Anatomy Lecture notes on Skeletal Muscle

Gross Human Structural Biology
Skeletal Muscles
D. Definition of innervation of muscle
OUTLINE ✓ Nerve to a muscle is motor nerve
I. Introduction to Skeletal Muscles ✓ Usually only one nerve supplies a muscle
Definition of Terms ✓ Nerve consists of bundles of nerve fibers
✓ Each nerve fiber supplies one or more muscle
II. AXIAL MUSCLES
fibers
III. APPENDICULAR MUSCLES
A. UPPER EXTREMITY E. Importance of nerve supply
✓ Responsible for functional activity and structural
B. LOWER EXTREMITY
integrity of muscles
✓ Maintenance of muscle tones
I. INTRODUCTION TO SKELETAL MUSCLE ✓ Gives a clue as to origin of certain muscles group
A. Function (e.g. splenic nerve – supplies abdomen)
✓ For locomotion
✓ Generation of heat F. Motor unit
✓ Gives shape and contour of the body ✓ Consists of:
B. Classification of muscles according to embryonic origin: -Nerve Fibers
✓ Branchiomeric – arise from the branchial arches -Muscle Fibers (group of muscle fibers
(e.g. face muscles) it supplies)
- Supplied by cranial nerves
✓ Myotonic – muscles arise from myotomes II. INTRODUCTION TO SKELETAL MUSCLE
- Supplied by cranial nerves
C. Bases of nomenclature A. MOTOR POINT
Shape Trapezius ➢ Entrance or point where the nerve enters the muscle at
Rhomboideus about the midpoint on its deep surface, often near the
Deltoid margin.
Quadratus
Maximus B. MUSCLE TONE
Size
➢ A small amount of tautness or tension in the muscle due to
Minimus
weak, involuntary contraction of its motor units.
Major
Minor ➢ It keeps skeletal muscles firm, but it does not result in a
force strong enough to produce movement.
Location Frontalis
Ex.
Occipitalis
1. UPRIGHT POSITION OF THE HEAD
Brachii
-when the muscles in the back of the neck are in normal
Femoris
Abdominis tonic
Contraction, they keep the head upright and prevent it from
Direction of fibers Rectus
slumping forward on the chest.
Oblique
Transversus
2. GASTROINTESTINAL TRACT
Points of attachment Sternocleidomastoid
-where the walls of the digestive organs maintain a steady
Hyoglossus
pressure on their contents.
Position Superior
Inferior
3. WALLS OF THE BLOOD VESSELS
External
-plays a crucial role in maintaining blood pressure.
Internal
Action Flexor
C. ACTION OF MUSCLE
Extensor ➢ 1. PRIME MOVER OR AGONIST
Supinator -muscle whose contraction is chiefly responsible for
Pronator Producing a particular movement
Structure Semitendinosus
Semimembranosus Ex. Biceps brachii-prime mover producing flexion of forearm
Number of Bellies Digastric
Number of Heads Quadriceps ➢ 2. ANTAGONISTS
Biceps - oppose action of the agonist
Combination External Oblique - slowly relaxing
Association (position and direction of fibers)
Miscellaneous Sartorius (tailor) Ex. Triceps brachii which extends forearm is the antagonist of
Buccinator the Biceps brachii which flexes arm




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, Gross Human Structural Biology
Skeletal Muscles
➢ 3. SYNERGISTS MUSCLE FUNCTIONS
PARTS OF THE
-contraction assists prime movers in performing
FACE
action to reduce excess and unnecessary motion
✓ Laughing
Ex. Latissimus dorsi is a back muscle that extends, adducts and muscle
medially rotates arm. Teres major is a synergist helping ✓ Zygomaticus minor ✓
latissimus dorsi in starting its action when arm is at full flexion. ✓ Corrugator supercilli ✓ Draws
eyebrow
➢ 4. FIXATOR Eyes medially
- contracts isometrically to stabilize the origin of the
✓ Orbicularis oculi ✓ Closes eyes
prime mover so that it can act efficiently.
✓ Procerus ✓ Wrinkles root
Ex. The muscles attaching the shoulder girdle to the trunk of nose
contract as fixators to allow deltoid to act on the shoulder joint. ✓ Nasalis ✓ Compresses
Nose
nose as in
D. TYPES OF MUSCLE sniffing
➢ 1. SKELETAL MUSCLE - associated with skeletal system ✓ Dilates alae
- usually attached to bones ✓ Auricular muscles ✓ Moves ears to
-striated and voluntary Ear (Extrinsic) different
➢ 2.CARDIAC MUSCLE -found in the heart directions
-striated and involuntary ✓ Epicranius ✓ Moves scalp
➢ 3.SMOOTH MUSCLE -found in the wall of visceral organs forward and
Like blood vessels, digestive tract, backward
Respiratory tract, urinary and • Made up of the
Reproductive system following:
➢ 4.APONEUROSIS and TENDINOUS PART -Frontalis
Scalp
✓ - For
E. PARTS OF MUSCLE transverse
➢ 1. ORIGIN - stationary attachment of muscle usually to wrinkles in
Bone -Occipitalis forehead when
➢ 2.INSERTION- movable attachment of the muscle one is
➢ 3.BELLY- fleshy part of the muscle surprised

INTRINSIC VS. EXTRINSIC B. EXTRA OCCULAR MUSCLES- Move eyeballs in different
➢ INTRINSIC directions
- group of muscle in a region of the body whose origin
MUSCLE MOVEMENTS
And insertion are confined to that region.
Inferior Rectus ✓
➢ EXTRINSIC
Medial Rectus
- muscle with attachment to part of another region
Superior Rectus
Of the body
Inferior Oblique
Levator Palpebrae Superioris ✓ Opens eyes
III. AXIAL MUSCLE
Superior Oblique ✓
A. FACIAL EXPRESSIONS MUSCLES
Lateral Rectus ✓

PARTS OF THE MUSCLE FUNCTIONS
C. MASTICATION MUSCLES- Supplied by CN V (trigeminal nerve
FACE - Muscles used for chewing
✓ Buccinator ✓ Trumpeteer’s MUSCLE MOVEMENTS
Muscle ✓ Temporal ✓ Elevation (close mouth)
✓ Depressor labii inferioris ✓ Quadrangularis ✓ Masseter,
✓ Medial pterygoid
✓ Levator labii superioris ✓
✓ Lateral pterygoid ✓ Depression (open
Mouth ✓ Mentalis ✓ ✓ Suprahyoid mouth)
✓ Orbicularis oris ✓ Purses lips ✓ Infrahyoid muscles
✓ Risorius ✓ Sardonic Smile ✓ Lateral pterygoid ✓ Protrusion (protrude
✓ Depressor anguli oris ✓ Triangularis ✓ Masseter chin)
✓ Medial pterygoid
✓ Zygomaticus major ✓ Sweet smile
✓ Temporal (posterior oblique and ✓ Retrusion (retrude chin)
near horizontal fibers)

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