404
Chapter 12
the interstitial fl
uid. Absorption from interstitial fl uid to
plasma is favored by the protein concentration difference
between the plasma and the interstitial fl
uid.
b. Filtration and absorption do not change the concentrations
of crystalloids in the plasma and interstitial fl uid because
these substances move together with water.
c. There is normally a small excess of fi ltration over absorption,
which returns fl uids to the bloodstream via lymphatic vessels.
Veins
I. Veins serve as low-resistance conduits for venous return.
II. Veins are very compliant and contain most of the blood in the
vascular system.
a. Sympathetically mediated vasoconstriction refl exly alters
venous diameters so as to maintain venous pressure and
venous return.
b. The skeletal muscle pump and respiratory pump increase
venous pressure locally and enhance venous return. Venous
valves permit the pressure to produce fl ow only toward the
heart.
The Lymphatic System
I. The lymphatic system provides a one-way route for movement
of interstitial fl uid to the cardiovascular system.
II. Lymph returns the excess fl uid fi ltered from the blood vessel
capillaries, as well as the protein that leaks out of the blood
vessel capillaries.
III. Lymph fl ow is driven mainly by contraction of smooth muscle
in the lymphatic vessels, but also by the skeletal muscle pump
and the respiratory pump.
Additional Clinical Examples
I. Disease states that alter the Starling forces can result in edema
(e.g., heart failure, tissue injury, liver disease, kidney disease,
and protein malnutrition).
SECTION C KEY TERMS
absorption
397
active hyperemia
389
angiogenesis
392
angiogenic factors
392
angiotensin II
391
atrial natriuretic peptide
391
bradykinin
389
capillary fi ltration
coeffi cient
399
colloid
397
compliance
385
crystalloid
397
diastolic pressure (DP)
386
endothelin-1 (ET-1)
392
endothelium-derived relaxing
factor (EDRF)
391
fl ow autoregulation
390
fl ow-induced arterial
vasodilation
392
fused-vesicle channel
394
hyperemia
389
intercellular cleft
394
intrinsic tone
389
kallikrein
389
kininogen
389
Korotkoff’s sounds
387
local control
389
lymph
401
lymphatic capillary
401
lymphatic system
401
lymphatic vessel
401
mean arterial pressure
(MAP)
386
metarteriole
394
myogenic response
390
net fi ltration pressure
(NFP)
397
nitric oxide
389
peripheral veins
399
precapillary sphincter
394
prostacyclin (PGI
2
)
391
pulse pressure
386
reactive hyperemia
390
respiratory pump
400
shear stress
392
skeletal muscle pump
400
SECTION C CLINICAL TERMS
SECTION C REVIEW QUESTIONS
1. Draw the pressure changes along the systemic and pulmonary
vascular systems during the cardiac cycle.
2. What are the two main functions of the arteries?
3. What are normal values for systolic, diastolic, and mean arterial
pressures? How is mean arterial pressure estimated?
4. What are two major factors that determine pulse pressure?
5. What denotes systolic and diastolic pressure in the
measurement of arterial pressure with a sphygmomanometer?
6. What are the major sites of resistance in the systemic vascular
system?
7. Name two functions of arterioles.
8. Write the formula relating fl ow through an organ to mean
arterial pressure and to the resistance to fl ow that organ offers.
9. List the chemical factors thought to mediate active hyperemia.
10. Name the mechanism other than chemical factors that
contributes to fl ow autoregulation.
11. What is the only autonomic innervation of most arterioles?
What are the major adrenergic receptors infl uenced by these
nerves? How can control of sympathetic nerves to arterioles
achieve vasodilation?
12. Name four hormones that cause vasodilation or vasoconstriction
of arterioles, and specify their effects.
13. Describe the role of endothelial paracrine agents in mediating
arteriolar vasoconstriction and vasodilation, and give three
examples.
14. Draw a fl ow diagram summarizing the factors affecting
arteriolar radius.
15. What are the relative velocities of fl ow through the various
segments of the vascular system?
16. Contrast diffusion and bulk fl ow. Which mechanism exchanges
nutrients, oxygen, and metabolic end products across the
capillary wall?
17. What is the only solute that has signifi cant concentration
differences across the capillary wall? How does this difference
infl uence water concentration?
18. What four variables determine the net fi ltration pressure across
the capillary wall? Give representative values for each of them
in the systemic capillaries.
19. How do changes in local arteriolar resistance infl uence local
capillary pressure?
20. What is the relationship between cardiac output and venous
return in the steady state? What is the force driving venous
return?
21. Contrast the compliances and blood volumes of the veins and
arteries.
22. What three factors infl uence venous pressure?
23. Approximately how much fl uid do the lymphatics return to the
blood each day?
24. Describe the forces that cause lymph fl ow.
angiostatin
392
arteriosclerosis
386
edema
401
elephantiasis
401
kwashiorkor
403
Starling force
398
systolic pressure (SP)
386
vasoconstriction
389
vasodilation
389
vasopressin
391
previous page 432 Vander's Human Physiology The Mechanisms of Body Function read online next page 434 Vander's Human Physiology The Mechanisms of Body Function read online Home Toggle text on/off