Skeleton Joints
Individual bones meet at areas called joints and are held in place by connective . Most joints, such as the elbow, are called synovial joints, for the synovial which envelopes the joint and secretes a lubricating fluid. Cartilage lines the surface of many joints and helps reduce between bones. The connective tissues linking the skeleton together at the joints are tendons and ligaments. Ligaments and tendons are both made up of collagen, but serve different functions. Ligaments link bones together and help prevent dislocated joints. Tendons link bone to muscle.
Type of joints
Where bones meet
Joints are the place where two bones meet. All of your bones, except for one (the hyoid bone in your neck), form a joint with another bone. Joints hold your bones together and allow your rigid skeleton to move.
- Some of your joints, like those in your skull, are fixed and don't allow any movement. The bones in your skull are held together with fibrous connective tissue.
- Other joints, such as those between the vertebrae in your spine, which are connected to each other by pads of cartilage, can only move a small amount.
- Most of your joints are 'synovial joints'. They are movable joints containing a lubricating liquid called synovial fluid. Synovial joints are predominant in your limbs where mobility is important. Ligaments help provide their stability and muscles contract to produce movement. The most common synovial joints are listed below:
- Ball and socket joints, like your hip and shoulder joints, are the most mobile type of joint in the human body. They allow you to swing your arms and legs in many different directions.
- Ellipsoidal joints, such as the joint at the base of your index finger, allow bending and extending, rocking from side to side, but rotation is limited.
- Gliding joints occur between the surfaces of two flat bones that are held together by ligaments. Some of the bones in your wrists and ankles move by gliding against each other.
- Hinge joints, like in your knee and elbow, enable movement similar to the opening and closing of a hinged door.
- The pivot joint in your neck allows you to turn your head from side to side.
- The only saddle joints in your body are in your thumbs. The bones in a saddle joint can rock back and forth and from side to side, but they have limited rotation.
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Flexibility: Joints enable your body to move
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Ball and socket joints: Are the most mobile type of joint in your body
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Saddle joints: Enable you to grasp things
Babies have more cartilage than bone
The skeleton of a newborn baby is made up of more than 300 parts, most of which are made of cartilage. Over time, most of this cartilage turns into bone, in a process called ossification. As the baby grows, some of its bones fuse together to form bigger bones. By adulthood, your skeleton contains just 206 bones.
How bones grow in length
A long bone, such as your femur (thigh bone), grows in length at either end in regions called growth plates. Growth occurs when cartilage cells divide and increase in number in these growth plates. These new cartilage cells push older, larger cartilage cells towards the middle of a bone. Eventually, these older cartilage cells die and the space they occupied is replaced with bone. When a bone has reached its full size, its growth plates are converted into bone.
Long bone growth comes to an end around the end of puberty. When long bone growth stops, you stop getting taller.
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Fusing bones: Babies' skeletons have 300 parts, adults' have 206
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Long bone growth: Stops around the end of puberty
Bone shapes
- Long bones, like in your arms and legs, are mostly made of compact bone
- Short bones, like the bones in your wrists and ankles, are mainly made of spongy bone
- Flat bones, like your rib and skull bones, are made of a layer of spongy bone sandwiched between two thin layers of compact bone
- Irregular bones, such as your butterfly-shaped vertebrae, are unusual shaped bones that don't fit into the other three groups
Cross section view of a long bone
Compact bone
Explain how compact bone works?
Find out the Bone cells and the process of it?
Skeleton spine
Vertebrae
Your spine is made up of 33 irregularly shaped bones called vertebrae. Each vertebra has a hole in the middle through which the spinal cord runs. The spinal cord can be divided into five different regions, from top to bottom:
- Your 7 cervical vertebrae support your head and neck and allow you to nod and shake your head
- Your ribs attach to your 12 thoracic vertebrae
- Your five sturdy lumbar vertebrae carry most of the weight of your upper body and provide a stable centre of gravity when you move
- Your sacrum is made up of five fused vertebrae. It makes up the back wall of your pelvis
- Your coccyx is made up of four fused vertebrae. It is an evolutionary remnant of the tail found in most other vertebrates
S-shaped spine: Prevents shock to your head when you walk or run
Spinal cord protection: Your bony spine encases your delicate spinal cord
Vertebrae: 33 vertebrae make up your spine
Ossification:
The Rib Cage
The Right Rib Cage
There are 12 ribs on each side of the body. Ribs are flat bones. They are numbered one through twelve from top to bottom. Each rib connects to a thorasic vertebra. The top seven are true ribs, which connect directly to coastal cartlilage and the sternum. The remaining 5 ribs are false ribs. Three of them connect to costal cartslige shared with the 7th true rib. The last 2 ribs are floating ribs, which do not have connectinos on their anterior ends.
The joints between ribs are cartilaginous joints.
The xiphoid process (not labeled) is the teardrop-shaped bone located just below the sternum. When administering CPR (cardio-pulminary recesitation) it is very important to find this process so as to avoid breaking it off while performing chest compressinons.