The main difference between tendon and aponeurosis is that a tendon is a tough band of connective tissue that attaches it to a bone, whereas aponeurosis is a thin sheet that connects a muscle to a bone or fascia.
Tendon and aponeurosis are two connective tissue types that occur in muscles. They attach muscles to bones.
Key Areas Covered
1. What is Tendon
– Definition, Facts, Function
2. What is Aponeurosis
– Definition, Facts, Function
3. Similarities Between Tendon and Aponeurosis
– Outline of Common Features
4. Difference Between Tendon and Aponeurosis
– Comparison of Key Differences
Key Terms
Aponeurosis, Tendon
What is Tendon
A tendon is a tough cord that connects muscles to the bones. It is made up of dense, white, fibrous connective tissue. This connective tissue mainly contains collagen fibers. A bunch of primary collagen fibers comprise the primary fiber bundle called subfascicle. A group of sub-fascicles forms the secondary fiber bundle called a fascicle. Several fascicles make up a tertiary fiber bundle called the tendon unit. An endotenon connective tissue layer covers each primary, secondary, and tertiary fiber bundle. The epitenon is the connective tissue layer that covers the tertiary fiber bundle.
Figure 1: Tendon
Furthermore, there are two types of cells in the tendon: tenocytes, the mature cells originating from fibrocytes, and tenoblasts, the immature cells originating from fibroblasts. Tenocytes are attached to the collagen fibers, while tenoblasts occur in clusters, secreting collagen and the extracellular matrix of the connective tissue. The main function of a tendon is to transmit the forces exerted by the muscles to the bones. Therefore, tendons occur at each end of a muscle. Due to the high tensile strength of a tendon, it can withstand the great pressure generated on it by the muscle.
What is Aponeurosis
An aponeurosis is a flattened tendon that attaches the muscle to a bone or fascia. It has an ordered arrangement of collagen fibers. Therefore, it peels off in sections. Also, it is similar to tendons histologically. It contains a tiny supply of blood vessels and nerves. Additionally, it can attain a high tensile strength in a particular direction. The color of the aponeurosis is a shiny whitish color. Thick aponeurosis occurs in the dorsal lumbar region, the ventral abdominal region, the ventriculus in birds, and the palmar (palms) and plantar (soles) regions.
Figure 2: Aponeurosis
Moreover, examples of aponeurosis include anterior abdominal aponeurosis, posterior lumbar aponeurosis, palmar and plantar aponeurosis and extensor hood, anterior and posterior intercoastal membranes, scalp aponeuroses, pennate muscles and aponeuroses, etc. The aponeuroses attached to pennate muscles, a type of skeletal muscle, are vulnerable to stretches during muscular contractions. They absorb energy as a spring and return, unloading the condition.
Similarities Between Tendon and Aponeurosis
- Tendon and aponeurosis are two types of connective tissues.
- They attach muscles to bones.
- They are made up of dense fibrous connective tissue.
Difference Between Tendon and Aponeurosis
Definition
Tendon refers to a flexible but inelastic cord of strong fibrous collagen tissue attaching a muscle to a bone. In contrast, aponeurosis refers to sheet-like elastic tendon structures that cover a portion of the muscle belly and act as insertion sites for muscle fibers.
Structure
Tendon is predominantly composed of collagen, while aponeurosis is a delicate, thin sheet of tissue that contains collagen-releasing cells called fibroblasts.
Function
Tendon is a cord of strong, flexible tissue that connects muscles to bones, while aponeurosis is a thin sheet of connective tissue that attaches muscles to bones or facia.
Conclusion
In brief, tendon and aponeurosis are two dense, fibrous connective tissue that attaches bones and muscles. The tendon is a connective tissue made up of collagen. It is a strong, flexible tissue. Also, it connects muscles to bones. In comparison, aponeurosis is a delicate, thin sheet of tissue that contains fibroblasts. Also, it attaches muscles to bones or other fascia. Therefore, the main difference between tendon and aponeurosis is their structure.
References:
- Tendon anatomy. Physiopedia. (n.d.-e). https://www.physio-pedia.com/Tendon_Anatomy
- Aponeurosis. Physiopedia. (n.d.-a). https://www.physio-pedia.com/Aponeurosis
Image Courtesy:
- “Tendon anatomy – Tendon Epimysium Fascicle Fiber Fibril etc — Smart-Servier” By OlafJanssen – Own Work (CC-BY SA 3.0) via Commons Wikimedia
- “Aponeurosis fibra muscular” By Ganímedes – Own work (CC BY-SA 3.0) via Commons Wikimedia
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