Nerves. *brachial plexus + axilla + spinal cord Flashcards
Generally, which nerve innervates the superficial and intermediate layers of the extrinsic shoulder muscles?
Anterior rami
Which nerve innervates the intrinsic shoulder muscles?
Posterior rami
Through which foramen does the suprascapular nerve travel?
-Suprascapular foramen (formed by the suprascapular notch and the superior transverse ligament of the scapula)
What is the travel buddy and path of the suprascapular nerve?
-N travels through foramen while suprascapular artery travels superiorly to foramen (not through)
-They meet up by the supraspinatus
-They travel inferior to the spinoglenoid notch to get to the infraspinatus
The musculocutaneous nerve is ________ to the brachialis and ____________ to the biceps brachii.
Superficial
Deep
Musculocutaneous nerve pathway
-Arises from lateral cord of brachial plexus
-Pierces coracobrachialis
-Travels deep to biceps brachii and superficial to brachilis (sandwiched between them)
-Exits the muscle sandwich by travelling lateral to distal aspects of biceps brachii
-Terminates as lateral cutaneous nerve of forearm
What is the quadrangular space?
The square that makes up the route for the axillary nerve
What are the boundaries of the quadrangular space?
Superior: teres minor
Inferior: teres major
Medial: triceps brachii long head
Lateral: triceps brachii lateral head (or humerus)
What is directly inferior to the quadrangular space?
The triangular interval
What does the axillary nerve innervate?
Deltoids
Teres minor
What is the triangular interval?
The route for the radial nerve
Boundaries of the triangular interval?
Superior: teres major
Medial: triceps brachii long head
Lateral: triceps brachii lateral head (or humerus)
Identify the structures of the arm in this transverse section (start at top and move clockwise)
-Radial nerve
-Triceps brachii longhead
-Triceps brachii medial head
-Musculocutaneous nerve
-Biceps brachii short head
-Biceps brachii long head
-Brachialis
-Triceps brachii lateral head
Is coracobrachialis present? Why or why not?
No because the section is too distal
What is the femoral triangle?
The travel space for the femoral nerve, artery, and vein
Boundaries of femoral triangle
Superior: inguinal ligament (of external obliques)
Lateral: sartorius
Medial: adductor longus
Floor: iliopsoas (medial) and pectineus (lateral)
When travelling together, what is the arrangement (medial to lateral) of the femoral n/v/a?
Medial to Lateral:
1. Femoral vein
2. Femoral arterty
3. Femoral nerve
The biceps femoris LH is ________ and the biceps femoris SH is ______ to the sciatic nerve.
Superficial
Deep
Which artery and vein travel with the sciatic nerve?
Popliteal artery and vein
Where do the popliteal artery and vein travel through?
The popliteal fossa and adductor hiatus
Boundaries of the popliteal fossa (superior because we haven’t learned the calve muscles)
Superomedial: semitendinosus
Superolateral: biceps femoris short head
Which division of the sciatic nerve is more lateral?
Common fibular nerve
Identify these structures in this transverse section of the thigh (start at top and go clockwise). What is the yellow circle and the red circle?
-Rectus femoris
-Vastus lateralis
-Vastus intermedius
-Biceps femoris short head
-Biceps femoris long head
-Semitendinosus
-Semimembranosus
-Adductor magnus
-Gracilis
-Adductor brevis
-Adductor longus
-Sartorius
Yellow circle: sciatic nerve
Red circle: femoral artery nerve and vein
Which structures are missing and why?
-Pectineus
-Obturator externus
-Iliapsoas
They are too distal
Muscles in the anterior compartment of the thigh are innervated by the _________ nerve.
Femoral
Muscles in the posterior compartment of the thigh are innervated by __________________.
Divisions of the sciatic nerve
Muscles in the medial compartment of the thigh are innervated by the ____________ nerve.
Obturator
Muscles in the superficial and intermediate layers of anterior compartment of the forearm are innervated by _________.
Median nerve
Muscles in the deep later of anterior compartment of the forearm are innervated by ______.
Anterior interosseus nerve
Travel path of the median nerve
-Travels through the medial aspect of the arm
-Travels anterior to elbow joints
-Travels between the two heads of pronator teres
-Travels between FDS and FDP
-Reappears superficially, lateral to palmaris longus tendon
-Enters the hand via the carpal tunnel
Travel path of the ulnar nerve and artery
-Arises from medial cord of the brachial plexus
-Travels through the arm on the medial aspect
-Travels posterior to the medial epicondyle
-Reappears in the anterior compartment of the forearm deep to flexor carpi ulnaris travelling with ulnar artery
-Enters the hand with ulnar artery superficial to the flexor retinaculum
Travel path of the anterior interosseus nerve
-Arises from median nerve between the two heads of pronator teres
-Travels anterior to the interosseus membrane between flexor digitorum and flexor pollicis longus
-Terminates in pronator quadratus
Extrinsic back muscles are generally innervated by the __________ rami of the spinal nerves. Which exception is there?
-Anterior rami
-Trapezius: Spinal accessory nerve (cranial nerve XI)
Intrinsic back muscles are generally innervated by the ______ rami of spinal nerves. Which exception is there?
-Posterior
-Intertransversarii: anterior rami and posterior rami
How can you find the dorsal scapular and spinal accessory nerves using a muscle? Which muscle is this?
If you find levator scapulae, DSN is medial and SAN is lateral to it.
From which view can you see the thoracodorsal nerve?
Anterior view in a supine donor
Why is the intertransversarii innervated by posterior and anterior rami of spinal nerves?
-The muscles are very close to the intervertebral foramina so close to both ramis
Which nerves innervate the respiratory diaphragm?
-Right phrenic nerve and left phrenic nerve
What is the travel buddy/path for the phrenic nerves?
-Phrenic nerve in PHRONT of the vessels arises from/travelling to the heart
-Phrenic nerves are lateral to the heart
-Starts at neck
-Travels through thorax to superior thoracic aperture
-Travels with the pericardiacophrenic artery
Are spinal nerves part of the PNS or CNS?
PNS
How many pairs of bilateral spinal nerves are in each segment of the spinal cord?
Cervical: 8
Thoracic: 12
Lumbar: 5
Sacral: 5
Coccygeal: 1
Why are there cervical and lumbosacral enlargements of the spinal cord?
-Enlargements accomodate the plexi arising from these locations
-Cervical: brachial plexus
-Lumbosacral: lumbosacral plexus
How long is the spinal cord?
Spans C1 to L2
Medullary cone
-Tapering inferior to end of spinal cord at L2
Why is the spinal cord not the full length of our our vertebral column?
-During development, our vertebral column lengths and our spinal cord ascends within the vertebral canal and outgrows us
Cauda equina
-Bundle of spinal nerve roots inferior to L2 in vertebral canal and sacral canal
Filum terminale (terminal filament)
-Extension of neural and connective tissue covered in pia mater (in dural sac)
-It’s rightttt in the middle and descends through the cauda equina
-It pierces the dural sac at the end near the coccyx
-When it exists the dural sac, it’s still covered in dura mater
Where do the spinal nerves exit the vertebral canal?
Intervertebral foramina
C1-C7 spinal nerves exit _______ their vertebrae that has the same name as them
Above
C8 spinal nerves exit _________ to the ______ vertebrae
superior, T1
T1 - Co1 spinal nerves exit ________ their vertebrae that has the same name as them
Below
Rootlets stem ______________
directly from spinal cord
The convergence of which structures form the rami?
Rootlets + Roots + Spinal nerves = Rami
Rootlets from both _______ and ________ form the posterior and anterior roots, which form the ________
Anterior and posterior
Spinal nerve
Anterior rootlets/roots are for __________ information
Efferent (motor)
Posterior rootlets/roots are for _________ information
Afferent (sensory)
True/False: Spinal nerves are made up of both efferent and afferent rootlets/roots
True
What point is where afferent and efferent information mixes?
Spinal nerve
What part of the spinal nerve is exiting at the intervertebral foramen?
The spinal nerve itself, not the roots or rootlets
What makes up the spinal meninges (from deepest to superficial)?
-Pia mater
-Arachnoid mater
-Dura mater
How does dura mater surround each spinal nerve pair?
Encloses each pair in dural root sheaths
Where does the arachnoid mater adhere to?
Directly to internal surface of dura mater
Arachnoid traceculae
Wisps of connective tissue
Denticulate ligament
-Wisps on lateral aspect of spinal cord that anchors the pia mater to arachnoid-lined dura
Where does the pia mater adhere to?
directly to spinal cord
Subarachnoid space
-Deep to arachnoid mater and superficial to pia mater
-Contains cerebrospinal fluid
Epidural space
-Superficial to dura mater
-Fat-filled space
Epidural anesthesia injection. Which structure would the needle pass through if injection in lumbar region?
-Inject anesthetic agent in epidural space in lumbar or sacral region
-Ligamentum flavum (hear a pop)
Lumbar puncture to collect CSF. Which space would you collect from and what structures would your needle pass through?
-Subarachnoid space
-Ligamentum flavum
-Dura mater
-Arachnoid mater
What is the axilla?
Passageway for structures traveling to and from the upper limb
Boundaries and function of apex of axilla.
-Cervico-axillary canal
-Opening for structures to pass through.
Medial: Rib 1
Anterior: clavicle
Posterolaterally: superior border of scapula
Base of axilla
Skin and fascia
Boundary of lateral wall of axilla
Humerus
Boundaries of medial wall of axilla
-Thoracic cage and wall
-Serratus anterior
Boundaries of anterior wall of axilla
-Pectoralis major (superficially)
-Pectoralis minor (deep)
Boundaries of posterior wall of axilla
-Subscapularis
-Teres major
-Latissimus dorsi
Contents of the axilla
-Axillary artery and branches
-Axillary vein
-Brachial plexus (cords and branches)
-Lymphatic vessels and lymph nodes
-Adipose tissue
From smallest/proximal to biggest/distal, list the structures that contribute to the brachial plexus
Rootlets, posterior and anterior roots, trunks, divisions, cords, branches
What does the brachial plexus innervate?
-Upper limb
-Overlying skin
What spinal nerves contribute to the brachial plexus?
Anterior rami of C5, C6, C7, C8, T1
What are the 3 different trunks in the brachial plexus?
Superior
Middle
Inferior
In the divisions of the brachial plexus, what are the two different divisions?
Anterior and posterior
For the divisions of each different trunk of the brachial plexus, what is the ordering of the posterior and anterior divisions?
Superior: A then P
Middle: A then P
Inferior: P then A
What are the three cords of the brachial plexus?
Lateral
Posterior
Medial
Supraclavicular region of the brachial plexus
-Contains roots and trunks
-Some branches arise from this region
Infraclavicular region of the brachial plexus
-Contains cords and branches
-Axilla is located here
At the level of the clavicle, which parts of the brachial plexus are located here?
Divisions
Which spinal nerves make up the 3 different trunks?
Superior: C5 + C6
Middle: C7
Inferior: C8 + T1
Where do the divisions of the brachial plexus enter the axilla?
-Posterior to clavicle through cervico-axillary canal
Which divisions make up the 3 different cords of the brachial plexus?
Lateral cord: superior anterior + middle anterior
C5 + C6 + C7
Posterior cord: superior posterior + middle posterior + inferior posterior
C5 + C6 + C7 + C8 + T1
Medial cord: inferior anterior
C8 + T1
Which artery do the cords of the brachial plexus surround? How does this dictate their names?
-Axillary artery
-Lateral cord is lateral to artery
-Medial cord is medial to artery
-Posterior cord is posterior to artery
Cords are located _________ to pectoralis minor in brachial plexus
Deep
Where do the branches of the brachial plexus arise from?
Either from the cords in infraclavicular region (terminal branches) or from the roots/trunks in supraclavicular region
Which branches arise from the lateral cord of the brachial plexus? Which spinal nerves contribute to these nerves?
-Musculocutaneous nerve (splits laterally)
-Lateral root of the median nerve (splits medially)
C5 + C6 + C7
Which branches arise from the medial cord of the brachial plexus? Which spinal nerves contribute to these nerves?
-Medial root of the median nerve (splits laterally)
-Ulnar nerve (splits most medially)
C8 + T1
The median nerve is formed by :
The medial root of medial cord and lateral root of lateral cord
Which branches arise from the posterior cord of the brachial plexus? Which spinal nerves contribute to these nerves?
-Axillary nerve (C5 - C6)
-Radial nerve (C5 - T1)
Which branches arise from the roots of the brachial plexus? Which spinal nerves contribute to these nerves?
-Dorsal scapular nerve (C5 anterior rami)
-Long thoracic nerve (C5-C7 anterior rami)
Which branches arise from the trunks of the brachial plexus? Which spinal nerves contribute to these nerves?
-Suprascapular nerve (C5 + C6)
-Subclavius nerve (C5 + C6)
Which branches arise from higher up on the lateral cord of the brachial plexus? Which spinal nerves contribute to these nerves?
-Lateral pectoral nerve
C5 + C7
Which branches arise from higher up on the medial cord of the brachial plexus? Which spinal nerves contribute to these nerves?
-Medial pectoral nerve (C8 + T1)
-Medial cutaneous nerves of the arm and forearm (C8 + T1)
The lateral pectoral nerve sits more _______ on the pectoralis minor compared to the medial pectoral nerve
Medially
Which branches arise from higher up on the posterior cord of the brachial plexus? Which spinal nerves contribute to these nerves?
-Upper subscapular nerve (C5-C6)
-Lower subscapular nerve (C5-C7)
-Thoracodorsal nerve (C6-C8)
At which level is the medullary cone?
L2
Spinal nerves exiting superior to the vertebrae form the __________ margin of that IV foramen
Inferior
Spinal nerves exiting inferior to the vertebrae form the _________ margin of that IV foramen
superior
The coccygeal segment has _______ pair(s) of bilateral spinal nerves.
1
The cervical enlargement spans which vertebraes?
C4 to T1
The lumbosacral enlargement spans which vertebraes?
T11 to L1
Which level does the cauda equina start at?
L1/L2
Which back muscles are innervated by the anterior rami of the spinal nerves?
Rhomboids & Levator Scapulae (dorsal scapular nerve)
Intertransversarii (both anterior and posterior rami)
