Spinal Cord and Spinal Nerves Chap 14 Spinal Cord Spinal Cord has a narrow central canal lined with ependymal cells and filled with cerebrospinal fluid. Gray matter lies around central canal and has 2 anterior and 2 posterior extensions = Horns. The outer part is formed of white matter. It has anterior, posterior, and lateral funiculi (sing. = funiculus) in it. Ascending tracts lie in posterior funiculi and descending tracts lie in anterior Funiculi(seen in T.S.). Spinal cord is S-shaped. Thoracic curvature – posterior; Sacral curvature – anterior
Conus medullaris is cone like inferior part of spinal cord near L2 vertebra. Cauda Equina is pony tail like arrangement of spinal nerves in lumbar-sacral region. Filum terminale is connective tissue fiber fixing inferior tip spinal cord to coccyx. Meninges – CNS coverings Meninges: Dura mater, Arachnoid and Pia Mater cover brain and Spinal Cord. Dura mater: Tough mother. Outermost is dura mater. Dura mater has sinuses filled with venous blood. Epidural space is cavity inner to it. Arachnoid mater: is middle covering. It has fibers making a network in subarachnoid space, cavity inner to it (spider web like arrangement). Pia mater: Delicate mother, is innermost covering and is in contact with brain or spinal cord. Meningitis: is bacterial or viral inflammation of meninges covering brain and spinal cord. It is treatable but can be dangerous.
Spinal Nerves There are 31 pairs of Spinal Nerves. There are 8 cervical, 12 thoracic, 5 lumbar, 5 sacral and 1 coccygeal nerves. Spinal nerve: arises from dorsal and ventral roots. Dorsal root has ganglion in it. Each spinal nerve divides into sensory dorsal ramus, motor ventral ramus and communicating rami for sympathetic ganglion.
Spinal Plexes A nerve plexus is a complex interwoven part made from branches of adjoining nerves.
Cervical Plexus (C1 – C5) gives phrenic nerve for diaphragm.
Brachial Plexus ( C5 – T1): major nerves include Radial nerve – triceps brachii, brachioradialis and most extensors in forearm Median nerve – flexor carpi radialis , pronator teres Ulnar nerve – flexor carpi ulnaris Musculocutaneous nerve – biceps brachii, brachialis Axillary nerve – deltoid muscle
T2 – T12 spinal nerves do not participate in plexus formation.
Spinal Plexes
Lumbar Plexus (L1 – L4): major nerves are femoral nerve supplies anterior muscles of thigh and obturator nerves – supplies adductor muscles of thigh.
Sacral Plexus (L4 – S4): major nerve Sciatic nerve, actually formed of tibial and common fibular nerves which supply posterior thigh, leg and foot. Dermatome is a region of body surface innervated by a pair of spinal nerves.
Recap 1 Spinal Cord & Spinal nerves 1. Dorsal ramus is ------and ventral ramus is ------in a spinal nerve. 2. Ascending tracts lie in ---funiculi and descending tracts in --funiculi. 3. Communicating rami link cell bodies in lateral horns to ------4. Cerebrospinal fluid moves in ----- canal of spinal cord. 5. Spinal nerves has ------pairs of cervical, ------pairs of thoracic, ----- pairs of lumbar, ----pairs of sacral and ---- pairs of caudal nerves. 6. All spinal nerves except ------to ------, branch and form networks called Plexes. 7. ------is the area of skin supplied by each pair of spinal nerves. 8. Nerve fibers from--- to --- spinal nerves form Brachial plexus. 9. Radial nerve supplies -- muscle and median nerve ----- muscle 10. Femoral nerve supplies --- muscle and obturator nerve ---- muscle 11. Musculocutaneous nerve supplies --- muscle and sciatic nerve ---muscle