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Chapter 7
Muscular system
VTHT 1205
ROOTS
• ARTHR/O- JOINT
(arthroscopy)
• CERVIC/O- NECK
(cervicoplasty)
• CHONDR/I,
CHONDR/O,
CHONDR/IOCARTILAGE
(chondromalacia)
• COST/O- RIB (intercostals
muscles)
• GNATH/O- JAW
(brachygnathous)
• MYEL/O- BONE
MARROW OR SPINAL
CORD (myelocyte,
myelogram)
• THORAC/OCHEST(thoracocentesis)
ROOTS
• MY/O- MUSCLE
(myositis)
• OCCIPIT/O- BACK
OF HEAD
(occipitoatlanto)
• OSS/EO, OSS/I,
OST/E, OST/EOBONE (osteotome)
• SACR/O- SACRUM
(sacroiliac joint)
• SPONDYL/OVERTEBRA
(spondylosis)
• STERN/O- STERUM
(sternotomy)
• STETH/O- CHEST
(stethoscope)
• TEND/O, TEN/OTENDON
(tendonectomy)
Introduction
• My/o/logy: Study of muscles
• Functions
–
–
–
–
Movement: contract and extend muscles
Posture: Support and maintenance
Producing body heat
Form: heart, uterus, lungs and intestines
• Always working
Tendon : attaches muscle to bone
• Tendons
– Strong FIBROUS white
bands
– Attaches muscle to
bone
• Ligaments
– Bone to bone
Tendon
• Aponeurosis
– Broad flat connective
tissue
– Attaches muscle >
bone OR muscle >
muscle
– “Flat and ribbon like”
Tendon Sheath
• CT around tendon
when there is a long
distance to attachment
or when tendon pulls
over a joint
Fascia : Sheet of fibrous tissue
that encloses muscles and
separates them into groups
Ligament : attaches bone to bone
or bone to cartilage
• Strong bands of
fibrous tissue
• Help/hinder
movement and support
organs
Origin - Insertion
• Origin : the less
movable of the two
points of attachment
• Insertion : the point of
attachment by a
muscle
Portion that moves
during contraction
Muscles
• Muscles may attach directly to cartilage,
joints, skin, mucous membrane, or fascia of
other muscles
Muscle cells
• Motor or neuromotor
unit: nerve cell +
group of muscle cells
• Causes muscle to
move by stimulating a
group of muscle fibers
circumduction
• FLEXION – bending at a joint
• EXTENSION – straightening at a
joint
• ABDUCTION – moving a body
part away from the body
• ADDUCTION – moving a body
part toward the body
• ROTATION – turning a body part
on its axis
• CIRCUMDUCTION – circular
movement
Composition of muscle
• Long slender cells called MYOFIBERS
– Larger than other body cells
• Plasma membrane: sarcolemma
• Cytoplasma: sacroplasma
• Fascia: Encloses fibers which are held
together by CT
• Within myofibers there are multiple
myofibrils
Composition of muscle
• Very vascular
• Move when fibers contract
• Speed: varies with type muscle and size of
body part to be moved
– Smaller structures move faster e.g. eye
• Movement carried out by group of muscles
• Exercise increase fiber thickness, does not
produce NEW fibers
Muscle Classification
SKELETAL
SMOOTH
• Voluntary
• Controlled at
will
• Nerves make
them contract
and extend
• Striated
• Microscopically
have cross
striated or
stripped
appearance
• Visceral
• Internal organs
• Involuntary
• Nonstriated
CARDIAC
• Involuntary
• Striated
SKELETAL
• Voluntary
• Striated
• Usually attached to
skeleton
– Striated muscle not
attached to skeleton:
eyes, tongue, pharynx,
skin muscles, heart
• Contract: muscle becomes
short and thick
• CNS and PNS
SMOOTH
• Visceral
• Not striated
Some organs = skeletal + smooth
e.g. esophagus ruminants:
– Spindle shaped fibers regurgitate and chew cud
• Involuntary
– Not controllable at will
• Stomach, intestine,
uterus, blood vessel,
eye-iris
– Some influenced by
hormones
bladder
uterus
Smooth muscle vs skeletal
muscle
CARDIAC
• Striated
• Involuntary
– Unlike other
involuntary muscle
– Fine transverse
striations
• ANS
cardiac
striated
smooth
Muscle attachments
• Muscle > tendon > phalanges: movement
and reduction of bulk
• Voluntary m. – bone
– Except larynx and thorax: muscle is attached to
thorax
• Attached to skin (cheek), mucous
membrane (tongue)
• Attached to fascia of other muscles
A muscle must depend on other
muscles to assist in a desired
movement. For this reason
muscles are called prime movers,
antagonists and synergysts.
Primer Movers
Muscles that actively produce a
movement
Antagonist
Muscles that are in opposition to
the prime movers
Synergist
Muscles that contract
simultaneously with the prime
mover to help execute a
movement or steady a part
The names of muscles are based on six
points of identification
* named for their action
* named for their origin and insertion
* named for their location
* named for their shape or use
* named for the direction of their fibers
* named according to the number of their
sections
• ORBICULARIS OCULI (C)– moves the eyelids
• MASSETERS (M) – muscles of mastication that
raise the mandible to close the jaw
FACIAL
MUSCLES
Serratus muscle group
Assist in respiration
Support trunk of the body
MUSCLES OF
NECK, BACK,
AND THORAX
• PECTORALS (7) – forms
chest, adducts forelimb
• LATISSIMUS DORSI (2) –
broadest muscle in the back.
Provides support for the
forelimb and aids in flexion
of the shoulder
EPAXIAL MUSCLES IN BACK
EXTEND THE THORAX AND PRODUCE
LATERAL MOVEMENT OF THE
TRUNK
-ILIOCOSTALIS
-LONGISSIMUS
-TRANSVERSOSPINALIS
MUSCLES OF THORAX
AID IN RESPIRATION, ALLOW THE THORAX TO
ENLARGE AND THE LUNGS TO EXPAND
- INTERCOSTALS (external
and internal):respiratory
muscles that are located
between the ribs
– DIAPHRAGM – wall that
separates the abdominal
and thoracic cavities
During respiration:
the external intercostals lift the
ribs
the internal intercostals lower the
ribs
the diaphragm contracts and
flattens out causing the thorax to
enlarge and the lungs to expand
MUSCLES OF FORELIMBS
• BICEPS BRACHII – flex the distal
forelimb
• TRICEPS BRACHII – extend the distal
forelimb
ABDOMINAL MUSCLES
KEEP VISCERA IN PLACE, SUPPORT
AND COMPRESS THE ABDOMEN,
CONTRACT (DURING PARTURITION,
DEFECATION, URINATION,
COUGHING), ROTATE THE
VERTEBRAL COLUMN
tricep
bicep
ABDOMINAL MUSCLES
•
•
•
•
EXTERNAL OBLIQUE
INTERNAL OBLIQUE
RECTUS ABDOMINUS
TRANSVERSUS ABDOMINUS
• LINEA ALBA – fibrous band of connective
tissue that is the center of attachment of the
abdominal muscles on the ventral
abdominal wall. Landmark for Sx.
Rectus abdominis
External
oblique
Internal oblique
Transversus
abdominis
Linea alba
Muscles of the hindlimb
These muscles have several
functions in movement. The most
important muscle groups include
*gluteal group
*quadricep group
*semi group
MUSCLES OF THE HINDLIMB
• GLUTEALS – located over the pelvis, extend and abduct
the limb
• QUADRICEPS FEMORIS – extend the hind leg
– Rectus femoris, vastus lateralis, vastus medialis, vastus
intermedius
MUSCLES OF
THE HINDLIMB
• GROUP THAT IS LOCATED
ON THE POSTERIOR
ASPECT OF THE LIMB.
FORMS THE HAMSTRINGS
AND FLEXES THE HIND LEG
- SEMIMEMBRANOSUS
– SEMITENDINOSUS
– BICEPS FEMORIS
MUSCLES OF THE HINDLIMB
• GASTROCNEMIUS
– Flexes the leg and foot
- Forms the Achilles Tendon
Miscellaneous muscles:
arrector pili
These are smooth muscles
attached to hair on the dorsum.
When stimulated these muscles
raise the hair on the back.
Cutaneous trunci:
a muscle that attaches to the dermis and
controls the insect twich in large animals
Another large animal muscle is the
cremaster, this muscle is part of the
spermatic cord and attaches to the
scrotum. This muscle contracts and
relaxes, raising and lowering the testicles.
This movement helps to regulate testicular
temperature