Download Arteries

Blood Vessels: The Vascular
System

Taking blood to the tissues and back
–Arteries
– Arterioles
– Capillaries
– Venules
–Veins
Figure 11.8a
The Vascular System
Figure 11.8b
Blood Vessels: Anatomy
 Three
layers (tunics)
– Tunic intima—slick, reduces friction
 Endothelium
– Tunic media—changes diameter
 Smooth muscle
 Controlled by sympathetic nervous
system
– Tunic externa—supports and protects
 Mostly fibrous connective tissue
Differences Between Blood
Vessel Types
 Walls
of arteries are the thickest
 Lumens of veins are larger
 Skeletal muscle “milks” blood in
veins toward the heart
 Walls of capillaries are only one
cell layer thick to allow for
exchanges between blood and
tissue
Movement of Blood Through
Vessels
Most arterial blood
is pumped by the
heart
 Veins use the
milking action of
muscles to help
move blood
 Breath and pressure
drops in thorax,
vessels fill

Figure 11.9
Capillary Beds
 Capillary
beds
consist of two
types of vessels
–Vascular shunt –
directly connects
an arteriole to a
venule
Figure 11.10
Capillary Beds
 True
capillaries –
exchange vessels
Oxygen and
nutrients cross
to cells
Carbon dioxide
and metabolic
waste products
cross into blood
Figure 11.10
Problems in our veins

Varicose Veins—
– Pooling of blood in feet and legs, poor venous
return (low pressure on veins from lack of
movement)
– THROMBOPHLEBITIS—complication of
varicose veins…inflammation in vein from clot
that forms in vessel
– PULMONARY EMBOLISM—clot breaks loose
and lodges in pulmonary circulation.
Varicose Veins
Major Arteries of Systemic Circulation
Figure 11.11
Major Veins of Systemic Circulation
Figure 11.12
Arterial Supply of the Brain
Figure 11.13
Arterial supply to the Brain
 Arteries-
Internal Carotid branch to:
–Anterior cerebral arteries
–Middle cerebral arteries
----These supply most of
cerebrum
 Vertebral
Arteries--up base of
neck.
 Within Skull, join to form one
Basilar Artery
–Serves brain
stem/cerebellum
–Divides at base of cerebrum,
form POSTERIOR CEREBRAL
ARTS.
Circle of Willis
CIRCLE OF WILLIS
 Complete
circle of
connecting blood vessels
 Protects brain
 Provides more than 1 route
in case of blockage
Hepatic Portal Circulation
Figure 11.14
HEPATIC PORTAL CIRC.
Digestive
organs,
spleen, pancreas-blood drained and
sent to liver thru
HEPATIC PORTAL
VEIN
Liver
maintains glucose,
fat, protein
concentrations
Liver then emptied by
hepatic veins to Inferior
Vena Cava
Circulation to the Fetus
Figure 11.15
Circulation to the Fetus
Figure 11.15
Fetal Circulation
 Nutrient,
excretory, gas
exchanged thru placenta
 Umbilical cord has 3 vessels
–1 large umb. Vein-nutrients and O2 to fetus
2
smaller umb. Arteries--CO2 and
waste from fetus to placenta
 Baby blood bypasses own liver
thru DUCTUS VENOSUS--goes to
RA
2
SHUNTS prevent blood flow
to lungs
–Foramen Ovale--flap from RA
to LA, closes at birth
–Ductus Arteriosus--vessel
from pulmonary trunk to
aorta, collapses at birth,
converted to ligamentum
arteriosum
Transposition of the Great Arteries
Congenital heart defect in which the
Pulmonary artery and Aorta are attached
to the opposite ventricles
 Can be corrected with SURGERY

Pulse
Pulse – pressure
wave of blood
 Monitored at
“pressure points”
where pulse is
easily palpated

Figure 11.16
Blood Pressure

Measurements by health professionals are
made on the pressure in large arteries
– Systolic – pressure at the peak of ventricular
contraction
– Diastolic – pressure when ventricles relax

Pressure in blood vessels decreases as the
distance away from the heart increases
Measuring Arterial Blood
Pressure
Figure 11.18
Comparison of Blood Pressures in
Different Vessels
Figure 11.17
Blood Pressure: How is it
Controlled????

Neural factors
– Autonomic nervous system adjustments
(sympathetic division)
– Causes vasoconstriction = increases pressure
 When we suddenly stand up, blood pools in legs
and feet
 Pressure drops, PRESSORECEPTORS in large
arteries in neck/chest signal vasoconstriction to
body.
 Fight
or Flight
–Generalized vasoconstriction
EXCEPT in our skeletal
muscles…these dilate to allow more
blood to the working muscles.
Blood Pressure: Effects of
Factors

Temperature
– Heat has a vasodilation effect
– Cold has a vasoconstricting effect

Chemicals
– Various substances can cause increases or
decreases

Diet
Variations in Blood Pressure

Human normal range is variable
– Normal
 140–110 mm Hg systolic
 80–75 mm Hg diastolic
– Hypotension
 Low systolic (below 110 mm HG)
 Often associated with illness
– Hypertension
 High systolic (above 140 mm HG)
 Can be dangerous if it is chronic
Capillary Exchange

Substances exchanged due to
concentration gradients
– Oxygen and nutrients leave the blood
– Carbon dioxide and other wastes leave the
cells
Diffusion at Capillary Beds
Figure 11.20
Capillary Exchange:
3 Mechanisms
Direct diffusion across plasma membranes
 Some capillaries have gaps (intercellular
clefts)

– Plasma membrane not joined by tight
junctions

Fenestrations of some capillaries
– Fenestrations = pores