What Is The Difference Between Endoskeleton and Exoskeleton?

What is the difference between endoskeleton and exoskeleton? The endoskeleton is hard to part found inside the body while the exoskeleton is hard to part found outside the body.

The endoskeleton and exoskeleton are parts of the body of a living organism. It has a complicated network of various organs. Endoskeleton is the hard part which is the internal support of the structure and it is developed from endoderm. It is called a living structure.

The exoskeleton is the hard part that is outside the body and it protects the inner soft tissues and muscles. It develops from ectoderm and mostly referred to as a non-living structure.

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Difference Between Endoskeleton and Exoskeleton With Table

Characteristics Endoskeleton Exoskeleton
Where located It is found inside the body. It is found outside the body.
Development In vertebrates; cartilage and bones are deposited. In arthropods; chitin and proteins are deposited.
Body size Support large body size. Support small body size.
Movement By muscles pulling on the joint. By jointed appendages
Protection from predators By moving away. Modification such as spikes or camouflage.
Protection from sources Strong protection. Usually, not very strong protection.
Repair and replacement It takes a long time to repair or replace. Can be replaced quickly.
Blood supply Bones contain blood supply. It has no blood supply.
Structure It is a living structure. It is a non-living structure.
Flexibility More flexible. Less flexible.
Blood Vessel Has Blood capillaries Lack blood capillaries
Support Large body size Small body size
Growth Grow with the body Does not grow with the body
Develop Endoderm Ectoderm
Components Calcium and Phosphorus Scales, chitinous cuticle, or calcified shells.
Examples They include chordates including all vertebrates. They include; arthropods, crustaceans, and mollusks.

What is Endoskeleton?

An endoskeleton is a structural framework located inside the body of an organism. It provides support, protection, and attachment points for muscles and other tissues. An endoskeleton is located within the body, typically made of bone or cartilage in vertebrates, although other materials can serve this purpose in different animals.


In vertebrates, the endoskeleton consists primarily of bones and cartilage. Bones are hard and rigid structures made of a dense matrix of collagen fibers and minerals, such as calcium and phosphate. Cartilage is a more flexible and rubbery connective tissue that is found in areas where some flexibility is required, such as the joints.


Support: One of the primary functions of the endoskeleton is to provide structural support for the body. It gives the body its shape and maintains its integrity, preventing it from collapsing under the force of gravity.

Protection: The endoskeleton also protects vital internal organs. For example, the skull protects the brain, the ribcage shields the heart and lungs, and the vertebral column surrounds and supports the spinal cord.

Muscle Attachment: Muscles, tendons, and ligaments attach to various parts of the endoskeleton, allowing for movement and locomotion. The bones serve as levers, and when muscles contract, they pull on these levers to generate movement.

Blood Cell Production: In vertebrates, some bones, such as the long bones in the limbs, contain marrow, where blood cells are produced.


The structure and composition of the endoskeleton can vary among different groups of organisms. For instance, vertebrates have a vertebral column (spine) composed of individual vertebrae, while arthropods (such as insects) have segmented endoskeletons consisting of exoskeletal plates and joints.

In some animals, like certain fish and reptiles, the endoskeleton is not completely ossified (turned into bone), allowing for more flexibility.

Growth and Repair

In vertebrates, bones can grow and repair themselves throughout an organism’s life. The process of bone growth involves the deposition of new bone tissue by specialized cells called osteoblasts. When bones are damaged or fractured, they can also undergo a repair process, where osteoblasts help mend the injury.

Evolutionary Significance
The evolution of the endoskeleton played a significant role in the diversification and success of vertebrates. It allowed for greater body size, mobility, and protection of vital organs.

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What is Exoskeleton?

An exoskeleton is a rigid, external protective covering or framework found on the outside of an organism’s body. It serves several important functions, including support, protection, and defense against environmental factors and predators.

Exoskeletons are primarily associated with arthropods, such as insects, crustaceans, and arachnids, although other organisms, like some mollusks, also have exoskeletal structures.


Exoskeletons are typically composed of a tough and durable material called chitin, which is a complex carbohydrate. Chitin provides the exoskeleton with rigidity and strength, allowing it to serve as a protective shield.

In addition to chitin, exoskeletons may contain other materials like calcium carbonate, as seen in the shells of many crustaceans.


Support: The primary function of an exoskeleton is to provide structural support for the organism’s body. It gives the organism its shape and prevents it from collapsing under the force of gravity.

Protection: The exoskeleton acts as armor, protecting the organism from physical injuries, predators, and environmental hazards such as desiccation (drying out) and UV radiation.

Attachment for Muscles: Muscles attach to the inner surface of the exoskeleton, allowing for movement and locomotion. When muscles contract, they move the appendages, causing the exoskeleton to act like a lever system.

Preventing Water Loss: In terrestrial arthropods, the exoskeleton helps reduce water loss, acting as a barrier against desiccation. Many arthropods also have specialized structures, such as waxy layers, to further prevent water loss.

Molting: To accommodate growth, arthropods must periodically shed their exoskeletons in a process called molting. A new, larger exoskeleton is secreted underneath the old one. After molting, the organism expands its body to fill the new exoskeleton.


Exoskeletons can be highly modified and adapted to suit specific lifestyles and ecological niches. For example, the exoskeletons of insects are often lightweight to facilitate flight, while those of crustaceans are adapted for underwater environments.

Some arthropods, like spiders, have a modified exoskeleton that forms a silk-spinning apparatus, enabling them to produce silk for building webs or capturing prey.

Growth and Limitations

An exoskeleton provides protection and support, but it poses a challenge for growth. As the organism grows, its exoskeleton becomes too small, necessitating the process of molting to accommodate the increased body size.

During the period immediately after molting, when the new exoskeleton is still soft and pliable, the organism is vulnerable to predation and environmental stress.

Evolutionary Significance

The development of exoskeletons was a crucial step in the evolution of various arthropods, enabling them to colonize diverse terrestrial and aquatic habitats and contributing to their evolutionary success.

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Main Difference between Endoskeleton and Exoskeleton

  1. Endoskeleton is found inside the body while the exoskeleton is found outside the body.
  2. The endoskeleton supports a large body size while the exoskeleton supports a small body size.
  3. The endoskeleton moves muscles by pulling on the joints while the exoskeleton moves the jointed appendages.
  4. Endoskeleton protects themselves from predators by moving away while exoskeleton protect themselves by developing spikes or camouflaging.
  5. It takes a long time to repair and replace the endoskeleton while it takes a shorter time to replace the exoskeleton as the animals molt.
  6. Endoskeleton is living structures while exoskeleton is non-living structures.
  7. Endoskeleton is more flexible while the exoskeleton is less flexible.

Similarities between Endoskeleton and Exoskeleton

  1. They are both made of hard parts.
  2. They both give support to the body of an organism.

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In Conclusion

In conclusion, endoskeletons and exoskeletons represent two distinct structural systems in the animal kingdom, each with its own set of characteristics and advantages.

Endoskeletons, found primarily in vertebrates, consist of internal bones or cartilage that provide support, protection for vital organs, and attachment points for muscles. They allow for greater flexibility, growth, and repair while offering efficient locomotion and diverse body shapes.

Exoskeletons, on the other hand, are external protective coverings made of materials like chitin, primarily seen in arthropods. They serve as armor, preventing physical injuries and protecting against environmental hazards. Exoskeletons also offer structural support and muscle attachment points but pose challenges related to growth and molting.

These differences in skeletal systems highlight the remarkable adaptability of organisms in the animal kingdom. The evolution of endoskeletons and exoskeletons has enabled various species to thrive in a wide range of ecological niches, contributing to the rich diversity of life on Earth.

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