Dog Morphology and Functional Anatomy

• Morphology and functional anatomy of dogs includes domestication, skull types, dental development, locomotion, and coat variations.
• These characteristics influence behavior, health, and breed-specific adaptations.

Domestication of the Dog

• Occurred between 40,000 and 20,000 years ago.
• Early humans and wild canines had a co-evolutionary relationship.
• Dogs were buried similarly to humans at burial sites, indicating social/emotional significance.
• Ancient dog DNA provides genetic evidence of domestication.
• 8,000-year-old rock engravings in Saudi Arabia show humans hunting with dogs.

General Characteristics of Dogs

• They have developed advanced social structures with hierarchical behaviors as pack animals.
• Enhanced night vision due to the tapetum lucidum, a reflective layer behind the retina.
• They have acute senses with 200 million olfactory cells for smell compared to 5 million in humans.
• Hearing ranges from 10 Hz to 40 kHz compared to 16 Hz to 20 kHz in humans.
• Canine Intelligence allows interpreting human cues, following commands, and solving problems.

Body Structure of the Dog

• The head houses sensory organs (eyes, ears, nose) and feeding/communication structures.
• The cervical region supports the head and is crucial for balance.
• The trunk includes the thoracic region, which protects the heart and lungs.
• The abdominal region contains digestive and reproductive organs.
• The pelvic region supports mobility for the hindlimbs.
• Limbs facilitate digitigrade locomotion, like walking on toes.
• The tail provides balance and aids in communication through body language.

Biometric Measurements

• Height at withers refers to the ground-to-shoulder top measurement.
• Body length spans from nose to tail base.
• Limb length measures from ground to elbow.
• Head length spans from muzzle to skull top.
• Dog conformation is evaluated using biometric parameters.

Tail Structure and Communication

• Tail types include curly, docked (surgically shortened), and otter (thick, ideal for swimming).
• Tail positions when wagging include high-stiff(dominance and alertness) and low-tucked(fear or submission).
• A fast and broad wag indicates friendliness, while a slow wag indicates caution.
• High, vibrating wags indicate potential aggression.

Coat and Fur Types

• Tail length can be short, medium, or long.
• Texture: Smooth, Wavy, or Wire-Haired
• Color can be simple(solid color), composed(two-tone, e.g., wolf or fawn coat), or mixed(complex patterns, e.g., brindle).
• Undercoats aid in thermal regulation, with some breeds experiencing seasonal shedding.

Limbs and Locomotion

• Walks involve four legs in contact with the ground at different times which uses symmetrical gaits.
• A trot is a symmetrical gait where diagonal legs move together in a two-beat rhythm.
• A gallop is an asymmetrical gait is the fastest, with aerial phases.
• Pigeon-toed feet point inward.
• Cow hocked hindlimbs curve inward.

Spine Structure

• The spine consists of cervical (7 vertebrae), thoracic (13 vertebrae), lumbar (7 vertebrae), sacral (3 fused vertebrae), and coccygeal (20-23 vertebrae) regions.
• Cervical Vertebrae support the head.
• Thoracic Vertebrae attaches ribs.
• Lumbar Vertebrae supports abdomen and hindlimbs.
• Sacral Vertebrae connects spine to pelvis.
• Coccygeal Vertebrae forms tail.
• Spinal disorders such as intervertebral disc disease (IVDD) can cause paralysis.

Skull and Muzzle Types

• Different skull morphologies affect breathing, vision, and bite force.
• Brachycephalic skulls are short and broad with a flattened muzzle.
• Brachycephalic breeds like Bulldogs and Pugs are prone to brachycephalic obstructive airway syndrome (BOAS). -Dolichocephalic Muzzles are long and narrow.
• Dolichocephalic breeds like Greyhounds and Borzoi have enhanced airflow and excellent field of vision.
• Mesocephalic skulls have an intermediate shape, as seen in Labrador Retrievers and Beagles.
• Mesocephalic Breeds has balanced vision, breathing, and bite force.
• The muzzle contains the Jacobson’s (vomeronasal) organ, crucial for scent detection.

Constitutional Morphologies (Body Types)

• Brevilinear (Brachymorph): Short, compact body with a wide chest (e.g., English Bulldog, French Bulldog).
• Mediolinear (Mesomorph): Balanced proportions with moderate strength/agility (e.g., Dalmatian, English Setter).
• Longilinear (Dolicomorph): Slender, elongated with long limbs for speed (e.g., Greyhound, Borzoi).
• Anacolimorph: Normal-sized head/neck/trunk but short limbs (e.g., Basset Hound, Dachshund).

Dental Chronometry (Development and Aging of Teeth)

• Dental chronometry studies tooth development, eruption, wear, and aging.
• Dogs are diphodonts, having two sets of teeth: deciduous ("baby") and permanent ("adult").
• The first set of teeth appears between 3 and 6 weeks of age.

Puppy Teeth (Deciduous Dentition)

• Puppies have 28 deciduous teeth, including 12 incisors, 4 canines, and 12 premolars (molars absent).
• Deciduous teeth erupt between 21-30 days.
• All deciduous teeth fully erupt by 6 weeks of age.
• They are replaced by permanent teeth between 4 to 7 months of age.

Adult Teeth (Permanent Dentition)

• Adult dogs have 42 teeth: 12 incisors, 4 canines, 16 premolars, and 10 molars.
• Incisors are used for nibbling and grooming, canines for grasping and tearing, premolars for shearing, and molars for crushing food.
• Incisors emerge at 3-5 months, canines/premolars at 4-6 months, and molars at 4-7 months.
• All permanent teeth should be in place by 8 months of age.

Aging Dogs Based on Teeth Wear

• Approximate age estimations can be made through tooth wear and tartar accumulation.
• 10 months – 2.5 years: White teeth with slight wear on incisors.
• 2.5 – 5 years: Squared incisors with tartar deposition on molars.
• 6 – 10 years: Worn teeth with heavy tartar buildup.
• 10+ years: Possible loss of teeth due to severe wear or periodontal disease.

Dental Occlusion (Bite Types)

• Bite type is determined by the alignment of the maxilla (upper jaw) and mandible (lower jaw).
• The perfect scissors bite involves upper incisors slightly overlapping lower incisors.
• Prognathism is an overextended lower jaw common in brachycephalic breeds like Bulldogs.
• Enognathism is an overextended upper jaw, considered a defect.
• Torques refer to misaligned canines embedding incorrectly, causing occlusion issues.

Tongue Functions in Dogs

• The tongue is involved in digestion, communication, thermoregulation, and sensory perception.

Mechanical and Digestive Functions

• Food manipulation involves moving food to the premolars and molars.
• Swallowing involves working with the pharynx to push food into the esophagus.
• The tongue has 1,700 taste buds, making them capable of detecting sweet, salty, sour, and bitter flavours.
• Dogs can taste sweetness unlike cats, making them attracted to fruits and carbohydrates.

Grooming and Wound Care

• Dogs lick wounds to remove debris and apply saliva, which contains antibacterial enzymes like lysozyme and peroxidase.
• Mothers lick puppies to stimulate excretion and maintain hygiene.

Communication and Social Behavior

• Licking is a submissive gesture often directed at dominant pack members or humans.
• Excessive licking can indicate stress, anxiety, or medical issues such as allergies.

Thermoregulation

• Dogs do not sweat through skin but regulate body temperature through panting and vascular dilation.
• Panting involves rapid tongue movements for evaporative cooling.
• Vascular dilation increases blood flow in the tongue to release heat.

Drinking Mechanism

• Dogs use a high-speed liquid capture method.
• The tongue extends below the water surface and curls backward, forming a ladle-like shape.
• Water adheres to the tongue surface due to adhesion and inertia when withdrawn.
• Canine jaws snap shut before the water falls back down.
• Process is approximately 5 times more efficient than drinking water with gravity alone.