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Histology Exam 3 > Capillaries > Flashcards

Capillaries Flashcards

0
Q

Composition of a capillary

A

Single layer of endothelial cells and basal lamina

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1
Q

What are the smallest blood vessels?

A

Capillaries

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2
Q

What occurs in the capillaries?

A

Exchange of gasses, nutrients, and waste products between blood and tissues

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3
Q

Describe the volume of flow in the capillaries

A

3x the combined diameter of the aorta

Leads to low pressure and low flow rate (allows diffusion)

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4
Q

What agents are vasodilating?

A

Endothelium derived relaxing factors (EDRF), NO, low O2 tension

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5
Q

Vasodilation in capillaries results in?

A

Smooth muscles of the arterioles relaxes and increases blood flow in the capillaries (can lead to peripheral edema)

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6
Q

What causes vasorestriction? Results?

A

Systemic signals from the autonomic nervous system and release of norephinephrine by adrenal gland to cause smooth muscles in arterioles to contract resulting in decreased blood flow through the capillary bed

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7
Q

What maintains blood pressure? What regulates distribution?

A

Muscular arteries - blood pressure

Small arteries and arterioles - regulates distribution

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8
Q

What is the function of metarterioles?

A

Possess individual smooth muscle cells to act as precapillary sphincters

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9
Q

What is the final step before reaching the capillaries?

A

Arterioles to metarterioles then capillaries

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10
Q

Describe blood flow through capillaries

A

Single blood cell at a time

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11
Q

Metarteroles control flow to capillary via?

A

Smooth muscle cells acting as precapillary sphincters

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12
Q

Describe structure of capillary wall

A

Single layer of squamous endothelial cells
Connected by tight junctions
Basement membrane

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13
Q

What layers are present in capillary walls?

A

Tunica intima and basement membrane

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14
Q

Where are pericytes located?

A

Periphery around capillaries but not technically part of the capillary wall

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15
Q

What is the function of pericytes?

A

Stem cells able to form collagen fibers, endothelial cells, smooth muscle cells, and new pericytes. Functions to repair and support the capillaries

16
Q

Three types of capillaries? Description?

A

Continuous - no pores inn the walls
Fenestrated - pores (fenestrae) in walls
Sinusoidal - discontinuous endothelial cells, many large fenestrae, and enlarged diameter (30-40 um)

17
Q

T or F: Fenestrae can be open or covered by thin membranes

A

T

18
Q

Describe continuous capillaries. Location?

A

Possess a continuous endothelial lining of about equal thickness throughout. Found where movement of molecules fro blood to tissue or the reverse is highly regulated like in the CNS, cardiac, and striated muscle, lung, thymus (cortex), skin

19
Q

Lateral processes in endothelial cells of continuous capillaries are connected by?

A

Junctional complexes

20
Q

Large number of pinocytotic vesicles in the plasmalemma is characteristic of?

A

Continuous capillaries

21
Q

Where are fenestrated capillaries found?

A

GI tract, kidneys, endocrine gland

E.g. pancreas, intestines, renal tubules and glomeruli, cilary body of the eye

22
Q

Describe walls of fenestrated capillaries

A

Endothelium has constant thickness except at fenestrae

23
Q

Describe fenestrae in fenestrated capillaries

A

Present and may be covered by thin membranes or diaphragms that are thinner than a plasmalemma.

24
Q

Describe the diaphragm in fenestrae of fenestrated capillaries

A

2-3 nm thick and allows for bulk movement of ions, hormones, and nutrients

25
Q

Function of fenestrated capillaries

A

Allow for less impeded movement of molecules across endothelial barrier

26
Q

T or F: Fenestrated capillaries contain both microvesicles and fenestrae

A

T

27
Q

Describe organization of fenestrae in endothelial cells

A

Are located in groups and each has a diameter of 60-80 nm. Often circular and well organized

28
Q

Where are sinusoidal (discontinuous) capillaries found?

A

Liver, bone marrow, and lymphoid organs (e.g. spleen)

29
Q

Function of sinusoidal capillaries

A

Large molecules or whole cells can move between the tissue and the circulating blood

30
Q

Describe the walls of sinusoidal capillaries

A

lumens of 20-40 um which is greater than the other two types
Gaps separate endothelial cells (in liver and spleen)
Basal lamina is discontinous at the gaps

31
Q

What is the space of disse?

A

Perisinusodial space that exists in the liver between the hepatocytes and the capillaries (called sinusoids)
It is filled with plasma into which the microvilli of the hepatocyte extend to absorb molecules

32
Q

Describe the small pore system in capillaries

A

Small pores up to 9-11 nm in diameter

Discontinuities between endothelial cell junctions (intercellular junctions)

33
Q

Describe the large pore system in capillaries

A

Large pores up to 50-70 nm.

Represented by fenestrae and microvesicle transport

Histology Exam 3 (11 decks)

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