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Muscle fiber

The name of a single muscle cell

Endomysium

Surrounds each muscle fiber areolar CT

Perimysium

Dense irregular CT around fascicles

Fascicles

Groups of muscle fibers

Epimysium

Dense irregular CT that surrounds the whole muscles

Deep fascia

Still coarser layer of CT that binds muscles into functional groups. Ex: separates muscle like hamstrings and quadriceps.

Direct attachment

Epimysium fused to periosteum of bone or perichondrium of cartilage.

Indirect attachment

Connective tissue wrapping of muscles extend as rope like tendon. or sheet like aponeurosis

Functional groups (4)

Prime mover

Antagonist

Synergist

Fixator

Prime mover muscles

Provides major force for a particular movement

Antagonist muscle

Opposes or reverses a particular movement. Located on opposite sides of joint from agonist muscles.

Synergist muscles

Muscles that help prime mover by promoting the same movement. Add force to the movement and reduce undesirable or unnecessary movement.

Fixator muscles

Synergists that immobilize a bone or muscles origin.

Parallel arrangement of fascicles

Fascicles parallel to the long axis of a strap like muscle.

Can be strap like or fusiform.

Pennate arrangement of fascicles

Short fascicles attached obliquely to a central tendon running the length of the muscle.

Can be uni, bi or multipennate.

Circular arrangement of fascicles

Concentric rings surrounding external openings & contract to close opening.

Convergent arrangement of fascicles

Fascicles converge towards a single tendon insertion, muscle is triangular or fan shaped.

Naming skeletal muscles (8)

1. Muscle location

2. Muscle shape (ex: deltoid)

3. Muscle size (ex: maximus, minimus)

4. Direction of muscle fibers or fascicles

5. Number of origins (ex: bicep, tricep)

6. Location of attachment (origin named first then insertion)

7. Muscle action (flexor, extensor)

8. Several of these criteria can be combined

Axial muscles

Stabilizes and positions the head, neck and trunk.

Can be divided into 4 broad groups based on location and/ or function. ( head & neck, oblique & rectus, vertebral column, pelvic floor)

The head muscles

Split into two major groups:

1. Muscles of facial expressions: Insert into skin and other muscles, not bone.

2. Muscles of mastication and tongue movement.

Scalp muscle

Epicranius: made of two parts, the frontal belly and the occipital belly. These two bellies are connected by the epicranius aponeurosis.

Frontal belly: Connects the aponeurosis to the skin of eyebrows. Raises eyebrows and wrinkles forehead.

Occipital belly: Connects the occipital and temporal bones to the aponeurosis. Pulls scalp posteriorly.

Muscles of facial expression (5)

Orbicularis oculi

Zygomaticus

Orbicularis oris

Buccinator

Platysma

Orbicularis oculi

Surrounds rims of orbit (eyes)

For blinking, squinting, drawing eyebrows down.

Zygomaticus

From zygotmatic bone corner of mouth.

Raises lateral corner of mouth. (smiling muscle)

Orbicularis oris

From maxilla and mandible to skin and muscles around mouth.

Lip movement, whistling, kissing, closing.

Buccinator

Mandible/maxilla to orbicularis oris muscle. found deep to masseters.

For holding food in place while chewing, sucking and whistling.

Platysma

From fascia of chest to mandible.

Helps depress mandible, and tenses skin of neck. (shaving muscle)

Muscles of mastication (4)

4 muscles, on each side.

Masseter

Temporalis

Medial pterygoid

Lateral pterygoid

Last two are for grinding movement.

Masseter muscle

From zygomatic arch and bone to the angle and ramus of mandible.

This is the prime mover of jaw closure.

Temporalis bone

From temporal fossa to coronoid process of mandible.

Elevates and retracts mandible (jaw). Maintains closed jaw at rest.

Medial and lateral pterygoid muscles

From pterygoid process of sphenoid bone to the mandible. For jaw movement from side to side. (grinding)

Muscles of tongue movement (3)

Genioglossus

Styloglossus

Hyoglossus

Genioglossus

From mandible to inferior tongue and hyoid bone.

Prime mover of tongue protrusion. anchors tongue to prevent obstructed airways.

Styloglossus

From styloid process of temporal boneto inferolateral tongue,

Retracts and elevates tongue.

Hypoglossus

From hyoid bone to inferolateral tongue.

Deoresses tongue

Musclesof eye movement (6)

Lateral rectus: Moves eye laterally

Medial rectus: Moves eye medially

Superior rectus: Elevates eye and turns it medially

Inferior rectus: Depresses eye and turns it medially

Inferior oblique: Elevates eye and turns it laterally

Superior oblique: Depresses eye and turns it laterally

Muscles of head movement (4)

Sternocleidomastoid (SCM)

Anterior, middle and posterior scalenes.

Sternocleidomastoid muscle

From manubrium/clavicle to mastoid process of temporal bone.

Two headed, found just deep to platysma.

Prime mover of head flexion (lifting head when laying down on back) Also for head rotation towards opposite shoulder.

Scalenes

all 3 (posterior, middle and anterior) from the cervical vertebrae to the first two ribs. Deep to SCM

For elevating first two ribs and flexes and rotates head. Aids in respiration.

Intrinsic muscles of the back (4)

For trunk movement and back posture

Splenius

Erector Spinae

Semispinalis

Quadratus lumborum

Splenius

From spinous process of vertebrae to mastoid process of temporal bone and occipital bone.

Is the antagonist muscle to the SCM. fro head extension ad rotation, tilt.

Erector spinae

Also called sacrospinalis.

Prime movers of back extension and lateral bending.

Each side consists of 3 columns: Iliocostalis, longissimus and spinalis. These resist bending forwards and act as extensors to return to erect posture.

Semispinalis

Deep layer of back muscles, 3 parts composite muscle from thoracic region to head.

Extends vertebral column & head, rotates head synergistic with SCM)

Quadratus lumborum

From iliac crest to lumbar vertebrae.

Individual muscles flex vertebral column laterally Jointly they extend lumbar spin & fix the 12th rib..