shoulder - bones, joints + muscles Flashcards
what three bones are responsible for attaching the upper limb to the trunk?
clavicle, scapula and humerus (upper arm bone)
clavicle -
what kind of bone is it?
what are its articulations?
its the shortest long bone in the body, and the only horizontal long bone
medial/sternal end (rough) articulates to manubrium of the sternum
lateral/acromial end (smooth) articulates to the acromion of the scapula
both ends have one facet, sternal vs acromial
clavicle - describe its borders?
surfaces?
has a posterior and anterior border.
the anterior border is convex for the medial 2/3s, and concave for the outer/lateral 1/3
name something unique about the clavicle
only bone connecting axial (trunk) skeleton to the appendicular skeleton
what are the borders, surfaces, angles, and processes of the scapular?
this is all obvious when you look at the bone - its a flat triangle so -
three borders (superior, lateral and medial)
Two surfaces (costal and dorsal)
Three angles (superior, inferior, lateral)
Three processes (spine, acromion for clavicle and coracoid - the one at the front by the glenoid cavity)
what is the glenoid cavity?
oval shaped area at the lateral angle of the scapula, where the humerus articulates to form the shoulder joint
describe the key features of the upper end of the humerus
from shoulder to elbow
upper end - spherical head - anatomical neck right below the head - then the surgical neck is a bit lower and is prone to fractures, also where the auxiliary nerve wraps
Shaft - has deltoid tuberosity, and radial groove for the radial nerve
what are the three fossa of the humerus?
at the lower end of the humerus there are the three fossa (indents):
- olecranon (posterior, but remember default position is palms outwards)
- radial (anterior)
- coronoid (anterior)
what are the muscles attaching the trunk and scapula?
superficial = trapezius and latissmus dorsi
deep = levator scapulae and rhomboid major
trapezius - description + action + innervation?
Description: Broad flat and triangular, superficial
Actions: The upper fibres of the trapezius elevate the scapula. The middle fibres retract the scapula and the lower fibres pull the scapula inferiorly
Innervation: accessory nerve
levator scapulae - description, action and innervation?
Description: small strap-like muscle, deep, goes from superior angle of scapula to transverse process of C1-C4 (shoulder to neck)
Action: elevates the scapula
Innervation: dorsal scapular nerve
Latissmus dorsi - description, action and innervation?
Description: lower part of back, superficial, the ‘climbers muscle’
Actions: Extends, adducts, and medially rotates the upper limb. (remember what anatomical stance is)
Innervation: Thoracodorsal nerve
rhomboid major - description, action and innervation?
Description: originates T2-T5, attaches to the medial border of scapula (shoulder to spine)
Action: retracts and rotates the scapula
Innervation: dorsal scapular nerve
what muscles attach the trunk and the arm?
anterior/pectoral muscles - pectoralis major and minor, serratus anterior, subclavius
posterior/deep muscles - deltoid, teres major
(plus the four rotator cuff muscles)
pectoralis major?
description: It islarge and fan-shaped
Function:Adducts and medially rotates the upper limb. The clavicular head also acts individually to flex the upper limb
Innervation:Lateral and medial pectoral nerves
pectoralis minor?
description: The pectoralis minor lies underneath the pectoralis major (inserts on corocoid process of the scapula)
Function:Stabilises the scapula by drawing it anteroinferiorly against the thoracic wall
Innervation:Medial pectoral nerve
serratus anterior?
description: The serratus anterior is located more laterally in the chest wall
Function:Rotates the scapula, allowing the arm to be raised over 90 degrees. It also holds the scapula against the ribcage
Innervation:Long thoracic nerve
what is ‘winging’ of the scapula?
When the serratus anterior is paralysed, which occurs when the nerve supply - long thoracic nerve - is damaged/affected. Looks like a wing as the medial border protrudes out of the back
subclavius?
description: the subclavius is small muscle, which is located directly underneath the clavicle, running horizontally
Function: Anchors and depresses the clavicle
Innervation: subclavian nerve
deltoid description, action of all three fibres, and innervation?
description: The deltoid muscle is shaped like an inverted triangle. It can be divided into an anterior, middle and posterior part
Actions:
Anterior fibres – flexion (moving arm foward) and medial rotation.
Posterior fibres – extension (moving arm behind you) and lateral rotation
Middle fibres – the major abductor of the arm, i.e. raising arm out to the side (takes over from the supraspinatus, which abducts the first 15 degrees)
Innervation: Axillary nerve
teres major?
description: I think its kind of midway down the back ish, horizontal
Actions: Adducts and extends at the shoulder, and medially rotates the arm
Innervation: Lower subscapular nerve
shoulder joint vs the shoulder girdle?
Shoulder joint = glenohumeral joint, humerus meeting the glenoid fossa of scapula, forming the glenoid cavity, a ball and socket synovial joint
shoulder girdle = scapula + clavicle
what kind of joint is the shoulder joint? why are ligaments needed?
the glenohumeral joint is a ball and socket synovial joint
the head of the humerus = bigger than the glenoid cavity = unstable joint = requires ligaments for support to prevent dislocation
what are the 7 possible movements of the shoulder joint?
Extension (upper limb backwards in sagittal plane)
Flexion (upper limb forwards in sagittal plane)
Abduction (upper limb away from midline in coronal plane)
Adduction
Internal rotation (rotation towards the midline, so that the thumb is pointing medially)
External rotation
Circumduction (moving the upper limb in a circle)
what muscles are responsible for extension in terms of shoulder joint?
Extension (upper limb backwards in sagittal plane) –
posterior deltoid, latissimus dorsi
assist by teres major
what muscles are responsible for flexion in terms of the shoulder joint?
.
Flexion (upper limb forwards in sagittal plane) –
pectoralis major, anterior deltoid
coracobrachialis and biceps short head weakly assist
what muscles are responsible for adduction in terms of the shoulder joint?
Adduction (upper limb towards midline in coronal plane) –
pectoralis major, latissimus dorsi biceps long, triceps short, teres major
what muscles are responsible for abduction in terms of the shoulder joint - this depends on how high in degrees
Abduction (upper limb away from midline in coronal plane):
The first 0-15 degrees of abduction is produced by the supraspinatus
The middle fibres of the deltoid are responsible for the next 15-90 degrees
Past 90 degrees, the scapula needs to be rotated to achieve abduction – that is carried out by the trapezius and serratus anterior
what muscles are responsible for medial/internal rotation in terms of the shoulder joint?
turning arm so thumb points inwards -
pectoralis major
anterior deltoid
latissimus dorsi
teres major
subscapularis
what muscles are responsible for external/lateral rotation in terms of the shoulder joint?
infraspinatus and teres minor muscles, with help from the posterior fibers of the deltoid muscle
what is the joint capsule - composition and function?
a fibrous sheath which encloses the structures of the joint
Extends from the anatomical neck of the humerus to the border of the glenoid fossa
it is lax – permitting greater mobility
The synovial membrane lines the inner surface of the joint capsule and produces synovial fluid to reduce friction between the articular surfaces
ligaments - what are the four ligaments of the shoulder joint, including where they attach and what part of the joint they stabilise/support?
Glenohumeral ligaments – extend from the humerus to the glenoid fossa
Stabilise the anterior aspect of the joint
Coracohumeral ligament – extends from the coracoid process to the greater tubercle of the humerus
It supports the superior part of the joint
Transverse humeral ligament – extends between the two tubercles of the humerus
Coracoacromial ligament – extends between the acromion and coracoid process of the scapula, forming an arch-like structure over the shoulder joint (coracoacromial arch)
This resists superior displacement of the humeral head
what are the rotator cuff muscles?
group of four muscles originating from the scapula and attaching to the humeral head, at resting they pull the humeral head into the glenoid fossa, stabilising the joint
from outer to inner, what structures stabilise the shoulder joint?
joint capsule - ligaments - rotator cuff muscles
what are the four rotator cuff muscles from top to bottom
supraspinatus
infraspinatus
subscapularis
teres minor (mostly posterior)
supraspinatus - actions and innervation?
Actions:
Abducts the arm 0-15, and assists deltoid for 15-90
Innervation:
Suprascapular nerve
infraspinatus - actions and innervation?
Actions:
Laterally rotates the arm
Innervation:
Suprascapular nerve
subscapularis - actions and innervation?
actions:
medially rotates the arm
innervation:
upper and lower subscapular nerves
teres minor - actions and innervation?
actions:
laterally rotates the arm
innervation:
axillary nerve
what are the four muscles of the arm? extensors vs flexors, including nerve supply
all located around the humerus, either flexors or extensors
flexors = biceps brachii, coracobrachialis, brachialis
all innervated by musculocutaneous nerve (brachialis also radial nerve)
extensors =
triceps brachii
innervated by radial nerve
biceps brachii - origins an insertion?
two heads
long head origin = supraglenoid tubercle of the scapula
short head original = coracoid process of the scapula
both insert at the radial tuberosity and the fascia of the forearm via the bicipital aponeurosis
biceps brachii - functions and innervation?
function = supination of the forearm + flexes the arm at elbow and shoulder
innervation = musculocutaneous nerve
coracobrachialis - origin and insertion?
lies deep to the biceps brachii (behind)
origins = coracoid process of the scapula
inserts = at the medial side of the humeral shaft (same level as deltoid tubercle)
coracobrachialis - functions and innervation?
function = flexion of the arm at shoulder (+assists adduction)
innervation = musculocutaneous nerve
brachialis - origin and insertion?
deep to the biceps brachii, but on the distal arm (lower arm)
origin = medial and lateral surfaces of the humeral shaft
inserts = ulnar tuberosity (just below elbow joint)
brachialis - function and innercation?
function = flexion at the elbow
innervation = musculocutaneous nerve + contributions from radial nerve
posterior compartment of the arm - triceps brachii
origins and insertion?
three heads, long, medial and lateral, medial being the deep one
origins:
long head = infraglenoid tubercle of the scapula
lateral head = on the humerus just superior to the radial groove
medial head = the humerus but just inferior to the radial groove
insertion - they converge into one tendon inserting into the olecranon fossa of the ulna
triceps brachii - function and innervation?
function = extension of the arm at the elbow
innervation = radial nerve
what are the three major nerves of the arm and their innervations?
axillary = teres minor and deltoid muscles
musculocutaneous = three anterior compartment muscles
radial = its wrapped around the surgical neck of the humerus and innervates the triceps (posterior compartment) and contributes to the brachialis
(there is also the ulnar nerve)
the three main nerves of the arm arise from the brachial plexus - what is it?
The brachial plexus is a network of nerve fibres that supplies the skin and musculature of the upper limb. It begins in the root of the neck, passes through the axilla, and runs through the entire upper extremity.
The plexus is formed by the anterior rami (divisions) of cervical spinal nerves C5, C6, C7 and C8, and the first thoracic spinal nerve, T1
what is the blood supply to the upper limb?
right:
aortic arch - brachiocephalic trunk - right subclavian - right axillary - right brachial - right radial and right ulnar - digital arteries
left:
aortic arch - left subclavian - L axillary - L brachial - L radial and L ulnar - digital arteries
(the same except left subclavian arises directly from the aortic arch, there is no brachiocephalic trunk)
