Human Skeletal System

What is the skeleton?

The internal framework of our body is the skeleton. It is made up of bones. Bones help muscles to act as levers to move the legs, arms and other body parts. We could no longer move our body without bones. In fact, you will look like a huge blob of jelly, without the skeleton.

Have you ever thought that you would look like a huge blob of jelly without your skeleton?

What does the skeleton do?

Following is a list of things that the skeleton does;

1. The skeleton provides shape and support to the body.

2. It protects the internal organs such as the brain, the heart,  and the lungs and keep them in their proper place.

3. It helps us to move as our muscles are attached to our bones.

4. Bones in the skeleton help producing blood cells.

How many bones are there in the human skeletal system?

Our human skeletal system is made up of about 300 bones at birth. As the body matures, some of these bones gradually, fuse together to form one bone. Therefore, by adulthood the human skeleton only consists of 206 bones.

 

Human Skeletal System

Human Skeletal System

The two main divisions of the human skeletal system

The human skeletal system is divided into two main divisions. They are;

1. The Axial Skeleton

2. The Appendicular Skeleton

The Axial Skeleton

The axial skeleton consists of the skull bones, sternum, spine (vertebral column) and the rib cage. The axial skeleton contains 80 bones all together.

Bones in the axial skeleton

The Skull

The skull is a bony structure that supports the structures of the face and provides a protective cavity for the brain. It consists of the following parts;

1. The cranium

2. The facial bones

3. The mandible or the jaw bone

Parts of the skull

The Sternum

The sternum is also called the breastbone. It is a long flat bone, which is located in the centre of the chest and connects to the ribs with cartilage . The sternum consists of three main parts;

1. The manubrium

2. Sternal body

3. The xiphoid process

Parts of the sternum

The Rib Cage

The rib cage is formed by the spine (vertebral column), sternum, ribs and cartilages. It encloses the heart and lungs. There are three types of ribs in the rib cage. They are;

1. True ribs

2. False ribs

3. Floating ribs

Parts of the rib cage

The Spine

The spine is also known as the vertebral column or backbone. The human vertebral column consists of 33 vertebrae.  A vertebra (plural – vertebrae) is one of the bony segments of the vertebral column. Vertebrae are irregular bones in the skeleton.

Parts of the vertebral column

The Appendicular Skeleton

Out of 206 bones in the human skeleton, the appendicular skeleton contains 126 bones. The appendicular skeleton consists of the following bones.

Bones in the appendicular skeleton

The clavicle

Also known as the collarbone. It is a long bone that acts as a rod between the shoulder blade (scapula) and the sternum (breastbone) to link them. Collarbone is the only long bone in our body that lies horizontally. There are two clavicles or collarbones in our skeleton. They are;

1. The right collarbone

2. The  left collarbone

The right and the left collarbones

The Scapula

The scapula (plural – scapulae) is also known as the shoulder blade. It connects the humerus (upper arm bone) with the collarbone. There are two scapulae.

1. The right scapula

2. The left scapula

The right and the left scapulae

The Humerus

The humerus (Plural – humeri) is a long bone in the upper arm. It runs from the shoulder to the elbow. There are two humeri.

1. The right humerus

2. The left humerus

The right humerus

The Radius and the Ulna

The radius (also called the radial bone) and the ulna are the two large bones of the forearm. Both run parallel to each other, extending from the elbow to the wrist. The ulna is located at the side of the forearm closest to the body.

There are 2 radial bones and 2 ulna bones in the human skeleton. They are;

1. Left and right radius

2. Left and right ulna 

The left radius and ulna

Carpals, Metacarpals and Phalanges of the hand

Each human hand consists of 27 bones. Therefore, altogether there are 54 bones in both hands. They are grouped as follows;

1. Wrist – Left carpals  (8 bones) and right carpals (8 bones)

2. Left metacarpals (5 bones) and right metacarpals (5 bones)

3. Fingers – Left phalanges (14 bones) and right phalanges (14 bones)

The eight short carpal bones of the wrist joint with the bones of the forearm and the bases of the five metacarpal bones of the hand.

The heads of the metacarpals joint with the bases of the knuckles, and the heads of the knuckles joint with the phalanges of the fingers and thumb.

There are fourteen phalanges to make up the four fingers and thumb. Each finger of the four fingers consists of three bones. The thumb only consists of two bones.

Bone structure of the left hand

The Pelvis

This is a symmetrical bone that looks like a basin. The meaning of pelvis is basin in Latin.

The pelvis is made of three major bones. These are;

1. The hip bone
2. The sacrum
3. The coccyx (tailbone)

Connected to either side of the sacrum, the pelvis contains two hip bones. Each hip bone contains three bones fused together. These are;

1. The ilium (the top part of the pelvis)
2. The pubis or pubic bone (the middle part of the pelvis)
3. The ischium (the lower part of the pelvis)

The pelvic girdle is a ring of bones that connects the vertebral column with the femur of the legs. The pelvic cavity is in the centre of the pelvis. It protects the digestive and reproductive organs and the rectum. The ligaments connected to the pelvis provide movement for running, walking, sitting, standing etc.

The Pelvis

The Femur

The femur is also known as the thigh bone. Thigh bone is the longest and the strongest bone in the human skeletal system. It extends from the hip to the knee. There are two femurs. They are;

1. The right femur

2. The left femur

The right femur

The Patella

This is simply known as the kneecap. Kneecap is a circular-triangular bone. It articulates with the femur. There are two patellas in our skeleton. They are;

1. The right patella (The right kneecap)

2. The left patella (The left kneecap)

The patella

The Tibia and the Fibula

The tibia and the fibula are the two long bones in the leg below the knee. The tibia, also known as the shinbone, is the stronger and the larger of the two bones. It connects the knee with the ankle bones. The fibula is the smaller of the two bones and also known as the calf bone. It is the thinnest of all the long bones. There are two tibia bones and two fibula bones. They are;

1. Left and right tibia

2. Left and right fibula

Right Tibia and Fibula

Tarsals, Metatarsals and Phalanges of the foot

Each human foot consists of 26 bones. Therefore, altogether there are 52 bones in both feet. They are grouped as follows;

1. Ankle – Left tarsals (7 bones) and right tarsals (7 bones)

2. Left metatarsals (5 bones) and right metatarsals (5 bones)

3. Toes – Left phalanges (14 bones) and right phalanges (14 bones)

The foot itself can be divided into three parts. they are;

1. The hindfoot

2. The midfoot

3. The forefoot

The hindfoot forms the heel and the ankle. It contains the largest tarsal bone to form the heel, the talus bone to form the ankle, and another two tarsal bones. The midfoot contains the rest of the tarsal bones. The forefoot consists of the metatarsals and the phalanges.

Bone structure of the right foot

Now you can get the idea of how each and every bone in the human skeletal system is important to us.