L5: Musculo-neuro-vascular systems of pectoral and dorsal regions Flashcards
what is a muscle
Muscle is a contractile tissue consisting of cells called myocytes
Muscles cross at least one joint; i.e., each end of muscle attached to different bones
“Origin” – Proximal attachment*Usually remains fixed during movement
“Insertion” – Distal attachmentUsually, the part that moves
how do muscles work
Skeletal muscle consists of:
-Myocytes (muscle fibres)
-Bundled into fascicles
-Bundled into muscle
Myocytes contract (shorten) when they are activated by nerves (neurons)
Induces contraction of myofibrils with muscle cells via the sliding filament mechanism
myocyte activation
Electrical signals (nerve impulse) travels along nerves, towards muscles
1.Electrical signal triggers release of acetylcholine (ACh) neurotransmitter from the end of the nerve cell
2.Neurotransmitter (ACh) travels across neuromuscular junction where it binds to ACh receptor on muscle cell
3.Triggers muscle action potential and muscle contraction
Muscles consist of many myocytes
*Many myocytes contracting together produces strong muscular movement
brachial
relating to, or situated in the arm
plexus
a network of anastomosing or interlacing blood vessels or nerves
brachial plexus
is the system of nerves that emerge lateral to the spinal chord and :
- allow motor nerves send their signals from brain to upper limb muscles
- allow sensory nerves send their signals back to the brain
brachial plexus; intro
spinal nerves leave spine through spaces between vertebrae
brachial plexus formed by C5-T1 spinal nerves
brachial plexus- sections
Roots - 5 > C5-T1
Trunks - 3 > sup, mid, inf
Divisions - 6 > anterior , posterior
Cords - 3 > lat, medial, post
movements of the scapula
elevation + depression
protraction + retraction
upward + downward rotation
scapular movers or stabilisers (6 muscles)
muscles that connect the scapula to the axial skeleton
dorsal region [back];
1. trapezius
2. levator scapulae
3. rhomboid minor
4. rhomboid major
pectoral region [front of chest]
5. pectoralis minor
6. serratus anterior
trapezius; origin
large diamond shaped superficial muscle of the back
developed in rowers
origin:
-external occipital protuberance
-nuchal ligament
-spinous process of C7-T12 vertebrae
trapezius; insertion
- spine of scapula
- acromion of scapula
- lateral 1/3 of clavicle
trapezius; innervation
spinal accessory nerve
aka cranial nerve 11
trapezius; actions
- powerful retractor of scapula [rowing]
- elevates scapula [upper fibres]
- depresses scapula [lower fibres]
- upward rotation of scapula [upper fibres]
levator scapular; origin
small muscles from neck vertebrae to medial superior scapula. deep to trapezius
origin: transverse processes of C1-4 vertebrae
levator scapular; insertion
superior part of medial border of scapula
levator scapular; innervation
dorsal scapular nerve [C4-5]
levator scapular; actions
- elevates medial border of scapula
- downward rotation of scapula
rhomboid minor; origin
deep to trapezius, superior to rhomboid major
spinous process of C7-T1
vertebrae
rhomboid minor; insertion
medial border of scapula, root of spine
rhomboid minor; innervation
dorsal scapular nerve (C4-5)
rhomboid minor; actions
- retracts scapula
- downward rotation of scapula
rhomboid major; orign
deep to trapezius, inferior to rhomboid minor
origin: spinous process of T2-T5 vertebrae
rhomboid minor; insertion
medial border of scapula (inferior 2/3)
rhomboid minor; innervation
dorsal scapular nerve (C4-5)
rhomboid minor; actions
- retracts scapula
- downward rotation of scapula
dorsal scapular nerve
formed from spinal nerve roots C4-5
Passes inferiorly, medial to medial border of scapula
Innervates:
- levator scapula
- rhomboid minor
- rhomboid major
pectoralis minor; origin
deep to pectoralis major
origin: anterior surface of ribs 3-5
pectoralis minor; insertion
coracoid process of the scapula
pectoralis minor; innervation
medial pectoral nerve (C8-T1)
pectoralis minor; actions
protracts and stabilises scapula by pulling it antero-inferiorly onto posterior thoracic wall
medial pectoral nerve
arises from medial cord of brachial plexus
formed by contributions from spinal nerve roots C8-T1)
passes inferiorly deep to pectoralis minor providing innervation
serratus anterior; origin
between scapula and posterior thoracic wall
origin: medial border of scapula, anterior surface
pectoralis minor; insertion
individual muscle slips that insert into anterolateral surface of ribs 1-8
pectoralis minor; innervation
long thoracic nerve (C5-7)
pectoralis minor; actions
- protracts and stabilises scapula by pulling it anteriorly against the thoracic wall
- very important in pushing + punching
- assists with upward rotation of scapula by pulling inferior angle laterally
long thoracic nerve
formed from spinal nerve roots C5-7
passes inferiorly over the lateral surface of serratus anterior
innervates serratus anterior
nerve protected when limbs at side, but is vulnerable when limbs elevated
long thoracic nerve palsy
caused by injuries to the long thoracic nerve
trauma, heavy weightlifting repeated throwing
causes paralysis of serratus anterior - lack of protraction
scapular cannot be held firmly against the posterior aspect of the thoracic cage
winging of the scapula
‘‘C5, 6, 7 spread your wings and go to heaven’’
muscles that stabilise and/or move the glenohumeral joint and arm
- pectoralis major
- latissimus dorsi
pectoralis major; origin
large muscle on anterior chest wall - it has 2 heads
origin:
clavicular head: medial 1/2 clavicle
sternocostal head: sternum, upper 6 costal cartilages, aponeurosis of external oblique
pectoralis major; insertion
lateral lip of bicipital groove
pectoralis major; innervation
medial pectoral nerve [C8-T1]
lateral pectoral nerve [C5-7]
pectoralis major; actions
- flexes shoulder from the extended position
- adducts and internally rotates humerus
medial pectoral nerve
arises from medial cord of brachial plexus
formed by contributions from spinal nerve roots C8-T1.
passes inferiorly deep to pectoralis minor providing innervation
lateral pectoral nerve
arises from lateral cord of brachial plexus
formed by contributions from spinal nerve roots C5-7
descends deep to pectoral muscles and innervates them from posterior
latissimus dorsi; origin
back muscle, very well developed in rowers
origin:
- spinous process of T6-L5 & S1-2
- thoracolumbar fossa
- inferior ribs
- posterior iliac crest of pelvis
- inferior angle of scapula
latissimus dorsi; insertion
floor of bicipital groove
latissimus dorsi; innervation
thoracodorsal nerve C6-8
latissimus dorsi; actions
- extends, adducts, medially rotates humerus
- downward rotation of scapula
thoraco-dorsal nerve (C6-8)
arises from posterior cord of the brachial plexus
formed by contributions of spinal nerves C6-8
passes inferiorly, between scapula and thorax to reach and innervate latissimus dorsi
upon reaching latissimus dorsi, runs obliquely [inferomedially] along L. Dorsi innervating the whole muscle
arterial blood supply to upper limb
the axillary artery has 3 parts:
1. proximal to pectoralis minor
2. deep to pectoralis minor
3. distal to pectoralis minor
there are 6 branches of the axillary artery:
1st part: 1 branch
2nd part: 2 branches
3rd part: 3 branches
once the axillary artery passes the inferior border of the teres major muscle, it becomes known as the brachial artery
axillary artery [part 1]
superior thoracic artery
- passes anteriorly and inferiorly between pectoralis major and minor
- supplies pectoralis major and minor
axillary artery [part 2]
Thoraco-acromial artery:
- runs over pectoralis minor and divides into 4 branches supplying: clavicle, deltoid, acromion, pectoral muscles
Lateral thoracic artery:
- descends along lower border of pectoralis minor to supply: serratus anterior, both pectoral muscles, N.B. in female provides additional branches to breast
axillary artery [part 3]
Anterior circumflex humeral artery:
- passes anteriorly around surgical neck of humerus anastomosing with posterior circumflex humeral artery
Posterior circumflex humeral artery:
- passes posteriorly around surgical neck of humerus anastomosing with anterior circumflex humeral artery
Subscapular artery:
- largest branch of axillary nerve
- divides into: circumflex scapular artery & thoracodorsal artery
anastomosis:
Anastomosis: a cross-connection between adjacent channels, tubes, fibres, or other parts of a network
Arterial Supply Around the Scapula: Anastomosis
Terminal branches from Subclavian artery supply medial and superior scapula.
Terminal branches from axillary artery supply inferior and lateral scapula
These terminal branches anastomose together to provide complete coverage of the scapula
veins of pectoral and dorsal region
Axillary Vein drains venous blood proximally toward the heart.
It is formed at the lower border of teres major by the union of the brachial vein and basilic vein.
It runs superomedially, anteromedial to axillary artery, until it crosses the lateral border of the first rib where it becomes the subclavian vein.
The axillary vein receives tributaries that correspond to branches of the axillary artery.
Proximally, the axillary vein also receives the cephalic vein
