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Thursday, November 24, 2011

Dog Feet Have Special Blood Vessels That Protect Them From Cold

Dog Feet Have Special Blood Vessels

That Protect Them From Cold


Woof, it's cold out there! So how come dogs' paws don't freeze up when they pad around on snow and ice - and what keeps dogs from minding the cold?
Japanese scientists say they've discovered why. First of all, they say in a new study published in the journal Veterinary Dermatology, dogs' pads contain lots of fatty tissue - which doesn't freeze as easily as other tissues. And the blood vessels in dogs' feet are arranged in a way that lets them act like living heat exchangers: arteries in the paws are very close to networks of tiny veins (venules), facilitating the transfer of heat from venous to arterial blood.

When a paw is cooled by contact with frozen ground, warmth from the arteries in the paw is transferred to the venules. This helps keep the paw at a tolerable temperature. In addition, it warms the blood before it flows back to the body - thus helping keep the dog's body temperature from falling uncomfortably low.

The so-called "counter-current" heat exchange mechanism sounds like a good one, and it's not unique to canines. Similar systems are seen in other animals, including penguins and foxes, physorg.com reported. The finding suggests that dogs may have evolved in cold environments.
Research has shown that dogs' feet are protected from freezing even in temperatures as low as -35 Celsuis, according to the BBC.

The research, carried out by Dr. Hiroysho Ninomiya and colleagues at Tokyo's Yamazaki Gakuen University, was conducted with the help of an electron microscope and four willing dogs.


Abstract

Dogs are well adapted to cold climates and they can stand, walk and run on snow and ice for long periods of time. In contrast to the body trunk, which has, dense fur, the paws are more exposed to the cold due to the lack of fur insulation. The extremities have a high surface area-to-volume ratio, so they lose heat very easily. We offer anatomical evidence for a heat-conserving structure associated with dog footpad vasculature. Methylmethacrylate vascular corrosion casts for scanning electron microscopy, Indian ink-injected whole-mount and histological specimens were each prepared, in a series of 16 limbs from four adult dogs. Vascular casts and Indian ink studies showed that abundant venules were arranged around the arteries supplying the pad surface and formed a vein–artery–vein triad, with the peri-arterial venous network intimately related to the arteries. In addition, numerous arteriovenous anastomoses and well-developed venous plexuses were found throughout the dermal vasculature. The triad forms a counter-current heat exchanger. When the footpad is exposed to a cold environment, the counter-current heat exchanger serves to prevent heat loss by recirculating heat back to the body core. Furthermore, the arteriovenous anastomoses shift blood flow, draining blood to the skin surface, and the venous plexuses retain warm blood in the pad surface. Hence, the appropriate temperature for the footpad can be maintained in cold environments.

 

Résumé

Les chiens sont bien adaptés aux climats froids et ils peuvent rester, marcher et courir sur la glace pendant de longues périodes. Contrairement au tronc, muni d’une fourrure dense et épaisse, les pieds sont plus exposés au froid à cause de l’absence de fourrure isolante. Les extrémités ont un rapport surface/volume élevé et perdent ainsi de la chaleur très facilement. Nous offrons une preuve anatomique des structures de conservation de la chaleur liée à la vascularisation des coussinets plantaires. Des préparations vasculaires au méthylméthacrylate pour microscopie électronique, des injections à l’encre Indian et des préparations histologiques ont été réalisées sur une série de 16 membres de 4 chiens adultes. Les moulages vasculaires et les colorations à l’encre Indian, ont montré que de nombreuses veinules étaient organisées autour des artères irrigant la surface du coussinet et formaient une triade veine-artère-veine, le réseau veineux peri-artériel étant intimement relié aux artères. En outre, de nombreuses anastomoses artério-veineuses (AVAs) et des plexus veineux bien développés ont été trouvés tout au long de la vascularisation dermique. La triade forme un échangeur de chaleur à contre-courant. Lorsque le coussinet plantaire est exposéà un environnement froid, l’échangeur à contre-courant permet de prévenir la perte de chaleur par un retour du courant circulatoire chaud vers le centre du corps. De plus, les AVAs réorientent le flux sanguin, drainent le sang à la surface cutanée et les plexus veineux retiennent le sang tiède à la surface du coussinet. Ainsi, une température appropriée pour le coussinet plantaire peut être maintenue dans les environnements froids.

Functional anatomy of the footpad vasculature of dogs: scanning electron microscopy of vascular corrosion casts

  1. Hiroyoshi Ninomiya,
  2. Emi Akiyama,
  3. Kanae Simazaki,
  4. Atsuko Oguri,
  5. Momoko Jitsumoto,
  6. Takaaki Fukuyama
Article first published online: 28 MAR 2011



Friday, November 11, 2011

Why God Sends Rain To Mexico

Why God Sends Rain To Mexico 
But Not The Mideast









Mideast






Any Questions?

Thursday, November 10, 2011

Decision... Decision

A man wakes up in the hospital bandaged from head to foot.
The doctor comes in and says, "Ah, I see you've regained consciousness. Now you probably won't remember, but you were in a huge pile-up on the freeway.

You're going to be OK, you'll walk again and everything, but your penis was severed in the accident and we couldn't find it."
 
The man groans, but the doctor goes on, "You have $9000.00 in insurance compensation coming and we now have the technology to build a new penis.

They work great but they don't come cheap. It's roughly $1000.00 an inch." 

The man perks up.
"So," the doctor says, "You must decide how many inches you want. But I understand that you have been married for over thirty years and this is something you should discuss with your wife.
 
If you had a five incher before and get a nine incher now she might be a bit put out. If you had a nine incher before and you decide to only invest in a five incher now, she might be disappointed.
 
It's important that she plays a role in helping you make a decision."
The man agrees to talk it over with his wife.

The doctor comes back the next day, "So, have you spoken with your wife?"  

"Yes I have," says the man.

 "And has she helped you make a decision?"
"Yes she has." says the man.
 "What is your decision?" asks the doctor.


 
"We're getting granite countertops."




Tuesday, November 1, 2011

Learn French with Music

Music
Learn French

*
Charles Aznavour   -  Hier encore.
Charles Aznavour  -   Mourir D'aimer
Christophe  -   Aline

Dalida  -   Bambino

Dalida   -  Bonsoir Mon Amour
Dalida  -   Come prima
Dalida   -  Garde-moi La Darnière Danse
Dalida   -  Histoire D'un Amour
Dalida   -  La Danse de Zorba
Dalida  -   La Mer
Dalida  -  La vie en rose
Dalida   -  Les Enfants du Piree
Dalida  -   Les Nuits d'Espagne
Dalida  -   Mourir sur Scène
Dalida   -  Paroles Paroles
Gilbert Becaud   -  Et Maintenant
Marie Laforêt  -   Les Vendanges de L'amour
Marie Laforet  -   Mon amour mon ami
Nana Mouskouri   -  Je chante avec toi Liberté
Celine Dion   -  Mon cœur survivra pour toi

http://www.youtube.com/user/rudylopez2000

Learn French with - Alain Barrière  
Learn French with - Charles Aznavour 
Learn French with - Christophe 
Learn French with - Claude François 
Learn French with - Dalida 
Learn French with - Gilbert Becaud 
Learn French with - Hervé Vilard 
Learn French with - Joe Dassin 
Learn French with - Marie Laforêt  
Learn French with - Mireille Mathieu 
Learn French with - Nana Mouskouri  
Learn French with - Patricia Carli 
Learn French with - Petula Clark  
Learn French with - Richard Anthony 
Learn French with - Salvatore Adamo 
Learn French with - Sheila