The Circulatory System (also called the cardiovascular system)

Objectives

• To be able to compare and contrast the three types of blood vessels

• To understand the function of valves in veins

• Many invertebrates don’t have a circulatory system

• Their cells are close enough to their environment for oxygen, wastes, nutrients, and other gases to simply diffuse into and out of their cells

• In many multi-cellular animals, especially land animals, this won’t work. Their cells are not close enough to the external environment for diffusion and osmosis to function quickly enough in exchanging needed gases

Closed Circulatory System

Components of the Circulatory System

• Heart

• Blood vessels

• Blood

Functions of the Cardiovascular System

• Picks up needed oxygen from the lungs and transports it to all the cells in the body

• Rids the body of the waste product, carbon dioxide, by delivering it to the lungs to be removed

• Helps keep the body healthy with its “germ- fighting” white blood cells

• Delivers nutrients from food to all body cells

Anatomy of the Heart

Four chambers of the heart

• The two upper chambers are the atria- they collect blood from incoming blood vessels and transfer it to the ventricles

• The two lower chambers, the ventricles are the pumping components of the heart; responsible for pumping blood to the lungs and to the rest of the body

Valves

• Valves prevent the back flow of blood in the veins

• They are also found in the heart and keep blood flowing from atria to the ventricles

• The “lub dub” sound you hear in the heart is caused by the opening and closing of the valves

HEART

The right side of the heart contains deoxygenated blood (blood low in oxygen and high in carbon dioxide (CO2)).

The left side of the heart contains oxygen rich blood.

The right side of the heart contains deoxygenated blood and the left side

contains oxygen rich blood

• You have about 100,000 km of blood vessels laid out in your body. Laid

end -to -end that is enough to circle Earth 2.5 times!

Arteries verses Veins

• Thicker walls than veins

• Blood carried here is under high pressure

• Usually carries blood away from the heart to the body cells

• Walls made three layers of smooth muscle

• Walls of veins thinner than arteries

• Blood carried here is under lower pressure

• Usually carries blood towards the heart

• Walls made of three layers of smooth muscle

• Most contain valves

Only Veins Have Valves, Arteries Do Not Have Valves

Valves prevent the backflow of blood

How Does Blood go from your legs to your heart?

• Contraction of skeletal muscles when you walk or run help push blood towards the heart

• One way valves help keep blood moving in one direction

• Breathing causes contraction of chest muscles which also squeeze blood forward

Capillaries

• These are the tiniest of the blood vessels

• They connect veins to arteries

• Their job is to distribute oxygenated blood coming from arteries to all body tissues, and then move deoxygenated blood from tissues to the veins (through diffusion)

Capillaries

• Walls of capillaries are made of flattened endothelial cells

• These cells are permeable, enabling substances to quickly diffuse through the capillary walls

• When the arteriole branches into the capillaries, the total cross- sectional area increases, slowing down blood flow, giving more time for the exchange of substances

Capillaries

• Capillaries are so narrow that many red blood cells travel single file through them!

• Each cell in the body is very close to a capillary- no further apart than the thickness of 4 sheets of paper.

• Most tissues have a rich supply of blood, but some are poorly vascularized, such as tendons and ligaments, and the cornea and lens in the eyes have no capillaries at all

• In places where activity is higher, there is a rich supply of capillaries: heart, digestion, bone, skeletal muscles, lungs, liver, brain, etc

Interesting Fact..

• Capillaries may be flooded with blood at times, or completely bypassed depending on the need of the body at that time. Here is an example:

• Between meals, when digestion isn’t taking place, blood bypasses most of the capillaries in the digestive tract

• After a meal, much of the blood is directed to the capillaries in the digestive tract in order to power digestion

• Why might it be a bad idea to engage in vigorous exercise just after eating a meal?

• The body may not have enough blood to supply both the digestive tract and the skeletal muscles, resulting in abdominal cramps

What is blood?

• Blood is a little thicker than water, has a little bit of a salty taste

• In the adult body there is about 10 pints of blood circulating around

• If you took a machine, called a centrifuge, and placed blood in it, you would see the layers of blood

• This machine spins things around, and the heavier parts sink to the bottom. Red blood cells are heaviest, plasma lightest

Composition of Blood

• Plasma- makes up 55% of total blood volume

• Red blood cells- make up 40% of total blood volume

• Platelets- make up 4% of total blood volume

• White blood cells-make up 1% of total blood volume

Composition of Blood

Amazing!

Plasma

• The liquid portion of the blood

• It is 90% water and contains nutrients, proteins, salts, hormones, and waste products

• Transports red blood cells and white blood cells through out the body

Red Blood Cells• Also called erythrocytes• They do not have a nucleus;

survive about 120 days • RBC’s are the only cells in

the body that lack mitochondria

• They have a characteristic flattened-disc shape, or donut shape

• They are soft and flexible• They contain an iron- rich

pigment called hemoglobin which binds very well to oxygen and gives red blood cells their color

• For this reason, RBC’s are the main transport system for oxygen in the blood

White Blood Cells

• Also called leukocytes• Tend to be larger than red

blood cells• They are colorless because

they lack hemoglobin• Their job is to fight infections

when microorganisms enter the body

• RBC’s, WBC’s, and platelets are produced in the bone marrow

• The body can produce more white blood cells in response to an infection

Platelets• Irregularly-shaped, colorless bodies that

have a sticky surface to stop bleeding

• Also called thrombocytes, they are the blood clotting agents in the blood

• Only survive about 9 days and are being constantly replaced by the bone marrow

How do Platelets Work?• When there is an injury, platelets sense

the presence of air and break apart

• They react with the presence of fibrinogen and form fibrin, a protein which resembles tiny threads

• The fibrin then forms a web-like mesh that traps in red blood cells

• This mesh of red blood cells hardens as it dries it, forming a clot, or a “scab”

Platelets rushing to the site of an injury

Fibrin forms a net that traps in red blood cells and helps stop bleeding.

• Vitamin K and calcium must be present in the blood for normal blood clotting- can bleed to death if missing from blood

• A bruise in an internal clot, a scab is an external clot- both lead to healing

• A clot in the artery sometimes occurs and can be serious- it can prevent the flow of blood, can result in a stroke or a heart attack

Tips for taking care of your heart…• Do not smoke, and avoid being around

second hand smoke• Eat less foods with saturated fat and

cholesterol • Eat low sodium foods• Engage in regular physical activity for 30

minutes everyday• Maintain a healthy weight• Maintain a blood pressure around or under

120/80• Keep total cholesterol under 200

Aerobic-Type Exercise Strengthen the Heart Muscle

Blood pressure

• Blood pressure is the force exerted on the walls of your blood vessels (artery) as blood flows through them

• Normal blood pressure is 120/80

• A reading of 140/90 is borderline hypertensive (high blood pressure)

• Blood pressure is measured by a device called a sphygmomanometer

• Your heart is a like pump. When it contracts, or beats, it sends a surge of blood through the blood vessels. This is called your systolic pressure

• When the heart relaxes between beats, your pressure decreases. This is called your diastolic pressure.

120 Systolic pressure (lub) load phase

___

80 Diastolic pressure (dub) reload

Hypertension (high blood pressure)• Hypertension is known as the “silent killer”

because it can creep up on people.• It adds to the workload of your heart and arteries

• The heart must work harder and the arteries

carry blood under higher pressure• If high blood pressure continues for a long time,

your heart and arteries may not work as well• Combined with obesity, high cholesterol,

diabetes, and smoking, the risk of heart attack or stroke increases dramatically

• Would you rather exercise 1 hour a day, or be dead 24 hours a day?

• Aerobic exercises, such as fast walking, running, soccer, biking, skating, and roller blading, are good for your heart!

Cholesterol

• Normal cholesterol levels should be under 200

• HDL-high density lipoproteins (good cholesterol)

• LDL- low density lipoproteins (bad cholesterol)

Cholesterol…not so bad

• Cholesterol occurs naturally in our bodies• It is manufactured normally by the liver• It helps keep the brain healthy• The liver uses cholesterol to make sex

hormones and the hormone, adrenaline• It also uses cholesterol to make bile• It is a main component of our cell membranes• Cholesterol is not bad unless we have too much

of it in our bodies

HDL and LDL in the Body

• Cholesterol can’t dissolve in blood so it is carried by lipoproteins

• When too much LDL cholesterol circulates the blood it can slowly build up in the walls of the arteries, leading to atherosclerosis

• HDL is thought to carry cholesterol back to the liver so that it may be passes from the body, thus protecting against heart attacks

Which type of foods contain cholesterol?

• Meats and dairy products

Diseases

Atherosclerosis

• A condition that leads to hardening of the inside walls of arteries (due to plaque)and can lead to coronary artery disease

• Plaque deposits build up inside the arteries; some normally as we age

• Plaque is made up mainly of fat cholesterol, and calcium

• Plaque build up begins in childhood and continues through life

Atherosclerosis

• Over time plaque build up leads to narrowing of the arteries which reduces the amount of blood and oxygen that reaches the heart muscle

• If it completely blocks the flow, can cause a heart attack

• It can also cause a blood clot, which also impedes blood flow to the heart

AngioplastyA treatment for atherosclerosis-here a thin catheter with a deflated balloon is inserted in the blocked vessel. Once inside it the balloon is inflated, crushing the plaque build up and opening up the pathway for blood flow.

Heart Failure Heart Attack

• Failure of the heart muscle to pump enough blood through the body

• As a result, some organs, such as the kidney, liver, and lungs may not get enough oxygen and nutrients

• A part of the heart muscle dies as a result of a blocked blood vessel that supplies the heart with blood

• Heart cells do not go through mitosis, so when they are lost they can not be replaced

Stroke-caused by a blocked blood vessel in the brain; afflicted area is deprived of oxygen and nutrients which

results in a variety of symptoms, like speech problems, or the inability to move an arm

Deep Vein Thrombosis (DVT)• DVT is a clot in the vein, usually in the

lower leg, or the thigh

• Sometimes they can break apart and move to the lungs

• This is called a pulmonary embolism, if the clot is large enough or if there are many,this can be life threatening

• Show students the animation (favorites)

Varicose Veins

• To return blood back to the heart, veins in your legs must work against gravity

• As you get older veins lose their elasticity, causing them to stretch

• The valves in your legs may become weak, allowing blood that should be moving towards your heart to flow backwords

• This results in pooling of the blood. It appears blue because it contains deoxygenated blood

Varicose Veins