Veterinary Professionals - Vet Pro - SPECIAL ANATOMY OF CAMEL TO COPE WITH HOT DESERT CLIMATE

Dr. Riaz Hussain Pas writes "The Camel (Camelus dromedarius) is an important component of the desert ecosystem. It provides transport and subsistence to the rural societies inhabiting arid and semi-arid zones. It is also a source of milk, hair, manure, bones and meat to the people residing in the poorly resourced arid and semi arid zones. Numerous adaptations have allowed the camel to survive the incredibly harsh environment of the desert.
Heat storage within the body of the camel, selective brain cooling, fur, concentrated urine from unique kidneys, respiration mechanisms and hormones, all serve as important characteristics for the camel in terms of thermoregulation.
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During the hot desert day, camels are able to significantly increase their body temperature and store heat during the hot desert day. The purpose of storing heat is to conserve water that would otherwise be lost to evaporation. The conservation of water in the desert is essential for the camel in times when water is scarce. At night when the temperature drops noticeably, the stored heat in the camel dissipates so that the body temperature of the camel returns to a normal level. The advantage of the storing heat on a hot desert day is that the camel does not waste any water on regulating its temperature.
Brain Cooling Mechanism
The brain is one of the most heat sensitive parts of the body. Consequently the camel uses selective brain cooling so that it can keep the brain at a lower temperature during times of heat stress than the rest of the body. If the brain were subjected to the extraordinarily high temperatures that the rest of the body faces then those temperatures would be fatal for the camel. Brain cooling is an essential thermoregulatory adaptation in heat stressed animals. The body temperature greatly increases when running at high speeds for an extended period of time, however this built up heat stress within the body does not affect the most sensitive part, the brain, due to brain cooling. The camel has the ability to withstand intensely high body temperatures without damaging its brain due to this cooling system. The brain cooling system not only provides protection for the brain in extreme temperatures, but it also allows the camel to have a wider range of tolerance for hot conditions. In camels, arterial blood to the tissues of the brain passes over the carotid rete before entering the brain (Fig1). In the long nasal cavity (A), evaporative heat loss occurs which then cools the venous blood that goes by the nasal cavity. This cooled venous blood travels from where the nasal vein connects with the angular vein (B) to the ophthalmic veins (C) which connect to the cavernous sinus The cavernous sinus incorporates the carotid rete; however the arterial blood of the carotid rete does not mix with the cool venous blood of the cavernous sinus. The two are separated by a thin arterial vessel wall which allows for heat exchange. The cool venous blood in the cavernous sinus cools off the arterial blood within the carotid rete. In this way the blood is cooled off before entering the brain and it is due to this process that the temperature of the brain can remain several degrees lower than the rest of the body temperature. Under normal conditions, the cool venous blood, after having passed over the nasal cavity, travels via a general circulation. However, when temperatures increase in the body the nasal and the angular veins become wider while the facial vein is constricted. When this situation occurs the cool venous blood can only go in one direction through the ophthalmic veins to the cavernous sinus which then cools the arterial blood through heat exchange in the carotid rete. This process maximizes the amount of cooling that is possible for the brain when the camel experiences heat stress. Not only can it survive in the desert because of this adaptation, but the camel also has an increased tolerance to higher temperatures.
Fur on the Body
The layer of fur on the camel serves as layer of insulation against the heat. As an effective barrier against the heat, the fur prevents excessive heat gain and consequently helps to conserve water. Camels that lack this important layer of fur, result in higher body temperature and heat stress.
Role of Kidneys
The role of the kidney in the camel becomes essential to the camel in terms of urine concentration. The kidney can produce very concentrated urine when there is a need for water. The ability to concentrate urine can be determined by the loop of Henle and the structure of the renal medulla. The longer the loop of Henle usually indicates the ability to produce more concentrated urine.
Respiratory Mechanism
Water loss can increase quickly in a camel with high temperatures and respiratory frequencies. For this reason, the camel has special respiratory mechanisms. Water loss can be reduced by cooling off the exhaled air in the nasal passages which allows for the recovery of water.
Role of Hormones
Hormones play an important role in the conservation of water during times of high heat and dehydration. The concentration of urine that occurs in the kidneys is also partially the result of hormones.
So Camel has provided with the special anatomical features which enable him to cope with the heat stress, conserve water for long period of time and to survive in the harsh climate of desert.
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