structure of skeletal muscle
ALL OF THESES TISSUE SHEATHS ARE CONTINUOUS WITH ONE ANOTHER
AS WELL AS WITH THE TENDONS THAT JOIN MUSCLES TO BONES IN AT LEAST
TWO PLACES
Nerve & blood supply: in general one nerve, on
artery, and one or more veins serve each muscle. All of these
structures enter or exit near the central part of the muscle and
branch through its connective tissue sheaths. unlike cells of cardiac
and smooth muscle tissues, which contract w/out nerve stimulation,
every skeletal muscle fiber is supported with a nerve ending that
controls its activity. skeletal muscle has
very rich blood supply. This makes sense because contracting
muscle fibers use huge amounts of energy and require almost
continuous delivery of oxygen and nutrients via the arteries.
Connective Tissue Sheaths: In all intact muscle
tissues, several different sheaths wrap individual muscle fibers.
Collectively, these sheaths support each cell and reinforce and hold
together the muscle as a whole. There connective tissue
sheath types:
Epimysium:
(outside the muscle)-overcoat of dense irregular tissue
surounding the whole muscle.
Perimysium and
fasicals: (withen the muscle)- the muscle fibers
are grouped into fascicles. Surrounding (Peri) each fascicle is a
layer of fibrous connective tissue called permysium.
Endomysium-(within
the muscle)- a sheath of CT that surrounds each
individule muscle fiber. Consists of fine areolar tissue.
Masseter:
What is the
orgin? What is the Insertion?
Orgin-Zygomatic arch and zygomatic bone.
Insertion-angle and ramus of mandible.
Digastric:
What is the
orgin? What is the function?
Orgin- lower margin of mandible and mastoid process of temporal
bone. Insertion- by a conective tissue loop to hyoid
bone.
Sternohyoid:
What is the
orgin? What is the insertion?
Orgin-manubrium and medial end of clavicle Insertion-
lower margin of hyoid bone.
Sternothyroid:
What is the
orgin? What is the insertion?
Orgin- posterior surface of manubrium of sternum.
Insertion- thyroid cartilage.
Sternocleidomastoid:
What is the Orgin? what is the insertion?
Orgin- Manubrium of sternum and medial portion of clavicle
Insertion- Mastoid process of temporal bone and superior nuchal
line of occipital bone.
Scalenes:
What is the
orgin? What is the insertion?
Orgin- transverse processes of cervical vertebrae
Insertion-anterolaterally on first two ribs.