Dog anatomy

Extrinsic muscles of the thoracic limb and related structures:[4] Descending superficial pectoral: originates on the first sternebrae and inserts on the greater tubercle of the humerus.

Intrinsic muscles of the thoracic limb: Deltoideus: originates on the acromial process of the scapula and inserts on the deltoid tuberosity.

Medial muscles of the scapula and shoulder: Subscapularis: originates on the subscapular fossa and inserts on the greater tubercle of the humerus.

Cranial muscles of the arm: Biceps brachia: originates on the supraglenoid tubercle and inserts on the ulnar and radial tuberosities.

Cranial and lateral muscles of antebrachium: Extensor carpi radial: originates on the supracondylar crest and inserts on the metacarpals.

Extensor carpi ulnar: originates on the lateral epicondyle of the humerus and inserts on the metacarpal 5 and the accessory carpal bone.

Flexor carpi radial: originates on the medial epicondyle of the humerus and inserts on the palmar side of metacarpals 2 and 3.

Superficial digital flexor: originates on the medial epicondyle of the humerus and inserts on the palmar surface of the middle phalanges.

Deep digital flexor: originates on the medial epicondyle of the humerus and inserts on the palmar surface of the distal phalanx.

Caudal hip muscles: Internal obturator: originates on the pelvic symphysis and inserts on the trochanteric fossa of the femur.

Cranial muscles of the thigh: Quadriceps femoris: originates on the femur and the ilium and inserts on the tibial tuberosity.

Craniolateral muscles of the leg: Cranial tibial: originates on tibia and inserts on the plantar surfaces of metatarsals 1 and 2.

Peroneus longus: originates on both the tibia and fibula and inserts on the 4th tarsal bone and the plantar aspect of the metatarsals.

Superficial digital flexor: originates on the lateral supracondylar tuberosity of the femur and inserts on the tuber calcanei and bases of the middle phalanges.

"[6] The domestic dog compared to the wolf shows the greatest variation in the size and shape of the skull (Evans 1979) that ranges from 7 to 28 cm in length (McGreevy 2004).

Puppies are born with short snouts, with the longer skull of dolichocephalic dogs emerging in later development (Coppinger 1995).

As dogs have few sweat glands in their skin, the respiratory system also plays an important role in body thermoregulation.

They have a spongy appearance due to the presence of a system of delicate branches of the bronchioles in each lung, ending in closed, thin-walled chambers (the points of gas exchange) called alveoli.

The dog's face can have a shortened skull, facial and nasal bones, stenotic nares, a hypoplastic trachea, and everted laryngeal saccules.

[11][12] The organs that make up the canine digestive system are:[13] Sixty percent of the dog's body mass falls on the front legs.

[15] 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.

Dog coats vary in texture, color, and markings, and a specialized vocabulary has evolved to describe each characteristic.

This white region (the neutral point) occurs around 480 nm, the part of the spectrum that appears blue-green to humans.

[36] A test has estimated poodles' visual acuity to have a Snellen rating of 20/75, a relatively low score compared to humans' vision.

[28] As crepuscular hunters, dogs often rely on their vision in low light situations: They have very large pupils, a high density of rods in the fovea, an increased flicker rate, and a tapetum lucidum.

Short-nosed breeds, on the other hand, have an "area centralis", a central patch with up to three times the density of nerve endings as the visual streak, giving them detailed sight much more like a human's.

[28] Dogs also have a greater divergence of the eye axis than humans, enabling them to rotate their pupils farther in any direction.

Vibrissae are more rigid, embedded much more deeply in the skin than other hairs, and have a greater number of receptor cells at their base.

[44] A study found that dogs may prefer, when they are off the leash and the Earth's magnetic field is calm, to urinate and defecate with their bodies aligned on a north-south axis.

Panting moves cooling air over the moist surfaces of the tongue and lungs, transferring heat to the atmosphere.