Download Histology of Muscle

Biology 322
Human Anatomy I
Histology of Muscle
Muscle Tissue: 3 Types:
Skeletal Muscle
Cardiac Muscle
Smooth Muscle
Skeletal
Muscle
Very long
Myocytes Unbranched
Nuclei
Striations
Cardiac
Muscle
Smooth
Muscle
Shorter
Branched
Short
Unbranched
Spindle-shaped
Hundreds per cell
Peripheral
One or two per
cell
Central
One per cell
Central
Yes
Yes
No
Muscle: Special Terminology:
Prefixes =
Cell =
Plasma membrane =
Endoplasmic reticulum =
Cytoskeletal Filaments =
Skeletal Muscle:
Always voluntary.
Each myocyte connected
to and controlled by an
axon from a motor neuron.
Because of high metabolism, myocytes must be very
close to capillaries.
Myocytes are all oriented parallel to long axis of muscle
which is
Parallel to direction which muscle pulls when it contracts
&
lengthens when it relaxes
Prominent Organelles in Myocytes:
- Sarcolemma
- Nuclei
- Myofibrils (highly organized bundles of myofilaments
- Transverse tubules (inward extensions of sarcolemma)
- Sarcoplasmic reticulum
- Mitochondria
Keep in mind: Even though not prominent, all other
organelles also present
(vesicles, ribosomes, lysosomes,
Golgi apparatus, etc.
Myocyte (muscle cell)
Myofibril
Thick & thin
myofilaments
Thick and thin myofilaments forming part of a myofibril
Skeletal Muscle Anatomy:
Each myocyte surrounded by, and firmly attached to,
layer of loose connective tissue called
Skeletal Muscle Anatomy:
Myocytes grouped together into bundles called
each fascicle surrounded by, and firmly attached to, layer
of dense irregular connective tissue called
Skeletal Muscle Anatomy:
Entire muscle surrounded by, and firmly attached to, layer
of dense irregular connective tissue called
Skeletal Muscle Anatomy:
All three layers of connective tissue blend together at
each end of muscle. Thus force transmitted from:
Myocytes
Endomysium
Perimysium
Epimysium
Tendon, bone,
etc.
Skeletal myocytes = VOLUNTARY
Can only contract when stimulated
by motor neuron
Myoneural junction or
Neuromuscular junction
One motor neuron
+
All myocytes it
innervates
=
Skeletal Muscle:
1. Myocytes and muscles always pull (exert force by
contraction), they never push. They usually, although
not always, pull on bone through a tendon.
2. If a sarcomere shortens, it always does so completely
"All-or-none"
3. All of the sarcomeres in the entire myocyte shorten at
the same time. "All-or-none"
But:
4. All of the myocytes in a muscle don't always contract at
the same time. No "all-or-none"
Skeletal Muscle:
The total force produced by a myocyte is equal to the sum
of the forces produced by individual sarcomeres.
Thus: More sarcomeres = more force
The total force produced by a muscle is equal to the sum
of the forces produced by individual sarcomeres.
Thus: More myocytes = more force