The Musculo skeletal System Support, Protection, Movement and Locomotion

1. The Musculoskeletal SystemSupport, Protection, Movement and Locomotion

2. Skeletal Functions • Framework for support • Transmits movement • Maintains shape • Protects internal organs from mechanical injury • Contains and protects the red bone marrow, one of the hemopoietic (blood-forming) tissues • Mineral reservoir - storage site for excess Ca and P • Storage of fats – yellow marrow

3. Hydrostatic skeleton • Fluid-filled closed chambers • Internal pressure generated by muscle contraction • e.g. sea anemone and worms

4. Exoskeleton • Shelled molluscs (CaCO3) • Arthropods (chitin) • Hard segments covering muscles and visceral organs • Muscles are attached to the exoskeleton • Restricts growth and size of insect  molting

5. Endoskeleton • Endoskeleton • Internal, often mineralized, connective tissue • Muscles on the outside • Cartilage – elasmobranchs • Other vertebrates – cartilage replaced by bone as embryo matures and develops

6. Appendicular and axial skeleton • Axial skeleton (80 bones) • axis of the body • support and protection of main organs • Skull • Sternum • Ribs • Vertebral Column + sacrum and coccyx • Appendicular skeleton (126 bones) • anchors appendages to the axial skeleton • Upper Extremities • Lower Extremities • Pectoral Girdle • Pelvic Girdle

7. Types of bones • Long bones • Long shaft (diaphysis) • Two joint surfaces (epiphyses) • Mostly compact bone • e.g. femur, tibia, fibula, radius, ulna • Short bones • Cube-shaped, mostly spongy bone • e.g. bones of wrist and ankle, patella • Flat bones • Thin and curved • e.g. skull and sternum • Irregular bones • Irregular and complicated shapes • e.g. spine and hips

8. Joints or articulations • Meeting of two bones • Types of joints • Immovable • Slightly movable • Freely movable

9. Bone Tissue • Compact bone • series of Haversian canals • concentric layers of bone cells (osteocytes) • new bone formed by osteocytes • Spongy bone • ends of long bones • less dense • contains red or yellow marrow • Periosteum • outer layer of bone • rich in nerve endings, blood, and lymphatic vessels • inner portion forms new bone or remodels existing bone

10. Types of bone cells • Osteoblasts • immature bone cells • manufacture hormones and enzymes that aid in bone mineralization • Osteocytes • mature osteoblasts in lacunae (spaces) • form bone, maintain matrix • act for calcium homeostasis • Osteoclasts • responsible for bone reabsorption and shaping • located on bone surfaces

11. Intramembranous ossification formation of the flat bones of the skull Endochondral ossification formation of long bones Bone formation

12. Bone remodeling • Resorption of bone (by osteoclasts) followed by replacement of bones (by osteocytes) • Functions to regulate calcium levels, repair damaged bones, and shape and sculpt the skeleton during growth • Rate is regulated by parathyroid hormones (PTH) and Vitamin D

13. Disorders of the skeletal system • Osteoporosis • Reduced bone density leading to fractures • Rickets and osteomalacia • Softening of bones leading to deformations and fractures • Arthritis • Inflammation of joints • Bone fractures • Scoliosis, kyphosis