A&P Exam 3- Ch.9 Muscular System

Skeletal Muscle gross anatomy (microscopic to organ)

1. skeletal muscle fibers are surrounded by thin layer extracellular matrix (endomysium)

2. 10-100 muscle fibers are bundled into a fascicle, surrounded by connective tissue (perimysium)

3. all fasicles in a muscle are surrounded by another layer of connective tissue (epimysium)

4. epimysium is continuous wiht most superifical connective tissue sheath (fascia) that merge or taper down to become tendons

5. tendons attach muscle to bone or other part muscle moves

General muscle structure

1. whole muscle

2. fascicle

3. muscle fiber

4. myofibril

5. myofilament

Tendons

• 3 continuous layers of connective tissue inside skeletal muscle that merge and collect at the end of muscle

• ATTACHES MUSCLE TO BONE

5 main fascicle patterns/arragments

1. parallel muscle

2. convergent muscle

3. circular muscle

4. fusiform muscle

5. pennate muscle

Parallel muscle

• evenly spaced fascicles attached to a tendon about the same width as the muscle

• example: sartorious

Convergent Muscle

• broad at one end and uniformly tapers to a single tendon

• example: traingle muscles like the pectoralis major

Circular Muscle

• encircles a strucutre like the opening to the eye to close or constrict when it contracts

• refered to as sphincters

• example: orbicularis oculi

Fusiform Muscle

• thicker in the belly or middle and tapered at ends

• example: biceps brachii

Pennate Muscle

• muscel where the fibers and fascicles attach to the tendon at an angle so it resembles a feather

• 3 variations (unipennate, bipennate, multipennate)

Unipennate Muscle

• type of pennate muscle

• single tendon; fasicles feather out at an angle from only one side

• example: flexor pollicis longus

Bipennate Muscle

• type of pennate muscle

• single tendon; fascicles feather out at an angle from both sides of the tendon

• example: rectus femoris

Multipennate Muscle

• type of pennate muscle

• composed of several tendons; fascicle attachments look like several feathers joined together

• example: deltoid

3 basic functions of skeletal muscles

1. Muscle Tension: to contract and generate forc

2. Actions: ability to generate muscle tension allows skeletal muscle to produce body movements

3. Generate Heat: tension enables skeletal muscles to generate heat as the chemical energy of ATP is converted to mechanical energy of movement, producing heat as a waste product

4 ways to name muscles

1. size

2. location

3. structures they attach to

4. function

Muscles based on size

• longus

• brevis (short or brief)

• vastus (vast or broad)

Muscles based on location

• use directional & regionla anatomical terms

• superior/inferior

• medial/lateral

• profundus (deep)

• pectoralis minor

Muscles based on structures they attach to

example: sternocleidomastoid muscle (sternum,clavicle, mastoid process)

• shaving muscle

Muscles based on function

• flexors (bend)

• extensor (straighten/extend)

• levatators (lift/pull in)

• adductors (pull in)

• abductors (pull away)

4 functional groups of muscles

1. agonists

2. antagonist

3. synergists

4. fixators

Agonists

• AKA prime movers

• functoinal group of muscles that provide most of force requried for given movements

• usually one of the larger muscles spanning joint to be moved

Antagonist

• usually on opposite side of a joint from agonist partner

• tends to oppose and slow action for control. Needed for slower and graceful moves

Synergists

• muscles that work tgt with agonist

• help guide movement and make it smooth

Fixators

• muscles that hold bone in place to make movement more efficient

• reduces risk of injury

Muscle Origin

• part muscle attaches to that is more fixed

• example: biceps brachii attaches to scapula

Muscle insertion

• part muscle attaches to that moves

• example: radius of biceps brachii as it moves the radius

Example of how origin and insertion can switch for muscles that act on more than one joint

• iliopsoas attaches to pelvis and lower vertebral column and to femur

• femur is usually insertion but when we bend forward, femur is fixed and becomes origin

4 components of lever system in body movements

1. lever itself (bones)

2. load (object you are tyring to move or weight of body part mvoed)

3. force applied to lever to move the load (tension generated by muscles)

4. fulcrum, or hinge point, around where lever moves (joint at which movement occurs)

First class lever

• fulcrum in middle

• load and force on opposite sides

• example: atlanto-occipital joint (think of see-saw) and nodding the head

Second-class lever

• uncommon in body

• fulcrum at one end

• load in middle

• force at other end

• example: metatarsophalangeal joints (think of hand truck)- lifting body weight on toes

Third-Class Lever

• very common in body

• fulcrum at one end

• force in the middle

• load at the other end

• example: elbow joint (think of tongs holding object)- lifting a weight

Mechanical advantage

• lever system uses a small force to move a large load

• placing fulcrum close to load allows large load to be moved with a smaller force

Mechanical disadvantage

• lever system require greater force to move the load

• placing fulcrum farther from load requries greater force to move load

Muscle Strain

• results when muscle is put under more stretching or contractile force it can handle; tears and can range from a few torn muscle fibers to rupture of entire muscle

• symptoms: pain, no movement, swelling, bruising

• PRICE method for treatment: Protect from injury, Rest to allow healing, Ice and Compression for less inflammation, and Elevation to drain fluid away