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WEEK 22:
Anatomy of nerve plexuses:
| Question | Answer |
|---|---|
| where are the primary rami found | in spinal nerve |
| types of primary rami | ventral (anterior) and dorsal (posterior) |
| dorsal rami | pass posteriorly to supply strip of skin (dermatome) extending either side of midline of neck/ trunk (some fail to reach the skin -C1) and extensor muscles of the vertebral column |
| ventral rami | larger than dorsal rami and can be split in 5 groups |
| feature of all spinal nerves (except T2-T12) | their anterior rami branch and rejoin forming nerve plexuses |
| principle of convergence | branches may contain fibres from more than one spinal level (Ǝ-) |
| clinical advantage of regrouping nerve fibres | damage to one spinal segment usually does not lead to complete loss of function |
| 5 groups of ventral (anterior) primary rami | cervical plexus, brachial plexus, nerves of the trunk, lumbosacral plexus, and coccygeal plexus |
| brachial plexus | formed by anterior rami of C5-T1 supplying the upper limb (sensory and motor) split into roots, trunks, divisions, cord, and branches |
| Erb Duchenne Palsy | C5 & C6 avulsion/ tractional lesion of upper trunk (nerves injured because they were stretched too much) usually occurring in child birth or trauma |
| Erb Duchenne palsy signs (5) | Waiter's tip sign, shoulder abduction/lateral rotation/flexion affected, elbow flexion paralyzed, limb hangs by side adducted and medially rotated (due to unopposed pectoralis major), and forearm extended and pronated due to deinnervation of biceps |
| Klumpke's palsy | damage to lower trunk (C8 + T1 avulsion) leading to clawed hand |
| dorsal scapular nerve | supplies rhomboid major, minor, and levator scapulae and damage to nerve leads to winged scapula |
| long thoracic nerve | supplies serratus anterior and damage to nerve leads to winged scapula |
| Suprascapular nerve | supraspinatus and infraspinatus muscle |
| Thoracodorsal nerve | supplies latissimus dorsi muscles |
| lateral and medial pectoral muscles | supply pectoralis major and minor |
| upper and lower subscapular muscle | supplies subscapularis and teres major |
| examples of autonomic plexuses (4) | cardiac, pulmonary, coeliac, and hypogastric plexus |
| dermatome | region of skin supplied by 1 spinal nerve |
| autonomic plexuses | involuntary nervous system/ visceral nervous system formed by sympathetic and parasympathetic nerves including cardiac plexus, pulmonary plexus, coeliac plexus, and hypogastric plexus |
| principle of divergence | spinal level may contribute to more than one branch (-E) |
| cervical plexus level | C1-C5 |
| brachial plexus level | C5-T1 |
| nerves of the trunk level | T1-L1 |
| lumbosacral plexus level | L1-S3 |
| coccygeal plexus level | S4-S5, Co1 |
| cervical plexus supplies what | head and neck |
| brachial plexus supplies what | upper limb |
| nerves of the trunk supply what | trunk |
| lumbosacral plexus supplies what | trunk and lower limb |
| coccygeal plexus supplies what | pelvis and lower trunk |
| types of nerves in the cervical plexus | cutaneous (superficial) and motor (deep) |
| cutaneous (superficial) nerves of the cervical plexus (4) | lesser occipital, greater auricular, transverse cervical, and supraclavicular |
| motor (deep) nerves of the cervical plexus (3) | ansa cervicalis, phrenic, and other muscular branches |
| lesser occipital nerve | cutaneous (superficial) nerve of the cervical plexus from C2 (C3) suppling the skin of the neck and scalp posteriosuperior to auricle |
| greater auricular nerve | cutaneous (superficial) nerve of the cervical plexus from C2, C3 supplying the skin over parotid gland, part of auricle, and skin from angle of mandible to mastoid process |
| transverse cervical nerve | cutaneous (superficial) nerve of the cervical plexus from C2, C3 supplying the skin of anterior cervical region |
| supraclavicular nerve | cutaneous (superficial) nerve of the cervical plexus from C3, C4 branching and supplying skin of neck and over clavicle to skin of shoulder |
| ansa cervicalis nerve | motor (deep) nerve of the cervical plexus from C1-C3 supplying the infrahyoid muscles (except thyrohyoid) |
| phrenic nerve | motor (deep) nerve of the cervical plexus from C3-C5 supplying the diaphragm |
| other muscular branches of nerves | motor (deep) nerve of the cervical plexus from C1-C5 |
| why is elbow flexion paralysed in those with Erb-Duchenne palsy | C5 & C6 roots usually supply the brachialis and biceps (flexors) but are damaged so cant |
| musculocutaneous nerve spinal root value | C5-C7 |
| median nerve spinal root value | C5-C7, C8-T1 |
| ulnar nerve spinal root value | C8-T1 |
| radial nerve spinal root value | C5-T1 |
| axillary nerve spinal root value | C5,C6 |
| dorsal scapular nerve spinal root value | C5 |
| suprascapular nerve spinal root value | C5,C6 |
| upper and lower subscapular nerve spinal root value | C5,C6 |
| long thoracic nerve spinal root value | C5-C7 |
| medial and lateral pectoral nerve spinal root value | C5-T1 |
| thoracodorsal nerve spinal root value | C7,C8 |
| cardiac plexus as an autnomic plexus | innervates heart where sympathetic fibres come from cervical and upper thoracic regions of the sympathetic trunk while parasympathetic fibres are supplied by the vagus nerve (cranial nerve x). Both of these also contribute fibres to oesophageal plexus |
| pulomary plexus | surrounds lung root and has branches from upper thoracic sympathetic trunk and vagus nerve |
| sympathetic fibres | speed up heart and constrict arteries where afferent fibres are associated with pain (eg from impaired blood supply to myocardium) |
| parasympathetic fibres | reduce heart rate and dilate arteries where afferent fibres take part in cardiovascular reflexes |
Created by:
kablooey
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