When looking to create or enhance textures the Emboss Filter is a handy tool. It allows the illustrator to create embossed, beaded and engraved effects over large areas consistently and quickly. Embossing works by identifying areas of high contrast and adding two areas of pixels (white and black) on opposite sides of the high contrast area. The white and the dark represent the highlight and the shadow of the embossed area and are what create the effect.
My technique drops out the background white of drawings that are scanned and allows illustrators to work on the sketch in Normal mode. The advantage to this process is to do away with converting the scanned sketch into Multiply mode in order to color it. In Multiply mode the sketch loses integrity when paint fills "multiply" through the sketch from below and becomes mingled as a tint of the sketch color above. Furthermore, you have to convert the sketch back to normal mode to color it and all the white comes back obscuring the effect the color change has with the colors layered underneath.
The texture of fibrous tissue like muscle, ligament and tendon can be quickly rendered in Photoshop with the aid of a preliminary pencil sketch. Setting a sketch layer to Multiply mode in a Photoshop painting can create the shadow areas of fibrous texture (sketch layer opacity = %65). The same sketch can also be used to create highlights for some subjects. This works especially well for fibrous tissue if the sketch is prepared with this application in mind.
A pattern brush consists of an object or group of objects that are repeated along the length of a path. A pattern brush can be applied to any path - straight or curved - and the objects will stretch and deform to follow the shape of the path. I use this feature all the time for vascular endothelial cells, epithelial membranes, lipid bilayers, and any other situation where I need to repeat many identical objects along the length of a path.
30 years ago I began my foray into pen and ink drawing with flexible nib pens. Two prongs hold ink and a varied pressure releases the ink in a thin and thick manner depending upon the pressure applied. Having practiced the medium in this manner has allowed me to find an alternative media that works just how I would like. My pen and ink instruments of choice now are disposable Pigma Micron pens (Sakura Color Products). My thinking behind their use has not changed. I am still rendering my subjects with fluidity utilizing thick and thin inked lines while remembering that communicating the message is still paramount to a medical illustrator's mission.