The Structure and Function of Giraffe Jugular Vein Valves

  title={The Structure and Function of Giraffe Jugular Vein Valves},
  author={Graham Mitchell and Sybrand J. van Sittert and John D. Skinner},
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 distances of 396 valves (192 left, 204 right) were measured in 60 veins from 25 adult (11 males and 14 females) and five foetal giraffes. The… 
Neck length and mean arterial pressure in the sauropod dinosaurs
It is demonstrated that the siphon principle is able to explain how blood was able to adequately perfuse the sauropod brain, and maximum neck length in the fossil record may therefore be due to the siphons height limit.
An allometric analysis of the giraffe cardiovascular system.
  • G. Mitchell, J. Skinner
  • Medicine, Biology
    Comparative biochemistry and physiology. Part A, Molecular & integrative physiology
  • 2009
Giraffe: Biology, Behaviour and Conservation
The giraffe's environment, social behaviour and populations, pregnancy, growth, reproduction and aging, and status and conservation of giraffe races are studied.
“ The Mammal with Heart ” by Hannah Gaitan


Venous Valves in the Giraffe, Okapi, Camel and Ostrich.
Experiments have shown that these valves are efficient in preventing backflow of blood into the tributaries when a sudden rise of pressure occurs in the main vein, unless the pressure in both is very low to start with.
The Cerebral Blood Supply in the Giraffidae
The shunt mechanism would appear to be an adaptation to the presence of the excessively long neck in the Giraffe, and the Okapi was a defective specimen.
It is concluded that in the head-down position blood flow to the head is relatively uncontrolled but when theHead is raised, intense extracranial vasoconstriction occurs which directs carotid blood via the occipito-vertebral anastomosis to the brain, thus preventing ‘fainting’.
The internal jugular vein valve may have a significant role in the prevention of venous reflux: evidence from live and cadaveric human subjects
The internal jugular vein valve (IJVV) is the only valve between the heart and the brain and plays a role in the prevention of cephalad flow of venous blood, so increase in intrapleural pressure could result in raised intracranial pressure.
Gravitational haemodynamics and oedema prevention in the giraffe
Investigating adaptive mechanisms to orthostatic pressure changes in giraffes revealed that arterial pressure near the giraffe heart is about twice that in humans, to provide more normal blood pressure and per-fusion to the brain.
Circulation of the Giraffe
The arterial blood pressure is high by human standards and adequate to maintain cerebral perfusion without other means of support and suggests a relatively lax vascular bed with considerable reserve distensibility.
Cerebral perfusion pressure in giraffe: modelling the effects of head-raising and -lowering.
The Role of the Neck in the Movements of the Giraffe
The role of the neck in the movement of the giraffe was studied by examining motion picture sequences of wild giraffe. Unlike in the horse, the forequarters in the giraffe are stronger than the
Giraffe Thermoregulation: a review
The anatomy of giraffe skin is analysed and it is shown that it contains many active sweat glands, and that the size of these glands is significantly greater under patches than it is elsewhere, supporting the idea that patches are thermal windows.
Rete mirabile of goat: its flow-damping effect on cerebral circulation.
Observations suggest that the carotid rete may have a flow-damping effect by maintaining resistance to blood flow when a change in the caliber of brain vessels occurs and that the response of the vehicle to the substances tested is negligible.