The Circulatory System Part One – Blood Part Two – Circulatory System

Part One - Blood At 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.

Components of Blood Liquid Element  Plasma Formed Elements  Red blood cells, (RBC)  White blood cells, (WBC)  Platelets

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 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 TypeA+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- 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 System At 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 system Describe 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. Systemic Pulmonary  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

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