Module 6 - Bones Flashcards
Bone Function
Functions
Support – attachment site for muscles – structural framework – support for soft tissue
Protection – internal organs have bony coverings
Movement – assist muscles
Mineral Homeostasis – store and release minerals – calcium and phosphorus
Production of blood cells – red marrow of bones – hemopoiesis
Triglyceride storage – yellow marrow
Bone Classification
Classification
Long bones – shaft with two ends - femur
Short – cube-like – ankle bones (tarsals)
Flat – thin and curved – skull bones
Irregular
Long Bone - Parts
Long Bones
Diaphysis
Epiphyses
Metaphysis
Hyaline cartilage
Periosteum
Medullary cavity
Endosteum
Red marrow
Yellow marrow
Diaphysis
Diaphysis – shaft
Epiphyses
Epiphyses – ends
Metaphysis
Metaphysis – area b/w diaphysis and epiphyses – epiphyseal plate
Hyaline cartilage
Hyaline cartilage – ends of bones – reduces friction and absorbs shock
Periosteum
Periosteum – connective tissue – covering surface – osteogenic cells – protect bones – assist in fracture repair – nourish bone tissue – attachment point for ligaments and tendons
Medullary cavity
Medullary cavity – in shaft – yellow marrow
Endosteum
Endosteum – lines inner medullar cavity
Red marrow
Red marrow – blood cell production
Yellow Marrow
Yellow marrow – fat storage
Bone Cells
Osteoprogenitor
Osteoblasts
Osteocytes
Osteoclasts – break down bone – reabsorption
Osteoprogenitor
Osteoprogenitor – stem cells
Osteoblasts
Osteoblasts – bone building cells
Osteocytes
Osteocytes – mature bone – maintain bone – principle cells
Osteoclasts
Osteoclasts – break down bone – reabsorption
Matrix
Matrix
inorganic salts – hydroxyapatite, calcium carbonate, and collagen fibres
salts deposited into framework of collagen fibres – calcification or mineralization
mineral salts = hardness
collagen = tensile strength
Compact Bone
Compact Bone
arranged in Osteons or Haversian Systems
Osteons
blood vessels, lymphatic vessels, nerves, and osteocytes
aligned in same direction – along stress lines
hollow passage
Calcified matrix
Spongy Bone
Spongy Bone
No osteons
Trabeculae
Canaliculi
Endosteum
Lamellae
Lacuna
Red marrow
Most structure of short, flat, and irregular bones
Epiphysis of long bones
Light
Supports and protects red marrow
Canaliculi
Canaliculi – light openings on surface – pores
Spongy bone
Trabeculae
Trabeculae – columns or beams of bone
spongy bone
Endosteum - Spongy Bone
Endosteum – lining outside
spongy bone - inside
Lamellae - spongy bone
Lamellae – concentric rings – like tree rings - spongy bone
Lacuna
Lacuna – spaces b/w rings – osteocytes and fluid - spongy bone
Ossification
Ossification – bone formation
Mesenchymal cells give template
2 types
Intramembranous
Endochondral
Intramembranous Ossification
Intramembranous Ossification
from or w/in fibrous connective tissue membranes
flat bones of skull and mandible
Intramembranous Ossification - Steps
4 Steps
Osteoblast cluster at centre of ossification – mesenchymal cells group
Osteoblasts secrete matrix – osteoid traps blasts – become osteocytes
Trabeculae lay down to form spongy bone – blood vessels come in – periosteum form, outer surface covering
Compact bone develops superficial – blood vessels condense to red marrow
Endochondral Ossification
Endochondral Ossification
Hyaline cartilage template
Early fetal development
Growth in length and thickness
Endochondral Ossification - Steps
5 steps
Cartilage model – mesenchymal cells differentiate into chondroblasts – form model – cells organize into columns – mature to chondrocytes
Calcification – chondrocytes at center hypertrophy – secrete matrix of collagen and glycoprotein – calcification of tissue
Primary Ossification center – model becomes vascular – chondrocytes die – bone marrow formed at center – osteoprogenitor cells come and differentiate into osteoblasts – in diaphysis
Secondary Ossification center – epiphysis – ossification continues in the diaphysis – new site in ends of bones – ends become vascular – ossification begins at ends
Epiphyseal plate formation – joint surface as articular cartilage
Remodeling
Remodeling
Constantly breaking down and reform
Remodeling Phases
Phases:
Activation – pre-osteoclasts are attracted to area – fuse into multinucleated osteoclasts
Resporption – osteoclasts dig out resorption pit or tunnel – calcium released into blood – osteoclasts disappear
Reversal – stem cells appear and differentiate into osteoblasts
Formation – release osteoid = new matrix – matrix is mineralized with calcium and phosphorous
Quiescense – dormant lining cells
Minerals
Minerals needed
Calcium
Phosphorus
Magnesium
Vitamins
Vitamins
A
B12
C
D
K
Hormones
Hormones
Thyroid hormones
Insulin
calcitonin
Human growth hormone:
Estrogen
Testosterone
Calcium Homeostasis
Calcium Homeostasis
Blood level calcium ions (Ca2+)
Normal: 10mg/dL
Regulated for physiology of:
Cardiac
Nerve
Enzyme
Blood
Parathyroid hormones (PTH)
Parathyroid hormones (PTH) – below normal -10mg/dL
Regulated Ca2+ of bones and blood
Increases blood calcium levels
Parathyroid gland
Osteoclasts release Ca2+ from bones
Calcium is reabsorbed from urine by the kidneys
Calcium absorption in the small intestine increases via vitamin D synthesis
Calcitonin (CT)
Calcitonin (CT) – above normal +10mg/dL
Thyroid gland
Decreases blood Ca2+
Thyroid gland releases calcitonin
Osteoclast activity is inhibited
Ca2+ reabsorption in kidneys decreases
