1. the descending and subterranean part of a plant.
2. that portion of an organ, such as a tooth, hair or nail, that is buried in the tissues, or by which it arises from another structure, or the part of a nerve that is adjacent to the center to which it is connected, e.g. root of neck, root of tail.
- calcified r. canal — restriction of the diameter of the root canal due to calicification; seen in older animals.
- r. canal — that part of the dental pulp cavity extending from the pulp chamber to the apical foramen. Called also pulp canal.
- r. canal therapy — see endodontics.
- dental r. elevator — screwdriver-shaped instrument with a grooved and beveled blade. By pushing the tip of the blade between the tooth root and the alveolar wall the periodontal membrane is broken and the root is elevated and removed.
- dorsal r. — the sensory division of each spinal nerve, attached centrally to the spinal cord and joining peripherally with the ventral root to form the nerve before it emerges from the intervertebral foramen.
- hair r. — the part of the hair buried in the hair follicle.
- mesenteric r. — the small area of attachment of the mesentery to the dorsal abdominal wall at about the level of the first lumbar vertebrae. It encloses the vessels and nerves that supply the intestine.
- motor r. — ventral root.
- nerve r's — the series of paired bundles of nerve fibers which emerge at each side of the spinal cord, termed dorsal (or posterior) or ventral (or anterior) according to their position. A series of dorsal and ventral roots join to form a spinal nerve. Certain cranial nerves, e.g. the trigeminal, also have nerve roots.
- penis r. — the attachment of the penis by two crura to the lateral parts of the ischial arch.
- r. perforation — an accidental occurrence when filing a root canal.
- r. planing — see dental planing.
- sensory r. — dorsal root.
- r. signature — referred pain down a limb, causing lameness or elevation of the limb, resulting from entrapment of the spinal nerve, usually by an extruded intervertebral disk.
- r. sheath cuticle — single layer of cornified cells of the hair follicle interdigitating with the cornified cells of the hair cuticle.
- tongue r. — caudal part of the tongue attached to the hyoid bone, soft palate and pharynx.
- ventral r. — the motor division of each spinal nerve, attached centrally to the spinal cord and joining peripherally with the dorsal root to form the nerve before it emerges from the intervertebral foramen.
