Scapular winging.

Note the origin and insertion of the serratus anterior muscle.

http://www.vancouveryoga.com/anatomy_serratusanterior.html

http://commons.wikimedia.org/wiki/Image:Gray202.png



http://www.exrx.net/Muscles/SerratusAnterior.html


If it becomes weak or stops working due to issues with the long thoracic n., scapular winging can occur...

Scapular winging looks like this:



http://www.injuryupdate.com.au/images/injury_details/shouldernerve.JPG




http://www.maitrise-orthop.com/corpusmaitri/orthopaedic/112_kelly/kelly-fig10.jpg




www.thieme-connect.com/.../200102/jrm00698.01




http://www.med.nyu.edu/neurosurgery/pns/images/Fig37.jpg

Recommended texts

Started a list (at left) of textbooks that I have found useful when learning anatomy.

Extensor expansion and extensor hood.

The extensor digitorum muscle inserts into the intermediate and distal phalanges of digits II-V via a tendinous aponeurosis (located on each individual digit) called the extensor expansion. By doing so, contraction of this muscle causes extension of the MCP and IP joints.

The expansion itself consists of two parts: a triangular, annular “hood” located around the MCP joints and proximal phalanges; and a single median band that runs dorsally along the intermediate phalanges to insert into the distal phalanges. This band is connected to the fibrous digital sheath on the anterior sides of each finger by retinacular ligaments.

The extensor exapansion is also the insertion of the lumbricals and interossei. The lumbricals insert onto the lateral hood (aka “extensor hood” or “dorsal hood”) of the expansion. Because of this, the lumbricals assist in extending the IP joints during MCP extension and are responsible for this extension during MCP flexion (which they assist in as well).

The interossei have a partial attachment into the expansion hood. Due to this, they assist the lumbricals in their actions (as well as ABduction/ADduction).

Pictures from http://home.comcast.net/~wnor/lesson5musofpostforearm.htm, Wesley Norman, PhD, DSc.

Explanation of pre- and postaxial nerves of the brachial plexus:

In order to understand this concept, you must first understand that for there are pre- and postaxial structures, they must be oriented around an axis.

Axis - a center line to which parts of a structure or body may be referred. (The American Heritage® Stedman's Medical Dictionary, 2002, Houghton Mifflin Company.)

Now, notice that the brachial plexus consists of five nerve roots (C5-T1). Logically, the C7 root is the center (middle or ‘midline’) of this group. This means that C7 is the axis of this nerve grouping.

As the lecture notes indicate, pre-axial nerves are found cranial to this axis, and postaxial nerves are found caudal to the axis (although for practical purposes the axis can be included in either subgroup due to nerve fiber contribution). Therefore, the musculocutaneous (C5-C7) and axillary (C5-C6) nn. are pre-axial, since they are formed by contributions from C7 and above. The ulnar (C7-T1) n. is postaxial, since it is formed by contributions from C7 and below.

Note that the radial and median nn. are not considered to be either pre- or postaxial. This is because they receive contributions from all of the roots of the brachial plexus, and therefore cannot be grouped with those branches formed only from roots above or below the axis…