Test 5 (lymphatics) Flashcards
Functions of microcirculations
- Control delivery of nutrients
- Remove waste products
- Maintain ionic concentrations
- Transport hormones
**Most significant**
- Transport of nutrients & removal of cell excreta
anatomy from artery to venules and their size
nutrient artery - > 50 mcm
organ
branches 6-8x
arterioles - 20 mcm
branches 2-5x
metarterioles - 5-9 mcm
capillaries - 5 mcm
venous end of capillary - 9 mcm
venules
describge arterioles
- Highly muscular; contain smooth muscle
- Diameter can change easily d/t smooth muscle
- Major resistance vessels
- Regulate regional blood flow to capillary beds
describe metarterioles
- Contain smooth muscle
- intermittent, not continuous
- Precapillary sphincter
describe venules
can they contract?
- Contain smooth muscle; weaker coat
-
Collecting channels
- Storage or capacitance vessel
- Pressure in venules is much less than that of arterioles, but can still contract considerably even though they have a weak muscle layer
describe wall of capillaries
- wall is ____ layer of ___cells
- surrounded by____ _____.
capillaries:
- wall is unicellular layer of endothelial cells
- surrounded by basement membrane
capillaries:
- total capillary wall thickness
- internal diameter
- anatomical feature used for diffusion
- diameter of capillary pores
- contains smooth muscle?
capillaries:
- total thickness of wall 0.5 mcm
- internal diameter 4-9 mcm
- anatomical feature used for diffusion: intercellular clefts
- diameter of capillary pores 25 x that of H2O
- O2 & CO2 lipid soluble/readily pass
- contains smooth muscle? devoid of smooth muscle
Capillaries: Vasomotion
- Blood flow is ___ mm/sec & ___continuous/intermittent__ in capillaries
- Contraction & relaxation of ______ & ______ sphincters
Capillaries: Vasomotion
- Blood flow is 1 mm/sec & intermittent in capillaries
- Contraction & relaxation of metarterioles & precapillary sphincters
Capillaries: Vasomotion
Most important determinant
oxygen (nutritive flow)
___ arterioles control blood flow to each tissue and local conditions in the tissues will control _____diameter;
- Small arterioles control blood flow to each tissue and local conditions in the tissues will control arteriolar diameter;
- each tissue controls its own blood flow in relation to body needs.
- At point where each true capillary originates form metarteriole, there is a ____ muscle fiber that encircles this area (where arteriole becomes ____) and is called the ____ ____, and it opens and closes the entrance to the capillary
- At point where each true capillary originates form metarteriole, there is a smooth muscle fiber that encircles this area (where arteriole becomes capillary) and is called the Precapillary sphincter, and it opens and closes the entrance to the capillary
- this part of capillaries
- Thin, slit like, curving channel; “interdigitated junction”
- Passageways in many organs that connect interior of capillary with the exterior
- used for diffusion
- intercellular clefts
Intercellular clefts
- Interrupted by ____ attachments that hold cells together while fluid is allowed to move freely through the cleft
- Usually has _____ spacing that is about ___nanometers, which is slightly ____ than albumin molecule
- The rate of _____ motion of water molecules plus water soluble ions and small solutes is ____ that all of these substances diffuse with ease b/w the interior and exterior of the capillaries through these clefts.
Intercellular clefts
- Interrupted by protein attachments that hold cells together while fluid is allowed to move freely through the cleft
- Usually has uniform spacing that is about 6-7 nanometers, which is slightly smaller than albumin molecule
- The rate of thermal motion of water molecules plus water soluble ions and small solutes is rapid that all of these substances diffuse with ease b/w the interior and exterior of the capillaries through these clefts.
how many capillaries in body
10 billion
- “small caves” inside capillary cell
Plasmalemmal vesicles
aka “caveolae”
- Plasmalemmal vesicles (caveolae)
Formed by proteins called ____that are associated with molecules of ____and _____
Precise function is unclear, it is believed to play role in _____ (engulfing material from outside cell), and ______ of macromolecules across the endothelial cell (transport after endocytosis)
- Plasmalemmal vesicles (caveolae)
Formed by proteins called caveolins that are associated with molecules of cholesterol and sphingolipids
Precise function is unclear, it is believed to play role in endocytosis (engulfing material from outside cell), and transcytosis of macromolecules across the endothelial cell (transport after endocytosis)
- Caveolae at surface of cell appear to take up small packets of ___ or ___ fluid that contain plasma ___ ; these vesicles move through ___cell and discharge the plasma and proteins by ___ into interstitial fluid
- Caveolae at surface of cell appear to take up small packets of plasma or extracelluar fluid that contain plasma proteins ; these vesicles move through endothelial cell and discharge the plasma and proteins by exocytosis into interstitial fluid
- Diameter of capillary pores ___ x that of H2O molecules (__nanometers)
Diameter of capillary pores
- 25 x that of H2O molecules (0.3 nanometers)
- NaCl, Glucose, K+, CL- etc have______diameters;
- describe pore permeability
- NaCl, Glucose, K+, CL- etc have intermediate diameters; pore permeability varies according to the substance trying to enter
- devoid of smooth muscle, not capable of active constriction but do contain actin and myosin so can alter shape
“True” capillaries
Blood flow is ___mm/sec &_______in capillaries
capillaries
- Blood flow is 1 mm/sec & intermittent
vasomotion
- Contraction & relaxation of metarterioles & precapillary sphincters alternating in a cycle of about__ to ___ times per minute = vasomotion
- Contraction & relaxation of metarterioles & precapillary sphincters alternating in a cycle of about 6-12 times per minute = vasomotion
Vasomotor
- Most important determinant is___ (____ flow)
- Vasomotion is affected by ____ levels
Vasomotor
- Most important determinant is oxygen (nutritive flow)
- Vasomotion is affected by O2 levels
- this change in leveol of O2 allows more blood to flow through capillaries to supply tissues
- Low PO2 allows more blood to flow through capillaries to supply tissues
- When tissue O2 concentration goes below normal, vasomotion occurs more often and periods last longer=increased quantities of O2 released to tissues=nutritive flow
- Impact of O2 on capillary blood flow provides _______. (hard to make question out of this just)
- Impact of O2 on capillary blood flow provides autoregulation
- Nonnutritive flow (aka ____ flow) regulated by ____
- Nonnutritive flow (aka shunt flow) regulated by ANS
summary
- nutritive flow regulated by
- nonnutritive flow regulated by
summary
- nutritive flow regulated by O2
- nonnutritive flow regulated by ANS
Even though blood flow is intermittent, since there are so many capillaries in body their overall function is _____.
Average function of capillary system
- Even though blood flow is intermittent, since there are so many capillaries in body their overall function is averaged.
- Average rate of blood flow
- Average capillary pressure
- Average rate of transfer of substances b/w blood and ISF
- ______ of capillaries contains substances involved in contraction/relaxation of vascular smooth muscle in response to local tissue metabolic requirements.
- Endothelium of capillaries contains substances involved in contraction/relaxation of vascular smooth muscle in response to local tissue metabolic requirements.
Local Control of Capillary BF
- capillary blood flow is regulated by:
Local Control of Capillary BF
capillary blood flow is regulated by:
- delivery of O2 and other nutrients
- removal of products of metabolism
- or maintenance of ionic balance and pH.
2 Theories to explain local control of capillary BF: both state that vessels will dilate to increase blood flow d/t ____ or in response to a _____ substance in response to hypoxemia.
- Vasodilator theory
- Oxygen-demand theory
- both state that vessels will dilate to increase blood flow d/t hypoxemia or in response to a vasodilator substance in response to hypoxemia.
-
prostacyclin
- comes from where
- what principle fx
- does what to smooth
-
Prostacyclin – from arachidonic acid by prostacyclin synthase
- Principal function – inhibit platelet adherence & aggregation
- Relaxation of vascular smooth muscle by release of cAMP
- Nitric oxide (NO) – released by stimulation from _____
- Release can be stimulated by what
- Synthesized where
-
Nitric oxide (NO) – released by stimulation from vasoactive substances
- Release can be stimulated by shear stress of blood flow
NO is synthesized in endothelial cells by __ ___ in response to what?
Synthesized in endothelial cells by nitric oxide synthase in response to
- Ach
- ATP
- bradykinin
- Histamine
- serotonin
- Substance P
pathophys of NO on smooth muscle
- Activates guanylate cyclase and this activates cGMP = relax smooth muscle
- Ach causes increase of Nitric oxide synthase activity which causes production of NO that interacts with guanyl cyclase, creating cGMP and leading to relaxation of smooth muscle.
affects vascular tone and BP
Endotholin
endothelin
- A - does what
- B - does what
- A is vascular smooth muscle, causes constriction
- B causes constriction and vasodilation
Diffusion of substances through cell membrane is determined by: (4)
Diffusion of substances through cell membrane is determined by:
- Lipid solubility
- Water solubility
- Size of molecule
- Concentration difference from one side of membrane to the other: most important method of transport is diffusion
Diffusion of substances thru cell membrane
- Results from ____ motion of ___ molecules & _____ substances
Diffusion of substances thru cell membrane
- Results from thermal motion of H2O molecules & dissolved substances
the most important means by which substances move from plasma to ISF is thru
diffusion
- Rate at which H20 diffuses through the capillary membrane is about ___ x as fast as the rate of plasma flows through capillary.
- Rate at which H20 diffuses through the capillary membrane is about 80 x as fast as the rate of plasma flows through capillary.
- Pores are about ___ nanometers, about ___x the diameter of H20 molecules
- Pores are about 6-7 nanometers, about 20x the diameter of H20 molecules
About ___ of the total volume of the body consists of spaces b/w cells which are called the interstitium
About 1/6 of the total volume of the body consists of spaces b/w cells which are called the interstitium
Interstitium & ISF - 2 major structures
Interstitium & ISF - 2 major structures
•Collagen fiber bundles
•Proteoglycan filaments
- Collaged extend long distances in the interstitium
- Extremely strong and provide most of the tensional strength of the tissues
- Collagen fiber bundles
part of IS & ISF
- Extremely thin parts of IS & ISF which are coiled or twisted molecules
- composed of about ___ and ___ (give % too)
- Look like “brush pile” on microscope
Proteoglycan filaments
- Extremely thin parts of IS & ISF which are coiled or twisted molecules
- composed of
- 98% hyaluronic acid
-
2% protein
- Look like “brush pile” on microscope
- Fluid comes from filtration and diffusion from capillaries, same constituents as plasma but much lower protein concentration b/c cannot pass easily through capillary
- ISF trapped in proteoglycan filaments
- Tissue gel
- free fluid amount is usually ___%
- Diffusion through gel occurs about ___ to ___% as rapidly as it does through free fluid
free fluid
- normally less than 1% but can expand tremendously with tissue edema until one half or more of the edema fluid becomes freely flowing fluid independent of the proteoglycans filaments
- Diffusion through gel occurs about 95-99% as rapidly as it does through free fluid
fluid filtration
- Colloid osmotic pressure cause fluid movement by ____ from interstitial space into blood
filtration
- Colloid osmotic pressure cause fluid movement by osmosis from interstitial space into blood
Movement of fluid volume from plasma & ISF determined by:
Starling forces
list and describe all straling forces variables and their function.. don’t let me down
-
Capillary pressure
- Forces fluid outward
-
Interstitial fluid pressure
- Forces fluid inward to capillary if positive, outward if negative
-
Plasma colloid osmotic pressure
- Osmosis of fluid inward through capillary membrane
-
Interstitial fluid colloid osmotic pressure
- Osmosis of fluid outward through capillary membrane
symbols for these
- Capillary pressure
- Interstitial fluid pressure
- Plasma colloid osmotic pressure
- Interstitial fluid colloid osmotic pressure
- Capillary pressure (Pc)
- Interstitial fluid pressure (Pif)
- Plasma colloid osmotic pressure (∏p)
- Interstitial fluid colloid osmotic pressure (∏if)
Net filtration pressure
- sum of 4 forces
- NFP =
Net filtration pressure
- sum of 4 forces
- NFP = Pc - Pif - (∏p) + (∏if)
-
multiply this by Kf (cap filtration coeff) to get get the rate of fluid FILTRATION.
- Filtration = Kf x NFP
NFP
- Sum is (+) – net fluid ____occurs across capillary
- Sum is (-) – net fluid _____from __ into ___
- normally which one + or -?
- Sum is (+) – net fluid filtration occurs across capillary
- Sum is (-) – net fluid absorption from interstitial spaces into capillary
- Normally slightly positive so flow into capillary