Chapter 10: The Muscular System Flashcards
7 different ways/criteria that is used when naming a skeletal muscle
- shape
- location
- size
- direction of muscle fibers or fascicles
- number of origins
- location of attachments
- muscle action
Naming criteria: muscle location
- bone or body region with which muscle is associated
- ex. temporalis (over temporal bone)
Naming criteria: muscle shape
- distinctive shapes
- ex. deltoid muscle (deltoid = triangle)
Naming criteria: Muscle size
- maximus (largest)
- minimus (smallest)
- longus (longest
Naming criteria: Direction of muscle fibers or fascicles
- ex. rectus (fibers run straight)
- transversus (fibers run at right angles)
- oblique (fibers run at angles to imaginary defined axis)
Naming criteria: number of origins
- ex. biceps (two origins)
- triceps (three origins)
Naming criteria: Location of attachments
- named according to point of origins and insertion (origin is first part of name)
- ex. sternocleidomastoid attaches to sternum and clavicle
- origin on sternum and clavicle (sternocleido-)
- insertion on mastoid process (-mastoid)
Naming criteria: muscle action
- named for action they produce
- ex. flexor (causes flexion)
- extensor (causes extension)
How else are muscles named?
- several criteria can be combined
- extensor carpi radialis longus- extensor (extends) carpi (wrist) radialis (radius) longus (length is long)
Epicranius: general
- epi = over; cran = skull
- 2 part muscle with distinct anterior and posterior positions
- epicranial aponeurosis (connective tissue sheath that connects muscle to bone) connects 2 bellies
2 parts of epicranius
- frontal belly (anterior)
- Occipital belly (posterior)
2 parts of epicranius: frontal belly
- anterior
- O: epicranial aponeurosis
- I: skin of eyebrows and root of nose
- Action: raises eyebrows
2 parts of epicranius: Occipital belly
- posterior
- O: occipital and temporal bones
- I: epicranial aponeurosis
- action: pulls scalp posteriorily
Orbicularis oris
muscle of lips
Orbicularis oris: action
closes lips, purses and protrudes lips
Buccinator
- thin, horizontal cheek muscle
- principal muscle of cheek, deep to masseter
Buccinator: action
- compresses cheek (for whistling and sucking- important for infant feeding)
- also important during chewing
Suprahyoid muscles
- 4 deep muscles involved in swallowing
- form floor of oral cavity
- anchor tongue
Suprahyoid muscles: what structures do these muscles move
- elevate hyoid bone
- move larynx during swallowing
Infrahyoid muscles
4 straplike muscles
Infrahyoid muscles: what structures do these muscles move
- depress hyoid bone and larynx during swallowing and speaking
Pectoralis major
large, fan-shape, anterosuperior chest
Pectoralis major: what joint does it cross and what is its primary action
- crosses shoulder (glenohumeral) joint
- action: prime mover of arm adduction; flexion and medial rotation of arm
Latissimus dorsi
- posterior muscle
- broad, flat, triangular, lower back
- O: lower 6 thoracic vertebrae, lumbar vertebrae, iliac crest
- I: medical humerus (axilla area)
Latissimus dorsi: what joint does it cross and what is its primary action
- crosses the shoulder (glenohumeral) joint
- action: prime mover of arm extension; prime mover of arm adduction (powerful); medially rotates arm
- important during hammering, swimming, rowing, with arms extended upwards: pull body upwards- chin-ups
Deltoid
thick, multipennate, forms rounded shoulder (anterior to posterior around shoulder)
Deltoid: what joint does it cross and what is its primary action
- crosses the shoulder (glenohumeral) joint
- action: prime mover of arm abduction when all fibers contract simultaneously; antagonist of pectoralis major and latissimus dorsi (arm abductors)
- anterior fibers: prime mover of arm flexion, rotate arm medially (become synergist of pectoralis major)
- posterior fibers: prime mover of arm extension, lateral rotation
Erector spinae
3 muscles: iliocostalis (lateral), longissimus (intermediate), spinalis (medial)
Erector spinae: what happens if this muscle group is damaged
- lifting a load or moving suddenly from bent-over position can injure erector spinae muscle
- muscles can easily begin spasming after a back injury
Abdominal wall muscles: identify the one that is most important during mobility
- transversus abdominis: deepest abdominal muscle
- fibers run horizontally
- action: compress abdominal content
- when 4 abdominal muscles contract simultaneously they compress abdominal content and increase intra-abdominal pressure
- if airway closed this helps with urination, defecation, childbirth, sneezing, coughing, and burping
Rotator cuff muscles
- synergists and fixators
- O: scapula
- I: humerus
- main function: reinforce capsule, prevent dislocation of humerus
Rotator cuff muscles: what muscles are in this group
- Supraspinatus: abduction of arm
- Infraspinatus: prime mover for lateral arm rotation
- Teres minor: prime mover for medial arm rotation
- Subscapularis: prime mover for medial arm rotation
Triceps brachii
- only muscle of posterior arm compartment
- large fleshy, three-headed origin
- O: scapula, humerus x2 heads
- I: olecranon of ulna
Triceps brachii: primary action
prime mover of forearm extension (powerful) antagonist of forearm flexors
Biceps brachii
two-headed muscle
Biceps brachii: primary actino
- Prime mover of elbow flexion and supination of forearm
- bulges when forearm is flexed
Brachialas
- strongest arm flexor
- deep to and stronger than biceps brachii
Brachialis: primary action
major flexor of forearm, prime mover of elbow flexion
Hamstring Muscles
- fleshy, cross both hip and knee joint
- pulled hamstring = common sports injury
Hamstring muscles- what muscles are in this group
- Biceps femoris (I: fibula and tibia); has 2 heads (biceps)
- Semitendinosus (I: upper tibial shaft)
- Semimembranosus (I: tibia and femur)
Hamstring muscles features
- all have common origin: ischial tuberosity
- prime movers of thigh extension and knee flexion
Sartorius
- longest muscle in the body
- straplike, runs obliquely across anterior surface
- crosses hip and knee joint
- O: iliac spine (pelvis)
- I: medial aspect of tibia
- Actions: flex, abduct, laterally rotate thigh
Sartorius: what sitting position is it used to create
helps produce the cross-legged position
Gastrocnemius
- has 2 heads
- action = plantar flexion
Gastrocnemius: insertion
- Instersts into posterior calcaneus via calcaneal tendon
- calcaneal tendon = achilles tendon, largest tendon in the body
Respiratory muscles: diaphragm: primary action
prime mover of inspiration (breathing in), flattens on contraction
* most important muscle of inspiration
* forms partition between thoracic and abdominopelvic cavities
Respiratory muscles: diaphragm: what happens when it is relaxed/contracts
Relaxed: dome shaped
When contracted: moves inferiorly and flattens to increase thoracic cavity volume (this action pulls air into lungs)
Respiratory muscles: External and internal intercostals: action
pulls ribs toward one another, important in inspiration and forced exhalation
External and internal intercostals: location
- between ribs
- external intercostals: superficial to internal intercostals. fibers run obliquely (downward and anteriorly)
- internal intercostals: fibers run at right angles to external intercostals, downward and posteriorly
- run in opposite directions
External and internal intercostals: what do they connect
connects a superior rib to inferior rib
What is considered the most powerful muscle in the body
quadriceps femoris
