7.1 Divisions of the Skeletal System

The skeletal system is our body's framework, providing support, protection, and movement. It's divided into the axial skeleton, which forms our central axis, and the appendicular skeleton, which includes our limbs and the structures that attach them to our core.

Our skeleton isn't just for structure - it's a multitasker. It shields vital organs, stores minerals, and even produces blood cells. From the skull protecting our brain to the tiny bones in our toes, each part plays a crucial role in keeping us moving and functioning.

Functions and Divisions of the Skeletal System

Functions of skeletal system

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• Provides structural framework for the body serves as attachment points for muscles, tendons, and ligaments enabling movement and support
• Shields vital organs from injury cranium protects brain, vertebrae protect spinal cord, rib cage protects heart and lungs
• Stores minerals calcium and phosphate in bone matrix released into bloodstream to maintain homeostasis (calcium balance)
• Produces blood cells through hematopoiesis red bone marrow generates erythrocytes (red blood cells), leukocytes (white blood cells), and thrombocytes (platelets)

Axial vs appendicular skeletons

• Axial skeleton forms vertical axis of body consists of 80 bones skull, vertebral column, rib cage, sternum primarily involved in protection and support
• Appendicular skeleton composed of bones of appendages (limbs) and girdles that attach them to axial skeleton consists of 126 bones pectoral girdle and upper limbs, pelvic girdle and lower limbs primarily involved in movement and locomotion (walking, running)

Components of axial skeleton

• Skull divided into cranium (brain case) frontal, parietal, temporal, occipital, sphenoid, ethmoid bones and facial bones maxillae, zygomatic, nasal, lacrimal, palatine, inferior nasal conchae, vomer bones also includes mandible (lower jaw)
• Vertebral column 33 vertebrae divided into five regions cervical (7), thoracic (12), lumbar (5), sacral (5 fused), coccygeal (4 fused) with intervertebral discs between vertebrae
• Rib cage 12 pairs of ribs true ribs (1-7) directly attach to sternum via costal cartilage, false ribs (8-12) indirectly attach or do not attach to sternum ribs 8-10 attach to costal cartilage of rib above, ribs 11-12 (floating ribs) do not attach to sternum
• Sternum (breastbone) composed of manubrium, body, and xiphoid process

Structures of appendicular skeleton

• Pectoral girdle includes clavicle (collarbone) and scapula (shoulder blade)
• Upper limbs consist of:
  1. Humerus (upper arm bone)
  2. Radius and ulna (forearm bones)
  3. Carpals (wrist bones)
  4. Metacarpals (hand bones)
  5. Phalanges (finger bones)
• Pelvic girdle composed of hip bones (coxal bones) ilium, ischium, pubis and sacrum, coccyx (part of axial skeleton but functionally part of pelvic girdle)
• Lower limbs include:
  1. Femur (thigh bone)
  2. Patella (kneecap)
  3. Tibia and fibula (lower leg bones)
  4. Tarsals (ankle bones)
  5. Metatarsals (foot bones)
  6. Phalanges (toe bones)

Skeletal system components and development

• Bone tissue: provides structure and strength to the skeleton
• Joints: connect bones and allow for movement
• Ligaments: tough connective tissue that binds bones together at joints
• Cartilage: flexible connective tissue found in joints, rib cage, and other areas
• Ossification: process by which bone tissue forms and develops