2. Muscular Tissue
Muscle tissue is composed of cells which have the
ability to contract (shorten) and relax (lengthen).
Muscle tissue is highly vascular zed and dense
tissue.
Muscle tissue can not regenerate itself once it has
been destroyed.
Muscle cells are called muscle fibers.
There are three types of muscle tissues:
a. Striated or skeletal muscle
b. Cardiac muscle or myocardial tissue
c. Smooth or visceral muscle
3. Muscular Tissue Types
Striated or skeletal muscle: This muscle is composed of
long, cylindrical, parallel fibers.
There are bands or striations present which run across the
width of the fiber. These fibers are multinucleated (more
than one nucleus present per cell).
This type of muscle tissue is under conscious or voluntary
control.
This muscle has the greatest strength of contraction but
tires most rapidly. It functions are locomotion and facial
expressions.
4. Muscular Tissue Types
Cardiac muscle: Cardiac muscle fibers are branched at the end
with striations present, usually only one nucleus is present per
cell.
The branches of each fiber come into contact at specialized
junctions called intercalated discs.
It is involuntarily controlled by the autonomic nervous system
and hormones. Its contractions are short, but the muscle fibers
are constantly contracting.
Its function is to create the pump which propels the blood
throughout the body.
5. Muscular Tissue Types
Smooth or visceral muscle: These cells are spindle-shaped
(tapered on the ends) and lack striations.
They have one nucleus present. They produce weaker
contractions, however they contract for extended periods of
time.
They are involuntarily controlled by the autonomic nervous
system or hormones.
They are found in the digestive organs, arteries and veins,
the trachea and bronchiole tubes, and the urogenital tract.
Their contractions propels or moves substances or objects
from one location to another.
6. Functions of muscle tissue
Movement
Maintenance of
posture
Joint stabilization
Heat generation
7. Special functional characteristics of muscle
Contractility
Only one action: to shorten
Shortening generates pulling force
Excitability
Nerve fibers cause electrical impulse to travel
Extensibility
Stretch with contraction of an opposing muscle
Elasticity
Recoils passively after being stretched
8. Types of Muscle Tissue
Skeletal
•Attach to and move skeleton
•40% of body weight
•Fibers = multinucleate cells (embryonic cells fuse)
•Cells with obvious striations
•Contractions are voluntary
Cardiac: only in the wall of
the heart
•Cells are striated
•Contractions are
involuntary (not
voluntary)
Smooth: walls of hollow organs
•Lack striations
•Contractions are involuntary (not voluntary)
9. Similarities…
Their cells are called fibers because they are elongated
Contraction depends on myofilaments
Actin
Myosin
Plasma membrane is called sarcolemma
Sarcos = flesh
Lemma = sheath
10. Skeletal muscle
Epimysium:
surrounds
whole muscle
Perimysium
Endomysium is around each
is around
muscle fiber
fascicle
11. Each muscle: one nerve, one artery,
one vein Skeletal Muscle
Branch repeatedly
Attachments
One bone to another
Cross at least one movable joint
Origin: the less movable attachment
Insertion: is pulled toward the origin
Usually one bone moves while the
other remains fixed
In muscles of the limb, origin lies
proximal to the insertion (by
convention)
Note: origin and insertion may switch
depending on body position and
movement produced
12. Attachments continued
Many muscles span two or more joints
Called biarticular or multijoint muscles
Cause movements at two joints
Direct or “fleshy” attachments
Attachments so short that muscle appears to attach directly
to bone
Indirect: connective tissue extends well beyond the
muscle (more common)
Tendon: cordlike (most muscles have tendons)
Aponeurosis: flat sheet
Raised bone markings where tendons meet bones
Tubercles, trochanters, crests, etc.
13. Some sites showing animations
of muscle contraction
http://entochem.tamu.edu/MuscleStrucContractswf/i
ndex.html
http://www.brookscole.com/chemistry_d/templates/s
tudent_resources/shared_resources/animations/musc
les/muscles.html
14. Skeletal muscle
Fibers (each is one
cell) have striations
Myofibrils are
organelles of the cell: This big
these are made up of cylinder is a
-an organelle
fiber: 1 cell
filaments
Sarcomere
Basic unit of contraction
Myofibrils are long
rows of repeating
sarcomeres
Boundaries: Z discs (or
lines)
15. Myofibrils
Made of three types of filaments (or myofilaments):
Thick (myosin)
Thin (actin)
Elastic (titin)
______actin
_____________myosin
titin_____
16. Sliding Filament Model
__relaxed sarcomere__ _partly contracted_
fully contracted
Sarcomere “A” band constant
shortens because because it is
actin pulled caused by
towards its middle myosin, which
by myosin cross doesn’t change
bridges length
Titin resists overstretching
19. Sarcoplasmic reticulum is smooth ER
Tubules surround myofibrils
Cross-channels called “terminal cisternae”
Store Ca++ and release when muscle stimulated to contract
To thin filaments triggering sliding filament mechanism of
contraction
T tubules are continuous with sarcolemma, therefore whole
muscle (deep parts as well) contracts simultaneously
20. Neuromuscular Junction
Motor neurons innervate muscle
fibers
Motor end plate is where they
meet
Neurotransmitters are released
by nerve signal: this initiates
calcium ion release and muscle
contraction
Motor Unit: a motor neuron and all the muscle fibers it innervates (these all
contract together)
•Average is 150, but range is four to several hundred muscle fibers in a motor
unit
•The finer movement, the fewer muscle fibers /motor unit
•The fibers are spread throughout the muscle, so stimulation of a single motor
unit causes a weak contraction of the entire muscle
21.
22.
23. Types of skeletal muscle fibers
Fast, slow and intermediate
Whether or not they predominantly use oxygen to produce
ATP (the energy molecule used in muscle contraction)
Oxidative – aerobic (use oxygen)
Glycolytic – make ATP by glycolysis (break down of sugars without
oxygen=anaerobic)
Fast fibers: “white fibers” – large, predominantly anaerobic,
fatigue rapidly (rely on glycogen reserves); most of the skeletal
muscle fibers are fast
Slow fibers: “red fibers” – half the diameter, 3X slower, but can
continue contracting; aerobic, more mitochondria, myoglobin
Intermediate: in between
24. A skeletal muscle contracts when its motor
units are stimulated
Amount of tension depends on
1. the frequency of stimulation
2. the number of motor units involved
Single, momentary contraction is called a muscle
twitch
All or none principle: each muscle fiber either
contracts completely or not at all
Amount of force: depends on how many motor
units are activated
Muscle tone
Even at rest, some motor units are active: tense the
muscle even though not causing movement: “resting
tone”
25. Muscle hypertrophy
Weight training (repeated intense workouts): increases
diameter and strength of “fast” muscle fibers by increasing
production of
Mitochondria
Actin and myosin protein
Myofilaments containing these contractile proteins
The myofibril organelles these myofilaments form
Fibers enlarge (hypertrophy) as number and size of
myofibrils increase
[Muscle fibers (=muscle cells) don’t increase in number but
increase in diameter producing large muscles]
Endurance training (aerobic): doesn’t produce hypertrophy
Muscle atrophy: loss of tone and mass from lack of stimulation
Muscle becomes smaller and weaker
Note on terminology: in general, increased size is hypertrophy; increased number of
cells is hyperplasia
26. Tendon Anatomy
Very strong, stronger than muscle for size
As strong as bone with a failing point similar to steel!
Can transmit force through ability to glide
Passive component of the musculotendinous unit in
light of their incredible influence on the foot.
Tendon Histology
30% Collagen, 2% Elastin,
68% Water
Bulk is supplied by reticulin
70% Type I collagen
27. Ligament Histology
33% Composition: 90% Type I
collagen,
Elastin, Glycosaminoglycans.
67% Water
28. Anatomy of the Tendon
Tropocollagen – the most basic molecular unit of
tendon
3 Coverings:
Endotenon- fascicles are surrounded by this areolar
CT, contains BV, L, N, and FB.
Epitenon- Fascicles bound together by this 1-2 cell
fibroblastic & synovial layer
Paratenon- loose areolar layer continuous with the
epitenon & perimysium, straight.
29. Anatomy of the Tendon
Tendon/Synovial Sheath: acts like a pulley when
tendon has an angled course.
Peritenon- term applied collectively to all CT
structures associated with a tendon incl para-, meso-
, epi-, and endotenon.
32. Tendon Circulation
3 Sources:
a) Small amount from the central blood vessels
originating in the muscle.
b) Some from vessels of the bone and periosteum
near the tendon’s insertion.
c) Majority comes from small vessels in the
paratenon or through the mesotenon. If absent
then carried thru the vincula. Synovial fluid also
nourishes the tendon.
34. Tendon Innervation
Afferent supply only
Source in musculotendinous
junction and external local
nerves.
Golgi tendon organs: monitor
increases in tension rather than
length.
35. Tendon Attachment to Bone
Attach at 90° angles to bone
in 4 layers:
1. Tendon collagen fibers
2. Fibrocartilage
3. Bone
4. Sharpey’s fibers – originate
in bone and end in
perisoteum.
