Circulatory System

• The function of the circulatory system is to transport oxygen and nutrients throughout the body. It also carries away waste. 
• The circulatory system moves nutrients absorbed from the intestine to different parts of a body’s cells. 

Parts of the Circulatory System

• The main parts of the circulatory system are the heart, blood and blood vessels
• It is an organ system
• The heart pumps blood through arteries
• Arteries branch into smaller and smaller blood vessels. 
• The smallest blood vessels are called capillaries

• Inside the capillaries, many substances are exchanged between the blood and surrounding tissues. 
• After this exchange is done, blood flows through the larger blood vessels called veins which eventually return to the heart.

Heart

• The heart beats at a regular rate called your heart rate
• The frequency of your heart rate can change depending on physical activity, stress, temperature, your general health and other factors
• The outer and inner parts of the heart are covered with a smooth layer of epithelial tissue

• They reduce friction 
• Protects the heart from damage as the lungs constantly expand and contract
• The inner surface of the heart is lined with epithelial tissues to help blood flow freely. 
• If the inner lining hardens or roughens, it can lead to many health problems.

• The heart is composed of three different types of tissue: cardiac muscle tissue, nerve tissue, and connective tissue.

Cardiac muscle tissue

• They are a type of muscle that can only be found inside the heart
• Every part of the cardiac muscle tissue contract at the same time
• This causes the heart to contract and move blood around the body

Blood Flow

1. Veins bring deoxygenated blood to the right atrium  of the heart 
2. The right ventricle of the heart pumps this blood to the lungs to receive oxygen
3. Oxygenated blood returns to the left atrium  of the heart as it comes from the lungs
4. The left ventricle of the heart then pumps this oxygenated blood to rest of the body through the arteries

Blood

• Components of the blood: water 92%, dissolved protein 8%, glucose, amino acids, vitamins, minerals (mainly NaCl), urea, CO2, hormones, antibodies

Red Blood Cells 

• Nearly half of the blood’s volume is made up out of red blood cells
• Contains hemoglobin

• Hemoglobin transports oxygen throughout the body
• It is the reason why red blood cells appear red

White Blood Cells 

• Makes up less than 1% of the blood’s volume
• White blood cells recognize and destroy bacteria and viruses

• In other words, they fight infection

• They are the only type of blood cell to contain a nucleus

Platelets 

• Makes up less than 1% of the blood’s volume
• Responsible for making the blood clot

Plasma

• Makes up more than half of the blood’s volume
• It is a yellow protein-rich liquid
• They help carry blood cells all throughout the body

Blood Vessels

• There are 3 types of blood vessels in the circulatory system: arteries, veins, capillaries

Arteries 

• They are very thick vessels whose job is to carry blood away from the heart. 

Veins 

• Their job is to carry blood towards the heart. They are not as thick as arteries. 

Capillaries 

• They connect veins and arteries together
• They have very thin walls. 
• Capillaries allow substances to diffuse between the blood, other body fluids and tissues. Oxygen and nutrients diffuse from the blood into surrounding tissues. Carbon dioxide and other types of wastes pass from the body tissues into the blood to be carried away for disposal. 
• All parts of the body are provided with blood through a network of capillaries.

Diseases & Disorders of the Circulatory System

Coronary Artery Disease

• coronary arteries are blood vessels which provide blood to the heart muscle tissue
• They can become blocked with plaque (made up from fat, cholesterol, calcium, and other substances that typically circulate in the blood). 

• The plaque buildup can be caused by inherited genetic information or caused by an unhealthy lifestyle (high-fat diet, smoking,lack of exercise, bad oral hygiene). 

• Symptoms of coronary artery disease include tiredness, dizziness, pain/ burning sensation in the chest or arms.
• It can be diagnosed with an angiogram (a type of x-ray)

• In an angiogram, a fluorescent dye is injected into the bloodstream.

Heart Attack

• Should the coronary arteries be completely blocked by plaque or a blood clot, a heart attack may occur
• When this happens, heart muscle cells stop receiving the oxygen and nutrients they need to function, so the heart stops pumping and heart tissues start to die
• Symptoms of a heart attack include:

• chest pain or pressure
• shortness of breath
• nausea
• anxiety
• upper body pain
• abdominal or stomach pain
• sweating
• dizziness
• unusual fatigue

• Symptoms of a heart attack may differ in men and women
• Any suspicion of a heart attack requires immediate medical attention
• Heart attacks can be diagnosed with a blood test and an electrocardiogram (ECG)

• Blood tests help identify proteins that only appear when cardiac muscle tissues die
• An electrocardiogram (or ECG) measures electrical activity pattern in the heart’s beat cycle

• Electrical signals in damaged heart muscles differ from those in healthy heart muscles