Biology 322 Human Anatomy I Spinal Cord

Human Central Nervous System Starts as a groove which becomes a hollow tube in the embryo; Remains hollow & fluid-filled throughout life; These fluid-filled spaces form the ventricles of the brain and the central canal of the spinal cord. Cranial end of this hollow tube enlarges & folds to form brain and its various parts Caudal end of this hollow tube does not enlarge or fold; Develops into spinal cord

= = Central Brain Nervous Spinal cord System Nerves which carry information into and out of the brain and spinal cord Central Nervous System = Peripheral Nervous System =

White Matter Gray Matter Coronal Section of Brain Cross Section of Spinal Cord

Embryology of nervous system

Spinal cord surrounded by 3 layers of connective tissue: Pia Mater Arachnoid Mater Dura Mater

Subarachnoid Space Subdural Space Epidural Space (Vertebrae) Pia Mater Arachnoid Mater Dura Mater

The spinal cord is protected in three ways: 1) Vertebrae (bone) 2) Meninges Pia Mater Arachnoid Mater Dura Mater 3) Floats in cerebrospinal fluid in subarachnoid space

Cerebrospinal fluid produced within ventricles by choroid plexus. Exits from fourth ventricle through median aperture and two lateral apertures into the subarachnoid space surrounding brain and spinal cord Reabsorbed into blood through arachnoid villi on surface of brain. Cerebrospinal fluid also passes from 4th ventricle of the brain into the central canal of the spinal cord.

Posterior Median Sulcus Central Canal Embryology of nervous system Anterior Median Fissure

Recall: In brain and spinal cord Gray Matter: Nervous tissue of the CNS consisting of neuron cell bodies, their supporting glia, and unmyelinated axons & dendrites. White Matter: Nervous tissue of the CNS consisting of myelinated axons & dendrites and their supporting glia White Matter Gray Matter

Gray Matter of Spinal Cord Dorsal (Posterior) Horn: Cell bodies of neurons which receive afferent information from spinal nerves and send it toward the brain Lateral Horn: Cell bodies of neurons which receive efferent information from the brain and send it to smooth myocytes, cardiac myocytes, and glands (autonomic motor innervation) Embryology of nervous system Ventral (Anterior) Horn: Cell bodies of neurons which receive efferent information from the brain and send it to skeletal myocytes (somatic motor innervation)

Gray Matter of Spinal Cord Connecting these horns of gray matter on the right and left sides of the spinal cord is the gray commissure. This allows both sensory and motor information to be shared between the two sides of the spinal cord, and thus the two sides of the body. ( )

White Matter of Spinal Cord Myelinated axons carrying information between brain and gray matter of spinal cord (both directions). Dorsal (Posterior) Column: Lateral Column: Ventral (Anterior) Column: Embryology of nervous system Within each column, axons with same functions organized into bundles called tracts

That white matter is formed by the axons of both motor neurons and sensory neurons which are grouped into “tracts”

Individual tracts of the spinal cord are described in your Saladin text. You should be able to describe, in moderate detail, at least one ascending tract and one descending tract: Where it begins Where it ends If it decussates (crosses to opposite side) Where it is located in the spinal cord What type of information it carries What would happen if it were damaged

Spinal cord gives rise to spinal nerves. A pair of spinal nerves (one on each side) exits between each pair of vertebrae from the atlas (cervical 1) to the first vertebra of the coccyx

Each nerve connects with spinal cord through two roots: Dorsal (posterior) root Carries afferent information into dorsal horn of gray matter Ventral (anterior) root Carries efferent information away from ventral horn of gray matter

Spinal nerves named according to which vertebrae they pass between: 8 cervical nerves 12 thoracic nerves 5 lumbar nerves 5 sacral nerves 1 coccygial nerve Levels of the spinal cord named according to which spinal nerve carries information in/out of it. Embryology of nervous system

Spinal nerves named according to which vertebrae they pass between: 8 cervical nerves 12 thoracic nerves 5 lumbar nerves 5 sacral nerves 1 coccygial nerve Levels of the spinal cord named according to which spinal nerve carries information in/out of it. Thus: Spinal cord level "cervical 5" is defined as the region where spinal nerve "cervical 5" connects Embryology of nervous system

Months before you were born, your spinal cord reached all the way through your sacrum, but as you continued to develop it grew less quickly than the vertebrae which surround it. At birth, your conus medullaris was at lumbar vertebrae 3 or 4. It now lies between lumbar vertebrae 1 and 2. That means that dorsal Roots and ventral roots of the spinal nerves must extend inferiorly to reach the proper intervertebral foramina, forming the cauda equina which is in the subarachnoid space.