The Circulatory System

TheCirculatory

System

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Circulatory System The Circulatory System is

responsible for transporting materials throughout the entire body.

It transports nutrients, water, and oxygen to your billions of body cells and carries away wastes such as carbon dioxide that body cells produce.

It is an amazing highway that travels through your entire body connecting all your body cells.

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Components Heart Blood Vessels

Arteries Veins Capillaries

Heart

Blood

ArteriesVeins


Circulatory System


Which gases are transported to and from the body’s cells by the blood flowing in the circulatory system?

carbondioxide

oxygen

Oxygen is the gas needed for respiration and is transported to the body’s cells.


Circulatory System


The circulatory system carries two types of blood

Arrangement of the circulatory system means that these two types of blood do not mix.

Oxygen-rich blood

c

Oxygen-poor blood

Blood travelling to the body cells

High oxygen content

Low carbon dioxide content

Blood travelling away from the body cells

Low oxygen content

High carbon dioxide content


Circulatory System


The heart is the organ at the centre of the circulatory system. It pumps blood around the body.


Circulatory System


The inside of the heart is divided into two sections so that the two types of blood (oxygen-rich and oxygen-

poor) are kept apart

Oxygen-poor blood

Right sideof the heart

Oxygen-rich blood

Left sideof the heart


Circulatory System


The Heart: StructuresHeart coverings

Pericardium Covers the heart and large blood vessels

attached to the heart Visceral pericardium

Innermost layer Directly on the heart

Parietal pericardium Layer on top of the visceral pericardium


Pericardium Protective sac of

connective tissue Surrounds the heart Filled with fluid


The Heart: Structures


Heart walls: Epicardium

Outermost layer Fat to cushion heart

Myocardium Middle layer Primarily cardiac muscle

Endocardium Innermost layer Thin and smooth Stretches as the heart pumps




Myocardium The muscle of the heart

Strong and thick

Composed of spontaneously contracting cardiac muscle fibers

Can conduct electricity like nerves.

It’s blood supply comes from the coronary arteries.




The right and left sides of the heart are separated by a septum, or wall.

The septum prevents the mixing of oxygen rich and oxygen poor blood.

On each side of the septum are two chambers. The upper chamber (receives blood) is the atrium. The lower chamber (pumps blood out of heart) is

the ventricle.




Four chambers Two Atria

Upper chambers Left and right Separated by

interatrial septum

Two Ventricles Lower chambers Left and right Separated by

interventricular septum


Right Ventricle

Right Atrium

Left Ventricle

Left Atrium



The chambers of the heart have different functions:

blood tothe body

blood from the body

blood to the lungs

blood from the lungs

The Atria collect blood that enters the heart.

The ventricles pump blood out of the heart.




The valves between the atria and ventricles are connected to the inner walls of the heart by tough tendons.

valve open© iTutor. 2000-2013. All Rights Reserved



The tendons allow the valves to close and hold the valve flaps in place. They prevent the valves from flipping up and turning inside out

valve open valve closed© iTutor. 2000-2013. All Rights Reserved



A valve acts like a door that only opens in one direction.

If the door is held by someone at a fixed point, only the arm moves as the door opens and closes.

When the door is closed the arm is fully extended, so the door can only be opened in one direction.




A valve acts like a door that only opens in one direction.

In the heart, the tendons holding the valve are like the arm holding the door.

One end of each tendon is fixed to the wall of the heart and so the valve can only open in one direction.




How does the heart pump blood? The heart can pump blood because it is made of

muscle. Muscle tissue works by contracting (squeezing) and relaxing.



How does the heart pump blood?

All the parts of the heart on either side, work together in a repeated sequence.

The two atria contract and relax; then the two ventricles contract and relax.

This is how blood moves through the heart and is pumped to the lungs and the body.

One complete sequence of contraction and relaxation is called a heartbeat.



Blood Vessels As blood moves through

the circulatory system it moves through 3 types of blood vessels: Arteries: Carry blood

away from the heart . Capillaries: Link

arterioles to veins. Veins: Carry blood

towards the heart



Arteries Large vessels Carry blood from heart to tissues of body. Carry oxygen rich blood, with the exception of

pulmonary arteries. Thick walls-need to withstand pressure produced when

heart pushes blood into them.


Smallest blood vessels Walls are only one cell thick and very narrow. Important for bringing nutrients and oxygen to

tissues and absorbing CO2 and other waste

products.

Capillaries

Blood Vessels


Veins Once blood has passed through the capillary

systems it must be returned to the heart. Done by veins

Walls contains connective tissue and smooth muscle.

Largest veins contain one way valves that keep blood flowing toward heart.

Many found near skeletal muscles. When muscles contract, blood is forced through veins.




Blood Pressure The heart produces pressure

The force of blood on the wall of the arteries is known as blood pressure.

Blood pressure decreases as the heart relaxes, but the rest of the circulatory system is still under pressure.



Blood Pressure When blood pressure is taken, the cuff is

wrapped around the upper portion of the arm and pumped with air until blood flow in the artery is blocked.

As the pressure in the cuff is relaxed, 2 numbers are recorded. Systolic pressure- the first number taken, is the force

felt in the arteries when the ventricles contract.

Diastolic pressure- the second number taken, is the force of the blood on the arteries when the ventricles relax.



Blood What percent of your body is blood? How much blood do we contain?

On average 4-6 liters We contain about a pint of

blood for every 15 pounds of body weight

Composition of Blood: What percent of your blood is

cellular? What percent of your blood is

plasma?

8%

45%

55%



Blood Composed of plasma and blood cells Types of Cells are:

Red Blood Cells White Blood Cells Platelets


Plasma Straw colored 90% water 10% dissolved gases, salts, nutrients,

enzymes, hormones, wastes, and proteins.


Blood Plasma proteins

3 Types: Albumins, globulins and fibrinogen. Albumins and Globulins- transport substances such

as fatty acids, hormones and vitamins. Fibrinogen- Responsible for blood’s ability to clot


Red Blood Cells Most numerous type Transport oxygen Get color from hemoglobin Disk shaped Made in red bone marrow Circulate for 120 days


White Blood Cells Guard against infection, fight parasites, and attack

bacteria Number of WBC’s increases when body is fighting Lymphocytes produce antibodies which fight

pathogens and remember them

Blood


Platelets Aid the body in clotting Small fragments Stick to edges of broken blood cell and secrete

clotting factor to help form clot.


BloodBlood has 3 main

Functions Transport Protection Temperature

Regulation


Plasma

Red Blood Cells

Platelets

White Blood Cells


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The Circulatory System