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8/10/2019 Limphatic System1233441212

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Structure of the Microcirculation

Capillary System Metarterioles

Precapillary sphincter Large preferential channels Small true capillaries


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Venule

Arteriole

PreferentialChannel

Metarteriole

PrecapillarySphincter True Arterioles


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BasementMembrane(Collagen Type I)

VesicularChannel?

Endothelial Cell

IntercellularCleft

PlasmalemmalVesicles

(1 Endothelial Cell Thick)


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Transport Mechanisms

Diffusion Intercellular Clefts

Plasmalemmal Vesicles Tight Junctions (brain) Open Junctions (liver)

Fenestra (kidney)


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Capillary Vasomotion

Intermittent flow regulated by precapillarysphincters.

Controlled by O2 concentration.


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Diffusion through CapillaryMembrane

Lipid soluable through endothelial cellmembrane.

Water soluable through intercellularpores

Size Dependent


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Diffusion through Capillary Membrane

This figure illustrates that the permeability of substances throughcapillary membrane decreases roughly with the logarithm of size.

0

0.2

0.4

0.6

0.8

1

1.2

10 100 1000 10000 100000

Molecular Weight (Daltons)

P e r m e a

b i l i t y ( R e l a t

i v e

t o W a t e r

) Water

Albumin


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Limphatic system

End collecting vessels of system aresingle walled endothelial cells

lacking tight junctions

possess fine filaments which anchor them toconnective tissue


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Limphatic system

with contractions, these filaments can pull onendothelial cells, allowing protein, largeparticles or cells to enter lymph system

Contain one-way valves, like the veins Collecting vessels drain into larger vessels, whichultimately enter the right and left subclavian veins

Recover and return about 15% of blood volume lostthrough capillary filtration

In a single day, this is equivalent to the total plasmavolume

returns proteins to the blood In a single day, this is represents about to the

circulating plasma proteins

Disease: Lymphodema Severe edema in affected area


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Lymphatic systemLymph capillaries drain excess fluid from

interstitial spacesNo true lymphatic vessels found in

superficial portions of skin, CNS,endomysium of muscle, & bones

Thoracic duct drains lower body & leftside of head, left arm, part of chest

Right lymph duct drains right side of head,neck, right arm and part of chest


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CNS-modified lymphatic

functionNo true lymphatic vessels in CNSPerivascular spaces contain CSF &

communicate with subarachnoid spacePlasma filtrate & escaped substances in

perivascular spaces returned to thevascular system in the CSF via thearachnoid villi which empties into duralvenous sinuses

Acts a functional lymphatic system in CNS


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Formation of LymphExcess plasma filtrate-resembles ISF

from tissue it drains[Protein] 3-5 gm/dl in thoracic duct

liver 6 gm/dlintestines 3-4 gm/dlmost tissues ISF 2 gm/dl

2/3 of all lymph from liver & intestines Any factor that filtration and/or

reabsorption will lymph formation


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Rate of Lymph Formation/Flow

Thoracic duct- 100 ml/hr.Right lymph duct- 20 ml/hr.

Total lymph flow- 120 ml/hr (2.9 L/day)Every day a volume of lymph roughly equal

to your entire plasma volume is filtered


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Function of Lymphatics

Return lost protein to the vascular systemDrain excess plasma filtrate from ISF space

Carry absorbed substances/nutrients(e.g. fat-chlyomicrons) from GI tractFilter lymph (defense function) at lymph

nodeslymph nodes-meshwork of sinuses lined withtissue macrophages (phagocytosis)

limphatic system1233441212

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