2- Bones and the Skeleton Flashcards
How are the upper limbs attached to the axial skeleton?
Sternoclavicular joint attaches medial aspect of clavicle to the manubrium of the sternum.
What is apposition, reposition, and opposition?
Apposition- touching of 5th digit to thumb
Reposition- Release of fingers
Opposition- gripping with fingers
What are some roles/facts of the clavicle?
Joins axial skeleton to upper limbs
Sternoclavicular ligaments are so strong, bone will break before disjoining
Transmits weight
Acts as a strut
Slight sigmoid curves (concave laterally, convex medially)
What are key features of the scapula?
Acromion- lateral, articulates with clavicle to form acromioclavicular joint.
Coracoid process- Used for muscular/ligament attachments
Spine- sharp ridge, posterior, splits scapula into supraspinous and infraspinous fossa
Glenoid Cavity- Lateral, articulates with humerus
Subscapular Fossa- Anterior surface where muscles pass over.
What muscles hold the scapula in place?
Trapezius Levator Scapula Rhomboid Major/Minor Serratus Anterior Pectoralis Minor
What is protraction/retraction of the scapula?
Protraction- pushing a door open, separating the scapula
Retraction- pulling scapulae together.
What muscles make up the posterior wall of the axilla?
Subscapularis, Teres major, Latissimus Dorsi, and long head of triceps brachii
What muscles make up the anterior wall of the axilla?
Pectoral Muscles
What landmarks form the lateral and medial borders of the axilla?
Medial- Upper thoracic wall and Serratus Anterior
Lateral- Intertubercular sulcus of humerus and muscles
What is the origin and insertion of pectoralis major?
Origin- Anterior, medial clavicle, sternum, upper 6 costal cartilage, aponeurosis of external oblique (fibrous tissue, takes place of tendon in flat muscle)
Insertion- Crest of greater tubercle and lateral lip of intertubercle groove (lower fibres form U-shaped tendon)
What action does pectoralis major cause?
Protracts and depresses scapula
Adducts and medially rotates humerus
Clavicular head can flex humerus
Sternocostal head can extend humerus
What nerve(s) innervate pectoralis major?
Medial and Lateral pectoral nerves coming from brachial plexus
What is the origin and insertion of pectoralis minor?
Origin- 3-5th ribs near costochondral junction
Insertion- Medial border and superior surface of the coracoid process of the scapula
What are the actions caused by pectoralis minor?
Depresses shoulder
Scapular protraction
Raises ribs when scapula is fixed
What nerve(s) innervate pectoralis minor?
medial pectoral nerve
What nerves form the brachial plexus?
Ventral rami of C5-T1 spinal nerve roots
C4 and T2 have minor contributions
What nerve fibres form the superior trunk of the brachial plexus?
C5 and C6
What nerve fibres form the middle trunk of the brachial plexus?
C7
What nerve fibres form the inferior trunk of the brachial plexus?
C8 and T1
What divisions form the lateral cord of the brachial plexus?
Anterior divisions of the superior (C5/6) and middle (C7) trunks
What divisions form the posterior cord of the brachial plexus?
Posterior divisions of the superior (C5/6), middle (C7), and inferior (C8/T1) trunks
What divisions form the medial cord of the brachial plexus?
Anterior division of the inferior (C8/T1) trunk
What cords and roots form the musculocutaneous terminal root of the brachial plexus?
Lateral cord of anterior divisions of the superior (C5/6) and middle (C7) trunks
What nerve roots form the musculocutaneous terminal root of the brachial plexus?
C5/6/7
What nerve roots form the axillary terminal root of the brachial plexus?
C5/6
What nerve roots form the median terminal root of the brachial plexus?
C5*/C6/7/8/T1
What nerve roots form the radial terminal root of the brachial plexus?
C5/6/7/8/T1
What nerve roots form the ulnar terminal root of the brachial plexus?
C8/T1
What muscles and skin does the anterior division of the brachial plexus supply?
Flexor muscles of upper limb
Skin on anterior surface of the upper limb
What muscles and skin does the posterior division of the brachial plexus supply?
Extensor muscles and skin on the back of the upper limb
Where do the divisions of the brachial plexus lay, and how many are there?
6 divisions (3 anterior, 3 posterior) Pass deep to middle 1/3rd of clavicle into the apex of the axilla
Where do the cords of the brachial plexus lay, and how many are there?
3 cords (named based on location to axillary artery) Initially lie posterior to axillary artery
Where are the terminal branches of the brachial plexus found?
At the lower border of pectoralis minor
What muscles does the musculocutaneous nerve supply?
Corachobrachialis muscle, biceps brachii, brachialis
What muscles does the lateral and median roots of the median nerve supply?
forearm flexor muscles and thenar eminence (muscles of the thumb on the anterior surface)
What muscles does the ulnar nerve supply?
intrinsic muscles of the hand
What muscles does the radial nerve supply?
All extensors (it is the largest) Medial and Lateral heads of triceps
What muscles does the axillary nerve supply?
Teres minor and deltoid
What are the main supraclavicular branches of the brachial plexus as well as their origin and the muscle they innervate?
Dorsal Scapular- ramus of C5, supplies rhomboids and levator scapula
Long thoracic- ventral rami of C5/6/7, supplies serratus anterior
Suprascapular- superior trunk, supplies supraspinatus and infraspinatus
What are the main infraclavicular branches of the brachial plexus as well as their origin and the muscle they innervate?
Medial and Lateral Pectoral- From medial and lateral cords, pectoral major for both, and minor for medial nerve
Upper and Lower Subscapular- From posterior cord, supplies subscapularis and teres major
Thoracodorsal- From posterior cord, supplies latissumus dorsi
What are some injuries to the brachial plexus?
Crutch Palsy- Impacts radial nerve impacting extensor muscles
Radial Nerve Damage- error when performing intramuscular injections to deltoid causing drop wrist (can’t extend hand)
Carpel Tunnel- Median nerve damage caused by overuse of wrist (repetition) causing swelling of carpel, numbness, tingling, pain in palm and fingers
What type of joint is the sternoclavicular joint?
Saddle Joint, although acts more like a Ball and socket synovial joint
What ligaments are found at the sternoclavicular joint?
Sternoclavicular ligament bonding medial clavicle to manubrium
Interclavicular ligament attaches the medial aspects of the clavicles
Costoclavicular ligament joins clavicle to 1st costal cartilage
What ligaments help form the acromioclavicular joint?
Coracoclavicular ligament
Acromioclavicular ligament
Coracoacromial ligament
What type of joint is the acromioclavicular joint?
Gliding synovial joint
What type of joint is the glenohumeral joint?
Multiaxial ball and socket joint
Limited stability as it is a poor fit
What is the purpose of the rotator cuff muscles?
Stabilize glenohumeral joint while allowing for free movement (as opposed to ligaments)
The humerus is 4x too large for the glenoid cavity
What is the glenoid labrum
fibrocartilage ring that runs around perimeter of glenoid cavity helping to extend it and increase hold on humerus
What side of the humerus are the greater and lesser tubercles found, and which is most lateral?
Anterior
Greater is more lateral
Where is the glenohumeral capsule attached, and what factor impacts injury of it?
Proximally at scapula beyond the supraglenoid tubercle as well as the margin of the labrum and distally at the anatomical neck of the humerus
The inferior aspect is quite loose and thus a common sight of dislocation
What are bursae?
They reduce friction where one structure commonly moves over another
What bursae are found at the glenohumeral joint?
Subacromial
Subscapular
Subdeltoid
Subcoracoid
What is the pectoral girdle?
Scapula and clavicle
What muscles aid in flexion of the upper limb?
Pectoralis Major (clavicular part) Anterior fibres of Deltoid, assisted by biceps brachii and coracobrachialis
What muscles aid in extension of the upper limb?
Posterior fibres of Lat Dorsi and Deltoid
Aided by scapular rotation by trapezius and levator scapula
What muscles aid in the upper limb return extension to anatomical position following flexion?
Latissimus Dorsi, Teres Major, Pectoralis Major (sternal head)
Aided by rhomboid major and pectoralis minor
What muscles aid in the abduction of the upper limb?
First 15-30- Supraspinatus
30-horizontal- Deltoid (it cannot initiate abduction though)
Horizontal to over head- Serratus anterior (lower fibres) and trapezius (upper fibres)
What muscles aid in the adduction of the upper limbs?
Gravity
Latissimus Dorsi
Lowest sternocostal fibres of Pec Major (until arm is horizontal)
What muscles aid in medial rotation of the upper limbs?
Pectoralis Major
Latissimus Dorsi
Subscapularis
Teres Major
What muscles aid in the lateral rotation of the upper limbs?
Infraspinatus
Deltoid (posterior fibres)
Teres minor
What muscles form the rotator cuff?
Supraspinatus
Infraspinatus
Teres minor
Subscapularis
What is the origin, insertion, action, and innervation of teres minor?
Origin-Lateral margin of scapula
Insertion- Posterior greater tubercle of humerus
Action- lateral rotation of humerus and stabilisation
Innervation- Axillary nerve
What is the origin, insertion, action, and innervation of infraspinatus?
Origin- Infraspinatus fossa of medial scapula
Insertion- Posterior superior greater tubercle of humerus
Action- Lateral rotation of humerus and stabilization
Innervation- suprascapular nerve
What is the origin, insertion, action, and innervation of supraspinatus?
Origin- Supraspinatus fossa of scapula
Insertion- superior greater tubercle of humerus
Action- abduction (first 15 degrees), and stabilization
Innervation- suprascapular nerve (upper trunk)
What is the origin, insertion, action, and innervation of subscapularis?
Origin- Subscapular fossa of scapula
Insertion- Lesser tubercle of humerus
Action- Medial rotation of humerus, stabilization
Innervation- upper/lower subscapular nerves (posterior cord)
What is the origin, insertion, action, and innervation of serratus anterior?
Origin- Lateral aspect of ribs 1-8th
Insertion- Anterior length of medial border of scapula
Action- Protraction of scapula
Innervation- Long thoracic nerve (of C5/6/7)
What are common shoulder injuries?
Dislocation- Most frequent (tears ligaments and articular capsule)
Rotator Cuff Injury- Tear supraspinatus tendon, common when using limb above horizontal (swimming)
Axillary Nerve Injury- Injured with dislocations of humeral head. Paralysis of deltoid and loss of sensation in small area of skin over deltoid
Which nerve travels close to the shaft of the humerus between the lateral and medial heads of the triceps?
Radial
What is the name of the gap located between teres major and minor, humerus, and long head of the triceps, through which the axillary nerve travels?
Quadrangular space
Which muscles can rotate the arm laterally?
Infraspinatus and teres minor
What part of the trapezius has a role in rotating (tilting) the scapula so that the inferior angle swings laterally, and, what is it needed for?
Superior (descending) fibres
Aids in elevation of upper limb above head
Where on the scapula does the levator scapulae attach?
Superior angle at medial aspect of scapula
Which muscle is needed for starting arm abduction from the anatomical position?
Supraspinatus
What actions does the latissimus dorsi muscle effect on the shoulder joint?
Adduction, extension, and medial rotation
What is the name of the fascial layer that envelops the muscles which are part of the erector spinae?
Thoraco-lumbar fascia
Which muscle(s) are (is) located immediately deep to the trapezius and connects vertebral spinous processes to the medial margins of the scapulae?
Rhomboids
What factors control osteoblastic proliferation and differentiation?
Wnt, Hedgehog, BMP (Specialization into osteoprogenitor)
BMP, Transforming Growth Factor-beta (differentiation into pre-osteoblast, and later for matrix maturation into mature osteoblast)
Fibroblast Growth Factor, IGF
CBFA1- activation of osteoblast
What factors regulate osteoclast formation and activity?
E2, glucocorticoids, PTH, 1.25 D3, IL-1, TNFa, IFNy, RANKL
What factor(s) does an osteoblastic cell release that lead to or prevent differentiation of a pre-fusion osteoclast into a mature osteoclast?
RANKL has activating effect
OPG has suppressing effect
We can regulate this to cause more or less bone resorption via osteoclast activity
What hormone do osteocytes release in quiescent bone surfaces, and what does this hormone act on?
Sclerostin is released to inhibit Wnt signalling, preventing osteoblast proliferation
How does a bone fracture change osteocyte activity?
Osteocyte near crack undergo apoptosis and stop releasing sclerostin, which then allows for Wnt signalling to pre-osteoblasts for proliferation and differentiation into mature osteoblasts
How are stromal cells impacted in terms of sclerostin levels following a fracture?
Sclerostin release is inhibited and IL-1 factors stimulate the stromal cells to secrete Macrophage Colony-Stimulating Factor which helps generate pre-osteoclasts.
What hormone regulates osteoclast lifespan?
Oestrogen
How is osteoclast activation stopped following the 2 week period of bone resorption during fracture repair?
Pre-osteoblasts mature into osteoblasts that stop expressing RANKL and secrete Osteoprotegrin which binds RANKL of existing pre-osteoblasts, blocking the binding/activation of other pre-osteoclasts
How do pre-osteoblasts aid in healing of a fracture, start with RANKL expression?
Pre-osteoblasts express RANKL which binds RANK on pre-osteoclasts, causing pre-osteoclast to enlarge and fuse with mature osteoclasts.
Osteoclast binds bone matrix using integrins and secrete acid/cathepsin K to resorb the bone (takes about 2 weeks), followed by osteoclast apoptosis.
Pre-osteoblasts mature into osteoblasts (RANKL expression stops), that line the resorbed cavity and secrete osteoid which becomes mineralized and reforms bone in 3-4 months.
Some osteoblasts differentiate into osteocytes and some into lining cells.
What are some systemic modulators inhibiting bone remodeling?
Oestrogens, androgens, progesterone, calcitonin.