lymphatics and tissue exchange Flashcards
intrinsic control of arterioles
Control of local blood flow:
-level of metabolites in surrounding tissue (CO2=dilate)
-Autoregulation (steady blood flow to tissues despite changing arterial pressures)
-Active hyperemia (increase in metabolism/demand of organs causes dilation and increased blood flow)
(Arterioles usually determine total peripheral resistance by controlling flow of blood into capillaries into organs)
Extrinsic control of arterioles
Sympathetic Nervous System
Endocrine System (Angio II and NE are strong hormones causing vasoconstriction)
Why is simple diffusion the most common way to cross the capillary walls?
Simple squamous cells take up more surface area than the small clefts in between them
Moving through clefts: must be water soluble (ions, glucose, amino acids)
Moving across membrane: must be lipid-soluble gases such as O2 and CO2
What organs are the exceptions to requiring vesicular transport?
Kidney and Intestine: fenestrated capillaries allow for larger proteins to move across
Why doesn’t water always follow sodium ions?
ex: certain parts of the kidney are non permeable to water (aka don’t have aquaporins)
Blood Hydrostatic Pressure
Pressure that is exerted by fluid within an enclosed space (capillary or interstitial)
-capillary hydrostatic pressure pushes fluid out of capillaries, interstitial hydrostatic pressure pushes fluid into the capillaries
Oncotic Pressures (AKA colloid osmotic pressure)
Caused by proteins, which pull fluid towards them
-most proteins are inside capillary (normally very little in interstitial spaces)
What do you call the buildup of fluid in interstitial spaces?
lymphedema
Filtration coefficient and Reflection coefficient
FC: water permeability of capillary walls
RC: Capillary’s permeability to proteins
Causes of Edema: Heart Failure
Blood cannot get pumped out efficiently, so it backs up in capillaries
This increases the capillary hydrostatic pressure causing fluid to leak out into the lower limbs
-why lower limbs? less return to the heart
-(elevating the feet with edema can help return blood flow to the heart)
Causes of Edema (cont.)
Infections, toxins or burns
-cause clefts to become larger form the damage, thus increasing the filtration coefficient and letting more water out
Causes of Edema (cont.)
Blockage of lymph system
-allows proteins to build up in interstitial space
-increases the interstitial oncotic pressure
-pulls water out of capillaries
-lymphedema occurs
Causes of Edema (cont.)
Decrease in plasma protein
-liver failure (creates proteins)
-Protein malnutrition
-Kidney disease
All of these situations result in decreased capillary oncotic pressure due to lack of proteins in the bloodstream
-Same result as protein buildup in lymph, just different process
3 types of passive transport
-Diffusion
-Facilitated diffusion
-Osmosis
T or R: Facilitated Diffusion used non-specific channels as well as very specific channels
T
Active Transport: 2 types
Primary: Uses ATP (sodium/potassium pump [3 Na+ out, 2 K+ in])
-against concentration gradient
Secondary: Does NOT use ATP, instead uses electrical gradient produced by primary (Na/K pump which produces gradient)
how is lymph fluid moved throughout the lymphatic system?
Pulsation of nearby artery and skeletal muscles (like skeletal muscle pump, also has valves)
Purpose of lymphatics
Return fluid/large molecules to the heart
Immune surveillance/blood filtration
Everyday about 20 liters of fluid leaks out of cells into interstitial spaces. About 17 liters quickly get reabsorbed. What happens to the remaining 2-3 liters?
Returned to the blood stream (dumped into veins) by lymphatic system
Lymphatic vessel anatomy:
Capillaries are very permeable: made up of single endothelial cells that loosely overlap and form one-way minivalves
capillaries are secured by collagen filaments allowing them to be flexible but maintain shape
Movement of lymph:
Lymph capillaries
Lymph vessels
Lymph trunks
Lymph ducts
Lymph system: 9 trunks (named after area they drain from)
TEST: see lymph system pwpt slide 10 (Image)
2 lumbar trunks
2 bronchomediastinal trunks
2 subclavian trunks
2 jugular trunks
1 intestinal trunk
From the trunks it drains to the ducts
2 major lymphatic ducts:
Right lymphatic duct:
-collects lymph from right arm, right side of head and chest
-drain into the junction of the right jugular vein and right subclavian vein
Thoracic duct:
-collects from everywhere else in the body
-Drains into the junction of the left jugular vein and left subclavian vein
Side Note: Gut Associate Lymphoid Tissue (GALT)
(NOT test material)
The gut-associated lymphoid tissue (GALT) is the largest mass of lymphoid tissue in the body. It consists of immune cells such as B and T lymphocytes, macrophages, antigen-presenting cells, including dendritic cells, and specific epithelial and intra-epithelial lymphocytes.
