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CVS & IBL - Histology 🔬 > L2: Vascular system > Flashcards

L2: Vascular system Flashcards

1
Q

What is the circulatory system formed of?

A
  • The heart.
  • Various types of blood vessels including:
    Arteries: (large elastic, medium-sized and arterioles).
    Veins: (venules, medium-sized and large veins).
    Connecting vessels between arteries and veins:
    1- Blood capillaries.
    2- Arterio-venous anastomosis.
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2
Q

What is the function of the blood vessels?

A

These vessels distribute blood to every part of the body and return it to the heart for
redistribution.

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3
Q

What are the three layers that form any blood vessel?

A

Tunica intima (the inner most coat)
Tunica media
Tunica adventitia

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4
Q

What does the tunica intima consist of?

A

Endothelial lining:
✓ Formed of simple squamous epithelium with flat nuclei
resting on a basal lamina. “As it is in connection with blood”
✓ Have a turnover rate of 1% per day.

Subendothelial layer:
✓ Consists of loose C.T.
✓ Rich in elastic fibers

Internal elastic lamina
✓It is seen as a wavy pink line just beneath the endothelium in arteries
✓ It is composed of elastic fibers.

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5
Q

What is the tunica media formed of?

A
  • Composed of circularly arranged smooth muscle cells.
  • Variable amount of elastic fibres.
  • Fine collagenous and reticular fibers. “All fibers”
  • In large muscular arteries
    ✓ The outer border of the media is separated from the outer tunica adventitia by the external elastic lamina.
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6
Q

What is Tunica adventitia formed of?

A
  • Fine collagenous fibres longitudinally oriented, contain collagen type I.
  • Elastic fibers. “But no reticular”
  • Tiny blood vessels called vasa vasorum (vessels of vessels) supply the adventitia and may reach the periphery of the media.
  • Lymphatics are also present in the adventitia of arteries only but in veins they can penetrate the media.
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7
Q

What are the large elastic arteries?

A

Large elastic arteries include the aorta and its large branches, the pulmonary, the subclavian and the innominate.

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8
Q

What are the characters of large arteries?

A

 They have thick walls and wide lumen.
 Their media are rich in elastic fibers.
 Their structure is more or less the same as the aorta.

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9
Q

What is the LM of the intima of the aorta? “Aorta=many elastic fibers”

A

Forms about 1/6 of the thickness of the wall.

The intima is thicker than the intima of a muscular artery.

The subendothelial layer is thick and rich in elastic fibers.

The internal elastic lamina is present but not be easily discerned, since it is similar to the elastic laminae of next layer.

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10
Q

What is the LM of the media of the aorta?

A

 Is very thick and forms the main thickness of the wall.

 It contains fenestrated elastic laminae concentrically arranged

 In between the elastic laminae smooth muscle cells, reticular fibers, collagenous fibers and ground substance consisting mainly of chondroitin sulfate. “More strength”

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11
Q

What is the LM of the adventitia of the aorta?

A

 Relatively thin and contains collagenous and elastic fibres.
 C. T. cells, vasa vasorum, lymphatics and nerves.

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12
Q

What is the function of large elastic arteries?

A

Transport blood away from the heart.

Maintain diastolic pressure.

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13
Q

What are the characteristics of the wall and the lumen of medium sized artery?

A
  • Thick “more hemorrhage when damaged”
  • Narrow
  • rounded “due to elasticity”
  • no valve
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14
Q

What are the characteristics of the wall and lumen medium sized vein? “Vein=no elasticity”

A
  • Thin
  • Wide
  • Collapsed
  • valve is present
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15
Q

What are the characteristics of tunica intima of medium sized artery?

A
  • Thick

- Internal elastic lamina is well developed

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16
Q

What are the characteristics of tunica intima of medium sized vein?

A
  • Thin

- Internal elastic lamina is absent

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17
Q

What are the characteristics of tunica media of medium size artery?

A
  • Thick.
  • Formed of smooth muscle fiber and elastic fibers.
  • External elastic lamina may be present between the media and adventitia.
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18
Q

What are the characteristics of tunica media of medium sized vein?

A
  • Thin.
  • Formed of few smooth muscle fibers.
  • No external elastic lamina.
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19
Q

What are the characteristics of Tunica adventitia of medium size arteries?

A
  • Thinner than media
  • contains elastic fibers
  • No lymphatic capillaries in its wall
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20
Q

What are the characteristics of Tunica adventitia of medium sized veins?

A
  • Thicker than media
  • No elastic fibers
  • Lymphatic capillaries may be found
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21
Q

How does blood flow in medium sized arteries?

A

Rapid flow of arterial blood

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22
Q

How does blood flow in medium size veins?

A

Slow flow of venous blood

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23
Q

What is the function of medium sized arteries?

A

Distribute blood to the whole body

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24
Q

What is the function of medium sized vein?

A

Carry venous blood from the tissues Withstand venous blood pressure

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25
Q

What is the definition of Arterioles?

A
  • Are the small branches of the arteries, Their diameter is less than 0.5 mm.
26
Q

What is the structure of arterioles?

A

The subendothelial layer is very thin

 The elastic laminae may be present or absent “absent in very small arterioles”

 Tunica media is formed of 1-2 layers of smooth ms.

Tunica adventitia is very thin “No vasa vasorum as the vessels are nourished by the blood flowing in the lumen”

27
Q

What is the definition of meta-arterioles?

A

The terminal parts of the arteriole before their connection with the blood capillaries.

28
Q

What is the structure of meta-arterioles?

A

 They have sphincters at their terminal.

 They have a sparse layer “separated” of smooth muscle

29
Q

What is the function of arterioles?

A

✓ They supply the tissues and organs with arterial blood.

✓ They control blood pressure. “Sphincters”

30
Q

What is the definition of veins?

A

Blood vessels carry venous blood from the tissues and return it to the heart.

31
Q

What do veins start as and what do they end as?

A

They start as post-capillary venules which are collected to form muscular venules then form large veins.

32
Q

What are veins classified into?

A

o Venules.
o Medium-sized veins.
o Large veins.

33
Q

What are the types of venules?

A

 Post-capillary venules.
 Collecting venules.
 Muscular venules.

34
Q

What is the definition of post Capillary venules?

A

Small venules that collect the capillaries.

35
Q

What is the LM structure of post Capillary venules?

A

▪ As capillary
▪ Endothelium: simple squamous epithelium.
▪ Basement membrane which supports the endothelium.
▪ Pericytes lie between the endothelium and basement membrane, they can differentiate to smooth muscle cells.

36
Q

What is the shape of postcapillary venues in the thymus gland and lymph nodes?

A

the post-capillary venules are lined with simple cubical epithelium, which shows wide intercellular spaces allowing migration of the T. lymphocytes.

37
Q

What is the definition of collecting venules?

A

Are venules that collect the post-capillary ones.

38
Q

What is the structure of collecting venules?

A

In addition to endothelium and pericytes, they possess an adventitia consisting of fibroblasts and collagen fibers.

39
Q

What is the definition of muscular venules?

A

Large-sized venules into which the collecting venules empty.

40
Q

What is the structure of muscular venules?

A
  • They have one or two layers of smooth muscle cells in their media. “Like arterioles”
  • The adventitia is relatively well developed.
41
Q

What are the characters of large veins and what is an example for them?

A

Character:

  • Has very wide lumen with many valves.
  • Collapsed thin and flat wall.

inferior Vena Cava

42
Q

What is the LM structure of large veins?

A

The intima: Similar to the medium-sized vein.

The media: Thin and contains only smooth muscle fibers.

The adventitia: Very thick layer of loose C.T. contains collagenous fibers, C.T. cells, vasa vasorum, and nerves, Also contains longitudinally arranged bundles of smooth muscle fibers. “Shorten-lengthen the vein to push blood”

43
Q

What is the definition of blood capillaries?

A

Thin-walled tubular blood channels that conduct the blood from the terminal arterioles to the venules.

Networks of these vessels are known as capillary beds.

44
Q

What is the LM structure of blood capillaries?

A

 Single-layer of endothelial cells is rolled up in the form of a tube.

 Rest on a basal lamina.

 Pericytes: lie between endothelium and the basal lamina.

45
Q

What is the EM structure of blood capillaries?

A

 Contain all the usual organelles.

 Abundant microfilaments and intermediate filaments.

 Endothelial cells show pinocytotic vesicles.

 The cells are held together by zona occludens and gap junction.

 Pericytes with long cytoplasmic processes surround the endothelial cells along capillaries, enclosed in their own basal lamina.

 Their cytoplasm contains myosin, actin, and tropomyosin which suggest their contractile function.

46
Q

What happens to pericytes after tissue injury?

A

pericytes proliferate and differentiate to form new blood vessels and C. T. cells.

47
Q

What are the types of capillaries?

A

 Continuous capillaries
 Fenestrated capillaries
 Fenestrated without diaphragm
 The sinusoid or discontinuous capillary

48
Q

What are the characters of continuous capillaries?

A

 No fenestrae are present in this type.

 May have numerous pinocytotic vesicles as in muscle capillaries or few or no pinocytotic vesicles as in nervous system capillaries

 Allow regulated exchange of material.

49
Q

What are the sites of continuous capillaries?

A

Is found in all kinds of muscle tissue, nervous tissue, and exocrine glands

“Nervous-muscular-Exo from prison”

50
Q

What are the characteristics of fenestrated or visceral capillaries?

A

 Large fenestrae are present in the walls of endothelial cells.
 The fenestrae are closed by a diaphragm that is thinner than a cell membrane.
 A continuous basal lamina is present.
 Allow more extensive molecular exchange across the endothelium

51
Q

What are the sites of fenestrated or visceral capillaries?

A

Present in the kidney, intestine, and endocrine gland.

“KID INSIDE”

52
Q

What are the characteristics of fenestrated capillaries without diaphragms?

A

Has a very thick basal lamina that separates the endothelium from the overlying epithelial cells.

53
Q

What are the sites of Fenestrated Capillary without diaphragm?

A

Renal glomerulus capillary

54
Q

What are the characteristics of sinusoids or discontinuous capillaries?

A

TDM

✓ Has tortuous path.

✓ Enlarged diameter

✓ Macrophages may be present outside the sinusoidal wall, extending their pseudopodia inside the wall to phagocytose any foreign body.

✓ The endothelial cells have large fenestrae without diaphragm forming a discontinuous layer

✓ The basal lamina is discontinuous.

✓ Allow maximal exchange of macromolecules as well as cells between tissues and blood

55
Q

What are the sites and functions of sinusoids or discontinuous capillaries?

A

1- In bone marrow: Allow migration of blood cells, to the general circulation. - Have slow circulation → low O2 tension → stimulate erythropoiesis.

2- In the spleen: Store and filter the blood.

3- In the liver: Allow the blood to come into contact with the hepatocytes.

4- In endocrine glands: Allow migration of hormones to general circulation

56
Q

What are the functions of capillaries?

A

Selective exchange of materials from blood to tissue and vice versa.

57
Q

What are the functions of endothelial cells?

A

Permeability + secretion of VIP

  • Act as a permeability barrier.
  • Synthesize collagen and proteoglycans for basement membrane maintenance.
  • Synthesize and secrete molecules that promote protective thrombus formation, e.g. von Willebrand factor (Factor VIII).
  • Secrete vasoactive factors control blood flow, e.g. nitrous oxide, vasoactive peptides such as endothelin.
  • Produce molecules that mediate the acute inflammatory reaction, e.g IL 1, 6, and 8, cell adhesion molecules.
58
Q

What is the definition of AV Shaunts?

A

Are blood channels, which allow the blood to pass directly from the arteries and arterioles to the veins or venules without its having to go through capillaries, metarterioles, or preferential channels.

59
Q

What are the types of AV shunts and their sites?

A
  • Direct connections: Between an arteriole and a venule by side branch as found in the placenta.
  • Glomus or complicated side: branch present in skin, ear pinna, toes, and nail bed.
60
Q

What is the structure of AV shunts?

A
  • Are similar to the arterioles on their arterial side and similar to the venules on the venous side.
  • The intermediate segment of the A-V shunt
    1- The lumen decreases gradually towards the venous side.
    2- The internal elastic lamina disappears towards the venous side.
    3- The media is well-developed, rich in longitudinal smooth muscles, and contains myoepithelial cells which act as sphincters.
    4- The adventitia becomes thicker at the venous side.
61
Q

What are the sites of AV shunts?

A

Exposed parts as tips of fingers, toes, external ear, nose, lip, and tongue.

Internal organs such as stomach, intestine, liver, endocrine gland, uterus, placenta and
sympathetic ganglia.

62
Q

What is the function of AV shunts?

A

 Conserve the body temperature; dilate in cold weather while constricting in hot weather.

 Regulate the blood flow to the organs according to their need.

 When dilating the venous return is increased and vice versa.

CVS & IBL - Histology 🔬 (5 decks)

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