Ch.11 muscles of the body HHP 3115

lever

rigid bar that moves, bones

fulcrum

fixed joint, joints

effort

applied force, muscle contraction

load

resistance (bone + tissues + any added weight) moved by the effort

lever systems

- move a heavier load

- move a load farther

- mechanical advantage: moves a large load over small distances

- mechanical disadvantage: allows a load to be moved over a large distance

first class lever

effort applied at one end, load is at the oppostie end, fulcrum is located between load and effort

ex: seesaws, scissors, and lifting your head off your chest

- some work at mechanical advantage, some at disadvantage

second class lever

effort applied at one end, fulcrum is at the oppostie end, load is between the effort and fulcrum

ex: wheelbarrow or standing on tiptoe

- uncommon type of lever in the body

- work at a mechanical advantage

third class lever

- effort is applied between the load and the fulcrum

- works speedily

- always at a mechanical disadvantage

- most skeletal muscles are these type of levers

fascicles

- firbils and myofibrils

- arranged in different patterns

- determines action of a muscle

parallel fascicle arrangement

run parallel to the long axis of the muscle

convergent fascicle arrangement

- origin of the muscle is broad

- fascicles converge toward the tendon of insertion

pennate fascicle arrangement

unipennate: fascicles insert into one side of the tendon

bipennate: fascicles insert into the tendon from both sides

multipennate: fascicles insert into one large tendon from all sides

circular fascicle arrangement

- arranged in concentric rings

- surround external body openings

- sphincter: general name for a circular muscles, act as valves

interactions of skeletal muscles in the body

- a muscle cannot reverse the movement it produces, it can only shorten

- another muscle must undo the action

- muscles with opposite actions lie on opposite sides of a joint

prime mover (agonist)

has major responsibility for certain movement

antagonist

opposes or reverses a movement

synergist

helps prime mover, adding extra force, reducing undesirable movements

fixator

type of synergist that holds a bone firmly in place

naming the skeletal muscles

location, shape, relative size, direction of fascicles and muscle fibers, location of attachments (origin/insertion), number of origins, action

muscles of facial expression

- lie in the face and scalp

- thin and variable in shape

- oftern insert in the skin (insertion is not on bones)

- innervated by cranial nerve VII (the facial nerve)

- unique because they attach to bone and then attach to skin

smiling muscle

zygomaticus minor and major

muscles of mastication

- innervated by mandibular division of the trigeminal nerve (cranial nerve V)

- prime movers of jaw closure: masseter and temporalis

- side-to-side movement: pterygoid muscles

- compression of cheeks: buccinator muscles

extrinsic msucles of the tongue

- move tongue laterally, anteriorly, posteriorly

- all innervated by cranial nerve XII, the hypoglossal nerve

muscles of the anterior neck and throat- swallowing

- divided into anterior and posterior triangles by the sternocleidomastoid

- anterior triangle: divided into suprahyoid and infrahyoid muscles, participate in swallowing

- pharyngeal constrictors: squeeze food into the esophagus

- act of swallowing starts as voluntary, then becomes involuntary, skeletal muscle > smooth muscle

head movement

sternocleidomastoid, splenius capitis, splenius cervicis

trunk extension

deep muscles of the back

- maintain normal curvatrures of the spine

- form a column from sacrum to the skull

- erector spinae group: largest of the deep back muscles, keep spine extended

deep muscles of the thorax- breathing

- deep muscles provide movements for breathing

- external intercostal muscles: lift the rib cage

- internal intercostal muscles: aid expiration during heavy breathing

- diaphragm: most important muscle of respiration, flattens as it contracts, increases the volume of the thoracic cavity

muscles of the abdominal wall

- lateral and anterior abdominal wall, formed from three flat muscle sheets

- external oblique: inferomedially or superior laterally nagle

- internal oblique: inferior lateral or superior medially angle

- transversus abdominis

fourth muscle pair

- rectus abdominis, straight muscle fibers, inserts at the linea alba

superficial muscles of the anterior thorax

movements of the scapula

pectoralis major, pectoralis minor, serratus anterior

superficial muscles of the posterior thorax

movements of the scapula; trapezius, levator scapulae, rhomboid major, rhomboid minor

movements of the arm

deltoid, pectoralis major, latissimus dorsi, teres major, and rotator cuff:

- supraspinatus

- infraspinatus

- teres minor

- subscapularis

muscles crossing the elbow joint

anterior muscles: flexors of the forearm

- biceps brachii- also supinates the forearm

- brachialis

- brachioradialis

posterior muscles: extensors of the forearm

- triceps brachii

- anconeous

muscles of the forearm

- movements of the wrist, hand, and fingers

- tendons anchored by flexor and extensor retinacula

- most originate on the distal humerus

- movements at the wrist include flexion, extension, abduction, and adduction

- wrist and fingers are "operated" by muscles in the forearm: gives us ability to be strong in flexion, extension, abduction, and adduction

- flexors: anterior flexor compartment, innervated by median nerve and ulnar nerve, originate from a common tendon, medial epicondyle of the humerus

superficial anterior muscles of the forearm

• pronator teres,

• flexor carpi radialis,

• palmaris longus,

• flexor carpi ulnaris,

• flexor digitorum superficialis

deep anterior muscles of the forearm

flexor pollicis longus, flexor digitorum profundus, pronator quadratus

extensors of the forearm

- posterior compartment of the forearm

- innervated by the radial nerve

- originate at a common tendon, lateral epicondyle of the humerus

superficial posterior muscles of the forearm

• Brachioradialis, flexes forearm

• Extensor carpi radialis longus

• Extensor carpi radialis brevis

• Extensor digitorum

• Extensor carpi ulnaris

deep posterior muscles of the forearm

supinator, abductor pollicis longus, extensor pollicis brevis and longus, extensor indicis (extend index finger)

- muscles can extend individual fingers but can't extend 4th digit because it doesn't have its own muscle

intrinsic muscles of the hand

- fine movement of the fingers (not much force)

- all located in the palm

- control precise movements

- include muscles of adduction, abduction, and opposition

thenar muscles- ball of thumb

abductor pollicis brevis, flexor pollicis brevis, opponens pollicis, adductor pollicis

hypothenar muscles

• abductor digiti minimi,

• flexor digiti minimi,

• opponens pollicis

midpalmar muscles

lumbricals, palmar interossei, dorsal interossei

muscles crossing the hip and knee joints: thigh and leg movements

anterior muscles: flex the thigh and extend the leg at the knee

posterior muscles: extend the thigh and flex the leg

adductor muscles (on medial aspect of thigh): adduct the thigh only

deep fascia of the thigh: surrounds and encloses all three groups

muscles crossing the hip and knee joints: movements at the hip joint

muscles that flex the thigh: originate on vertebral column or pelvis

muscles that extend the thigh: arise posterior to the hip joint

- adductors originate medial to the hip joint

- abductors originate lateral to the hip joint

anterior and medial muscles of thigh

-Origin on pelvis or vertebral column: Iliacus (primary hip flexors), psoas major, sartorius (helps cross leg)

-Muscles of the medial compartment: adductor longus, adductor brevis, adductor magnus, pectineus, gracilis

muscles of the anterior compartment of the thigh

quadriceps femoris: 4 seperate heads, common insertion at the quadriceps tendon

- powerful knee extensors: rectus femoris, vastus lateralis, vastus medialis, vastus intermedius

tensor fasciae latae

posterior muscles of hip

- Origin on pelvis or sacrum

* Gluteus maximus

* Gluteus medius

* Gluteus minimus

- Lateral rotators

* Piriformis

* Obturator externus

* Obturator internus

* Superior and inferior gemellus

* Quadratus femoris

muscles of the posterior compartment of the thigh

hamstrings: biceps femoris (2 proximal attachments), semitendinosus, semimembranosus

- cross hip and knee joint, extension and flexion

muscles of the leg

fascia lata of the leg surrounds muscles: tightly binds muscles, prevents swelling during exercise, aids venous return, divides leg into three compartments (anterior, posterior, and medial)

tendons held in place by: extensor, fibular, and flexor retinacula

- muscle movement at ankle and intertarsal joints

muscles of the anterior compartment

- tibialis anterior: dorsiflexion

- extensor digitorum longus: extend toes

- fibularis terminus: comes off digitorum longus, goes down to lateral side of foot helps invert foot

- extensor hallucis longus: extends big toe

muscles of the lateral compartment

fibularis longus

fibularis brevis

- eversion, plantar flexion

muscles of the posterior compartment of leg

Superficial Muscles

-Triceps surae

*Gastrocnemius

*Soleus

-Plantaris

deep muscles: popliteus, flexor digitorum longus, flexor hallucis longus, tibialis posterior

intrinsic muscles of the foot

toe movement and foot support

- help to flex, extend, abduct, and adduct the toes

- support the arches of the foot

- single muscle on the dorsal aspect of the foot

- many muscles on the plantar aspect

muscles of the foot

muscle on the dorsal of the foot: extensor digitorum brevis

muscles on the sole of the foot

- first layer: flexor digitorum brevis, abductor hallucis, abductor digiti minimi

- second layer: flexor accessorius, lumbricals

- third layer: flexor hallucis brevis, adductor hallucis, flexor digiti minimi brevis

- fourth layer: plantar and dorsal interossei