lecture 8: guyton chapter 16/17 Flashcards
what are the 4 forces that contribute to starling equilibrum
capillary hydrostatic pressure interstitial fluid hydrostatic pressure osmotic force (plasma proten conc) osmotic force (iterstitial protein)
what is the capillary hydrostatic pressure due to
due to the BP within the capillary (increase pressure, more force/filtratioin into the instersticium)
which pressure value is llways negatice
interstiial fluid hydrostatic pressuer
interstial fluid hydrostatic pressure pushes fluid up or out
pushes flud=ud back to the cpaillary
what 2 forces increase filtration
cap hydrostatic pressure
osmotic force due to interstital fluid plprotein concentration
what 2 forces increase reabsorbition
intertitial fluid hydrostatic pressure
osmotic foce force due to plasma protein concentraion
what is lymph and where is it found
is a fluid (like blood) found in lymph vessels (similar to veins) that conntrians some proteins that have escaped through capillary walls
what does the lymphatic system move
moves interstial fluid with proteins
true or falseL tthe lymphatic system is interconnected with capillary system
true
what size are the proteins that escape the cpaillary walls and why
they are usually small because others have a hard time passing through the fenestarions of capilaries
lymphatic sytse=m is an open or closed ended entwork
close ended (just appears)
lymph capillaries are highly permeable or not highly
they are highy permeable
lymphatics lack what in compoarionn to capillaries
lack tight junctions
why is lymphatics not havinng tight junctions a good thing
therefore larger ptoteins can easily get in
how are lymphatnics attached to connective tissue
finne filament anchors to connective tissue
where does lymph drain
at the level of the vena cava (mixes with blood)
what is the general flow of fluid
capillary inntersitum lymphatic system (flow) to lymphnodes (for filtration) vena cava (with clean fluid)
the lympathic makes an accessory route by what
by which fluid protein can flow from intnerstium to the blood
the lympathic system is important in prventeing what
edema
what is a majo rorute for the absroption of nutriends from the GI tract
lymphatic systtem
why is the lymphatic system imporant route for absoption of nutrients from the GI tract
since large proteinns cannot pass trhough capillaries but it is easier to pass thrgouh lymph (nno tight junctions)
true or false and why: the lymphatic system provides a important rule in ummune system
true
when the fluid passes though the lymphnodes (which gets fitlrated) and the unwanted things like bacteria, eccess lipids, proteins get caught inn lymph
=cleans fluid
what is the negative pressure in the innterstital fluid socae caused by
pumping by lympatic sysm
plasma filtrate is returned to the circulation by what (4 ways)
tissue pressure
intermitted skeltal muscle actvitiy
lymphatic vessel contraction
system of one what valve
whatt are some elements that get returned back into the circulation due to the lymphatnics
prottein (albmin)
bacteria
fat
excess fluid
what does the degree of activtiy of lymphathic pump depend on
(determinants of lymph flow)
smooth muscle filmanets in the lyph vessels cause them to contract
external compression also contributes
true or false: lymph vessels do not have smooth muscle filaments
false
what makes the valves of the lympaticic sytem
elongated endothelial in lympnodes
what arte the 2 phases of movement of lymph
expansion phase
compressio phase
explain the expansion phase of movement of lymph
Fluid travels from intersttitisum into the lymph (no tight junctions so itd easier)
hydrostatic pressure in the intersitcium exceeds sthat inside lymphastic causing microvalves to open and fluid to enter
explain the compression phase of the movement of lymph
the hydrostatic pressure inside the lymph rises, closing the microvalves ans causing lymph to flow downstream (froward) so valves can open again
what is the highest driving force of moving lymph/main determinant
interstitial fluid hydrostatic pressure
if there is an icncrease in interstitual fluid hydrostatic pressure, there is an increase or decrease in lymph flow
increase
the more fluid is travelling into the intersitum (filtration) what happens to the flow
more lymph flow
what are the factos affeccting the formation of interstiaial fluid
capillary hydrostatic pressue (more filtration)
colloid osmotid pressure (putting more fluid in the interstitum)
lymph return
capiliary permiability
what are the factors that increase hydrosttic pressure
Impaired venous return Congestive heart failure Constrictive pericarditis Ascites (liver cirrhosis) Venous obstruction or compression Thrombosis External pressure (e.g., mass) Lower extremity inactivity with prolonged dependency Arteriolar dilation Heat Neurohumoral dysregulation
explain how an increased hydrostatic pressue can lead to an impaired venous return (vice versa)
there will be a smaller pressure gradient therefore the heart needs to but more pressure to contract
explain ho w congestive heart failure and constrictive pericarditis
heart is not pumping blood properly, the blood startts to back up in veous size
explain how heat can cause an increased hydrosttic pressure
vasodiliation, icnrease flow/rate, increase filtrattion
herreohprage is a long term or short term solution
short term
when you are hemmoraging what is happen to the pressure
there is a low fluid pressure (low cap hydro) but a normal osmotic prssure (blood is lost but the concentration of proteins has not changed)
explai nthe hemmorage mechanism
1) bllod is lost so the force tthat drives fluid from the capillaries is diminued (less filtration) but the force that moves the fluid back into the capilaries is not altered (force differential)
this movement provides a homeostatic adjustment which restores fluid volume
(to rebuild the plasma volume there will be an increased reabsoption of fluid from interstium to capilary
=eventually the plasma colloid will decreae pbecause it is diluted with fluid
when you are starving, what is hapening in terms of presure
normal fluid pressure but low osmotic pressure (arent getting enough food, body will use plaasma proteins for energy)
plasma proteins are always used for energy
false, a last resortt for energy
when you use plasma proteins what happens to the pressur
decreases capiliarry absorption (lower osmotic pressire)
explain pressure and starvation
When you are stariving you have a normal fluid pressure but low osmotic pressure (not enough proteins in the blood)
to increase the concentration in the capillary, more water will enter the tissue than pulled back (swelling.edema)
exp[lain why swelling/edema happens when starving
because low concentration in blood so more water will move to tthe tissues causing swelling
in starvation that is more or less filtration than reabsorb
more filtratiton
what happens if your lymphnodes are blocked
there is no draining causing a build up of fluid
explain elphantitus
a parasite blocks flow of lymph and feeds of lipids and proteins and is growing which causes swelling
regulation of perepheral blood flow is a uni or dual control
dual (intrinsic and extrinsic)
what are the 2 ways we control how bllod gets to perphery
extrinsinc and intrisinc
what system is responsible for extrisinc control of peripheral blood blow
primarily by nervous system (also by hormones)
intrisic control of peripheral blood bflow occurs where
locally in the tissues
what is intrinsic control of perepheral blood flow controlled by
controlled by the conditions in the immediate viscinity of the blood vessels
what are the 4 tissue needs
delivery of oxygen
2) delivery of nutrients such as glucose, amino acids, etc.
3) removal of carbon dioxide, hydrogen and other metabolites from the tissues
4) transport various hormones and other substances to different tissues
flow is closed related to what
metabolic rate of tissues
what is the reason for control of blood flow
REASON: Body needs various amounts of nutrient delivery and metabolic removal for different levels of activity
ig a tissue has a high activity is needs w BLANK blood flow
high
whatt is the principle behind control of blood flow
Blood flow is regulated to minimal level to just meet needs – body will not ‘waste’ blood
(metabolic need determines how much blood the tissue recevies)
explain tissue blood flow at restt
at rest, tthings like skeletal muscles dont need to be perfused /filled iwth oxygen so the sphnicts will constrict tbecause metabolic need is determining flow
at rest, organs will be taking up more of the flow
what is the main factor in acute control of local blood flow
tissue metabolic acitivity
what is one of the most fundemental principles of circulartory function
the ability of each tissue to control its own local blood flow in proportion to its metabolic needs
if there is an change that results in an inadequate oxygen (nutrient) supply for the metabolic requirements of the tissues results in what
the formation of vasodilator substances which increase blood flow to the tissues
what are the 2 major thereories for local blood flow (acutte control)
The vasodilator theory - Increases in tissue metabolism lead to increases in blood flow
2) Oxygen demand theory - Decreases in oxygen availability to tissues increase tissue blood flow
what are the vasodilators in the vasodilator therory
Adenosine, CO2, Lactic acid, ADP compounds, Histamine, K ions, H ions
explain the vasodilator theory for blood flow conttrol
increase tissue metabolism (increase tissue needs, increase conbustion)
=incrrease release of vasodilators
=decrease arteriole resistance
=increase blood flow
what is the oxygen demand theory for blood flow control
increase tissue metalosim or decrease oxugen delivery to tissue
=decrase tissue oxygen concentrration
=decrease arteriole resistnce
=increase blood flow
what structures controls local blood flow by sensing changes
precapilary shincters
explain acute local feedback control of blood flow (sphincs)
if there is a change (lack of oxygen, formation of vasodilatesr ettc), the precapilary sphincters will relax (relation of smooth muscle) to increase blood flow
what is an example of metabolic control of local blood flow
active hyperemia
increased blood flow to meed increase metabolic needs
true or false: there will be a maximal flow for increasing metabolic activties
true
will your body stay in active hyperemeia after increased metabolism for a pronglued period
no, eventually itt will adapt
ehat is an example of oxygen demand contrtol of local blood flow
reactive hyperemia
explain reactive hyperemia
If there is an occlusion/block, there wil lbe a lack of oxygen to the cells and will cause the sphincts to fully dilatet and allow an icreased flow
what is the realtionship between peak blood flow and duration of hyperemia
they proportional to tthe duraction of the occlusion
what does autoregulation mean
intrinsic ability of a tissue to maintain blood flow relatively constant over a wide range of arterial pressures.
what is a possible explanation for autoreg.
q/f= pa-pv/r
be able to explain the autoregulation slides
metabolic theory suggests taht as arterial pressure is decreased, oxygen/nutrient deliver is BLANK
is decreased resulting in release of a vasodilators
if there is a decrease of oxygen or nutrients, what will be released
vasodilator
myogenic theory proposes that as arteiral pressure falls, what happens to the arterioles
have an intrinsic property to dialte in response to decrases in wall tension
what is the mechanism for blood flow control in the kidneyts
they have a feedback system between the tubules and arterioles
what is the mechanism for the brain blood flow
controlled by carbon dioxde and hyderogen ion concentration
what is the theory to explain metablic mecahnism
When the pressure in a vessel to a tissue increases, the flow increases, and excess oxygen and nutrients are provided to the tissues. These excess nutrients cause the blood vessels to constrict and the flow to return nearly to normal despite the increased pressure.
what is the theory to explain myogenic mechanisms
When the lumen of a blood vessel is suddenly expanded, the smooth muscles respond by contracting in order to restore the vessel diameter and resistance. The converse is also true.
Proposed mechanism is stretch of vascular smooth muscle causes activation of membrane calcium channels.
Consequently, vascular smooth muscle cells depolarize when stretched.
know the slide about theroy to ecxplain myogenic mechanism
.
true or false; Vessels are “built to withstand the wall tensions they normally “see”
true
if intravascular pressure increases, what happens to the vessel wall tension
it will increase
if intravascular pressure increases and the vessel wall tension alsp increases, what happens to the muscles of the vessels
the vascular smooth muscle contracts and the ttension returns to normal
what is the law of LaPlace
radius defines tension (increase radius, increase tension)
For given BP, increasing the radius of the vessel leads to BLANK
a increase in tension.
why do arteries needtthicker walls than veins
because they carry much higher BP (more tension)
true or false: because capillaries also carry significant BP they have thick walls
false, because of thei small size, there is reduced tension to the thick walls is not needed
does the endothelium play an active role in what
in regulationg the microcirculation
explain why the endothelium is important in regulation microcirculation
Endothelium is a source of substances that elicit contraction or relaxation of the vascular smooth muscle
sends substances to tunica media to allow for vasodilation and contriction
what are some vasoactie substances realased from endothelium
Nitric Oxide (NO) (Endothelium-derived relaxing factor) Prostacyclin Endothelin Endothelial-derived hyperpolarizing factor (EDHF)
long term or acute regulatory mechanisms that control blood flow are more effective
long ter,
how does long term local blood flow regulation occur
by by changing the degree of vascularity of tissues (size and number of vessels).
what is an important stimulus for regulating tissue vascularity
oxygen
what is angiogenesis
growth of new blood vessels
Angiogenesis occurs in response to angiogenic factors released from where
ischemic tissue
2) rapidly growing tissue 3) tissue with high metabolic rates
what are most angiogeneic factors
small peptides such as vascular endothelial cell growth factors (VEGF) and fibroblast growth factor (FGF).
why is long term regulation of blood flow more effective than short term
it can withstand even larger pressure changes
