Kaan Yücel M.D., Ph.D .
12.March.2013 Tuesday
 The muscular system consists of all the muscles of the body.
 The discipline related to the study of muscles is myology.
 Musculus (muscle) is derived from the word mus-mouse; musculuslittle mouse.
So called because the shape and movement of some muscles (notably biceps) were
thought to resemble mice.
If you bend and straighten your arm at the elbow, you should see the front of the upper
arm move under the skin. To the ancient Romans this movement resembled a little
mouse scurrying beneath the skin.
 All skeletal muscles are composed of one specific type of muscle
tissue.
 These muscles move the skeleton, therefore, move the body parts.
Types of Muscles
based on distinct characteristics
Functional
voluntary vs. involuntary
Histological
striated vs. smooth or unstriated
Anatomical (location)
@ body wall (soma) and limbs
@ hollow organs (viscera) or blood vessels
Skeletal striated muscle
voluntary somatic muscle
gross skeletal muscles that compose the muscular system
moving or stabilizing bones and other structures (e.g., the eyeballs).
Innervated by the somatic nervous system.
Cardiac striated muscle
involuntary visceral muscle
forms the walls of the heart and adjacent parts of the great vessels.
pumps blood.
Smooth muscle (unstriated muscle)
involuntary visceral muscle
forms part of the walls of most vessels and hollow organs (viscera)
moving substances through them
coordinated sequential contractions (pulsations or peristaltic contractions).
Innervated by the autonomic nervous system.
FEATURES OF SKELETAL MUSCLES
HEAD OR BELLY fleshy, reddish, contractile portions
TENDON white non-contractile portions
composed mainly of organized collagen bundles, that provide a means of attachment.
Most skeletal muscles attach to
Directly or indirectly to bones
Cartilages
Ligaments
Fascias
or combinations of the ones above
Some to organs (eyeball)/skin (facial muscles)/mucous membranes(intrinsic tongue muscles
Muscles are organs of locomotion (movement)
also:
provide static support
give form to the body
provide heat
Some tendons form flat sheets aponeuroses
anchor the muscle
to the skeleton
to deep fascia
to aponeurosis of another muscle
Many terms provide information about a structure's
Shape
Size
Location
Function
Resemblance of one structure to another
Basis of function
Bones attached to
Abductor digiti minimi muscle abducts the little finger.
Sternocleidomastoid muscle (G. kleidos, bolt or bar, clavicle)
attaches inferiorly to the sternum and clavicle and superiorly to the
mastoid process of the temporal bone of the cranium.
Levator scapulae elevates the scapula (L. shoulder blade).
Descriptive names
Deltoid muscle
triangular, like the symbol for delta, the fourth letter of the Greek
alphabet.
-oid “like”;
deltoid means like delta.
Position
medial, lateral, anterior, posterior
Length
brevis, short; longus, long
Shape
piriformis muscle
pear shaped (L. pirum, pear + L. forma, shape or form).
Location
temporalis muscle
in the temporal region (temple) of the cranium (skull).
according to their shapes
Flat muscles
parallel fibers often with an aponeurosis
External oblique muscle
broad flat muscle
Sartorius
narrow flat muscle with parallel fibers
longest muscle in the body
Pennate muscles
feather-like (L. pennatus, feather), arrangement of fasicles
Unipennate
Extensor
digitorum
longus
Bipennate
Rectus
femoris
Multi-pennate
Deltoid
Fusiform muscles
spindle shaped with a round, thick belly (or bellies) and tapered ends
Convergent muscles
arise from a broad area
converge to form a single tendon
Quadrate muscles
four equal sides (L. quadratus, square)
rectus abdominis
between its tendinous intersections.
Circular or sphincteral muscles
surround a body opening or orifice, constricting it when contracted
orbicularis oculi closes the eyelids
Multi-headed or multi-bellied muscles
more than one head of attachment or more than one contractile belly
Biceps muscles
two heads of attachment
triceps muscles
three heads
Two bellies
digastric muscle
gastrocnemius muscle
Skeletal muscles function by contracting
they pull and never push.
When a muscle contracts and shortens
one of its attachments usually remains fixed
the other attachment (more mobile) pulled toward it
movement
Attachments of muscles
origin & insertion
Origin proximal end of the muscle
remains fixed during muscular contraction.
Insertion distal end of the muscle
movable
This is not always the case.
Some muscles can act in both directions under different
circumstances.
Whereas the structural unit of a muscle is a skeletal striated muscle
fiber, the functional unit of a muscle is a motor unit, consisting of a
motor neuron and the muscle fibers it controls.
When a motor neuron in the spinal cord is stimulated, it initiates an
impulse that causes all the muscle fibers supplied by that motor unit
to contract simultaneously.
 The number of muscle fibers in a motor unit varies from one to
several hundred. The number of fibers varies according to the size
and function of the muscle.
 Large motor units, in which one neuron supplies several hundred
muscle fibers, are in the large trunk and thigh muscles.
 Movement (phasic contraction) results from the activation of an
increasing number of motor units, above the level required to
maintain muscle tone.
Functions of muscles
Prime mover (agonist)
main muscle responsible for producing a specific movement of the body.
Does most of the work (expending most of the energy) required.
In most movements, there is a single prime mover, but some movements involve two prime
movers working in equal measure.
Fixator
steadies the proximal parts of a limb through isometric contraction
while movements are occurring in distal parts.
Synergist
complements the action of a prime mover.
Usual to have several synergists assisting a prime mover in a particular movement.
Antagonist
a muscle that opposes the action of another muscle.
A primary antagonist directly opposes the prime mover,
synergists may also be opposed by secondary antagonists.
The same muscle may act as a prime mover, antagonist, synergist, or
fixator under different conditions.
Nerves and arteries to muscles
 Variation in the nerve supply of muscles is rare; it is a nearly constant
relationship.
 In the limb, muscles of similar actions are generally contained within
a common fascial compartment and share innervation by the same
nerves.
Fascia (L. fasciae)
wrapping, packing, and insulating materials of the deep structures of the body
Underlying the subcutaneous tissue superficial fascia
Deep fascia
dense, organized connective tissue layer, devoid of fat
covers most of the body deep to the skin and subcutaneous tissue
In the limbs, groups of muscles with similar functions sharing the same
nerve supply are located in fascial compartments, separated by thick
sheets of deep fascia, called intermuscular septa, that extend centrally
from the surrounding fascial sleeve to attach to bones.
These compartments may contain or direct the spread of an infection or
a tumor.
Muscles of the Face and the Scalp
The facial muscles (muscles of facial expression) move the skin
and change facial expressions to convey mood.
Most muscles attach to bone or fascia and produce their effects by
pulling the skin.
The occipitofrontalis is a flat digastric muscle which elevates the
eyebrows and produce transverse wrinkles across the forehead.
This gives the face a surprised look.
The shape of the mouth and lips is controlled by a complex threedimensional group of muscular slips, which include the following:
 Elevators, retractors, and evertors of the upper lip.
 Depressors, retractors, and evertors of the lower lip.
 The orbicularis oris, the sphincter around the mouth.
 The buccinator in the cheek
The platysma (G. flat plate) is a broad, thin sheet of muscle in the
subcutaneous tissue of the neck. It helps depress the mandible and
draw the corners of the mouth inferiorly.
The orbicularis oculi closes the eyelids and wrinkles the forehead
vertically.
The muscles of the nose may provide evidence of breathing
behaviors.
Cutaneous (sensory) innervation of the face and
anterosuperior part of the scalp is provided primarily by the
trigeminal nerve (CN V).
Motor innervation to the facial muscles is provided by the
facial nerve (CN VII).
Sternocleidomastoid (SCM) muscle
broad, strap-like muscle with two heads
One head attaches to the sternum
One head attaches to clavicle.
Bilateral contractions extension of the elevating the chin
Unilateral contraction laterally flexes the neck
Trapezius muscle
large, flat triangular muscle
Covers the posterior aspect of the neck & superior half of the trunk
A direct attachment of the pectoral girdle to the trunk.
A ssists in suspending the upper limb.
4 anterior axioappendicular muscles (pectoral muscles) move the
pectoral girdle.
Pectoralis major is the biggest of these four.
powerful adduction and
medial rotation of the arm
Posterior shoulder muscles
Superficial extrinsic shoulder muscles
trapezius and latissimus dorsi
Deep extrinsic shoulder muscles
two muscles
Intrinsic shoulder muscles
deltoid, teres major, four rotator cuff muscles
latissimus dorsi (L. widest of back)
passes from the trunk to the humerus and acts directly on the
shoulder joint and indirectly on the pectoral girdle.
extends, retracts, and rotates the humerus medially
when folding the arms behind the back or scratching the skin over the opposite scapula
Deltoid
thick, powerful, coarse-textured muscle covering the shoulder
forms its rounded contour.
As its name indicates, the deltoid is shaped like the inverted Greek
letter delta (Δ).
Muscles of the Arm & the Hand
Of the four major arm muscles:
three flexors (biceps brachii, brachialis, and coracobrachialis)
in the anterior (flexor) compartment
supplied by the musculocutaneous nerve
one extensor (triceps brachii)
in the posterior compartment, supplied by the radial nerve.
 The biceps brachii is the flexor of the arm.
 The brachialis is the main flexor of the forearm.
 The triceps brachii is the main extensor of the forearm.
flexor muscles of the forearm
anterior (flexor-pronator) compartment of the forearm
extensor muscles of the forearm
posterior (extensor-supinator) compartment of the forearm,
innervated by branches of the radial nerve.
Muscles of the Gluteal Region, Back,
Leg & the Foot
gluteus maximus
largest, heaviest, and most coarsely fibered muscle of the body.
most superficial gluteal muscle
extension and lateral rotation of the thigh
anterior thigh muscles
flexors of the hip and extensors of the knee.
sartorius, the “tailor's muscle”
longest muscle in the body.
quadriceps femoris (L., four-headed femoral muscle)
It covers almost all the anterior aspect and sides of the femur.
extensor of the leg.
The posterior thigh muscles include the hamstring muscles: (1)
semitendinosus, (2) semimembranosus, and (3) biceps femoris (long
head).
Four muscles in the anterior compartment of the leg
dorsiflexors of the ankle joint, elevating the forefoot and depressing the heel
lateral compartment of the leg
smallest (narrowest) of the leg compartments
fibularis longus and brevis muscles
Evertors of the foot
Posterior compartment of the leg
plantarflexor compartment
is largest of the three leg compartments
inversion of the foot
superficial group of calf muscles
gastrocnemius, soleus, and plantaris.
gastrocnemius and soleus share a common tendon
calcaneal tendon (L. tendo calcaneus, Achilles tendon)
most powerful (thickest and strongest) tendon in the body.
triceps surae (L. sura, calf).
raise heel during walking; flex the leg at the knee joint.
6 abdominal muscles
transverse abdominal
internal obliques
external obliques
rectus abdominis