1. Blood Vessels: Organization and Microscopic Anatomy
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2. Blood Vessels: The transport system
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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3. Microscopic Anatomy of Blood Vessels
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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4. Structural Differences between Arteries, Capillaries & Veins
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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5. Figure 11.10b Structure of blood vessels.
Tunica intima
Artery
Vein
• Endothelium
• Loose connective tissue
Tunica media
• Smooth muscle
Tunica externa
• Collagen fibers
Valve
Venule
Arteriole
Capillary
network
Lumen
Lumen
Basement membrane
Endothelial cells
(b)
Capillary

6. Figure 11.11 Operation of the muscular pump.
Valve (open)
Contracted
skeletal
muscle
Valve (closed)
Vein
Direction of
blood flow

7. Figure 11.12a Anatomy of a capillary bed.
Vascular shunt
Precapillary sphincters
True
capillaries
Terminal arteriole
Postcapillary
venule
(a)
Sphincters open; blood flows through
true capillaries.

8. Figure 11.12b Anatomy of a capillary bed.
Terminal arteriole
Postcapillary
venule
(b)
Sphincters closed; blood flows through
vascular shunt.

9. Homeostatic Imbalance
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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10. Major Vessels of Systemic Circulation
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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11. Superior vena cava
Aorta
Left atrium
Right atrium
Left ventricle
Right ventricle
Inferior vena cava

12. Arterial Supply of: the Brain and the Circle of Willis
CEREBRUM:
Blood supply branches from
internal carotid arteries
Basilar artery
BRAIN STEM AND CEREBELLUM:
This system of arteries branches to form a circle which supplies the major brain structures
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13. Figure 11.15a Arterial supply of the brain.
Anterior
Cerebral arterial circle
(circle of Willis)
Frontal lobe
Internal carotid
artery
Temporal lobe
Basilar artery
Pons
Vertebral artery
Occipital lobe
Cerebellum
(a)
Posterior

14. Figure 11.15b Arterial supply of the brain.

15. Hepatic Portal Circulation- dual blood supply
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
© 2015 Pearson Education, Inc.

16. Figure 11.16 The basic scheme of the hepatic portal system.
Arterial
blood
Venous
blood
Inferior
vena cava
Stomach and intestine
Liver
Nutrients and
toxins absorbed
Liver cells (hepatocytes)
Nutrients
and toxins
leave
Hepatic
portal vein
First capillary bed
Second capillary bed
(liver sinusoids)
Hepatic
vein
Hepatic portal system

17. Figure 11.17 The hepatic portal circulation.
Inferior vena cava
(not part of hepatic
portal system)
Gastric veins
Liver
Spleen
Stomach
Hepatic
portal vein
Splenic vein
Inferior
mesenteric vein
Superior
mesenteric vein
Small
intestine
Large intestine

18. Hepatic Portal Circulation Animation
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