Human Skeletal system
17. Human Body - Skeletal system
Skeletal system
In biology, the skeleton or skeletal system is the biological system providing support in living organisms. Skeletal systems are commonly divided into three types
1. external (an exoskeleton)
2. internal (an endoskeleton)
3. fluid based (a hydrostatic skeleton)
3. fluid based (a hydrostatic skeleton)
The phyla arthropoda and mollusca both have exoskeletons. An internal skeletal system consists of rigid structures within the body, moved by the muscular system. Hydrostatic skeletons are similar to a water-filled balloon. Located internally in cnidarians and annelids, among others, these animals can move by contracting the muscles surrounding the fluid-filled pouch, creating pressure within the pouch that causes movement. Cartilage is another common component of skeletal systems, supporting and supplementing the skeleton. The human ear and nose are shaped by cartilage. Some organisms have a skeleton consisting entirely
of cartilage and without any calcified bones at all, for examplesharks. The bones or other rigid structures are connected by ligaments and connected to the muscular system via tendons.
The human skeleton consists of 206 bones. We are actually born with more bones (about 300), but many fuse together as a child grows up. These bones support your body and allow you to move. Bones contain a lot ofcalcium (an element found in milk, broccoli, and other foods). Bones manufacture blood cells and store important minerals.
The longest bone in our bodies is the femur (thigh bone). The smallest bone is the stirrup bone inside the ear. Each hand has 26 bones in it. Your nose and ears are not made of bone; they are made of cartilage, a flexible substance that is not as hard as bone.
Joints
Bones are connected to other bones at joints.T here are many different types of joints, including
fixed joints (such as in the skull, which consists of many bones)
hinged joints (such as in the fingers and toes)
ball-and-socket joints (such as the shoulders and hips)
A typical bone has an outer layer of hard or compact bone, which is very strong, dense and tough. Inside this is a layer of spongy bone, which is like honeycomb, lighter and slightly flexible. In the middle of some bones is jelly-like bone marrow, where new cells are constantly being produced for the blood.
Differences in males and females
Males and females have slightly different skeletons, including a different elbow angle. Males have slightly thicker and longer legs and arms; females have a wider pelvis and a larger space within the pelvis, through which babies travel when they are born.
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