blood will die.

Bypass A bypass involves transplanting a vein from another part of the body (usually the leg) onto the heart. Blood is re-routed around the blockage.

Angioplasty A narrow balloon is inserted into the blocked vessel. It is then inflated, expanding the vessel.

If the vessel does not stay expanded on its own, a mesh-like stent can be inserted to hold it open.

Fetal Circulation In an adult, blood flows from the right atrium to the right ventricle, then out to the lungs. In a fetus, the lungs are nonfunctional and can be bypassed. The foramen ovale is an opening that allows blood to move directly from the right to left atrium.

Fetal Circulation The fetus receives all of its oxygen and nutrients from the mother through the umbilical vein.

Fetal Circulation Carbon dioxide and other wastes produced by the fetus are returned to the mother through the umbilical artery.

Fetal Circulation Fetal blood has a much greater (+50%) concentration of hemoglobin with a higher affinity for oxygen than maternal blood. After birth, more blood flows into the pulmonary arteries and veins, increasing pressure in the left atrium. This forces the foramen ovale to permanently close.

Systemic Circulation Each time an artery or vein forms smaller branches, it is given a new name.

External Carotid Internal Carotid Common Carotid Subclavian Artery Brachiocephalic Artery Renal Artery Abdominal Aorta Common Iliac Internal Iliac External Iliac Artery Femoral Artery

Internal Jugular External Jugular Brachiocephalic Vein Subclavian Vein Superior Vena Cava Hepatic Vein Inferior Vena Cava Renal Vein Common Iliac Vein Internal Iliac Vein Femoral Vein

Circulatory Pathway in the Human Body Section 1 The Circulatory System Chapter 46 Circulatory Pathway in the Human Body

Chapter 46 Lymphatic System Section 1 The Circulatory System Chapter 46 Lymphatic System The circulatory system also includes the lymphatic system. The lymphatic system returns fluids that have collected in the tissues to the bloodstream. Excess fluid in the tissues, called lymph, moves into the tiny vessels of the lymphatic system by diffusion.

Lymphatic System, continued Section 1 The Circulatory System Chapter 46 Lymphatic System, continued Lymph vessels are similar to blood vessels but are also different in many ways. Lymph is filtered through small organs known as lymph nodes to trap tissue debris and other foreign particles. Lymph nodes also store lymphocytes, white blood cells that are specialized to fight disease.

Section 1 The Circulatory System Chapter 46 Lymphatic System