12.3 Circulatory System Disorders: Arteriosclerosis

UNIT 4 Chapter 12: The Circulatory System Section 12.3

• arteriosclerosis is a general term describing several conditions in which the walls of the arteries thicken and lose their elasticity• one type, called atherosclerosis, occurs when plaque (fats, calcium, and fibrous tissues) builds up inside arteries • as the artery narrows, blood pressure increases • may lead to angina (chest pain), blood clots, shortness of breath, heart attack, or heart failure• prevention includes a healthy lifestyle• treatments include aspirin, urokinase, and t-PA (for clots), angioplasty, and coronary bypass 

 

This ultrasound image shows where blood flow in an artery is normal (red) and slow (green). A build-up of plaque restricts bloodflow through the artery.

Aneurysm

UNIT 4 Chapter 12: The Circulatory System Section 12.3

• a bulge in an artery due to a weakened area of the arterial wall• blood pressure can cause the aneurysm to grow larger over time• if it bursts, internal bleeding can be fatal• most aneurisms occur in the aorta• treatments include surgery to remove the damaged portion and replacement with a patch or graft made of synthetic material

 

A coloured MRI scan shows ananeurysm (bulging) in one of the arteries of the neck. The scan was done to determine the cause of the patient’s dizziness.

Heart Valve DiseasesUNIT 4 Chapter 12: The Circulatory System Section 12.3

The following diseases affect the proper functioning of the heart valves:

• regurgitation: when a valve does not close completely and blood flows backward instead of forward • stenosis: when the valve opening becomes narrowed from thickening or scarring, inhibiting blood flow• mitral valve prolapse: when one or both of the biscuspid valve flaps bulges back into the atrium, preventing a tight seal

 

• causes include ageing, previous heart attack, or infection• surgeons may repair the valve or replace it with a human, animal, metal, plastic, or synthetic alternative

 

Arrhythmia

UNIT 4 Chapter 12: The Circulatory System Section 12.3

• a problem with the speed or rhythm of the heartbeat• can lead to insufficient blood flow to the brain or other organs• may be treated with medications or surgery to implant an artificial pacemaker

 

In a pacemaker, two lead wires with electrodes at their tips send the electrical signals from the pulse generator to the heart muscle. The electrical signals cause the heart muscle to contract or pump. Most pacemaker implantations are performed under local anesthesia.

Congenital Heart Defects

UNIT 4 Chapter 12: The Circulatory System Section 12.3

• present since birth; include problems in the walls dividing heart chambers, in valves, and in structure of heart blood vessels• surgeons can often successfully repair or reduce damage• diagnosed by CT or MRI scans

Stroke• an ischemic stroke occurs when a clot in a blood vessel blocks the flow of blood to the brain• a hemorrhagic stroke occurs when a blood vessel in the brain bursts and blood flows into the surrounding brain tissue• both kill brain cells and can lead to permanent damage• treatment must begin immediately to be effective; includes clot-busters, surgery, and non-surgical procedures

 

Disorders of the Blood: Anemia

UNIT 4 Chapter 12: The Circulatory System Section 12.3

• blood contains fewer than normal healthy red blood cells• can be caused by blood loss, or when the red blood cells do not contain enough hemoglobin to carry the body’s required amount of oxygen• symptoms include dizziness, fatigue, shortness of breath, headache, and cold extremities • treatments include dietary supplements

Hemophilia• an inherited disorder• blood is missing clotting proteins, such as factor VIII, so it does not clot properly• treatment includes factor VIII injections and lifestyle changes to avoid injury and possible continuous internal bleeding

 

Leukemia

UNIT 4 Chapter 12: The Circulatory System Section 12.3

• a cancer of the white blood cells• myeloid leukemia involves too many immature leukocytes that are not able to fight infection• lymphoid leukemia involves too many lymphocytes that are unable to perform their immunity role• both can be acute (and fatal) or chronic• treatments include blood transfusions, chemotherapy, or bone marrow transplant

 

(A) Normal blood cells. (B) Blood from a patient with leukemia. Notice the increased number of white blood cells (shown in purple).

Diagnosing DisordersMany diagnostic tests have been developed for the circulatory system and the heart:

 

 

 

UNIT 4 Chapter 12: The Circulatory System Section 12.3

• coronary angiography maps the coronary (heart) arteries• echocardiogram (ECHO) determines cause of a stroke and possible blood clots• exercise electrocardiogram determines the cause of chest pain, irregular heartbeats, dizziness, or fatigue• Holter monitor determines the possible cause of rhythm disturbances• event monitor determines the cause of a problem while symptoms are present• cardiac catheterization takes internal X rays of the heart to investigate problems

 

A Holter monitor is a portable recording device that continuously monitors heart activity.

Treating Circulatory Disorders: AngioplastyUNIT 4 Chapter 12: The Circulatory System Section 12.3

This is a treatment option for arteriosclerosis, in which a tube is inserted into a clogged artery and a tiny balloon inflates to force the artery open. Sometimes a wire-mesh tube called a vascular stent is inserted during the procedure to hold the vessel open.

  To widen a blood vessel blocked by plaque, surgeons insert a tube with a narrow balloon inside it. The balloon is inflated at the site of blockage to widen the vessel. After the balloon is removed, a permanent tube may be left in place the keep the vessel open.

Treating Circulatory Disorders: Coronary BypassUNIT 4 Chapter 12: The Circulatory System Section 12.3

During a bypass a section of healthy artery or vein from another part of the body (e.g., leg) is used to create a new pathway for blood to flow around a blockage.

Depending on the number of blockages, surgeons may perform a double, triple, or quadruple bypass.

 

A heart after a triple coronary bypass has been performed. Three healthy blood vessels have been attached to create new pathways for the blood to flow between the aorta and three arteries that are blocked.

Treating Circulatory Disorders: Organ Transplants

UNIT 4 Chapter 12: The Circulatory System Section 12.3

More than 1800 Canadians are waiting for an organ transplant, including lungs, liver, kidney, pancreas, corneas, stomach, heart valves, bone, skin, and heart. Many people die before a suitable organ is available.

 

A surgeon holds a human heartduring a heart transplant operation.

Treating Circulatory Disorders: Xenotransplants

UNIT 4 Chapter 12: The Circulatory System Section 12.3

One way to increase the supply of organs for transplant is to use non-human, yet compatible, species. This is called a xenotransplant, and the organ is called a graft.

 A key to success lies in the recipient’s body not rejecting the organ. Drugs have been developed to overcome this problem, however there are many health, safety, legal, ethical, and regulatory issues to consider. To date, there have been no clinical trials of xenotransplants in Canada.

 

Treating Circulatory Disorders: Artificial HeartsUNIT 4 Chapter 12: The Circulatory System Section 12.3

Artificial hearts can address some of the over-demand for heart transplants. A recent model, made of titanium and plastic, is powered by an external battery that can constantly and wirelessly recharge an internal battery.

 

This artificial heart is currently used as a temporary replacement for patients awaiting a human heart transplant due to acondition known as biventricular failure.

Treating Circulatory Disorders: Nanotechnology

UNIT 4 Chapter 12: The Circulatory System Section 12.3

Nanotechnology is the use of microscopic structures to detect changes in cells and molecules. Any molecule that points to the development of a disease is called a biomarker. For example, enzymes produced by cancer cells are different from those of healthy cells. A new drug therapy packages drugs in microcontainers (nanovalves) that deliver drugs only when they encounter the biomarker.

 

The nanovalve is a microscopic container—only 400 nanometres in diameter—that is easily taken up by cells. The cover remains in place when the body’s internal environment is at a neutral to acidic pH (left). In an internal environment with a basic pH, however, the forces holding the structure together are weakened. The cover separates and the drugs inside the container are released (right).

Section 12.3 Review

UNIT 4 Chapter 12: The Circulatory System Section 12.3