Exam 2 (Lecture 8) - Microcirculation and Interstitium

Question 1

What are the components of the cardiovascular system?

Answer 1

1) Arteries and arterioles
2) Capillaries
3) Venules and veins
4) Lymphatics

Question 2

What are the fluid compartments?

Answer 2

1) Intracellular
2) Extracellular
- Vascular
- Body cavities
- Interstitium

Question 3

Which physics concepts are important for understanding microcirculation?

Answer 3

1) Fluid Dynamics
2) Laminar Flow
3) Starling’s Hypothesis

Question 4

What other components are important for microcirculation?

Answer 4

1) Endothelium
2) Interstitium

Question 5

Do capillaries or the aorta have greater cross-sectional area?

Answer 5

Capillaries
- 1300x greater than the aorta; BUT only 5% of total blood volume

Question 6

What is the MAX distance between a capillary and cell? What does this mean?

Answer 6

1 mm
- This means that there is a LOT of vascular supply.

Question 7

Describe the interstitium.

Answer 7

Structural framework for cells.

Composed of:
- Type I collagen
- Type IV collagen (basement membrane)
- Adhesive glycoproteins
- attachment, receptors
- Absorptive glycoaminoglycans, proteoglycans
- hydrophilic

Question 8

Describe the fluid distribution in the body.

Answer 8

60% of body weight is water.
- 2/3 intracellular
- 1/3 extracellular
- 80% in interstitium
- 20% in plasma

Physical barriers

Osmotic gradients

Pressure gradients

**100 times cell water volume crosses plasma membrane in 1 second
- Stable cell volume achieved by Na/K+ pumps and osmotic
gradient

Question 9

Describe the properties of endothelium.

Answer 9

Single cell layer within the vascular system.

Antithrombotic/profibrinolytic

Activation: typically localized
- inflammation
- hypoxia
- oxidative stress
- injury/infectious agent
** can do these in the face of injury

Location and structure differences

Question 10

Which mediators are produced during vasodilation/vasoconstriction?

Answer 10

1) Nitric Oxide (NO)
2) PGL2/Endothelin

Question 11

Which mediators are produced to maintain homeostasis?

Answer 11

1) Antihemostatic
2) Prohemostatic

Question 12

Which mediators are the inflammatory mediators?

Answer 12

1) Cytokines
2) Cell adhesion molecules
3) Selectins

Question 13

Which cells produce the growth factor mediators?

Answer 13

1) Smooth muscle/fibroblasts
2) Colony stimulating factors

Question 14

Which mediators are responsible for fibrinolysis?

Answer 14

Fibrinolytic components

Question 15

List the roles of endothelial cells.

Answer 15

1) Produce prostacyclin

2) Modulate smooth muscle activity

3) Vasoactive role
- endothelin 1 (vasoconstriction)
- nitric oxide (vasodilator)

4) Control vascular cell growth

5) Trigger blood coagulation

6) Regulate the traffic of inflammatory cells

Question 16

What is Starling’s Hypothesis?

Answer 16

• Flow of fluids across capillary walls is a balance between the force of blood pressure on the walls (tends to force fluids out) AND the osmotic pressure across the walls (tends to keep fluids in the vessel; or draw them back in when they leave).
• These pressures change between arteriolar to venular sides of capillary bed.

Question 17

Describe net filtration and capillary endothelial permeability.

Answer 17

At the arteriole end:
- Hydrostatic pressure: high
- Filtration (fluid out of capillary bed into interstitial fluid)

At the venule (venous) end:
- Hydrostatic pressure: low
- Absorption (fluid into capillary bed from interstitium)

Question 18

What are the osmotic factors?

Answer 18

Albumin

Question 19

What are the hydrostatic factors?

Answer 19

Blood pressure

Drainage

Question 20

What causes a disturbance of circulation?

Answer 20

Edema

  - Accumulation of fluid in extravascular space

  - Edema is a transudate (low protein/low cellular) fluid
        - watery, clear

Question 21

What are the mechanisms of edema?

Answer 21

1) Decreased plasma oncotic pressure (decreased protein)
- low albumin (due to it not being produced, a nutritional
deficiency, or a severe burn case)

2) Increased capillary hydrostatic pressure due to:
- heart failure
- venous obstruction

3) Lymphatic obstruction due to:
- fibrin thrombi
- tumor emboli
- external compression (Ex: cast left on too long)

4) Increased vascular permeability (“inflammatory” edema)
- inflammation

Question 22

What are the causes of vascular leakage associated with inflammation?

Answer 22

• Infectious agents
  - viruses
  - bacteria
  - rickettsia
• Immune-mediated
• Neovascularization
• Anaphylaxis
• Toxins
• Clotting abnormalities
• Metabolic abnormalities

Question 23

What are the causes of increased intravascular hydrostatic pressure?

Answer 23

• Portal hypertension
• Pulmonary hypertension
• Localized venous obstruction
• Fluid overload
• Hyperemia

Question 24

What are the causes of decreased intravascular osmotic pressure?

Answer 24

• Decreased albumin production
• Excessive albumin loss
• Water intoxication

Question 25

What are the causes of decreased lymphatic drainage?

Answer 25

• Lymphatic obstruction or compression
• Congenital lymphatic aplasia or hypoplasia
• Intestinal lymphangiectasia
• Lymphangitis

Question 26

How do you recognize edema grossly?

Answer 26

1) Appears pitted:
- Tissue “pits” when pressure is applied to it.

2) Swollen

3) Spongy

4) Pale

5) Cool to the touch (b/c of decreased blood flow to the area)

6) Pain +/-

Question 27

How do you recognize edema microscopically?

Answer 27

1) Expansion of intercellular spaces

2) Pale eosinophilic fluid (b/c of protein presence)