Dog anatomy comprises the anatomical study of the visible parts of the body of a domestic dog. Details of structures vary tremendously from breed to breed, more than in any other animal species, wild or domesticated,Scientists fetch useful information from dog genome publications, Cold Spring Harbor Laboratory, 7 December 2005; published online in Bio-Medicine quote: "Phenotypic variation among dog breeds, whether it be in size, shape, or behavior, is greater than for any other animal" as dogs are highly variable in height and weight. The smallest known adult dog was a Yorkshire Terrier that stood only at the shoulder, in length along the head and body, and weighed only . The heaviest dog was an English Mastiff named Zorba, which weighed . The tallest known adult dog is a Great Dane that stands at the shoulder.
Anatomy
Muscles The following table lists the limb muscles of the dog.
Muscle Location Origin Insertion Nerve Action Descending superficial pectoral chest and shoulders first sternebra greater tubercle of the humerus cranial pectoral nerves adducts the forelimb Transverse superficial pectoral chest and shoulders second and third sternebrae greater tubercle of the humerus cranial pectoral nerves adducts the forelimb Deep pectoral chest and shoulder ventral sternum lesser tubercle of the humerus caudal pectoral nerves extends the shoulder joint Sternocephalicus chest and neck sternum temporal bone accessory nerve turns the head and neck Sternohyoideus anterior chest Sternum Basihyoid bone ventral branches of the cervical spinal nerves moves the tongue caudally Sternothyoideus neck first costal cartilage thyroid cartilage ventral branches of the cervical spinal nerves moves the tongue caudally Omotransversarius anterior back and neck spine of the scapula wing of the atlas accessory nerve advances the forelimb and flexes the neck Trapezius anterior back midline supraspinous ligament spine of the scapula accessory nerve elevates and abducts the forelimb Rhomboideus back of the neck to the shoulders nuchal crest of the occipital bone scapula ventral branches of the spinal nerves elevates the forelimb Latissimus dorsi back and shoulder thoracolumbar fascia teres major tuberosity of the humerus thoracodorsal nerve flexes the shoulder joint Serratus ventralis back of the neck to shoulders transverse processes of the C3 to C7 vertebrae scapula ventral branches of the cervical spinal nerves support the trunk and depress the scapula Deltoideus shoulder acromial process of the scapula deltoid tuberosity axillary nerve flexes the shoulder Infraspinatus shoulder infraspinatus fossa greater tubercle of the humerus suprascapular nerve extends and flexes the shoulder joint Teres minor shoulder infra glenoid tubercle of the scapula teres minor tuberosity of the humerus axillary nerve flexes the shoulder and rotates the forelimb laterally Supraspinatus shoulder supraspinous fossa of the scapula greater tubercle of the humerus suprascapular nerve extends and stabilizes the shoulder joint Subscapularis shoulder subscapular fossa greater tubercle of the humerus subscapular nerve rotates the forelimb medially Teres major shoulder scapula teres major tuberosity of the humerus axillary nerve rotates the forelimb medially Coracobrachialis shoulder coracoid process of the scapula crest of the lesser tubercle of the humerus musculocutaneous nerve adducts, extends, and stabilizes the shoulder Tensor fasciae antebrachium upper forelimb fascia covering the latissimus dorsi olecranon radial nerve extends the elbow Triceps brachii upper forelimb caudal border of the scapula olecranon tuber radial nerve extends the elbow and flexes the shoulder Anconeus lower forelimb humerus proximal end of the ulna radial nerve extends the elbow Biceps brachii upper forelimb supraglenoid tubercle ulnar and radial tuberosities musculocutaneous nerve flexes the elbow and extends the shoulder Brachialis upper forelimb lateral surface of the humerus ulnar and radial tuberosities musculocutaneous nerve flexes the elbow Extensor carpi radialis lower forelimb supracondylar crest metacarpals radial nerve extends the carpus Common digital extensor lower forelimb, carpus lateral epicondyle of the humerus distal phalanges radial nerve extends the carpus and digits 3, 4, and 5 Extensor carpi ulnar lower forelimb lateral epicondyle of the humerus metacarpal 5 and the accessory carpal bone radial nerve abducts and extends the carpal joint supinator forelimb lateral epicondyle of the humerus radius radial nerve rotates the lower forelimb laterally Abductor pollicis longus lower forelimb ulna metacarpal 1 radial nerve abducts digit 1 and extends the carpal joint pronator teres lower forelimb medial epicondyle of the humerus medial border of the radius median nerve rotate lower forelimb medially and flex the elbow Flexor carpi radialis lower forelimb medial epicondyle of the humerus palmar side of metacarpals 2 and 3 median nerve flexes the carpus Superficial digital flexor lower forelimb medial epicondyle of the humerus palmar surface of the middle phalanges median nerve flexes the carpus and the metacarpophalangeal and proximal interphalangeal joints Flexor carpi ulnar lower forelimb olecranon accessory carpal bone ulnar nerve flexes the carpus Deep digital flexor lower forelimb medial epicondyle of the humerus palmar surface of the distal phalanges median nerve flexes the carpus, metacarpophalangeal joints, and interphalangeal joints Pronator quadratus lower forelimb radius and ulna ? median nerve pronates the paw Biceps femoris upper hindlimb ischiatic tuberosity patellar ligament sciatic nerve extends the hip, stifle, and hock Semitendinosus hindlimb ischiatic tuberosity tibia sciatic nerve extends the hip and hock, flexes the stifle Semimembranosus hindlimb ischiatic tuberosity femur and tibia sciatic nerve extends the hip and stifle Sartorius hindlimb ilium patella and tibia femoral nerve flexes the hip and both flexes and extends the stifle Gracilis hindlimb pelvic symphysis cranial border of the tibia obturator nerve adducts the hindlimb, flexes the stifle and extends the hip and hock Pectineus upper hindlimb iliopubic eminence caudal femur obturator nerve adducts the hindlimb Adductor upper hindlimb pelvic symphysis lateral femur obturator nerve adducts the hindlimb and extends the hip Tensor fasciae latae upper hindlimb tuber coxae of the ilium lateral femoral fascia cranial gluteal nerve flexes the hip and extends the stifle Superficial gluteal hips lateral border of the sacrum third trochanter caudal gluteal nerve extends the hip and abducts the hindlimb Middle gluteal hips ilium greater trochanter cranial gluteal nerve abducts the hip and rotates the hindlimb medially Deep gluteal hips ischiatic spine greater trochanter cranial gluteal nerve extends the hip and rotates the hindlimb medially Internal obturator hips pelvic symphysis trochanteric fossa of the femur sciatic nerve rotates the hindlimb laterally Gamelli hips lateral surface of the ischium trochanteric fossa sciatic nerve rotates the hindlimb laterally Quadratus femoris hips ischium intertrochanteric crest ? extends the hip and rotate the hindlimb laterally External obturator hips pubis and ischium condyloid process of mandible obturator nerve rotates the hindlimb laterally Quadriceps femoris upper hindlimb femur and ilium tibial tuberosity femoral nerve extends the stifle and flexes the hip Ilipsoas upper hindlimb ilium lesser trochanter femoral nerve flexes the hip Cranial tibial lower hindlimb tibia plantar surfaces of metatarsals 1 and 2 peroneal nerve flexes the tarsus and rotates the paw laterally Popliteus lower hindlimb lateral condyle of the femur tibia tibial nerve rotates the leg medially Long digital extensor lower hindlimb extensor fossa of the femur extensor processes of the distal phalanges peroneal nerve extends the toes and flexes the tarsus Peroneus longus lower hindlimb tibia and fibula fourth tarsal bone and the plantar aspect of the metatarsals peroneal nerve flexes the tarsus and rotates the paw medially Gastrocnemius lower hindlimb supracondylar tuberosities of the femur tuber calcanei tibial nerve extends the tarsus and flexes the stifle Superficial digital flexor lower hindlimb lateral supracondylar tuberosity of the femur tuber calcanei and bases of the middle phalanges tibial nerve extends the tarsus and flexes the stifle Deep digital flexor lower hindlimb Fibula plantar surface of the distal phalanges tibial nerve extends the tarsus and flexes the toes
Skeleton
The vertebrae have muscles attached to the pedicles, the laminae, the spinous, transverse, and articular processes, the vertebral and intervertebral foramina, the atlas (C1), axis (C2), dens, and ventral lamina (C6).
Skull In 1986, a study of skull morphology found that the domestic dog is morphologically distinct from all other canids except the wolf-like canids. The difference in size and proportion between some breeds are as great as those between any wild genera, but all dogs are clearly members of the same species. In 2010, a study of dog skull shape compared to extant carnivorans proposed that "The greatest shape distances between dog breeds clearly surpass the maximum divergence between species in the Carnivora. Moreover, domestic dogs occupy a range of novel shapes outside the domain of wild carnivorans."
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). Wolves are dolichocephalic (long-skulled) but not as extreme as some breeds of dogs, such as greyhounds and Russian Wolfhounds (McGreevy 2004). Canine brachycephaly (short-skulledness) is found only in domestic dogs and is related to paedomorphosis (Goodwin 1997). Puppies are born with short snouts, with the longer skull of dolichocephalic dogs emerging in later development (Coppinger 1995). Other differences in head shape between brachycephalic and dolichocephalic dogs include changes in the craniofacial angle (angle between the basilar axis and hard palate) (Regodón 1993), morphology of the temporomandibular joint (Dickie 2001), and radiographic anatomy of the cribriform plate (Schwarz 2000). All cited in Roberts.
One study found that the relative reduction in dog skull length compared to its width (the cephalic index) was significantly correlated to both the position and the angle of the brain within the skull, regardless of the brain size or the body weight of the dog.
+ Bite force adjusted for body weight in Newtons per kilogram Canid Carnassial Canine Wolf 131.6 127.3 Dhole 130.7 132.0 African wild dog 127.7 131.1 Greenland Dog (domesticated) 117.4 114.3 Coyote 107.2 98.9 Side-striped jackal 93.0 87.5 Golden jackal 89.6 87.7 Black-backed jackal 80.6 78.3
Respiratory system
The respiratory system is the set of organs responsible for the intake of oxygen and the expelling of carbon dioxide. As dogs have few sweat glands in their skin, the respiratory system also plays an important role in body thermoregulation.
Dogs are mammals with two large lungs that are further divided into lobes. 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 presence of a muscular structure, the diaphragm, exclusive to mammals, divides the peritoneal cavity from the pleural cavity, besides assisting the lungs during inhalation.
Inbreeding dogs can cause brachycephalic airway syndrome. The dog's face can have a shortened skull, facial and nasal bones, stenotic nares, a hypoplastic trachea, and everted laryngeal saccules.
Digestive system The organs that make up the canine digestive system are the same as those in most other mammals, including a mouth, esophagus, stomach, small and large intestines, rectum, anus, liver, and pancreas.