Muscular System III (Upper Limb) Flashcards
Supraspinatus
- one of the fossa was called supraspinus fossa but it is the origin for the muscle supraspinatus - after originating the muscles fibers horizontally will travel laterally and pass below the acromion process and get inserted into the greater tubercle of humerus
◦ function: this muscle can abduct the shoulder - prime mover for abduction of the shoulder but only for the first 30 degrees
◦ nerve supply: supplied by direct branch from brachial plexus - when we contract this muscle there is a risk for this muscle and tendon to be rubbed against acromion - tendon of muscle can be pinched between acromion and greater tubercle humerus - overuse of this muscle will result in inflammation of the tendon muscle and you can get tendinitis of supraspinatus (painful)
What are the Upper Limb Regions?
- shoulder region is subdivided into smaller areas: pectoral area, scapular area, deltoid area (bring them together to make shoulder region)
- arm is between shoulder joint and elbow and forearm which is between elbow and wrist and hand which is below wrist
Infraspinatus
- below the spine you have another muscle called infraspinatus originating from infraspinous fossa - fibers are directed laterally and superiorly and insert to greater tubercle of humerus
◦ function and nerve supply: tendon of this muscle passes inferior (behind) to the joint so it is involved in lateral rotation - prime mover for lateral rotation - innervated by same nerve as before - direct branch from BP (can help in adduction)
Subscapularis
- going to anterior view we have a large shallow fossa called subscapular fossa - serves as origin for subscapularis muscle and it inserts on the lesser tubercle of humerus
◦ function and nerve supply: fibers are crossing the joint anteriorly - in front of joint - can help in adduction but that is not main function is medial rotation acting as a prime mover for medial rotation for gleno-humeral joint - another direct branch from brachial plexus
Deltoid
- deltoid describes shape - reverse triangle - base of muscle has wide origin - some fibers start from clavicle and some fibers are coming from acromion and has some posterior fibers coming from spine of scapula (big origin) - from all these 3 origin the muscles fibers converge to midpoint of lateral surface of shaft of humerus
- deltoid tuberosity if one insertion point - slight bony elevation located at the midpoint on the lateral surface of the shaft of the humerus
- function: most fibers cross your shoulder joint laterally so it is an abductor - bigger than supraspinatus so after 30 it takes over from 30-90 degrees - prime mover of abduction from 30-90 degrees
◦ nerve supply: direct branch coming from BP
What are the two muscular (fascial) compartments of the Arm Region?
- can identify two muscular (fascial) compartments
- cross section of arm - first layer is skin and deep to that you have a little bit of fat (superficial fascia ) and white one is deep fascia encirculating all muscles and it sends some thicker septum’s which will joint and attach to the humerus
- these extensions of deep fascia are known as intramuscular septum
- using the humerus and intramuscular septum on both sides you can identify two muscle groups: one is anterior compartment and other is posterior compartment
- know this: basis for putting muscles into certain compartments is not their attachment, not their function, not their physical location RATHER their nerve supply
- those supplied by same nerve are classified by the same compartment
- all muscles in anterior compartment in arm are supplied by musculo-cutaneous nerve (branch of BP)
- muscles in posterior compartment are supplied by the radial nerve
Biceps Brachii (two heads)
- long head originates from right above the glenoid fossa
- short head arises from this bony process - corocoid process
- two heads are merging and insert on the radial tubercle (bony elevation)
- muscles crosses two major joints as it crosses both your shoulder and your elbow
- for the elbow it crosses in front so it helps with flexion of the elbow - not prime mover for this
- function: prime mover for supination
- biceps helps in flexion of shoulder and elbow but prime mover for supination of the forearm
- nerve supply: innervated by musculo-cutaneous - anterior compartment
Brachialis
- deep to biceps and indicates its physical location - brachial means arm and it is located in anterior compartment
- originates from the shaft of the humerus
- after crossing anterior to elbow it inserts on ulnar tuberosity
- function: only crosses one joint (elbow) - so function is flexion of elbow acting as prime mover
- nerve supply is musculocutaneuous
Triceps Brachii (main muscle)
- 3 heads - long head which originates just below glenoid fossa, lateral head and medial head (covered by two heads)- not small just covered by the other two heads -> both lateral and medial head originate from shaft of humerus
- all 3 heads after merging together insert to this bony process - olecranon process on ulna
- function: the muscle passes behind your elbow so it is an extensor of your elbow and it is a prime mover
- nerve supply is radial nerve - posterior compartment
How many layers are the muscles divided into the anterior compartment of the forearm?
muscles are divided into three layers (superficial, intermediate, deep)
Where does most of the muscles in the anterior compartment originate from?
- superficial layer - majority of the muscles in anterior compartment originate from your medial epicondyle of humerus so form a common tendon known as common flexor tendon (white)
- most muscles in anterior compartment help with flexion of wrist and digits (not all) thus the name
- tendon shared by most of those muscles
Flexor Carpi Radialis
function (flex) carpi (carpus - wrist) radialis (on lateral side) - flexes the wrist (not the prime mover) -> nerve supply: median nerve
- origin is from medial epicondyle or common flexor tendon -> inserts on third and second metacarpal bones (crosses the wrist)
- muscles in the anterior compartment are innervated by median or ulnar nerve but most are median nerve
Pronator teres
pronates your forearm (teres means round - cross section is round) - origin is from common flexor tendon and inserts on the midpoint of shaft of radius - when it contracts it turns your radius pronating and nerve supply is median nerve
- muscles of anterior compartment give rise to tendon that cross the wrist- to increase efficiency of the tendons there is a thick band of connective tissue holding those tendons in place- flexor retinaculum
- if it was not there when you are trying to flex your wrist all those muscles could boy out - keeping them in place as the tendons wrap around out acting as a pulley
Intermediate Layer (1 muscle): Flexor digitorum superficialis
- flex the digits (superficial)
- origin is medial epicondyle and radius (big one)
- muscles passes in front of wrist and divides into four tendons that will be targeting digits 2-5 - do not end to thumb
- they are splitting and attaching to both side of middle phalanx (insertion)
- flex the wrist and it can help in flexion in some of the joints except the distal phalanx
- not prime mover but is powerful
- nerve supply median nerve
Flexor digitorum profundus (deep)
flexes your digits and it is sitting deeper than the previous one
- originating mostly from your ulna and divides into 4 tendons - tendons go to the same digits but this this time they go to the end to the distal phalanx
- can flex your wrist and all the joints in your digits - prime mover for both
- nerve supply because lateral half is median nerve and medial half have is innervated by ulnar nerve
Flexor pollicus longus
flexes thumb (two of them and this is the longer one
- origin: coming from radius - crosses the wrist reaches to the thumb and insertion is distal phalanx of the thumb - prime mover for flexion of your thumb
- nerve supply median nerve
Brachioradialis (interesting muscle)
- on the lateral side of the anterior compartment there is a muscle called brachioradialis
- coming from humerus and inserts to styloid process of radius
- muscle is crossing elbow anteriorly so it is a flexor but it is not in the anterior compartment because it is innervated by the radial nerve putting it in the posterior compartment
How many layers does the Posterior Compartment of the Forearm Have?
2 - superficial and deep muscles
Extensor Digitorum
- most of the muscles of the posterior compartment originate from lateral epicondyle so they share a tendon called common extensor tendon
- extensor digitorum - originates from lateral epicondyle (or common extensor tendon) which serves as origin for most of the muscles (nerve supply: radial nerve)
- passes behind your wrist and divides into 4 branches that will get into digits 2-5 - insertion will be middle and distal phalanges of those digits 2 and 5
- function: extending the wrist and digits as well so it is prime mover for extension of the wrist and digits
- extensor carpi ulnaris - helps in extension of wrist on the medial side of forearm
◦ coming from common extensor tendon and it attaches on the fifth metacarpal bone and nerve supply is radial nerve
Deep Muscles of Posterior Compartment of Forearm
- smaller muscles but very significant and clinically important muscles
- supinator - originates from both ulna and humerus (lateral epicondyle) and then it wraps around radius and attaches to the shaft of the radius
- so if the forearm is already pronated when this muscle contracts it can bring it back to supination hence the name (not prime mover - biceps was)
- innervated by radial nerve
- extensor pollicis longus - longer muscle that is going to extend the thumb - it originates from the ulna and going to distal phalanx - prime mover for extension of thumb - nerve supply is radial nerve
Muscles of the Hand can be Divided into 3 areas
- ulnar supplies majority of hand
muscles of the hand can be divided into 3 areas: - one group of muscles are moving your thumb referred to as thenar group muscles (at base of thumb) - originate from carpal bones and they insert two first metacarpal or proximal phalanx of the thumb - perform flexion, abduction or opposition (bringing tip of thumb against the other digits) - innervated my median nerve
- hypothenar group located at the base of the fifth finger and they arise from the carpal bones and insert to fifth metacarpal and proximal phalanx of the fifth finger (they can flex the fifth finger, abduct and opposition for that finger)
- lumbricals originates from the flexor digitorum profundus muscle and inserts on the dorsal digital expansion of fingers 2 to 5 - main function is to do flexion of metacarpophalangeal joints and extension of the interphalangeal joints of fingers 2-5 - innervated by the median and ulnar nerves
Interossei
- interossei (between metacarpals) - ulnar nerve
◦ palmar interossei - adduction
of fingers
◦ dorsal interossei - abduction
of fingers - dorsal interossei arise from the adjacent surfaces of metacarpals and inserts on dorsal digital expansion of fingers 2-4 - they do abduction of the metacarpal joints and extension of the interphalangeal joints of fingers 2-4
- palmar interossei arise from the palmar surfaces of the 2nd, 4th, and 5th metacarpals and insert on the dorsal digital expansion of fingers 2,4 and 5 - primary function is adduction of the metacarpal joints and extension of the interphalangeal joints of fingers 2,4 and 5
Axilla, Cuboidal Fossa and Carpel Tunnel
- pyramid between torso (trunk) and arm
- another transitional area is in front of elbow known as cuboidal fossa between arm and forearm
- carpal tunnel right in front of wrist between forearm and hands
