skeletal system

• Functions of Skeletal System

  • Support
  • Protection
  • Assistance in Movement
  • Mineral homeostasis
  • Blood Cell Production
  • Fat Storage
• Support


  It provides structural support and shape to the body allowing us to stand upright
• Protection


  It protects the most important internal organs from injury
• Assistance in Movement


  Our bones assist in movement by providing a structure for muscles to pull against
• Mineral homeostasis


  It stores several minerals, especially calcium and phosphorus, which contribute to the strength of bone. Bone tissue stores about 99% of the body's calcium. On demand, bone releases minerals into the blood to maintain mineral balances (homeostasis) and to distribute the minerals to other parts of the body
• Blood Cell Production


  Within certain bones, such as the red bone marrow, hematopoiesis occurs. Hematopoiesis is the process of blood cell formation including red blood cells, white blood cells, and platelets
• Fat Storage


  Bones store fat in its marrow, specifically yellow bone marrow. It can release energy when your body needs it. Yellow bone marrow primarily consists of adipocytes, which are specialized cells for storing fat
• Bone tissue makes up about 18% of the weight of the human body
• Types of Skeleton


  • Hydrostatic Skeleton
  • Exoskeleton
  • Endoskeleton
• Hydrostatic Skeleton


  Consists of fluid constrained within a layer of flexible tissue. Many invertebrate animals have hydrostatic skeleton such as earthworms, jellyfish, leeches, snails, squids, and etc.
• Exoskeleton


  It is a skeleton that protects the animal from the outside. They can move by their muscles contracting and relaxing. Examples: Spider, Beetle, Snail, Scallop, Shrimp
• Endoskeleton


  It is an internal support structure found inside the bodies of many animals, including us, humans
• Division of the Skeleton

  • Axial
  • Appendicular
• Axial Skeleton


  It is located along the central axis of the body, The axial skeleton shields the vital and soft body parts. It includes the skull, hyoid bone, ribs, auditory ossicles, vertebral column, and thoracic cage
• Appendicular Skeleton


  It refers to the portion of skeleton that includes the bones of the limbs and the bones that connect them to the axial skeleton. It consists of the pectoral girdle, upper limbs, pelvic girdle, and lower limbs
• Types of Bones


  • Long Bones
  • Short Bones
  • Flat Bones
  • Irregular Bones
  • Sesamoid Bones
• Long Bones


  Have greater length than width and are slightly curved for strength. They consist mostly of compact bone tissue in their shaft but have considerable amounts of spongy bone tissue in their ends. Examples include the femur, tibia, fibula, humerus, ulna, radius, metacarpals, and phalanges
• Short Bones


  Are cube-shaped or have a box-like appearance. They provide support and stability and contribute to the movement of joints. Examples include the carpals and tarsals
• Flat Bones


  Are generally thin and composed of two nearly parallel plates of compact bone tissue enclosing a layer of spongy bone tissue. Examples include the cranial bones, sternum, ribs, and scapulae
• Irregular Bones


  Do not fit into any specific category due to their unique shapes. They serve as providing protection for delicate internal organs or serving as anchor points for muscles and tendons. Examples include the backbones, facial bones, and certain bones of the pelvis
• Sesamoid Bones


  Are small bones commonly found embedded within a muscle or tendon near joint surfaces. They protect tendons from excessive wear and tear
• Bone Tissue


  A highly rigid connective tissue that forms the skeleton of vertebrates, containing blood vessels and cells like osteoclasts, osteocytes, osteoblasts, and lining cells
• Cartilage


  A thin, fibrous, flexible connective tissue, mainly found in the external ear, larynx, respiratory tract and the articulating surface of the joints, lacking blood vessels so growth and development is slower
• Cells in Bone Tissue


  • Osteoclasts - cells that break down bones
  • Osteoblasts - cells that form new bones
  • Osteocytes - cells inside the bone responsible for bone health
  • Lining Cells - regulate passage of calcium into and out of the bone
• Skeletal System


  • Provides the framework and support structure for the body
  • Protects organs like the brain, spinal cord, heart, and lungs
  • Allows for movement through the muscular system
• Bone Growth


  1. Ossification - the process of laying down new bone material

  2. Intramembranous ossification - bone forms directly within mesenchyme

  3. Endochondral ossification - replacement of cartilage with bone tissue
• Chondrogenesis


  The process of creating chondrocytes, the cells responsible for producing cartilage
• Growth Plates


  Thin discs of cartilage located near the ends of long bones
• Bone Remodelling Cycle


  1. Resorption - breaking down bone material

  2. Reversal - osteoclasts perform apoptosis and osteoblasts are recruited

  3. Formation - creating new bone material
• Bones strengthen through exercise
• Bones are self-healing
• Calcium Homeostasis


  Bones absorb and store calcium and phosphate, which is used in muscle contraction, nerve transmission, blood clotting, and bone formation
• Hypocalcemia - Blood Calcium drops


  Parathyroid hormone released, leading to bone resorption
• Hypercalcemia - Calcium elevated


  Calcitonin released by thyroid, decreasing resorption and increasing formation/osteoblast activity
• Osteoporosis


  Bones lose more calcium than they add, causing them to be less dense and weaker