Transcript The Circulatory System

The
Circulatory
System
Idea that blood circulates in the
body dates back to the 1620s and
English physician William Harvey
Blood vessels form closed delivery
system that begins and ends with
the heart transporting blood 60,000
miles (the Earth has a
circumference of 24,902 miles)
Includes 50,000,000,000 capillaries
Functions of the Peripheral
Circulatory System
• Carries blood from heart to tissues
to heart
• Exchange nutrients, waste
products and gases w/tissues
• Transports substances (hormones,
components of immune system,
coag. Agents, NZs, nutrients,
gases, waste products, etc.
• Helps regulate blood pressure
• Directs blood flow to tissues when
required to maintain homeostasis
Vessels In Sequence
ELASTIC ARTERIES
MUSCULAR ARTERIES
ARTERIOLES
CAPILLARIES
VENULES
SMALL VEINS
MEDIUM/LARGE VEINS
General Features of
Blood Vessels
Tunicsthe
Tunicadetails
Intima
innermost layer smooth
surface of endothelium;
enables ease of blood flow
Tunica Media
middle layer of smooth muscle
cells arranged circularly with
variable amounts elastic and
collagen fibers; elastic
connective tissue in muscular
arteries
Tunica Externa or Adventitia
outer layer of connective
tissue
Action of
Smooth Muscle
Long, narrow,
tapered muscle
cells arranged
circularly
that contract
and relax
slowly so not to
affect heart
action but
control size of
blood vessel
lumen
Specialized
Features of
Blood Vessels
1. Arteries- conduct blood
under high pressure;
have thick strong walls
a. elastic arteriesb. muscular arteriesc. arterioles-
2. Capillaries- allow greater
surface area and slows
speed of blood so
exchange can take place
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3. Veins- return blood to
heart under low pressure
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YouTube - Mechanism of Vein
Physiology of
Circulation
Pulse- wave of pressure that
begins in the ventricles and
travels through the arteries
PULSE RATE = HEART RATE
Can be measured in any artery close to
body surface; compress artery
against firm tissue
Assess
– Rate
– Regularity
– Strength
Normal- 70-76 bpm in resting
person
Factors Influencing Pulse– activity
– postural changes
– emotions
Blood Pressure
The pressure the blood exerts
against the inner walls of
blood vessels
It is the force that keeps the
blood circulating between
heartbeats
In other words…
Any system equipped with a
pump that forces fluid
through a network of closed
tubes operates under
pressure.
The closer you get to the
pump, the higher the
pressure.
Blood pressure understood to
mean the pressure within
the large systemic arteries
near the heart
Principles that determine
pressure and flow include:
1.
2.
3.
4.
The heartSize of the vesselSpeed vs. PressureConstriction-
• YouTube - Blood Pressure