What makes up the skeleton

If you breathe in deeply, you can easily feel your ribs right in the front of your body, too. Some thin kids can even see a few of their ribs right through their skin. Your ribs come in pairs, and the left and right sides of each pair are exactly the same. Most people have 12 pairs of ribs, but some people are born with one or more extra ribs, and some people might have one pair less.

All 12 pairs of ribs attach in the back to the spine, where they are held in place by the thoracic vertebrae. The first seven pairs of ribs attach in the front to the sternum say: STUR-num , a strong bone in the center of your chest that holds those ribs in place. The remaining sets of ribs don't attach to the sternum directly. The next three pairs are held on with cartilage to the ribs above them. The very last two sets of ribs are called floating ribs because they aren't connected to the sternum or the ribs above them.

But don't worry, these ribs can't ever float away. Like the rest of the ribs, they are securely attached to the spine in the back. Your skull protects the most important part of all, the brain.

You can feel your skull by pushing on your head, especially in the back a few inches above your neck. The skull is actually made up of different bones. Some of these bones protect your brain, whereas others make up the structure of your face. If you touch beneath your eyes, you can feel the ridge of the bone that forms the hole where your eye sits.

And although you can't see it, the smallest bone in your whole body is in your head, too. The stirrup bone behind your eardrum is only. Want to know something else? Your lower jawbone is the only bone in your head you can move. It opens and closes to let you talk and chew food. Your skull is pretty cool, but it's changed since you were a baby. All babies are born with spaces between the bones in their skulls. This allows the bones to move, close up, and even overlap as the baby goes through the birth canal.

As the baby grows, the space between the bones slowly closes up and disappears, and special joints called sutures say: SOO-churs connect the bones.

As you sit and type at the keyboard, while you swing on a swing, even when you pick up your lunch, you're using the bones in your fingers, hand, wrist, and arm. Each arm is attached to a shoulder blade or scapula say: SKA-pyuh-luh , a large triangular bone on the upper back corner of each side of the ribcage. The arm is made up of three bones: the humerus say: HYOO-muh-rus , which is above your elbow, and the radius say: RAY-dee-us and ulna say: UL-nuh , which are below the elbow.

Each of these bones is wider at the ends and skinnier in the middle, to help give it strength where it meets another bone. At the end of the radius and ulna are eight smaller bones that make up your wrist. Although these bones are small, they can really move! Twist your wrist around or wave and you'll see how the wrist can move. The center part of your hand is made up of five separate bones.

Each finger on your hand has three bones, except for your thumb, which has two. So between your wrists, hands, and all your fingers, you've got a grand total of 54 bones — all ready to help you grasp things, write your name, pick up the phone, or throw a softball! Sure, your arm, wrist, hand, and finger bones are great for picking up the phone, but how are you supposed to run to answer it?

Well, with the bones of the legs and feet! Your legs are attached to a circular group of bones called your pelvis. The pelvis is a bowl-shaped structure that supports the spine.

It is made up of the two large hip bones in front, and behind are the sacrum and the coccyx. The pelvis acts as a tough ring of protection around parts of the digestive system, parts of the urinary system, and parts of the reproductive system. Your leg bones are very large and strong to help support the weight of your body.

The bone that goes from your pelvis to your knee is called the femur say: FEE-mur , and it's the longest bone in your body. At the knee, there's a triangular-shaped bone called the patella say: puh-TEL-luh , or kneecap, that protects the knee joint. Just like the three bones in the arm, the three bones in the leg are wider at the ends than in the middle to give them strength.

The ankle is a bit different from the wrist; it is where the lower leg bones connect to a large bone in the foot called the talus say: TAL-iss. Next to the talus are six other bones.

But the main part of the foot is similar to the hand, with five bones. Each toe has three tiny bones, except for your big toe, which has just two. The long bones of the body contain many distinct regions due to the way in which they develop. At birth, each long bone is made of three individual bones separated by hyaline cartilage. The epiphyses and diaphysis grow towards one another and eventually fuse into one bone.

Once the long bone parts have fused together, the only hyaline cartilage left in the bone is found as articular cartilage on the ends of the bone that form joints with other bones. The articular cartilage acts as a shock absorber and gliding surface between the bones to facilitate movement at the joint. Looking at a bone in cross section, there are several distinct layered regions that make up a bone.

The outside of a bone is covered in a thin layer of dense irregular connective tissue called the periosteum. The periosteum contains many strong collagen fibers that are used to firmly anchor tendons and muscles to the bone for movement.

Stem cells and osteoblast cells in the periosteum are involved in the growth and repair of the outside of the bone due to stress and injury. Blood vessels present in the periosteum provide energy to the cells on the surface of the bone and penetrate into the bone itself to nourish the cells inside of the bone. The periosteum also contains nervous tissue and many nerve endings to give bone its sensitivity to pain when injured.

Deep to the periosteum is the compact bone that makes up the hard, mineralized portion of the bone. Compact bone is made of a matrix of hard mineral salts reinforced with tough collagen fibers. Many tiny cells called osteocytes live in small spaces in the matrix and help to maintain the strength and integrity of the compact bone.

Deep to the compact bone layer is a region of spongy bone where the bone tissue grows in thin columns called trabeculae with spaces for red bone marrow in between. The trabeculae grow in a specific pattern to resist outside stresses with the least amount of mass possible, keeping bones light but strong. Long bones have a spongy bone on their ends but have a hollow medullary cavity in the middle of the diaphysis.

The medullary cavity contains red bone marrow during childhood, eventually turning into yellow bone marrow after puberty. An articulation, or joint, is a point of contact between bones, between a bone and cartilage, or between a bone and a tooth. Synovial joints are the most common type of articulation and feature a small gap between the bones. This gap allows a free range of motion and space for synovial fluid to lubricate the joint. Fibrous joints exist where bones are very tightly joined and offer little to no movement between the bones.

Fibrous joints also hold teeth in their bony sockets. Finally, cartilaginous joints are formed where bone meets cartilage or where there is a layer of cartilage between two bones.

These joints provide a small amount of flexibility in the joint due to the gel-like consistency of cartilage. The bones of the axial skeleton act as a hard shell to protect the internal organs—such as the brain and the heart —from damage caused by external forces. The bones of the appendicular skeleton provide support and flexibility at the joints and anchor the muscles that move the limbs. The bones of the skeletal system act as attachment points for the skeletal muscles of the body.

Almost every skeletal muscle works by pulling two or more bones either closer together or further apart.

Joints act as pivot points for the movement of the bones. The regions of each bone where muscles attach to the bone grow larger and stronger to support the additional force of the muscle. In addition, the overall mass and thickness of a bone increase when it is under a lot of stress from lifting weights or supporting body weight. Red bone marrow produces red and white blood cells in a process known as hematopoiesis.

Red bone marrow is found in the hollow space inside of bones known as the medullary cavity. The amount of red bone marrow drops off at the end of puberty, replaced by yellow bone marrow. The skeletal system stores many different types of essential substances to facilitate growth and repair of the body. Proper levels of calcium ions in the blood are essential to the proper function of the nervous and muscular systems. There are 14 facial bones. Auditory ossicles The auditory ossicles are six small bones found within the inner ear canal in the skull.

There are three auditory ossicles on each side of the head, known as the: malleus hammer incus anvil stapes stirrup They work together to transmit sound waves from the surrounding environment to the structures of the inner ear. Hyoid The hyoid is a U-shaped bone found at the base of the jaw. Vertebral column The vertebral column is made up 26 bones. The 24 vertebrae can be further divided into the: Cervical vertebrae.

These seven bones are found in the head and neck. Thoracic vertebrae. These 12 bones are found in the upper back. Lumbar vertebrae. These five bones are found in the lower back. Thoracic cage The thoracic cage is made up of the sternum breastbone and 12 pairs of ribs. Skeletal system diagram. Explore the interactive 3-D diagram below to learn more about the skeletal system. Appendicular skeleton anatomy. Pectoral girdle The pectoral girdle is where the arms attach to the axial skeleton.

Upper limbs Each arm contains 30 bones, known as the: Humerus. The humerus is the long bone of the upper arm. The radius is one of two long bones of the forearm, found on the thumb side. The ulna is the second long bone of the forearm, found on the pinky finger side. The carpals are a group of eight bones found in the wrist area.

The metacarpals are five bones found in the middle area of the hand. The phalanges are 14 bones that make up the fingers. Pelvic girdle The pelvic girdle, commonly known as the hips, is where the legs attach to the axial skeleton. Each hip bone consists of three parts, known as the: Ilium. The ilium is the top portion of each hip bone. The ischium is a curved bone that makes up the base of each hip bone.

The pubis is located in the front part of the hip bone. Lower limbs Each leg is composed of 30 bones, known as the: Femur. The femur is the large bone of the upper leg.

The tibia is the main bone of the lower leg. It forms the shin. The fibula is the second bone in the lower leg, found in the outer leg. The patella is also called the kneecap.

The tarsals are the seven bones that make up the ankle. The metatarsals are the five bones that make up the middle area of the foot. The phalanges are 14 bones that comprise the toes. What is the function of the skeletal system? But the skeletal system has several additional functions, including: Protecting internal organs from injury. For example, the skull protects the brain, while the thoracic cage protects the heart and lungs. Allowing for movement.

Muscles attach to bones through tendons. This connection allows the body to move in many different ways. Producing blood cells. The soft bone marrow inside of many bones produces red blood cells, white blood cells, and platelets.