CHAPTER 23 Circulation

CHAPTER 23Circulation

It transports O2 and nutrients to cells It takes away CO2 and other wastes

Artery and vein, cross-section •Blood smear

Circulatory system made up of 3 parts organ

heart tissues & cells

blood vessels arteries veins capillaries

blood red blood cells plasma

The circulatory system associates intimately with all body tissues

Capillaries are microscopic blood vessels They form an intricate network among the tissue

cells

Capillary

Redbloodcell

The circulatory system associates intimately with all body tissues II

No substance has to diffuse far to enter or leave a cell

Diffusion ofmolecules

INTERSTITIALFLUID

Capillary

Tissuecell

The cardiovascular system has two circuits The pulmonary

circuit conveys blood

between the heart and gas-exchange tissues

The systemic circuit carries blood

between the heart and the rest of the body

2 part system Circulation to

lungs(pulmonary) blood gets O2 from lungs drops off CO2 to lungs brings O2-rich blood from

lungs to heart Circulation to

body(systemic) pumps O2-rich blood to body picks up nutrients from

digestive system collects CO2 & cell wastes

Circulation of Blood

heart

lungs

body

Circulationto lungs

Circulationto body

The human heart 4-Chambered heart

atria (atrium) thin wall collection chamber receive blood

ventricles thick wall pump pump blood out right

atrium

leftatrium

rightventricle

leftventricle

AV

SL

AV

Lub-dub, lub-dub 4 valves in the heart

flaps of connective tissue prevent backflow

Heart sounds closing of valves “Lub”

force blood against closed AV valves

“Dub” force of blood against

semilunar valves Heart murmur

leaking valve causes hissing sound blood squirts backward through valve

Blood’s path through the heart

1. vena cavae 2. right atrium 3. valve 4. right ventricle 5. valve 6. pulmonary artery (to

lungs) 7. pulmonary veins 8. left atrium 9. valve 10. left ventricle 11. valve 12. aorta largest blood

vessel in the body.

Blood vesselsarteries

arterioles

capillaries

venules

veins

artery

arteriolesvenules

veins

Arteries: Built for their job Arteries

blood flows away from heart thicker walls

provide strength for high pressure pumping of blood

elastic & stretchable maintains blood

pressure even when heart relaxes

Major arteries

pulmonaryartery

pulmonary

artery =to lungs

aortacarotid = to headto brain & left arm to right arm

coronary arteries

to body

Veins: Built for their job Veins

blood returns back to heart thinner-walled

blood travels back to heart at low speed & pressure

why low pressure? far from heart

blood flows because muscles contract when we move squeeze blood through veins

valves in large veins in larger veins one-way valves

allow blood to flow only toward heart

Open valve

Blood flowstoward heart

Closed valve

Major Veins

pulmonaryvein =

from lung

superiorvena cava = from upper body

pulmonaryvein = from lung

inferiorvena cava = from lower body

Structure-function relationship Capillaries

very thin walls allows diffusion of

materials across capillary O2, CO2, H2O,

food, wastebody cell

O2

food

waste

CO2

The heart contracts and relaxes rhythmically

Diastole Blood flows from

the veins into the heart chambers

Systole The atria briefly

contract and fill the ventricles with blood

Then the ventricles contract and propel blood out

The pacemaker sets the tempo of the heartbeat

The SA node (pacemaker) generates electrical signals that trigger the contraction of the atria

The AV node then relays these signals to the ventricles

heart pumping controlled by electrical impulses signal also transmitted to skin = EKG electrocardiogram

Connection: What is a heart attack? A heart attack is damage that occurs when

a coronary feeding the heart is blockedAorta

Leftcoronaryartery

Blockage

Dead muscle tissue

Rightcoronaryartery

Cardiovascular diseases are the leading cause of death in the United States

Blood vessel blockage is usually due to blood clots Atherosclerosis: Growths called plaques develop in the inner

wall of the arteries, narrowing their bore In some cases, plaques also become hardened by calcium

deposits, leading to arteriosclerosis, commonly known as hardening of the arteries

PlaqueEpitheliumSmoothmuscle

Connectivetissue

Women & Heart Disease

Heart disease is 3rd leading cause of death among women aged 25–44 years & 2nd leading cause of death among women aged 45–64 years.

Risk factorsSmokingLack of exercise

High fat dietOverweight

Death rates for heart disease per 100,000 women, 2002

Blood exerts pressure on vessel walls

Blood pressure depends on cardiac output resistance of

vessels Pressure is highest

in the arteries It drops to zero by

the time the blood reaches the veins

Systolicpressure

Diastolicpressure

Relative sizes andnumbersof blood vessels

Three factors keep blood moving back to the heart

muscle contractions breathing one-way valves

Connection: Measuring blood pressure can reveal cardiovascular problems Blood pressure is measured as systolic and diastolic

pressures Hypertension is persistent systolic pressure higher

than 140 mm Hg and/or diastolic pressure higher than 90 mm Hg

It is a serious cardiovascular problem

STRUCTURE AND FUNCTION OF BLOOD Blood consists of cells suspended in plasma Plasma is an aqueous solution of various

substances

Blood Cell production ribs, vertebrae,

breastbone & pelvis

Stem cells “parent”

cells in bone marrow

differentiate into many different types of cells

white bloodcells

red bloodcells

white blood cells

Blood & blood cells Blood is a tissue of fluid & cells

plasma liquid part of blood dissolved salts, sugars, proteins, and more

cells red blood cells (RBC)

transport O2 in hemoglobin white blood cells (WBC)

defense & immunity platelets

blood clotting

Red blood cells transport oxygen Small round cells

produced in bone marrow 5 liters of blood in body 5-6 million RBC in drop of human blood last 3-4 months (120 days)

filtered out by liver ~3 million RBC destroyed each second

Hemoglobin Protein which carries O2

250,000 hemoglobins in 1 red blood cell

O2

O2O2

O2

White blood cells help defend the body

White blood cells (leukocytes)

function both inside and outside the circulatory system They fight

infections and cancer

Blood clots plug leaks when blood vessels are injured

When a blood vessel is damaged, platelets respond They help trigger

the formation of an insoluble fibrin clot that plugs the leak

Connection: Stem cells offer a potential cure for leukemia and other blood cell

diseases All blood cells

develop from stem cells in bone marrow Such cells may

prove valuable for treating certain blood disorders

2008-2009

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