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Higher Human Biology
Unit 2
Physiology & Health
KEY AREA 5: Structure and Function of Arteries, Capillaries and Veins
Higher Human Biology
We are going to build on the knowledge and skills that you developed during N5 and will
learn about the following Physiology & Health key areas : -
Key Area 1 – Reproductive Organs
Key Area 2 –Hormonal Control of Reproduction
Key Area 3 – Biology of Controlling Fertility
Key Area 4 – Ante- and Postnatal Screening
Key Area 5 – Structure and Function of Arteries, Capillaries and Veins
Key Area 6 – Structure and Function of the heart
Key Area 7 – Pathology of Cardiovascular Disease (CVD)
Key Area 8 – Blood Glucose Levels and Obesity
Physiology & Health
KEY AREA 5 – Structure and Function of Arteries, Capillaries and Veins
a) Structure and function of arteries, capillaries and veins
b) Exchange of materials between tissue fluid and cells
N5 Revision - Role of Blood Vessels
The three types of blood vessel are Arteries, Capillaries &
Veins
Arteries divide up into capillaries, then capillaries join up
to make Veins
N5 Revision - Arteries, Capillaries & Veins
Thin walled
(only 1 cell
thick)
Thick
muscular
wall
Arteries
•
•
•
•
•
thick muscular walls
a narrow channel
carry blood under
high pressure AWAY
from the heart
a pulse indicates that
blood is flowing
through an artery
Arteries carry
Oxygen and nutrients
Capillaries
•
•
•
•
thin walled to allow
exchange of gas, food
and wastes
Capillaries form
networks through organs
and tissues and have a
large surface area
Oxygen leaves capillaries
and enters tissues/cells
Carbon Dioxide leaves
tissues/cells and enters
capillaries
Valves to stop
blood flowing
backwards
Veins
•
•
•
Veins thin muscular
walls and a wide
channel and carry
blood under low
pressure TO the
heart
Veins contain valves
to prevent blood
flowing backwards
Veins carry Carbon
Dioxide and Wastes
Physiology & Health Learning Intentions
KEY AREA 5 – Structure and Function of Arteries, Capillaries and Veins
a) Structure and function of arteries, capillaries and veins
b) Exchange of materials between tissue fluid and cells
5a) Arteries, Capillaries & Veins
Arteries
Capillaries
Veins
Function
Carry blood away from heart at high
pressure
Allow the exchange of
substances
Carry blood to the heart at low
pressure
Wall Structure
Thick & Strong
Outer Layer (elastic fibres)
Middle Layer (muscle)
Inner Layer (elastic fibres)
Lining of endothelium
Very thin
Only one cell thick
Thin walled
Outer Layer (elastic fibres)
Middle Layer (muscle)
Inner Layer (elastic fibres)
Lining of endothelium
Lumen
Narrow Lumen
Very narrow
Wider Lumen
Valves
NO
NO
YES to stop back flow
Divide up into
Arterioles
Blood is transported from
arterioles (small arteries) to
venules (small veins) by passing
through the dense network of
tiny microscopic vessels called
capillaries
Venules
How structure
is related to
function
Strength & elasticity needed to:- withstand pulsing of blood
- prevent bursting
- help to maintain blood pressure
- for vasconstriction/vasodilation
Thin walls, and narrow lumen:- materials can easily be
exchanged
Wide lumen:
- Less resistance to blood flow
5c) Arteries, Capillaries & Veins
Capillary
5d) Vasoconstriction and Vasodilation
• The smooth muscular middle layer of arterioles can contract
(vasoconstriction) or relax (vasodilation) to control blood flow e.g.
during a football match, arterioles undergo vasodilation at muscles
to increase the flow of blood to working muscles, and arterioles in
the small intestine undergo vasoconstriction to reduce blood flow to
these regions
5e) Exchange of materials – Blood Plasma
Blood consists of red blood cells, white blood cells, platelets and plasma
Plasma is a watery yellow fluid that contains all the blood cells and glucose,
amino acids, carbon dioxide, plasma proteins and ions
5f) Exchange of materials – Tissue Fluid
Blood arriving at the arteriole side of a capillary bed is at a higher pressure
than the blood in the capillaries, so blood is forced into these narrow
capillaries
As blood is forced into the narrow capillaries, it undergoes pressure filtration
and much of the plasma is squeezed out through the thin walls.
Tissue fluid differs from blood plasma as it contains little or no protein
because the protein molecules are too big to pass through
Tissue Fluid
5g) Exchange of materials – Tissue Fluid continued
Tissue fluid diffuses into cells, supplying cells with glucose, oxygen and other substances
Carbon Dioxide and other metabolic wastes diffuse out of the cells and into the tissue
fluid to be excreted
Most of the tissue fluid returns to the blood in the capillaries at the venule side of the
capillary bed
Excess tissue fluid is absorbed by thin-walled lymphatic vessels, and the fluid is now
called lymph. The lymphatic system returns lymph fluid to the circulatory system
(bloodstream)
Physiology & Health Questions
KEY AREA 5 – Structure & Function of arteries, capillaries and veins
1. Testing Your Knowledge 1
2.
Quick Quiz
Page 163
Q’s 1-4