The brachial plexus is a network of nerves originating from the _____ ____ of the 5th ____ through the 1st ___ spinal nerves. This network of nerves supplies the _____ and _____ innervation to the upper extremity.
1. ventral rami
What are potential ways in which the brachial plexus can be injured?
trauma or tumors that compress it
entrapement btwn anterior and posterior scalene muscles in neck
entrapment btwn the first rib and clavicle
entrapment under the pectoralis minor
childbirth-one of more common causes of traumatic injury
The ___ is a gateway to the upper limb. It represents a transition btwn the neck and arm and is continuous with the neck superiorly. All major structures passing into and out of the upper limb pass through the _____ (same as previous blank)
axilla. remember the posterior triangle of the neck is superior to the axillary inlet
What are the boundaries of the axilla?
What 3 structures form the boundaries of the axillary inlet?
1. lateral margin of the first rib
3. superior margin of the scapula to the coracoid
The clavicular head of the pectoralis major is innervated by the _____ ____ nerve. The sternocostal head is innervated by the ____ _____ nerve. `
1. lateral pectoral nerve
2. medial pectoral nerve
What is the major fxn of the pectoralis major as a whole? What are additional fxns and why does the pec major have additional fxns?
The major fxn as a whole is adduction and medial rotation of the arm. It also contributes to flexion and extension of the arm at the shoulder. This is due to differences in the fiber orientation of the upper and lower parts of the muscle
-lower fibers will extend the arm from a flexed position
-upper fibers will flex the arm from an extended position
What is the fxn of the pectoralis minor?
its origin in on ribs 3-5 and inserts on coracoid process of scapula. exerts a downward pull on the scapul and can also draw the coracoid process anteriorly resulting in anterior "tipping" of the scapula, necessary to put the upper limb behind the back such as when putting an arm in a coat sleeve or scratching back
What are the names of these muscles? What are the spaces pointed to in the picture and what structures pass through them? What boundary of the axilla do these muscles comprise?
comprise posterior wall of the axilla
Identify these structures. What borders do they form in the axilla?
medial and lateral walls
What are the fxns of the serratus anterior? Why are its functions critical for (as far as arm movement is concerned)? What is it innervated by? What can result if the serratus anterior is weak?
serratus anterior is a powerful protractor of the shoulder complex. it abducts the scapula during motion of shoulder protraction. additionally, it is an upward rotator of the scapula acting along with the trapezius. both abduction and upward rotation are critical for flexing the upper limb up over the head. if the serratus anterior is weak, can get "winging" of the scapula where the medial border lifts off of the thoracic wall
List the contents of the axilla (there are several).
axillary artery and vein with associated branches and tributaries
proximal portions of the biceps brachii and coracobrachialis
axillary process of the breast
lymph nodes draining the upper limb. note that all lymphatics from the upper limb drain into lymph nodes in the axilla. additionally, the back, lower neck, parts of the chest, and part of the abdominal wall drain into axillary lymph nodes. ***75% of lymphatic drainage from the mammary gland is received by axillary lymph nodes. when remove lymph nodes due to breast ca, can get lymphedema
Arteries, veins, nerves, and lymphatics pass through the axilla within the ____ ______.
The ____ artery in the neck becomes the ___ artery at the lateral margin of the first rib. This artery passes through the axilla and becomes the _____ artery at the inferior margin of the teres major.
The axillary artery is separated into what 3 portions by what muscle?
What are the branches of the axillary and brachial arteries?
The brachial plexus orginates in the ____, passes inferiorly and laterally over the ___ ____, and enters the ____.
2. first rib
The parts of the brachial plexus are from medial to lateral. What are the parts of the brachial plexus?
Real Truckers Drink Cold Beer
Divisions (won't ID on practical but must know)
Branches (form named peripheral nerves)
The cords of the brachial plexus are named according to their relationship to the ___ ____. The cords also lie deep to the ____ _____ muscle.
1. axillary artery
2. pectoralis minor
Discuss how the branches of cords (peripheral nerves) may not contain all of the axons from spinal nerves as the cord it branched from.
Just because a nerve is formed from fused spinal nerves does not mean it contains axons from all of those spinal nerves. For example, the posterior cord contains axons from spinal nerves C5-T1. It's branches (axillary and radial nerves) do not necessarily contain all axons from C5-T1. What nerves muscles/skin are innervated by is determined in the embryo and depends on what myotermal or dermatomal cells fused to form that skin or muscle. Also, for example, the radial nerve does contains axons from C5-T1 but all of the muscles it innervates to not have axons from all of these spinal nerves.
Spinal nerves C5/C6 innervate more (proximal/distal) musculature while spinal nerves C7/C8/T1 innervate more (proximal/distal) musculature.