medullary sheath
Noun: * A protective, insulating layer: The medullary sheath is a specialized, fatty covering that surrounds and insulates the axons of certain nerve fibers. Its primary function is to increase the speed and efficiency of electrical signal transmission along the nerve cell.
The term "medullary sheath" is a technical, anatomical term used primarily in biology, medicine, and neuroscience. It describes a specific structure and is not used in everyday conversation.
Examples: * The medullary sheath is essential for the rapid conduction of neural impulses. * Damage to the medullary sheath, as seen in multiple sclerosis, can severely impair neurological function. * Under the microscope, the medullary sheath appears as a glossy, white layer around the axon.
- "Demyelination": This is the process of damage or loss of the medullary sheath. It is a key pathological feature in several neurological diseases.
- The disease causes progressive demyelination of the central nervous system.
- "Myelinated" vs. "Unmyelinated": These adjectives describe whether a nerve fiber is encased in a medullary sheath or not.
- Myelinated axons conduct signals much faster than unmyelinated ones.
- Myelin sheath: This is the most common synonym for "medullary sheath." In modern scientific literature, "myelin sheath" is more frequently used.
- Myelin (noun): The fatty substance that constitutes the medullary sheath.
- Myelination (noun): The process of forming a medullary sheath around an axon.
- Myelin sheath: The direct and most common synonym.
- White matter: In a broader anatomical context, large collections of myelinated axons in the brain and spinal cord are referred to as white matter due to the color of myelin.
The term "medullary sheath" is highly specific to neuroanatomy. It does not have other common meanings in general English. The word "medullary" itself can refer to other central or inner parts of structures (e.g., renal medulla in the kidney, medullary bone in birds), but the compound "medullary sheath" refers exclusively to the insulating layer of nerve fibers.
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a layer of myelin encasing (and insulating) the axons of medullated nerve fibers
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