Anatomy 4 (Muscles)

Muscle Characteristics

• Contractile

• Excitable

• Elastic

• Extensible

Muscle Functions

• Movement

• Stability

• Storage

• Guard entrance/exit

• Thermogenesis

Sarcolemma

Muscle cell membrane

Sarcoplasm

Muscle cell cytoplasm

Epimysium

Fibrous connective outer layer holding the entire muscle together

Perimysium

Areolar layer that surrounds bundles of muscle fibers

Endomysium

Areolar layer surrounding each muscle fiber

Sarcolemma

Plasma membrane of individual muscle fibers

Myofibrils

Rod-shaped organ in muscle cells made of sarcomeres that makes muscle contract

Sarcoplasmic Reticulum

Modified ER in muscle cells of fluid-filled sacs that encircle each myofibril

• Stores and releases Ca

• Contain terminal cisterns

Terminal Cisterns

Part of the SR and release Ca

• Traid

T-Tubules

Small invagination of the sarcolemma filled with fluid that helps move electrical signals down the fiber

• Triad

Triad

2 terminal cisterns and 1 T-Tubule

Sarcomere

Functional unit of myofibrils

• Thick and thin filaments between z disks

I Band

Thin filaments only

A Band

Thick and thin filaments

H Zone

Thick filaments only

Contractile Muscle Proteins

Actin (thin) and myosin (thick)

Regulatory Muscle Proteins

Troponin and tropomyosin

• Act as an on/off switch for muscle contraction by controlling contact between actin and myosin

Structural Muscle Proteins

• Titin

• Myomesin

• Nebulin

• Dustrophin

Titin

Coiled between Z-lines for elasticity

Myomesin

Found in the M-line to cross-link myosin

Nebulin

Stiffens/stabilizes actin

Dystrophin

Aligns actin with sarcolema

• Muscular Dystrophy

Flexion

Decrease angles between bones

Extension

Increase angles between bones

Lateral Flexion

Flexion in the frontal plane

Abduction

Away from midline

Adduction

Towards midline

Supination

Turns palms anteriorally

Pronation

Turns palms posteriorally

Inversion

Turning sole medially

Eversion

Turning sole laterally

Dorsiflexion

Top of the foot moves towards tibia

Plantar Flexion

Sole of the foot moves posteriorly

Protraction

Forward from horizontal plane

Retraction

Backward from horizontal plane

Origin

Attachment to a stable, less movable bone

Insertion

Moveable end of the muscle

Parallel Arrangment

Fibers run parallel along axis

Converging Arrangment

Fibers come to together on one end

Unipennate Arrangment

Attach to 1 side of a tendon

Bipennate Arrangment

Attach to 2 sides of tendon

Multipennate Arrangment

Attach to central tendon on all sides

Circular Arrangement

Rings of fibers

Frontalis

Creases forehead

• O: Aponeuosis

• I: Skin

Aponeurosis

Tendon sheet

Orbicularis Oculi

Around the eyes to squint

Orbicularis Oris

Around the mouth to purse lips

Levator Palpebrae

On eyelids to open eyes

Zygomaticus Major and Minor

Smile

• O: Zygomatic arch

• I: Skin

Platysma

Tightens skin

• O: Fascia on clavicle

• I: Mandible

Depressor Anguli Oris

Side of mouth going down

Nasalis

On nose

Masseter

Closes jaw

• O: Zygomatic arch

• I: Mandibular ramus

Buccinator

In cheeks

Mentalis

On chin

Temporalis

Closes the jaw

O: Temporal fossa

I: Coronoid process

Pterygoids

Medial: On bottom

Lateral: On top, opens the jaw

Mylohyoid

Opens the jaw

O: Mylohyoid line of mandible

I: Hyoid

Rectus Muscles

4 side of the eyes

• Medial

• Lateral

• Superior

• Inferior

Superior Oblique

Move eye down and out

Inferior Oblique

Move eye up and out

Genioglossus

Anterior/outwards and rolls tongue

• O: Mandible

• I: Tongue

Styloglossus

Tongue up and back

• O: Styloid process

• I: Tongue

Palatoglossus

Tongue up and back

• O: Soft palate

• I: Tongue

Hyoglossus

Tongue sides down

• O: Hyoid

• I: Tongue

Geniohyoid

Tongue muscle that depresses mandible

• O: Mandible

• I: Hyoid

Diagastric

Moves mandible down

• Mastoid to chin

Stylohyoid

Stabilize hyoid for tongue movement

• O: Styloid

• I: Hyoid

Geniohyoid

Mandible down

• O: Mandible

• I: Hyoid

Omohyoid

Stabilize hyoid for tongue movement

• O: Hyoid

• I: Clavicle

Sternohyoid

Stabilize hyoid for tongue movement

• O: Sternum

• I: Hyoid

Sternothyroid

Stabilize hyoid for tongue movement

• O: Sternum

• I: Thyroid

Thyrohyoid

Stabilize hyoid for tongue movement

• O: Thyroid

• I: Hyoid

Sternocleidomastoid

Head movement

O: Manubrium and clavicle

I: Mastoid

Other muscles of head movement

• Semispinalis capitis

• Splenius capitis

• Longissimus capitis

• 3 scalenes

Rectus Sheath

Tendon sheath over abs

Linea Alba

Midline between abs

Linea Semilunaris

Lateral edge of abs

Inguinal Ligament

ASIS to pubic tubercle; marked by V line

External Oblique

Rotation, trunk + lat flex

• O: Lower ribs

• I: Linea alba

• Runs diagonally downward

Internal Oblique

Trunk + lat flex

• O: Lumbodorsal fascia + iliac crest

• I: Linea alba

• Run upward and inward perpendicular to external obliques

Transversus Abdominus

Tension to support the spine and pelvis

• O: Lumbodorsal fascia iliac crest, lower ribs

• I: Linea alba

• Runs horizontally

Tranversalis Fascia

Under transversus abdominus

Rectus Abdominus

Trunk flexion and forced exhalation

• O: Pubic crest and symphysis

• I: Xiphoid and lower ribs

Quadratus Lumborum

Ext, lat flex

• O: Iliac crest

• I: Lower ribs and lumbar vert

Inguinal Canal

Canal formed by 3 arches of muscle (2 obliques and transversus abdominus)

• Holds nerves, tendons, spermatic cord

Natural Respiration Muscles

• Ext and Int Intercostals

• Transversus Thoracis

• Rectus Abdominus

• Diaphragm

External Intercostal

Elevate rib below for inhale

Internal Intercostals

Depress rib above during exhale

Transversus Thoracis

Ribs to sternum

Diaphragm

O: Everywhere (ribs and L3)

I: Central tendon and connect with pleura and pericardium

Diaphragm Landmarks + Vertebrae

• IVC: T8

• Esophagus: T10

• Aorta: T12

Accessory Respiration Muscles

• Sternocleidomastoid

• Scalenes

• Pec Minor

• Internal Intercostals

• Rectus Abdominus

Superficial Back Muscles

• Trap

• Lat

• Rhomboid Maj/Min

• Levator Scapulae

Deep Back Muscles

• Erector Spinae Group

• Multifidus

• Quadtratus Lumborum

Erector Spinae Group

Along the vertebral column for ext, lat flex, rot

Multifidus

Spinal extension and rotation

O: Transverse processes

I: Spinous processes

Subclavius

Elevates 1st rib, depresses 2nd rib

O: 1st rib

I: Subclavian groove