The document is an anatomy lecture on muscular tissue delivered at Kilimanjaro Christian Medical University College, highlighting the types, structures, and functions of skeletal, cardiac, and smooth muscle tissues. It discusses muscle characteristics, including contractility and elasticity, along with the types of muscle fibers and their physiological properties. Additionally, it addresses muscle disorders, developmental aspects, and the impact of aging on muscle tissue.

1. KILIMANJARO CHRISTIAN MMEDICAL
UNIVERSITY COLLEGE
Faculty of Rehabilitation Medicine
Department of Anatomy and Neuroscience
Anatomy Lecture for BSc.Nursing and BSc.Physiotherapy
LECTURE 6 & 7
TOPIC: MUSCULAR (CONTRACTILE) TISSUE
Date: Nov. 11th 2022, from 1:30 am -3:30pm, GYM – Physiotherapy School
Lecturer: J. S. Kauki, BSc, MSc, on PhD, Email: jskauki@gmail.com.
Office ext. 70 Block C, 3RD Floor, Anatomy dept.

2. Objective
 Describe the general features of muscular
tissue.
 Compare the structure, location, and
mode of control of skeletal, cardiac, and
smooth muscle tissue.

3. Introduction
 Muscular tissue consists of elongated cells called muscle fibers
or myocytes that can use ATP to generate force.
 As a result, muscular tissue produces body movements,
maintains posture, and generates heat.
 It also provides protection.
 Based on its location and certain structural and functional
features, muscular tissue is classified into three types: skeletal,
cardiac, and smooth

4. Functions of muscle tissue
Movement
Maintenance of posture
Joint stabilization
Heat generation
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

5. 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)

6. Similarities…
 Their cells are called fibers because they are elongated
 Contraction depends on myofilaments
 Actin
 Myosin / Desmin (smooth muscles)
 Plasma membrane is called sarcolemma
 Sarcos = flesh
 Lemma = sheath

7. Skeletal Muscle
 Each muscle is an organ
 Consists mostly of muscle tissue
 Skeletal muscle also contains
 Connective tissue
 Blood vessels
 Nerves
 Plasma membrane is called a sarcolemma
 Cytoplasm is called sarcoplasm

8. Skeletal muscle
 Connective tissue and fascicles
Connective tissue sheaths
bind a skeletal muscle and its
fibers together
 Epimysium – dense regular
connective tissue surrounding
entire muscle
 Perimysium – surrounds each
fascicle
(group of muscle fiber
 Endomysium – a fine sheath
of connective tissue wrapping
each muscle cell
 Nerves and blood vessels
 Each skeletal muscle supplied by
branches of
 One nerve
 One artery
 One or more veins

9. Skeletal muscle
Epimysium:
surrounds
whole muscle
Perimysium
is around
fascicle
Endomysium is around each
muscle fiber

10. Attachments
 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.

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Formation of Muscle fibre

14. Skeletal muscle
 Fibers (each is one cell) have
striations
 Myofibrils are organelles of the
cell: these are made up of
filaments
 Sarcomere
 Basic unit of contraction
 Myofibrils are long rows of
repeating sarcomeres
 Boundaries: Z discs (or
lines)
This big
cylinder is a
fiber: 1 cell -an organelle
 Basic unit of contraction of skeletal
muscle
 Z disc (Z line) – boundaries of each
sarcomere
 Thin (actin) filaments – extend
from Z disc toward the center of the
sarcomere
 Thick (myosin) filaments – located
in the center of the sarcomere

15.  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

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Myofibrils  Made of three types of filaments
(or myofilaments):
 Thick (myosin)
 Thin (actin)
 Elastic (titin)

18. Sliding Filament Model
__relaxed sarcomere__ _partly contracted_
fully contracted
“A” band constant
because it is
caused by myosin,
which doesn’t
change length
Sarcomere shortens
because actin pulled
towards its middle
by myosin cross
bridges
Titin resists overstretching

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 the 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

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Neuromuscular junction

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

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 A) staining for
ATPase at Ph 4.2.
Type 1 fibers dark,
type 2 fibers light.
 B) Stainig to
demonstrate NADH
transferase. Type 1
dark stained, type 2
light stained.

25. NOTE
 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”

26.  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

27. Cardiac muscle
 Bundles form thick
myocardium
 Cardiac muscle cells are single
cells (not called fibers)
 Cells branch
 Cells join at intercalated discs
 1-2 nuclei in center
 Here “fiber” = long row of
joined cardiac muscle cells
 Inherent rhythmicity: each
cell! (muscle cells beat
separately without any
stimulation)
Intercalated
disc__________

28. Smooth muscle
•Muscles are spindle-shaped cells
•One central nucleus
•Grouped into sheets: often running
perpendicular to each other
•Peristalsis
•No striations (no sarcomeres)
•Contractions are slow, sustained and
resistant to fatigue
•Does not always require a nervous signal:
can be stimulated by stretching or hormones
6 major locations:
1. inside the eye 2. walls of vessels 3. respiratory tubes
4. digestive tubes 5. urinary organs 6. reproductive organs

32.  Muscle tissues experience few disorders
 Heart muscle is the exception
 Skeletal muscle
 Remarkably resistant to infection
 Smooth muscle
 Problems stem from external irritants
 READ: Disorders of muscle Tissue,at least
three.

33. Muscle Tissue Through life
 Muscle tissue develops from myoblasts
Skeletal muscles contract by the seventh
week of development.
 Cardiac muscle
 Pumps blood from three weeks after
fertilization
 With increased age
 Amount of connective tissue increases in
muscles
 Number of muscle fibers decreases
 Loss of muscle mass with aging
 Decrease in muscular strength by 50% by
age 80
 Sarcopenia – muscle wasting

34. Take home Assignment
Read about the following Muscle Disorders
1. Myopathies eg Polymyositis, Dermatomyositis, Duchenne Muscular
Dystrophy, Steroid induced myopathy
2. Cramp: prolong painful involuntary contraction of skeletal muscles
3. Fibrositis: Inflammation of fibrous connective tissues in muscles.it also
effect muscles of trunk and back.
4. Myasthenia Gravis
5. Rhabdomyolysis
6. Cardiac Myopathy: Coronary Artery Disease
7. Amyotrophic Lateral Sclerosis
8. Sarcopenia: This muscle disease can be primary or secondary.
Sarcopenia causes muscle mass loss and muscle strength

35. Questions?

36. THANK YOU FOR YOUR ATTENTION