1. MICROCIRCULATION AND LYMPHATIC SYSTEM
CAPILLARIES
MICROCIRCULATION AND LYMPHATIC SYSTEM 1

2. Capillaries *Are smallest vessels with thin wall
*Microscopic capillary networks are highly
permeable to all water , cell nutrients and
cell excreta between the tissues tissues and circulating blood
*Chemicals and gases diffuse across walls 2 2

3. Functions of Capillaries
*Permit diffusion of:
water
small solutes
Lipid-soluble materials
*Block:
blood cells
plasma proteins 3 3

4. Capillary Function
*it’s the Location of all exchange functions of cardiovascular system
*Materials diffuse between blood and interstitial fluid 4 4

5. Capillary Structure - Endothelial tube, inside thin basal lamina
- No tunica media
- No tunica externa
*Diameter is similar to red blood cell 5 5

7. Transport across capillary wall
Endothelial cell
Interstitial fluid
Water-filled pore
Plasma proteins
generally cannot
cross the capillary
wall
Plasma
Plasma
proteins
Plasma
membrane
Lipid-soluble
substances
pass through the
endothelial cells
O2, CO2
Cytoplasm
Exchangeable
proteins
Na+, K+, glucose,
amino acids
Exchangeable
proteins are
moved across
by vesicular
transport
FIGURE 10-16: Exchanges across the capillary wall. (b) As depicted in this schematic representation of a cross section of a capillary wall, small water-soluble substances are exchanged between the plasma and the interstitial fluid by passing through the water-filled pores, whereas lipid-soluble substances are exchanged across the capillary wall by passing through the endothelial cells. Proteins to be moved across are exchanged by vesicular transport. Plasma proteins generally cannot escape from the plasma across the capillary wall.
Small, water-soluble
substances pass
through the pores
Fig b, p. 292 7

8. Capillary structure Capillary pores (Intercellular cleft) Plasmalemmal vesicles Vesicular channels

9. Special types of (pores) in certain organs
1.Brain ,blood brain barriers tight junction
2.Liver very wide
3.GI capillaries, midway in size between
muscles and liver
4. Glomerular capillaries of the kidney, Fenestrate ; small oval windows penetrate through middle of endothelial cells 9 9

10. Capillary Networks
Figure 21-5 10 10

11. Capillaries Networks Capillary bed or capillary plexus
Connect 1 arteriole and 1 venule 11 11

12. 12

13. Collaterals *Multiple arteries that contribute to 1 capillary bed
*Allow circulation if 1 artery is blocked
Arterial anastomosis:
=> fusion of 2 collateral arteries 13 13

14. 0.5 500 4.5 6,000 5 Velocity of flow (mm/sec) Anatomical distribution
Total cross-sectional
area (cm2)
Blood flow rate
(liters/min)
0.5
500
4.5
6,000 5
Aorta
Arteries
Arterioles
Capillaries
Venules
Veins
FIGURE 10-14: Comparison of blood flow rate and velocity of flow in relation to total cross-section area. The blood flow rate (red curve) is identical through all levels of the circulatory system and is equal to the cardiac output (5 liters/min at rest). The velocity of flow (purple curve) varies throughout the vascular tree and is inversely proportional to the total cross-section area (green curve) of all the vessels at a given level. Note that the velocity of flow is slowest in the capillaries, which have the largest total cross-section area.
Venae
cavae
Fig , p. 291 14

15. O2 CO2 Glucose Plasma = Carrier-mediated transport Interstitial fluid
FIGURE 10-17: Independent exchange of individual solutes down their own concentration gradients across the capillary wall.
Glucose + O CO2 + H2O + ATP
Tissue cell
Fig , p. 293 15

16. Capillary pressure (mm Hg) Transition point Fluid movement
Inward pressure
( pP + PIF)
Outward pressure
(PC + pIF)
FIGURE 10-19: Net filtration and net reabsorption along the vessel length. The inward pressure (πP + PIF) remains constant throughout the length of the capillary whereas the outward pressure (PC + πIF) progressively declines throughout the capillary’s length. In the first half of the vessel, where the declining outward pressure still exceeds the constant inward pressure, progressively diminishing quantities of fluid are filtered out (upward red arrows). In the last half of the vessel, progressively increasing quantities of fluid are reabsorbed (downward blue arrows) as the declining outward pressure falls farther below the constant inward pressure.
Capillary length
Beginning
End
= Ultrafiltration
= Reabsorption
Fig , p. 295 16

17. Pulmonary Systemic arteries vessels 13% 9% Systemic arterioles 2%
Heart 7%
Systemic capillaries 5%
Systemic veins
64%
FIGURE 10-23: Percentage of total blood volume in different parts of the circulatory system.
Fig , p. 299 17

19. PLASMA COLLOID OSMOTIC P=28 SUMMATION OF FORCES
ARTERIAL END OF CAP
FORCES OUTWARD
CAP P 30+NEG IFFP 3 +IFCOP8=41
FORCES INWARD
PLASMA COLLOID OSMOTIC P=28
SUMMATION OF FORCES
OUTWAR 41-INWARD 28=13mmhg 19

20. PLASMA COLLOID OSMOTIC P=28 SUMMATION OF FORCES
VENOU END OF CAP
FORCES OUTWARD
CAP P 10+NEG IFFP 3 +IFCOP8=21
FORCES INWARD
PLASMA COLLOID OSMOTIC P=28
SUMMATION OF FORCES
INWAR 28-OUTWARD 21=7mmhg 20

21. STARLING EQUILIBRIUM FOR CAPILLARY PRESSURE
OUTWAD FORCES
MEAN CAP P=17.3
NEG IFFP=3
IFCOP=8
TOTAL=28.3mmhg
INWARD FORCES
PLASMA COLL OSM PRES=28mmhg
RESULT(OUTWARD28.3-INWARD28=0.3 21

22. LYMPHATIC CIRCULATION
1-LYMPHATIC STRUCTURE
2-FACTORS DETERMINE LYMPHATIC FLOW
A.LYMPHATIC PUMP
B.INTERSTIAL FLUID PRESSURE 22

25. LYMPHATIC FUNCTION CONTROLL INTERSTIALFLUID 1. PROTEIN CONCENTRATION
2.VOLUME
3.PRESSURE 25

27. Lymph flow 1.Interstial fluid pressure A. Elevate capillary pressure B. Increase interstitial fluid colloid osmotic pressure C. Decrease plasma colloid osmotic pressure D. Increase permeability of capillaries

28. 2. Lymph pump and valves 3. External compression A
2. Lymph pump and valves 3.External compression A. Surrounding skeletal muscles B. Movements of parts of the body C. Pulsation of arteries D. Compression of the tissues by objects outside the body

29. 4. Lymphatic capillary pump