page_title: Dog anatomy
section_title: Physical characteristics
hierarchical_section_title: Dog anatomy / Physical characteristics
caption_attribution_description: dog knee
context_page_description: Dog anatomy comprises the anatomical studies of the visible parts of the body of a canine. Details of structures vary tremendously from breed to breed, more than in any other animal species, wild or domesticated, as dogs are highly variable in height and weight. The smallest known adult dog was a Yorkshire Terrier that stood only 6.3 cm at the shoulder, 9.5 cm in length along the head and body, and weighed only 113 grams. The largest known adult dog was an English Mastiff which weighed 155.6 kg and was 250 cm from the snout to the tail. The tallest known adult dog is a Great Dane that stands 106.7 cm at the shoulder.
context_section_description: Like most predatory mammals, the dog has powerful muscles, a cardiovascular system that supports both sprinting and endurance and teeth for catching, holding, and tearing.
  The dog's muscles provides the ability to jump and leap. Their legs can propel them forward rapidly, leaping as necessary to chase and overcome prey. They have small, tight feet, walking on their toes (thus having a digitigrade stance and locomotion). Their rear legs are fairly rigid and sturdy. The front legs are loose and flexible with only muscle attaching them to the torso.
  The dog's muzzle size will vary with the breed. Dogs with medium muzzles, such as the German Shepherd Dog, are called mesocephalic and dogs with a pushed in muzzle, such as the Pug, are called brachycephalic. Today's toy breeds have skeletons that mature in only a few months, while giant breeds, such as the Mastiffs, take 16 to 18  months for the skeleton to mature. Dwarfism has affected the proportions of some breeds' skeletons, as in the Basset Hound.
  All dogs (and all living Canidae) have a ligament connecting the spinous process of their first thoracic (or chest) vertebra to the back of the axis bone (second cervical or neck bone), which supports the weight of the head without active muscle exertion, thus saving energy. This ligament is analogous in function (but different in exact structural detail) to the nuchal ligament found in ungulates. This ligament allows dogs to carry their heads while running long distances, such as while following scent trails with their nose to the ground, without expending much energy.
  Dogs have disconnected shoulder bones (lacking the collar bone of the human skeleton) that allow a greater stride length for running and leaping. They walk on four toes, front and back, and have vestigial dewclaws on their front legs and on their rear legs. When a dog has extra dewclaws in addition to the usual one in the rear, the dog is said to be "double dewclawed."
caption: Dog knee
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