A model for time-dependent flow in (giraffe jugular) veins: uniform tube properties
Computations are reported for a one-dimensional model of time-dependent flow in collapsible tubes representing long mammalian veins. The tubes are taken to have uniform intrinsic properties and we concentrate on the effect of longitudinal gravity. The main application is to the jugular vein of the upright giraffe, with given inflow rate from the head, a […]
Diameter of coronary arteries in 36 species of mammalian from mouse to giraffe
Systematic quantitative investigations were performed in the coronary arteries of 102 hearts of 36 mammal species with an overall more than tenthousandfold difference of their heart weight. After postmortem coronary angiography with a filling pressure of 100 mm Hg x-rays were taken, and the widest diameters of the coronary artery stems were determined. We found […]
How giraffes prevent oedema
An upright giraffe, by analogy with humans, ought to suffer massive oedema in its feet; moreover, when it lowers its head to drink, the blood should rush down into it and be unable to flow up again. New pressure measurements reported on page 59 of this issue by Hargens et al. Show why neither of […]
The structural organization of the carotid arterial system of the giraffe (Giraffa camelopardalis)
Carotid arteries in the giraffe were removed and their structural organization studied with light microscopy. It has been shown that the carotid artery has a largely muscular structure in the adult except for the carotid baroreceptor area located at the carotid‐occipital junction. The fetus carotid has an elastic structure in its caudal portion and a […]
Gravitational haemodynamics and oedema prevention in the giraffe
Because it is so tall, the giraffe, Giraffa camelopardalis, provides an important animal model for investigating adaptive mechanisms to orthostatic (gravitational) pressure changes. Previous physiological studies of the giraffe have concentrated on arterial blood pressures in the heart and neck. Briefly, these investigations revealed that arterial pressure near the giraffe heart is about twice that […]
Blood pressure and flow rate in the giraffe jugular vein
Experimental measurements in the jugular veins of upright giraffes have shown that the internal pressure is somewhat above atmospheric and increases with height above the heart. A simple model of steady viscous flow in an inverted U-tube shows that these observations are inconsistent with a model in which the blood vessels in the head and […]
Is the Flow in the Giraffe’s Jugular Vein a “Free” fall?
There is a controversy as to whether or not the heart works against gravity in the arteries to the head in the upright position. One view is that the gravitational effects in the neck arteries are counterbalanced by the gravitational effects in the veins of the neck and the heart does not do extra pressure […]
Development of the Giraffe Horn and Its Blood Supply
The giraffe horn is an unusual cranial exostosis that lacks clear delineation and categorization as either horn or antler. The distinction between the two is made by contrasting their methods of development and basic composition. This process of development has not been detailed in the giraffe, a factor contributing to the difficulty in distinguishing the […]
Carotid Haemodynamics in the Giraffe
In a research letter to this journal on the physiology of the giraffe, McCalden et al. suggested that cranial blood flow in the giraffe is regulated by an autoregulatory response of the cranial vasculature. Their conclusion was based on two points: 1) that carotid flow remains constant over a wide range of carotid pressures, and […]