1. Microcirculation and lymphatic system

2. Microcirculation Most purposeful function of circulation
Nutrient transport
Cell excreta removal
Regulation of blood flow
Small arterioles
Local conditions within the tissue
Diameter of arterioles

3. Structural organization
Organ-specific
Meet its demands
Nutrient artery
Braches 6 to 8 times
Arterioles

4. Structural organization
Arterioles
Highly muscular
Changes in diameter
Metarterioles (terminal arterioles)
Smooth muscles
No muscle sheath

5. Structural organization
True capillary
Smooth muscle fibers
Precapillary sphincter
Venules
Larger than capillary
Weak musculature

6. Metarterioles and precapillary shincter
Close contact with tissue
Regulation of blood flow
Local condition of tissues

7. Capillaries Capillary wall Diameter Extremely thin 4 to 9 micrometer
Highly permeable
Single endothelial cell layer
Basement membrane
Diameter
4 to 9 micrometer
Barely large enough passage for RBC and other cells

8. Movement of solute and water
Intercellular cleft
Thin slit, curving channels
Large amount of transport activity
Plasmalemmal vesicles
Endocytosis
Picnocytosis
Vesicular channels
Little of important

9. Specialization Brain Liver GI capillary membrane
Blood-brain barrier (tight junctions)
Only small molecules can pass
Liver
Larger pores and slits
GI capillary membrane
Intermediate in size
Glomerular tufts of kidney
Fenestrae (oval window)
Large amount of small molecules and ions

10. Vasomotion Capillary flow Intermittent rather than continuous
Intermittent contraction of metarterioles and precapillary sphincter
Regulated by oxygen concentrations
Decrease in oxygen concentration (greater tissue demand), increase in vasomotion (increased frequency with longer duration)

11. Exchange of solutes and water
Diffusion
Most important method of transfer
Results from thermal motion of the water molecules and solutes in the fluid

12. Movement of lipid-soluble substances
Direct diffusion
No pores required
Oxygen
Carbon dioxide
Faster than lipid-insoluble materials
Require facilitation

13. Water-soluble materials
Intercellular cleft
Extremely efficient
Cleft occupy 1/1000 of the entire capillary surface area
Diffusion of water is 80X faster than flow of plasma itself

14. Substance Molecular Weight Permeability
Water
NaCl
Urea
Glucose
Sucrose
Insulin
Myoglobin 17,
Hemoglobin 69,
Albumin 69,
Molecular size
Different permeability
Tissue capillary-dependent

15. Concentration gradient
Greater the difference in concentrations between inside and outside, faster the rate of diffusion
Rates of diffusion of most nutrients
Much greater than other materials
Require small concentration differences

16. Interstitium and interstitial fluid
Space between the cells
Structures
Collagen fiber bundles
Tensional strength
Proteoglycan filaments
Thin, coiled/twisted molecule (98 % hyaluronic acid, 2 % protein)
Forms brush pile (reticular filaments)

17. Interstitial fluid Filtrate and diffusion of plasma components
Same constituents but lower concentrations of proteins
Entrapped in minute space along proteoglycan filaments
Formation of tissue gel
Diffusion of fluid and molecules
Very rapid

18. Interstitial fluid Free fluid Edema Very small amount (less than 1 %)
Expansion of fluid stored in the interstitium until 50 % of fluid becomes free of proteoglycan
Rivulets
Pockets

19. Fluid filtration across capillary
Pressures
Hydrostatic
Physical pressure that forces fluid and solutes out of capillary via pores
Osmotic
Concentration gradient of plasma proteins
Movement of fluid out of interstitial space
Regulates amount of fluid being moved out of blood

20. Role of lymphatic system
Return of excess fluid and proteins to blood
Leakage into interstitial space

21. Hydrostatic and colloid osmotic forces
Determination of fluid movement through capillary
Four forces
Capillary pressure (outward movement of fluid)
Interstitial fluid pressure (inward movement of fluid)
Capillary colloid plasma osmotic pressure (inward movement of fluid)
Interstitial fluid colloid osmotic pressure (outward movement of fluid)

22. Net filtration pressure
Sum of these forces
Fluid filtration to the interstitium if positive
Fluid absorption to the blood if negative
NFP = Pc-Pif-p+ if

23. Other factors Filtration coefficient (Kf) Filtration = Kf X NFP
Pore size
Pore number
Number of capillaries
Filtration = Kf X NFP

24. Lymphatic system Accessory route
Flow of fluid from interstitium to the blood
Movement of proteins and large particles away from tissue to the blood
Extremely critical
Lethal if no movement
Drainage
Channels
Not present on skin, the CNS, endomysium, and bones
Prelymphatics

25. Thoracic duct
Common drainage of lymphatic ducts in the lower body and left side of head, left arm, and chest
Drains into left internal jugular and subclavian vein

26. Right side of the body 10 % of arterial blood Right lymph duct
Empty into right internal jugular and subclavian vein
10 % of arterial blood
Enters lymphatic capillaries
Returns through lymphatic system
Removal of proteins

27. Structural design of lymphatic capillary
Anchoring filaments
Formation of valve

29. Lymph formation Derived from interstitial fluid Same composition
Differences in protein concentrations
Average 2g/dl (most tissues)
As high as 6g/dl in lymphs from the liver
3-4g/dl in lymphs from the intestine
Used for nutrient absorption
Lipids
Infectious agents
Destroyed

30. Rate of lymph flow 100 ml per hour through thoracic duct
20 ml per hour through other channels
120 ml per hour
2-3L per day
Increased interstitial fluid pressure, increased lymph flow
Changes in balance of fluid exchange

31. Lymphatic pumps Rate of lymph flow
Contraction of smooth muscles surrounding lymphatic and large lymph ducts
Compression of lymphatics
Rate of lymph flow
Interstitial fluid pressure X activity of lymphatic pumps

32. Regulation of interstitial fluid
Protein level
Accumulation of plasma proteins in the interstitium
Small but continuous leakage from the capillary
Alters colloid osmotic pressure
Alters fluid filtration rate and cause fluid accumulation
Alters interstitial fluid pressure and volume
Increased flow of lymph
Removal of proteins