Biology 211 Anatomy & Physiology I Dr. Thompson The Spinal Cord

Human Central Nervous System Starts as a hollow tube in the embryo; Remains hollow & fluid-filled throughout life; These 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 the brain and its various parts Caudal end of this hollow tube does not enlarge or fold; Develops into spinal cord

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

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

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 three openings (apertures or foramina) into the subarachnoid space. Median Aperture Two Lateral Apertures Surrounds brain & spinal cord. Reabsorbed into blood through arachnoid villi on surface of brain

Posterior Median Sulcus Anterior Median Fissure Central Canal

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 Recall: In brain and spinal cord

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 Ventral (Anterior) Horn: Cell bodies of neurons which receive efferent information from the brain and send it to skeletal myocytes (somatic motor innervation) 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)

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

Tracts of the spinal cord are described in your 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 deccusates 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 are 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.

Spinal nerves are 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

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 equine which is in the subarachnoid space

Next: Let's follow the spinal nerves distally as they form the peripheral nervous system.