An exoskeleton is a type of skeleton that is an external anatomical feature that supports and protects an animal's body, in contrast to the internal endoskeleton of, for example, a human. In Biology, the skeleton is a strong and often a rigid framework that supports the body of an animal holding it upright and giving it shape and strength (Also skeletal Anatomy (from the Greek anatomia, from ana separate apart from and temnein, to cut up cut open is a branch of Biology that is the consideration An endoskeleton is an internal support structure of an Animal. Whilst many, many other invertebrate animals (such as shelled mollusks) have exoskeletons in the sense of external hard parts, the characteristic is most associated with the arthropods (i. An invertebrate is an Animal lacking a Vertebral column. The group includes 98% of all animal Species — all animals except those in the Chordate Molluscs are animals belonging to the phylum Mollusca. There are around 250000 extant Species within the phylum with an estimated 70000 Arthropods are Animals belonging to the Phylum Arthropoda (from Greek ἄρθρον arthron, " Joint " e. insects, spiders, myriapods and crustaceans). Insects ( Class Insecta) are a major group of Arthropods and the most diverse group of Animals on the Earth with over a million described Spiders are Predatory Invertebrate Animals that have two body segments, eight legs no chewing mouth parts and no wings Myriapoda is a Subphylum of Arthropods containing Millipedes Centipedes and others Structure of crustaceans As Arthropods crustaceans have a stiff Exoskeleton, which must be shed to allow the animal to grow ( Ecdysis or molting Exoskeletons contain rigid and resistant components that fulfil a set of functional roles including protection, excretion, sensing, support, feeding and (for terrestrial organisms) acting as a barrier against desiccation. Exoskeletons first appeared in the fossil record about 550 million years ago, and their evolution has been seen as a critical driving role in the Cambrian explosion of animals that took place subsequent to this time. The Cambrian explosion or Cambrian radiation was the seemingly rapid appearance of most major groups of complex Animals around, as evidenced by the
Contents |
Arthropod exoskeletons
Microscopic structure
A typical arthropod exoskeleton is a multi-layered structure with four functional regions: epicuticle, procuticle, epidermis and basement membrane. The epicuticle is the outermost portion of the Exoskeleton of an Insect (and various other Arthropods; its exact composition and structure may differ somewhat The procuticle is the major portion of the Exoskeleton of an Insect (and various other Arthropods; its exact composition and structure may differ somewhat The basement membrane is a structure that supports overlying Epithelial or Endothelial cells. [1]. Of these, the epicuticle is a multi-layered external barrier that, especially in terrestrial arthropods, acts as a barrier against dessiccation. The epicuticle is the outermost portion of the Exoskeleton of an Insect (and various other Arthropods; its exact composition and structure may differ somewhat The strength of the exoskeleton is provided by the underlying procuticle, which is in turn secreted by the epidermis. The procuticle is the major portion of the Exoskeleton of an Insect (and various other Arthropods; its exact composition and structure may differ somewhat Arthropod cuticle is a biological composite material, consisting of two main portions: fibrous chains of alpha-chitin within a matrix of silk-like and globular proteins, of which the most well-known is the rubbery protein called resilin. Composite materials (or composites for short are engineered Materials made from two or more constituent materials with significantly different physical or chemical Chitin ( C 8 H 13 O 5 N)n (ˈkaɪtən is a long-chain Polymer of a N-acetylglucosamine Resilin is an Elastomeric Protein found in many Arthropods As of 2005 it is the most efficient elastic protein known (Elvin et al 2005 The relative abundance of these two main components varies from approximately 50/50 to 70/30 protein/chitin, with softer parts of the exoskeleton having a higher proportion of chitin. Although the cuticle is relatively soft when first secreted, it soon hardens in a poorly-understood process that involves dehydration and/or tanning mediated by hydrophobic chemicals called phenolics. Dehydration ( hypohydration) is the removal of Water ( hydro in ancient Greek) from an object Tanning is the process of converting Putrescible skin into non-putrescible Leather, usually with Tannin, an Acidic Chemical compound In Chemistry, hydrophobicity (from the combining form of water in Attic Greek hydro- and for fear phobos) refers to the physical property of In Organic chemistry, phenols, sometimes called phenolics, are a class of Chemical compounds consisting of a Hydroxyl group (- Different types of interaction between the proteins and chitin leads to varying mechanical properties of the exoskeleton.
In addition to the chitino-proteinaceous composite of the cuticle, many crustaceans, some myriapods and the extinct trilobites further impregnate the cuticle with mineral salts, above all calcium carbonate, which can make up up to 40% of the cuticle. Structure of crustaceans As Arthropods crustaceans have a stiff Exoskeleton, which must be shed to allow the animal to grow ( Ecdysis or molting Myriapoda is a Subphylum of Arthropods containing Millipedes Centipedes and others Trilobites ("three-lobes" are extinct Arthropods that form the class Trilobita. This can lead to great mechanical strength.
Organization
The arthropod exoskeleton is typically divided into different functional units to allow flexibility in an often otherwise rigid structure. Ants are social Insects of the family Formicidae and along with the related families of Wasps and Bees belong to the order For example, the head is a fused capsule; and the trunk is often divided into a series of articulating sclerites called tergites. A tergum (plural terga, associated adjective tergal) is the dorsal portion of an Arthropod segment other than the head In addition, the characteristic limbs of arthropods need to be jointed. The internal surface of the exoskeleton is often elaborated into a set of specialised structures called apodemes that allow the attachment of muscles. Such endoskeletal components of the arthropod skeleton can be highly complex, as in crabs and lobsters.
Ecdysis
- See also main article: Ecdysis
The relative rigidity of the exoskeleton means that continuous growth of arthropods is not possible. Therefore, growth is periodic and concentrated into a period of time when the exoskeleton is shed, called moulting or ecdysis, which is under the control of a hormone called ecdysone. In Biology, moulting (or molting, also known as shedding or for some species Ecdysis) signifies the manner in which an animal routinely Ecdysis is the Molting of the Cuticula in Arthropods and related groups ( Ecdysozoa) Ecdysone is a Steroidal Prohormone of the major insect molting hormone 20-hydroxyecdysone, which is secreted from the Prothoracic glands Moulting is a complex process that is invariably dangerous for the arthropod involved. Before the old exoskeleton is shed, the cuticle separates from the epidermis through a process called apolysis. New cuticle is excreted by the underlying epidermis, and mineral salts are usually withdrawn from the old cuticle for re-use. After the old cuticle is shed, the arthropod typically pumps up its body (for example, by air or water intake) to allow the new cuticle to expand to a larger size: the process of hardening by dehydration of the cuticle then takes place. Newly molted arthropods typically appear pale or white, and darken as the cuticle hardens.
Natural exoskeletons
Excellent as defensive adaptation, exoskeletons may nevertheless cause problems where entities carry an excessive weight to surface-area ratio or whenever organism growth requires an enlargement of the exoskeleton. An adaptation is a characteristic of an Organism that has been favored by Natural selection and Exoskeletons are found on many different types of organisms including shellfish and insects.
Types
- Bone and cartilage
- Ostracoderms (extinct armoured fish)
- Turtles, Terrapins and Tortoises
- Chitin
- Arthropods
- some Bacteria
- Calcium compounds
- Silicate
Artificial human exoskeletons
Humans have long used armour as an artificial exoskeleton for protection, especially in combat. Bones are rigid organs that form part of the Endoskeleton of Vertebrates They function to move support and protect the various organs of the body produce Cartilage is a type of dense Connective tissue. It is composed of specialized cells called chondrocytes that produce a large amount of extracellular matrix Ostracoderms ("shell-skinned" are any of several groups of extinct, primitive jawless Fishes that were covered in an armor of bony plates Turtles are Reptiles of the Order Testudines (all living turtles belong to the Crown group Chelonia) most of A terrapin is a Turtle that lives in fresh or Brackish water Taxonomy Although sometimes superficially similar to Sea turtles Tortoises or land Turtles are land-dwelling Reptiles of the family of Testudinidae', order Testudines. Chitin ( C 8 H 13 O 5 N)n (ˈkaɪtən is a long-chain Polymer of a N-acetylglucosamine Arthropods are Animals belonging to the Phylum Arthropoda (from Greek ἄρθρον arthron, " Joint " The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have Calcium (ˈkælsiəm is the Chemical element with the symbol Ca and Atomic number 20 Corals are Marine organisms from the class Anthozoa and exist as small Sea anemone –like Polyps typically in colonies of many Echinoderms (Phylum Echinodermata) are a phylum of marine Animals (including Sea stars) Molluscs are animals belonging to the phylum Mollusca. There are around 250000 extant Species within the phylum with an estimated 70000 The Polychaeta or polychaetes are a class of Annelid worms generally marine For the Artificial intelligence Androids of the 1990s Science fiction series Space Above and Beyond, see Silicate (AI Diatoms ( Greek: (dia = "through" + (temnein = "to cut" i Radiolarians (also radiolaria) are Amoeboid Protozoa that produce intricate Mineral Skeletons typically with a central capsule Human beings, humans or man (Origin 1590–1600 L homō man OL hemō the earthly one (see Humus Armour (or armor) is protective covering most commonly manufactured from metals to prevent damage from being inflicted to an individual or a vehicle through use of direct contact Exoskeletal machines are also starting to be used for medical and industrial purposes, while powered human exoskeletons are a feature of science fiction writing, but are currently moving into prototype stage. A powered Exoskeleton is a powered mobile machine consisting primarily of a skeleton-like framework worn by a person and a power supply that supplies at least part of the Orthoses are a limited, medical form of exoskeleton. An orthosis (sometimes called an orthesis) is a device that is applied externally to a part of the Body to correct Deformity, improve function or relieve
In history
In medicine
An orthosis (plural orthoses) is a device which attaches to a limb, or the torso, to support the function or correct the shape of that limb or the spine. An orthosis (sometimes called an orthesis) is a device that is applied externally to a part of the Body to correct Deformity, improve function or relieve Orthotics is the field dealing with orthoses, their use, and their manufacture. Orthotics is an allied health care medical profession or field that is concerned with the design development fitting and manufacturing of Orthoses, which are devices that support An orthotist is a person who designs and fits orthoses. An orthotist is a person who measures designs fabricates fits or services Orthoses, and/or assists in the formulation of orthoses
A limb prosthesis (plural prostheses) is a device that substitutes for a missing part of a limb. In Medicine, a prosthesis (plural prostheses) is an Artificial extension that replaces a missing Body part. If the prosthesis is a hollow shell and self-carrying, it is exoskeletal. If internal tubes are used in the device and the cover (cosmesis) to create the outside shape is made of a soft, non-carrying material, it is endoskeletal. Cosmesis is the preservation restoration or bestowing of bodily beauty Prosthetics is the field that deals with prostheses, use, and their manufacture. In Medicine, a prosthesis (plural prostheses) is an Artificial extension that replaces a missing Body part. A prosthetist is a person who designs and fits prostheses. A prosthetist, as defined by The American Board for Certification in Orthotics Prosthetics and Pedorthics Inc
In modern and near-future technology
References
See also
- Mechatronics
- Spiracle - Small openings in the exoskeleton that allow insects to breathe
External links
Biology
Modern technology
- Bionic Boots
- PowerSkip
- Berkeley Lower Extremity Exoskeleton (BLEEX)
- University of Washington Exo Arm Project
- Cyberdyne's HAL power suit
Dapyx Software network: MP3 Explorer | Ebook Manager | Zenithic