3_Bones and Skeletal Tissue (ch 6) Flashcards
Marieb Chapter 6
What are the 7 functions of bones?
1) Support (for body and soft organs)
2) Protection (for brain, spinal cord, and vital organs)
3) Movement (levers for muscle action)
4) Mineral and growth factor storage (Calcium and phosphorus, and growth factors reservoir)
5) Blood cell formation (hematopoiesis) in red marrow cavities of certain bones
6) Triglyceride (fat) storage (yellow marrow)(Energy source)
7) Hormone production
(osteocalcin which regulates bone formation
Protects against obesity, glucose intolerance)
What hormone produced by bone regulates bone formation
and protects against obesity and glucose intolerance
Osteocalcin
What is hematopoiesis
Blood cell formation
Why are bones categorized as organs?
Because they contain different types of tissues
bone (osseous) tissue, nervous tissue, cartilage, fibrous connective tissue, muscle and epithelial cells in its blood vessels
How many levels of structure do bones have?
3:
Gross anatomy
Microscopic
Chemical
Name the two bone textures
Compact and spongy bone
What are the characteristics of compact bone?
Dense outer layer; smooth and solid
What are the characteristics of Spongy (cancellous or trabecular) bone?
Honeycomb of flat pieces of bone deep to compact called trabeculae
What is the structure of short, irregular and flat bones? (e.g. skull)
**Thin plates of spongy bone covered by compact bone
**Plates sandwiched between connective tissue membranes
**Periosteum (outer layer) and endosteum
**No shaft or epiphyses
**Bone marrow throughout spongy bone; no marrow cavity
**Hyaline cartilage covers articular surfaces
What is the structure of typical long bones? (e.g.humerus)
1) Diaphysis
*Tubular shaft forms long axis;
*Compact bone surrounds medullary cavity)
2) Epiphyses
*Bone ends
*External compact bone; internal spongy bone
*Articular cartilage covers articular surfaces
*Between is epiphyseal line
Remnant of childhood bone growth at epiphyseal plate
What membrane covers bones?
Periosteum
Where would you find periosteum membrane? and what are its characteristics?
*White, double-layered membrane
*Covers external surfaces except joint surfaces
*Outer fibrous layer of dense irregular connective tissue
Note: Sharpey’s fibers secure to bone matrix
*Osteogenic layer abuts bone
Note: Contains primitive stem cells – osteogenic cells
*Many nerve fibers and blood vessels
*Anchoring points for tendons and ligaments
Where would you find the endosperm membrane?
Delicate connective tissue membrane covering internal bone surface
Covers trabeculae of spongy bone
Lines canals that pass through compact bone
Contains osteogenic cells that can differentiate into other bone cells
What is red marrow?
Hematopoietic Tissue in Bones
Where is red marrow found?
*Found within trabecular cavities of spongy bone and diploë of flat bones (e.g., Sternum)
*In medullary cavities and spongy bone of newborns
*Adult long bones have little red marrow [Heads of femur and humerus only]
*Red marrow in diploë and some irregular bones is most active
*Yellow marrow can convert to red, if necessary
What five major cell types are found in bones?
Osteogenic cells
Osteoblasts
Osteocytes
Bone lining cells
Osteoclasts
What are osteogenic cells?
Also called osteoprogenitor cells - STEM CELLS
Mitotically active stem cells in periosteum and endosteum
When stimulated differentiate into osteoblasts or bone lining cells [some persist as osteogenic cells]
What are osteoblasts?
Matrix-synthesizing cell responsible for BONE GROWTH
Secrete unmineralized bone matrix or osteoid [Includes collagen and calcium-binding proteins][Collagen = 90% of bone protein]
Actively mitotic
What protein makes up 90% of bone protein?
collagen
What are Osteocytes?
MATURE bone cells in lacunae
Monitor and maintain bone matrix
Act as stress or strain sensors
Respond to and communicate mechanical stimuli to osteoblasts and osteoclasts (cells that destroy bone) so bone remodeling can occur
What are osteoclasts?
*cells that destroy bone
*Derived from hematopoietic stem cells that become macrophages
*Giant, multinucleate cells for bone resorption
*When active rest in resorption bay and have ruffled border
[Ruffled border increases surface area for enzyme degradation of bone and seals off area from surrounding matrix]
What are bone-lining cells?
Flat cells on bone surfaces believed to help maintain matrix
On external bone surface called periosteal cells
Lining internal surfaces called endosteal cells
What are the characteristics of Compact Bone?
*aka lamellar bone
*Osteon or haversian system
[Structural unit of compact bone]
*Elongated cylinder parallel to long axis of bone
*Hollow tubes of bone matrix called lamellae [Collagen fibers in adjacent rings run in different directions;
Withstands stress – resist twisting]
What is the structural unit of compact bone?
Osteon or haversian system
Note: Canals and canaliculi
Central (haversian) canal runs through core of osteon
Contains blood vessels and nerve fibers
Perforating (volkmann’s) canals
Canals lined with endosteum at right angles to central canal
Connect blood vessels and nerves of periosteum, medullary cavity, and central canal
Where do you find canaliculi in compact bone?
in compact bones; these hairlike canals connect lacunae to each other and central canal
What is ossification (osteogenesis)?
*Process of bone tissue formation
*Formation of bony skeleton
Begins in 2nd month of development
*Postnatal bone growth
until early adulthood
*Lifelong Bone remodeling and repair
How are canaliculi formed in compact bone?
Osteoblasts secreting bone matrix maintain contact with each other and osteocytes via cell projections with gap junctions
When matrix hardens and cells are trapped the canaliculi form
Allow communication
Permit nutrients and wastes to be relayed from one osteocyte to another throughout osteon
What are lamellae in compact bone?
**Interstitial lamellae
[Incomplete lamellae not part of complete osteon
Fill gaps between forming osteons
Remnants of osteons cut by bone remodeling]
**Circumferential lamellae
[Just deep to periosteum
Superficial to endosteum
Extend around entire surface of diaphysis
Resist twisting of long bone]
Name two types of lamellae in compact bone.
*Interstitial lamellae
*circumferential lamellae