In this low magnification view, the gray matter (GM) of the spinal cord is stained with a pink hue and the surrounding white matter (WM) has a blue tint due to the use of the myelin stain, luxol fast blue. [6-2]:Light Microscopic Slide, Spinal Cord, Myelin and Nissl stains, 10x lens (#20)-
This slide shows a higher magnification view of the central region of the spinal cord. Note the central canal and a small amount of white matter in the periphery. [6-3]:Light Microscopic Slide, Spinal Cord, Myelin and Nissl stains, 40x lens (#20)-
At high magnification, cross sections of axons (Ax) are seen as small pink structure surrounded by blue circles representing their myelin sheaths (My). The apparent space between the axon and its myelin sheath is an artifact of preparation. Recall that Schwann cells are responsible for the peripheral myelin while oligodendrocytes myelinate axons in the central nervous system. The myelin is somewhat different chemically and the luxol fast blue procedure detects this difference. [6-4]:Light Microscopic Slide, Spinal Cord, Myelin and Nissl stains, 40x lens (#20)-
Examine the multipolar neurons in the gray matter. The largest of these are usually seen in the ventral horns. The cell bodies (perikarya, soma) are present which represent stacks of RER and free polysomes. The blue-staining Nissl bodies (NB) extend into the larger dendrites (Den) of the neurons but are absent in the axon as well as the axon hillock of the cell body from which it arises (the hillock is not apparent in this slide). Also note the red-staining granules of lipofuscin (Lip) also known as residual bodies or secondary lysosomes present in the parakaryon. The 'Nissl stain" used also stains the nucleolus of the neurons and the nuclei (chromatin and nucleoli) of glial cells within the spinal cord. [6-5]:Light Microscopic Slide, Spinal cord, silver impregnation 1x lens (#19)-
This low power view shows the central gray matter (GM) surrounded by the white matter (WM). [6-6]:Light Microscopic Slide, Spinal cord, silver impregnation 40x lens (#19)-
This high power view, shows that neuron cell bodies (Perik) and processes contain cytoskeletal elements termed neurotubules and neurofilaments (NF). So numerous are these elements that so-called neurofibrils can be seen by light microscopy after nervous tissue has been impregnated with silver salts. Find the cell bodies of the large motor neurons in this slide of spinal cord stained by silver impregnation. Identify the neurofibrils which are located in the perikaryon and extend out into the dendrites (Den) and the larger axons. [6-7]:Transmission Electron Micrograph, Spinal cord, x 12,000 (#6-1)-
Examine the neuron cell body with a large euchromatin nucleus (Nuc), and clumps of RER (RER), Golgi complexes (Gol), mitochondria (Mit) and other cytoplasmic organelles. Note also the presynaptic terminals (PreST) filled with synaptic vesicles (SV), that are making synaptic contact with this neuron (axosomatic synapses). Myelinated axons (MA) are also present and a complexity of other cell processes that cannot be readily identified at this magnification. [6-8]:Transmission Electron Micrograph, Spinal cord x 30,000 (#6-2)-
At higher magnification, the nucleus (Nuc) RER and a Golgi complex (Gol) within the perikaryon of this neuron may be seen in greater detail. [6-9]:Transmission Electron Micrograph, Spinal cord, x 48,000 (#6-4)-
In the CNS, neuronal and non-neuronal processes are interspersed in a complex fashion. In this section identify myelinated axons (MA), and un-myelinated axon terminals (AT) which contain synaptic vesicles (SV). The terminals make synaptic contact with a dendrite (1) to form axodendritic synapses. Neurotubules (NT) and neurofilaments can be seen in the neuronal processes. Portions of an astrocyte process (6) are present but are difficult to identify as such in this section. Note the absence of connective tissue elements and the close packing of cell processes in the CNS. [6-10]:Transmission Electron Micrograph, Spinal cord, x 28,000 (#6-6)-
Processes of non-neuronal cells normally form a boundary between nervous and non-nervous tissue. In the CNS, astrocyte cell processes perform this function and a basal lamina is formed on the side of the astrocyte facing the non-nervous tissue of an endothelial cell (Endo). In this micrograph, note the astrocyte cell process (AP) that surrounds a capillary (Cap) in the spinal cord and the basal lamina (4) that has formed. [6-11]:Light Microscopic Slide, Cerebrum, cresyl violet - luxol fast blue, 1 x lens (#26)-
In the cerebral hemispheres there is a complex, highly convoluted outer covering cortex of gray matter (GM) and an inner layer of white matter (WM). In this low power slide, myelin in the white matter is stained blue with the luxol fast blue technique and neuron cell bodies in the cortex are stained with the Nissl stain, cresyl violet. [6-12]:Light Microscopic Slide, Cerebrum, cresyl violet - luxol fast blue, 20 x lens (#26)-
A higher power view of the white matter shows the light blue-staining myelin and darker staining nuclei. [6-13]:Light Microscopic Slide, Cerebrum, cresyl violet - luxol fast blue, 20 x lens (#26)-
A higher power view of the outer gray matter shows the neuron cell bodies are arranged in layers (generally 6) of similar types. Most of the neuron cell bodies are pyramidal (Py), stellate or granular (Gr) or spindle shaped or fusiform (Sp). [6-14]:Light Microscopic Slide, Cerebellum, silver, 10x lens (#26)-
The cerebellum consists of a cortex of gray matter (GM) which has an irregular contour due to numerous transverse folds and a medullary center of white matter (WM). Three layers of neuron cell bodies are evident in the cortex, the outer molecular layer (OML), the middle Purkinje cell layer (PCL) and the inner granule cell layer (IGL). [6-15]:Light Microscopic Slide, Cerebellum, silver, 40x lens (#26)-
This high power view shows the large flask-shaped Purkinje cells (PC). Each Purkinje cells has an initial segment of the single axon and a "dendrite tree" (Den) on the opposite side. [6-16]:Light Microscopic Slide, Sensory ganglion, H&E, 40x lens (#23)-
As the sensory neurons are pseudounipolar and their cell bodies appear round in sections. They contain a large, centrally located euchromatic (vesicular) nucleus (Nuc) with a prominent nucleolus. The cell body is surrounded by a single layer of flattened satellite cells or capsule cells (Sat). A single process leaves the cell body and bifurcates to form the central and peripheral process that travel respectively to the CNS and sensory end organs. Both processes are morphologically and functionally axons. The processes are insheathed and become myelinated by Schwann cells that are continuous with the satellite cells covering the cell body. Bundles of these myelinated axons can be seen between groups of cell bodies. [6-17]:Light Microscopic Slide, Autonomic ganglion, H&E, 40 x lens (#24)-
The histological appearance of sympathetic and parasympathetic neurons is similar. The neurons are multipolar and therefore sections through autonomic ganglia show irregularly-shaped cell bodies. The nuclei (Nuc) are usually eccentrically located and the cytoplasm often contains orange-red lipofuscin granules. Satellite cells (Sat) are less numerous than in sensor ganglia and the capsule they form around the cell body appears incomplete. Schwann cells insheath the axons from these ganglionic neurons but the axons are unmyelinated. [6-18]:Light Microscopic Slide, Nerve trunk, H&E, 10x lens (slide #21)-
This slide shows a cross-section through the large sciatic nerve. In the cross-section, identify the epineurium (Epi) and the perineurium (Peri) surrounding each of the many fascicles, and the nuclei of fibroblasts of the endoneurium (Endo), the connective tissue between individual axons in a fascicle. In such a routine preparation, the myelin has been dissolved by the organic solvents used in processing. [6-19]:Light Microscopic Slide, Nerve trunk, H&E, 40x lens (slide #21)-
In this higher power view, the axons appear as small pink dots surrounded by a clear space (that has contained myelin). A rim of pink-stained cytoplasm of the insheathing Schwann cell (Sch) may be seen external to this clear space. In some cases the flattened nucleus of the Schwann cell may also be seen. [6-20]:Light Microscopic Slide, Nerve trunk, H&E, 40x lens (slide #21)-
In this longitudinal section, identify nodes of Ranvier (NR) as well as the Schwann cells (Sch) and axons (Ax). [6-21]:Light Microscopic Slide, Nerve trunk, Osmic acid, 40x lens (slide #22)-
Osmic acid used in this preparation has both fixed and blackened the myelin. In the longitudinal section, the nodes of Ranvier (NR) are clearly seen as unstained gaps along the length of myelinated axons. [6-22]:Transmission Electron Micrograph, Fascicle of Peripheral Nerve x 15,000 (#6-7)-
This is a cross-section of a very small fascicle of nerve surrounded by a perineurium which consists of a single perineural cell. Within the fascicle, endoneurium consisting of collagen fibrils (CF) and fibroblast process present in-between myelinated (My) and unmyelinated (UMy) axons. Both are insheathed by Schwann cells (Sch) and a basal lamina is visible on the surface of the Schwann cells contacting the endoneurial connective tissue. [6-23]:Transmission Electron Micrograph, Peripheral nerve, adrenal gland x 40,500 (#6-3)-
In this longitudinal section of a myelinated axon innervating the adrenal gland, note the fine structure of the axoplasm (Ax), the myelin lamellae (My), the cytoplasm of the Schwann cell (Sch) and its external mesaxon (Mx). At the top of the micrograph, the beginning of a node of Ranvier is seen in oblique section. Note how the myelin lamellae appear to "open up" and the layers of Schwann cell cytoplasm that are visible. [6-24]:Light Microscopic Slide, Skin, H&E, 20x lens (slide #47)-
Meissner's corpuscle (MC) beneath the epidermis of the finger tips, sole of foot, etc., which are responsive to light touch are composed of unmyelinated nerve terminals surrounded by a delicate connective tissue capsule. They are generally found in the tips of the finger-like projections of the dermis (Der) into the epidermis (Epid) mear capillaries (Cap). [6-25]:Light Microscopic Slide, Skin, H&E, 10x lens (slide #52)-
Pacinian corpuscles (PC) are sensitive to deep touch, pressure and vibrations. These large bodies are composed of nerve endings surrounded by a series of concentric layers of connective tissue. [6-26]:Light Microscopic Slide, Muscle Spindle, H&E, 20x lens (slide #15)-
Muscle receptors (muscle spindles and tendon organs) are present in muscles and tendons and mediate proprioception (awareness of the position of the body or its parts). This sensory modality is activated by pulling or stretching a muscle tendon. Examine this slide showing a muscle spindle (MS).