The Circulatory System

Chapter 37

Functions of the Circulatory System:

• Circulatory systems are used by large organisms that cannot rely on diffusion to exchange materials with the environment to transport – Oxygen– Carbon dioxide– Nutrients – Waste products– Hormones or cell products that are made in one place

and used in another

• Helps to regulate body heat

Components of the Circulatory System:

• Heart• Blood• Blood vessels

– Arteries– Arterioles– Capillaries– Venules– Veins

Parts of the Blood• Blood is the only liquid

tissue in the body• It contains a liquid called

plasma and 3 different cellular components– Red Blood Cells = RBC’s– White Blood Cells = WBC’s– Platelets

Plasma• Is 46% to 63% of total blood volume

• Mostly water (92%)

• Transports dissolved materials such as– Plasma proteins – Hormones– Ions (charged atoms)– Nutrients– Wastes

Red Blood Cells• Also called erythrocytes• Most numerous of all

blood cells• Produced in bone marrow

• Transport O2 and CO2

• Contain HEMOGLOBIN, a protein that oxygen binds to

• No NUCLEUS• Last 120 days

White Blood Cells• Also called leukocytes• Outnumbered by RBC’s

1000 to 1.• Produced in bone marrow• Contain a nucleus• Guard against infection,

fight parasites, and attack bacteria

• Can last days, weeks, or months.

Platelets• Also called thrombocytes• Cell fragments that function in blood clotting• Certain cells in bone marrow break into pieces and

the pieces are released into the blood stream• When platelets come into contact with the edge of a

broken blood vessel, they become very sticky.• A cluster of platelets will form around the wound

and begin to release chemicals called clotting factors, which start chemical reactions to clot blood.

Blood Vessels• All mammals including humans have a

closed circulatory system.

• This means that blood is always contained within the heart or a blood vessel

• There are 3 main types of blood vessels– Arteries– Veins– Capillaries

Arteries• Large vessels that carry

blood away from the heart

• Thick, muscular walls b/c they are exposed to high pressure

• All except pulmonary arteries carry oxygen rich blood

• The aorta is the largest blood vessel in the body

Veins• Return blood to the heart• MOST carry

deoxygenated (or oxygen poor blood)

• Have muscular walls, but not nearly as thick as arteries.

• Have valves to prevent backflow of blood when it is being pumped from places below the heart

Capillaries• Smallest of all blood

vessels.• Walls are only 1 cell

thick.• Nutrients, wastes, &

gases are exchanged with cells through diffusion into and out of capillaries.

• So narrow, RBC’s must line up and go single file

The Heart

• Mammals have a 4 chambered heart made of a type of muscle tissue called cardiac muscle.

• There are two atria and two ventricles.

• The atria are for collecting blood, the ventricles are for pumping blood.

• Oxygenated and deoxygenated DO NOT mix.

The Heart

• The walls of the ventricles are thicker than those of the atria.

• The walls of the left ventricle are the thickest of all because it must pump blood to the whole body, not just the lungs.

Pulmonary Circulation:

– Blood returns from the body to the right atrium

– It passes through the tricuspid valve to the right ventricle

– It is pumped through the pulmonary arteries to the lungs.

– Blood returns to the left atrium from the pulmonary veins

Systemic Circulation:

– Blood returns to the heart from the lungs through the pulmonary veins, which empty into the left atrium.

– Blood passes through the mitral valve, into the left ventricle.

– Blood passes through the aortic valve and into the aorta. Blood passes through arteries, arterioles, capillaries, venules, and veins.

– Blood returns to the heart through the vena cava, which empties into the right atrium.

The Heartbeat

•  During the period of contraction (systole), the heart pumps blood out through the arteries; during the period of relaxation (diastole), the heart fills with blood.

• One complete sequence of filling and pumping blood is called a cardiac cycle, or heartbeat.

The pacemaker

• The heart's rhythm of contraction is controlled by the sinoatrial node (SA node), often called the pacemaker.

• This node is part of the heart's intrinsic conduction system, which is made up of specialized myocardial cells called nodal cells.

The activity of the conduction system, muscles, and valves of the heart are synchronized so that the heart

can operate as a pump.

• The conduction system initiates and coordinates the muscular activity of the heart.

• Pressure differentials that result from muscle activity actuate the opening and closing of valves.

• The opening and closing of valves directs the flow of blood through the heart.

Flow of Blood

Path of blood

You are a red blood cell in the superior vena cava. Trace your path through the heart and body using the following terms. Begin and end at the superior vena cava. – Right ventricle, right atrium, left ventricle, left atrium.– Tricuspid valve, mitral valve, aortic valve– Pulmonary arteries, pulmonary veins, lungs– Veins, venules, arteries, arterioles, capillaries, aorta

The Heart• Mammalian hearts contain 4 chambers• 2 atria (atrium singlular) for collecting

blood• 2 ventricles for pumping blood• Oxygen rich and oxygen poor blood DO

NOT mix• Valves separate the atria and ventricles• A wall called the septum separates right

from left

The Heart

superior vena cava

superior vena cava

aorta

superior vena cava

aorta

left pulmonary artery

right pulmonary artery

superior vena cava

aorta

left pulmonary artery

right pulmonary artery

pulmonary veins

pulmonary veins

superior vena cava

aorta

left pulmonary artery

right pulmonary artery

pulmonary veins

pulmonary veins

right atrium

superior vena cava

aorta

left pulmonary artery

right pulmonary artery

pulmonary veins

pulmonary veins

right atrium

left atrium

superior vena cava

aorta

left pulmonary artery

right pulmonary artery

pulmonary veins

pulmonary veins

right atrium

left atrium

tricuspid valve

superior vena cava

aorta

left pulmonary artery

right pulmonary artery

pulmonary veins

pulmonary veins

right atrium

left atrium

tricuspid valve

bicuspid valve

superior vena cava

aorta

left pulmonary artery

right pulmonary artery

pulmonary veins

pulmonary veins

right atrium

left atrium

tricuspid valve

bicuspid valve

right ventricle

superior vena cava

aorta

left pulmonary artery

right pulmonary artery

pulmonary veins

pulmonary veins

right atrium

left atrium

tricuspid valve

bicuspid valve

right ventricleleft ventricle

superior vena cava

aorta

left pulmonary artery

right pulmonary artery

pulmonary veins

pulmonary veins

right atrium

left atrium

tricuspid valve

bicuspid valve

right ventricleleft ventricle

septum

superior vena cava

aorta

left pulmonary artery

right pulmonary artery

pulmonary veins

pulmonary veins

right atrium

left atrium

tricuspid valve

bicuspid valve

right ventricleleft ventricle

septum

semi-lunar valves

superior vena cava

aorta

left pulmonary artery

right pulmonary artery

pulmonary veins

pulmonary veins

right atrium

left atrium

tricuspid valve

bicuspid valve

right ventricleleft ventricle

septum

semi-lunar valves

inferior vena cava

The heart

• Each side of the heart is completely separate and so deoxygenated blood and oxygenated blood do not mix

The heart

• The thickness of the walls of each chamber is related to the distance that it has to pump the blood.

• The atria just pump into the ventricles so are very thin

The heart

• The right ventricle has to pump the blood to the lungs and has a thinner wall than the left ventricle

• …because this has to pump blood all around the body

The heart

• The valves keep the blood flowing in one direction.

• The atrio-ventricular valves prevent the back flow of blood into the atria when the ventricles contract

• On the right side the tricuspid valve has three flaps, on the left the bicuspid has two flaps.

Structures of the Respiratory System

pharynx

larynx

trachea

bronchi

bronchioles

alveoli

diaphragm

Respiratory System

Function of the Respiratory System:

• To bring about the exchange of oxygen and carbon dioxide between the blood, the air, and the tissues.

Path of air to the lungs:

Nose or mouth pharynx larynx trachea bronchi bronchioles alveloli

Path of air inside the lungs:

Trachea bronchi bronchioles alveoli (air sacs)

Gas Exchange:

• 150 million alveoli in each lung• Oxygen dissolves in the moisture on the inner

surface of the alveoli and then diffuses across the capillary wall into the blood

• Carbon dioxide in the blood moves from the capillaries to the alveoli and is then exhaled.

• Inhaled air = 21% oxygen and 0.04% carbon dioxide

• Exhaled air = 15% oxygen and 4% carbon dioxide

Breathing:

• Movement of air into and out of the lungs• No muscles connected to the lungs.• Air pressure forces air into the lungs• The diaphragm is a muscle at the bottom of the body

cavity. • Inhaling: the diaphragm moves down the ribs move

up and out the chest cavity volume increases creates a partial vacuum inside the body cavity air is forced in

• Exhaling : diaphragm moves up the ribs move down and in volume of chest cavity decreases internal pressure rises above air pressure outside the body air is forced out

Breathing