The Circulatory System

The Circulatory System

• Transportation system of a living organism (move things around body like streets and highways of a city)

• Humans have closed circulatory system (blood flows through vessels)

• In pictures, the heart will be pictured “backwards”

The Heart

• Composed mostly of muscle and is the size of a fist• Contractions of heart pump blood through circulatory

system• Right side of heart divided from left side by septum (a

wall of muscle). This wall prevents mixing of O2 poor blood and O2 rich blood

• Heart has four chambers– 2 atria – upper chambers, left and right atrium, receive blood

into heart– 2 ventricles – lower chambers, left and right ventricles,

pump blood out of heart

The Heart

Right Ventricle

Right Atrium

Left Atrium

Inferior Vena CavaVein that brings oxygen-poor blood from the lower part of the body to the right atrium

Tricuspid ValvePrevents blood from flowing back into the right atrium after it has entered the right ventricle

Pulmonary ValvePrevents blood from flowing back into the right ventricle after it has entered the pulmonary artery

Pulmonary VeinsBring oxygen-rich blood from each of the lungs to the left atrium

Superior Vena CavaLarge vein that brings oxygen-poor blood from the upper part of the body to the right atrium

AortaBrings oxygen-rich blood from the left ventricle to the rest of the body

Pulmonary ArteriesBring oxygen-poor blood to the lungs

Aortic ValvePrevents blood from flowing back into the left ventricle after it has entered the aorta

Mitral ValvePrevents blood from flowing back into the left atrium after it has entered the left ventricle

Left Ventricle

Septum

CO2 Rich, O2 Poor Blood from body

To Lungs

O2 Rich, CO2 Poor Blood from lungs

To Body

Circulation Through the Body

• Heart is two separate pumps– Right side pumps O2 poor blood from heart to lungs =

pulmonary circulation (in lungs, CO2 leaves blood and O2 enters blood)

– Left side pumps O2 rich blood to body = systemic circulation

Just so You Know……..

• ALL BLOOD IS RED!!!!!!!!!! O2 rich and O2 poor blood is RED!!!!!!!!! In PICTURES, O2 poor blood is often colored blue so that you can see the path of the O2 poor blood. ALL BLOOD IS RED!!!!!!!!!!

Blood Flow Through Heart

• Blood enters heart through the atria and flows into the ventricles and then out from the ventricles

• Valves in the heart between the atria and ventricles prevent blood from moving backwards within the heart

• Valves at the exits of the ventricles prevent blood from flowing back into the heart

• These valves keep blood moving in ONE direction

Circulation Through the BodyCapillaries of

head and arms

Capillaries of abdominal organs and legs

Inferior vena cava

Pulmonary veinCapillaries of

right lung

Superior vena cava

Aorta Pulmonary artery

Capillaries of left lung

The Circulatory System

Heartbeat

• Muscle fibers (one in the atria and one in the ventricles) are stimulated by the nervous system = contraction of the heart

• Heart beats faster or slower depending on how much O2 the body needs

Heartbeat

Blood Vessels

• Three types of blood vessels in circulatory system – arteries, capillaries, and veins

Arteries

– Arteries – large vessels that carry blood from the heart to the body

» Almost all arteries carry O2 rich blood» Thick walls made of smooth muscle that withstand

the pressure of the blood coming out of the heart» When you feel your pulse, you are feeling the

walls of an artery moving

Capillaries

– Capillaries – smallest blood vessels» Very thin walls (one cell thick) and VERY small» Bring nutrients and O2 to cells and remove CO2 from

cells

Veins

– Veins – blood returns to heart in veins» Made of smooth muscle» Have valves to prevent backflow

The Three Types of Blood Vessels

Capillary

Connective tissue

Connective tissue

Smooth muscle

Smooth muscle

Endothelium

Endothelium

Valve

Venule

Endothelium

Arteriole

VeinArtery

Blood Pressure

• Force of blood on arteries’ walls = blood pressure

• Two numbers – systolic and diastolic pressures

– Systolic pressure = force felt in arteries when ventricles contract (top number)

– Diastolic pressure = force felt in arteries when ventricles relax (bottom number)

• Average for adults is 120/80

Blood

• Blood collects O2 from lungs, nutrients from digestive tract, and waste products from cells

• Helps regulate body temperature

• Helps fight infections

• Helps to form clots to repair vessels

• 4 to 6 Liters of blood in body

Blood

Whole Blood Sample

Red blood cells

White blood cells

Platelets

Plasma

Sample Placed in Centrifuge Blood Sample That Has Been Centrifuged

Blood

Whole Blood Sample

Red blood cells

White blood cells

Platelets

Plasma

Sample Placed in Centrifuge Blood Sample That Has Been Centrifuged

Blood Plasma

• 45% of blood is cells• 55% is plasma, which is mostly water• Plasma helps to transport substances, clot blood,

and fight infections

Blood Cells

• Two types of blood cells – Red and White Blood Cells– Red Blood Cells (RBC) – transport O2

» Most numerous

» Get color from hemoglobin

» Shaped like discs

» Made from red bone marrow

» Live for 120 days

– White Blood Cells (WBC) – attack foreign substances or organisms

» Less numerous

» No hemoglobin

» Most live for a few days

» Made from red bone marrow

Blood Clotting

• Made possible by plasma proteins and cell fragments called platelets

• When platelets come into contact with broken blood vessels, they become sticky and cluster around would. They release proteins that start a series of chemical reactions, eventually forming tiny filaments which stop the bleeding

Blood Clotting

Break in Capillary Wall

Blood vessels injured.

Clumping of Platelets

Platelets clump at the site and release thromboplastin. Thromboplastin converts prothrombin into thrombin..

Clot Forms

Thrombin converts fibrinogen into fibrin, which causes a clot. The clot prevents further loss of blood..

Inflammation

The Lymphatic System

• As blood circulates, some leaks into tissues• Network of vessels (lymphatic system) collects this

fluid lost by the blood and returns it to the circulatory system

• Helps with nutrient absorption• Helps fight off infection – “swollen glands” when

you’re sick