20.1: The Circulatory System

Section Objectives: Distinguish among the

various components of blood

Trace the route blood takes through the body and heart.

Explain how heart rate is controlled.

Circulatory system

made up of 3 parts organ

heart tissues & cells

blood vessels arteries veins capillaries

blood red blood cells plasma

Your Blood: Fluid Transport

Blood is a tissue of fluid & cells

transports O2 and nutrients to cells

takes away CO2 and other wastes

Aids in fighting disease

Helps maintain body temp.

Blood composition:Plasma: 55% (liquid part)Blood cells: 45% (red,

white, & platelets

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

Red blood cells: Oxygen carriers

Bioconcave disc shaped, most numerous

No nucleus when mature, last 120 days

5-6 million RBC in drop of human blood

Produced in red marrow of long bones

contain hemoglobin Hemoglobin enables the

transport of O2

Hemoglobin Protein which carries O2

250,000 hemoglobins in 1 red blood cell

O2

O2O2

O2

White blood cells: Infection fighters Largest blood cell play a major role in

protecting your body from foreign substances.

White Blood Cells

Platelets: Blood clotting Smallest (fragments) help blood clot after an

injury. Short-lived

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

pulmonaryartery =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, waste body cell

O2

food

waste

CO2

Your Heart: The Vital Pump Atria: upper

chamber which receive blood that pump blood to

Ventricles: muscular walled chambers which pump blood from heart

leftatrium

rightatrium

leftventricleright

ventricle

2 part system Circulation to lungs

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

lungs to heart Circulation to body

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

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.

Heartbeat regulation

surge of blood through an artery is called a pulse.

Pacemaker: initiates heartbeat generates an electrical impulse that spreads over both atria.

Sinoatrial node (Pacemaker

Blood pressure the force that the blood exerts on the blood vessels. Blood pressure is measured as systolic (ventricles

contract) and diastolic (ventricles relax) pressures

Control of the heart

A portion of the brain called the medulla oblongata regulates the rate of the pacemaker, speeding or slowing its nerve impulses.

If the heart beats too fast, the medulla oblongata, sends signals that slow the pacemaker.

If the heart slows down the medulla oblongata sends signals to speed up the pacemaker and increase the heart rate.

Medulla oblongata

wastefood

Circulatory System & Homeostasis Homeostasis

keeping the internal environment of the body balanced

need to balance food & O2 in need to balance energy (ATP) production need to balance CO2 & waste out

Exercise heart beat faster

need more ATP bring in more O2 & food; remove more CO2 & waste out

Disease poor lung or heart function = heart beat faster

need to work harder to bring in O2 & food & remove wastes

O2

ATP

CO2

Cardiovascular disease Atherosclerosis & Arteriosclerosis

deposits inside arteries (plaques) develop in inner wall of the arteries,

narrowing their channel increase blood pressure increase risk of heart attack, stroke, kidney

damage

normal artery hardening of arteries

Cardiovascular healthbypass surgery

Risk Factors genetics diet

high animal fat exercise & lifestyle

smoking lack of exercise

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

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