Circulatory systemHeart

Done by: Sumaiah alghamdi /Nora alkahtani /Nora alhoshani \Latifa Qassim

Submitted to : Dr. khadejah

Content :• Definition • Function• Circulatory system content • Heart anatomy • Artioventricular and semilunar valves• Cardiac cycles• Heart rate and cardiac output• Blood pathway in systematic and pulmonary circuits• Blood content.• Blood vessels• Heart diseases

Definition: The system that moves blood throughout the

body.

Function:

The Circulatory System is responsible for transporting materials throughout the entire body. It transports nutrients, water, and oxygen to the body cells and carries away wastes such as carbon dioxide that body cells produce.

Circulatory system content

The circulatory System is divided into three major parts:

1. The Heart2. The Blood3. The Blood Vessels

1.Heart• The heart is located near the anterior chest

wall , directly posterior to the sternum.• The great veins arteries are connected to the

superior end of the heart at its base.

1.Heart• The heart surrounded the pericardial sac,

sits in the anterior portion of the mediastinum.

• The mediastinum the region between the two cavities , also contains the great vessels , thymus ,esophagus and trachea.

1.Heart• The pericardium is lined by a delicate serous

membrane that can be divided into the1. visceral pericardium which covers and adheres

closely to the outer surface of the heart.2. parietal pericardium which lines the inner surface

of the pericardial sac , which surrounds the heart.

• *The pericardial sac , or fibrous pericardium, which consist of a dense network collagen fibers.

1.Heart

Anatomy of the heart• The heart contains four muscular chambers,

two associated with each circuit.1. The right atrium receives blood from the

systemic circuit and pass it to right ventricle which pumps blood into the pulmonary circuit.

2. The left atrium collects blood from the pulmonary circuit and empties it into the left ventricle , which pumps blood into the systematic circuit.

Anatomy of the heart• When the heartbeats, first the atria contract

, and then the ventricles contract.• The two ventricle contract at the same time

and eject equal volumes of blood into the pulmonary and systemic circuit.

Anatomy of the heart

The heart wall The wall of the heart reveals three distinct layer:1. The epicardium is the visceral pericardium

that covers the outer surface of the heart.

2.The myocardium or muscular wall of the heart , forms the atria and ventricles. This layer contains cardiac muscle tissue, blood vessels, and nerves. The myocardium consists of con- centric layers of cardiac muscle tissue.

The heart wall 3.The endocardium covers the inner surfaces

of the heart, including those of the heart valves. This simple squamous epithelium is continuous with the endothelium of the attached great vessels.

The heart wall

Artioventricular and semilunar valves:

• Although adjacent myocardial cells are joined together mechanically and electrically by intercalated discs, the atria and ventricles are separated into two functional units by a sheet of connective tissue – the fibrous skeleton previously mentioned.

• Embedded within this sheet of tissue are one- way atrioventricular (AV) valves.

• The AV valve located between the right atrium and right ventricle has three flaps and is therefore called the tricuspid valve .

Artioventricular and semilunar valves:

• AV valve between the left atrium and left ventricle has flaps and is this called the bicuspid or alternative mitral valve.

• The AV valves allow blood to flow from the atria ventricles, but they normally prevent the backflow of blood the atria.

• Opening and closing of these valves occur as a the ventricles are relaxed , the venous return of blood to the causes the pressure in the atria to exceed that in the ventricles .

Artioventricular and semilunar valves:

• The AV valves therefore open, allowing blood to enter the ventricle .As the ventricles contract, the intraventricular pre rises above the pressure in the atria and pushes the AV closed

Artioventricular and semilunar valves:

The heart valve

Relaxed ventricles

THE CARDIAC CYCLE:• Electrical activity coordinates the rhythmic contraction

and relaxation of the heart’s chambers.• Most currents in the heart are less than a millionth of an

ampere, but they exert a powerful influence on the heart muscle.

• The cardiac cycle consists of two phases • DIASTOLE[In this phase the heart’s ventricles are relaxed, is the longer

phase, taking up approximately two-thirds of the cycle]• SYSTOLE[the phase during which blood is Ejected from the ventricles, takes up the remaining one third]

During diastole:• The sinus node generates an impulse that forces the two

atria to contract. • In this phase, the tricuspid and mitral valves are open,

and blood is propelled from the atria into the relaxed ventricles.

• By the end of diastole, the electric impulse reaches the ventricles, causing them to contract.

During systole: the contracting ventricles close the tricuspid and mitral

valves. Shortly afterward, the pressure of the blood inside the ventricles rises sufficiently to force the pulmonary and aortic valves to open, and blood is ejected into the pulmonary artery and the aorta.

As the ventricles relax again, blood backs up from the pulmonary artery and the aorta, closing down the pulmonary and aortic valves.

The pressure in the relaxed ventricles is now lower than in the atria, the tricuspid and mitral valves open again, and the

cardiac cycle starts anew. This events in fact takes approximately a second.

The familiar double throb (lub dub) of the beating heart corresponds to the two sets

of synchronized contractions that occur during the cardiac cycle.

The throbbing sound we hear comes from:Snapping of the valves,Accompanying vibrations of other heart

structures Turbulence produced by the flow of blood.

THE THROBBING SOUND OF HEART

Pulmonary and systemic circulations:

Pulmonary and systemic circulations:The circulatory system is extremely important in sustaining life.

It’s proper functioning is responsible for the delivery of oxygen and nutrients to all cells, as well as the removal of carbon dioxide, waste products, maintenance of optimum pH, and the mobility of the elements, proteins and cells, of the immune system.

Both atria contract at the same time and that both ventricles contract at the same time.

The heart works as two pumps, one on the right and one on the left that works simultaneously.

The right pump pumps the blood to the lungs or the pulmonary circulation at the same time that the left pump pumps blood to the rest of the body or the systemic circulation.

Systemic circulation The part of the network that delivers blood to all parts of the body except the lungsPulmonary circulation:The flow of blood through the lungs. The pressure in Pulmonary circulation system is only about one-sixth as great as in the systemic circulation, and the walls of pulmonary arteries and veins are significantly thinner than the walls of corresponding vessels in the rest of the body. In the pulmonary circulation, the roles of arteries and veins are the opposite of what they are in the systemic circulation, Blood in the arteries has less oxygen, while blood in the veins is oxygen-rich.

Blood pathway in systemic and pulmonary circulation

• Venous blood from systemic circulation (deoxygenated) enters the right atrium through the superior and inferior vena cava. The right atrium contracts and forces the blood through the tricuspid valve (right atrioventricular valve) and into the right ventricles. The right ventricles contract and force the blood through the pulmonary semilunar valve into the pulmonary trunk and out the pulmonary artery. The pulmonary arteries branch to transport blood to the lung, where gas exchange occurs between the lung capillaries and the air sacs (alveoli) of the lungs blood

releases carbon dioxide and receives a new supply of oxygen. The new blood is carried in the pulmonary veins that take it to the left atrium.

Continue…• The left atrium then contracts and forces blood through the left

atrioventricular (bicuspid) or mitral valve into the left ventricle. The left ventricle contracts forcing blood through the aortic semilunar valve into the ascending aorta (a very large, elastic artery). It then branches to arteries carrying oxygen rich blood to all parts of the body.

• As a result of cellular respiration, the oxygen concentration is lower and the carbon dioxide concentration is higher in the tissues than in the capillary blood, blood that drain into the systemic veins is thus partially depleted of oxygen and increase in carbon dioxide content.

• These veins ultimately empty into two large veins [the superior and interior vena cavae] that return the oxygenpoor blood to the right atrium.

The path of blood from the heart (right ventricle) through the lungs; and back to the heart (left atrium) completes one circuit: the pulmonary circulation

• The complete the systemic

circulation from the heart (left ventricle),

through the organ systems, and back to the heart (right

atrium).

Summary

HEART RATE AND CARDIAC OUTPUT

In an average adult, the pacemaker fires approximately 70 impulses a minute at rest, which means that in one minute the heart goes through a full cardiac cycle 70 times.

The amount of blood pumped by the heart in one minute is called the cardiac output.

When there is a need for an increased blood supply, as during physical exertion, the heart most commonly increases its output by beating faster—for example, up to 140 or 150 beats per minute.

STROKE VOLUME:• The cardiac output is determined not only by the

heart rate but also by the amount of blood the ventricles eject or pump out with each contraction,(This amount is called the stroke volume).

• A decrease in the stroke volume is one of the first signs of a failing heart.

• cardiologists usually measure only the stroke volume of the left ventricle, because it is the one that pumps blood to all of the body’s organs except the lungs

2 .Blood

The blood is the substance that is constantly flowing through our bodies. it is pumped by heart.

• the blood travels through thousands of miles of blood vessels right within the body.

• A young person has about a gallon of blood. An adult has about 5 quarts.

• the blood is not just a red liquid but rather is made up of liquids, solids and small amounts of oxygen and carbon dioxide.

Blood content:1- Red Blood Cells( erythrocytes)• Red Blood Cells are responsible for carrying oxygen and carbon dioxide. • Red Blood Cells pick up oxygen in the lungs and

transport it to all the body cells. After delivering the oxygen to the cells it gathers up the carbon dioxide and transports carbon dioxide back to the lungs where it is removed from the body when we exhale(breath out). There are about 5,000,000 Red Blood Cells in ONE drop of blood.

Blood content:2.White Blood Cells (leukocytes )• White Blood Cells help the body fight off

germs. by attack and destroy germs when they enter the body.

Blood content:3.Platelets• Platelets are blood cells that help stop bleeding. .,

fibers and other blood cells to help form a plug to seal the broken blood vessel. When the platelet plug is completely formed the wound stops bleeding.

Blood content:4.Plasma• Plasma is the liquid part of the blood.

Approximately half of your blood is made of plasma. The plasma carries the blood cells and other components throughout the body. Plasma is made in the liver.

Blood content5 .hemoglobin

•Hemoglobin is the protein molecule in red blood cells that carries oxygen from the lungs to the body's tissues and returns carbon dioxide from the tissues back to the lungs. Hemoglobin also plays an important role in maintaining the shape of the red

blood cells .

Blood content…con• Hemoglobin is made up

of four protein molecules (globulin chains) that are connected together. The normal adult hemoglobin (Hbg) molecule contains two alpha-globulin chains and two beta-globulin chains.

Blood content…con•Each globulin chain contains an important central

structure called the heme molecule.•Heme molecule Embedded within the iron that is

vital in transporting oxygen and carbon dioxide in our blood , and it’s responsible for the red color of blood.

Blood vessels• Blood is carried in a closed system of vessels that

begins and ends at the heart.• The three major types of vessels are arteries,

capillaries, and Veins.• Arteries carry blood away from the heart (O2 rich,

except pulmonary).• Veins carry blood toward the heart (O2 poor,

except pulmonary).• Capillaries contact tissue cells and directly serve

cellular needs.

Blood vessels wall

1. Tunica interna /intima- innermost: Endothelium (simple squamous epithelium) of connected cells; forms a smooth, flat , low friction surface. • All vessels have this layer, and all but the teeny-

tiniest have a basement membrane associated with the endothelium.

2. Tunica media-smooth muscle and elastic connective tissue surrounding the interna, Responsible for vasoconstriction and vasodilation.

3-Tunica Adventitia/Externa- connective tissue, surrounds entire vessel. Lots of collagen, some elastin.

Artery

• Their relatively thick, muscular walls make arteries elastic and contractile.

• Elasticity permits the vessel diameter to change passively in response to changes in blood pressure.

• When stimulated, arterial smooth muscles contract, constricting the artery—a process called vasoconstriction.

Types of artery1- Elastic arteries:• Elastic arteries are also known as conducting

arteries because they carry large volumes of blood away from the heart.

• The pulmonary trunk and aorta, as well as their major branches.

• The walls of elastic arteries are extremely resilient because

• The tunica media contains a high density of elastic fibers and relatively few smooth muscle cells.

• As a result, elastic arteries can tolerate the pressure changes of the cardiac cycle.

2- Muscular arteries:• Muscular arteries, or medium-sized arteries, are

also known as distribution arteries because they distribute blood to the body’s skeletal muscles and internal organs.

• Most of the vessels of the arterial system are muscular arteries.

• They are characterized by a thick tunica media. It contains more smooth muscle cells than does the tunica media of elastic arteries

• The external carotid arteries of the neck, the brachial arteries of the arms, the mesenteric arteries of the abdomen, and the femoral arteries of the thighs are examples of muscular arteries.

3-Arterioles:• Arterioles have a poorly defined tunica externa. • In the larger arterioles, the tunica media consists

of one or two layers of smooth muscle cells. • In the smallest arterioles, the tunica media

contains scattered smooth muscle cells that do not form a complete layer.

capillary• A capillary is an extremely small blood vessel

located within the tissues of the body, that transports blood from arteries to veins.

• Capillaries are most abundant in tissues and organs that are metabolically active, for example, muscle tissues and the kidneys have a greater amount of capillary networks than do connective tissues.

• Capillary walls are thin and are composed of endothelium, Oxygen, carbon dioxide, nutrients and wastes are exchanged through the thin walls of the capillaries.

Capillary types1- Continuous- most common. Endothelial cells connected by tight junctions, without large pores . Small spaces between tight junctions allow fluid and small solutes to pass into and out of blood. 2-Fenestrated- located in areas where lots of exchange of relatively large particles take place, like endocrine glands . Large pores in cells. Fenestrations are large enough to allow polypeptides like hormones .3-Sinusoidal. Large spaces between endothelial cells allow very large particles, including proteins and RBC, to pass.

Capillary Bed• Capillaries function not as individual units, but rather, as

part of an interconnected network called a capillary bed, or capillary plexus.

• A single arteriole generally gives rise to dozens of capillaries.

• They empty into several venules, the smallest vessels of the venous system.

• The entrance to each capillary is guarded by a precapillary sphincter.

• Contraction of the smooth muscle cells narrow the diameter of the capillary entrance, thereby reducing the flow of blood.

• Relaxation of the sphincter dilate the opening, allowing blood to enter the capillary faster.

• A capillary bed contains several direct connections between arterioles and venules.

• The wall in the first part of such a passageway contains smooth muscle that can change its diameter, this segment is called a metarteriole.

• The rest of the passageway resembles a typical capillary in structure and is called a thoroughfare channel.

veins

• Veins collect blood from all tissues and organs and return it to the heart.

• The walls of veins can be thinner than those of corresponding arteries because the blood pressure in veins is lower than that in arteries.

• Even though their walls are thinner, in general veins are larger in diameter than their corresponding arteries.

Venules

Venules • Are the smallest venous vessels. • They collect blood from capillary beds, are the

smallest venous vessels.• the smallest venules resemble expanded capillaries.Medium-Sized Veins• Are comparable in size to muscular arteries.• Their tunica media is thin and contains relatively few

smooth muscle cells.• The thickest layer of a medium-sized vein is the

tunica externa, which contains longitudinal bundles of elastic and collagen fibers.

Large Veins• Large veins include the superior and inferior

venae cavae and their tributaries within the abdominopelvic and thoracic cavities.

• All large veins have all three layers. • The slender tunica media is surrounded by a

thick tunica externa composed of a mixture of elastic and collagen fibers.

Heart Disease

• Coronary Artery DiseaseHeart disease is a result of plaque buildup in your coronary arteries -- a condition called atherosclerosis -- that leads to blockages. The arteries, which start out smooth and elastic, become narrow and rigid, restricting blood flow to the heart. The heart becomes starved of oxygen and the vital nutrients it needs to pump properly

Heart Disease

• Abnormal Heart RhythmsThe heart is an amazing organ. It beats in a steady, even rhythm, about 60 to 100 times each minute (that's about 100,000 times each day!). But, sometimes your heart gets out of rhythm. An irregular or abnormal heartbeat is called an arrhythmia. An arrhythmia (also called a dysrhythmia) can involve a change in the rhythm, producing an uneven heartbeat, or a change in the rate, causing a very slow or very fast heartbeat

Heart Disease• Heart FailureThe term "heart failure" can be frightening. It does not mean the heart has "failed" or stopped working. It means the heart does not pump as well as it should. This then leads to salt and water retention, causing swelling and shortness of breath. The swelling and shortness of breath are the primary symptoms of heart failure.• Congenital Heart DiseaseCongenital heart disease is a type of defect in one or more structures of the heart or blood vessels that occurs before birth.

Heart Disease

• CardiomyopathiesCardiomyopathies are diseases of the heart muscle itself. People with cardiomyopathies -- sometimes called an enlarged heart -- have hearts that are abnormally enlarged, thickened, and/or stiffened. As a result, the heart's ability to pump blood is weakened.

Heart Disease

Pericarditis Pericarditis is inflammation of the lining that surrounds the heart. It is a rare condition that is often caused by an infection.Aorta Disease and Marfan SyndromeThe aorta is the large artery that leaves the heart and provides oxygen-rich blood throughout the body. These diseases and conditions can cause the aorta to dilate (widen) or dissect (tear), increasing the risk for future life-threatening events

References:

• http://www.saylor.org/site/wp-content/uploads/2010/11/The-Cardiovascular-System.pdf

• http://doc.med.yale.edu/heartbk/1.pdf• http://www.kean.edu/~jfasick/docs/Fall%2009%20A&P/Chapter%2019.pdf• http://facweb.northseattle.edu/tstilson/homepage/ANPLectVessels.pdf• http://biology.about.com/od/anatomy/ss/capillary.htm

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