The Skeletal System

The Skeletal System

Your skeleton is made up of bones which give your body structure, allow you to move, protect your organs, and more. Did you know that the human body has 206 bones?

THE HUMAN BODY:

LEGS

RIBS

HANDS

JOINTS

SKULL

SPINE

HOW BONES GROW

ABOUT BONES

“Your Bones (for Kids) - Nemours KidsHealth.” Edited by KidsHealth Medical Experts, KidsHealth, Nemours Children's Health System, kidshealth.org/en/kids/bones.html.

Your ribs are there to protect your lungs, heart, and liver. The left and right sides of your ribs are exactly the same; most people have 12 ribs, but some people are born with extra ribs and some people have one pair less. The ribs all attach to the spine, and are held in place by the thoracic vertebrae. The first seven ribs also attach in the front to the sternum, a bone in the center of your chest that helps hold the ribs in place.

Your arms are attached to your scapula, or shoulder blades, which are large triangular bones on your upper back. The arm itself is made of three bones, the humerus, the radius, and the ulna. The humerus is above the elbow, while the radius and ulna are below. At the end of the radius and ulna are eight small bones which form your wrist. These bones allow for wrist movement. The center part of your hand, the palm, is made of five separate bones, and then each finger has three bones - except for the thumb, which only has two.

Joints are where two bones meet. Many of our joints move, but some don’t. For example, there are some fixed joints (joints which don’t move) in the skull. However, lots of other joints move! Hinge joints, such as the elbows and knees, are an important kind of moving joint. The elbows and knees let you bend and straighten your arms and legs, but they can only move in one direction. Another kind of moving joint are ball and socket joints, such as your shoulders and hips. These joints are made of a round end of a bone fitting into a cup-like area of another bone. These joints allow for movement in any direction.

Your skull protects the most important part - your brain. The skill is made of various bones, some of which serve to protect the brain while others make up the structure of your face. When we are born, we have a space between the bones in our skull. This helps the bones move to fit through the birth canal as the baby is being born. However, as babies get older, the space between the bones closes.

The spine is made of 33 ring-shaped bones called vertebrae. The purpose of the spine is to protect the spinal cord, a bundle of nerves which sends information from the brain to the rest of the body. Your spine also allows you to hold your body upright. There are five kinds of vertebrae in the spine: cervical, thoracic, lumbar, sacrum, and coccyx. The first seven vertebrae (at the back of your neck) are the cervical vertebrae, and they support the head and neck. Below the cervical vertebrae are 12 thoracic vertebrae, and these serve to hold your ribs in place. Next you have five lumbar vertebrae , and the scrum, which is made of five vertebrae fused together to make a single bone. Finally, you have the coccyx, a bone made of four vertebrae fused together. This bottom part of your spine helps you carry weight and balance. In between the vertebrae, there are disks made of cartilage which keep the vertebrae from rubbing against each other.

Your legs are attached to the pelvis, a circular group of bones which supports the spine. It is made of two large hip bones, and the sacrum and coccyx. The pelvis protects the digestive system, the urinary system, and the reproductive system. The bone that connects your pelvis to your knee is the femur, and it’s the longest bone. In your knee, there’s a triangular shaped bone called the patella. Below the knee are the tibia and the fibula. The bones in your legs are large and strong to support your weight. At the ankle, the lower leg bones connect to the talus, a large bone in the foot. There are six other bones near the talus, and then the main part of the foot is similar to the hand - it has five bones. Each toe has three bones, too, except for the big toe which only has two.

Your ribs are there to protect your lungs, heart, and liver. The left and right sides of your ribs are exactly the same; most people have 12 ribs, but some people are born with extra ribs and some people have one pair less. The ribs all attach to the spine, and are held in place by the thoracic vertebrae. The first seven ribs also attach in the front to the sternum, a bone in the center of your chest that helps hold the ribs in place.

The spine is made of 33 ring-shaped bones called vertebrae. The purpose of the spine is to protect the spinal cord, a bundle of nerves which sends information from the brain to the rest of the body. Your spine also allows you to hold your body upright. There are five kinds of vertebrae in the spine: cervical, thoracic, lumbar, sacrum, and coccyx. The first seven vertebrae (at the back of your neck) are the cervical vertebrae, and they support the head and neck. Below the cervical vertebrae are 12 thoracic vertebrae, and these serve to hold your ribs in place. Next you have five lumbar vertebrae , and the scrum, which is made of five vertebrae fused together to make a single bone. Finally, you have the coccyx, a bone made of four vertebrae fused together. This bottom part of your spine helps you carry weight and balance. In between the vertebrae, there are disks made of cartilage which keep the vertebrae from rubbing against each other.

Your skull protect the most important part - your brain. The skill is made of various bones, some of which serve to protect the brain while others make up the structure of your face. When we are born, we have a space between the bones in our skull. This helps the bones move to fit through the birth canal as the baby is being born. However, as babies get older, the space between the bones closes.

Your arms are attached to your scapula, or shoulder blades, which are large triangular bones on your upper back. The arm itself is made of three bones, the humerus, the radius, and the ulna. The humerus is above the elbow, while the radius and ulna are below. At the end of the radius and ulna are eight small bones which form your wrist. These bones allow for wrist movement. The center part of your hand, the palm, is made of five separate bones, and then each finger has three bones - except for the thumb, which only has two.

Joints are where two bones meet. Many of our joints move, but some don’t. For example, there are some fixed joints (joints which don’t move) in the skull. However, lots of other joints move! Hinge joints, such as the elbows and knees, are an important kind of moving joint. The elbows and knees let you bend and straighten your arms and legs, but they can only move in one direction. Another kind of moving joint are ball and socket joints, such as your shoulders and hips. These joints are made of a round end of a bone fitting into a cup-like area of another bone. These joints allow for movement in any direction.

Your legs are attached to the pelvis, a circular group of bones which supports the spine. It is made of two large hip bones, and the sacrum and coccyx. The pelvis protects the digestive system, the urinary system, and the reproductive system. The bone that connects your pelvis to your knee is the femur, and it’s the longest bone. In your knee, there’s a triangular shaped bone called the patella. Below the knee are the tibia and the fibula. The bones in your legs are large and strong to support your weight. At the ankle, the lower leg bones connect to the talus, a large bone in the foot. There are six other bones near the talus, and then main part of the foot is similar to the hand - it has five bones. Each toe has three bones, too, except for the big toe which only has two.

A baby is born with over 300 bones. These bones fuse together to form just 206 bones. Some of a baby’s bones are made entirely or partly of cartilage, a soft, flexible connective tissue. As children grow up, the cartilage will slowly be replaced by bone. This process will be complete by the time you are around 25 years old.

Unlike bones in fossils or museums, the bones in your body are alive and they can grow and change like the rest of your body! Bones are made of several materials. The outer surface of your bones is called the periosteum, and it is a thin membrane which contains blood vessels and nerves that nourish the bone. The next layer is what you see when you look at a skeleton, and it is called compact bone. It is very smooth and hard. In the compact bone there are layers of cancellous bone, which is not as hard or as compact as bone but still quite strong. In most bones, the purpose of the cancellous bone is to protect the inner part of the bone, the bone marrow. Bone marrow is soft tissue which makes blood stem cells (cells that turn into blood cells).