The main difference between annulus fibrosus and nucleus pulposus is that annulus fibrosus contains less water, whereas nucleus pulposus contains more water.
The annulus fibrosus and nucleus pulposus are the two parts of the intervertebral disc. Also, they contain water, collagen, and proteoglycans.
Key Areas Covered
1. What is Annulus Fibrosus
– Definition, Structure, Function
2. What is Nucleus Pulposus
– Definition, Structure, Function
3. Similarities Between Annulus Fibrosus and Nucleus Pulposus
– Outline of Common Features
4. Difference Between Annulus Fibrosus and Nucleus Pulposus
– Comparison of Key Differences
Key Terms
Annulus Fibrosus, Nucleus Pulposus
What is Annulus Fibrosus
Annulus fibrosus is a sturdy tire-like structure in the intervertebral disc, encasing the gel-like center, the nucleus pulposus. The primary function of the annulus fibrosus is to enhance the spine’s rotational stability, and it helps to resist compressive stress. On the other hand, the annulus fibrosus is a layered structure consisting of water and sturdy elastic collagen fibers.
Figure 1: Intervertebral Disc
Furthermore, it contains 60% of collagen and 20% of proteoglycans. The fibers construct a radial tire-like system by orienting at different angles horizontally. Collagen consists of fibrous bundles of protein, binding together by proteoglycan gel. Additionally, intervertebral discs are the most significant structures in the body with no vascular supply. Instead, they absorb nutrients through osmosis.
What is Nucleus Pulposus
The nucleus pulposus is the center portion of each intervertebral disc, filled with a gel-like elastic substance. The primary function of the nucleus pulposus is to transmit stress and weight from vertebra to vertebra together with the annulus fibrosus.
Figure 2: Intervertebral Disc Structure
Moreover, structure-wise, the nucleus pulposus comprises water, collagen, and proteoglycans. It contains 65% of proteoglycans and 20% of collagen. However, the main difference between the nucleus pulposus and annulus fibrosus is the containment of water. The nucleus pulposus contains more water.
Similarities Between Annulus Fibrosus and Nucleus Pulposus
- The Annulus fibrosus and nucleus pulposus are two parts of the intervertebral disk.
- They contain water, collagen, and peptidoglycans.
- They occur between the vertebral body forming a cushion.
- Their function is to absorb shock and stress during movement and prevent vertebrae from grinding against one another.
- They are the largest structures without blood supply.
- They absorb nutrients by osmosis.
Difference Between Annulus Fibrosus and Nucleus Pulposus
Definition
Annulus fibrosus is a fibrocartilaginous tissue consisting of layers of lamellae rich in highly cross-linked collagen fibrils. At the same time, nucleus pulposus refers to more amorphous with a small percentage of randomly oriented fibrils and a significant content of proteoglycans.
Anatomy
Annulus fibrosus is the tough circular exterior of the intervertebral disc surrounding the soft inner core, the nucleus pulposus. Meanwhile, the nucleus pulposus is the soft, gelatinous central portion of the intervertebral disk that moves within the disk with changes in posture.
Occurrence
Annulus fibrosis occurs in the exterior of the intervertebral disc, while nucleus pulposus occur interior of the intervertebral disc.
Composition
Annulus fibrosus contains 20% proteoglycan and 60% collagen, while nucleus pulposus contains 65% proteoglycan and 20% collagen.
Water
Annulus fibrosus contain less water, while the nucleus pulposus contains more water.
Function
The Annulus fibrosus enhances the spine’s rotational stability and helps resist compressive stress, while the nucleus pulposus allows the spine to absorb shock.
Conclusion
In brief, the annulus fibrosus and nucleus pulposus are two parts of the intervertebral disk. They compose of water, proteoglycan, and collagen. Their function is to absorb shock. Annulus fibrosus is a fibrocartilage tissue occurring exterior of the intervertebral disc. It contains 20% proteoglycan and 60% collagen. Also, it has less water. Its function is to maintain the rotational stability of the spine.
In comparison, the nucleus pulposus is the interior of the intervertebral disc, which is soft and gelatinous. It contains 65% proteoglycan and 20% of collagen. Also, it has less water. It absorbs shock. Therefore, the main difference between annulus fibrosus and nucleus pulposus is their structure and function.
References:
- Intervertebral Disc. Physiopedia. (n.d.-b).
Image Courtesy:
- “Annulus Fibrosus.” By BruceBlaus – Own work (CC-BY SA 4.0) via Commons Wikimedia
- “Cervical vertebra english.” By user:debivort – Own Work (CC-BY SA 3.0) via Commons Wikimedia
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