1. Biology 322 Human Anatomy I
Histology of Muscle

2. Muscle Tissue: 3 Types:
Skeletal Muscle
Cardiac Muscle
Smooth Muscle

3. Muscle Muscle Muscle Myocytes Nuclei Striations
Skeletal Cardiac Smooth
Muscle Muscle Muscle
Very long
Unbranched
Shorter
Branched
Short
Spindle-shaped
Hundreds per cell
Peripheral
One or two per cell
Central
One per cell
Yes No
Myocytes
Nuclei
Striations

4. Muscle: Special Terminology:
Prefixes =
Cell =
Plasma membrane =
Endoplasmic reticulum =
Cytoskeletal Filaments =

5. 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

6. 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.

8. Myocyte (muscle cell)
Myofibril
Thick & thin myofilaments

11. Thick and thin myofilaments forming part of a myofibril

13. Skeletal Muscle Anatomy:
Each myocyte surrounded by, and firmly attached to, layer of loose connective tissue called

14. Skeletal Muscle Anatomy:
Myocytes grouped together into bundles called each fascicle surrounded by, and firmly attached to, layer of dense irregular connective tissue called

15. Skeletal Muscle Anatomy:
Entire muscle surrounded by, and firmly attached to, layer of dense irregular connective tissue called

16. 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.

17. Skeletal myocytes = VOLUNTARY Can only contract when stimulated by motor neuron
Myoneural junction or
Neuromuscular junction

18. One motor neuron +
All myocytes it
innervates =

19. 1. Myocytes and muscles always pull (exert force by
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"

20. 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