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ESA 2- Cardiovascular System > Histology of the CVS > Flashcards

Flashcards in Histology of the CVS Deck (134)
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91

What are the most common type of capillaries?

Continous

92

Where are continuous capillaries located?

Nervous, muscle and connective tissues, exocrine glands, and the lungs

93

What do continuous capillaries consist of?

Continuous endothelial layer, with the cells joined by tight or occluding junctions

94

Where are fenestrated capillaries found?

In parts of the gut, endocrine glands and the renal glomerulus

95

What exists in fenestrated capillaries?

‘Little windows’, or interruptions, across thing parts of the endothelium, which are bridged by a thin diaphragm (except in the renal glomerulus)

96

What are the possible routes of transport across the endothelial wall of a fenestrated capillary?

Direct diffusion
Diffusion through intercellular cleft
Diffusion through fenestration 
Through pinocytic vesicles

97

How do sinusoids differ from other capillaries?

They have a larger diameter and a slower blood flow

98

What is the diameter of sinusoids?

30-40µm

99

Where are sinusoids found?

In the liver, spleen and bone marrow

100

What do sinusoids have?

Gaps in the wall

101

What is the purpose of the gaps in the walls of sinusoids?

Allows whole cells to move between blood and tissue

102

What do pericytes form?

A branching network on the outer surface of the endothelium

103

What are pericytes capable of?

Dividing into muscle cells or fibroblasts, during angiogenesis, tumour growth and wound healing

104

How are postcapillary venules similar to capillaries?

The wall is similar, in that it has an endothelial lining with associated pericytes

105

What is the diameter of postcapillary venules?

10-30µm

106

What is more permeable, capillaries or post-capillary venules?

Post-capillary venules

107

What tends to drain into post-capillary venules?

Fluid

108

Why does fluid tend to drain into post-capillary venules?

Because their pressure is lower than that of capillaries or the surrounding tissues

109

When does fluid not drain into the postcapillary venules?

When an inflammatory response is operating, in which case fluid and leukocytes emigrate

110

What are the post-capillary venules the preferred location for?

Emigration of leukocytes from the blood

111

At what point do smooth muscle fibres begin to be associated with the endothelium of venules?

As the diameter of merging venules begin to increase to more than 50µm

112

What is happening as smooth muscle fibres begin to appear in venules?

A tunica media is beginning to appear

113

What is the diameter of venules?

Up to 1mm

114

What is the endothelium of venules associated with?

Pericytes

115

What can venules have?

Valves

116

What do venules valves consist of?

Thin, intimal extensions

117

What do venules valves do?

By pressing together, they restrict retrograde transport of blood, stopping blood flow in the opposite direction

118

What is the general rule regarding veins?

They have a larger diameter than any accompanying artery, and a thinner wall that has more connective tissue and fewer elastic and muscle fibres

119

What do small and medium sized veins have?

A well developed adventitia

120

What does the tunica media of veins consist of?

2 to 3 to layers of smooth muscle