bio156 chapter 6 powerpoint

8/14/2019 BIO156 Chapter 6 Powerpoint

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BIO 156

Chapter 6


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The Circulatory System


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The Heart

The heart is a muscular organ that pumps blood

throughout the body There are three layers in the heart walls:

The pericardium

The myocardium

The endocardium

Blood flows through two distinct circuits in the

cardiovascular system.

The pulmonary circuit, which transports blood toand from the lungs.

The systemic circuit, which delivers blood to the

body and returns it to the heart.


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The human heart consists of four chambers: two atria

and two ventricles.

The right atrium and right ventricle service the

pulmonary circuit.

The right atrium receives blood, low in oxygen and

rich in carbon dioxide, from the superiorand

inferior vena cavae.

From the right atrium, blood is pumped into the

right ventricle, then to the lungs.


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Blood, resupplied with oxygen, returns to the heart via

the pulmonary veins, which empty into the left atrium.

The left atrium and left ventricle pump blood into the

aorta and are part of the systemic circuit.

Blood from the aorta supplies cells of tissues and organs

with oxygen and picks up cellular wastes.


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Valves help control the flow of blood in the heart

Heart sounds result from the closing of heart

valves


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Heart rate is controlled primarily by an internal

pacemaker .

The sinoatrial (SA) node is located in the upperwall of the right atrium.

The cells of the SA node discharge periodically,sending impulses to all atrial muscle cells, whichcause them to contract in unison.

The impulse next travels to the ventricles, but itspassage is delayed to time for the ventricles to fill.

The impulse is channeled the atrioventricular(AV) node.


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External factors regulate thepacemaker

The SA node is curbed byimpulses transmitted by nervesthat connect the heart with acontrol center in the brain.

Hormones also play a role incontrolling heart rate.

The hearts electrical activity can

be measured on the surface of thechest.

The measurement is called anelectrocardiogram.


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Blood flows from the heart to the capillaries, then back

to the heart via veins.

Arteries and arterioles deliver oxygen-rich blood to

tissues and organs.

The aorta and many of its chief branches areelastic.

Blood pressure and flow rate are highest in the

aorta and drop considerably as the arteries branch.

This decline enhances the rate of exchangebetween the blood and the tissues.

The Blood Vessels


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Capillariespermittheexchangeofnutrientsandwastes

Capillariesformbranchingnetworks,knownascapillarybeds,amongthecellsofbodytissues

Venulesdraincapillariesandmergetoformveinsthattransportbloodbacktotheheart.


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Intheveinsabovetheheart,gravityisthechiefmeansofpropulsion.

Veinsbelowtheheartrelyonthemovementofbodypartstosqueezethebloodupwardandonvalvesthatpreventthebackflowofblood


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The lymphatic system is a

secondary system of

vessels that returns excess

fluid to the circulatory

system

The lymphatic system

includes the lymphnodes, spleen, thymus,

and tonsils.

Lymph nodes filter the

lymph. Normally, lymph is

removed from tissues at

a rate equal to its

production.

The Lymphatic System


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Cardiovascular Diseases Causes and Cures

The cardiovascular systemthe heart and bloodvesselsare subject to a variety of potentially life

threatening disease


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Myocardial infarction: blockage ofthe arteries supplying heartmusclecanleadtoheartattacks.

can occurwithout warning ormay be preceded by severalweeksofangina.

Fibrillation: anothertype ofheartattack results from a loss ofelectricalcontrol.

The cardiac muscle cells beat

independently. The heart can stop beating

altogether(cardiacarrest).


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Preventingheartattacksisthebestcure

Properdiet,exercise,andstressmanagementcanreducetheriskofheartproblem

Manymedicaltreatmentsareavailabletotreatheartattacks.


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High blood pressure (hypertension) develops gradually

over time.

Hypertension is a prolonged elevation in blood

pressure. Early detection and treatment are essential to prevent

serious problems, including heart attacks.


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Atherosclerosis results from

the buildup of cholesterol

plaque in arteries.

Arteries clogged withcholesterol force the heart

to work harder.

Blood clots can lodge in

narrowed coronary arteries.

Weakening of the arterial walls

can result in a rupture(aneurysm) of the wall.


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End of Chapter 6

bio156 chapter 6 powerpoint

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