Lamella-bone - the microscopic structure of cortical bone gives it the appearance of concentric or parallel plates ( from Latin, lamella, the diminutive of lamina, meaning a plate or leaf).

Lamina propria - the layer of loose connective tissue underneath the epithelium of mucosa, which provides physical and nutritional support.

Lamina-dura - the name given to the radiographic appearance of a dense layer of bone around the tooth root. It represents the dense cortical bone lining6 the tooth socket.

Laminin - an adhesive molecule of connective tissue related to fibronectin andtenascin.

Langherhans cells are active in the immune response of the skin and mucous membrane. They act as sentries, detecting the presence of foreign antigens on the surface of the epithElium. They do not contain keratin and are thus sometimes called clear cells.

Lectin - a protein molecule which bindson to a specific sequence of sugars. Bacteria may use lectin attachments to bind onto each other or oral surfaces.

Leucocytes - un pigmented (white) cells of the blood. Those with granular cy lasm are neutrophils, eosinophils and basophils. The agranulocytes are lymphocytes and monocytes.

Leucotriens- concerned with signalling between cells of the immune system and a member of the eicosanoid family of hormones.

Ligand - a protein molecule which binds to another specific protein molecule. The forces of the bond are week and thus protein-ligand bonds depend on close fit of one molecule to the other, so as to capture as many bonding sites as possible. Ligands are specific for a particular protein. They are found on cell surfaces of microorganisms where they assist in cell adhesion. They are also sights on cell membranes onto which protein messengers attach such ascytokines (see also lectins).