Bone Histology & Intramembraneous Ossification Flashcards
Bone Properties
• Specialized form of ____ with a mineralized collagen matrix.
• Bones are units of the skeletal system.
– Individual bones are made up of bone tissue, marrow, cartilage and periosteum
• Physical properties:
– Strength: resistance to compression, shear and tensile strength.
– Reservoir of ____ and ____.
– Adaptable to growth and weight changes by remodeling.
– Able to self-repair.
• Functions:
– Protection for brain and internal organs.
– Attachment sites for muscles allowing movement of limbs.
– Defense against ____.
– Endocrine ____.
– Hearing.
connective tissue calcium phosphorus acidosis homeostasis
two types of bone: ____ > first deposited and is remodeled by clasts and blasts into a ____
two types of mature: ____ or ____
immature/woven/fibrous
mature/lamellar
cortical/compant
trabecular/cancellous
Bone Types: Compact Bone and Spongy Bone
- Compact Bone:
- Does not have spaces or hollows in the bone matrix that are visible to the eye.
- ____ and ____.
- Thick-walled the ____ of long bones.
- ____ of long bones.
- Spongy Bone (a.k.a. trabecular bone or cancellous bone):
- Delicate network of ____ which branch and intersect to form a sponge-like tissue.
- ____ contain mainly spongy bone.
- ____ but NOT ____.
lamellar
haversion
diaphysis
epiphyses
trabeculae
epiphyses
lamellar
haversion
Structure of a Flat Bone
• ____ and ____ surfaces of ____ bones are composed of compact bone.
• Middle layer is spongy bone and it is also called the ____.
• An impact to the skull may fracture the outer layer and crush the spongy bone, but not harm ____ compact bone or the underlying brain.
external internal flat diploe inner
Bone Components
• Cells – Osteoblast lineage: • Osteoprogenitor Cells • Osteoblasts • Osteocytes – Monocyte-macrophage lineage: • Osteoclasts
• ECM: – Organic (osteoid): –-- Fibers: Type \_\_\_\_ Collagen. –-- Ground substance: GAGs, PGs. – Mineral: –-- \_\_\_\_ (Ca10(PO4)6(OH)3)
I
hydroxyapatite
Bone Components
table: mineral component is ____ of total part of bone > of hydroxyapatite > ____%
OPC > blasts > cytes
monocyte (from bone marrow) > macrophage (involved with phagocytosis) > clasts (a type of ____, engulf the mineral and organic matrices of the bone)
big fraction
70
macrophage
Osteogenic Lineage
• Osteogenic Cells: • Found in the \_\_\_\_ and \_\_\_\_. • Arise from embryonic \_\_\_\_ cells. • Multiply \_\_\_\_ and differentiate into osteoblasts in response to stress or fractures.
- Osteoblasts:
- Produce an ECM of about ____% collagen fibers and ____% mineral (mostly calcium phosphate).
• Osteocytes:
• Osteoblasts that have completely surrounded
themselves with the extracellular matrix they produce.
ostoegenic are ____; capable of mitosis, continuously divide
osteocyte uncapable of further ____; differentiation stops
Spicules = ____, newly formed pieces of ____
endosteum
periosteum
mesenchymal
continuously
35
65
undifferentiated
cell division
isolated
bone
Bone Cells: Osteoblast
• Derived from ____.
• Epithelial-like ____ or ____ in monolayers at sites of active bone
formation.
• ____ cell: ECM released at the cell/bone interface.
• Synthesizes the organic matrix (osteoid)
and ____ mineralization of the matrix:
• Osteoid:
–• Type ____ collagen.
–• PGs.
• Non-collagenous ____.
osteoblast has features of actively secreting cell; big ____ and secretory vesicle and lots of ____; because it’s producing osteoid
osteoprogenitor cells cuboidal columnar polarized controls I proteins
ER
mitochondria
Bone Cells: Osteocyte
• Derived from \_\_\_\_. • Terminally \_\_\_\_: Incapable of cell division. • Highly branched cell with cytoplasmic extensions entering the \_\_\_\_ of the bone matrix. • Maintains the bone \_\_\_\_.
very ____ cell (biochemically, metabolically)
osteoblasts differentiated canaliculi ECM active
Osteogenic Cells: The Bone Mineral Matrix
• Inorganic (65%) – \_\_\_\_ (a form of calcium phosphate) • Organic (35%) – Type \_\_\_\_ Collagen – Non-collagenous proteins: • Osteocalcin, osteopontin, osteonectin • Bone sialoprotein • Growth factors, cytokines
– GAGs
• Chondroitin sulfate
• Keratan sulfate
• Hyaluronic acid
most of matrix of bone is mineral = ____
take a bone, and do not mineralize, you end up with an element similar to ____
if only mineral and no collagen > the bone becomes very ____, the bone would break easily and it is not resistant to impact/stresses
hydroxyapatite I hydroxyapatite cartilage brittle
Mineralization: Formation of the Bone Mineral Matrix
- Mineralization: precipitation of ____ and growth of crystals of ____.
- Calcium phosphate is extremely ____ and precipitates at high concentrations of calcium or phosphate ions.
- In non-mineralizing tissues, calcium phosphate precipitation is prevented by ____ (e.g. pyrophosphate).
• In mineralizing tissues (e.g. bone), pyrophosphate is destroyed by ____.
• Mineralization occurs in the ECM between ____ – requires ____:
1. Within the holes that separate the collagen molecules within the collagen fibrils.
2. Between adjacent collagen molecules within the fibril.
3. Space between adjacent fibrils.
calcium phosphate
hydroxyapatite
insoluble
crystal growth inhibitors
alkaline phosphatase
collagen fibrils
nucleators
Mineralization: Formation of the Bone Mineral Matrix
• Mineralization occurs in the ECM between collagen fibrils – requires nucleators:
- Within the holes that separate the collagen molecules within the collagen fibrils.
- Between adjacent collagen molecules within the fibril.
- Space between adjacent fibrils.
Molecular arrangement of collagen and hydroxyapatite crystals in compact bone.
(a) Collagen fibers overlap adjacent fibers as they repeat every ____ Å.
(b) Hydroxyapatite crystals
(Ca10[PO4]6[OH]2) are arranged in ____ within each fiber, resembling overlapping ____.
680
layers
bricks
Mineralization: Formation of the Bone Mineral Matrix
when collagen is mineralized, the fibers change in ____ and they get much ____
morphology
thicker
Osteoblast Biology: The Bone Mineral Matrix
Edge of matrix acts as ____; layers of matrix; osteoblasts produce matrix in ____; these layers are known as ____ bone; similar to growht rings of tree
nucleator
pulses
lamellar
Bone Cells: Osteoclast
• Derived from a pluripotent ____ stem cell (granulocyte/macrophage colony forming unit, GM- CFU).
- The monocyte progenitor cell may differentiate into either ____ or ____.
- Preosteoclasts travel directly through the marrow to the trabecular bone ____, or via the ____ to the cortical bone.
- Mature osteoclasts arise by fusion of ____ to form a ____ giant cell.
- Responsible for bone resorption associated with bone modeling, remodeling and pathology.
hematopoietic preosteoclast premonocyte surface vascular system preosteoclasts multinucleated
