KINE 1102- midterm lecture 4
Basics of blood vessels
Arteries: bring blood away from the heart and relatively oxygenated with the exception of pulmonary circulation
Capillaries: Contact with tissue cells, point of gas exchange
Veins: bring blood towards the heart and relatively deoxygenated
Three main layers of structure of blood vessels
1) Tunica interna
2)Tunica media
3) Tunica externa
Tunica Interna
innermost, associated with endothelia
more wavy in arteries than veins
Tunica Media
Associated with muscle of BV
External elastic lamina (arteries in particular): expand and recoil
smooth muscle larger in arteries than veins
Tunica Externa
provides structural support
made of collagen
larger in veins
arteries have Vasa Vosum: blood vessels that support other vessels with blood
Components of the arterial system
1) elastic arteries
2) muscular arteries
3) Arterioles
Elastic arteries
Largest type
beginning of periphery pushing (conducts)
good amount of elastic fiber and muscular wall
muscular artery
delivers blood to organs, distal from the heart
less elastic and bigger muscular component due to vasoconstriction
Arterioles
smallest
lost less elastic and muscle
fine control of blood flow
last step before going to capillaries
The Venous system
1) Large vein
2) Medium Vein
3) venules
Large vein
end stage of circulatory and closest to the heart
not too much muscle and tunica externa is the largest layer
Medium Veins
Lots of valves
NO ELASTIC
little muscle
Venules
Opposite side of the capillary
very thin
smallest
NO VALVES
Exceptions that have poor capillary supply
Tendons/ligaments
cartilage and epithelia
Meta-Arteriole
Pre capillary sphincter
bridge from arteriole to capillary
controls blood flow in capillary network
Thoroughfare channel
associated with vascular shunting where blood goes through this channel instead of the capillary network
Capillary types
1) continous
2) fenestrated
3) Sinusoidal
Continous
"least leaky"
most common and immpereable to junctions
passage for small molecules through intercellular cleft
Fenestrated
pores, more leaky
permeable to large molecules
common in SI for absorption and filtration
Sinusoid
"swiss cheese"
leakest and has the biggest intercellular gap
passage for really large molecules
slowest blood flow
common in visceral organs
Micro anatomy of the heart
three layers
1) Epicardium: visceral serous pericardium, anchored to muscle wall
2) myocardium: main muscle layer
3) Endocardium: covering turbuclae cardinae
Micro anatomy of myocardium
Cardiac muscle fiber: striated, follows sliding filaments theory
Intercelated disc: cardio mocytes connect to one another creating a junction so they can act as one unit
Desmesomes: Helps hold junctions close together
Gap Junctions: Little channels that allow channel of ions from one muscle cell to another
Mechanism of cardiac contraction: Phase 1
A) Resting membrane potential (-90mv)
everything at rest
more -ve inside and more +ve charge outside
B) Depolarization (-30mv)
Requires sharp change in membrane potential
opening sodium channel for a rush
more -ve outside and more +ve inside
some ions go from myocyte 1-> myocyte 2 through gap junction
Phase 2
C) Plateu Phase
Sodium channels deactivate
potassium ions leak
"dip" in membrane potential
less +ve on inside
maintain +ve potential for longer contraction
D) plateu phase (2)
ca+ slowly go in the cell balancing K+ to maintain MP
Influx of ca+ initiates muscle contraction
Phase 3
E) Repolarization
end plateau phase by deactivating ca+ channel
K+ leaving causing more rapid decrease
-ve inside,+ve outside
F) End of Repolarization
Ionic balance restored
more K+ inside
brings back to resting membrane potential (-90mv)
Absolute Refractory period
Ensures that new actionpotential is not generated until first contraction is complete
skeletal muscle
STIMULATION
Muscle fibers stimulated by
neuron (basic unit of nervous
system)
CONTRACTION Each fiber works alone – no fiberto-fiber connection
All cells work as a team and
contract synchronously as one
REFRACTORY PERIOD 1-2 ms (full contraction 15-100 ms)
Contractions can build (tetany)
Cardiac muscle
STIMULATION
Self-excitable cells (SA node in
heart) stimulate themselves
and pass this along to other
cells (myocytes)
CONTRACTION
All cells work as a team and
contract synchronously as one
REFRACTORY PERIOD
200 ms
no tetany