gross- upper limb (osce I) Flashcards
which bones are part of the pectoral girdle?
clavicle & scapula
axial & appendicular skeleton
axial skeleton: made up of bones that form the body’s axial skeleton (ribs, skull, spine)
appendicular skeleton: made up of bones that attach to the axial skeleton
where does the clavicle attach on both sides (ends of medial and lateral sides)?
medial side attaches to the sternum
lateral side attaches to the acromion process
side determination of the clavicle
LATERAL END → flat
MEDIAL END → large & quadrilateral
The shaft is slightly curved, so that it is:
Convex forward (comes out) in its medial 2/3
Concave forward (goes in) in its lateral 1/3
Inferior surface is grooved longitudinally in the middle 1/3rd (posterior side on top is smooth and inferior bottom side has a groove)
4 surfaces of the medial end of the clavicle + what muscles attach there
anterior (convex forward): origin of the pectoralis major
posterior: origin of the sternohyoid muscle (hyoid= neck)
superior: insertion of the clavicular head of sternocleidomastoid (when you clench jaw and move head)
inferior: insertion of the subclavius muscle (attached to subclavian groove)
medial is rounded so has 4 surfaces but lateral is flat and only has 2
2 borders and 2 surfaces of the lateral end of the clavicle + their muscle attachments
superior and inferior surfaces
anterior border (concave): origin of the deltoid muscle
posterior border (convex): insertion of the trapezius muscle
bony landmarks of the clavicle
- conoid tubercle that is a bump on the bottom (inferior) of the lateral side and attaches the coracoclavicular ligament
- trapezoid ridge which is next to the conoid tubercle and attaches the coracoclavicular ligament
- subclavian groove on the inferior side of medial part
- oval impression at the inferior surface of the medial side that attaches the costoclavicular ligament (connects clavicle to first rib)
coracoclavicular ligament
has 2 parts (trapezoid ridge & conoid tubercle) on clavicle and connects clavicle to coracoid process of scapula
walls/boundaries of apex & base in axilla (armpit)
pyramidal shape where apex is the top:
- anterior bordered by the posterior surface of clavicle
- posterior bordered by superior border of scapula and medial aspect of coracoid process
- medial bounded by outer border of 1st rid
base: formed by skin, superficial and axillary fascia
muscle attachments on the walls of axilla
Anterior wall: Pectoralis major, subclavius (below clavicle) & pectoralis minor
Posterior wall: subscapularis, latissimus dorsi & teres major
Medial wall: upper 4-5 ribs, intercostal spaces covered by serratus anterior
Lateral wall: Coracobrachialis, biceps brachi in the bicipital groove of humerus
4 contents of the axilla
- axillary artery: & branches, supply blood to the upper limb
- axillary vein: & tributaries, drain blood from the upper limb
- axillary lymph nodes & vessels: drain lymph from the upper limb
- brachial plexus: important nerve network that innervates the upper limb
contents of axilla are embedded in fat
axillary vein is always ____ to the axillary artery
medial
parts of the scapula (surfaces, borders, processes)
- two surfaces (anterior, posterior)
- three borders (superior, lateral, medial)
- three angles (superior, inferior, lateral)
- three processes (spine, acromion, coracoid)
side determination of the scapula
- Glenoid cavity located laterally (towards the outside)
- Spine goes on the dorsal/posterior side
- Costal/Anterior surface is concave (goes inwards) to fit into the concave chest wall
- Lateral border is the thickest border (goes towards the outside)
bony landmarks of the scapula
- subscapular fossa: marked by 3 longitudinal ridges (where the ribs fit) on the anterior/coastal surface
- spine on the posterior end that divides into supraspinous fossa (above the spine) and infraspinous fossa (below the spine)
- superior border is at the top and has the suprascapular notch
- medial border is all along the medial side
- lateral border is all along the lateral side and is thicker, with the infraglenoid tubercle at the top of it
- 3 angles as well: superior, inferior, lateral
- supraglenoid tubercle is on top of the glenoid cavity
- spine has lower and upper lips
- acromion process is at the end of the spine and is bigger and fatter
- coracoid process (looks like crows beak)
what muscle attaches to the subscapular fossa of the scapula?
subscapularis
what muscle attaches to the spine / are related to the spine of the scapula?
trapezius → inserts along upper lip of the spine
deltoid → originates from lower lip of spine
supraspinatus → fills most of supraspinous fossa
infraspinatus → covers most of infraspinatous fossa
which muscles hit the medial border of the scapula?
levator scapulae → attaches right below the superior angle on the posterior side of scapula (think elevator that pulls up towards neck)
rhomboid minor→ attaches along the upper medial border, below levator scapulae
Rhomboid major→ attaches below the rhomboid minor and takes up much more space
serratus anterior→ inserts along the entire medial border but on the anterior end (end facing the person)
what muscles attach to the lateral border of the scapula?
teres minor → attaches to the upper lateral border (an artery goes through the minor too)
teres major → attaches to the lower lateral border
what muscle attaches to the inferior angle of the scapula?
latissimus dorsi
kinda just zooms past
which muscles attach at the glenoid cavity of the scapula?
long head of biceps (brachii) → originates from supraglenoid tubercle
long head of triceps (brachii) → originates from infraglenoid tubercle
what muscles attach at the coracoid process of the scapula?
pectoralis minor → inserts on the medial surface of coracoid
coracobrachialis→ originates from the coracoid (like the circle part of the beak looking thing)
short head of biceps → coracoid
what muscles attach to the acromion process of the scapula?
trapezius → inserts on the upper side of the acromion
deltoid → originates from the lateral acromion
side determination of humerus
- head (rounded part) is directed medially, backwards and upwards (bc the scapula is kind of backwards) - so head should face the body side
- olecranon fossa is on the posterior side (back)
-
bony landmarks of the upper end of the humerus
- head: articulates with the glenoid cavity of the scapula to form the shoulder joint
- anatomical neck: imaginary line that support head from the rest of the upper end
- 2 tubercles: greater tubercle (on the lateral lip of bicipital groove) and lesser tubercle (on the medial lip, also is smaller)
- groove b/w the 2 tubercles is called the bicipital groove (bc biceps tendon passes through it) or intertubercular sulcus
- surgical neck: imaginary line separating the upper end of humerus from the shaft
bony landmarks of the shaft of the humerus
has 3 borders & 3 surfaces
BORDERS:
1. Anterior border: follow the lateral lip of bicipital groove down (the greater tubercle)
- Medial border: start from the medial epicondyle (the fatter one) and go up to the middle of the bicipital groove (it rotates its way around)
- Lateral border: prominent only from the bottom, start from bottom (lateral epicondyle) and go up until you lose it
SURFACES:
1. Anteromedial surface: b/w anterior & lateral borders (marked by V shaped deltoid tuberosity)
- Anterolateral surface: kind of all throughout the bicipital groove but rotates as it goes down
- Posterior surface: middle one-third is crossed by the radial groove (which carries the radial nerve as well)
full path of the biceps brachii
- Long head originates from the supraglenoid tubercle of scapula
- Short head originates from the coracoid process of the scapula
- The long head exits shoulder joint, passes through the bicipital groove, and is held in place by the transverse humeral ligament.
- Both heads merge into the biceps belly in the upper arm.
- The biceps tendon inserts into the radial tuberosity (main insertion and is on the radial bone) and extends as the bicipital aponeurosis (sheet-like structure that blends with the deep fascia of the forearm, helping protect underlying structures like arteries and nerves)
It is innervated (supplied w nerves) by the musculocutaneous nerve (C5-C7, which comes from brachial plexus).
bony landmarks of the lower end of the humerus
- medial & lateral epicondyle: medial is a bit rounded and fatter while lateral is more flatter and inwards
- medial & lateral supracondylar ridge: parts directly above the epicondyles for both, respectively
- trochlea: on the medial side, pulley-shaped structure (has the little line in the middle and longer than capitulum)- only on anterior side
- capitulum: on the lateral side, rounded, ball-like structure (only on anterior side)
- coronoid fossa: the hole right above the trochlea
- radial fossa: hole right above the capitulum
- olecranon fossa: the big hole on the back (posterior side)
muscle attachments of the upper part (proximal end) of the humerus?
SITS Muscles (rotator cuff):
- Supraspinatus (originates from scapula) → inserts at uppermost impression on greater tubercle
- Infraspinatus (originates from scapula) → inserts on middle impression on greater tubercle
- Teres Minor (originates from scapula) → inserts on lower impression on greater tubercle
- Subscapularis (originates from scapula) → inserts on lesser tubercle
Lady b/w 2 majors:
- Pectoralis Major → Inserts on the lateral lip of bicipital groove
- Latissimus Dorsi → Inserts in the bicipital groove
- Teres Major → Inserts on the medial lip of bicipital groove
muscle attachments of the shaft of the humerus
deltoid → inserts at the deltoid tuberosity (V ridge)
medial head of triceps → originate from radial groove
coracobrachialis → inserts at the middle of the medial border (this one is coming from up- from the coracoid process and then goes down to insert into the middle of the humerus)
brachialis → originates from lower half of anteromedial & anterolateral surfaces (this one kinda starts from the middle of the shaft and then goes down)
what makes the 3 cords of the brachial plexus?
Lateral Cord → formed by anterior divisions of the upper and middle trunks (C5-C7)
Medial Cord → formed by anterior division of the lower trunk (C8-T1)
Posterior Cord → formed by posterior divisions of all three trunks (upper, middle, and lower)
muscle attachment of the lower part (distal end) of the humerus
brachioradialis → originates from the upper 2/3 of the lateral supracondylar ridge
flexors → forearm flexor muscles originate from the medial epicondyle
extensors → forearm extensor muscles originate from the lateral epicondyle
lateral head of triceps originates from the upper posterior surface- above the radial groove (but this should be in shaft idk why its here)
boundaries of the breast (horizontally & vertically)
vertically: on the chest wall, extends from 2nd to 6th rib
horizontally: extends from sternum (midline of the chest) to axilla (armpit region)
anatomical features/parts of the external part of breast
- nipple: raised, pigmented projection in the center of the breast, contains 15-20 lactiferous duct openings that allow milk to exit during breastfeeding
- areola: circular pigmented area surrounding the nipple
- contains montgomery glands (areolar glands) that produce an oily secretion to prevent the nipples from getting cracked & work as anti-infect ants
axillary tail (tail of spence): only part that lies deep in the fascia (pierces deep fascia at lower border of pectoralis major) small portion of breast tissue that extends into the armpit
breast changes in old age
atrophy of breasts starts
with aging, suspensory ligaments stretch, leading to breast sagging (ptosis).
thinner skin and less elasticity
description/details about the breast
- present in superficial fascia right below the skin, and sits on the pectoralis major
same in males and immature females - modified sweat gland, is an accessory gland b/c not essential for survival but has a special function
- like other glands, connective tissue & duct system is present
- compound tubuloacinar (compound: gland has multiple branches, tubuloacinar: has both tube-like [ducts] & sac-like [alveoli that produce milk] structures)
increase in size of breasts is mainly due to what
increase in deposition of fat
- estrogen increases = fat tissue accumulates in breast
- the actual milk producing glands stay small until a woman gets pregnant or starts breastfeeding
breast anatomy: lobes, lobules, alveoli
alveoli → lobules → lobes
- lobes: 15-20 lobes arranged in a radial pattern (like flower petals)
- lobules: inside the lobes, smaller compartments that contain the actual milk-producing glands
- alveoli: inside lobules, small-grape like clusters of milk-secreting epithelial cells
- surrounded by myoepithelial cells that contract under influence of oxytocin to push milk out
significance of the quadrangular space
axillary nerve and posterior circumflex humeral vessels emerge through this space to reach their terminal destinations in the shoulder
quadrangular space: bounded:
above→ subscapularis & teres minor muscles, capsule of the shoulder joint
below → teres major muscle
medially → long head of triceps
laterally → surgical neck of humerus
importance of fibrous septa
keep infections localized and prevent them from spreading to other lobes in the breast
(they separate the different lobes)
breast anatomy: lactiferous ducts & ampulla
lactiferous ducts: smaller branched ducts from the lobules that merge to form a larger lactiferous duct for each lobe and carry milk to the nipple
near the nipple, this duct widens to form the lactiferous sinus (ampulla) that store milk temporarily before it exists through the nipple
each lobe has 1 lactiferous duct, but multiple lobules
anatomy of the breast: fibrous septa, retromammary space
fibrous septa (suspensory/cooper’s ligaments): separate lobules, space between the lobules, bands of connective tissue that extend from deep fascia of pectoralis major to skin of breast
- provide structural support (more dense in upper part of breast & less dense in lower part)
retromammary space: thin layer of loose connective tissue and fat located b/w breast and pectoralis major
- allows some movement of breast over chest
adipose tissue: fat that surrounds and fills up most of breast
breast and nipple changes during pregnancy
- influence of estrogen causes lactiferous ducts to grow rapidly and form more branches
- development of alveoli & glandular tissue: connective tissue (CT) spaces replaced with growing alveoli
-
increased blood supply (vascularity): breast becomes highly vascularized to support milk production/gland growth
- veins are also more visible on the surface of breast - enlargement/darkening of areola: darker pigment helps newborns locate the nipple
colostrum (first milk): thick yellowish fluid produced in late pregnancy, first few days after birth before mature milk comes in
breast and nipple changes post weaning (after stopping breastfeeding)
alveoli and ducts gradually atrophy (shrink back)
- glandular tissue is replaced by fat
apoptosis of milk producing cells
lactiferous ducts remain but become smaller & less active
blood supply of breast: 4 main arteries
-
Internal Thoracic Artery (Internal Mammary Artery): branch of the subclavian artery, runs down inner chest (parallel to sternum)
🔹 provides most of the blood supply to the medial half of the breast -
Lateral Thoracic Artery: branch of the axillary artery, runs along outer (lateral) chest wall.
🔹 supplies lateral half of the breast, especially the glandular tissue -
Thoracoacromial Artery (Pectoral Branch): branch of the axillary artery, passes over the pectoralis minor muscle.
🔹 provides additional blood supply to the upper breast and overlying skin -
Posterior Intercostal Arteries: runs b/w the ribs, supplying the chest wall.
🔹 supports deep parts of the breast, especially the lateral and lower portions
lymphatic drainage of breast
4 quadrants→ upper lateral, lower lateral, upper medial, lower medial
lateral quadrants: drain into the anterior axillary (pectoral) nodes
- 75% of lymph from the breast drain here
- located near lower border of pectorals major
medial quadrants: drain into the internal thoracic (parasternal) nodes (which run alongside internal thoracic artery, parallel to sternum) - in the middle of the chest
- about 20%
- important b/c this is how cancer spreads to the other breast!! (b/c of this lil communication space b.w the 2)
posterior intercostal arteries: some lymph vessels follow this path to drain into posterior intercostal lymph nodes (near the vertebrae)
- about 5%
- can cause cancer to spread to spine or lungs
from axillary tail: lymph from axillary tail drains into posterior axillary (subscapular) subgroup of lymph nodes
- located along posterior axillary fold and are important in spread of cancer to back & shoulder region
lymphatic drainage and breast cancer
60% of breast cancers occur in the upper lateral quadrant since these are the ones that drain mostly in the axillary node
- lymphatic spread to opposite breast, abdominal cavity, or into root of neck is bc of obstruction of normal lymphatic drainage pathways
breast mammography
low-dose X-ray used to detect early signs of breast cancer before they can be felt
- dangers are minimal and examination can be repeated often
breast examination
essential for detecting early signs of breast cancer, cysts, or infections
- inspect breasts for symmetry (some degree of asymmetry is common)
- any swelling should be noted
- examine nipples for evidence of retraction (carcinoma can cause retraction by pulling on the lactiferous ducts)
- patient should lie down so that breasts can be palpated against underlying thoracic wall
- patient should sit up again and raise both arms above head (shows any carcinoma tethered to the skin, suspensory ligaments, or lactiferous ducts)
which muscle divides the axilla into 3 regions and what are they?
pectoralis minor muscle
3 subregions:
1. proximal: extends from lateral border of 1st rib to upper border of pectoralis minor
- deep: behind the pectoralis minor muscle
- distal: extends from lower border of pectoralis minor to lower border of the teres major
what artery continues as the axillary artery?
subclavian artery
axillary artery: begins from lateral border of 1st rib & ends at lower border of teres major muscle, where it continues as the brachial artery
axillary sheath
protective layer of connective tissue (fascia) that surrounds the axillary artery and cords of the brachial plexus as they pass through the axilla
- derived from the prevertebral fascia of the neck
relations of the first part of the axillary artery
extends from lateral border of 1st rib to upper border of pectoralis minor
anteriorly (in the front): pectoralis major and the skin; cephalic vein crosses the artery
posteriorly (in the back): long thoracic nerve (* runs down & controls movement of the serratus anterior*)
laterally: 3 cords of the brachial plexus
medially: axillary vein (axillary vein is always medial to the axillary artery)
relations of the second part of the axillary artery
behind the pectoralis minor muscle
anteriorly: pectoralis minor, pectoralis major, and the skin
posteriorly: posterior cord of the brachial plexus, the subscapularis muscle, and the shoulder joint
**laterally: lateral cord of the brachial plexus
medially: medial cord of the brachial plexus and the axillary vein
relations of the third part of the axillary artery
extends from lower border of pec minor to lower border of teres major
anteriorly: pectoralis major for a short distance; more distally, the medial root of the median nerve crosses the artery
posteriorly: subscapularis, latissimus dorsi, and teres major; axillary and radial nerves also lie behind the artery
laterally: coracobrachialis, biceps, and humerus; lateral root of the median nerve and the musculocutaneous nerve also lie on the lateral side
medially: ulnar nerve, axillary vein, and medial cutaneous nerve of the arm
where is the axillary vein located?
formed at the lower border of the teres major muscle by union of venae comitantes (artery going is accompanied by veins on both sides) of brachial artery & basilica vein
so basically starts where the axillary artery changes its name to brachial artery (in the axial) and runs upward toward the heart
- once it reaches the lateral border of the first rib, changes its name to subclavian vein
also lies outside the axillary sheath
how many branches are formed from the axillary artery and how many from each part?
6 branches formed
1 from first part
2 from 2nd part
3 from 3rd part
however, branching pattern is subject to much variation
6 branches of the axillary artery (just name them)
First part:
- Superior thoracic (Highest thoracic)
Second part:
- Lateral thoracic
- Thoracoacromial artery
Third part:
- Subscapular artery → divides into circumflex scapular & thoracodorsal arteries
- Anterior circumflex humeral
- Posterior circumflex humeral
branch of the first part of the axillary artery
highest thoracic artery
runs along upper border of pec minor to reach area of the 1st 2 ribs
branches from 2nd part of axillary artery
thoracoacromial artery→ short trunk that immediately divides into 4 terminal branches that supply pectoral muscles & acromioclavicular region
lateral thoracic artery → runs along lower (lateral) border of pectoralis minor along the lateral chest wall
branches from the 3rd part of the axillary artery
subscapular artery large vessel, descends along lower (axillary) border of scapula
- divides into circumflex scapularand thoracodorsal arteries
- circumflex scapular artery curls around axillary border of the scapula to reach the infraspinous fossa
- thoracodorsal artery descends along the latissimus dorsi muscle to reach the lateral thoracic wall
anterior and posterior circumflex humeral arteries → wind around front and back of the surgical neck of the humerus, respectively, and form an anastomosing circle
- posterior artery is the larger of the two and passes through the quadrangular space with the axillary nerve to reach the scapular region
arterial anastomosis around shoulder joint
arterial anastomosis: network of blood vessels that connect w/ each other to ensure continuous blood supply, even if one artery gets blocked or damaged
in shoulder joint, exists b/w branches of subclavian artery & axillary artery
importance: If the axillary artery is blocked due to injury or compression, blood can still reach the shoulder and upper limb through these alternate routes, preventing tissue damage from lack of blood supply
what are the 6 groups of axillary lymph nodes (just list them & their flow summary)
- anterior (pectoral) lymph nodes
- posterior (subscapular) group
- lateral group
- central group
- apical group
- infraclavicular (deltopectoral) group
peripheral groups (anterior, posterior, lateral) drain into → central group which drains into → apical group which drains into → subclavian lymph trunk which then enters → venous circulation
6 groups of axillary nodes: location + drainage of 1. anterior (pectoral) lymph nodes
location: lie deep to the pectoralis major muscle, along the lower border of the pectoralis minor (basically like outside edge of 4th rib)
drainage: receive lymph from:
- lateral quadrant of the breast
- anterolateral abdominal wall above the umbilicus (belly button)
6 groups of axillary nodes: location + drainage of 2. posterior (subscapular) lymph nodes
location: lie in front of the subscapularis muscle
drainage: receive lymph from the back, specifically from areas above the iliac crest (lower back region)
6 groups of axillary nodes: location + drainage of 3. lateral group lymph nodes
location: found along the medial side of the axillary vein (near the head of the humerus)
drainage: receive most of the lymph from the upper limb
(q: which receives drainage from upper limb? a: lateral group)
6 groups of axillary nodes: location + drainage of 4. central group lymph nodes
location: situated in the center of the axilla, in the axillary fat deep to the pectoralis minor (kind of just right in the middle of the armpit)
drainage: collect lymph from the three groups above (anterior, posterior, and lateral lymph nodes)
6 groups of axillary nodes: location + drainage of 5. apical lymph nodes
location: found at the apex (top) of the axilla, near the lateral border of the first rib
drainage: receive lymph from all other axillary lymph nodes and eventually drain into the subclavian lymph trunk, which then connects to the venous system
6 groups of axillary nodes: location + drainage of 6. deltopectoral lymph nodes
not strictly axillary b/c located outside the axilla
location: found in the deltopectoral groove, between the pectoralis major and deltoid muscles
drainage: receive superficial lymph from the lateral side of the hand, forearm, and arm
why is the axillary artery is prone to injury?
axillary artery is highly vulnerable to trauma, second only to the popliteal artery (behind the knee)
reason: located superficially in the axilla, making it prone to lacerations (cuts) due to penetrating injuries, fractures, or gunshot wounds
clinical consequences: severe bleeding & potential loss of upper limb circulation
what is a synovial double plane joint
joint = where 2 bones meet
synovial joint: joint that has fluid-filled cavity (synovial fluid), allowing smooth movement
plane joint: joint where flat surfaces slide against each other
double plane: means there are 2 flat surfaces, allowing movement in two planes (e.g., forward-backward and up-down)
exs. sternoclavicular & acromioclavicular joints
Sternoclavicular (SC) Joint
(structure, ligaments, & movements)
structure: synovial double plane joint that is formed between the sternum (manubrium) and clavicle (medial end) - this is the articulation
- contains an articular disc (fibrocartilage pad inside joint that helps w/ shock absorption, stability, and smooth movement - kind of like a cushion*)
ligaments (for strength & stability):
- sternoclavicular ligaments (prevents excessive forward and backward movement of the clavicle)
- costoclavicular ligament (connects clavicle to first rib, limits elevation of the clavicle, preventing excessive upward movement)
movement:
- elevation & depression (e.g., shrugging shoulders)
- protraction & retraction (e.g., pushing shoulders forward and pulling them back).
- rotation (during arm elevation)
anterior: skin + fibers of sternocleidomastoid + pec maj. fibers
posterior: sternohyoid muscle + brachiocephalic artery, left brachiocephalic vein, left common carotid artery
acromioclavicular (ac) joint
(structure, ligaments, movement)
structure: synovial plane joint (gliding movement) that is formed between the lateral end of clavicle and acromion of scapula
Ligaments:
- Superior & Inferior Acromioclavicular ligaments: strengthen the joint capsule, prevent excessive clavicular movement
- accessory ligament: coracoclavicular ligament: strongest stabilizer of the AC joint, connects clavicle to the coracoid process of scapula, prevents clavicle from displacing superiorly
movements: gliding movement when scapula rotates or clavicle is elevated or depressed
- works with SC joint to allow full shoulder motion
anterior: hits deltoid
posterior: hits trapezius
superiorly: skin
anastomosis around scapula imp : around body of scapula
anastomosis: network of interconnected blood vessels that allow blood to flow even if one artery is blocked (lots around scapula)
- suprascapular artery (passes over suprascapular notch to supply supraspinatus & infraspinatus muscles)
- deep branch of transverse cervical artery or dorsal scapular artery (runs along the medial border of scapula, supplying the rhomboids and trapezius)
- circumflex scapular artery (passes through the triangular space [right below quadrangular space] to reach back of the scapula, connecting with the suprascapular artery)
function: ensures blood supply to the scapular muscles & bones
mnemonic: “some teens can always party” - for all of the scapular anatomosis
anastomosis around scapula imp : around acromion process
this anastomosis occurs around the top of the scapula, near the acromion
- acromial branch of the thoracoacromial artery: comes from axillary artery, supplies acromion and shoulder joint
- suprascapular artery: same as from scapula body, also supplies the acromion area
posterior circumflex humeral artery: comes from the axillary artery, passes through the quadrangular space to supply the deltoid and shoulder joint
function: provides blood to the shoulder joint & acromion
mnemonic: “some teens can always party” - for all of the scapular anatomosis
platysma
bunch of muscle fibers in your neck that lie just under the skin
- arises from deep fascia of pectoralis major & inserts on base of mandible (jaw)
may protect external jugular vein which underlies it
what are the 4 muscles of the pectoral region?
pectoral region - area in front of shoulder
- Pectoralis major
- Pectoralis minor
- Subclavius
- Serratus anterior
nerve supply of the following muscles:
- pectoralis major
- pectoralis minor
- subclavius
- serratus anterior
pectoralis major & minor → medial & lateral pectoral nerves (pectoralis minor is only medial pectoral nerve) from the brachial plexus
- nerve roots: C6, C7, C8 (major), C7 (minor)
subclavius → subclavian nerve (aka nerve to subclavius, comes from upper trunk of brachial plexus)
- nerve roots: C5
serratus anterior → long thoracic nerve
- nerve roots: C6, C7
action of the pectoralis major & minor
pectoralis major → adduction of arm (bring back to side) & medial rotation of arm (move towards midline of body)
pectoralis minor → depression of the shoulder (when you push something down like pressing on a table) & pulling ribs upwards when scapula is fixed (like when you take a deep breath)
action of the subclavius & serratus anterior muscles
subclavius → helps stabilize the clavicle & pull it down (depresses), steadies clavicle during movements of the shoulder joint
serratus anterior → pulls scapula forward and around rib cage (called boxer’s muscle), rotates scapula outwards in raising the arm above 90º (abduction above 90º)
what is the main function of the rotator cuff?
stabilizes the shoulder joint
cuff has no muscles (deficient) inferiorly so this is a site of potential weakness
clavipectoral fascia, deep pectoral fascia + structures piercing the clavipectoral fascia
clavipectoral fascia: strong sheet of connective tissue located under the pec. major muscle
- connects the clavicle (collarbone) to thorax & surrounds the pec. minor muscle
deep pectoral fascia: covers pectoralis major, attached superiorly to clavicle & anteriorly to sternum
STRUCTURES PIERCING IT:
1. Lateral Pectoral Nerve → this nerve supplies the pec. major muscle, helping with arm and shoulder movement
2. Cephalic Vein → large vein that drains blood from the arm and carries it to the axillary vein
3. Thoracoacromial Vessels → These arteries & veins supply blood to the shoulder, chest, and upper arm
4. Lymphatics from the Breast → small vessels that help drain lymph from breast, playing a role in the body’s immune system
contents of the superficial fascia of the chest (pectoral region)
- cutaneous nerves (skin nerves)
- cutaneous blood vessels (arteries that supply the skin)
- platysma muscle
- breast
cutaneous nerves in superficial fascia of chest (pectoral region)
2 sources of these nerves:
Cervical plexus (neck nerves) → These supply the upper chest and neck.
- C3 and C4 (from the cervical plexus) supply the shoulder and upper chest
Intercostal nerves (from ribs) → These supply the lower chest and abdomen
- T2 and T3 (intercostal nerves) supply the lower chest and upper abdomen
C3,4 directly overlap area supplies by T2,3 → some areas of the skin receive signals from both sets of nerves (why sometimes pain in heart is felt in shoulder too)
- these nerves provide sensation to the skin in the chest area
cutaneous blood vessels in superficial fascia of chest (pectoral region)
Internal thoracic artery branches → Come from inside the chest.
Posterior intercostal artery branches → Come from the back and supply the chest wall
these arteries deliver blood to the skin and superficial tissues of the chest
why is the deltoid called a multipennate muscle?
its muscle fibers are arranged in multiple diagonal rows, attaching to several tendons
- this structure increases the strength of the muscle by allowing more muscle fibers to fit into a small space
- has anterior, posterior, and middle parts of the fibers
axillary nerve supplies which 2 muscles? imp.
deltoid & teres minor
demonstrate flexion & extension of shoulder joint
flexion: right arm goes out but also kind of to the left
extension: right arm just goes downward and backwards
nerve supply of the following muscles (scapular region):
- deltoid
- supraspinatus
- infraspinatus
- teres major
- teres minor
- subscapularis
deltoid: axillary nerve
supraspinatus & infraspinatus: suprascapular nerve
teres major: lower subscapular nerve
teres minor: axillary nerve
subscapularis: upper & lower subscapular nerves
nerve supply of the following muscles:
- trapezius
- latissimus dorsi
- levator scapulae
- rhomboid minor
- rhomboid major
trapezius: spinal part of accessory nerve
- nerve roots: cranial nerve
latissimus dorsi: thoracodorsal nerve
- nerve roots: C7
levator scapulae: C3,4 dorsal scapular nerve
rhomboid major & minor dorsal scapular nerve
- nerve roots: C4
only predominant nerve root listed
action of the follow muscles:
- deltoid
- supraspinatus
- infraspinatus
- teres major
- teres minor
- subscapularis
deltoid: anterior fibers flex arm (move forward) & medially rotate the arm; middle fibers abduct arm (lift sideways); posterior fibers extend and laterally rotate arm
supraspinatus: starts arm abduction (first 15º) before deltoid takes over, stabilizes shoulder joint (rotator cuff)
infraspinatus: laterally rotates arm & stabilizes shoulder joint (rotator cuff)
teres major: medially rotates arm and stabilizes shoulder joint
teres minor: laterally rotates arm and stabilizes shoulder joint
subscapularis: medially rotates arm & stabilizes shoulder joint
action of the following muscles:
- trapezius
- latissimus dorsi
- levator scapulae
- rhomboid major
- rhomboid minor
trapezius: upper fibers elevate scapula; middle fibers retract scapula (pull back); lower fibers depress (lower) shoulder (medial border of scapula)
latissimus dorsi: extends, adducts, medially rotates arm
levator scapulae: lifts medial border of scapula
rhomboid major & minor: raises medial border of scapula upwards & medially
muscles that participate in abduction of the arm imp
supraspinatus starts (0-15º) → deltoid continues (15-90º) → serratus anterior & trapezius (90-180º- overhead abduction)
which muscles participate in medial/internal rotation of the arm? imp
- pectoralis major
- anterior fibers of deltoid
- latissimus dorsi
- teres major
which muscles participate in lateral/external rotation of the arm? imp
- posterior fibers of the deltoid
- infraspinatus
- teres minor
which muscles participate in adduction of the arm? imp
- pectoralis major
- latissimus dorsi
- biceps long head
- triceps long head
which muscles participate in flexion (0-135º) of the arm? imp
- pectoralis major (clavicular part)
- anterior fibers of deltoid
- coracobrachialis
which muscles participate in extension (45-60º) of the arm? imp
- posterior fibers of deltoid
- latissmus dorsi
- teres major
scapular humeral mechanism
for every 3º of total arm movement, 2º comes from humerus moving while 1º comes from thescapula rotating
- Initial Phase (0°–30° Abduction) →
mostly the humerus moves, with little scapular movement. - Middle Phase (30°–90° Abduction) →
scapula begins to rotate upward with the humerus - Final Phase (90°–180° Abduction) →
scapula rotates fully to allow maximum arm elevation
brachial plexus: dorsal scapular nerve
branches from C5 root
supplies levator scapulae & rhomboid muscles
brachial plexus: long thoracic nerve
arises from C5, C6, C7 roots
supplies serratus anterior (unusual passes through its superficial side rather than the usually belly of muscle - makes it more prone to injuries)
brachial plexus: branches from upper trunk
lower and middle trunks dont have branches
upper trunk:
- nerve to the subclavius (C5-6) which supplies subclavius muscle
- suprascapular nerve (passes through suprascapular notch then goes down to supply supraspinatus, more down to infraspinatus, and the shoulder joint)
brachial plexus: branches from lateral cord
lateral pectoral nerve: supplies pectoralis major
terminal branch is muscular cutaneous nerve
also combines with medial cord to form the lateral root of the median nerve (median nerve has no branches in the axilla)
brachial plexus: branches from medial cord
medial pectoral nerve: supplies pectoralis minor and major
medial cutaneous nerve of forearm: supplies skin on medial side of forearm
medial cutaneous nerve of the arm: supplies skin on medial side of arm
ulnar nerve: no branches in the axilla (terminal branch)
also joins with the lateral cord to form the medial root of the median nerve (terminal branch)
brachial plexus: branches from posterior cord
upper & lower subscapular nerves: supply upper & lower parts of the subscapularis muscle, lower also supplies teres major
thoracodorsal nerve: supplies latissimus dorsi
axillary nerve: passes through quadrangular space (terminal branch)
radial nerve: largest branch of brachial plexus, gives off branches to heads of triceps muscle (terminal branch)
Sympathetic innervation
- “fight or flight” response
- comes from T2-T6 spinal segments
- fibers ascend to higher levels in the sympathetic chain before synapsing in the middle, inferior, and first thoracic ganglia
- sympathetic stimulation causes vasodilation in skeletal muscles for increased blood flow, vasoconstriction in the skin, sweating, and piloerection (goosebumps)
axillary sheath & brachial plexus nerve block
brachial plexus block: type of regional anesthesia used to numb upper limb, often performed for surgical procedures, pain management, or trauma care
- 3 TYPES:
1. interscalene block: targets roots of brachial plexus (for shoulder surgeries)
2. supraclavicular block: targets trunks (for elbow, forearm, or hand surgeries)
3. infraclavicular block: targets cords (for lower arm and hand procedures)
axillary nerve block: anesthetic injected into axillary sheath near axillary artery
- commonly used for surgeries on the forearm, wrist, and hand
what are the anterior and posterior compartments of arm divided based off of and what divides them?
divided based off movement
anterior → flexors (arm going forward)
posterior → extensors (arm going backwards)
divided by the medial & lateral inter muscular septum that are within the sheath of deep fascia that encloses the arm
anterior compartment of arm- muscles, their nerve & blood supply
- biceps brachii
- coracobrachialis
- brachialis
nerve supply → musculocutaneous nerve (C5-C7)
blood supply → radial artery
for all
anterior compartment of arm: brachialis muscle (origin, insertion, function)
origin: middle third of medial surface of humerus
insertion: coronoid process & ulnar tuberosity
function: flexes forearm at elbow joint
anterior compartment of arm: coracobrachialis muscle (origin, insertion, function)
origin: coracoid process of scapula
insertion: middle third of medial surface of humerus
function: flexes arm at shoulder joint
anterior compartment of arm: biceps brachii muscle (origin, insertion, function)
origin: short head from coracoid process of scapula, long head from supraglenoid tubercle of scapula
insertion: radial tuberosity & bicipital aponeurosis (aponeurosis- where muscles tendons meet)
function: strong supinator when forearm is flexed, all screwing movement done with it, short head is flexor of the arm, flexor of the elbow, long head prevents upwards displacement of head of humerus
pathway of musculocutaneous nerve
arises from lateral cord of brachial plexus → travels with 3rd part of axillary artery in lower axilla → pierces coracobrachialis muscle near shoulder → travels down b/w biceps & brachialis muscles (supplies both) → continues down towards lateral side of arm → becomes lateral cutaneous nerve of the forearm once it goes into the forearm
what does articular branch mean?
the one that supplies joints
pathway of brachial artery in arm
starts at lower edge of teres major (continuation of axillary) → travels medially alongside median nerve → goes in front of biceps & coracobrachialis →lies superficially in the middle of arm (makes it easy to feel pulse there) → end at cubital fossa (front of elbow) → divides into radial (lateral) and ulnar (medial) branches
4 branches of the brachial artery
-
profunda brachii artery: deep brachial artery, largest branch that runs with the radial nerve in the posterior compartment
- supplies triceps brachii and contributes to the elbow anastomosis - nutrient artery to humerus: supplies bone marrow of humerus
3 & 4. superior and inferior ulnar collateral artery: both help in anastomosis of the elbow joint, superior is above the end of the humerus while inferior is below the end of the humerus
spotting brachial artery, median nerve, and ulnar nerve on cadaver
- brachial artery will have a little hole (lumen) in it (nerves can never have lumens!!)
- median nerve will starts from 2 nerves (branches of the lateral & medial cord)
- axillary nerve will be kati wee
- ulnar nerve will be from the medial epicondyle
posterior compartment of arm: muscle, nerve supply, blood supply, structures passing through compartment
muscle: triceps (only 1 muscle in this compartment)
nerve supply: radial nerve (C6, C7, C8)
blood supply: profunda brachii & ulnar collateral arteries
structures passing through compartment: radial & ulnar nerve
origin/insertion and function of triceps
origin:
- long head → infraglenoid tubercle of scapula (long head originates from scapula, while lateral & medial heads originate from humerus - identifier)
- lateral head → above radial groove
- medial head → below radial groove (medial head is under the long & lateral heads)
insertion: all 3 heads insert into olecranon process of ulna via triceps tendon
function: main extensor muscle
significance of the radial nerve
sole motor nerve of the posterior compartment of the arm & forearm
- provides extensive cutaneous innervation along posterior aspect of the entire limb
course of the radial nerve in the arm
originates from posterior cord of brachial plexus → passes behind (posterior) axillary artery → gives off branches to the long head of triceps brachii → travels along radial groove with the profunda brachii artery → supplies all 3 heads of triceps → pierces lateral intermuscular septum (separates anterior & posterior compartments) to enter the anterior compartment → travels b/w brachialis & brachioradialis → lateral epicondyle of humerus
pathway of the ulnar nerve in the arm
arises from medial cord of brachial plexus → runs medial to axillary artery but gives no branches in the axilla!! → travels medial to brachial artery → pierces medial intermuscular septum & enters posterior compartment → passes behind medial epicondyle (funny bone area!!)
profunda brachii artery (aka deep brachii artery)
- arises from
- brachial artery near its origin
- accompanies radial nerve in radial groove of humerus
- supplies triceps
- takes part in anastomosis around elbow joint
- ends by diving into middle & radial collateral arteries
