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Histology of Blood Vessels Flashcards

1
Q

What does the systemic circulatory system do?

A

Carries oxygenated blood from the heart to tissues

Returns deoxygenated blood to heart

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2
Q

What does the pulmonary circulatory system do?

A

Carries deoxygenated blood from heart to lungs

Returns oxygenated blood to heart

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3
Q

Which circulatory systems depend on a pump?

A

Systemic

Pulmonary

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4
Q

What helps move blood around the portal circulatory system?

A

Movement and pressure changes in the body

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5
Q

What does the lymphatic system do?

A

Drains extracellular fluid back into the circulatory system

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6
Q

What three layers are present in a typical blood vessel?

A

Tunica intima

Tunica media

Tunica adventitia

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7
Q

What is the tunica intima?

A

Lining of simple squamous endothelial cells supported by a basal lamina

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8
Q

What marks the boundary between the tunica intima and the tunica media?

A

Internal elastic lamina

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9
Q

What is the tunica media comprised of?

A

Smooth muscle cells

Some collagen

Variable elastin

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10
Q

What marks the boundary between the tunica media and the tunica adventitia?

A

External elastic lamina

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11
Q

What is the tunica adventitia?

A

Supporting layer of dense fibroelastic connective tissue

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12
Q

What is a vasavasorum?

A

Smaller blood vessel networks that supply large blood vessels

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13
Q

Where are elastic arteries mainly found and why?

A

Closest to heart

Elastic walls can stretch to withstand high pressure and recoil to maintain flow

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14
Q

When do the elastic artery walls stretch?

A

Systole

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15
Q

When do the elastic artery walls recoil?

A

Diastole

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16
Q

Describe the tunica intima of elastic arteries (4)

A

Simple squamous endothelial cells

Subendothelial collagenous connective tissue

Rich in elastin

Fibroblasts and smooth muscle-like myointimal cells

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17
Q

Describe the tunica media of elastic arteries

A

Concentric, fenestrated sheets of elastin separated by sheets of collagen and smooth muscle cells

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18
Q

Describe the tunica adventitia of elastic arteries

A

Collagenous connective tissue

Vasavasorum and autonomic plexuses

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19
Q

Give an example of an elastic artery

A

Aorta

Common carotid

Pulmonary artery

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20
Q

Describe the tunica media of a muscular artery

A

Almost entirely circumferential smooth muscle cells

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21
Q

Where is elastin found in a muscular artery?

A

Only in the internal elastic lamina and maybe a less distinct external elastic lamina

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22
Q

What is the function of smooth muscle in a muscular artery?

A

Withstand pressure

Vary lumen diameter to regulate flow

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23
Q

What stimulates the smooth muscle cells to contract in muscular arteries?

A

Sympathetic NS

Adrenaline

Local factors in response to vessel injury

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24
Q

What is the pressure that can be sustained in a muscular artery proportional to?

A

Wall thickness / diameter

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25
What are arterioles?
Terminal branches of arterial system
26
What is the diameter of an arteriole?
<0.1mm
27
Describe the structure of an arteriole (4)
Thin tunica intima May have a thin internal elastic lamina <6 layers of smooth muscle cells in tunica media Insignificant tunica adventitia
28
What is the relationship between pressure and radius?
(Pressure = resistance to flow / Rf) Rf = k / r^4 or inversely proportional to r^4
29
What is the main factor used in the regulation of systemic blood pressure?
Control of blood flow through arterioles
30
What occurs in microcirculation?
Exchange of gases, fluids, nutrients and waste products
31
What is the order of blood vessels from the microcirculation?
Capillaries Post-capillary venules Collecting venules Muscular venules
32
What controls flow into capillaries?
Arterioles Pre-capillary sphincters
33
How close must an active cell be to a capillary?
150um
34
What is a true capillary?
Single layer of endothelial cells (and basal lamina) only
35
What is a metarteriole?
Transitional vessels (arteriole to capillary) Discontinuous layer of smooth muscle cells
36
What are arteriovenous shunts?
Direct connections between arterial and venous systems
37
What is the diameter of a capillary?
Varies from 3-4um to 30-40um Average is 8-10um
38
How long is a capillary?
<1mm
39
What are sinusoids?
Large diameter capillaries
40
Where are sinusoids found?
Liver Spleen Bone marrow Some endocrine glands
41
Describe a continuous capillary
Tube of endothelial cells resting on a thin basal lamina Tight junctions Embraced by pericytes
42
How are substances transported across capillary membranes?
Small molecules (eg. O2) simply diffuse through endothelial cells Permeability to other molecules depends on 'tightness' of tight junctions Large molecules and fluids involves transcytosis across endothelial cells
43
What is transcytosis?
Calveolae bud off vesicles which cross the cell and fuse with calveolae on the opposite side of the cell
44
What are calveolae?
Flask-like pits on endothelial cells lined by calveolin
45
What is the purpose of fenestrated capillaries?
Rapid movement of macromolecules
46
Where are fenestrated capillaries found?
Small intestine Kidney Some endocrine glands
47
Describe a fenestra (of a capillary)
Basal lamina and basal membranes of endothelial cells come together to form fenestrae Fenestrae closed by diaphragm (continuous basal lamina)
48
What is the average diameter of a fenestra?
50nm
49
Where are discontinuous capillaries found?
In sinusoids of liver and spleen
50
What is the purpose of discontinuous capillaries?
Allows free passage of large macromolecules or even cells
51
Describe a discontinuous capillary
Large gaps between endothelial cells with a discontinuous basal lamina
52
What is the difference between a post-capillary venule and a capillary?
(Similar structure but) larger diameter
53
What occurs at post-capillary venules?
Entry and exit of white blood cells
54
What is the difference between a collecting venule and a post-capillary venule?
Larger diameter More pericytes
55
How many layers of smooth muscle cells are in muscular venules?
1-2
56
What vessels come together to form veins?
Muscular venules
57
Describe the structure of a vein
Tunica intima is little more than endothelium Tunica media is 2+ layers of smooth muscle cells Tunica adventitia is the broadest layer
58
How could you tell the difference between an artery and a vein on a micrograph?
Veins have a larger diameter to smooth muscle/wall ratio
59
How can you tell the difference between a blood vessel and a lymphatic vessel on a micrograph?
No red blood cells in a lymphatic vessel
60
How does blood move through the vein system?
Passively Assisted by negative pressure within chest/right atrium during inspiration Assisted by muscle contractions causing vein compression from limbs/skeletal pump
61
What prevents backflow in veins?
Valves
62
What is the structure of a valve in a vein?
2 semilunar projections of fibroelastic tissue extending from tunica intima
63
When do you find valves in veins?
When the vein is larger than 2mm in diameter
64
What is the function of the endothelial cells?
Permeability barrier Synthesise and secrete substances
65
What do endothelial cells synthesise/secrete? (5)
Blood clotting factors Molecules that prevent inappropriate blood clotting Vasoactive factors (promote/inhibit vasodilation) Inflammatory mediators Some growth factors
66
At which end of the microcirculatory system is the hydrostatic pressure highest?
Arterial end
67
Where does the lymphatic system drain into?
Subclavian veins
68
Where are lymphatic vessels not found? (6)
CNS Cartilage Cornea Bone and bone marrow Placenta Teeth
69
What is a lymphatic vessel similar to in structure?
Sinusoids
70
What does high hydrostatic pressure in the microcirculation cause?
Water, electrolytes and some proteins to leak into extracellular space
71
Describe the structure of a lymphatic vessel
Extremely flattened endothelial cells and basal lamina (no pericytes) Delicate semilunar valves prevent backflow
72
What is angiogenesis?
Formation of new blood vessels from pre-existing capillaries
73
When does angiogenesis occur?
Menstrual cycle Placental growth Wound healing Inflammation
74
Briefly describe angiogenesis
Capillary sprout Migration and proliferation of endothelial cells Assembly into tubes Recruitment of smooth muscle cells, pericytes and fibroblasts
75
What type of cell can induce angiogenesis?
Tumour cells

BMS10 (13 decks)

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