muscle new anatomy

functions of muscular system

movement; posture and joint stabilization; respiration; communication (speaking, writing, facial expressions); thermoregulation; heart rate regulation; internal organ function

skeletal muscle

voluntary muscle attached to bones by tendons

tendons

attach muscle to bone; composed of collagen

ligaments

attach bone to bone

fascia

connective tissue that encases skeletal muscle

functions of fascia

protects muscle; attaches muscle to bone; provides pathway for nerves, blood vessels, and lymph vessels

skeletal muscle structure

each skeletal muscle is a separate organ encased in connective tissue

skeletal muscle description

voluntary and striated

voluntary muscle

direct control by the CNS

striated muscle

striped microscopic appearance due to sarcomeres

muscle fiber

a single multinucleated muscle cell

sarcolemma

plasma membrane of muscle fiber

sarcolemma function

propagates electrical impulses for contraction

sarcoplasm

cytoplasm of muscle cell; contains organelles like normal cytoplasm

sarcotubular system

unique to muscle; consists of sarcoplasmic reticulum and transverse (T) tubules for calcium regulation

muscle membrane

composed of sarcolemma and basement membrane

basement membrane

functions as microskeleton and maintains muscle fiber shape

myofibrils

bundles within muscle fibers arranged in parallel

functional unit

sarcomere

functional contractile unit of myofibril; contains actin and myosin filaments

actin

thin filament of sarcomere

springy ends

myosin

thick filament of sarcomere

nonprotein constituents of muscle

Nitrogen

Creatine and creatinine

Glycogen

Amino acids

Uric acid

creatine build up due to

kidney failure

creatine & creatinine tracking metabolism used for

measuring muscle mass

muscle wasting causes

creatine excertion ⬆️

creatinine excretion ⬇️

excitation-contraction coupling

action potential triggers calcium release from SR, leading to contraction

short term energy supplies for muscle contraction

glycogen and blood glucose

sarcoplasmic reticulum

stores and releases calcium for contraction

muscle fiber energy requirements

constant ATP and phosphocreatine supply; glycogen and blood glucose for short-term energy

creatine phosphate / phosphocreatine

rapid ATP donor for cross-bridge cycling

cardiac muscle

striated, branched, involuntary muscle of the heart; contains intercalated discs (gap junctions)

intercalated discs

gap junction

specialized connections for electrical and mechanical syncytium in cardiac muscle

syncytium

cytoplasm of different cells conjoin to have multiple nuclei in one cell

smooth muscle

non-striated, involuntary; found in walls of hollow organs (viscera); arranged in circular and longitudinal layers

major upper arm muscles

biceps, triceps, brachialis

biceps

function: elbow flexion and forearm supination

triceps

function: elbow extension; antagonist to biceps

brachialis

function: lifts ulna; assists in elbow flexion

muscles of hip

gluteus maximus, gluteus medius, adductors

gluteus maximus

forms most of hip; powerful hip extensor; aligns thigh with pelvis

gluteus medius

located beneath gluteus maximus; hip abductor; steadies pelvis during walking; site for IM injections

adductors

adduct thighs together

jaw muscles

temporalis muscle and masseter muscle

masseter muscle

elevates the mandible (jaw bone)

temporalis muscle

elevates and retracts mandible (jaw bone)

sternocleidomastoid muscle

neck muscle

flexes and rotates head

trapezius muscle

extends head

adduct, elevate, or depresses scapula (wing bone)

latissimus dorsi

extends, adducts, and medially rotates arm

deltoid muscle

round shape of shoulders (어깨 모양)

Prime abductor of arm

abdominal muscles

rectus abdominis

external oblique

internal oblique

rectus abdominis

flexes vertebral column

compresses abdomen during pooping and birthing

external oblique

flexes vertebral column

rotates trunk, bends laterally

internal oblique

accessory respiration and lateral bending

bending of trunk

pectoralis major

chest muscle

movement of arm

adduction of humerous

flexion of humerous

intercostal muscles

move chest wall (chest muscle)

accessory muscles for breachest musclefor breathing

hamstring muscles

thigh and knee

biceps femoris, semimembranosus, semitendinosus

thigh extension and knee flexion

sartorius

thigh/knee muscle

weak flexion of thigh

quadriceps

thigh/knee muscle

4 muscles

flexes hip, extend knee; crosses hip and knee joints

Tibialis anterior

Dorsiflexion and inversion of foot

Extensor digitorum longus

toe extension

Gastrocnemius

Plantar flexion of foot; lifts heel

Soleus

Plantar flexion of foot

aging in muscular function

decreased range in motion

loss in muscle mass

decreased lean body mass (less muscle, more fat)