WEE4 4: CH 16--Microcirculation & Lymphatic Flashcards
–It is in the microcirculation where the MOST meaningful events occur—prior to and after microcirculation, the other blood vessels are simply a transport pathway.
–Gas exchange and nutrient/waste product exchange occurs between the blood in the microcirculation and the tissues.
KNOW
–Microcirculation primarily includes the 500 to 700 square meters (about 1/8th of a football field) of CAPILLARIES.
the arterioles as they progressively narrow toward the capillaries—these TERMINAL arterioles are called
_____________
metarterioles.
- Metarterioles have SMOOTH muscle fibers that _______ the vessels at intermittent points .
** Where the metarteriole meets the capillary, the smooth muscle fibers form the __________ sphincter which can open or close the opening of the capillary.
encircle
precapillary
Because the metarterioles and the precapillary sphinters are in close contact with the tissues they serve, the _____ _______ of the tissues controls the blood flow according to tissue needs. Control of blood flow is based on increasing or decreasing the diameter of the blood vessels.
local conditions
Microcirculation Structures
- __________ ____—single celled, highly permeable layer of endothelium surrounded by a thin basement membrane.
Capillary Wall
Microcirculation Structures
- _______- between individual cells that make up the capillary wall allow for small nutrient molecules and plasma fluid to
leave the capillary through these pores.
• Blood cells and plasma proteins are too large to fit through the pores.
Pores
Microcirculation Structures (PORES CONTINUED…)
Two small passageways:
a) __________ ______ (pores)— thin, curving channels
between cells. WATER, water- soluble ions and small solutes
can diffuse through these intercellular clefts.
b) ____________ (plasmalemmal vesiscles)—seemed to be formed on the cell membrane from PROTEINS (caveolins) associated with cholesterol and other lipid materials. They play a transcytosis role by engulfing small packets of plasma, or extra cellular fluid with plasma proteins, and transporting it slowly through the endothelium.
Intercellular cleft
Caveolae
Special Types of Pores
a) _________—tight junctions only allow extremely small molecules in or out.
b) _________—opposite of brain— has large pores so that even plasma proteins can pass.
c) ___________—smaller than liver but larger than brain.
d) ____________ —contain windows called fenestrae which allow tremendous amounts of small ions, but not large plasma proteins, to pass so the kidneys can filter the blood rapidly.
Brain
Liver
GI Liver
Kidney
Vasomotion
- Vasomotion is the type of blood flow through the _____________. Blood flow through these vessels is NOT continuous, it flows intermittently.
- The cause is intermittent opening and closing of metarterioles and precapillary sphincters.
- Regulation of vasomotion is primarily controlled by the ____ concentration in the tissues.
- When tissues use O2 at a greater rate, O2 concentration ↓ thus intermittent periods of flow occur more often.
capillaries
O2
Exchanges between Blood and Interstitial Fluid
- __________ is the primary method of transfer of water and dissolved ions between the capillaries and the interstitial fluid.
Diffusion
Exchanges between Blood and Interstitial Fluid
- ______ ______ is the space between cells and contains the fluid that provides a watery environment for cells.
Interstitial space
Exchanges between Blood and Interstitial Fluid
- Diffusion results from the “______ _______” of water molecules and dissolved ions as they randomly move in all directions between the capillary membrane and the interstitial fluid.
thermal motion
Things that have and effect on diffusion
1. ____ ________ _________—can diffuse directly through the capillary membrane and do NOT have go through the pores.
a) these substances include O2 and CO2
b) because they can diffuse directly across the membrane, they can diffuse at a much FASTER rate than lipid-insoluble substances
Lipid-Soluble Substances
Things that have and effect on diffusion
- Water-Soluble and Lipid-Insoluble Substances—must pass through the intercellular pores (clefts) that are located between the __________ cells of the capillary membrane.
a) these substances include water molecules, sodium ions, chloride ions and glucose
endothelial
Things that have and effect on diffusion
- Effect of Molecular Size (Weight)—permeability of capillary pores to substances of varying sizes has an effect on diffusion rate.
a) the ______ the diameter of the molecule (water) the faster it will diffuse; intermediate diameter molecules diffuse at a slower rate
b) ________molecules (plasma proteins) are not permeable in most organ cells but the _____ has pores large enough –thus, capillary permeability can vary depending on the function of the organ
smaller
larger
liver
Things that have and effect on diffusion
- Effect of ___________ Gradient—as with any gradient, substances will move more rapidly the greater the difference in concentration between the area of higher concentration and the area of lower concentration.
Example of O2 and CO2:
O2 is higher in the capillary blood than the interstitial fluid therefore, O2 moves from the blood toward the tissues.
Conversely, CO2 is higher in the tissue so it moves into the capillary.
Concentration
Interstitium
A. Collective of _______ located between all cells in the body—makes up about 1/6th of total body volume.
B. Contains two solid structures:
1. _________ fiber bundles to provide tensile strength against cells.
2. __________ filaments are thin filaments that form a mat to provide more substance
spaces
Collagen
Proteoglycan
The interstitial fluid contains similar components as plasma with the exception of a lower concentration of ________ because plasma _______ do not easily pass through the capillary pores.
proteins
proteins
(note: the interstitial fluid actually has a higher number of proteins but this fluid is in more quantity than plasma so the concentration of proteins is lower in interstitial fluid).
Because of the proteoglycan filaments and the vesicles containing fluids, interstitial fluid is the consistency of a____
gel.
**As a result of the gel, fluids and molecules do NOT flow through the interstitial fluid, they diffuse through molecule by molecule
Usually, there is a small percentage (< 1%) of free fluid in the interstitium, but when tissues develop _____, these rivulets of free fluid increase tremendously.
edema
Filtration vs. Absorption
The blood (hydrostatic) pressure in the capillaries tends to force fluids and dissolved ions through the capillary pores into the interstitial fluid—____________.
Filtration
Filtration vs. Absorption
osmotic pressure caused by the plasma proteins (colloid osmotic pressure) inside the capillary cause fluid movement by osmosis from the interstitial fluid into the blood—_____________
Absorption.
**The BALANCE between filtration and absorption prevents significant fluid loss from the blood into the interstitial fluid
There are four primary forces (called ______ _______) that determine if fluid will move out of the blood into the interstitial space (filtration) or from the interstitial space into the blood (absorption).
- Capillary pressure (Pc)—tends to force fluid OUTWARD from the blood
- Interstitial fluid pressure (Pif)—tends to force fluid INTO the blood when Pif is (+) and OUTWARD if Pif is (-).
- Plasma colloid osmotic pressure (Πp)—tends to cause osmosis of fluid INTO the blood.
- Interstitial fluid colloid osmostic pressure (Πif)—tends to cause osmosis of fluid OUTWARD from blood.
Starling forces
If the sum of the Starling forces (net filtration pressure—NFP) is ________, there will be a net fluid FILTRATION—from blood INTO interstitial fluid. If the sum of the Starling forces is _________, there will be a net fluid ABSORPTION from the plasma INTO the interstitial fluid
positive
negative
Hydrostatic pressure (Pc) forces fluids ____ of the blood on the ARTERIOLE end of the capillary.
- Because of the _______ concentration of plasma proteins in the blood, this creates an plasma colloid osmotic pressure (Πp) which re-absorbs water back INTO the blood via osmosis on the VENULE end of the capillary
- The excess fluid in the interstitial fluid must be returned to blood circulation via the ________ system
out
higher
lymphatic
**Net filtration of fluid OUT of the capillary into the interstitial fluid is HIGHER than net absorption of fluid back into the capillary.
Abnormal Imbalance of Forces
- If the fluid amount is higher than what the lymphatic system can carry back to blood circulation, the concentration of fluid in the interstitial spaces causes
_____ - If mean capillary pressure _____, net reabsorption increases resulting in more fluid coming inward to the blood causing an increase in blood volume.
edema.
falls
Lymphatic System
This system provides an accessory route for fluids to flow from the interstitial fluid back to the circulatory system.
• Most importantly, lymphatic vessels can carry ______ and other large substances back to the blood.
• Returning plasma proteins back to the blood is essential for life.
proteins
Lymphatic System
Lymph vessels from the _____ part of the body empty into the thoracic duct which then empties into the venous system at the juncture of the left internal jugular vein and the left subclavian vein
lower
Lymphatic System
- Lymph from the LEFT side of the head, left arm and parts of the left thorax enters the thoracic cavity and then the two veins.
- Lymph from the RIGHT side of the head and neck, right arm and parts of the right thorax enter the right lymph duct and then enter the venous system at the right subclavian vein and right internal jugular vein.
KNOW LEFT VS RIGHT
Most of the fluid that filters out of the arteriole side of the capillaries is reabsorbed on the VENULE side of the capillary bed. However, about one-tenth of the fluid is NOT reabsorbed and enters the lymphatic capillaries and returns to the blood via the ________ vessels rather than via the venules and veins.
•The total amount of lymph made from the intersitital fluid is 2 to 3 liters per day.
lymphatic
Structure of Lymphatic Capillary
- Anchoring filaments—attached to the endothelial cells of the lymphatic capillary.
- “_______”—the endothelial cells of the capillary overlap so that the overlapping edge can flap inward.
- The interstitial fluid containing proteins can push the flap open allowing flow into the capillary and then the backflow closes the “________”.
Valve
valve
Formation of Lymph
Lymph is originally derived from fluid
interstitial
Formation of Lymph
Most tissues have a protein concentration of 2 g/dl in the interstitial fluid surrounding them. However, some organs, like the ______, have a higher protein concentration (6 g/dl).
liver
Formation of Lymph
- Lymphatic vessels pick up nutrients (including ALL ______) from the digestive tract before they enter blood circulation.
- Bacteria can also enter the lymphatic vessels and as they pass through the lymph nodes, most bacteria is _______
lipids
destroyed
Lymph Flow
______ Pump—the valves described earlier are used to not only trap fluids, proteins, nutrients, etc., they are used as a pump. The filling of one vessel causes it to contract and the fluid is pumped through the next valve to the next vessel—even throughout the collecting vessels.
Internal
Lymph Flow
___________ Pumps
•Contraction of surrounding skeletal muscle
•Pulsation of adjacent arteries
•Movement of parts of body
External
