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Division of skeletal system

  • The human skeletal system can be divided into two main divisions: the axial skeleton and the appendicular skeleton.

  • The axial skeleton forms the central axis of the body, while the appendicular skeleton consists of the limbs and girdles.

  • Here is the classification of the skeletal system, including the names of all bones

Division of skeletal system

A. Axial Skeleton (80 Bones) (Division of skeletal system)

  • The axial skeleton forms the central axis of the body and consists of 80 bones.

  • Its primary functions are to protect vital organs in the head, neck, and trunk, and to support the body’s weight.

Axial Skeleton (80 Bones)
Axial Skeleton

Skull (22 Bones)

  1. Cranial Bones (8 Bones):

    • Frontal (1)

    • Parietal (2)

    • Occipital (1)

    • Temporal (2)

    • Sphenoid (1)

    • Ethmoid (1)

  2. Facial Bones (14 Bones):

    • Maxillae (2)

    • Zygomatic (2)

    • Nasal (2)

    • Lacrimal (2)

    • Palatine (2)

    • Inferior Nasal Conchae (2)

    • Vomer (1)

    • Mandible (1)

Features:

  • The skull consists of 22 bones, including 8 cranial bones and 14 facial bones, joined by immovable joints called sutures.

  • The mandible (lower jaw) is the only movable bone in the skull.

Functions:

  • Protects the brain and forms the structure of the face.

  • Provides attachment points for muscles involved in facial expressions and mastication (chewing).

Auditory Ossicles (6 Bones)

  • Located in each ear:

    • Malleus (2)

    • Incus (2)

    • Stapes (2)

Function:

  • Transmit sound vibrations from the eardrum to the inner ear.

Hyoid Bone (1 Bone)

  • A U-shaped bone in the neck that supports the tongue and is associated with swallowing.

Vertebral Column (26 Bones)

  1. Cervical Vertebrae (7):

    • C1 (Atlas), C2 (Axis), C3-C7

  2. Thoracic Vertebrae (12):

    • T1-T12

  3. Lumbar Vertebrae (5):

    • L1-L5

  4. Sacrum (1):

    • Composed of 5 fused sacral vertebrae

  5. Coccyx (1):

    • Composed of 3-5 fused coccygeal vertebra

Features:

  • The vertebral column is composed of 33 vertebrae, including cervical, thoracic, lumbar, sacral (fused), and coccygeal (fused) vertebrae.

  • Separated by intervertebral discs.

Functions:

  • Provides support for the body, protects the spinal cord, and serves as an attachment point for muscles and ligaments.

  • Allows for flexibility and movement.

Rib Cage (25 Bones)

  1. Ribs (24 Bones):

    • 12 pairs:

      • True Ribs (1-7): Attach directly to the sternum via costal cartilage.

      • False Ribs (8-10): Attach to the cartilage of the rib above.

      • Floating Ribs (11-12): Do not attach to the sternum.

  2. Sternum (1 Bone):

    • Composed of the manubrium, body, and xiphoid process.

Features:

  • The rib cage consists of 12 pairs of ribs and the sternum.

Functions:

  • Protects vital organs such as the heart and lungs.

  • Supports the thoracic cavity and aids in respiration.

B. Appendicular Skeleton (126 Bones)

  • The appendicular skeleton consists of 126 bones and is responsible for mobility.

  • It includes the limbs, girdles, and attachment points for limb muscles.

Appendicular Skeleton

Pectoral (Shoulder) Girdles (4 Bones)

  1. Clavicles (2 Bones):

    • Collar bones

  2. Scapulae (2 Bones):

    • Shoulder blades

Features:

  • Each pectoral girdle consists of a clavicle and a scapula.

Functions:

  • Connects the upper limbs to the axial skeleton.

  • Provides a stable base for the attachment and movement of upper limb muscles.

Upper Limbs (60 Bones)

  1. Humeri (2 Bones):

    • Upper arm bones

  2. Ulnae (2 Bones):

    • Medial forearm bones

  3. Radii (2 Bones):

    • Lateral forearm bones

  4. Carpal Bones (16 Bones):

    • Wrist bones, 8 in each wrist:

      • Scaphoid, Lunate, Triquetrum, Pisiform, Trapezium, Trapezoid, Capitate, Hamate

  5. Metacarpal Bones (10 Bones):

    • Palm bones, 5 in each hand

  6. Phalanges (28 Bones):

    • Finger bones, 14 in each hand:

      • 3 in each finger (Proximal, Middle, Distal), 2 in each thumb (Proximal, Distal)

Features:

  • The upper limbs consist of the humerus, radius, ulna, carpal bones, metacarpals, and phalanges.

Functions:

  • Allow for a wide range of movements and dexterity, enabling actions such as grasping, lifting, and manipulating objects.

Pelvic (Hip) Girdle (2 Bones)

  1. Coxal Bones (2 Bones):

    1. o    Each formed by the fusion of the ilium, ischium, and pubis.

Features:

  • The pelvic girdle consists of two coxal bones.

Functions:

  • Supports the weight of the upper body when sitting and standing.

  • Provides attachment points for the lower limbs and protects organs in the pelvic region.

Lower Limbs (60 Bones)

  1. Femurs (2 Bones):

    • Thigh bones

  2. Patellae (2 Bones):

    • Kneecaps

  3. Tibiae (2 Bones):

    • Shin bones (medial)

  4. Fibulae (2 Bones):

    • Calf bones (lateral)

  5. Tarsal Bones (14 Bones):

    • Ankle bones, 7 in each ankle:

      • Talus, Calcaneus, Navicular, Cuboid, Medial Cuneiform, Intermediate Cuneiform, Lateral Cuneiform

  6. Metatarsal Bones (10 Bones):

    • Foot bones, 5 in each foot

  7. Phalanges (28 Bones):

    • Toe bones, 14 in each foot:

      • 3 in each toe (Proximal, Middle, Distal), 2 in each big toe (Proximal, Distal)

Features:

  • The lower limbs consist of the femur, patella, tibia, fibula, tarsal bones, metatarsals, and phalanges.

Functions:

  • Provide support, stability, and mobility for the body, enabling actions such as walking, running, jumping, and maintaining balance.


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