1. Chapter 19 – Vascular System
BIOL 2304 Fall 2008
Chapter 19

2. A. categories and general functions:
1. arteries - carry blood
away from heart
2. capillaries - allow
exchange of materials
between blood and
tissue fluid
3. veins - return blood
to heart
BIOL 2304 Fall 2008
Chapter 19

3. BIOL 2304 Fall 2008
Chapter 19

4. most vessel walls have 3 layers
B. wall structure
most vessel walls have 3 layers
lumen = space inside vessel
1. tunica intima / tunica interna
endothelium –
simple squamous e.
subendothelial layer –
loose c.t. (collagen)
BIOL 2304 Fall 2008
Chapter 19

5. a. smooth muscle - cells circularly arranged
2. tunica media
a. smooth muscle - cells circularly arranged
controlled by ANS and chemical factors
constriction decreases blood flow and increases systemic blood pressure
dilation increases blood flow and decreases systemic blood pressure
b. elastic c.t.
BIOL 2304 Fall 2008
Chapter 19

6. 3. tunica adventitia / tunica externa
c.t. attaches vessel to surrounding structures
vasa vasorum nourish outer part of vessel wall
BIOL 2304 Fall 2008
Chapter 19

7. C. arteries
1. elastic (conducting) - large arteries near heart (aorta and major branches)
* conduct blood to muscular arteries
* low resistance
* tunica media = circular elastin sheets with few smooth m. cells
* recoil maintains blood pressure during diastole
BIOL 2304 Fall 2008
Chapter 19

8. 2. muscular - middle-sized arteries, distal to elastic arteries
* tunica media very thick; much smooth m. and some elastin
* regulate blood flow to organs
* have an internal and an external elastic lamina
BIOL 2304 Fall 2008
Chapter 19

9. 3. arterioles - smallest arteries
* tunica media contains smooth m. only
* diameter controlled by ANS and chemical messengers
* diameter determines blood flow and blood pressure
BIOL 2304 Fall 2008
Chapter 19

10. D. capillaries
* wall consists of endothelium and basal lamina (no tunica media or externa)
* 8 to 10 mm in diameter
* join and branch to form capillary beds
* cells are joined at spots around perimeter by tight junctions and desmosomes
* intercellular clefts are spaces between cells
BIOL 2304 Fall 2008
Chapter 19

11. a. fenestrated capillaries (high permeability)
1. types
a. fenestrated capillaries (high permeability)
* have fenestra (openings) in endothelial cells
* some fenestra are covered by a membrane, others are not
* also have intercellular clefts
* found in small intestine, synovial joints, kidney
BIOL 2304 Fall 2008
Chapter 19

12. b. continuous capillaries * intercellular clefts but no fenestra
* most common type
c. sinusoids
* wide, leaky capillaries, usually fenestrated
* fewer cell junctions
* allow passage of large particles
* found in bone marrow, spleen, liver
BIOL 2304 Fall 2008
Chapter 19

13. d. low-permeability capillaries
* complete tight junctions
* no fenestra, no clefts
* restricted transport vesicles
* can transport specific molecules in or out
* found in brain (blood-brain barrier)
BIOL 2304 Fall 2008
Chapter 19

14. * controls blood flow through capillaries
2. capillary beds
precapillary sphincter - smooth m. cell wrapped around origin of capillary
* controls blood flow through capillaries
* sphincter controlled by autoregulation
* when sphincter is closed, blood is diverted to thoroughfare channel
BIOL 2304 Fall 2008
Chapter 19

15. E. veins
have thinner walls than arteries for the same diameter (larger lumen)
act as capacitance vessels - store extra blood (65%)
low pressure
tunica adventitia thicker than tunica media
venous valves prevent backflow
BIOL 2304 Fall 2008
Chapter 19

16. F. vascular anastomosis
occurs when vessels join midstream
anastomoses provide alternate pathways (collateral channels)
BIOL 2304 Fall 2008
Chapter 19

17. G. circulatory routes
1. pulmonary circuit: right ventricle to lungs to left atrium
* pressure supplied by right ventricle
* low pressure system
* takes low oxygen blood (75% saturated) to lungs and brings high oxygen (98%
saturated) blood
back to heart
BIOL 2304 Fall 2008
Chapter 19

18. pulmonary semilunar valve pulmonary trunk
right ventricle
pulmonary semilunar valve
pulmonary trunk
left and right pulmonary arteries
lobar arteries (3 R, 2 L) take blood to lung lobes
pulmonary capillaries
pulmonary veins (superior and inferior, L and R)
left atrium
BIOL 2304 Fall 2008
Chapter 19

19. 2. systemic circuit: left ventricle to body to right atrium
* pressure supplied by left ventricle
* high pressure system
* takes O2 to tissues and removes CO2
* distributes nutrients from digestive tract to body
* collects wastes and takes them to kidney for excretion
BIOL 2304 Fall 2008
Chapter 19

20. a. circulatory pathways of the brain (cerebral arterial circle, circle of Willis)
BIOL 2304 Fall 2008
Chapter 19

21. anterior communicating a. anterior cerebral a. internal carotid a.
posterior communicating a.
posterior cerebral a.
basilar a.
vertebral a.
BIOL 2304 Fall 2008
Chapter 19

22. cross section of neck:
BIOL 2304 Fall 2008
Chapter 19

23. b. hepatic portal circulation
portal system = two capillary beds in series, joined by veins or arteries
BIOL 2304 Fall 2008
Chapter 19

24. BIOL 2304 Fall 2008
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25. capillaries of small intestine, part of large intestine and stomach
superior mesenteric vein
capillaries of spleen, stomach and pancreas
splenic vein
capillaries of distal large intestine and rectum
inferior mesenteric vein
BIOL 2304 Fall 2008
Chapter 19

26. hepatic portal vein liver liver sinusoids hepatic veins
inferior vena cava
BIOL 2304 Fall 2008
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27. c. fetal circulation
placenta = organ formed from extra-embryonic membranes and endometrium to exchange materials between fetal and maternal blood
the umbilical veins take high-oxygen and high-nutrient blood from the placenta to the fetus
the umbilical arteries take low-oxygen, high-waste blood back to the placenta
BIOL 2304 Fall 2008
Chapter 19

28. umbilical vein from placenta
  fetal liver
hepatic portal vein
ductus venosus
inferior vena cava
right atrium foramen ovale left atrium
right ventricle left ventricle
pulmonary trunk ductus arteriosus aorta
lungs
  internal iliac a.
umbilical a. to placenta
BIOL 2304 Fall 2008
Chapter 19

29. 1) to bypass the fetal liver
adaptations:
1) to bypass the fetal liver
ductus venosus - allows some umbilical vein blood to go through the fetal liver but diverts most of it directly into the inferior vena cava
2) to bypass the non-functional fetal lungs
foramen ovale – opening in interatrial septum that allows blood to go from the right atrium directly into the left atrium
ductus arteriosus – vessel that connects pulmonary trunk and aorta
BIOL 2304 Fall 2008
Chapter 19

30. BIOL 2304 Fall 2008
Chapter 19