The gastrointestinal circulation / Peter R. Kvietys.

Format:

Book

Author/Creator:

Kvietys, Peter R.

Series:

Colloquium series on integrated systems physiology ; #5.

Integrated systems physiology : from molecule to function to disease ; bk. #5

Language:

English

Subjects (All):

Gastrointestinal system--Blood-vessels.

Gastrointestinal system.

Digestive organs--Blood-vessels.

Digestive organs.

Physical Description:

1 online resource (140 p.)

Place of Publication:

[San Rafael, Calif.?] : Morgan & Claypool Life Sciences, 2010.

Language Note:

English

Summary:

The microcirculation of the gastrointestinal tract is under the control of both myogenic and metabolic regulatory systems. The myogenic mechanism contributes to basal vascular tone and the regulation of transmural pressure, while the metabolic mechanism is responsible for maintaining an appropriate balance between O2 demand and O2 delivery. In the postprandial state, hydrolytic products of food digestion elicit a hyperemia, which serves to meet the increased O2 demand of nutrient assimilation. Metabolically linked factors (e.g., tissue pO2, adenosine) are primarily responsible for this functional hyperemia. The fenestrated capillaries of the gastrointestinal mucosa are relatively permeable to small hydrolytic products of food digestion (e.g., glucose), yet restrict the transcapillary movement of larger molecules (e.g., albumin). This allows for the absorption of hydrolytic products of food digestion without compromising the oncotic pressure gradient governing transcapillary fluid movement and edema formation. The gastrointestinal microcirculation is also an important component of the mucosal defense system whose function is to prevent (and rapidly repair) inadvertent epithelial injury by potentially noxious constituents of chyme. Two pathological conditions in which the gastrointestinal circulation plays an important role are ischemia/reperfusion and chronic portal hypertension. Ischemia/reperfusion results in mucosal edema and disruption of the epithelium due, in part, to an inflammatory response (e.g., increase in capillary permeability to macromolecules and neutrophil infiltration). Chronic portal hypertension results in an increase in gastrointestinal blood flow due to an imbalance in vasodilator and vasoconstrictor influences on the microcirculation.

Contents:

1. Introduction

2. Anatomy

Extramural blood and lymphatic vessels

Intramural blood and lymphatic vessels

3. Regulation of vascular tone and oxygenation

Basal hemodynamics and oxygenation

Intrinsic vasoregulation: myogenic and metabolic

Myogenic

Metabolic

Relative impact of myogenic and metabolic mechanisms

Reactive hyperemia

Venous pressure elevation

Arterial pressure reduction

Mediators of metabolic vasoregulation

Tissue pO2

Adenosine

Nitric oxide

Mediators of myogenic vasoregulation

Shear stress modulation of metabolic and myogenic regulatory systems

4. Extrinsic vasoregulation: neural and humoral

Neural

Postganglionic sympathetic

Sensory C fibers

Enteric nerves

Circulating vasoactive substances

5. Postprandial hyperemia

General characteristics

Localization of the postprandial hyperemia

Constituents of chyme responsible for the postprandial hyperemia

Mechanisms involved in the postprandial hyperemia

Extrinsic nerves

Enteric neural reflexes

Circulating hormones

Tissue metabolic activity

6. Transcapillary solute exchange

Ultrastructural pathways

Endothelial cell membrane

Fenestrae

Pinocytotic vesicles

Interendothelial cell junctions

Glycocalyx

Basement membrane

Physiological (functional) pathways

Small solutes

Macromolecules

Factors influencing vascular permeability

Ultrastructural correlates for the functional pathways

7. Transcapillary fluid exchange

Net transcapillary fluid movement ( Jv,c)

Capillary filtration coefficient (Kf,c)

Capillary pressure (Pc)

Interstitial fluid pressure (Pt)

Osmotic reflection coefficient (Od)

Transcapillary oncotic pressure gradient ([pi]c-[pi]t)

8. Interaction of capillary and interstitial forces

Increased venous pressure

Decreased arterial pressure

Transepithelial fluid absorption

Glucose and/or electrolyte-coupled fluid absorption

Oleic acid-coupled fluid absorption

Colonic fluid absorption

Transepithelial fluid secretion

9. Gastrointestinal circulation and mucosal defense

Gastrointestinal acid load

Intestinal lipid load

Gastrointestinal restitution

10. Gastrointestinal circulation and mucosal pathology I: Ischemia/reperfusion

Moderate reductions in blood flow: dysfunction

Severe reductions in blood flow: injury

Ischemia-induced injury

I/R-induced injury

I/R-induced inflammation

Luminal factors may aggravate mucosal injury during I/R

Ischemic tolerance and restitution

11. Gastrointestinal circulation and mucosal pathology II: Chronic portal hypertension

The gastrointestinal circulation in chronic portal hypertension (PH)

Collateral vessels: portosystemic shunting

Gastrointestinal hyperemia

Transcapillary fluid exchange

Luminal factors may aggravate mucosal injury during portal hypertension

12. Summary and conclusions

References

Author biography.

Notes:

Part of: Colloquium digital library of life sciences.

Series from website.

Title from PDF t.p. (viewed on March 15, 2010).

Includes bibliographical references.

Cited in:

Google scholar

Google book search

ISBN:

1-61504-118-4

OCLC:

698135172