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May 16, 2024 · Learn about the structure and function of the human skeleton, the internal framework of the body. The skeleton consists of two main parts: the axial and the appendicular, and serves as a support, protection, and motion system.
- Overview
- Comparative study of skeletal systems
- Principal types of skeletal elements
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skeleton, the supportive framework of an animal body. The skeleton of invertebrates, which may be either external or internal, is composed of a variety of hard nonbony substances. The more complex skeletal system of vertebrates is internal and is composed of several different types of tissues that are known collectively as connective tissues. This ...
In addition to its supportive function, the animal skeleton may provide protection, facilitate movement, and aid in certain sensory functions. Support of the body is achieved in many protozoans by a simple stiff, translucent, nonliving envelope called a pellicle. In nonmoving (sessile) coelenterates, such as coral, whose colonies attain great size, it is achieved by dead structures, both internal and external, which form supporting axes. In the many groups of animals that can move, it is achieved either by external structures known as exoskeletons or by internal structures known as endoskeletons. Many animals remain erect or in their normal resting positions by means of a hydrostatic skeleton—i.e., fluid pressure in a confined space.
The skeleton’s protective function alone may be provided by structures situated on the body surface—e.g., the lateral sclerites of centipedes and the shell (carapace) of crabs. These structures carry no muscle and form part of a protective surface armour. The scales of fish, the projecting spines of echinoderms (e.g., sea urchins), the minute needlelike structures (spicules) of sponges, and the tubes of hydroids, all raised from the body surface, are similary protective. The bones of the vertebrate skull protect the brain. In the more advanced vertebrates and invertebrates, many skeletal structures provide a rigid base for the insertion of muscles as well as providing protection.
The skeleton facilitates movement in a variety of ways, depending on the nature of the animal. The bones of vertebrates and the exoskeletal and endoskeletal units of the cuticle of arthropods (e.g., insects, spiders, crabs) support opposing sets of muscles (i.e., extensors and flexors). In other animal groups the hydrostatic skeleton provides such support.
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In a limited number of animals, the hard skeleton transmits vibrations that are sensed by the hearing mechanism. In some forms—e.g., bony fishes and fast-swimming squids—it aids in the formation of buoyancy mechanisms that enable the animal to adjust its specific gravity for traveling at different depths in the sea.
Certain types of skeletons usually characterize particular animal phyla, but there are a limited number of ways in which an animal can form its skeleton. Similar modes of skeleton formation have evolved independently in different groups to fulfill similar needs. The cartilaginous braincase of the octopus and the squid, which are invertebrates, has a microscopic structure similar to the cartilage of vertebrates. The calcareous (i.e., calcium-containing) internal skeleton of the echinoderms is simply constructed but is essentially not far different from the much more elaborate bones of vertebrates. Skeletal fibres of similar chemical composition occur in unrelated animal groups; for example, coiled shells of roughly similar chemical composition are present in gastropods (e.g., snails), brachiopods (e.g., lamp shells), and cephalopods (e.g., chambered nautilus). The mechanical properties of different skeletal types vary considerably according to the needs of animals of particular size ranges or habits (e.g., aquatic, terrestrial).
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Skeletal elements are of six principal types: hard structures, semirigid structures, connective tissue, hydrostatic structures, elastic structures, and buoyancy devices.
Learn about the skeleton, the supportive framework of an animal body, composed of various types of tissues and structures. Compare the skeletons of invertebrates and vertebrates, and explore their functions and adaptations.
- The Skeletal System Consists Of More Than Bones. When you look at the human skeleton the 206 bones and 32 teeth stand out. But look closer and you’ll see even more structures.
- The Adult Human Skeleton Is Made Up of 206 Bones. These bones provide structure and protection and facilitate motion. Bones articulate to form structures.
- The Skeleton Protects Vital Organs. The brain is surrounded by bones that form part of the skull. The heart and lungs are located within the thoracic cavity, and the vertebral column provides structure and protection for the spinal cord.
- Interactions Between the Skeleton, Muscles, and Nerves Move the Body. How does the skeleton move? Muscles throughout the human body are attached to bones.
Aug 30, 2018 · Learn about the skeletal system, which consists of bones, cartilage, tendons, and ligaments. Find out how it supports, protects, moves, and produces blood cells in the body.
Skeletons can be defined by several attributes. Solid skeletons consist of hard substances, such as bone, cartilage, or cuticle. These can be further divided by location; internal skeletons are endoskeletons, and external skeletons are exoskeletons.
Discuss the different types of skeletal systems. Explain the role of the human skeletal system. Compare and contrast different skeletal systems. A skeletal system is necessary to support the body, protect internal organs, and allow for the movement of an organism.
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Learn about the differences between exoskeletons and endoskeletons, and the functions and types of human bones. Watch a video and read comments from other learners on skeletal anatomy.
- 7 min
- Tracy Kim Kovach
