The Circulatory System

Part One – BloodPart Two – Circulatory System

Part One - BloodAt the end of this section you should be able to:Identify the liquid and formed elements of blood.Identify their functions.Identify different blood types and their compatibility.

What we have learned so far… Nutrients enter the bloodstream after

they have been absorbed by the small intestine.

Oxygen enters the bloodstream through the alveoli.

Together, these elements travel through the blood to enter our bodies trillions of cells so as to nourish them and to allow energy to be created.

Later, we will learn how waste products leave our bodies.

Blood Blood is an incompressible fluid

flowing through our bodies. It flows everywhere.

Its main function is the transportation of nutrients and gases from their point of entry to their destination, and vice versa. Nutrients from the digestive system. Oxygen from the respiratory system. Waste made from cellular respiration.

Characteristics of Blood Blood is red, not blue as you may think

from looking at your veins. Salty Viscous, (thick) Odourless

Males have 5-6 litres of blood. Females have 4-5 litres of blood.

Components of Blood Blood may seem homogenous, but is

composed of formed elements called blood cells, (white and red), and platelets.

Plasma is what makes it liquid. The formed elements and the plasma

can be separated through a process called centrifugation.

45% - formed elements, 55% plasma.

Plasma

Formed elements

Components of Blood

Liquid Element Plasma

Formed Elements Red blood cells,

(RBC) White blood cells,

(WBC) Platelets

Red Blood Cell

Platelet

White Blood Cell

Liquid Element - Plasma Description:

Yellowish liquid, composed of 90% water. Many substances become dissolved in the plasma as they’re being transported, like nutrients, hormones and waste.

Functions: Transportation of nutrients to cells. Transportation of waste from cellular

respiration to excretory organs. Transportation of hormones, antibodies,

etc.

Formed Elements – RBC’s Description:

There are 4-6 billion RBC’s in your body. Red-coloured cells. They are concave,

(donut-shaped). Functions:

Transportation of oxygen using a protein called hemoglobin.

Transportation of carbon dioxide. Blood carrying oxygen is bright red.

Blood carrying carbon dioxide is dark red.

Formed Elements – WBC’s Description:

There are 4-11 billion WBC’s in the body. They are transparent.

Functions: Provide immunity and defense against

disease. This is why the numbers vary. Someone who is very ill will have a lower count of WBC’s than someone who is healthy.

Phagocytosis: surround and destroy foreign substances.

Formed Elements - Platelets Description:

There are 150-400 million platelets in your body.

They are irregular fragments coming from large cells in bone marrow.

Function: Coagulation or blood-clotting. This

process allows your skin to scab and heal.

Blood Types There are 4 main blood types: A, B, AB and O Blood types are first categorized by the

presence or absence of two substances. Substance A Substance B Found on the membrane of

RBC

In addition, cells can carry another substance on their membrane: Rhesus Factor, or RH Factor. Blood types can be either RH positive or RH

negative.

Blood Type A+ A- B+ B- AB+ AB- O+ O-

Substance A

No substances present

Substance B

RH Factor

Blood Transfusions An injection or transfer of blood to a

person who has undergone an accident, surgery or has a disorder which requires it.

A transfusion requires a donor and a recipient. But, because people have different blood types, the process must be done with care.

Before blood typing was discovered in 1902, many people died as a result of blood transfusions.

… Donation is possible between two

people with the same blood type. But some types are rarer than others.

Some blood types are compatible with others.

The rule of thumb for blood donation: Don’t give what they don’t already have.

Consider the substances in blood, A and B, and the RH factor.

DONOR

RECIPIENT

O- O+ B- B+ A- A+ AB- AB+

AB+

AB-

A+

A-

B+

B-

O+

O-

Blood Compatibility Two people are blood compatible when:

They are both of he same blood type. Type O- blood can donate to anyone,

regardless of blood type because they have no substances, nor RH factor. Universal donor.

Type AB+ blood can receive blood from anyone because they have both substances and RH factor. Universal recipient.

Part Two – Circulatory SystemAt the end of this section you should be able to:Name the parts of the circulatory system, (heart, vessels).Explain the role of the circulatory systemDescribe the function of the main parts, (heart vessels).

Anatomy of the Circulatory System There are three main parts of the

circulatory system: The heart Blood vessels Pulmonary and systemic circulation

The heart is the pump that keeps blood circulating in our blood vessels.

The blood vessels are broken down into many types, mainly depending on their size.

There are two ways that blood circulates throughout the body.

Blood Vessels The bodies blood vessels form a closed-

circuit network. Blood vessels are divided into three

categories: Arteries Capillaries Veins

Arteries A blood vessel that

carries blood from the heart to other parts of the body.

They have very thick walls, allowing them to withstand high amounts of pressure.

They branch into smaller arterioles, before becoming small capillaries.

Capillaries A blood vessel that

has a small diameter and thin walls. Responsible for exchanges between the blood and cells.

Capillaries are so small that the blood cells must pass one at a time.

Veins A blood vessel that carries blood back

to the heart. Once capillaries start to reconnect, they

form venules, which become the larger veins.

The Heart The heart is roughly the size of your fist,

located between your lungs, protected by the rib cage.

It is composed of four chambers: Right atrium Right ventricle directly linked Left atrium

Left ventricle directly linked

Separated by a partition

… There are 5 major blood vessels that

are connected to the heart. Superior and inferior vena cava, (veins) Pulmonary vein Pulmonary artery Aorta, (artery).

… Valves are also present in the heart. Without these valves, blood would flow

backwards in the heart. They are called atrioventricular valves.

Several blood vessels are attached to the heart. Veins, (superior and inferior vena cava,

pulmonary veins), attached to both atria. Arteries, (aorta and pulmonary arteries),

are attached to the ventricles.

Function of the Heart The contraction and relaxation of the

heart muscles is what circulates blood throughout the body.

For blood to enter the heart: It must enter the atria from the veins. It must enter when the heart is at rest, or

is relaxed. The filling of the heart is called diastole.

… For blood to leave the heart:

The atria must contract, pushing blood into the ventricles.

Then, the ventricles contract, pushing blood into the arteries attached to the heart, (aorta and pulmonary). This is called systole.

The pulse that you feel corresponds to the contractions of the left ventricle, (it is larger). 75 beats per minute when at rest.

Circulation Routes The heart is a double pump. Because

the two sides of the heart are separated, the blood is pumped in and out by different routes.

On the right side of the heart, the mechanism is called pulmonary circulation.

On the left side, it is called systemic circulation.

Pulmonary vs. SystemicPulmonary

Right side. Shorter circuit. Blood is rich in CO₂ Blood exits the right

ventricle and flows to the capillaries of the lungs.

CO₂ exchanges with O₂. Now rich in O₂, blood

returns to the heart and enters the left atrium through a pulmonary vein.

Systemic Left side. Longer circuit. Blood is rich in O₂. Blood exits the left

ventricle through the aorta. Aorta divides into arteries

and capillaries which shed O₂ at the cells and pick up CO₂.

Now rich in CO₂, blood returns to the left atrium, entering via the Vena Cava.

Circulation Routes

Image Credits http://

www.neodenta.lt/Treatment-using-concentrated-blood-plasma

http://www.interactive-biology.com/3820/a-brief-review-on-the-study-of-blood-and-its-different-components/

http://www.phschool.com/science/biology_place/biocoach/cardio2/pathway.html

http://www.infovisual.info/03/060_en.html http://

www.kidport.com/reflib/science/humanbody/cardiovascular/Capillaries.htm