Lorenz Heister (1683-1758) A German surgeon, physician, anatomist, and botanist, Lorenz Heister [also known as Laurentius Heisterus] was born at Frankfurt-am-Main in 1683. As a result of his early studies, he became proficient in Latin, French, English and Dutch. He started medical studies at the University of Giessen, later continuing in Amsterdam, and Leyden, where he obtained his MD degree in 1708.

For a short time Heister became an army surgeon. In 1710 he was appointed Professor of Anatomy and Surgery at the University of Altfdorf. Although he lectured in Latin, Heister published his anatomical treatise “Compendium Anatomicum” in German in 1718. Later, Latin, French, Italian, and Spanish translations were created and published. Heister’s book became the main anatomical and surgical textbook in Europe. The English version was first published in 1743.

Heister is considered the “Father of German Surgery”, including in his books the management of hemorrhage, wounds, fractures, bandaging, instrumentation, and surgery. Heister described the surgical treatment of breast cancer, hemothoraces, spinal fractures, trepanation, oral surgery, and even obstetrical emergencies. He introduced the term “tracheotomy.” Heister also studied the eye, confirming that cataracts are formed within the lens.

•. Heister’s valve (plica spiralis) a spiral fold of mucosa found in the cystic duct
•. Heister’s diverticulum (bulbus superius venae jugularis interna), a dilation of the internal jugular vein found at its origin from the jugular foramen of the base of the cranium

Heister's name is spelled Heisters, in his "Compendium Anatomicum" published in 1756.

Sources:
1. "Heister of the spiral valve of Heister - Lorenz Heister" Gastroenter Hepat News (2006): 131 (3) 696. 
2. “Lorenz Heister: Surgeon (1683-1758)” Stewart, J. Can Med Assoc J. 1929 20(4): 418–419. 
3. "Lorenz Heister (1683-1758). Eighteenth century surgeon" JAMA 202 (11), 1048-1049
4. "Lorenz Heister and oral disease with the original text from his papers". Shklar , G. J Hist Dent (2007); 55:2 68-74

A serosa is a type of epithelium embryologically derived from the mesoderm, thus a serosa can also be called a [mesothelium]. Serosal membranes are found forming sacs that surround structures in the body, such as the pericardium, pleural membranes, and peritoneum.

Serous membranes are characterized by a thin single-layer mesothelium covering a layer of vascularized loose connective tissue. A serosa produces (and absorbs) a watery fluid called "serous fluid" which serves to lubricate organs that require movement such as the heart, lungs and digestive tract : pericardial fluid, pleural fluid, and peritoneal fluid.

The excess production (effusion) of serous fluid can cause serious pathology, such as  pericardial tamponade, hydrothorax, or ascitis (peritoneal effusion) 

The [triquetrum] is one of the bones of the proximal row of carpal bones that form the wrist. Because of its wedge-shape it is also called the [cuneiform] bone, from the Latin [cuneus], meaning "wedge".  Other names for this bone are [triangular] bone and [os triquetrum].

The triquetrum bone articulates with the lunate bone laterally, the pisiform bone anteriorly, and the hamate bone distally. It is separated from the distal ulna by a triangular articular disc.

The accompanying image shows the anterior (volar) surface of the wrist. Click on the image for a larger picture.

Image modified from the original: "3D Human Anatomy: Regional Edition DVD-ROM." Courtesy of Primal Pictures

This is a word of Greek origin. The prefix [epi] means "outer" or "above"; the root term [-thel-] means "nipple" or "female", and the suffix [-ium] means "layer" or "membrane.  The reason for the origin of this words is that in c.1700 Ryusch used this term to refer to the surface layer of cells in the nipple and areola. It was later used to denote any covering superficial layer of cells.  The plural form for epithelium is epithelia.

There are many types of epithelia in the body, and they are described by their histology, or how they look under the microscope: single-layer, multilayered, cuboidal, columnar, etc.

- Although the above is the standard accepted etymology for this word, I have a different interpretation, as the Latin term [tela], meaning "fabric" or "cover" could have been used. Thus explained, the word means "outer cover layer". Who knows?. Dr. Miranda -

"The origin of Medical Terms" Skinner, AH, 1970