CVS Different Types of Capillaries, Functions and Solute Movement

Question 1

What are cell memrbanes?

Answer 1

Cell membranes are a barrier to solute transport

Question 2

What does it mean by semi permeable membrane?

Answer 2

Allow movement of water

Question 3

What do cell membranes provide?

Answer 3

Provide support and protection

Question 4

What do cell membranes control?

Answer 4

Controls what enters or leaves the cell – e.g. ion movement in nerves

Question 5

What do cell membranes regulate?

Answer 5

Regulates cell function – e.g. Insulin-mediated glucose uptake

Question 6

What layers does the cell membrane consist of?

Answer 6

Consists of two layers of amphipathic
phospholipids

Question 7

What is the state of phosphate head?

Answer 7

Phosphate head is polar (hydrophilic)

Question 8

What is the state of fatty acid tail?

Answer 8

Fatty acid tail is non-polar (hydrophobic)

Question 9

What does a cell membrane form in solution?

Answer 9

Form bilayers in solution

Question 10

Where does most solute and fluid movement occur?

Answer 10

Most solute and fluid movement occurs at capillaries

Question 11

How thick is the endothelium of capillaries?

Answer 11

Endothelium only – 1 cell thick

Question 12

What do capillaries connect?

Answer 12

Vessels that connect arterioles to venules

Question 13

What is passive movement?

Answer 13

– Movement of molecules DOWN a gradient

Question 14

Does passive transport require energy?

Answer 14

No

Question 15

What is active transport?

Answer 15

Movement of molecules AGAINST a gradient

Question 16

What are the four passive transport processes?

Answer 16

1. Diffusion
2. Convection
3. Osmosis
4. Electrochemical flux

Question 17

How does diffusion work?

Answer 17

Concentration gradient

Question 18

How does convection work?

Answer 18

Pressure gradient

Question 19

How does osmosis work?

Answer 19

Osmotic pressure (water) gradient

Question 20

How does electrochemical flux work?

Answer 20

Electrical and Concentration gradient
e. g. ion flow during an action potential in a nerve

Question 21

What does convection require?

Answer 21

Requires pressure gradient, functioning heart – appropriate CO etc.

Question 22

What does osmosis require?

Answer 22

Requires balance of filtration, reabsorption and functioning lymphatics
(see Fluid movement and oedema session)

Question 23

What does electrochemical flux require?

Answer 23

Requires active and other transport mechanisms to create electrochemical
gradients, needs ion channels to provide ion movement across membranes

Question 24

What does properties of the solute that affect transport?

Answer 24

-Concentration gradient
-Size of the solute
-Lipid solubility of solute (lipophilic,
lipophobic nature)

Question 25

What are the properties of the membrane affecting transport?

Answer 25

-Membrane thickness/composition -Aqueous pores in the membrane -Carrier-mediated transport -Active transport mechanisms

Question 26

What are the 4 factors that determine solute movement?

Answer 26

1. D = Diffusion coefficient of solute - how easy it moves through solvent 2. Area 3. deltaC/x 4. x(distance0 Js = - D*A*deltaC/x

Question 27

What are the 3 distinct types of capillaries?

Answer 27

1. Continuous capillaries 2. Fenestrated capillaries 3. Discontinuous capillaries

Question 28

What are the 3 distinct types of capillaries?

Answer 28

1. Continuous capillaries 2. Fenestrated capillaries 3. Discontinuous capillaries

Question 29

What is the permeability like for continuous capillaries?

Answer 29

Moderate permeability

Question 30

How are the gaps like between continuous capillaries?

Answer 30

Tight gaps between neighbouring cells

Question 31

What type of constant membrane does continuous capillaries have?

Answer 31

Constant basement membrane

Question 32

What is the permeability like for fenestrated capillaries?

Answer 32

High water permeability

Question 33

What is the basement membrane like in fenestrated capillaries?

Answer 33

Modest disruption of basement membrane

Question 34

What structures do discontinuous capillaries have?

Answer 34

Very large fenestration structures

Question 35

What is the basement membrane like for discontinuous capillaries?

Answer 35

Disrupted basement membrane

Question 36

What are the 3 structural features of capillary walls that can influence solute transfer?

Answer 36

1. Intercellular cleft 2. Glycocalyx 3. Caveola-vesicle system

Question 37

How wide is the intercellular cleft?

Answer 37

10-20 nm wide

Question 38

What does the glycocalyx cover?

Answer 38

covers endothelium

Question 39

What does glycocalyx acts as?

Answer 39

acts as sieve for solute permeation and access to transport mechanisms

Question 40

What are caveolae and vesicles involved in the movement of?

Answer 40

movement of large molecules,

Question 41

What processes does glucose transport occur via across membrane from capillaries into tissues?

Answer 41

Glucose transport across membrane from capillaries into tissues occurs by either passive diffusion or filtration

Question 42

What is glucose concentration in blood plasma?

Answer 42

Glucose concentration in blood plasma is 1 g / litre

Question 43

Via what process is the majority of glucose transport into interstitial space?

Answer 43

98% of glucose transport into interstitial space via passive diffusion - via GLUT carrier system -

Question 44

How does increased blood flow increase diffusion rate?

Answer 44

Increases concentration of solutes in capillaries Less time for equilibration between interstitial spaces and plasma in capillaries of highly membrane permeable solutes, e.g. O2/CO2

Question 45

How does a fall in interstitial concentration increase diffusion rate?

Answer 45

Increases the concentration difference Also, metabolism increases blood flow - metabolic hyperaemia -  O2 delivery

Question 46

How does recruitment of capillaries increase diffusion rate?

Answer 46

Dilation of arterioles - Increased number of capillaries perfused Increases total surface area A for diffusion (Fick’s law) Shortens diffusion distance deltax (faster diffusion)

Question 47

What is permeability?

Answer 47

Permeability is the rate of solute transfer by diffusion across area of membrane per concentration difference