Unit 2 - Blood Flow & Blood Pressure PART G Flashcards
What happens to the excess ISF that was reabsorbed by the capillaries (~3 L/day)?
The excess ISF that was not reabsorbed by the capillaries (~3 L/day) enters blind-ended lymphatic capillaries, part of the lymphatic system.
Lymphatic capillaries
blind-end lymph vessels; lie close to all blood capillaries except those in the kidney & CNS
The fluid that circulates through the lymphatic system (lymph) will…
pass through lymphatic vessels and lymph nodes, before retuning to the the blood stream via lymphatic ducts that empty into veins near the jugular veins.
Lymph
clear fluid; once inside the lymphatics
Lymph nodes
bean-shaped nodules of tissue with a fibrous outer capsule & an internal collection of immunologically active cells, including lymphocytes & macrophages
Failure of this system, or disease states affecting one or more of the Starling forces produce
EDEMA
Edema
is an accumulation of interstitial fluid in the tissues
Edema can result from:
- Obstruction of lymph vessels
- Increased Net Filtration Pressure (Net P)
- Decreased Net colloid osmotic pressure (Net π)
- Obstruction of lymph vessels
a. Elephantiasis – mosquito-borne fliaria worms block lymphatic flow
b. Removal of lymph nodes (creates scarring and blockage of lymph vessels)
The lymphatic system has…
NO single pump like the heart
- lymph flow depends primarily on waves of the larger lymph vessels
- flow is aided by contractile fibers in the endothelial cells, by the one-way valves, & by external compression created by skeletal muscle
What is an imp. reason for returning filtered fluid to the circulation?
the recycling of plasma proteins
- the body must maintain a low protein concen. in the interstitial fluid b/c colloid osmotic pressure is the only sign. force that opposes capillary hydrostatic pressure
- if proteins move from the plasma to the interstitial fluid, the osmotic pressure gradient that opposes filtration decreases
- with less opposition to capillary hydrostatic pressure, additional fluid moves into the interstitial space
Edema 2 causes:
- inadequate drainage of lymph or
2. blood capillary filtration that greatly exceeds capillary absorption
What are patients with edema told to do?
pateints with edema in an injured limb are told to elevate the limb above the level of the heart so that gravity can assist lymph flow back to the blood
What is edema a sign of?
a sign that normal exchange b/t the circulatory system & the lymphatics has been disrupted
Increased Net Filtration Pressure (Net P)
a. Heart failure promotes VENOUS POOLING, backing up blood into the capillaries, increasing PC
(when capillary hydrostatic pressure ↑’s, filtration greatly exceeds absorption, leading to edema)
Decreased Net colloid osmotic pressure (Net π)
a. Could result from liver disease (decreased plasma protein production) and kidney disease (increased protein excretion = proteinuria), or severe malnutrition (decreased protein intake) all of which decrease πC
b. Histamine dilates arterioles (↑’s PC) and ↑’s intercellular pore size (increases capillary permeability for proteins, increasing πI)
Heart Failure
a condition in which 1 ventricle loses pumping power & can no longer pump all the blood sent to it by the other ventricle
Histamine
released in the inflammatory response makes capillary walls leakier & allows proteins to escape from the plasma into the interstitial fluid
- the local swelling that accompanies a region of inflammation is an ex of edema caused by redistribution of proteins from the plasma of the interstitial fluid
What is an ex of a situation in which the balance of colloid osmotic & hydrostatic pressure is disrupted?
inflammation
On occasion, changes in the balance b/t filtration & absorption help the body…
maintain homeostasis
