Cardiovascular and Vascular Systems

The Cardiovascular System

• The heart is a four-chambered, hollow, and muscular organ, slightly larger than a man's fist.
• The heart is surrounded by the pericardium, a thin fluid-filled sac with three distinct layers.
• The two sides of the heart are right and left, each with two chambers: an upper and a lower.
• Atrioventricular (AV) valves are located at the entrance to the ventricles.
• The left AV valve is also called the mitral valve.
• The right AV valve is also called the tricuspid valve.
• Septa are the partitions that separate the right and left heart chambers.

The Vascular System

• The vascular system is a major component of the circulatory system.
• The vascular system is vital for phlebotomists, as they need to access it for blood sample collection for lab testing.
• The system of blood vessels, along with the heart, forms a closed loop for circulating blood to all body parts.
• Pulmonary and systemic circulation are the two divisions of the vascular system.

Pulmonary Circulation

• It carries blood from the right ventricle of the heart to the lungs.
• Carbon dioxide is removed and oxygen is picked up in the lungs during pulmonary circulation.
• Oxygenated blood is returned to the left atrium of the heart.

Systemic Circulation

• Systemic circulation serves the rest of the body.
• Oxygenated blood and nutrients are carried from the left ventricle of the heart to the body cells.
• Blood carrying carbon dioxide and waste products of metabolism is returned to the right atrium of the heart.

Arteries

• Arteries are blood vessels that carry blood away from the heart.
• Arteries have thick walls due to the high pressure from the contraction of the ventricles.
• The pressure in arteries creates a pulse that can be felt which distinguishes arteries from veins.
• Most arteries are part of the systemic circulation which carries oxygenated blood away from the heart to the tissues.
• Normal systemic arterial blood appears bright red because of its high oxygen content.

Veins

• Veins are blood vessels that return blood to the heart.
• Most veins belong to the systemic circulation and carry deoxygenated blood from the tissues back to the right atrium.
• The blood in veins is darker and more bluish than arterial blood due to low oxygen content.
• Vein walls are thinner than artery walls because the blood is under less pressure.
• Skeletal muscle movement, one-way valves, and pressure changes in the abdominal and thoracic cavities keep blood moving through veins.

Capillaries

• Capillaries are microscopic, one-cell-thick vessels that connect arterioles and venules.
• These vessels form a bridge between arterial and venous circulation, transporting blood from arterioles to venules.
• Blood within capillaries is a mixture of both venous and arterial blood.
• In systemic circulation, arterial blood in capillaries delivers oxygen and nutrients.
• The thin walls of capillaries enable the exchange of gases and nutrients between the blood and cells.

Layers of Blood Vessels

Tunica Adventitia/Externa

• This is the outer layer of a blood vessel.
• The tunica adventitia is made of connective tissue.
• This layer is thicker in arteries than in veins.

Tunica Media

• This is the middle and thickest layer of a blood vessel.
• The tunica media consists of smooth muscle tissue and some elastic fibers.
• It is thicker in arteries than it is in veins.

Tunica Intima/Interna

• This is the inner layer or lining of a blood vessel.
• The tunica intima consists of a single layer of endothelial cells.
• An underlying basement membrane, connective tissue, and an elastic internal membrane form this layer.

Antecubital Fossa

• This is the shallow, triangular depression in the arm, anterior to and slightly below the elbow's bend.
• The antecubital fossa is the first-choice location for venipuncture due to its location.
• The arrangement of antecubital (AC) veins can vary from individual to individual.
• There are two basic vein distribution arrangements characterized as “H-shaped” and “M-shaped”.

H-Pattern Antecubital Veins

Median Cubital Vein

• The vein in the center of the antecubital area, ideal choice, is the vein for venipuncture in the H-shaped pattern.
• This vein is usually larger, closer to the surface, and well-anchored as well as less painful and less likely to bruise.

Cephalic Vein

• This vein is in the lateral aspect of the antecubital area, and it is the second-choice vein for venipuncture in the H-shaped pattern.
• It is often more difficult to palpate than the median cubital vein , but it is fairly well anchored and the only vein that can be palpated by obese patients.

Basilic Vein

• This vein is located on the inner side of the antecubital area.
• The basilic vein is considered the last-choice vein for venipuncture in either venous distribution pattern.
• It is easy to palpate but not well anchored, increasing the risk of puncturing major arm nerves, and can be more painful with increased risk of bruising.

M-Pattern Antecubital Veins

Median Vein (aka Intermediate Antebrachial Vein)

• This vein is in the center of the antecubital area, and the first choice for venipuncture in the M-shaped pattern because it is well anchored.
• It is generally the safest vein to use as it tends to be less painful and not as close to major nerves or arteries.

Median Cephalic Vein (aka Intermediate Cephalic Vein)

• This vein is located in the lateral aspect of the antecubital area, and is the second choice for venipuncture in the M-shaped pattern due to how accessible it is in relation to major nerves and arteries
• It is also less likely to roll and puncture wounds are less likely to be painful.
• This vein should not be chosen unless median or median cubital veins of both arms have been ruled out.

Median Basilic Vein (aka Intermediate Basilic Vein)

• This vein is located in the medial aspect of the antecubital area, and is the last choice for venipuncture in the M-shaped pattern.
• This vein is located near the median nerve and the anterior and posterior branches of the medial cutaneous nerve and the brachial artery more likely to be painful to puncture and also like the basilic vein.

Dorsal Forearm, Hand, and Wrist Veins

• The larger and fuller antecubital veins are used most frequently.
• Veins on the back of the hand and wrist are also acceptable for venipuncture.
• Veins on the lateral wrist, above the thumb to the mid-forearm should not be used because a nerve injury could occur.

Leg, Ankle, and Foot Veins

• Leg, ankle, and foot veins must not be used for venipuncture without documented permission from the patient's physician due to potential medical complications like phlebitis or thrombosis.
• Puncture of the femoral vein is performed only by physicians or specially trained personnel.

Definitions

• Aneurysm is the localized dilation or bulging in the wall of a blood vessel, usually an artery.
• Arteriosclerosis is the thickening, hardening, and loss of elasticity of artery walls.
• Atherosclerosis is a form of arteriosclerosis.
• Atherosclerosis involves thickening of the intima of the artery due to plaque buildup.
• Disseminated Intravascular Coagulation (DIC) is pathological widespread clotting and fibrinolysis.
• Bleeding may occur due to DIC, in which coagulation factors are consumed.

Lymphatic System

• The lymphatic system is a network of organs, vessels, ducts, and nodes.
• Lymph vessels extend throughout the entire body, much like blood vessels.
• Tissue fluid is returned to the bloodstream via the lymphatic system.
• The lymphatic system protects the body from microorganisms and impurities, processing lymphocytes and delivering fats from the small intestine to the bloodstream.
• Lymph, vessels, and lymph nodes make up the lymphatic system.
• Lymph nodes can remove impurities and process lymphocytes.

Definitions Related to the Lymphatic System

• Hodgkin Disease is a chronic, malignant disorder common in males, characterized by enlarged lymph nodes
• Lymphadenopathy is a disease of the lymph nodes.
• Node enlargement is often seen in lymphadenopathy, for example as seen in mononucleosis.
• Infectious Mononucleosis is caused by the Epstein-Barr virus (EBV).
• Splenomegaly is spleen enlargement.