Muscle Anatomy & Muscles of Head, Neck, Thorax, Abdomen & Back

primary function of muscles

move bones, maintain posture, generate heat, move substances through body, enable breathing

three types of muscle tissue

skeletal, cardiac, smooth

skeletal muscle function

moves bones and generates heat

myocytes

skeletal muscle cells containing myoglobin; arranged in bundles

striations

lines marking sarcomeres, the contractile unites

skeletal muscle nuclei

multiple nuclei per cell

muscle fascia

outer connective tissue layer; becomes tendons

eipmysium

dense connective tissue surrounding entire muscle

perimysium

surrounds fascicles

endomysium

surrounds individual muscle fibers

sacolemma

cell membrane of muscle fiber

cardiac muscle characteristics

striated, one nucleus, contains intercalated discs

intercalated discs

specialized junctions allowing synchronized contraction

cardiac muscle control

involuntary; contains nodes that generate impulses

smooth muscle characteristics

no striations, one nucleus, involuntary

where smooth muscle is found

digestive, urinary, reproductive systems; blood vessels

peristalsis

wave-like contractions that move substances through organs

origin

less mobile end of a muscle

insertion

more mobile end of a muscle

tendon

dense connective tissue connecting muscle to bone

Ligament

a tough, fibrous band of connective tissue that connects bones to bones, or bones to cartilage, to stabilize joints and hold organs in place

aponeurosis

broad, flat tendon (e.g., iliotibial band [IT])

agonist

muscle that produces a movement

antagonist

muscle that opposes the agonist

example of agonist/antagonist at elbow

biceps = agonist for flexion; triceps = antagonist

epicranial aponeurosis

connective tissue band from front to band of head

occipitofrontalis

wrinkles forehead

orbicularis oculi

opens and closes the eye

orbicularis oris

puckers lips

buccinator

compresses cheek

sternocleidomastoid

turns the head

trapezius (neck function)

shrugs shoulders

levator scapulae

elevates scapula

scalenes

assist in lateral flexion of neck

pectoralis major

moves humerus; chest muscle

serratus anterior

protracts scapula; stabilizes shoulder

external oblique

outer abdominal layer; trunk rotation

rectus abdominis

flexes trunk; “six-pack” muscle

linea alba

midline connective tissue of abdomen

internal oblique

middle abdominal layer; trunk rotation

transversus abdominis

deepest abdominal muscle; core stability

trapezius

moves scapula; extends neck

rhomboid major & minor

retract (pinch) shoulder blades

deltoid

abducts arm; shoulder muscle

latissimus dorsi

extends, adducts, and internally rotates humerus

erector spinae group

longissimus, spinalis, iliocostalis; extend and stabilize spine

longissimus

long fibers; part of erector spinae

spinalis

attaches to spine; part of erector spinae

iliocostalis

attaches ilium to ribs; part of erector spinae

multifidus

short deep back muscles; stabilizes spine

rotators

small deep muscles that rotate spine