1. Biology 322 Human Anatomy I
Muscle Histology

2. Muscle Tissue: 3 Types:
Skeletal Muscle
Cardiac Muscle
Smooth Muscle
Voluntary
Striated
Involuntary
Nonstriated

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. We have learned the names, locations, origins, and insertions of skeletal muscles (organs) in lab.
We will now discuss the cytology (cells) & histology (tissues) of skeletal muscle, then do a brief review of their shapes, sizes, and functions in different regions of the human body.
We will discuss cardiac muscle when we discuss the heart, and we will discuss smooth muscle when we discuss the circulatory, digestive, and other systems where it is located.

5. Muscle: Special Terminology:
Prefixes =
Cell =
Plasma membrane =
Endoplasmic reticulum =
Cytoskeletal Filaments =
Myo- / Sarco-
Myocyte ("Fiber")
Sarcolemma
Sarcoplasmic reticulum
Myofilaments

6. Skeletal Muscle: Always voluntary: Each myocyte is
connected to and controlled by an axon
from a motor neuron.
High metabolism
Myocytes 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

8. Muscle
Myocyte
Myofibril
Myofilaments

11. Thick and thin myofilaments forming part of a myofibril
Z-line
Sarcomere

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

15. Skeletal Muscle Anatomy:
Myocytes grouped together into bundles called fascicles. Each fascicle surrounded by, and firmly attached to, layer of dense irregular connective tissue called perimysium
Perimysium

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

17. 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.

18. One motor neuron +
All myocytes it
innervates =
one Motor Unit

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

20. 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"

21. 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