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CRRAB Week 2 > Blood Vessel Histology > Flashcards

Blood Vessel Histology Flashcards

1
Q

What are the three layers of a blood vessel?

A
  1. Tunica intima
  2. Tunica media
  3. Tunica adventitia
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2
Q

What innervates blood vessels? What NT do these nerves release? How do they propagate impulses?

A
  • Postganglionic, unmyelinated sympathetic fibers (stimulation causes contraction)
  • They release NE
  • Impulses propagated via gap junctions
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3
Q

What is different between the structure of an artery and a vein?

A

Arteries have an elastic membrane between the tunica intima and the tunica media.

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4
Q

What are the three layers of the heart wall?

A

Innermost to outermost:

  1. Endocardium
  2. Myocardium
  3. Epicardium
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5
Q

What are examples of elastic (conducting) arteries? How do they look in fresh specimens?

A
  • Aorta; common carotid & subclavian arteries; common iliac arteries; pulmonary trunk
  • Sometimes appear yellowish in fresh specimens due to abundance of elastin in arterial walls
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6
Q

What to know about the tunica intima of elastic arteries?

A
  • Endothelium
  • -Elongated endothelial cells; oriented in longitudinal plane
  • -Cells connected by occluding junctions
  • -Small vesicles associated with plasma membrane: transport of water, electrolytes, macromolecules
  • -Weibel-Palade bodies
  • Narrow layer of underlying connective tissue
  • Internal elastic lamina
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7
Q

What are Weibel-Palade bodies?

A
  • Arterial endothelial cells
  • Contain von Willebrand factor
  • associated with tunica intima of arteries
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8
Q

What to know about the tunica media of elastic arteries?

A
  • Many fenestrated lamellae of elastin (gaps between)
  • Circularly arranged smooth muscle bundles alternate with elastin
  • Elastin tends to be the dominant component
  • Extracellular matrix produced by smooth muscle cells
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9
Q

What to know about the tunica adventitia of elastic arteries?

A
  • Relatively thin
  • Contains vasa vasorum (blood vessels of the blood vessels)
  • -Capillary beds spring from these vessels and supply the tunica media
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10
Q

What is wider in an elastic artery than other vessels?

A

Tunica intima

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11
Q

What are the components of the tunica media?

A
  • Smooth muscle
  • Collagenous fibers
  • Elastic membrane (with windows)
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12
Q

What do sheets of elastin look like?

A

Pink, thick wavy structures

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13
Q

What are muscular (distributing) arteries?

A

Most of named arteries fall into this category

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14
Q

What is the chief characteristic of muscular (distributing) arteries?

A

Thick tunica media comprised primarily of smooth muscle cells

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15
Q

What to know about the tunica intima of muscular (distributing) arteries?

A
  • Thinner than that of elastic arteries

- Prominent internal elastic lamina; undulating contour

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16
Q

What to know about the tunica media of muscular (distributing) arteries?

A
  • Smooth muscle cells circumferentially arranged are the predominate component
  • 3-40 layers of smooth muscle
  • Smooth muscle cells produce the extracellular matrix
  • External elastic lamina present in the larger muscular arteries
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17
Q

What to know about the tunica adventitia of muscular (distributing) arteries?

A
  • Connective tissue components with some thin elastic laminae present
  • -Connective tissue components produced by fibroblasts
  • Vasa vasorum present
  • Unmyelinated nerve endings present
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18
Q

What is the size of arterioles?

A
  • Typical diameter of = 0.1 mm

- Wall diameter is often about the same as the lumen diameter

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19
Q

What are the three layers of arterioles?

A
  • Tunica intima: endothelium; thin layer of c.t.; sometimes an internal elastic lamina
  • Tunica media: 1-3 layers of smooth muscle
  • Tunica adventitia: scant; produced by fibroblasts
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20
Q

On a slide, how does an arteriole look different than a venule?

A

Arteriole has much thicker walls than venule. Venule is much wider, larger lumen and is filled with more blood in general.

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21
Q

What are metarterioles?

A
  • Smooth muscle cells are not continuous
  • Smooth muscle cells can act as sphincters
  • Control blood flow into capillary bed by encircling the arteriole adjacent to where a capillary arises from the arteriole
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22
Q

What are three specialized sensory structures in arteries?

A
  1. Carotid sinuses
  2. Carotid bodies
  3. Aortic bodies
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23
Q

What are carotid sinuses?

A
  • Baroreceptors (perceive changes in blood pressure)
  • In walls of internal carotid arteries (just above bifurcation of common carotid arteries)
  • Adventitia is thick and innervated by sensory fibers of cranial nerve IX (glossopharyngeal)
  • Tunica media thin: blood vessels distend with increasing blood pressure –> stimulates nerve endings
  • Adjustments made in vasoconstriction to maintain proper blood pressure
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24
Q

What are carotid bodies?

A
  • Chemoreceptors
  • Located at bifurcation of common carotid arteries
  • Special chemoreceptor nerve endings monitor changes in oxygen, carbon dioxide, and hydrogen ions in blood
  • Sensory (afferent) fibers supplied by glossopharyngeal and vagus nerves
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25
Q

What are aortic bodies?

A
  • Chemoreceptors
  • Located on arch of aorta between right subclavian and right common carotid an between left common carotid and left subclavian
  • Same structure and function as carotid bodies
26
Q

What to know about capillaries?

A
  • Usually short; 8-10 microns in diameter
  • Single layer of elongated simple squamous endothelial cells
  • -Long axis in direction of blood flow
  • -Vimentin and desmin have been identified in cells
  • -Pinocytotic vesicles associated with cell membrane
  • -Joined together by fascia occultness
  • -External surface covered by a basal lamina
27
Q

Where does leukocyte migration occur most often?

A

-Almost all leukocytes migrate from lumen of vessel to adjacent connective tissue - post-capillary venule is place where this occurs most often

28
Q

What are pericytes and what do they do?

A
  • Found outside small capillaries and small venues
  • Processes run circumferentially and longitudinally around capillary
  • Sometimes form gap junctions with endothelial cells
  • Probably contractile and help regulate blood flow through capillaries
  • May give rise to smooth muscle cells or endothelial cells
29
Q

What are the three main types of capillaries?

A
  1. Continuous capillaries
  2. Fenestrated capillaries
  3. Sinusoidal capillaries
30
Q

What to know about continuous capillaries?

A
  • No interruptions (pores/fenestrae) in walls
  • Found in muscle, nervous and connective tissues
  • Cells joined by fasciae occludentes
31
Q

What to know about fenestrated capillaries?

A
  • Pores (fenestrae) in capillary walls
  • -Pores covered by thin diaphragm
  • -Pores occur in clusters
  • Found in pancreas, intestines, and endocrine glands
32
Q

What to know about sinusoidal capillaries?

A
  • Irregularly shaped blood pools or channels
  • Larger diameter than other capillary types
  • Contain many fenestrae (without diaphragms); endothelial wall may be discontinuous
  • -larger pores
  • Basal lamina is discontinuous
  • Found in bone marrow, liver, spleen, lymphoid organs and some endocrine glands
33
Q

Where are continuous capillaries found?

A
  • Muscle
  • Connective tissue
  • CNS
34
Q

Where are fenestrated capillaries found?

A
  • Kidney glomeruli
  • Endocrine glands
  • Intestinal villi
  • Exocrine pancreas
35
Q

Where are sinusoidal capillaries found?

A
  • Liver
  • Spleen
  • Bone marrow
  • Lymph nodes
36
Q

What are arteriovenous anastomses?

A
  • Occur where an artery joins a venous channel
  • If shunt is open, blood largely bypasses capillary bed
  • If shunt is closed, blood enters capillary bed
  • Play an important role in thermoregulation
37
Q

What are the three segments of arteriovenous anastomses?

A
  • Arterial segment (structure similar to that of an artery)
  • Intermediate sement: richly innervated with adrenergic and cholinergic nerve fibers
  • Venous segment (structure similar to that of a vein)
38
Q

What are the parts of the central channel?

A
  • Metarterioles (proximal component of central channel): have precapillary sphincters
  • -Contraction of sphincters allows blood to bypass true capillaries and enter thoroughfare channels directly
  • Capillary bed (middle component of central channel)
  • Thoroughfare channel (distal component of central channel)
  • -Drains into venule
39
Q

What is capillary histophysiology?

A
  • Vesicle transport; transcytosis
  • Leukocyte adhesion and diapedesis
  • -Leukocytes bind to endothelium and pass through endothelium to extravascular spaces
  • -Selectins (P,E,L)
  • -Integrins
  • -Other molecules
40
Q

What are the steps of leukocyte recruitment?

A

1a. Attachment
1b. Rolling
2. Activation
3. Arrest & adhesion strengthening
4. Transendothelial migration
- Selectins are present from 1a-3
- Chemoattractants are present from 2-4
- Integrins are present from 2/3-4

41
Q

What else are capillaries involved in? (histophysiology)

A
  • Inflammation & capillary permeability (histamine & bradykinin)
  • Synthetic activities: broad capabilities
  • Enzymes for conversion of angiotensin I to angiotensin II
  • Lipoprotein breakdown into fatty acids and triglycerides in adipose tissue
42
Q

How many and how large are veins?

A
  • Outnumber arteries
  • Lumen diameter larger
  • ~70% of blood volume found in veins
  • Parallel arteries
  • Walls tend to collapse due to thinness
  • Layers: tunica intima; tunica media; tunica adventitia
43
Q

What are post capillary venules?

A
  • Receive blood from capillary bed
  • Similar to capillaries
  • -Thin endothelium surrounded by pericytes
  • -In section look very much like sinusoidal capillaries
  • Preferred site for emigration of leukocytes from vessel lumen into tissue spaces
44
Q

What are Larger Venules?

A
  • Pericytes replaced by smooth muscle
  • Smooth muscle cell investment increases as venules get larger
  • Much material exchanged between vascular compartment and extravascular compartment
45
Q

What lines the larger venules?

A

Simple squamous endothelial cells

46
Q

As veins get larger, pericytes are replaced with. . .

A

smooth muscle, wrapped circumferentially around venule

47
Q

What are High endothelial venules (HEVs)?

A
  • Specialized versions of small venues found in some lymphatic organs
  • Endothelium is cuboidal rather than squamous
  • Allow for migration of specific types of leukocytes through the endothelial wall into the lymphoid parenchyma
48
Q

What are the three types of venules & small veins?

A
  1. Postcapillary venules
  2. Larger venules
  3. High endothelial venules (HEVs)
49
Q

How large are medium veins and what do they have that smaller veins do not?

A
  • Less than 1 cm in diameter

- Many medium veins have valves

50
Q

What are the three layers of medium veins?

A
  1. Tunica intima: endothelium; basal lamina; some reticular fibers
  2. Tunica media: smooth muscle cells intermingled with collagen fibers and fibroblasts
  3. Tunica adventitia: thickest layer; collagen and elastic fibers
    - Adventitia is MUCH thicker than in arteries
51
Q

What are examples of large veins?

A

Venae cavae; pulmonary, portal, renal, internal jugular, iliac, and azygous veins

52
Q

What are the three layers of large veins?

A
  1. Tunica intima: endothelium and a thick sub endothelial layers with elastic fibers
  2. Tunica media: not well developed– often apparent
  3. Tunica adventitia: collagen fibers; abundant elastic fibers; vasa vasorum; longitudinally disposed SMOOTH MUSCLE BUNDLES (e.g., inferior vena cava)
53
Q

What are Varicose veins?

A
  • Abnormally enlarged and tortous veins
  • Usually affect superficial veins in legs of older individuals
  • -Due to loss of muscle tone; wall degeneration; valvular incompetence
  • Other common locations: lower esophagus (esophageal varices); terminus of anal canal (hemorrhoids)
54
Q

What are valves?

A
  • Found in small and medium-sized veins, especially those of the limbs
  • Consist of folds of the intima
  • -Endothelium
  • -Connective tissue rich in elastic fibers
  • Prevent back flow of blood
55
Q

What are the three main components of the lymph vascular system?

A
  1. Lymph capillaries
  2. Collecting vessels
  3. Main trunks
56
Q

What are lymph capillaries?

A
  • Larger diameter than blood capillaries
  • End blindly in tissue spaces
  • Flimsy basal lamina
  • Endothelial cells held together by a few tight junctions
57
Q

What are collecting vessels?

A

-Vein-like structure but thinner walls and valves more closely spaced

58
Q

What are main trunks?

A

Thoracic and right lymphatic ducts have vein-like structure

59
Q

What are some functional considerations relating to pressure in the venous system?

A
  • Pressure in vascular system forces fluids, salts and protein into extracellular compartment
  • Edema will develop if substances are not returned to circulation
  • Low pressure lymphatics well situated for taking up these materials
60
Q

What are functional considerations of the lymph system?

A
  • Contraction of smooth muscle in walls of vessels and adjacent skeletal muscles force lymph toward heart
  • Lymph flows through lymph node where it is filtered and picks up antibodies

CRRAB Week 2 (9 decks)

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