Musculoskeletal System Bones

Objectives 1) State 6 basic functions of the skeleton 2) State the gross structure of the axial and appendicular skeleton 3) Describe the basic structure of mature bone matrix 4) State the function of chondroblasts, fibroblasts, osteoblasts, osteocytes and osteoclasts 5) Describe the structure and location of cancellous and compact bone

Objectives 6) Describe the 3 patterns of bone ossification 7) Describe the typical stages of long bone development 8) List and state the function of nutrition, vitamins, minerals and hormones in bone growth 9) Describe the role of vitamin D, parathyroid hormone and calcitonin in calcium regulation and homeostasis 10) Identify the location of the main bones of the human body

Basic functions of the skeleton Support Framework, supports soft tissue, point of attachment for muscles 2) Protection For internal organs e.g. brain, lungs, heart etc

Basic functions of the skeleton 3) Facilitates movement Skeletal muscle contraction causes movement at movable joints 4) Storage of minerals Ca and P stored and released when needed

Basic functions of the skeleton 5) Blood cell formation Red bone marrow in certain bones produces blood cells 6) Storage of energy Lipids stored in yellow bone marrow

Skeleton Axial skeleton: skull, vertebral column, ribs, sternum Appendicular skeleton: scapulae, clavicles, hip bones limb bones

Types of Bones Flat (e.g. skull) Irregular Short Long Bones are either: Flat (e.g. skull) Irregular (e.g. vertebrae) Short (e.g. carpals) Long (e.g. phalanges)

Basic structure of Bone Matrix 65% Calcium and Phosphate salts Inorganic  weight bearing strength 33% Collagen Organic material, rope like and strong  strong flexible framework (Loss of collagen  bones become ‘brittle’) 2% cells

Typical Long Bone

Bone Cells Osteoblasts: bone building cells, produce bone matrix Osteocytes: osteoblast surrounded by matrix (i.e. mature bone cells) Osteoclasts: bone consuming cells, remove/shape bone Chondroblasts: cells that work on cartilage to form bone Fibroblasts: cells that form collagen

Cancellous / Trabecular bone Light, sponge like Strong due to trabeculae Spaces contain red or (Compact bone) yellow bone marrow Cancellous bone Found: centre of flat bones, ends of long bones

Trabecular / Cancellous bone Section through the head of the femur, showing the outer layer of compact bone and the soft centre of trabecular bone, filled with red bone marrow

Compact Bone More dense, fewer spaces than cancellous bone Blood vessels and nerves within Haversian canals Circumferential lamellae is very strong  protection

Compact Bone

Bone Ossification Bone ossification = laying down of minerals Bones are formed from ossification of: Cartilage  Long bones Membranes  Flat bones Tendons  Sesamoid bone

Development of a Typical Long Bone

Bone Growth: Nutrition and Hormones Vitamin C for collagen synthesis Vitamin D for normal absorption of Ca from the intestine Growth hormone for bone growth and development Thyroid hormone also influences bone and cartilage growth Sex hormones (oestrogen and testosterone) influence bone growth and account for growth spurt at puberty

Growth Hormone

Effect of Growth Hormone Excess GH secretion in children  Gigantism (Maintain normal body proportions) Excess GH secretion in adults after the epiphyseal discs are sealed  Acromegaly  No increase in height but Growth of soft tissue  Elongation of jaw, deformities in hands, feet, and bones of face Inadequate secretion of GH during childhood  short stature

Acromegaly

Calcium regulation and homeostasis High blood Ca  Thyroid gland  Calcitonin  Inhibits osteoclast activity  Bone breakdown inhibited  Lowers blood Ca Low blood Ca  Parathyroid glands  Parathyroid hormone  Stimulates osteoclast activity  Mobilization of Ca from bone  Raises blood Ca

Bones Identify on the model of the skeleton the following bones: Cranium, clavicle, sternum, ribs, humerus, radius, ulna, carpals, metacarpals, phalanges, pelvis, femur, patella, tibia, fibula, tarsals, metatarsals, phalanges, cervical vertebrae, scapula, thoracic vertebrae, lumbar vertebrae, sacrum, coccyx, calcaneus