medulla

/me'dʌlə/

Thân thiện

The diagram shows the medulla at the base of the brain.

Definition

1. Noun:
   • The inner region of an organ or structure: In biology, "medulla" refers to the innermost part of an organ or anatomical structure, distinct from the outer layer (cortex). This applies to both plants and animals.
   • The medulla oblongata: Specifically, it is the lower portion of the brainstem, continuous with the spinal cord. It controls vital autonomic functions like breathing and heart rate.
   • A core of soft tissue: In botany, it can refer to the soft, spongy parenchyma tissue in the center of a plant stem or root.
   • Myelin sheath material: In neuroanatomy, it can denote the white, fatty substance (myelin) that forms an insulating sheath around some nerve fibers.

Usage Examples

• Noun (General Anatomy):
  • The adrenal gland has an outer cortex and an inner medulla.
  • The renal medulla contains the loops of Henle and collecting ducts.
• Noun (Neuroanatomy - Medulla Oblongata):
  • Damage to the medulla can be life-threatening.
  • The medulla regulates essential reflexes like swallowing and vomiting.
• Noun (Botany):
  • The pith, or medulla, of the stem stores nutrients.

Advanced Usage

• "Medulla oblongata": This is the full anatomical term for the specific part of the brainstem. It is often simply called "the medulla" in medical contexts.
  • The cardiac and respiratory centers are located in the medulla oblongata.
• In a figurative or technical sense, "medulla" can describe any central, core, or essential part of a structure or system.
  • The argument struck at the very medulla of the issue.

Variants and Related Words

• Medullary (adj): Of or relating to a medulla or resembling marrow.
  • Medullary bone; medullary cavity.
• Myelinated (adj): (Of a nerve fiber) having a medullary sheath.
  • Myelinated axons conduct impulses faster.

Synonyms

• Core: The central or most important part.
• Pith: (Especially in botany) the soft, spongy central cylinder.
• Marrow: The soft, fatty substance in the cavities of bones (a related but not identical concept).

Antonyms

• Cortex: The outer layer of an organ or structure, such as the cerebral cortex or adrenal cortex.

Related Phrases/Compounds

• Adrenal medulla: The inner part of the adrenal gland, which secretes epinephrine and norepinephrine.
• Renal medulla: The inner region of the kidney.
• Medulla spinalis: A Latin term for the spinal cord.

Học thuật

Noun

1. the inner part of an organ or structure in plant or animal
2. lower or hindmost part of the brain; continuous with spinal cord; (`bulb' is an old term for medulla oblongata)
   • the medulla oblongata is the most vital part of the brain because it contains centers controlling breathing and heart functioning
3. a white fatty substance that forms a medullary sheath around the axis cylinder of some nerve fibers

Từ đồng nghĩa

• medulla oblongata
• bulb
• myelin
• myeline