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Function of a sphincter‐like structure in the median artery of the giraffe foreleg
Author(s) -
Hoerlyck Arne,
Petersen Karin Kastberg,
Sloth Erik,
Baandrup Ulrik,
Bertelsen Mads,
Broendum Emil,
Candy Geoffrey,
Groendahl Carsten,
Hasenkam Michael,
Secher Niels,
Wang Tobias,
Oestergaard Kristine,
Aalkjaer Christian
Publication year - 2011
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.25.1_supplement.1045.9
Subject(s) - medicine , anatomy
An abrupt increase of wall thickness and reduction of the lumen distal to the knee is seen in the tibial artery of the giraffe. Here we test whether this is seen in the forelegs and provides a vascular resistance. Pressure catheters (zeroed at heart level) were placed ca. 4–5 cm upstream and 140 cm downstream of the sphincter in the foreleg of 5 male giraffes ( Giraffa camleopardalis) under chloralose anesthesia. Lumen narrowing and thickening of the wall were visualized with ultrasound. Spontaneous variability in lumen diameters distal to and at the sphincter, was seen. Sometimes only the sphincter was constricted, sometimes the sphincter and the distal vessel were constricted, while sometimes no constriction was apparent. The pressure difference along the artery varied between 0 and 125 mmHg. Intraarterial injection of 100 μg norepinephrine induced constriction of the sphincter and the distal vessel and an increase in the pressure difference between the catheters. The abrupt narrowing of the median artery of the giraffe is functionally a sphincter and the artery provides a viscous resistance which potentially constitute a protective mechanism against the high transmural pressure in the lower leg.