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Protection against high intravascular pressure in giraffe legs.
- Source :
-
American journal of physiology. Regulatory, integrative and comparative physiology [Am J Physiol Regul Integr Comp Physiol] 2013 Nov 01; Vol. 305 (9), pp. R1021-30. Date of Electronic Publication: 2013 Sep 04. - Publication Year :
- 2013
-
Abstract
- The high blood pressure in giraffe leg arteries renders giraffes vulnerable to edema. We investigated in 11 giraffes whether large and small arteries in the legs and the tight fascia protect leg capillaries. Ultrasound imaging of foreleg arteries in anesthetized giraffes and ex vivo examination revealed abrupt thickening of the arterial wall and a reduction of its internal diameter just below the elbow. At and distal to this narrowing, the artery constricted spontaneously and in response to norepinephrine and intravascular pressure recordings revealed a dynamic, viscous pressure drop along the artery. Histology of the isolated median artery confirmed dense sympathetic innervation at the narrowing. Structure and contractility of small arteries from muscular beds in the leg and neck were compared. The arteries from the legs demonstrated an increased media thickness-to-lumen diameter ratio, increased media volume, and increased numbers of smooth muscle cells per segment length and furthermore, they contracted more strongly than arteries from the neck (500 ± 49 vs. 318 ± 43 mmHg; n = 6 legs and neck, respectively). Finally, the transient increase in interstitial fluid pressure following injection of saline was 5.5 ± 1.7 times larger (n = 8) in the leg than in the neck. We conclude that 1) tissue compliance in the legs is low; 2) large arteries of the legs function as resistance arteries; and 3) structural adaptation of small muscle arteries allows them to develop an extraordinary tension. All three findings can contribute to protection of the capillaries in giraffe legs from a high arterial pressure.
- Subjects :
- Adaptation, Physiological
Animals
Brachial Artery diagnostic imaging
Brachial Artery pathology
Capillary Permeability
Edema physiopathology
Hydrostatic Pressure
Male
Tibial Arteries diagnostic imaging
Tibial Arteries pathology
Time Factors
Ultrasonography
Vascular Resistance
Vasoconstriction
Arterial Pressure
Brachial Artery physiopathology
Capillaries physiopathology
Edema prevention & control
Lower Extremity blood supply
Ruminants
Tibial Arteries physiopathology
Subjects
Details
- Language :
- English
- ISSN :
- 1522-1490
- Volume :
- 305
- Issue :
- 9
- Database :
- MEDLINE
- Journal :
- American journal of physiology. Regulatory, integrative and comparative physiology
- Publication Type :
- Academic Journal
- Accession number :
- 24005251
- Full Text :
- https://doi.org/10.1152/ajpregu.00025.2013