Re: How are muscles attached to bones at the molecular level?

REFERENCE(S):1)Introduction to Organic and Biochemistry, 3rd Edition,
Brown and McClarin, Willard Grant Press
2)Histology, 3rd Edition, Greep and Weiss, McGraw-Hill Book Company

Dear Christina,
This is a most complex question and not one that is usually encountered
in the classroom!  To explain how the concept of "molecular attachment"
can occur, you need to understand that the chemical molecule called
collagen is the predominant, fibrous, connective tissue protein, which
provides great strength and anatomic form to both bone and tendon.  Both
bone and tendon share the same tissue classification since they are both
connective tissue. Collagen is a biochemically specific, long, twisted,
three-stranded protein with a distinctive amino acid composition.  It is
an extremely common protein among vertebrates.

Any bone and its attached muscle will develop so that the bone's
collagen fibers are identical to and continuous with the collagen fibers
in the connected tendon!  Thus the same same molecule that composes most
of the bone is identical to the molecule that makes up the tendon.There
is no need to struggle further with the ideas of how attachment can
occur in this biological situation, since the molecules "see themselves"
(and you should to) as already "attached."

Muscle is a second tissue type, which is fundamentally different from
connective tissue since it is made to contract or shorten.  But the fact
to realize is that the individual muscle fiber cells, the groups of
fiber cells called muscle fascicles, and the muscles themselves (you see
them during dissection) are all wrapped very securely by our old friend
the connective tissue!  In fact, the fascicles and the muscle are
tightly encircled by the identical protein molecue described above we
called collagen.  Muscles insert into and are attached to the bones they
"move" by their tendon "extensions"!  In reality then, the muscle, its
tendon, and the attached or connected bone can be visualized as a three
related, closely coordinated, working pieces inside one, single,
continuous, protein "sheath", which biochemists call COLLAGEN and
anatomists call fibrous connective tissue.  The human body is indeed a
miracle.

Does this make "molecular sense?"  I hope so.  It is the best I can do
until you study biochemistry, gross anatomy, and histology (microscopic
anatomy).  Good luck in your life-long learning.  Keep thinking in these
fundamental terms and a world of excitement will await you.