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:

A. Axial Skeleton (80 Bones)

• 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.

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 vertebrae

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.

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.