Download the circulatory system

Blood Vessels and Circulation
Objectives:
1.
Describe the structure and function of each of
the three types of blood vessels
2. Compare and contrast each type of blood vessel
3. Explain the path that blood takes from the heart
Quiz
1.
2.
3.
4.
What is a Erythrocyte?
What is the function of leukocytes?
Type A blood has what antibodies?
Which blood type is the universal recipient?
(Don’t forget the +/-)
5. What component of blood initiates blood
clotting?
How Does Blood Get
Around?
• Vessel
• A hallow tube that
circulates blood
• An average adult has ~160
000 km of blood vessels
The need for a circulatory system
Simple organisms don’t require a circulatory
system…Unicellular organisms are in direct
contact with their environment.
Multicellular organisms like Sponges don’t need
a circulatory system because their body has
only two layers so all their cells are very
close to their environment. Also their body
cavity has water containing oxygen and
nutrients constantly circulating through it.
Increasing Body Size
Bigger organisms have cells that are not in
contact with the external environment.
Cells can’t move around to get oxygen and
nutrients.
Cells must be surrounded by fluid for gases,
nutrients and wastes to be able to diffuse
across.
The cells of complex multicellular animals are
surrounded by tissue fluid.
Types of circulatory systems
Open circulatory system: blood and tissue
fluid (hemolymph) is pumped into body
cavities where it bathes all the cells.
Closed circulatory system: blood flows
through vessels. Blood and tissue fluid is
kept separate.
Three types of blood vessels
1. Arteries
2. Capillaries
3. Veins
• These blood vessels acting together are
responsible for transporting or carrying
blood to and from the heart, and to and from
every cell in the body
• This network is a continuous and closed
network
• Note: the arrow →represents the direction
of blood flow through the blood vessels of
the body
heart → arteries → arterioles → capillaries → venules
→ veins → heart
↓ ↑
O2 CO2
↓ ↑
cell
Function
• to carry blood away from the heart to the cells
of the body
Structure
• thick, muscular walls
• can stretch slightly to
accommodate the
heart pumping blood
Gas content of Blood
• blood carried by most arteries is rich in oxygen
(oxygenated)
Colour of blood
• bright red
Blood is pushed by
• blood in these vessels is pushed by the force of
contraction of the left ventricle of the heart
Blood Pressure
• these vessels are under high pressure due to
the force of contraction of the left ventricle
Clinical Usage
• to measure a pulse that represents an estimation of
heart rate
• to measure blood pressure
Note: the pulmonary arteries are the only
arteries that carry deoxygenated blood (blood
being pumped from the heart to the lungs)
Note: Blood pressure is greatest in the aorta, the
largest artery of the body, and then decreases
as it moves farther away from the heart
• are ‘small’ arteries
• they link arteries with the capillaries
Function
• Allow for the exchange of gases and the
transfer of nutrients and waste products
between cells and the blood; and they allow
for the continuation of blood flow as they
connect arterioles with venules.
• every cell in the body is within 50
micromillimetres of a capillary but only
certain capillaries are open at any given time.
Structure
• narrow – only one blood cell at a time can flow
through this vessel
• numerous – placed end to end they represent
6,300 square metres
• thin walls – composed of only a single layer
cells. The walls are only one cell thick, allowing
for maximum diffusion of gases, nutrients and
waste products
Gas content of Blood
• blood carried by capillaries will contain O2 leaving
the blood in the capillary and diffusing into the
cells and CO2 entering the blood from the cell.
Colour of blood
• red in arterial end and maroon in venous end
Blood is pushed by
• blood in these vessels is pushed by the residual
or left-over pressure of the force of contraction
of the left ventricle of the heart
Blood Pressure
• is very low in these vessels due to the large
surface area covered by capillaries, but not as
low as the blood pressure in the veins
• are ‘small’ veins
• they contain deoxygenated blood collected
from capillaries
• they connect or link capillaries to veins
Function
• to carry or return blood back to the heart
Structure
• the walls of the veins are thinner than those of
the artery.
• Veins contain valves that allow for one-way
flow of blood back to the heart. Valves prevent
back flow of blood, counter balancing the affect
of gravity
Gas content of Blood
• blood carried by most veins is rich in carbon dioxide
(deoxygenated)
Note: the pulmonary veins are the only veins that carry
oxygenated blood (back to the heart from the lungs)
Blood is pushed by
• blood in veins is squeezed back to the heart slowly, step by
step, valve by valve. The return of blood is also aided by
contraction of surrounding skeletal muscles
Blood Pressure
• is negligible
Movement of blood
• blood moves slowly and steadily through veins. There are
more veins than arteries and veins can expand more than
arteries, thus they contain about 70% of total blood volume.
Clinical Usage
• veins are used for injections, transfusions and withdrawing
blood. The reason for this is the fact that the walls of
veins are relatively thin and therefore easily punctured, and
the blood pressure is negligible so that blood will not rush
out of the puncture
• Key Terms:
–Arteries  Arterioles
–Veins  Venules
• Valves
–Capillaries
• What is the function of each of these
structures?
• The cardiovascular system is composed of
two major components or organs, what
are they?
i) a network of vessels – arteries, capillaries
and veins
ii) a pump – the heart
• transporting or carrying blood to and from
the heart, and to and from every cell in the
body
Q) What is a clinical usage of Arteries???
A) to measure a pulse that represents an
estimation of heart rate
A) to measure blood pressure
Q) What is a clinical usage of Veins???
A) used for injections, transfusions and
withdrawing blood. The walls of veins are
relatively thin and therefore easily punctured,
and the blood pressure is negligible so that
blood will not rush out of the puncture
Varicose Veins
A) A)Venules
Venules
Drain
blood blood
from capillaries
1) Drain
from capillaries
B) Veins
B)
Veins
C) Capillaries
D) Arteries
C) E)Capillaries
Arterioles
2) Smallest blood vessels
May
contain
valves valves
3) May
contain
Take blood to the heart
4) Take blood to the heart
Smallest
blood
5) Sites
forvessels
exchange of
Sitessubstances
for exchange ofbetween
substances
blood
between
andfluid
tissue fluid
andblood
tissue
Rate of blood flow is the lowest
6) Rate of blood flow is the
lowest
Your Task
• Fill in the table comparing the structure
and function of each of the types of blood
vessels we discussed today.
• H/W: Read through pages 250-254
• Answer questions 2-4 on page 253 and 1,
5-9 on page 255. These are potential test
questions and we can discuss them
tomorrow if enough people complete them.
Plenary
1. What are the three types of blood vessels?
2. What is the function of veins, capillaries and
arteries?
3. How are veins structured to help blood get
back to the heart?
4. How are capillaries structured to do their job?
5. State the path that blood takes from the
heart…what blood vessel does it pass through
first?