Spinal Cord – Anatomy of the Nervous System (Nursing)

00:02 Welcome.

00:03 In today's lecture, we will be discussing the spinal cord and the spinal nerves.

00:10 So first let's discuss the functions of the spinal cord.

00:14 What does the spinal cord do? The first function of the spinal cord is to process reflexes.

00:23 Another function of the spinal cord is to intergrate excitatory postsynaptic potentials or EPSPs and inhibitory postsynaptic potentials or IPSPs.

00:37 Recall that EPSPs are depolarizing potentials and IPSPs are hyperpolarizing potentials.

00:46 And the summation of these postsynaptic signals determine whether a nerve's impulse is generated or not.

00:54 The third and final function of the spinal cord is to conduct sensory impulses to the brain and motor impulses away from the brain to the effectors.

01:07 So now let's discuss the external anatomy of the spinal cord.

01:14 The spinal cord is going to begin as an extension of the medulla oblongata of the brain.

01:22 This happens at the level of the foramen magnum of the skull and the spinal cord is going to terminate at the level of the L2 vertebrae.

01:34 The spinal cord is protected by three main ways.

01:40 The first way are the vertebrae themselves.

01:44 These bones provide a hard layer of protection around the spinal cord.

01:51 A second layer of protection of the spinal cord is going to be the meninges.

01:56 This connective tissue layer is going to provide a lot of protection directly unto the spinal cord.

02:04 The third way that we protect the spinal cord is by suspending it in cerebrospinal fluid.

02:12 This helps to prevent shock by allowing for shock absorption when there are sudden movements.

02:20 So now let's take a closer look at that connective tissue layer that surrounds the spinal cord also known as the meninges.

02:29 The meninges is composed of three layers.

02:32 If we start from the most deep layer to the most superficial layer, you get the mnemonic P-A-D or PAD.

02:43 P stands for pia mater.

02:46 The pia mater is a transparent connective tissue layer that adheres to the surface of the spinal cord.

02:55 This layer is going to contain blood vessels and this allows for the supplying of oxygen and nutrients to the spinal cord.

03:05 There are extensions from the pia mater known as denticulate ligaments that are going to fuse with the arachnoid mater and the inner layer of the dura mater and suspends the spinal cord so that it is protected from displacement and therefore from shock.

03:25 The middle layer of the meninges is the arachnoid mater.

03:30 This is a thin, avascular covering with a spiderweb arrangement of collagen and elastic fibers thus the word arachnoid.

03:41 The arachnoid mater is continuous with the arachnoid mater of the brain.

03:48 And there is a space between this layer and the pia mater known as the subarachnoid space.

03:55 In this space, you will find the cerebral spinal fluid.

04:00 The third layer is going to be the dura mater.

04:05 The dura mater is the outermost layer of the meninges and it is the thickest and strongest layer.

04:12 It is composed of dense, irregular connective tissue.

04:17 The dura mater is continuous with the dura mater of the brain and forms a sac that hangs from the foramen magnum of the skull to the second sacral vertebrae.

04:31 It is also continuous with the outer coverings of the spinal nerves known as the epineurium.

04:37 Don't worry, we will discuss that later in the lecture.

04:41 The space between this layer and the arachnoid layer below it is known as the subdural space and in this space, you have interstitial fluid.

04:53 So now let's discuss the anatomy of the spinal cord.

04:57 Let's start with this external anatomy.

05:00 So extending from the spinal cord, we have two roots and rootlets.

05:06 These are the posterior roots and the anterior roots.

05:11 The posterior root also has a swelling called the posterior root ganglion.

05:17 Now let's move in and look at the internal anatomy of the spinal cord.

05:23 On the anterior portion of the spinal cord, we have a fissure known as the anterior median fissure.

05:29 On the posterior end, we have the posterior median sulcus.

05:35 In the center, we have the central canal.

05:39 Here is where we will find some of the cerebrospinal fluid In the white matter of the spinal cord in the anterior portion, we have the anterior white column.

05:53 On the lateral portion, we have the lateral white column and on the posterior portion, we have the posterior white column.

06:03 In the grey matter, we have on the anterior portion, the anterior grey horn.

06:10 On the lateral portion, the lateral grey horn.

06:15 In the center, the cross bar is referred to as the grey commissure and it gives the grey mater it's butterfly or H shape.

06:25 And then in the posterior portion, we have the posterior grey horn.