Muscles of the Crus

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[ image 1 ] [ image 2 ]

Try to identify the labelled muscles before reading on. You should be doing this on all the images.

Once again, we can group the muscles here into those of the craniolateral crus which flex the hock and extend the digits, and those of the caudomedial crus (although more caudal than medial) which extend the hock and flex the digits.

Remember: If it does not say digital in the name, it does not have an action upon the digits!

Starting with the craniolateral muscles of the crus and moving cranially to caudally, we have the cranial tibial muscle (A), the long digital extensor muscle (B), and the peroneus longus muscle (C). A very small lateral digital extensor muscle is present deep and caudally to the peroneus longus muscle. If you don't believe me, click here. What is the innervation of these craniolateral muscles?

Starting most caudally, the caudal crus muscles include the gastrocnemius muscle (E), the superficial digital flexor muscle (F), which may be more completely covered by the gastrocnemius muscle in your specimen, and the deep digital flexor muscle (D). Evans & deLahunta gives names to the individual heads of the deep digital flexor muscle - we will just call them all the deep digital flexor muscle. If you are uncertain about the superficial digital flexor muscle, trace its tendon, which will course around the medial side of the gastrocnemius tendon to become superficial to it (<).

What common innervation do these caudal muscles have?

The craniolateral muscles (those that flex the hock, extend the digit) are innervated by the peroneal nerve. The caudal muscles (those that extend the hock and flex the digits) are innervated by the tibial nerve.