1. The Musculoskeletal System Support, 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 Short bones Flat bones Irregular 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. Bone formation
Intramembranous ossification  formation of the flat bones of the skull
Endochondral ossification  formation of long bones

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