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The thick layer of skin beneath the outer epidermis, containing blood vessels, nerve endings, and connective tissue; also referred to as dermis.

Modified molars (and premolars in carnivorans) that are adapted for shearing flesh rather than grinding, optimizing them for a carnivorous diet.

Blind sacs located at the junction of the stomach and the intestines in some fishes, they secrete digestive enzymes and absorb nutrients.

A common cavity at the end of the digestive tract for the release of both excretory and genital products in vertebrates except most mammals.

The tough, fibrous outer layer of the eye that provides protection and form; it is the white part of the eye in humans.

The duct through which sperm move from the testicle to the urethra in male animals; a component of the male reproductive system.

A gland located at the base of the tail in birds that secretes an oil used for preening feathers. It maintains the quality of the plumage.

A mammal that walks on its toes, not touching the ground with its heels, which typically results in quieter and more energy-efficient movement.

Bacteria living in a symbiotic relationship within the guts of some animals, they assist in breaking down cellulose and other difficult to digest plant materials.

Species in which the young are relatively mature and mobile from the moment of birth or hatching.

The part of a turtle's or tortoise's shell forming its underside, it provides protection for the ventral internal organs.

A keratinous covering over the distal phalanges of the feet of certain animals, which protects the digit tips and provides support and traction.

Openings in the body of fish and some amphibians through which water exits after passing over the gills; important for respiration.

An extra toe or functionless digit not reaching the ground on the foot of many mammals with claws, often remnants of ancestral digits.

A specialized stomach constructed of thick muscular walls used for grinding up food, often found in birds.

A complex network of interconnected small blood vessels, it functions as a countercurrent exchange system to trap heat or gas exchange in some fish and mammals.

The first digit of the hind foot of an animal, equivalent to the human big toe; plays a significant role in balance and grasping.

A small muscle within the ear that dampens the sound of chewing and other loud noises, it reflexively contracts in response to loud sounds.

A thin-walled expanded portion of the alimentary tract used for the storage of food prior to digestion; found in birds and some insects.

The pair of appendages in front of the mouth in arachnids and some other arthropods, often modified to function as pincers or fangs.

A structure that runs longitudinally along the sternum in birds to which flight muscles attach, it provides increased muscle attachment area for powerful wing strokes.

Second pair of appendages in arachnids located near the mouth, used for feeding, sensory perception, and mating in various species.

A ligament that stabilizes the head and neck, allowing animals, particularly quadrupeds, to hold their heads up without using muscles.

The external part of the ear in humans and other mammals; it collects sound waves and directs them into the ear canal.

The individual visual units that make up the compound eyes of insects and crustaceans, they provide a wide field of vision.

Extensions of the skull grown by members of the deer family; they are true bone, are shed and regrown annually, and are typically used for sexual selection and territorial defense.

Small, nipple-like structures on the skin or surface of an organ, they increase surface area for absorption and sensation.

The hard upper shell of a turtle, crustacean, or arachnid, often acting as a protective shield.

Special sensing organs in the snouts of cartilaginous fishes like sharks, allowing them to detect changes in electric fields in water.

Another term for the uropygial gland, it secretes oils that birds use to maintain their feathers.

Long, fibrous plates located in the mouths of baleen whales, used to strain plankton from the water for food.

The highest part of a horse's back, located at the base of the neck above the shoulders, it is an important area for measuring horse height.

The fourth and final stomach compartment in ruminants, it is known as the 'true stomach' and is where the actual digestion of food occurs.

A small bone found in the heart of some animals, particularly in the heart of cattle, which helps support the valves and muscular ridges.

Commonly known as the eardrum, it's a thin membrane that vibrates in response to sound waves and is involved in hearing.

A significant part of the anatomy of mollusks, it secretes the shell in shelled mollusks and performs a respiratory function in others.

Paired fins on either side of a fish's body which are often used for steering and maneuverability in water.

An unpaired fin located on the ventral side of a fish posterior to the anus, used for maintaining stability in the water.

A longer fringe of hair found on the neck of certain animals, such as horses or lions; may provide a visual display or offer protection to the neck.

The cartilaginous section at the lower end of the sternum which is not attached to any ribs. It is important in the attachment of abdominal muscles and diaphragm.

The muscular part of the hind limb between the stifle and the hock in quadrupeds, especially in horses. It's equivalent to the human calf.

A pouch connected to the junction of the small and large intestines that absorbs fluids and salts and digests cellulose via microbial fermentation in herbivores.

A respiratory opening on the body of an insect or fish, it can regulate water intake and gas exchange.

The fluid equivalent to blood in most invertebrates, occupying the hemocoel, it directly bathes the organs in nutrients and gases.

Fleshy filaments growing from the mouth or snout of some fish, these are sensory organs that help the fish to taste and feel its environment.

Describing animals that give birth to live, free-moving offspring, where the embryos develop inside the body of the parent.

Cells containing melanin responsible for pigmentation in animal skin, fur, and feathers; these cells can change size to affect coloration.

Species in which the young are born or hatched helpless and typically require significant parental care and feeding.

An olfactory structure found in some animals, including snakes and lizards, which analyzes airborne chemicals, it plays a role in the sensing of pheromones and prey.

Part of the brainstem that controls vital life functions such as breathing, heart rate, and blood pressure in vertebrates.