1
Q
The circulatory system includes…
A
- heart
- arteries
- arterioles
- capillaries
- venules
- veins
Lymph vessels are also included
2
Q
What are the typical layers of a blood vessel?
A
- tunica intima
- tunica media
- tunica adventitia
3
Q
What is the major difference between elastic and muscular arteries?
A
Composition of the tunica media
- elastic arteries contain many concentric sheets of elastin
- muscular arteries only have a few fibers
4
Q
How many layers of smooth muscle do arterioles have?
A
3 or fewer
5
Q
How is flow regulated through capillary beds (microcirculation) ?
A
by precapillary sphincters at the arteriole-capillary junction
6
Q
What allows blood to bypass the capillary beds?
A
arteriovenous shunts
7
Q
endocardium
A
- endothelium
- some supporting connective tissue
- adipose tissue deposits in places
8
Q
myocardium
A
- muscle of the heart
- contains cardiac myocytes and purkinje fibers
9
Q
epicardium
A
- adventitia
- contains mesothelium that secretes serous fluid
- some supporting CT like in endocardium
- broad layer of adipose tissue
10
Q
pericardium
A
outer membrane
11
Q
Purkinje fibers
A
- conduction system
- derived from cardiac muscle
- cells are larger than muscle fiber
- no T-tubules
12
Q
What connective tissue can be found in the endocardium?
A
- delicate collagenous layer
- deeper fibroelastic layer
13
Q
cardiac skeleton
A
- fibrous skeleton of heart
- annulus
- trigone
14
Q
What is the fibrous skeleton of the heart?
A
dense CT in heart that separates the atria from the ventricles
15
Q
Annulus
A
surround valves in the heart
16
Q
Trigone
A
triangular area between the two AV canals and aortic valve
17
Q
Heart valves
A
- folds of endocardium
- supported by cardiac skeleton
- edges of cusps of valves anchored by chordae tendineae
18
Q
tunica intima
A
- can have 3 layers
- endothelium = always
- subendothelial connective tissue = +/-
- internal elastic lamina = +/-
19
Q
tunica media
A
- smooth muscle of vessel
- varying amounts of elastic laminae
- external elastic lamina = difficult to see usually
20
Q
tunica adventitia
A
- connective tissue of vessel wall
- dense or loose CT
- larger vessels also have a blood and nerve supply for that vessel
21
Q
vasa vasorum
A
- blood supply for the larger blood vessel
- located in the tunica adventitia
- too large to just pull what blood they need from the blood going through them
22
Q
nervi vasorum
A
- nerve supply for the larger blood vessels
- located in the tunica adventitia
23
Q
tunica intima of elastic arteries
A
- most inner layer, just inside endothelium
- very thin layer = may be difficult to observe
- usually contains fibroblasts and myointimal cells
24
Q
What do myointimal cells do as they age?
A
deposit lipid and thicken
25
What is atherosclerosis?
disease of the arteries characterized by the deposition of plaques of fatty material on their inner walls
26
tunica media of elastic arteries
- thickest layer
- many concentric layers of elastin
- smooth muscle cells and reticular fibers between layers
- external elastic lamina is not readily apparent
27
In comparison with the tunica media, the tunica adventitia of elastic arteries is...
thin
28
tunica intima of muscular arteries
- endothelium
- CT
- IEL
29
tunica media of muscular arteries
- thick layer of smooth muscle
| - contains fibers and proteoglycans
30
What is the external elastic lamina? Where is it in muscular arteries?
- made of elastin fibers
| - divides tunica media and adventitia
31
tunica adventitia of muscular arteries
- external CT layer
| - can be very thick
32
Can the tunica intima be seen for muscular arteries under normal conditions with a light microscope?
- Not really = difficult with light microscope and normal conditions
- However it is visible in pathological conditions such as atherosclerosis
33
What happens when the vascular intima becomes thicker?
| Why is this a problem?
- Increases peripheral blood pressure
| - Leads to hypertension, coronary artery disease, stroke, aneurysm, etc.
34
Differences between small muscular arteries and arterioles?
SMA
- greater than 3 layers of muscle cells
Arterioles
- no external elastic lamina
- diminishing internal elastic lamina
- 3 or less layers of muscle cells
35
Arterioles
- smallest branch of arterial system
- delivers and regulates blood flow to the capillary beds
- regulates systemic blood pressure
36
How do arterioles regulate systemic blood pressure?
Through constrictions of arterioles, which increases resistance to peripheral blood flow
37
Layers of Arterioles
- tunica intima = present
- internal elastic lamina = disappearing
- tunica media = 1-3 layers of smooth muscle cells
- tunica adventitia = narrow layer of connective tissue
38
What kind of cells produce nitric oxide?
| What does nitric oxide do?
- produced by vascular endothelial cells and macrophages
| - potent vasodilator = open arteries/arterioles up and lowers blood pressure
39
What layers are found in capillaries?
endothelium and basement membrane
40
What types of capillaries are there?
- continuous
- fenestrated
- discontinuous
- sinusoidal
41
What is the diameter of a capillary?
Generally about the same as a RBC (7-9 micrometers)
Sinusoids are much larger at 30-40 micrometers (5x the size of RBC!) and are found in the liver, spleen, lymph nodes, and bone marrow
42
Why are capillaries so thin?
To allow for exchanges
- water and solutes between blood and tissues (tissue beds)
- between blood and environment (lung)
43
Continuous capillaries
- no pores in endothelial cells
| - most common types = muscle, brain, thymus, bone, lung
44
Fenestrated (windowed) capillaries
- have pores w/in endothelial cells (+/- diaphragm)
| - found in tissues with substantial fluid transport: intestine, kidney, endocrine glands
45
Sinusoids
- special capillaries found in the liver, spleen, and bone marrow
- have wide lumen
- incomplete basal lamina
46
Discontinuous capillaries
- found in liver and spleen
| - have discontinuous endothelium = gaps between the endothelial cells themselves
47
What is microcirculation?
- interaction of arterioles and venules through capillaries at peripheral tissues
- for gas, nutrients, fluid, and metabolic waste exchange
48
How is blood flow in capillary circulation controlled/
- autonomic nervous system
- circulating hormones
- precapillary sphincters
49
Layers of Venules
- tunica intima =endothelium only
- tunica media = thin or not present
- tunica adventitia = present
50
Blood flow through a capillary bed
arterioles -> capillaries -> post-capillary venule -> collecting venule ->muscular venule
51
Layers of Veins
- tunica intima = present
- tunica media = few layers of smooth muscle; may be discontinuous; irregularly arranged
- tunica adventitia = thickest part
52
Keys to differentiating arteries from veins
- veins and venules have a thinner wall for all layers
- compare them = arteries and veins often found together, same with arterioles and venules
- most arteries do not have valves; many veins have valves
53
Why can it be a problem that lymph vessels are a very low pressure system?
- easily occluded, obstructed, or overwhelmed
| - leads to edema
54
Why do lymph vessels have valves?
help assure fluid continues toward large veins cranial to the heart
55
What does it mean that the lymph system is a one-way system?
- smallest lymph vessels (lymph capillaries) are blind-ended
| - begin in the perivascular space in the tissue beds
56
Function of Lymph Vessels?
- transport excess interstital fluid, proteins, solutes, and macromolecules through lymph nodes and back to venous system
- safety valve between extravascular and intravascular fluid pools
- filtering system to impede microorganisms and cancer cells
57
What do lymph vessels look like on a slide?
- no basement membranes
- endothelium only
- look like a space in the tissue = look for the endothelium
- have valves
- thinner walls than veins of similar size
- should NOT fnd RBCs in lymph vessels
58
Circulatory Shock
- acute symptom
- life-threatening
- widespread inadequacy of tissue perfusion
- hypovolemia of 25% or greater can lead to it = can be due to blood loss or extreme vasodialtion by endotoxin, etc.
59
What damage does circulatory shock do?
- cellular hypoxia
- cellular injury
- organ damage
- lactic acidosis = lactic acid released from damaged cells
60
How does peripheral vasoconstriction relate to circulatory shock?
- compensation for circulatory shock
- preserves blood flow to vital organs
- decreases capillary hydrostatic pressure to facilitate the flow of interstital fluid into the circulation
Microanatomy 1
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