Anatomy of the Dog (copy)

Evolution and Domestication

• Dogs and wolves share a common ancestor; dogs did not evolve from modern wolves.

• Genetic divergence occurred at least 15,000 years ago (range: 14,000-17,000 years), varying by location and fossil evidence.

• Mandible shortening is a key indicator in the fossil record.

• Domestication may have been driven by dogs themselves, coinciding with the rise of human agriculture.

• North American dog-like canids date back 9,000 years and served as pack animals.

• Older dog breeds (primarily Asian) exhibit more genetic variability and resemblance to their wolf ancestor (e.g., Basenji).

• Breeds bottlenecked geographically, leading to signature dog breeds on islands throughout the Mediterranean.

• Dog domestication coincided with human territorial expansion, with dogs benefiting from proximity to humans.

• Genetic breakdown shows wolves branching off long ago, with older breeds (Asian and African) being genetically distinct. Phenotype often reflects genotype.

• Terriers are closely related, branching off in the late 1500s and 1600s. Genetically new.

Taxonomy

• Linnaeus originally coined the term Canis familiaris for the modern dog.

• Current classification: Canis lupus subspecies familiaris (subspecies of the wolf).

• Taxonomic ranks: Kingdom Animalia, Phylum Chordata, Class Mammalia, Order Carnivora, etc.

• Dogs are not true carnivores, but omnivores.

Behavior and Use

• Dogs have been categorized based on the following traits: playfulness, curiosity, chase proneness, sociability, aggressiveness. These traits vary within breeds and individuals.

• These behaviors are manipulated for companionship, herding, guarding, hunting, etc.

• Dogs serve a wider variety of purposes when compared to other domesticated species such as cows and horses.

Diet

• Dogs are omnivores, not obligate carnivores like cats.

• They can adapt to a variety of protein sources, even those of lower quality.

• Wild dogs forage for vegetables, fruits, plant protein, and meat protein.

• A majority of dog food is not meat protein-based.

• The ideal dog diet is not completely defined, but it does not have to consist majorly of meat.

• Toxic foods: chocolate, onions, garlic, grapes, raisins.

• Grapes and raisins can be nephrotoxic. The toxicity percentage cannot be predicted. (e.g., one dog can eat 52 grapes and be fine, and it's litter mate literally can eat three grapes and have acute renal failure.)

• Some nuts can be GI toxic due to volatile oils.

Anatomical Concepts and Terms

• Anatomical position: how anatomical structures are described.

• Varies depending on the animal.

• Humans (bipeds): standing erect, palms forward.

• Dogs (quadrupeds): standing on four feet, palms down.

• Locomotion: dogs are cursorial (adapted for running) and digitigrade (digits have the majority of contact with the ground).

• Palms (palmar surface) or plantar surface do not usually come in contact with ground.

• Their limbs have been adapted to a running or rotary gallop. The shoulder blades are on the lateral side of the body, unlike humans.

• Shoulder joint is freely movable.

• Mass of forelimb is high and very proximally located when compared to a bipedal animal.

• Radius is the dominant bone in the antebrachium adapted for stability and running. There is very little pronation and supination.

• The number of digits that come in contact with the ground have been reduced. In canines it's 4 digits that hit the ground.

• Mass of the limb is proximal and there is a reduction of muscle mass distally.

Anatomic Planes

• Sagittal: divides the animal into left and right.

• Midsagittal: divides the animal into equal left and right halves.

• Transverse: separates the animal into front and back.

• Dorsal (frontal in humans): separates the animal into top and bottom, parallels the vertebral column.

Directional Terms

• Cranial: towards the head.

• Caudal: towards the tail.

• Anterior and posterior, superior and inferior: human terms, used in dogs primarily for structures within the eyes.

• Dorsal: towards the back.

• Ventral: towards the belly.

• Medial: towards midline.

• Lateral: away from midline.

• Proximal: towards the torso.

• Distal: away from the torso.

• Cranial and caudal: used until you reach the foot, then use dorsal and palmar.

  • The foot is from the wrist or the ankle down.

• Manus is the forepaw.

• Pez is the foot.

More Directional Terms

• Maxillary: upper jaw.

• Mandibular: lower jaw.

• Longitudinal: pertains to the long axis of the body.

• Superficial and deep: skin structures.

• Axial: going towards the imaginary middle line.

• Abaxial: going away from the imaginary middle line in relation to an extremity.

• Palmar and plantar: relate to the manus or the pes.

• Oral and aboral: structures in the mouth.

• Ipsilateral: same side.

• Contralateral: opposite side.

Regional Terms

• Need to be able to use off hand and should be part of your repertoire easily.

• The stop is at the bottom of the forehead.

• The withers are between the shoulder blades.

• The hawk is the ankle.

Muscle and Joint Actions

• Related to the animal's anatomical position.

• Extension: increasing the angle formed by a joint.

• Flexion: decreasing the angle formed by a joint.

• Abduction: moving a limb away from midline.

• Adduction: moving a limb towards midline.

• Supination: rotating the limb where the dorsum of the paw is going laterally.

• Pronation: pronating the top of the paw immediately. You're turning it over immediately.

The Mammalian Plan

• All mammals start with five digits embryologically.

• Five metacarpals or metatarsals proximal to digits.

• Digits are numbered from medial to lateral.

• In canines, the the dewclaw is number 1.

• Digits 2, 3, 4, and 5 project out lateral.

• Each digit has three phalanges, except digit one has two.

• Digit one (dewclaw) may be reduced or absent on the hind limb.

• Some breeds show polydactylism (multiple digits).

• Some mammals show extreme reduction of the number of digits.

Organ Systems

• This is a general anatomical overview to refresh you on core concepts.

Skeletal System

• Approximately 320 bones (varies by breed due to caudal vertebrae number).

• Regions: cervical, thoracic, lumbar, sacral, caudal.

• Scapula located laterally.

• No clavicle in dogs.

• Hind limb has the same structures learned from grade school.

• Skull: prolonged rostally, projecting nasal bones and maxilla.

• Complete orbit around the eye is not completely close. It is not closed with bone, but with ligaments and muscles. Muscles correspond to closing the jaw.

• The same bones are located as in humans they're just located in different places.

• Axial skeleton: vertebral core (skull, vertebral column).

• Specific number of vertebrae is rigid across dog breeds.

• Seven cervical vertebrate.

• 13 thoracic.

• Seven lumbar.

• Three fused sacral vertebrate.

• C1 (atlas): holds up the skull

• C2 (axis): rotational movement of the skull.

• The fused pelvis is the last portion of the axial skeleton.

• Appendicular skeleton: the appendages.
  Forelimb: thoracic.

• Hindlimb: pelvic.

• Individual vertebrae structure: spinous process, transverse processes, vertebral canal, vertebral body.

• Lamina: spans between the transverse and spinous process.

• Pedicle: from the transverse process to the body.

• Appendicular skeleton
  Thoracic or forelimb and pelvic or hindlimb.

• Carpus: the wrist.

• Tarsal area: the ankle.
  Canine dental formula (Permanent): I 3/3, C 1/1, P 4/4, M 2/3

Muscular System

• Skeletal muscle: locomotion, support, protection of body cavities.

• Striated: histological organization.

• Voluntary: attached to the skeleton used in movement.
  Origin, insertion, action, innervation, blood supply.

Muscle Groups

• Head: very muscular for grazing, eating, chewing, and biting.

  • Genioglossus muscles helps move the tongue around.

  • The digastrics have 2 bellies involved in opening of the jaw.

  • Jaw Closing-Temporalis, Masseter, Pterygoids

Eye Muscles

• Moves the eye in different ways, medial, lateral, dorsal, ventral, oblique.

• The superior rectus is known as the dorsal rectus in dogs.

• Dorsal and ventral oblique muscles help the rotational movement in the eye.

• Retractor bullae is one that helps pull the eye back in.

• 
  Two sets of muscles in the iris.

• Radial muscles help open the eyes.

• Circulatory muscles help restrict the pupil.

Torso

• LD: latissimus dorsi

• Pectoral muscles.

• TB: triceps brachii. The Gluteal.

  • QF-Quadriceps femoris.

  • Hamstrings: Semimembranosus, a semitendinosus, and a biceps femoris.

Nervous System

• Anatomically: central nervous system (brain, spinal cord), peripheral nervous system (everything else).

Canine Brain

• Organized into lobes, sulci (depressions), and gyri (protrusions).

• Olfactory lobe (OL) is large due to canine sense of smell.

• Cranial nerves branch off the base of the brain stem.

• Spinal cord: cervical area is wider than thoracic, lumbar area is also wide. Nerve cell bodies are higher in cervical and lumbo areas. Distinguishing width is also apparent under the microscope.

Peripheral Nerves

• Nerves that are motor, sensory.

• Will lose a lot of things if you get damage to this area.

• Sympathetic fibers are located in individual blood vessels.

Circulatory System

• Mammalian four-chamber heart.

• Arteries go away from the heart.

• Veins goes towards from the heart.

• Aorta pumps out from the heart to the rest of the body.

• Lymphatic system mirror the circulatory system that dumps back into the venous system and plays a role in immunity.

Digestive System

1. Begins at the teeth (dentition).

2. Dental formulae for the dog (D)eciduous teeth
   Permanent teeth.
   I 3/3, C 1/1, P 3/3 = 28 Deciduous teeth
   I 3/3, C 1/1, P 4/4, M 2/3 = 42 Permanent teeth

3. The I = Incisors, C = Canine, P = Premolars, M = Molars.

4. Salivary glands.

5. Esophagus.

The Stomach

• Simple and glandular

• Has a fundus, a body and a pylorus.

• You have a cardiac sphincter and a pylorus sphincter.

• Omentum that sweeps off on both the lesser and greater curvatures of stomach. Will serve as a way to act as a band aid whenever there is micro ruptures.

Digestive System - Organ

• Liver produces bile.

• The gall bladder will receive the bile that will also get dumped into the duodenum.

• The pancreas produces pancreatic enzymes in the duodenum.

• Going down towards the the small intestine which is the jejunum and the ileum.

Lower Intestine

• The cecum which is an area for secondary fermentation.

• Have will project into the three sections of the large intestine which are the ascending, transverse, and descending areas. Those areas help mostly in water reabsorption and to change what’s left of the balls of food into what is actually expelled from the body.

• Anal glands: are tiny glands that produce excretory fluid that is involved in marking. The dump into anal sacs. Anal sacs are what are subject to pathology.

Endocrine System

• Everywhere from the brain on down to the testes.

  1. Brain, at the top or the pitituary glands or what is known as the hypothalamus.

  2. The thyroid glands

  3. Pancreas will help regulate our blood glucose. Has hormones that are there to help with this. Insulin and glucagon can be made with this

  *Adrenal glands - Produces adrenaline and it is involved in stress regulation.

Respiratory System

• Dogs breathe out of their mouth and nose.

• Has a soft palate.

• The larynx is known to act as a wide cage around the vocal cords.

• The primary bronchi: are known to be the branches off the trachea. Primary bronchi. Is located on one going towards each lung. Then secondary branches.

• Has 2 main lungs: The right which has a cranial, middle caudal and an accessory lung.

• and the left lung.

Urogenital System

• Urine Production: has two kidneys and also two ureters that go through the kidneys to the urinary bladder. The will dump in to the urethra. Male or females will differentiate.

• There testicles will be in a location that is pendulum and they have to be outside the body to regulate the temperature that the body is at because the testes need to be at a certain temperature.
  Three way: to make sure temperature:
  1) The cremaster muscle which is there to help with temperature regulation.
  2) The tunica dartosis muscle
  3) The pampinaiform plexus: helps cools down the blood going towards the testes.

• The ductus deferens will go through and will exit to the prostate.
  The female is know to be bicornuate uterus.

Breed Groupings

• Sporting Dogs - muscular and tall. (i.e. Golder Retriever.)

• Hound Group - Very widespread. (i.e. tall skinny, short bulky.)

• Working Dogs are tall and big.

• Terriers - have compact short limbs and fast.

• Herding Dogs - long hair, long snouts.

Individual Breed Differences

• Skull differences based on breeding and genetics from humans. Brachycephalic is shortened Skull type. Dolichocephalic- longer skull type.

• Coat/ Colour Differences -Based on dog functionality. And breedin.

• Ear Orientation and Cropping - UK doesn't do it any more but still does it here a little bit.

• Barrel chested dogs.

• Chondrdroplasia- Form of dwarfism. Some dog’s limbs are turned other ways. It's a gene of dwarfism that bred in dogs that we consider normal.

SIMPLIFIED

• Dogs and wolves share a common ancestor; dogs did not evolve from modern wolves.

• Genetic divergence occurred at least 15,000 years ago (range: 14,000-17,000 years).

• Current dog classification: Canis lupus subspecies familiaris.

• Dogs are omnivores, not obligate carnivores.

• Key anatomical terms: cranial (towards the head), caudal (towards the tail), dorsal (towards the back), ventral (towards the belly), medial (towards the midline), lateral (away from the midline), proximal (towards the torso), distal (away from the torso).

• Muscle actions: extension (increasing joint angle), flexion (decreasing joint angle), abduction (moving limb away from midline), adduction (moving limb towards midline).

• Mammals start with five digits embryologically; dogs may show polydactylism (multiple digits).

• Dog dental formulae: Deciduous I 3/3, C 1/1, P 3/3 = 28 , Permanent $$ I