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 […]
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 […]
The structure and function of giraffe jugular vein valves
When a giraffe (Giraffa camelopardalis) lowers its head to drink, blood could enter the jugular vein from the inferior vena cava or regurgitate from the jugular veins into the cranial veins. We investigated the anatomy of jugular valves in giraffes to establish if they could prevent either of these regurgitations. Jugular vein length and intervalve […]
Haemodynamics of the jugular vein in the giraffe
Controversy cotinues over the haemodynamics of the circulation to and from the head of the giraffe. The recent study by Hargens et al. provides new information explaining the absence of oedema in the legs of the ambulant giraffe. But in sedated, standing giraffes the pressure gradient down the jugular vein is about one-tenth of, and […]
Variations in the thickness and composition of the skin of the giraffe
This study examined the skin of two 1- to 2-year-old male giraffes and one adult male, determining skin thickness and histological structure with reference to it functioning as a component of the features required for the maintenance of blood pressure, dermal armor, or thermoregulation. It has been argued that a tight skin surrounding the extremities […]
Giraffes, Rats, and Man — What is the importance of the ‘structural factor’ in normo- and hypertensive states?
The normal structural adaptation of heart and vessels to regional changes in load or/and tissue demands is surveyed with respect to its importance for cardiovascular function in normotension as well as in physiological (giraffes) and pathophysiological (e.g. human and rat primary hypertension) variants of high pressure states. At the local level it implies an entirely […]