Unit 2 Lecture Flashcards
What are the levels of organization?
Chemical/molecular Cellular Tissue Organ Organ system Organism
What is the skeleton composed of?
It is all bones and the connective tissues which attach them to each other (cartilage, ligaments, joints, and more)
What are the bones?
They are each an organ
What do bones contain?
Contain osseous (connective) tissue, blood vessels, nerves, lymphatic vessels, cartilage, and connective tissue coverings
How many bones are in the Axial region?
80 bones
What are the main regions of the axial skeleton?
- Skull
- Associated bones
- Vertebral column
- Thorax
How many bones are in the Appendicular Skeleton?
126 bones
What are the main regions or the appendicular skeleton?
- Pectoral Girdles
- Upper Limb
- Pelvic Girdle
- Lower limb
How many total bones are in the adult skeleton?
206 bones
What does the 206 total adult bones not include in the skeleton?
Sutural bones because some people don’t have them
What are the 7 classifications of bones?
- Long
- Short
- Flat
- Irregular
- Sesamoid
- Sutural
- Pneumatized
Where can sutural bones be found?
They are found in patches on the skull
What is the rule of 2?
In the cranium there are two bones that are identical to each other. In the face there are two bones that have no identical pair.
What are the 6 functions of the skeletal system?
- Support
- Protection
- Mineral storage
- Triglyceride storage
- Red and white blood cell formation (hemopoiesis)
- Leverage (assistance in movement)
What are the bones’ primary function in a developing baby/fetus?
To make red and white blood cells
What are the size of short bones?
They are as tall as they are wide
What are the main functions of the endosteum and the periosteum?
They are important for bone growth and remodeling
What is the periosteum?
It is the outside layer of bone. Technically: Connective tissue membrane covering external surface of bone. continuous with tendons, connective tissue of joints.
How is the periosteum attached to bone?
Attached to bone matrix via perforating fibers
What are the two layers of the periosteum?
- Outer fibrous layer
2. Inner osteogenic layer
What is the endosteum?
The lining of the inner surfaces of bone including marrow cavity, trabecullae of spongy bone, canals of compact bone.
What type of cells does endosteum contain and what are their functions?
Contains osteogenic cells-important for bone growth and remodeling
What does “osteo” mean?
bone
Define osteology
The study of bone tissue
What two components does connective tissue break down into?
Extracellular matrix and cells
What two components make up extracellular matrix?
Ground substance and fibers
What cells are found in bones?
Osteogenic cells
Osteoblasts
Osteocytes
Osteoclasts
What are the components of the ground substance in bones?
Organic and inorganic components
What type of fibers can be found in bones?
Collagen fibers
What bone cells are important for bone remodeling?
Osteoblasts and osteoclasts
What is the osteogenic cell journey to become osteocyte?
Osteogenic cell develops into an osteoblast that forms bone matrix and the osteoblast then becomes an osteocyte that maintains bone tissue
What are osteogenic cells?
Stem cells that are formed from mesenchyme (embryonic connective tissue)
How do osteogenic cells become osteoblasts?
Osteogenic cells undergo mitosis then come daughter osteogenic cells. Differentiation then begins and osteoblasts come about
What are osteoblasts functions?
Cells that build bone; bone formation. They synthesize organic components of matrix. They also initiate calcification
How do osteoblasts initiate calcification?
They take calcium from blood and deposit it within matrix by exocytosis
What are osteogenic cells and osteoblasts? immature or mature?
Immature
What osteocytes?
Mature cells involved in maintenance of bone
What is one major physical characteristic of osteocytes?
They have dendrites
What are the functions of osteoclasts?
Break down bone (bone resorption). They release proteolytic enzymes and acids to degrade collagen and release minerals to blood.
What are osteoclasts derived from?
Derived from myeloid stem cells (not osteogenic cells) and bone
What are osteoclasts’ nickname
“Bone crumblers”
What is the definition of bone modeling (construction)?
The process by which bone is formed by osteoblasts without prior bone resorption.
- This happens during growth
- It results in change in bone size and shape
What is the definition of bone remodeling (reconstruction)?
Occurs when bone is first resorbed by osteoclasts and then formed in the same location by osteoblasts
-Happens throughout life
What is the overall goal of modeling and remodeling?
Achieve strength for loading and lightness for mobility
How is the goal of modeling and remodeling achieved?
1) Strategically deposit bone where it is needed
2) Remove bone from where it is not needed to avoid bulk
What is Goal of modeling and remodeling during growth?
To achieve the skeleton’s peak strength
What is the goal of modeling and remodeling during adulthood?
To maintain bone strength by removing damaged bone
What cell is in charge of detecting location and magnitude of damage?
Osteocytes
What cell is in charge of removing damage?
Osteoclasts
What cell is in charge of replacing old bone with new bone?
Osteoblasts
What are the five steps of bone remodeling?
1) Activation
2) Resorption
3) Reversal
4) Formation
5) Quiescence
What is bone remodeling step 1: activation?
Pre-osteoclasts are stimulated and differentiated under the influence of cytokines and growth factors into mature active osteoclasts
What is bone remodeling step 2: resorption?
Osteoclasts digest mineral matrix (old bones).
What is bone remodeling step 3: reversal?
End of resorption; recruitment of osteoblasts
What is bone remodeling step 4: formation?
Osteoblasts synthesize new bone matrix
What is bone remodeling step 5: quiescence?
Osteoblasts become resting bone lining cells on the newly formed bone surface
What are the three locations on osteoclasts?
Sealing zone
Ruffled border
Functional secretory domain
What is an example of a long bone?
Humerus
What is an example of a short bone?
Trapezoid, wrist bone
What is an example of a flat bone?
Sternum
What is an example of an irregular bone?
vertebra
What is an example of a sesamoid bone?
Patella
What is an example of a sutural bone?
The blotches of bone between the main cranial bones
What is an example of a pneumatized bone?
ethmoid
Describe flat bone anatomy
Made of compact bone and spongy bone in between the compact bone
Describe long bone anatomy
At both epiphysis’s (the ends of the bone) there is articular cartilage and spongy bone. At both metaphysis’s (the region after the epiphysis) there is more spongy bone. In the diaphysis there is compact bone with endosperm, periosteum, and medullary cavity with blood vessels in it.
What are the organic compounds that make up the bone extracellular matrix (ECM)?
-Ground substance
-Collagen fibers (type I)
Both come from osteoblasts
What is in the ground substance of the bone extracellular matrix?
- Glycosaminoglycans = GAGs
- Glycoproteins = polysaccharide + protein (chondroitin sulfate, hyaluronic acid, etc.)
- Negatively charged (i.e. they trap water)
What are some characteristics of the collagen fibers of the bone extracellular matrix?
- Fibrous protein arranged in helical form
- Very resistant to pulling forces
- Provides flexibility and a framework for deposition of calcium crystals
What is the hierarchical organization of collagen in bone
osteoblasts create tropocollagen that then makes up microfibril which are like plates. The microfibrils make up fibrils that are like large microfibrils. Fiber is then made from fibrils. The fiber then makes lamella the rings in the compact bone tissue. The lamella then make up an osteon (in compact bone only) and the osteons form all together to make compact bones which then makes an actual bone.
What are the inorganic components of bone extracellular matrix?
- Water
- Hydroxyapatite
What are some facts about water within the extracellular matrix?
- Attracted to ground substance
- Makes up 25% of the ECM
What are some components of the hydroxyapatite within the bone extracellular matrix?
-Calcium phosphate and calcium hydroxide, other minerals like calcium carbonate, and some ions: Mg2+, F-, K+
How are hydroxyapatite crystals formed in the bone ECM?
- Salts (hydroxyapatite) are deposited within collagen fibers
- As the hydroxyapatite condenses, other inorganic salts and ions precipitate in the matrix to fill in the spaces between fibers
What is the organization of minerals in the bone ECM?
- The collagen fiber contains mineralized fibrils
- The fibrils contain small mineral plates bound by helical non collagenous proteins (collagen cross links)
- The big osseous tissue fibers contain mineralized fibrils
What does collagen provide the Bone ECM?
Provides strength in flexibility and resistance to tension
What do minerals provide the Bone ECM?
Provide strength in firmness (resistance to compression)
What happens to bones in a weak acid like vinegar?
Removes minerals so it becomes rubbery
What happens to bones when proteolytic enzymes are applied to it?
Removes collagen so it becomes brittle
What is rickets?
Inorganic component deficient. Calcium deficiency due to lack of vitamin D leads to flexible bones (bowed legs)
What is scurvy?
Organic component deficient. Problem with collagen synthesis due to vitamin C deficiency leads to brittle bones that can fracture easily
T or F: Spongy bone and compact bones have different chemical composition?
False: They both have the same chemical composition just different 3D organization
What is Spongy bones organization like?
- Irregular lattice of thin plates called trabeculae
- Osteocytes housed in lacunae
Where is spongy bone found?
- Epiphyses of long bones
- Surrounding marrow cavities
- Flat, short, irregular bones
What are spongy bone’s functions?
- Withstands forces from many directions - trabecular arranged along lines of stress
- Lightens the skeleton (not as strong as compact bone)
- Contains red marrow for hemopoiesis
How is compact bone organized?
Solid network of bone organized in concentric ring structures called osteons
What is the location of compact bone?
- External layer of all bones
- Diaphysis of long bones
What is the function of compact bone?
Gives long bones ability to withstand forces along longitudinal axis
What are the main components of an osteon?
Lamella Osteocytes lacuna Canaliculus Central canal
What are the main components of a trabeculae?
Lacuna Lamella Canaliculi Osteocyte Osteoclasts Osteoblasts aligned along trabeculae of new bone
What is the main physical difference between osteons and trabeculae?
Osteons are circular and trabeculae are ovular with osteoclasts and osteoblasts.
