BIO 304 · Human Anatomy & Physiology
Bone Tissue & Bone Growth
Skeletal System · Module 5
A reference for the Bone Tissue video. Bone is a living, organ-system-active tissue. It builds, breaks down, and rebuilds throughout your life; it stores calcium and houses the marrow.
How to use this sheet Toggle the toolbar above. Notes prints the full reference for review. Study prints as a fill-in-the-blank worksheet , print it, then write each definition while you watch the video or read your book. Quiz me is on-screen typing practice; type the term, click Reveal to check yourself.
- Name the four bone cell types and the role of each in bone turnover.
- Distinguish compact from spongy bone by structure and function.
- Contrast intramembranous and endochondral ossification, and locate the epiphyseal plate.
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Bone Cells & Matrix
Four bone cells
- Osteogenic (osteoprogenitor)stem cells in periosteum & endosteum; divide into osteoblasts
- Osteoblastbone builder; secretes osteoid (collagen + ground substance)
- Osteocytemature bone cell trapped in lacuna; maintains matrix
- Osteoclastmultinucleate giant cell; dissolves bone (resorption)
Matrix composition
- Organic (~33%)osteoid: collagen fibers + ground substance · tensile strength
- Inorganic (~67%)hydroxyapatite (calcium phosphate crystals) · compression strength
Compact bone
- Osteon (Haversian system)cylindrical unit of compact bone
- Central canalruns lengthwise; blood vessels and nerves
- Lamellaeconcentric rings of matrix
- Lacunaesmall spaces housing osteocytes
- Canaliculitiny channels connecting lacunae; nutrient diffusion
- Perforating (Volkmann) canalsrun perpendicular; connect central canals
Growth & Remodeling
Spongy (cancellous) bone
- Trabeculaelattice of bony struts; aligned along stress lines
- No osteonsosteocytes nourished by diffusion from marrow spaces
- Houses red marrowhematopoiesis — blood cell production
Ossification
- Intramembranousbone forms directly from mesenchyme · flat skull bones, clavicle
- Endochondralcartilage model is replaced by bone · most bones
- Primary ossification centerin diaphysis (shaft); forms first
- Secondary ossification centerin each epiphysis (end)
Growth in length & width
- Epiphyseal (growth) platecartilage between epiphysis and diaphysis; longitudinal growth
- Epiphyseal lineclosed growth plate — growth stopped (late teens/early 20s)
- Appositional growthosteoblasts add bone under periosteum; bone grows wider
Calcium homeostasis
- Parathyroid hormone (PTH)low blood Ca²⁺ → PTH ↑ → osteoclasts active → Ca²⁺ up
- Calcitoninhigh blood Ca²⁺ → calcitonin → deposits Ca²⁺ into bone
- Vitamin Denables Ca²⁺ absorption from the gut
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