Long Bones of Arms and Legs

The skeleton makes up the human body. The skeleton is made up of bones. Both the bones and muscles help in the movement of the skeleton and thus in the movement of the human body. Movement is essential for living organisms. In an organism, the internal and external body parts, both show movement. Long bones in the body are present in the arms and legs of the human body. These bones are small at the time of birth and start growing to their full size later on. The arm and leg bones are collectively known as the limbs of the human body. 

The long bones of arms and legs are mainly responsible for determining the height of the human, help in the movement and also play a major role in maintaining the equilibrium of the body. We will study the arm skeleton, femur and humerus that are the human leg bones. Together they all make up the long bones of arms and legs. 

Skeletal System

This system is made from external and internal structures that can be living or dead in nature. They are hardened structures that help in forming the support system to the body. They also serve the purpose of protection. 206 bones are present in an adult skeleton. Axial and appendicular skeleton are the subparts in which the skeletal system is divided. The long bones in human body that make up the arms and legs are made up of an appendicular skeleton. The appendicular skeleton has 126 bones. 

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Limb Bones 

In our body, we have two pairs of limbs. They are known as the forelimbs and the hindlimbs. The forelimbs and hindlimbs have 30 bones each. Humans have a pair of forelimbs. 30 bones are present in each of the forelimbs. These bones then help in forming the different parts of the arm. The different parts of arms are known as the upper arm, lower arm, forearm and hand. The humerus is the single long bone in human body that is present in the upper arm. Radius and the ulna are also long bones. 

These bones are present in the lower arm. The radius and ulna run parallel to each other or they cross each other. The ulna is longer than the radius. The human hand is made up of 27 bones. Out of these 27 bones, 8 bones are present in the wrist region and 5 bones are present in the palm region. These eight bones are known as carpal bones and the five bones are known as metacarpals. In the fingers, there are fourteen bones present. These all fourteen bones together are known as phalanges. 

The 8 Bones of the Carpal are:

• Trapezium

• Trapezoid

• Scaphoid

• Lunate

• Hamate

• Capitate

• Pisiform

• Triquetrum

Hind Limbs

The leg bones names are Femur, tibia, fibula. They together form the hind limbs. The humans have a pair of hind limbs. There are 30 bones present in each hind limb. These 30 bones from the thigh, the shank, the knee and the foot. The femur that is present in the hind limb is the longest and the strongest bone in the human body. It is present in the thigh. This bone also has bone marrow. This bone marrow helps in producing the red blood cells and also antibodies to maintain the immunity of the human body. Tibia and fibula are the other leg bones names. They are present in the shank region and are present below the femur. The patella bone helps in joining the tibia and fibula to the femur. 

In the ankle, we have seven bones. These are known as the tarsals. The sole is made up of five bones and these are known as the metatarsals. The toes are made from fourteen bones and these are known as the phalanges. The tibia is longer than the fibula. Tibia is articulated with the bone of the ankle at the lower end. The fibula is articulated with the tibia only at the lower end. The fibula is also articulated to the bone of the ankle at the lower end. So, it is articulated to both. Tibia is present towards the thumb side and the fibula is present towards the little finger side. Patella is the sesamoid bone and it helps in forming the knee cap. 

The Five Ankle Bones are:

• Calcaneum

• Talus

• Cuboid

• Navicular

• Cuneiform

The femur, tibia and fibula make up the long bones names of the hind limbs. 

Pectoral Girdle

This girdle is part of the appendicular skeleton. It is also known as the shoulder girdle. It is present between the forelimb and the axial skeleton. It is made up of the scapula or the shoulder bone and the clavicle. The clavicle is also known as the collarbone. The functions of the pectoral girdle are:

• It provides a glenoid cavity that helps in the articulation of the head of the humerus. 

• The pectoral girdle serves as a site for attachment of arm muscles. 

• It protects the internal organs in this area that are very delicate in nature.

Pelvic Girdle 

It is also known as the hip girdle. It is an irregular trough-shaped structure. It is present between the hind limbs and the axial skeleton. Towards its posterior end, it is attached to the sacrum. These sacrum and coccyx are responsible for forming the basin-shaped pelvis. The functions of the pelvic girdle are:

• It serves as a site for the attachment of leg muscles.

• It helps in providing strength to the sacral region.

• It helps in transferring the weight of the whole body to the hind limbs. 

• The hind limb bones are also attached to the pelvic girdle.

• These girdles form a hollow space. This space is known as the pelvis. 

Movement of the External and Internal Body Parts

These all the bones of the hindlimb, forelimb and girdles help in the process of movement and locomotion. The movement is done by both the internal body parts and the external body parts. 

Movements of External Body Parts Help in:

• It helps to maintain the equilibrium of the body. It is done by limbs, heads and trunks. 

• The organisms are able to catch food by the movement of limbs, appendages, jaws and tentacles. 

• Ingestion, defence and locomotion are also done by external body parts. 

Movement of Internal Body Parts:

• These internal body parts help in the proper functioning of various cells, tissues and organs of the body. This in turn helps the organism to carry out other vital functions of the body.

• The heart pumps blood to all the parts of the body. 

• The peristaltic movement of the food pipe helps in the process of digestion.