Transcript Ch 11 Anatomy of Blood Vessels

Pages 370-379

Flow is unidirectional

Vessels that carry blood away from the heart:
(from largest to smallest)
◦ Arteries > arterioles > Capillary beds


exchanges between tissues and blood take place at the
capillary beds
Vessels that return blood toward the heart:
◦ Venules and veins
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
Three tissue layers (tunics) in blood vessels
from deep to superficial:
◦ Tunica intima- innermost endothelium
◦ Tunica media- middle smooth muscle
◦ Tunica externa- outermost fibrous connective

All vessels possess this arrangement except
capillaries
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
Arteries:
◦ thicker tunica media for larger volume and pressure
◦ Stronger and more elastic

Capillaries: one cell layer thick for diffusion
between blood and tissues

Veins:
◦
◦
◦
◦
◦
thinner tunica media than arteries
operate under low pressure
valves to prevent backflow of blood against gravity
Larger lumen (channel)
Skeletal muscle helps move blood toward the heart
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Artery
Tunica intima
• Endothelium
• Loose connective tissue
Vein
Tunica media
• Smooth muscle
Tunica externa
• Collagen fibers
Valve
Arteriole
Lumen
Venule
Capillary
network
Lumen
Basement membrane
Endothelial cells
(b)
Capillary
Valve (open)
Contracted
skeletal
muscle
Valve (closed)
Vein
Direction of
blood flow
Precapillary sphincters
Vascular shunt
True
capillaries
Terminal arteriole
Postcapillary
venule
(a) Sphincters open; blood flows through
true capillaries.
Terminal arteriole
Postcapillary
venule
(b) Sphincters closed; blood flows through
vascular shunt.

Varicose veins:
◦ structural defect due to incompetent valves
◦ Common in people who:
 Are obese
 stand for long periods of time
◦ Predisposing factor for thrombophlebitis:
inflammation of a vein resulting from a clot
 can lead to pulmonary embolism
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
circulation between the heart and tissues
◦ Aorta (oxygenated blood)
 Largest artery in the body
 Leaves from the left ventricle of the heart
◦ Superior and inferior venae cavae (deoxygenated)
 enter the right atrium of the heart
 Superior drains the head and arms
 Inferior drains the lower body
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Superior vena cava
Aorta
Left atrium
Right atrium
Right ventricle
Inferior vena cava
Left ventricle

CEREBRUM:
◦ Blood supply branches from
 internal carotid arteries
 Basilar artery

BRAIN STEM AND CEREBELLUM:
◦ Blood supply branches from
 Basilar artery

This system of arteries branches to form a circle
which supplies the major brain structures
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Anterior
Frontal lobe
Cerebral arterial circle
(circle of Willis)
Internal carotid
artery
Temporal lobe
Pons
Basilar artery
Vertebral artery
Occipital lobe
(a)
Cerebellum
Posterior
(b)

sends blood from certain organs (digestive,
pancreas, spleen) for processing by the liver

The hepatic portal vein is the transport vessel

After nutrients are removed and stored, blood
is returned to systemic circulation
◦ via the hepatic portal vein to the inferior vena cava

veins are supplying the liver with blood for
processing while arteries supply the liver with
oxygen
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Arterial
blood
Venous
blood
Inferior
vena cava
Stomach and intestine
Nutrients and
toxins absorbed
Liver
Liver cells (hepatocytes)
Nutrients
and toxins
leave
Hepatic
portal vein
First capillary bed
Second capillary bed
Hepatic
(liver sinusoids)
vein
Hepatic portal system
Inferior vena cava
(not part of hepatic
portal system)
Liver
Hepatic
portal vein
Gastric veins
Spleen
Stomach
Splenic vein
Inferior
mesenteric vein
Superior
mesenteric vein
Small
intestine
Large intestine
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