Skeletomuscular System - Bone and Cartilage Flashcards
What is the skeletomuscular system?
System that connects the skeleton to muscles - the skeleton and muscles work together to support the body’s weight and allow it to move
What are the functions of the skeletal system?
- provide support
- protects tissues
- stores minerals
- forms blood cells
What type of tissue makes up the skeletal system?
Connective tissues
What are the three types of connective tissue structures that connect the skeletal and muscular systems?
Cartilage - supportive connective tissues
Tendons - dense regular connective tissue
Ligaments - dense regular connective tissue
What do cartilage and bone have in common?
SUPPORTIVE CONNECTIVE TISSUE WITH DENSE SOLID MATRICES
CARTILAGE: chondrocytes in lacunae
BONE: osteocytes in lacunae
CARTILAGE: chondroitin sulfate (in proteoglycan)
BONE: small volume of liquid surrounded by crystals of calcium salts (crystalline)
CARTILAGE: collagen, elastic, and reticular fibers in varying proportions
BONE: collagen fibers predominate
CARTILAGE: no internal blood vessels (avascular)
BONE: extensive blood vessels (extensive vasculature)
CARTILAGE: perichondrium covering (two layers)
BONE: periosteum covering (two layers)
CARTILAGE: limited strength; ends easily; but hard to break
BONE: strong; resists distortion until broken
What makes up bone tissue? What are some of its characteristics?
- supportive connective tissue
- collagen + calcified, hydroxyapatite matrix
- more rigid
- mineralized, crystalline matrices
- highly vascularized and innervated
What makes up cartilage? What are some of its characteristics?
- supportive connective tissue found at joint surfaces
- proteoglycan matrix (glyco-proteins which include chondroitin sulfates)
- more flexible
- avascular and contain chondrocytes residing in lacunae
What are the three subtypes of cartilage?
- Hyaline cartilage
- Elastic cartilage
- Fibrocartilage
- all avascular and contain chondrocytes residing in lacunae
What are the two subtypes of bone tissue?
- Compact
- Spongy
- represent a trade-off between weight and weight-bearing
What is hyaline cartilage?
- contains proteoglycans
- stiff somewhat firm support
ex) shoulder joint
What is elastic cartilage?
- proteoglycans + elastic fibres
- can distort without damage and return to original shape
ex) external ear
What is fibrocartilage?
- proteoglycans + lots of collagen
- extremely durable and tough
- matrix consists mostly of collagen and less ground substance
ex) knee joint
What is compact bone tissue?
A bone is typically hollow
- bone tissue that lines the outside of the bone
- dense (heavy) resists compression
- supports weight
What is spongy bone tissue?
A bone is typically hollow
- network that lines the internal cavity of the bone
- light, distributes force
- reduces weight
What are chondrocytes?
aka cartilage cells - found in chambers called lacunae
- responsible for production of collagen and extracellular matrix
- maintenance of cartilaginous tissues within joints
What are proteoglycans?
proteins present in the extracellular matrix of connective tissues (cartilage)
What is bone marrow?
- fills the cavities/inside spaces of bones
- NOT a type of supporting connective tissue
- creates blood cells (erythrocytes, etc.)
What are the four types of cells in bone tissue?
- osteogenic cells
- osteoblasts
- osteocytes
- osteoclasts
What are osteogenic cells?
- found in the periosteum for adults
- deep layers of the periosteum and the marrow (inner, cellular layer of the periosteum, and sometimes in the endosteum)
- stem cells that produce other bone cells
- play a role in bone repair and growth
- divide to produce daughter cells that differentiate into osteoblasts
- maintain populations of osteoblasts
What are osteoblasts?
- secrete collagen hydroxyapatite
- produce new bone matrix in a process called ossification/osteogenesis
- found along the bone surface
- immature cell
What are osteocytes?
- matured osteoblast/mature bone cell
- found between bone layers
- maintain bone matrix
- secrete chemicals that dissolve the adjacent matrix and release minerals into bloodstream (then they rebuild the matrix)
- located within lacunae surrounded by mineralized bone matrix
What are osteoclasts?
- breaks the bone / dissolves the bone
- remove bone matrix (osteolysis)
- found in the endosteum (inner)
- degrade bone to initiate normal bone remodeling
- play a role in bone growth
What do bone and cartilage have in common?
- both have solid matrices
- only bone has mineralized crystalline matrix
- both have cells capable of synthesizing matrix and matrix proteins
- both can sometimes be found within bones
What question should you ask yourself to differentiate cartilage from bone tissue?
How is the tissue formed and how does it grow?
Answering this question can help us determine if we are referring to bone tissue or cartilage!
What are the two ways that cartilage grows?
- Cell division - Interstitial growth
- chondrocyte proliferation - Differentiation - appositional growth
- differentiation into new chondrocytes
What is interstitial growth?
- chondrocyte proliferation
- growth by chondrocyte
- not possible after puberty
- chondrocyte undergoes division and the additional matrix secreted pushes the cells apart
- lay down more matrix in the existing matrix and this is what allows the cartilage to grow
What is appositional growth? (For cartilage)
- differentiation into new chondrocytes
- growth from the perichondral layer
- cells differentiate into chondroblasts
- chondroblasts secrete new matrix
- chondroblasts mature into chondrocytes
- produces new matrices and cartilage grows (?)
What are the two ways that bone can grow?
- Endochondrial growth
- Appositional growth
What is endochondral growth?
- starts with hyaline cartilage
- ossification begins in the shaft of the bone then to the epiphyses (ends)
- cartilaginous “epiphyseal plates” (hyaline cartilage tissue) at the ends grow by interstitial growth (allows the bone to grow in length) until ossification at puberty
- epiphyseal plates separate the epiphysis from the diaphysis
- but the ends of the bones remain as cartilage
- not possible after puberty
What is appositional growth? (For bone)
- does not have to start with cartilage
- osteogenic cells in the inner layer of the periosteum produce daughter cells that differentiate into osteoblasts and add bone matrix to the surface
- osteoblasts active at the periosteum produce more bone matrix
- osteoclasts active at the endosteum remove bone matrix
- diameter of a bone enlarges through appositional growth at the outer surface
- outside is growing wider, while the inside is being eaten away = diameter increases!
What are the two exceptions to bone growth?
- dermal and sesamoid bones ossify from non-cartilaginous connective tissue
- dermal bones found mostly in the head ossify from within dermal tissue
- sesamoid bones form within tendons
What are the three main differences between bones and teeth?
- hardness (chemical composition of crystalline matrix)
- growth (organization of cells compared to crystalline matrix)
- evolutionary history
What are the three layers of teeth?
- enamel
- dentin
- pulp
How do bones in the skeleton connect to each other?
bones in the skeleton connect to each other via joints (articulations) with differing tissues, producing diverse physical properties
What is a synovial joint? What is its function?
Synovial joints - ends of bones encased in smooth cartilage
- contain articular cartilage and bone tissue
What is articular cartilage?
a sub-type of hyaline cartilage
- reduce friction during movement at the joint
- even when pressure is applied across a joint, the smooth articular cartilages do not touch one another, because they are separated by a thin film of synovial fluid within the joint cavity
- similar to hyaline cartilage but it has no perichondrium and its matrix contains more water than other cartilages
- cannot repair itself at all
- lacks a perichondrium layer
- cannot undergo appositional growth
What is ossification?
process by which new bones are produced
Between cartilage and bone tissue, which one repairs itself better?
bone tissue repairs itself way better than cartilage
- this is due to the fact that cartilage is avascular and bone tissue is extensively vascular
- cartilage repair through appositional growth can occur into adulthood for fibrous and elastic cartilage, but interstitial growth no longer occurs after puberty
How does bone tissue repair itself?
bone tissue repairs itself well through a series of stages
- bone healing involves extra proliferation of cells which typically first differentiates in cartilage before bone
- cartilage -> spongy bone -> compact bone
- start by making new cartilage to hold the broken bone together
- making new chondrocytes (cartilage)
- after chondrocytes have established the matrix/spongy bone
- osteocytes come in and start ossifying it into compact bone
What are the stages of fracture repair for bones?
- fracture hematoma formation
- callus formation
- spongy bone formation
- compact bone formation
Why doesn’t cartilage repair itself well?
because it is avascular / lacks blood vessels
What are cauliflower ears?
CARTILAGE DOES NOT REPAIR ITSELF WELL
- consequence of appositional growth processes misfiring and producing dense connective tissue proper instead of elastic cartilage
- deformity caused by blunt force trauma to cartilage
What is osteoarthritis?
inflammation caused by friction between the joints
- degenerative disorder caused by damage to the articular cartilage
What is arthritis?
any disease that affects synovial joints and causes inflammation
How is osteoarthritis an example of an positive feedback loop?
- damage to articular cartilage increases friction at the synovial joint
- leads to inflammation
- more pressure on the remaining cartilage
- causes more damage
[BACK TO 1 AND REPEAT]
Why are bones are so much more vascularized, metabolically active, and capable of remodelling/repairing than cartilage?
Cartilage is thin, avascular, flexible and resistant to compressive forces.
Bone is highly vascularized, and its calcified matrix makes it very strong.
How are bones part of the homeostatic regulation of calcium and other minerals?
- bones act as resevoirs for minerals within the body
- stores minerals and releases them as needed
- balance between osteoblasts and osteoclasts activity helps maintain calcium homeostasis
NORMAL LEVELS Ca2+ LEVELS IN THE BLOOD
1. Intestines - calcium and phosphate ions are absorbed
2. Kidneys - calcium and phosphate ions are lost
3. Bone - osteoblasts make matrix/bone and osteoclasts break down matrix/bone (using up and releasing Ca2+)
How do cartilage and bone differ in their methods of growth/repair?
Bone growth generally proceeds by ossification of cartilage
They also differ in their capacity for repair
Bone heals well, while cartilage heals little (fibro- or elastic) or not at all (articular)
Describe the following in terms of tissue type and give examples of their roles:
Bones
Tendons
Ligaments
Cartilage
Bones - supportive connective tissue
- structural support, protects tissue, stores minerals, forms blood cells
Tendons - dense regular connective tissue
- anchors bones to muscles
Ligaments - dense regular connective tissue
- anchors bones to other bones
Cartilage - supportive connective tissue
- joint surfaces
Compare the matrix and diversity of distinct cell types in bone and cartilage
both bone and cartilage have firm, solid matrices
bone - crystalline hydroxyapatite matrix
cartilage - chondroitin sulfate matrix
Compare the different mechanisms of growth that occur in bones and in cartilaginous tissues, including how these processes alter following puberty
Bone tissues
- endochondrial growth = ossification of cartilage (NOT POSSIBLE AFTER PUBERTY)
- appositional growth = diameter of bone increases
Cartilaginous tissues
- cell division (interstitial growth) = involves growth in the chondrocytes (IS NOT POSSIBLE AFTER PUBERTY)
- differentiation (appositional growth) = involves cells differentiating into chondroblasts then chondrocytes in the perichondral layer
Describe the phases involved in bone repair and compare and contrast the capacity for repair in bone and cartilage
Bone - very capable of self repair
Cartilage - not good at self repair
- articular cartilage cannot repair itself at all
bone fractures repair in the four stages of fracture repair:
1. fracture hematoma formation
2. callus formation
3. spongy bone formation
4. compact bone formation
Explain the pathological processes occurring in osteoarthritis and analyze the potential costs and benefits of treating osteoarthritis with total joint replacement
inflammation caused by friction at the synovial joints causes damage to the articular cartilage - this cycle repeats
pros: less pain, bone stops degenerating (positive feedback loop has been broken), replacing one joint could protect another one
cons: difficult to adjust, body may reject, major surgeries aren’t ideal, surgery is a risk for developing infections, putting metal in your body makes you more prone to infections, don’t last forever, must get them replaced after a while, limits movements
Explain the role of bone as a mineral reservoir and predict how the activity of bone cells will respond to changes in body calcium levels
When calcium levels INCREASE, this will cause an INCREASE in OSTEOBLAST activity to use up the calcium in making bone matrix
When calcium levels DECREASE, this will cause an INCREASE in OSTEOCLAST activity to break down the bone matrix and release more calcium
What is the difference between periosteum and endosteum?
Periosteum is the sheath that lines the outside of the bone.
- superficial layer of compact bone that covers all bones
- fibrous outer layer and a cellular inner layer
Endosteum lines the inside of the bone where the bone marrow is.
- incomplete cellular layer that lines the medullary cavity
- lines the inner surfaces of the central canals
- simple flattened layer of osteogenic cells that covers the bone matrix
Differentiate interstitial growth vs appositional growth in cartilage
Appositional growth - cell growth that occurs on the periosteum
Interstitial growth - chondrocytes growing from within the cartilage
What is a fracture?
- a crack or break in a bone
- most fractures heal even after severe damage, provided that the blood supply and the cellular components of the endosteum and periosteum survive
- there are four steps in fracture repair
Fracture Repair: What occurs in fracture hematoma formation? (1)
- extensive bleeding occurs
- a large blood clot or fracture hematoma soon closes off and injured vessels and leaves a fibrous meshwork in the damaged area
Fracture Repair: What occurs in callus formation? (2)
- cells of the intact endosteum and periosteum undergo rapid cell division
- daughter cells migrate into the fracture zone
- internal callus (hard skin) forms as a network of spongy bone unites the inner edges of the fracture
- external callus of cartilage and bone encircles and stabilizes the outer edges of the fracture
Fracture Repair: What occurs in spongy bone formation? (3)
- osteoblasts replace the central cartilage of the external callus with spongy bone
- bone fragments and areas of dead bone closest to the break are removed and replaced
- ends of the fracture are not held firmly in place and can withstand normal stresses from muscle contractions
Fracture Repair: What occurs in compact bone formation? (4)
- swelling initially marks the location of the fracture
- region becomes remodeled by osteoblasts and osteoclasts
- little evidence of the fracture will remain
Describe the role of cartilage
supportive connective tissue
- joint surfaces
Describe the role of bone
supportive connective tissue
- structural support, protect tissues, stores minerals, forms blood cells
Describe the role of tendons
dense regular connective tissue
- anchors muscles to bones
Describe the role of ligaments
dense regular connective tissue
- anchors bones to other bones
