Blood

Vessels

and Our

Pulse

Blood Vessels in Your Body

All the blood vessels in your body joined

together in a straight line would reach from

St. John’s, Newfoundland, to Victoria,

British Columbia, and back, twice!

End to end, they would span about 19 000

km

Our blood vessels are a complex network of

tubes that branch and re-branch

The largest blood vessel in the body is about

3 cm in diameter

The smallest blood vessels are about 5 μm

to 10 μm in diameter, just wide enough for

blood cells to pass through in single file

What are the 3 major types of blood

vessels?

Arteries

Veins

Capillaries

Review:

What do

arteries do?

What do veins

do?

What do

capillaries do?

carry blood away from the

heart to the rest of the body

bring blood from body back

to the heart

enable exchange of water

and chemicals between the

blood and the tissues

Arteries

Ventricles of heart contract to pump blood around the body, arteries expand

slightly in diameter to accommodate increased pressure of blood within

them

When the ventricles relax, the walls of the arteries return to their original

size, pushing the blood farther into the downstream vessels

The outer layer of arteries includes elastin fibres elasticity of the artery

walls ensures there is a continuous flow of blood through the blood vessels,

even when the heart is relaxed

A single large artery (aorta) leaves the heart and branches

into major arteries that carry blood around the body

Smallest branches are arterioles

Walls of arteries have three layers of tissue

an outer layer of connective tissue

a middle layer of smooth muscle

a smooth inner single layer of epithelial cells (endothelium)

Coronary Arteries

Veins Venules and veins carry deoxygenated blood containing CO2

and other waste products from the body tissues

Middle layer of smooth muscle not as thick as arteries

Walls are not as elastic

Internal diameter of veins is greater than that of arteries

Blood pressure in veins is lower than in arteries

How then does blood get back to the heart,

especially from the lower parts of the body?

Many of the larger veins have valves that ensure the blood flows in

only one direction

Skeletal muscles also help the circulation of blood

Muscles contract squeeze the veins increases the pressure in

the veins helps push the blood back toward the heart (in

conjunction with valves)

Capillaries Arterioles branch further into smaller blood vessels called

capillaries when it reaches the tissues of the body

Capillaries form networks of blood vessels that supply oxygen

and nutrients to every cell throughout the body tissues

Walls are only a single cell layer thick

O2/nutrients diffuse from blood into tissue fluid that

surrounds the cells

CO2/waste materials diffuse into the tissue fluid and then

into the capillaries.

Small in diameter: blood cells move through them in single

file

On one side of capillary networks are arteries and arterioles

carrying oxygenated blood and nutrients to the tissues. On

the other side, capillaries merge into venules and veins.

Blood flows slower through the capillary network provides

time for the diffusion of substances into and out of the

capillaries

When you are feeling for your pulse, are

you feeling a vein or artery? (Explain)

Think – Pair - Share

Heart contracts Blood is forced through artery Artery expands

Felt as the pulse if the artery is fairly large, close to the skin,

and in front of a bone or other firm structure

Major Arteries and Pulse Points

➢ Best places to take your pulse:

• at your wrist

• inside the elbow

• at the side of your neck

• on the top of your foot

➢ You can also take your

pulse at your groin, on

your temple or behind

your knees

Mini Investigation:

Taking a Pulse

Question: What is YOUR heart rate?

Purpose: To find your pulse at several different pulse points and determine your heart rate

Start here: The most common point is the radial artery in the wrist

Steps:

Find your pulse at the radial artery (runs along the thumb side of your wrist)

Count the number of beats in 15 seconds and multiply by 4 to obtain your heart rate. Record your heart rate.

Refer to the figure on the right to try to find your pulse at other accessible locations

Questions: Think – Pair - Share

Why do you think the radial artery is the

most commonly used pulse point?

Did you have difficulty finding other pulse

points? Why do you think it was more

difficult in other locations?

When police or medical personnel check for signs of life, they check the carotid pulse. Why do you think they check this pulse rather than the radial pulse?

At the doctor’s…

The apical pulse is the pulse over the top of the

heart, as typically heard through a stethoscope

with the patient lying on his or her left side

The normal apical pulse rate of an adult is 60 to

100 beats

Other than doing an electrocardiogram (ECG),

taking the apical pulse is the most accurate,

noninvasive way of assessing cardiac health.

The apical pulse provides information on count,

rhythm, strength and quality of the heart.