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2. Chapter 10 Muscular Tissue
Lecture slides prepared by Curtis DeFriez, Weber State University

3. Functions of Muscular Tissue
Like nervous tissue, muscles are excitable or "irritable”
they have the ability to respond to a stimulus
Unlike nerves, however, muscles are also:
Contractible (they can shorten
in length)
Extensible (they can extend or
stretch)
Elastic (they can return to their
original shape)

4. Functions of Muscular Tissue
Muscle makes up a large percentage of the body’s weight
Their main functions are to:
Create motion – muscles work with nerves, bones, and joints to produce body movements
Stabilize body positions and maintain posture
Store substances within the body using sphincters
Move substances by peristaltic contractions
Generate heat through thermogenesis

5. Three Types of Muscular Tissue
Location
Function
Appearance
Control
Skeletal
skeleton
movement, heat, posture
striated, multi-nucleated (eccentric), fibers parallel
voluntary
Cardiac
heart
pump blood continuously
striated, one central nucleus
involuntary
Visceral
(smooth muscle)
G.I. tract, uterus, eye, blood vessels
Peristalsis, blood pressure, pupil size, erects hairs
no striations, one central nucleus

6. Three Types of Muscular Tissue
(a) Skeletal muscle
(b) Cardiac muscle
(c) Visceral smooth muscle

7. Skeletal Muscle Location Function Appearance Control Skeletal skeleton
movement, heat, posture
striated, multi-nucleated (eccentric), fibers parallel
voluntary
Cardiac
heart
pump blood continuously
striated, one central nucleus
involuntary
Visceral
(smooth muscle)
G.I. tract, uterus, eye, blood vessels
Peristalsis, blood pressure, pupil size, erects hairs
no striations, one central nucleus

8. Skeletal Muscle
All muscle start as these spindly shaped cells from myoblasts – skeletal muscle cells fuse to form large fibers…
Satellite cells are small mononuclear progenitor cells with virtually no cytoplasm found in mature muscle. They are found sandwiched between the basement membrane and sarcolemma (cell membrane) of individual muscle fibres, and can be difficult to distinguish from the sub-sarcolemmal nuclei of the fibres. Satellite cells are able to differentiate and fuse to augment existing muscle fibres and to form new fibres. These cells represent the oldest known adult stem cell niche, and are involved in the normal growth of muscle, as well as regeneration following injury or disease.

9. A single skeletal muscle fiber
Skeletal muscle fibers are very long “cells” - next to neurons (which can be over a meter long),
perhaps the longest in the body
The Sartorious muscle contains
single fibers that are at least
30 cm long
It’s difficult to find the sartorius muscle in some people (cadavers)
A single skeletal muscle fiber

10. Skeletal Muscle
The terminal processes of a motor neuron in close proximity to the sarcolemma of a skeletal muscle fiber
Motor neuron
Sarcolemma

11. Organization of Muscle Tissue
The epimysium, perimysium, and
endomysium all are continuous with
the connective tissues that form
tendons and ligaments (attach
skeletal muscle to bone) and muscle
fascia (connect muscles to other
muscles to form groups of muscles)

12. Organization of Muscle Tissue
Epimysium
Perimysium
These next few graphics show connective tissue elements associated with skeletal muscle: Starting with whole muscles and working our way down to fascicles and individual muscle cells (fibers).
Organization of a single muscle belly

13. Organization of Muscle Tissue
Organization of a fasciculus

14. Organization of Muscle Tissue
Organization of a muscle fiber

15. Organization of Muscle Tissue
A muscle, a fasciculus, and a fiber all visualized

16. Organization of Muscle Tissue
In groups of muscles the epimysium continues to become thicker, forming fascia which covers many muscles
This graphic shows the fascia lata enveloping the entire group of quadriceps and hamstring muscles in the thing

17. Organization of Muscle Tissue
Many large muscle groups are encased in both a superficial
and a deep fascia
Real Anatomy, John Wiley and Sons

18. Organization of Muscle Tissue
An aponeurosis is
essentially a thick
fascia that connects two muscle bellies. This epicranial aponeurosis connects the muscle bellies of the occipitalis and the frontalis to form “one” muscle: The occipitofrontalis
Epicranial aponeurosis
Frontal belly of the occipitofrontalis m.
An aponeurosis is essentially a thick fascia that connects two muscle bellies. This epicranial aponeurosis connects the muscle bellies of the occipitalis and the frontalis to form “one” muscle: The occipitofrontalis

19. Organization of Muscle Tissue
Veins, arteries, and nerves are located in the deep fascia between muscles of the thigh.

20. The Skeletal Muscle Fiber
Beneath the connective tissue endomysium is found the plasma membrane (called the sarcolemma) of an individual skeletal muscle fiber
The cytoplasm (sarcoplasm) of skeletal muscle fibers is chocked full of
contractile proteins
arranged in myofibrils

21. The Skeletal Muscle Fiber
You should learn the names of the internal structures of the muscle fiber
Sarcolemma
Sarcoplasm
Myofibril
T-tubules
Triad (with
terminal cisterns
Sarcoplasmic reticulum
Sarcomere

22. The Skeletal Muscle Fiber
Increasing the level of magnification, the myofibrils are seen to be composed
of filaments
Thick filaments
Thing filaments
Sarcomeres are multi-protein complexes composed of three different filament systems. The thick filament system is composed of myosin protein which is connected from the M-line to the Z-disc by titin. It also contains myosin-binding protein C which binds at one end to the thick filament and the other to actin.
The thin filaments are assembled by actin monomers bound to nebulin, which also involves tropomyosin (a dimer which coils itself around the F-actin core of the thin filament) and troponin.
Nebulin and titin give stability and structure to the sarcomere.

23. The Skeletal Muscle Fiber
The basic functional unit of skeletal muscle fibers is the sarcomere: An arrangement of thick and thin filaments sandwiched between two Z discs
A scanning electron micrograph of a sarcomere
Z-line (from the German "Zwischenscheibe“). Each myofibril is made up of thin filament proteins and thick filament proteins, arranged (configured) in sarcomeres.

24. The Skeletal Muscle Fiber
Muscle contraction occurs in the sarcomeres
Each myofibril is made up of thin filament proteins, and thick filament proteins, arranged (configured) in sarcomeres
The “Z line” is really a Z disc when considered in 3 dimensions. A sarcomere extends from Z disc to Z disc.

25. Muscle Proteins Myofibrils are built from three groups of proteins
Contractile proteins generate force during contraction
Regulatory proteins help switch the contraction process on and off
Structural proteins keep the thick and thin filaments in proper alignment and link the myofibrils to the sarcolemma and extracellular matrix

26. Muscle Proteins
The thin filaments are comprised mostly of the structural protein actin, and the thick filaments are comprised mostly of the structural protein myosin
However, in both types of filaments, there are also other structural and regulatory proteins