Human Skeleton | Axial Skeleton Appendicular Skeleton |

Human Skeleton.

The human skeleton can be divided into two parts, axial skeleton and appendicular skeleton.

1. Axial Skeleton:

The axial skeleton includes the skull, the vertebrae and the ribs and sternum.

Skull:

It is made up of cranial and facial bones:

➤ Cranium bones:

The cranium consists of 8 bones. Four are unpaired and two paired.

(a). Paired bones:

Parietal bones

Temporal bones

(b). Unpaired bones:

Frontal bone.

Occipital bone.

Sphenoid bone.

Ethmoid bone.

➤ Facial bones:

 There are 14 facial bones. Six are paired and two are unpaired.

(a). Paired bones:

Maxilla

Zygomatic

Nasal 

Lacrimal

Palatine

Inferior concha

(b). Unpaired bones:

Mandible

Vomer

Vertebral Column:

Vertebral column extends from the skull to the pelvic region. It forms the backbone. It protects the spinal cord inside. Normally, vertebral column has four curvatures. So it provides more strength than the straight column. The vertebral column is composed of 33 vertebrae. These vertebrae are named according to their location i. e. cervical , thoracic, lumber and pelvic.

(i)  Cervical vertebrae:

These are composed of seven vertebrae present in the neck region. The first two vertebra are: atlas vertebra and axis vertebra.

(ii) Thoracic vertebrae:

There are 12 thoracic vertebrae. These are located in theracic region.

(iii) Lumber vertebrae:

There are five lumber vertebrae. These are present in the lumber region.

(iv) Pelvic vertebrae:

There are nine pelvic vertebrae. These forms two sets of vertebrae:

➤ Sacrum: It is formed by the fusion of anterior five vertebrae.

➤ Coccyx: It is formed by the fusion of posterior four vertebrae.

Rib Cage:

Rib cage is composed of 12 pairs of ribs. These ribs articulate with the thoracic vertebrae. Ten ribs are connected anteriorly with the sternum directly or through the costal arch. The lower two pairs of ribs are called floating ribs as they are not attached with the sternum. The ribcage provides support to semi-vacuum chamber called chest cavity.

2. Appendicular Skeleton:

The appendicualr skeleton consists of pectoral girdle with appendages (fore limb) and pelvic girdle with appendages (hind limb).

Pectoral girdle and Fore limb:

Pectoral girdle is composed of scapula, suprascapula and clavicle. The clavicle connects scapula with sternum. The fore limb consists of one humerus, two radius and ulna, eight carpals, five metacarpals and fourteen phalanges.

➤ Humerus:

Its proximal end forms ball and socket joint with scapula. While its distal end form hinge joint with the radius and ulna.

➤ Radius and Ulna:

They form multistage joint with eight wrist bones or carpals at their distal end.

➤ Carpals:

There are 8 carpals. They form the wrist of arm

➤ Metacarpal:

There are five metacarpal. They form the framework of the palm of hand.

➤ Phalanges:

There are 14 phalanges which are attached to the metacarpals. They support the finger.

Pelvic Girdle and Hind Limb:

Pelvic girdle attaches the hind limb with the vertebral column. It consists of two coxal bones. Each coxal bone is formed by the fusion of three bones, ilium, ischium and pubis. The pelvic girdle supports the pelvic region. Hind limb consists of following bones:

➤ Femur:

There is single femur in each leg. The proximal end of femur forms hip joint with the pelvic girdle or hip bone. It is a ball and socket joint. The distal end of the femur forms knee joint with the proximal end of the tibia and fibula.

➤ Tibia and fibula:

These are wo in number in each leg. The distal end of the tibia and fibula forms joint with tarsal bones.

➤ Tarsals:

There are eight tarsal which forms ankle. The distal end of the tarsals is attached with the five metatarsal.

➤ Metatarsal:

There are five metatarsals. They form sole of the foot. Their distal ends are attached with the fourteen phalanges.

➤ Phalanges:

There are five rows of fourteen phalanges of the toes. They are present in the fingers.