Exoskeleton vs Endoskeleton
Body of a living organism is a complex network of different organs having several functions of their own besides being connected to each other for a harmonious, balanced and functional body be it a honey bee or a human being. All are complex marvels of nature as every species has a special feature of its own. Some has only endoskeleton some only exoskeleton and some has both for support. Mainly a living thing has a network of an exoskeleton and or an endoskeleton. The external skeleton which protects and also supports an animal’s body is called exoskeleton. Endoskeleton on the other hand is referred to as the internal networks of skeletal systems which gives support and protection to both the inner softer and fragile organs like heart, lungs, and kidneys and also give grounds on which exoskeleton can play its role if the particular specie has the second feature as well.
The fossil record of mineralized exoskeleton came to light around 550 million years ago. Exoskeleton is very resistant, rigid and somewhat brittle and hard that has specific roles for example excretion of waste products produced inside of the body of an animal or anthropod, support for movement and safety of inner softer organs, sensing and feeding are very important and complex features of exoskeleton. It contains calcium carbonate and/or chitin. In simple language it can be called as a shell. Organisms like snails, crabs, lobsters, shellfish cockroaches, crustaceans and insects like grasshoppers have exoskeleton and some animals like tortoise are blessed with both endoskeleton and exoskeleton.
Mineralized tissue which gives support to the internal structure of an animal is called as Endoskeleton and develops in deeper body tissues and organs. During the embryonic life its development is derived from mesodermal tissue and formed by notochord and cartilage. Which later during the rest of intrauterine life or fetal life goes through stages of intra-membranous ossification and extra-membranous ossification which finally leads to a network of bones, cartilage and secondary cartilage all these combine to form an endoskeleton. There are different forms and types of endoskeletons which differ in development and complexity. Some examples are Chordates, Coleoidea, Porifera and Echinodermatas. Functions of endoskeleton include support, protection and ability to move and have a rigid profile because they serve as attachment sites for muscles and so transmit muscular forces helping in locomotion.
So in short endo means part of body that is inside and exo means part of body outside in this particular matter. Endoskeleton is what we humans have. Examples of exoskeleton containing animals and insects have been given. Both above have some similar functions like support, movement, protection and some different features like exoskeleton helps in excretion but endoskeleton does not. In the same way endoskeleton has bone marrow in shaft of long bones which helps in making blood cells by the process of endothelial proliferation for the body this feature is not present in exoskeleton. Exoskeleton mostly contains the non living portions of the body for example scales on fish, hair on most animals, horns, feathers on birds but the inside of these feather to which muscle is attached ,the hard part is the endoskeleton and is the living portion of body which responds to stimuli from brain. In terms of development endoskeleton develops from mesoderm or endoderm and exoskeleton from ectoderm.