Fewell - Microcirculation, Lymphatic System & Starling Forces 2021.pdf Flashcards
why are right anf left coronary blood flows different?
The left pump has to work harder than the right pump
>because metabolic demand is higher for the left pump
>left heart has to generate higher pressure transmural pressure drops to almost zero and have to generate more pressure to componsent???
Myocardial Oxygen Supply & Demand
In the normal heart, the oxygen requirements of the myocardium
are continuously matched by the coronary arterial supply
Major Determinants of Myocardial
Oxygen Consumption
- Heart Rate
- Wall Stress (Systolic Pressure)
- Cardiac Contractility
coronary blood flow and myocardical oxygen consumption have a ___ relationship
linear relationship
components of myocardial oxygen supply
- O2 content
- coronary blood flow
determinants of coronary blood flow
-coronary perfusion pressure
-coronary vascular resistance
>external compression
>intrinsic regulation
regulating coronary microvascular tone (resistance)
balance between vasodilator and vasoconstrictor signals
>exerted by: neurohumoral, metabolic, exxtravascular, endocrine, paracrine and endothelial influences
Macrocirculation
circulation of
blood to and from organs
Microcirculation
vasculature
embedded within organ tissues
and composed of arterioles,
capillaries and venules
slide 3 figure
**8 maybe a question???
circulatory system has blood vessels that are all lined with ____
all blood vessels are lined with endothelial cells
that are continuous with the endothelial lining of the heart
arterioles
(aka resistance vessels in
the circulation) are highly muscular and
their diameters can change many fold
metarterioles
(i.e., the terminal
arterioles) do not have a continuous
muscular coat but smooth muscle fibers
encircle the vessel at intermittent points
precapillary sphincter
At the point where a capillary originates
from a metarteriole, a smooth muscle
fiber usually encircles the capillary
vasomotion
intermittent
contraction of metarterioles and precapillary
sphincters (likely regulated by O2 in tissue)
Capillaries walls
thin and constructed of a single layer
of endothelial cells surrounded by a thin basement membrane
(exchange vessels)
Diffusion definition
most important method of capillary exchange
• Lipid soluble [nonpolar] substances such as oxygen, carbon dioxide, steroid hormones) – across lipid bilayer wall
(water!!)
clefts/fenestrations allows entry of substance via
Small water soluble substances [ions & polar] such as glucose &
amino acids) – clefts or fenestrations (water!!)
Transcytosis
allows transport of large molecules across capillary
walls (large lipid insoluble molecules & protein hormones)
Bulk Flow
> transfer of fluids across capillary walls
regulates the relative volumes of blood and interstitial
fluid (regulated by Starling Forces)
Continuous Capillary
Lipid-soluble substances diffuse directly through the cell membranes of the capillary endothelium e.g., oxygen & carbon dioxide, H2O, ions >found in the heart
Fenestrated Capillary
Water-soluble, non-lipidsoluble substances diffuse
through intercellular clefts
and fenestrations in the
capillary membrane
e.g., H20, Na+, Cl-, glucose
>pinocytic vessicles can transport larger substances
Discontinuous Capillary
Plasma proteins pass through these walls almost as easily as water and other substances. Note large intercellular clefts and pores and incomplete basement membranes
what determine filtration across capillaries
by Capillary and Interstitial
Fluid Pressure & Colloid Osmotic Pressure (thanks to Ernest Starling)
Lymphatic System functions
maintenance of fluid balance in the internal environment
and immunity
> to provide an accessory return route to the blood for the surplus 3L
capillary filtration
removes plasma while leaving blood cells from circulatory system
where does filtered plasma go?
reabsorbed directly into the blood vessels,
while the remaining 3L remain in the
interstitial fluid
pinocytic vessicles
> can transport larger substances
> found in fenestrated capillaries
aterial end has _ starling forces
-greater capillary hydrostatic pressure than colloidal osmotic pressure
>filtration
>(+10 mm Hg)
mid capillary end has _ starling forces
-capillary hydrostatic pressure is the same as collodial osmotic pressure
>no net movement
> (0 mm Hg)
venous end has _ starling forces
-blood colloidal osmotic pressure is greater than capillary hydrostatic pressure
>reabsorption
> (-7mm Hg)
without lymphatic system there would be an
accumulation of fluid in interstitial space
does the lymphatic system include the heart
yes
