Wednesday, September 18, 2013

Cardiovascular System



Cardiovascular system

The cardiovascular system contains the Heart, Blood vessels and blood. There is approximately 5 liters of blood that courses through these blood vessels as it’s pumped by the Heart. The cardiovascular system transports nutrients, oxygen, cellular waste products and hormones to the rest of the body. The heart pumps blood throughout the body every minute.

The Heart

The heart is a fist sized organ located in the thoracic region. The great blood vessels (aorta, pulmonary trunk, vena cava and pulmonary veins) are connected at the top of the heart.




















There are two circulatory loops, the systemic circulatory loop and the pulmonary  circulatory loop.


The systemic loop carries oxygenated blood from the left side of the heart to the body tissues and organs (except to the heart and lungs) and returns deoxygenated blood to the right side of the heart. The systemic circulatory loop also gets rid of waste from body tissues.


The pulmonary circulation loop carries deoxygenated oxygen from the right side of the heart to the lungs where it picks up oxygen and returns it to the left side of the heart.


The heart contains four chambers: right atrium, right ventricle, left atrium, left ventricle.

Blood vessels






Blood vessels are the blood ‘highways’ of our body. The size of the vessel corresponds to the quantity of blood that goes through (arteries are thick and capillaries thin). The hollow portion of the blood vessel through which blood passes is called the lumen. Blood vessels are lined with a thin layer of epithelium known as endothelium. the endothelium prevents blood clots and protects blood cells.

There are three types of blood vessels: arteries, veins and capillaries. Blood vessels are usually named according to the region they carry blood or nearby body structures.

Arteries- They carry blood away from the heart. All arteries except the pulmonary trunk and arteries of the pulmonary circulation loop carry highly oxygenated blood to tall parts of the body. Due to the pressure of blood going through arteries they are usually thick walled, muscular and elastic.

      Arterioles are small arteries that branch off from the main arteries and carry blood to            capillaries.

Capillaries- They are the smallest, thinnest and most common vessels in the body. Capillaries connect to arterioles on one end and to venules on the other. Capillaries help in the exchange of gases, nutrients and waste products. The endothelium of the capillaries is very thin , it acts as a filter to allow for gases, liquids and nutrients to go through while keeping the blood cells inside the capillaries.

Veins- they carry deoxygenated blood to the heart. They usually undergo low blood pressure and their walls are therefore thin, less elastic and less muscular. Since veins do not rely on the heart to pump blood back, they rely on gravity, inertia and skeletal muscle contractions to help in blood flow. Vein contain one-way valves to prevent the blood from flowing away from the heart.

Venules are like arterioles but connect to veins.



Coronary Circulation

The heart has blood vessels that provide the myocardium with oxygen and nutrients. The left and right coronary arteries provide blood to the left and right sides of the heart. The coronary sinus is a vein that returns deoxygenated blood from the myocardium to the vena cava


Hepatic Portal Circulation

The hepatic portal vein carries blood from the stomach and small intestines to the liver. The liver removes toxins, stores sugars and processes the products of digestion before they reach other body tissues. Blood from the liver then returns to the heart through the Vena Cava.


Blood

The body carries about 5 liters of blood. Blood carries nutrients, wast and gases throughout the body. Blood is made up of red blood cells, white blood cells, platelets,  and liquid plasma.

Red blood cells- They make up 45% of blood volume. Red blood cells are produced in the red bone marrow. About 2 million are produced every second! Red blood cells look like a concave disk. This shape gives them a high surface are and helps them squeeze through the capillaries. The high surface area to volume ratio allows oxygen to be easily transferred into and out of the cells. Red bloods cells contain no DNA and are unable to repair themselves.

      Red blood cells transport oxygen throughout the body through the red pigment hemoglobin. Hemoglobin contains iron and proteins.

White blood cells- white blood cells make a small percentage of blood. They help with immunity. There are two classes of white blood cells: granular leukocytes and agranular leukocytes.

Granular leukocytes-  There are three types: neutrophils, eosinophils, and basophils. Neutrophils contain digestive enzymes that neutralize bacteria. Eosinophils contain digestive enzymes for digesting viruses that have been bound to by antibodies in the blood. Basophils release histamine to intensify allergic reactions and help protect the body from parasites.

2.  Agranular Leukocytes- There are two types: lymphocytes and monocytes. Lymphocytes include T cells and natural killer cells that fight off viral infections and B cells that produce antibodies against infections by pathogens. Monocytes develop into cells called macrophages . They ingest pathogens and the dead cells from wounds or infections.

Platelets- They are responsible for clotting. Platelets form in the red bone marrow. They have a short lifespan, usually about a week.

Plasma-  This is the liquid part of the blood. It contains water, proteins and dissolved substances. Plasma makes about 55% of the blood volume. The proteins in the plasma include antibodies and albumin. O dissolved in the plasma, including her substances dissolved in plasma include:  oxygen, carbon dioxide, electrolytes, nutrients, and cellular waste products. The plasma functions as a transportation medium for these substances.


Functions of the cardiovascular System

The cardiovascular system has three functions:  transportation, regulation and protection.

Transportation- It transports blood throughout the body. The blood transports nutrients, hormones and oxygen and removes waste materials and carbon dioxide to be processed or removed from the body.

Protection- The cardiovascular system protects the body through its white blood cells. The platelets and red blood cells create protection against outside infection by creating scabs. Blood lso carries antibodies that provide immunity.

Regulation- Blood vessels help maintain a stable body temperature by controlling the blood flow to the surface of the skin. Blood also helps maintain the body’s pH. The albumins in the blood help balance the osmotic concentration of the body’s cells.


Cardiovascular conditions/Diseases

Coronary artery disease ( also known as coronary heart disease and ischaemic heart disease)- Coronary artery disease (CAD) is the most common type of heart disease and cause of heart attacks. CAD is caused by plaque building up along the inner walls of the arteries of the heart, which narrows the arteries and reduces blood flow to the heart.

Signs and symptoms:

Chest pain
Decreased exercise tolerance
Heartburn
Difficulty in breathing
Swelling of the extremities

Risks:

Smoking
Lack of exercise
Hypertension
Hyperglycemia
Genetics
Alcohol consumption
Stress
Age (men over 60, women over 65)
Obesity
Diet rich in saturated fats, low in antioxidants
Low hemoglobin

Diagnosis:

EKG
Stress test
Coronary angiography
Intravascular ultrasound
MRI




Treatment:

Medical treatment - drugs (e.g. cholesterol lowering medications, beta-blockers, nitroglycerin, calcium antagonists, etc.);
Coronary interventions- angioplasty and coronary stent-implantation;
Coronary artery bypass grafting (CABG - coronary artery bypass surgery).
Stem cell therapy
Angiogenesis

Cardiomyopathy - is the deterioration of the function of the myocardium (the heart muscle), usually leading to heart failure

Signs and Symptoms:

Breathlessness
Swelling of the legs
Irregular heartbeat
Chest pain

Treatment:

Medications
Pacemaker
Defibrillators
Ventricular assist devices

Hypertensive heart disease - diseases of the heart secondary to high blood pressure

Signs and symptoms:

Fatigue
Irregular pulse or palpitations
Swelling of feet and ankles
Weight gain
Nausea
Shortness of breath
Difficulty sleeping flat in bed (orthopnea)
Bloating and abdominal pain
Greater need to urinate at night

An enlarged heart (cardiomegaly)

Heart failure
Cor pulmonale - a failure at the right side of the heart with respiratory system involvement
Cardiac dysrhythmias - abnormalities of heart rhythm
Inflammatory heart disease
Endocarditis – inflammation of the inner layer of the heart, the endocardium. The structures most commonly involved are the heart valves.
Inflammatory cardiomegaly
Myocarditis – inflammation of the myocardium, the muscular part of the heart.
Valvular heart disease
Cerebrovascular disease - disease of blood vessels that supplies to the brain such as stroke
Peripheral arterial disease - disease of blood vessels that supplies to the arms and legs
Congenital heart disease - heart structure malformations existing at birth
Rheumatic heart disease - heart muscles and valves damage due to rheumatic fever caused by streptococcal bacteria infections