Ulna

The ulna (/ˈʌlnə/) is one of the two long bones in the forearm (the other is the radius). It is on the side opposite the thumb, extends from the elbow to the wrist, and runs parallel to the radius, which it exceeds in length and size. In anatomical position, when the arms are down at the sides of the body and the palms of the hands face forward, the ulna is located at the side of the forearm closest to the body (the medial side). The bone may break due to excessive weight or impact.

Structure

The ulna is broader close to the elbow, and narrows as it approaches the wrist.

Close to the elbow, the ulna has a bony process, the olecranon process, a hook-like structure that fits into the olecranon fossa of the humerus. This prevents hyperextension and forms a hinge joint with the trochlea of the humerus. There is also a radial notch for the head of the radius, and the ulnar tuberosity to which muscles attach.

Close to the wrist, the ulna has a styloid process.

Histology

The ulna is a long bone. The long, narrow medullary cavity of the ulna is enclosed in a strong wall of cortical tissue which is thickest along the interosseous border and dorsal surface. At the extremities the compact layer thins. The compact layer is continued onto the back of the olecranon as a plate of close spongy bone with lamellæ parallel. From the inner surface of this plate and the compact layer below it trabeculæ arch forward toward the olecranon and coronoid and cross other trabeculæ, passing backward over the medullary cavity from the upper part of the shaft below the coronoid. Below the coronoid process there is a small area of compact bone from which trabeculæ curve upward to end obliquely to the surface of the semilunar notch which is coated with a thin layer of compact bone. The trabeculæ at the lower end have a more longitudinal direction.

Coleophora

Coleophora is a very large genus of moths of the family Coleophoridae. It contains some 1,350 described species. The genus is represented on all continents, but the majority are found in the Nearctic and Palaearctic regions. Many authors have tried splitting the genus into numerous smaller ones, but most of these have not become widely accepted.

As with most members of the family, the larvae initially feed on the seeds, flowers or leaves of the host plant, but when larger, they feed externally and construct distinctive protective silken cases, often incorporating plant material. Many species have specific host plants; discarded larval cases are often scattered thickly on affected plants.

Gallery

Female genitalia of C. lusciniaepennella

Female genitalia of C. lusciniaepennella

C. serratella case

C. serratella case

Soft Rush (Juncus effusus) inflorescence with feeding damage and cases of C. caespitiella

Soft Rush (Juncus effusus) inflorescence with feeding damage and cases of C. caespitiella