Rod sheath is an area identified in histologic

Histology

Histology is the study of the microscopic anatomy of cells and tissues of plants and animals. It is performed by examining cells and tissues commonly by sectioning and staining; followed by examination under a light microscope or electron microscope...

 sections of a tooth

Tooth

Teeth are small, calcified, whitish structures found in the jaws of many vertebrates that are used to break down food. Some animals, particularly carnivores, also use teeth for hunting or for defensive purposes. The roots of teeth are embedded in the Mandible bone or the Maxillary bone and are...

. It is found where enamel rod

Enamel rod

An Enamel rod is the basic unit of tooth enamel. Measuring 4 μm wide to 8 μm high, an enamel rod is a tightly packed, highly organized mass of hydroxyapatite crystals...

s, the functional unit of enamel

Tooth enamel

Tooth enamel, along with dentin, cementum, and dental pulp is one of the four major tissues that make up the tooth in vertebrates. It is the hardest and most highly mineralized substance in the human body. Tooth enamel is also found in the dermal denticles of sharks...

, meet interrod enamel

Interrod enamel

Interrod enamel is histologically identified on microscopic views of tooth enamel. Because interrod enamel is located around enamel rods, the areas of interrod enamel enhances the "keyhole" appearance of enamel rods by acting as its border...

. The crystal

Crystal

A crystal or crystalline solid is a solid material whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions. The scientific study of crystals and crystal formation is known as crystallography...

s of both types of enamel meet at sharp angles and form the appearance of a space called the rod sheath. As a result of this space, the rod sheath consists of more protein

Protein

Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

(as opposed to minerals) than other areas of enamel. For this reason, the rod sheath is characterized as being hypomineralized in comparison to the rest of the highly mineralized enamel.

Additionally, the rod sheath is attributed with giving tooth enamel a "fish-scale" appearance under a microscope when the enamel has been demineralized or acid-etched.

The rod sheath is Inorganic matrix tying the enamel rods together