Human Skeleton

The human skeleton is divided into two parts, the axial skeleton, and the appendicular skeleton. The axial skeleton consists of the skull, chest cage, vertebral column, and hyoid bone, whereas the appendicular skeleton comprises the pectoral girdle, pelvic girdle, forelimbs, and hindlimbs.

Human skull (side view)

Axial Skeleton

The axial skeleton includes the skull, chest cage, vertebral column, and hyoid bone.

Skull

The skull or cranium is a box cavity that protects the brain. The cranium consists of eight bones, out of which four are unpaired and two are paired. The bones of the face are 14 in number, out of which six are paired and two are unpaired. The skull bones are mostly flat and immovable, and they come together at joints called sutures.

Chest Cage

The chest cage consists of twelve pairs of ribs. Ten ribs are connected interiorly with the sternum, and the other two are floating. The rib cage provides support for a semi-vacuum chamber called the chest cavity.

Vertebral Column

The vertebral column supports the weight of the body and provides axial support to the head. It consists of 33 vertebrae named according to their location in the vertebral column. The vertebral column has four curvatures that provide more resiliency and strength in an upright posture than a straight column could.

Inferior nasal concha

An inferior view of the skull 

Interior view of Hyoid Bone 

Hyoid Bone

The hyoid bone is a small bone that lies at the tongue. It gives attachment to the tongue and serves as the site for the attachment of muscles associated with swallowing. It does not articulate with any other bone of the head.

Appendicular Skeleton

The appendicular skeleton comprises the pectoral girdle, pelvic girdle, forelimbs, and hindlimbs.

Vertebral Column

Pectoral Girdle

The pectoral girdle consists of a pair of clavicles and a pair of scapulas. The clavicles are a pair of collar bones that form the front of the pectoral girdle, and the scapulas are two shoulder blades that form the back part of the pectoral girdle.

Forelimb

The forelimb consists of the humerus, radius and ulna (forearm bones), carpals (eight short bones forming the wrist), metacarpals (five short bones forming the palm), and phalanges (three bones forming the fingers, two bones forming the thumb).

Chest Cage

Hindlimb

The hindlimb consists of the femur (thigh bone), patella (kneecap), tibia and fibula (leg bones), tarsals (seven short bones forming the ankle), metatarsals (five short bones forming the foot), and phalanges (fourteen bones forming the toes).

Pelvic Girdle

The pelvic girdle is a bony ring that protects the organs in the lower abdomen. It consists of two hip bones, which are large and heavy, and they articulate with the sacrum at the back.

Pectoral Girdle

The pelvic girdle is formed by a pair of hip bones, each of which is made up of three bones: ilium, ischium, and pubis. The two hip bones are joined anteriorly by a cartilage called pubic symphysis. The pelvic girdle protects and supports the reproductive and urinary organs, as well as the lower part of the digestive tract. It also provides a stable foundation for the attachment of the lower limb bones.

Hindlimb

The hindlimb, also known as the lower limb, consists of the following bones:

Femur: The femur, or thigh bone, is the longest and strongest bone in the human body. It articulates with the hip bone proximally and the tibia and patella distally.

Patella: The patella, or kneecap, is a small, triangular bone located in front of the knee joint. It protects the knee joint and helps to increase the leverage of the quadriceps muscle.

Tibia: The tibia, or shinbone, is the larger of the two bones in the lower leg. It articulates with the femur proximally and the ankle bones distally.

Forelimb

Fibula: The fibula is the smaller of the two bones in the lower leg. It is located on the lateral side of the tibia and provides attachments for muscles of the leg and foot.

Tarsals: The tarsals are seven bones that form the ankle joint.

Metatarsals: The metatarsals are five long bones that form the sole of the foot.

Phalanges: The phalanges are the bones that form the toes. There are 14 phalanges in each foot: three in each of the first four toes and two in the big toe.

Functions of the Skeletal System

The skeletal system performs several important functions in the human body, including:

Support: The skeletal system provides structural support for the body and helps to maintain its shape.

Protection: The bones of the skull, rib cage, and pelvis protect vital organs such as the brain, heart, lungs, and reproductive organs.

Movement: The skeletal system provides a framework for muscles to attach to, allowing for movement of the body.

Blood cell production: The bone marrow in certain bones produces red blood cells, white blood cells, and platelets.

Mineral storage: Bones serve as a storage site for important minerals such as calcium and phosphorus, which are necessary for many metabolic processes in the body.

The skeletal system is composed of the axial and appendicular skeleton, which together provide support, protection, and movement to the body. The individual bones of the skeletal system work together to form a strong, flexible, and dynamic structure that allows us to stand, move, and perform a wide range of activities.

Humerus

Pelvic Girdle

Hindlimb