Study your flashcards anywhere!

Download the official Cram app for free >

  • Shuffle
    Toggle On
    Toggle Off
  • Alphabetize
    Toggle On
    Toggle Off
  • Front First
    Toggle On
    Toggle Off
  • Both Sides
    Toggle On
    Toggle Off
  • Read
    Toggle On
    Toggle Off

How to study your flashcards.

Right/Left arrow keys: Navigate between flashcards.right arrow keyleft arrow key

Up/Down arrow keys: Flip the card between the front and back.down keyup key

H key: Show hint (3rd side).h key

A key: Read text to speech.a key


Play button


Play button




Click to flip

81 Cards in this Set

  • Front
  • Back
Most important function of circulation; where it occurs:
Transport of nutrients to tissues, removal of cell excreta; in microcirculation.
What controls diameters of arterioles?
Local conditions in the tissues around the arterioles
What controls blood flow to tissues?
Total surface area and number of capillaries in the body:
SA = 500 - 700 square meters

Total # = about 10 billion
Internal Diameter of:
Arterioles = 10 - 15 um

Capillaries = 5 - 9 um
Which has muscle?
Arteriole = abundant muscle
Metarteriole = intermittent
Capillary = No smooth muscle except at origin from metaart.
What is the point of junction between a metaarteriole and capillary characterized by?
A Precapillary sphincter - smooth muscle fiber encircling the capillary.
What is the structure of a capillary wall like?
-Single layer epithelial cells
-Membrane is 0.5 um thick
-Internal diameter 4-9 um
-Surrounded by basement memb.
What are Intercellular clefts?
Pores in the endothelial capillary membrane.
What are Intercellular clefts for?
Free percolation of fluid between the capillary and interstitial fluid
How wide is an intercellular cleft?
6-7 nm - just a little bigger than Albumin
What are Plasmalemmal Vesicles?
Small vesicles that take up plasma or ECF and then diffuse through the endothelial cell
What are pores in the endothelial cells of the brain like?
Very small so that only water, O2, and CO2 can pass in/out of brain tissue.
What connects the endothelial cells in brain capillaries?
Tight junctions
What are pores in liver capillaries like?
Wide - to let nutrients and even plasma proteins through.
What are pores in GI capillary membranes like?
A little bit wider but not as much as in the liver.
What are pores in the capillary membranes of the Glomerulus like?
Fenestrated - allowing tremendous amounts of very small molecules/ions to filter through.
How are fenestrae different from Intercellular clefts?
They are pores passing right through middle of endothelial cells - not between like clefts.
What is bloodflow like in capillaries?
Not continuous; intermittent.
What allows for intermittency of bloodflow in capillaries?
Define vasomotion
Intermittent contraction of metarterioles and precapillary sphincters
What is the main regulator of vasomotion?
O2 concentration in the tissues
How are substances transferred between plasma and interstitium?
Via diffusion primarily
What causes diffusion?
Thermal motion of water molecules and dissolved substances in the fluid.
What can diffuse directly through capillary endothelial cells?
Lipid-soluble substances:
-Carbon dioxide
What can't just diffuse through the capillary endothelium?
Water-soluble, lipid-insoluble substances
What specifically has to go through intercellular pores?
-Na Cl ions
How much of the capillary surface area (total) consists of intercellular clefts?
Not more than 1/1000
What is the rate of water compare to plasma movement?
Water diffuses through pores 80x faster than plasma actually moves through capillaries.
What are the 4 most permeable substances at muscle capillary pores?
-Water (freely)
What determines the permeability of a substance?
Its diameter size - water is 20x less than the intercellular cleft diameter
What does the rate of diffusion of a substance through a capillary membrane depend on?
Concentration gradient of that substance on either side of the wall.
How much of the body consists of interstitium?
2 Types of Solid Structure in interstitium:
-Collagen fiber bundles
-Proteoglycan filaments
Purpose of collagen fiber bundles in interstitium:
Tensional strength
Where is interstitial fluid found?
In spaces between proteoglycan filaments (the brushy reticular network of them).
What is Interstitial fluid made of?
Same stuff as plasma minus the plasma proteins
What do proteoglycan filaments and interstitial fluid together make?
What are Rivulets?
Small pockets of freely flowing interstitial fluid not constrained by tissue gel.
When do rivulets and free fluid in the interstitium increase?
In edema
What forces determine filtration in capillaries?
Starling's forces
NFP is what
Sum of starling forces
-Hydrostatic F inside/outside
-Osmotic F inside/outside
What is the eqn for NFP?
What is the normal NFP?
Slightly positive - net filtration into tissues
What determines the RATE of capillary filtration?
-# of capillaries thru which blood is flowing
-# and size of pores in capillaries
What term encompasses the factors determining filtration rate?
Kf - Capillary filtration coefficient
Define Kf
A measure of the capacity of capillary membranes to filter water for a given NFP
Units of Kf
How is filtration rate of a capillary calculated?
Frate = Kf x NFP
2 Methods for estimating Capillary hydrostatic pressure:

What pressure did each give?
1. Direct micropipette cannulation - 25 mm Hg
2. Indirect functioal measurement - 17 mm Hg
How is micropipette cannulation done?
By shoving a pipette right into the capillary and measuring pressure.
What does the gravimetric method for measuring Pc tell you?
The functional hydrostatic pressure in a capillary
What is the functional Pc in a normal capillary?
17 mm Hg.
What's more accurate; cannulation or gravimetric?
3 Most Common methods for msring Interstitial Fluid Hydrostatic Pressure:
1. Micropipette cannulation
2. Implanted perforated capsules
3. Cotten wick insert in tissue
What pressure does the micropipette cannulation of interstitium give?
That of a free fluid pocket - b/c the tip can't be small enough to fit between proteoglycans.
What is the interstitial fluid pressure in loose subcutaneous tissue?
Negative: -3 mm Hg
What causes the tissue pressure to be negative?
Pumping by the lymphatic system.
What is another name for Colloid Osmotic Pressure?
Oncotic pressure
Normal Colloid Osmotic pressure of human plasma:
28 mm Hg
What are the actual components of Plasma oncotic pressure?
-19 mm Hg is protein
-9 mm Hg is cation held onto by the negatively charged protein
What is the term for proteins holding onto cations in plasma?
Donnan effect
What are the plasma proteins?
What does each contribute to oncotic pressure?
Albumin - 21.8 mm Hg
Globulins - 6.0 mm Hg
Fibrinogen - 0.2 mm Hg
Average interstitial fluid oncotic pressure:
8 mm Hg
What is the avg NFP at the arterial end of a capillary?
13 - moves fluid out
What is the avg NFP at the venous end of a capillary?
Why is the NFP negative at the venous end of a capillary?
Because the hydrostatic pressure inside the capillary is reduced from 30 to 10
How much fluid that is filtered at the arterial end of a capillary is reabsorbed at the venous end?
What happens to the other 1/10 of the filtered fluid?
It is absorbed into the lymph system.
What is the normal Starling's equilibrium value for NFP?
0.3 outward
What happens to the 0.3 mm Hg caused fluid that is filtered?
Returned to circulation via the lymphatic system.
What is the normal rate of net filtration in the entire body?
2 mL/min
What is the value of the whole body capillary filtration coefficient?
6.67 ml/min/mm Hg
What is important to remember about the filtration coefficient?
It varies a TON between different body tissues
Where is the filtration coeff:
Extreme = kidney/liver
Large = intestine
Medium = subcutaneous tissue
Small = brain/muscle
What happens to filtration if the mean capillary pressure rises from 17 to 37 mm Hg?
There will be 68x more net filtration, the lymphatics wouldn't be able to handle it, EDEMA would ensue.
What happens if the mean capillary pressure fell very low?
Net reabsorption; tissue fluid would decrease and plasma volume would increase.
Main function of the lymphatic system:
to remove protein and large particulate matter from the ISF and return it to circulation.
Total amt of lymph typically recycled in a day:
2-3 L
What attaches lymphatic capillary endothelial cells to surrounding connective tissue?
Anchoring filaments
What allows lymphatic capillaries to absorb proteins and large molecules?
The design of adjacent cells; they overlay ea other creating a flap/valve. Fluid can enter but can't leave.