Any animal that lives outside of water needs a skeleton to support it.

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1 LIFE AND LIVING SKELETONS The skeleton is the part of the body that forms the supporting structure in animals and humans. Without a skeleton, we would not be able to stand upright or walk. Animal Skeletons Any animal that lives outside of water needs a skeleton to support it. Animals that have backbones are called vertebrates. These all have skeletons, ie fish, mammals, reptiles, birds and amphibians are all vertebrates. Vertebrates- - Birds Vertebrates - Mammals Dogs and Cats Vertebrates- - Fish Vertebrates- - Amphibians Vertebrates- - Reptiles Animals that do not have a backbone are called invertebrates. Snails, insects and worms are examples of invertebrates. Invertebrates - Snails Invertebrates - Worms Version 5: November

2 There are 3 main types of skeletons found in animals: Exoskeleton This is a stable outer shell of an animal. Many invertebrates have exoskeletons. The exoskeleton encloses and protects the soft tissues and organs of the animal. The exoskeleton also serves as a surface for the attachment of muscles. The exoskeleton can be a simple hard shell or two or more hard pieces joined together by flexible tissue. Insects, spiders and scorpions, cockroaches and crustaceans, such as lobsters and crabs all have exoskeletons. Exoskeleton - Scorpion Exoskeleton - Crab The exoskeleton has several layers. The inner layer or epidermis is a membrane made of fibres. Above this layer is the procuticle, which is made of chitin and covered in a layer of protein which forms a rigid plate. On the outside, is the epicuticle, which prevents the soft tissues from drying out. This is a very strong layer which can resist compression and therefore provides protection. The exoskeleton moults as the animal grows. An arthropod is an invertebrate animal with a segmented body, an exoskeleton and jointed limbs. The arthropod has flexible joints to allow for a range of movement. Version 5: November

3 Hydroskeleton Some organisms like starfish, for example, do not have bones or plates. They have cavities filled with fluid under pressure, known as a hydroskeleton. The pressure of the fluid, as well as the action of muscles, helps the organism to change shape and move. Hydroskeleton - Starfish Hydroskeletons are mainly found in cold blooded organisms and soft bodied animals such as jellyfish, sea urchins and earthworms. Hydroskeletons - Jellyfish Hydroskeletons - Sea Urchin Endoskeleton An endoskeleton forms the support structure inside of the body. It serves a number of functions apart from support, such as attachment of muscles and it also enables movement. Humans, mammals, reptiles, birds, fish and amphibians all have endoskeletons. Human Endoskeleton Endoskeleton - Amphibians - Frog Version 5: November

4 In humans and most vertebrates, the main skeletal structure is made of bone, as well as cartilage in the joint areas of mammals. In sharks, for example, the skeleton is made entirely of cartilage which is lighter than bone and enables the shark to swim efficiently. There are a number of similarities and differences between the skeletons of the various groups of vertebrates, as described below: Mammals Endoskeleton Shark Skeleton Made of Cartilage Mammal skeletons are the most complex of all animals, because they enable a range of movements. Mammals all have backbones made of vertebrae and limbs with different types of joints. Each of the bones of the limbs are arranged in the same basic pattern and jointed to the spine with a bone called a girdle. A Girdle Most mammals have the following bones in their skeletons; A skull protects the brain A rib cage protects the heart and lungs A backbone from skull to the tail A tail the tail is made up of many vertebrae which is used to help the mammal balance Version 5: November

5 The skeletons of many mammals have adapted to their habitat. For example, a giraffe has a long neck to reach the leaves at the top of trees. A Dolphin Has Flippers A Giraffe Has a Long Neck A dolphin has flippers instead of front legs. Version 5: November

6 Birds A bird s skeleton is very lightweight and strong and well adapted for flying. Birds have less bones than other animals as some are fused together to make the skeleton more rigid. Many of the bones are hollow, except for birds that don t fly, like the penguin. Some of the bones are also supported by internal struts. A Penguin Does Not Fly Birds do not have teeth or a jaw, but a lightweight beak. They also have more neck (cervical) vertebrae than most animals, so that they can turn around and groom their feathers. Birds Have Beaks The forearms of birds have been modified into wings. The muscles which enable birds to fly are attached to the sternum (breastbone). Wings Are Used For Flying Version 5: November

7 Fish In fish, the skeleton is made of cartilage or bones. Most of the fins are not connected to the spine, but supported by muscles. The ribs are attached to the spine. There are 3 types of fish, based on their type of skeleton: Bony fish the skeleton is made of bones and they have pairs of fins and teeth. Most fish are bony fish. Bony Fish - Koi Version 5: November

8 Jawless fish these have a skeleton made of cartilage, no jaw and no pairs of fins, for example, the hagfish or lamprey. Jawless Fish - Lamprey Cartilaginous fish these also have a skeleton made of cartilage, but do have pairs of fins. For example, sharks and rays. Reptiles Cartilaginous Fish - Stingray Reptiles with limbs hold them to the side of their bodies. They also have a breastbone and feet with claws. Most lizards have 4 limbs with 5 toes on each one. Some reptiles only have traces of limbs. Reptiles A Lizard Snakes have up to 500 vertebrae in their flexible spine. They have a skull, vertebra and ribs, as well as the remnants of limbs in their skeletons. Their skull is a complex structure that allows them to swallow prey that is much larger than their head. Remnants of a pelvis can be found in some snakes. Reptiles - A Snake Version 5: November

9 A tortoise has a vertebrae and ribs which have been fused and modified to form its shell. Reptile - A Tortoise Version 5: November

10 Amphibians Frogs have well developed back legs and foot bones, a short strong spine and adapted hip bones to help them jump and land easily. Amphibians - Frogs The limbs are attached to the shoulders and hips. The front legs are smaller and weaker and have the same bones as humans, ie the humerus, radius and ulna, although the radius and ulna are fused together. The rear legs have femurs which supports the upper and lower leg bones of the fibula and tibia, which are also fused together. The frog has 5 toes on its back legs and 4 toes on its front legs. Frogs have two shoulder blades (scapulae) and clavicles (collar bones) which are shaped a lot like the same bones in humans. The pelvis can slide up and down its spine, so this helps the frog to leap. The vertebrae at the base of the spine are fused together and there are no ribs. Although the frog has a skull, it has no neck, so cannot turn its head. Version 5: November

11 Human Skeleton The human skeleton is a framework of bones, cartilage and ligaments. The human skeleton has a number of important functions: It supports the body It protects internal organs such as the brain It allows the body to move Bones store minerals such as calcium Blood cells are made in the bones Bones allow us to grip and grasp Version 5: November

12 Bones make up around 20% of the total body weight in humans. They are very strong, in fact, they are stronger than concrete or steel. However, they can still break, but will heal themselves in time. Cartilage joins the end of bones in joints. It also forms ears and the nose. A joint is found wherever bones meet and allow us to move and be flexible. They connect the bones together. There are more than 150 joints in the body. Joints can either be hinge type joints which allow the lower leg, for example to move forwards and backwards, but not sideways. These joints are found in your fingers and elbows as well. Version 5: November

13 Ball and socket joints allows for sideways movement and are found in the hip and shoulder. Ligaments also hold the bones together and to move and stop them from coming apart. Version 5: November

14 A human skeleton has 206 bones, made up as follows: Axial skeleton the backbone, ribs and skull. These are all located in the centre of the body. A total of 80 bones. Appendicular skeleton this consists of the arm and leg bones, shoulder and hips. A total of 126 bones. Half of the bones of the human body are in your hands and feet. Bones are hard on the inside, have a soft spongy middle layer and have soft bone marrow in the middle, where the red and white blood cells are made. Bones are made up of collagen and minerals such as calcium and phosphate. There are also blood vessels and nerves in bones. The nerves help us to feel pressure and pain. Version 5: November

15 The Skull Human Skull X-ray of the Human Skull The skull is made up of 22 bones. It is a very strong structure which protects the brain. There are 14 bones which provide the framework of the face and hold the muscles that produce facial expressions. The mandible or lower jaw is the only moveable bone in the skull. There are deep eye sockets in the skull for the eyeballs. Backbone The backbone is the main axis for the body and supports the head and trunk. It has 24 vertebrae with a further 9 fused bones at its base, forming the sacrum and coccyx. Between each vertebra is a disc made of cartilage. The vertebrae are hollow bones which protect the spinal cord. The spinal cord sends messages to and from the brain. Human Vertebrae (Backbone) Version 5: November

16 The vertebrae are flexible, strong and can also absorb shock, as well as balance the body. They also provide anchorage for muscles. Human Vertebrae (Backbone) Ribs The ribs surround and protect the heart and lungs. There are 25 bones in the chest of which 24 are ribs, as well as the breastbone or sternum. Version 5: November

17 Shoulder Blades The shoulder blade or scapula forms a joint with the upper arm/humerus and is attached to the clavicle or collar bone. Arm bones The humerus is the upper arm bone and there are two lower arm bones the radius and the ulna, which is the inner arm bone. The metacarpals are the bones in the palm of the hand and the phalanges are the finger bones. X-ray of the Human Arm X-ray of the Human Hand Version 5: November

18 Leg Bones There are 31 bones in each leg, with 7 in each ankle. The femur or thigh bone is the longest bone in the body. The fibula is the lower leg bone and is found behind the tibia or shin bone, which takes most of the weight of the lower leg. The patella or knee cap protects the knee. The ankle bones are called tarsals and the metatarsals are the 5 long bones between the knees and the toes. The toe bones are called phalanges. The heel bone is known as the calcareous. Version 5: November

19 X- Ray of Human Leg & Foot Bones Hips The hip bones or pelvis supports and protects the abdominal organs. Version 5: November