Companion Animal Body Systems: Structure, Function, and Practical Implications

External Anatomy

The visible body parts of an animal that provide information regarding health, comfort, and suitability for a home.

Directional Terms

Precise language used to describe locations in animal anatomy, including dorsal, ventral, cranial, caudal, medial, lateral, proximal, and distal.

Muzzle (rostrum)

The part of an animal's face that houses the nose and mouth; important for smell in dogs and for vision and hearing in cats.

Nares

Nostrils of an animal, responsible for the sense of smell.

Vibrissae (whiskers)

Specialized tactile hairs that help animals judge openings and detect air movement, especially important in cats.

Pinnae

External ear flaps that funnel sound and can indicate mood through ear position.

Claws

Sharp, pointed structures found in animals; differ in function between dogs (non-retractable) and cats (retractable).

Paw Pads

Cushioned structures on an animal's feet that provide traction and some heat protection.

Tail

An anatomical part that helps with balance and communication in animals.

Mammary Glands

Glands present in both males and females, but functional in females for milk production.

Incisors

Continuously growing front teeth in herbivorous mammals, critical for processing food.

Eyes Placed Laterally

A positioning of the eyes in animals that provides a wide field of view for predator detection.

Hind Limbs

Powerful limbs found in rabbits and similar species, adapted for rapid escape.

Beak (bill)

A bird's anatomical structure that replaces lips and teeth, with shape indicating feeding style.

Feathers

Structures that serve insulation, flight, waterproofing, and communication in birds.

Cloaca

A single external opening in birds serving digestive, urinary, and reproductive tracts.

Scales

Protective outer layer on reptiles that reduces water loss.

Compact Bone

Dense outer layer of bone providing strength and protection.

Spongy Bone

Inner lattice in bones that reduces weight and houses marrow spaces.

Periosteum

Outer membrane of bone important for growth and repair.

Skeletal Muscle

Striated muscle that is mostly voluntary and responsible for movement by attached to bones.

Cardiac Muscle

Striated but involuntary muscle found in the heart, designed for endurance.

Smooth Muscle

Non-striated, involuntary muscle lining hollow organs and tubes for movement.

Growth Plates

Regions of cartilage in long bones where longitudinal growth occurs.

Hypertrophy

Increase in size of muscle fibers as a response to consistent activity and recovery.

Ovaries

Female reproductive organs that produce ova and hormones like estrogen and progesterone.

Testes

Male reproductive organs that produce sperm and testosterone.

Negative Feedback

A control mechanism by hormones where an effect reduces further hormone release to maintain homeostasis.