Unit 1 Flashcards
Is bone tissue alive?
yes, bone tissue is dynamic, a living tissue with cells
What is cartilage used for?
-component for embryonic, growing, and mature bones
-important for bone development
- connects bones in some areas (ribs and hip bones)
- at the end of bones for protection
What kind of cartilage is at the end of bones?
articular hyaline cartilage
What are the types of cartilage?
-hyaline
-fibrous/elastic
Where is hyaline cartilage found?
-end of bones( articular hyaline)
- epiphysial plate
What is fibrous cartilage?
stretchy cartilage
Where is fibrous cartilage found?
in between vertebrae
nose and ears
What are the types of connective tissue
ligaments and tendons
What is connective tissue?
bone and ligament outer membrane
What are tendons?
connective tissue that connects muscle to bone
What are ligaments?
connective tissue that connects bone to bone
Does cartilage absorb water?
yes this helps in protect and cushion the bones
What are the types of bones?
-long
-short
-flat
-irregular
What is an example of a long bone?
femur or humerous
What is an example of a short bone?
tarsals
What is an example of a flat bone?
frontal bone
What is an example of an irregular bone?
vertebrae
What is a long bone?
a bone that is longer than it is wide
What is a short bone?
a bone where length is equal to width
What is an irregular bone?
a bone that is a complex or elaborate shape
What is a flat bone?
a bone with a flat smooth surface, sometimes is curved
What do all bones have?
compact and spongey bone
what is compact bone?
-white, smooth, solid bone on the outside of bones
- dense or cortical bone
What makes up compact bone?
osteons and lamellae
Where is compact bone found?
-on the exterior of the bone
What percentage of bone is compact bone?
20% of the bone overall, but 80% of the bone weight
What is spongey bone?
-cancellous/ trabecular bone
- appears porous
Where is spongey bone found?
-internal to compact bone
What makes up spongey bone?
-trabeculae
space between trabeculae contains red bone marrow
What makes up the extracellular matrix?
Organic and Inorganic tissues
What are the organic tissues that make up the extracellular matrix
-osteoid produced by osteoblasts
-a ground substance containing mostly collagen, proteoglycans, and glycoproteins
What is needed for collagen formation?
vitamin C
How is organic matter organized?
-in a uniform/organized pattern
What does organic matter do for the bone?
-contributes to flexibility
- gives in tensile strength by resisting stretching
How much of the bone matrix is organic
1/3
How much of the bone matrix is inorganic
2/3
How are osteoid produced?
by osteoblasts
What is the inorganic bone matrix made of?
mineralized crystals (mostly Ca10, PO4. Oh, hydroxyapatite are deposited around collagen fibers resulting in mineralization/ calcification of bone
What does vitamin D help with?
propper Ca2+ reabsorbtion
What does the mineralization of inorganic tissue do for bone?
accounts for the relative rigidity
How is the bone matrix organized?
1st. Collagen is laid down parallel and everything else is laid down after
2. Osteoid (more organic compound) is laid down
3. Proteoglycans and glycoproteins are laid down between the collagen and mineralization occurs
4. hydroxyapatite crystals are laid down between the parallel collagen fibers
What are the skeletal system functions?
- Mobility and movement
- support and protections
-hemopoietic - storage
How does the skeletal system help with mobility and movement?
-bones form lever system that act as attachment sites for skeletal system
How does the skeletal system help with support and protection?
-Bones provide a structural framework and protect delicate tissues
- can build bones when growing
- can take bones away (pregnant mothers)
How does the skeletal system help with hemopoiesis?
- formed elements developed in red bone marrow (RBCs WBCs , platelets)
- yellow bone marrow= fatty
How does the skeletal system help with storage?
-mineral storage (99% of body’s Ca2+ phosphate is in bones)
- liquid storage ( adipose tissue is stored in yellow bone marrow)
- bones are mostly calcium phosphate
What does Calcium do?
-muscle contraction
-blood clotting
-neurons firing
-tooth enamel
What does phosphate do?
ATP and Energy
What are the types of bone cells in the order of formation?
-osteoprogenitor cells
-osteoblasts
- osteocytes
- osteoclasts
What are osteoprogenitor cells
-Bone cells derived from stem cells
-differentiate into osteoblasts
What are osteoblasts and what do they do?
-Blast are the builders
- Synthesize and secrete osteoid
- Regulate osteoclast differentiation and activity
-more cuboidal
-We activate them more when we want to build more bone
- When mineralized it gets trapped and turns into an osteocyte
What is osteoid?
-organic portion of tissue matrix
largely collagen
- synthesized secreted from osteoblasts
When do we activate more osteoblasts?
when we want to build more bone
What are osteocytes and what do they do?
- mature cell enveloped by calcium osteoid
- maintains matrix and responds to stress by activating osteoblasts and osteoclast activity
- Extensions allow communication with other osteocytes through gap junctions
-still strapped in the matrix, doesn’t add to it, but maintains it through communication
What are osteoclasts and what do they do?
-nucleated phagocytic cells formed by the fusion of bone marrow
- digests and dissolves bone matrix through reabsorption into blood
- raises blood calcium levels and releases minerals
-Proteolytic enzymes break down organic material
- HCL dissolves inorganic material
- inhibited by estrogen, so when estrogen drops during menopause bones break down more
What are external circumferential lamellae?
-rings of compact bone that surround the entire outer compact bone surface
-not too thick bc you have to be able to get blood vessels through
Where are external circumferential lamellae found?
immediately internal to the bone periosteum
What are interstitial lamellae?
compact bone remains of a partially reabsorbed osteon
-evidence that bone tissue is constantly regenerating
Where are interstitial lamellae found?
found between the newer, complete osteons
What is evidence that bone tissue is constantly regenerating?
interstitial circumferential lamellae
What is an osteon?
functional unit of compact bone inside of concentric lamellae and the central canal
What are internal circumferential lamellae?
-rings of compact bone that line the inner edge of compact bone tissue
Where are internal circumferential lamellae found?
-found adjacent to the endosteum
Why are compact bones organized the way they are?
-helps blood supply and nutrients be evenly dispersed
- Having the internal circumferential lamellae and external circumferential lamellae means bones can be repaired from inside or outside
What is the periosteum?
- double layer bone covering adjacent to compact bone
- connected to compact bone through perforating fibers
-The outer fibrous layer is composed of connective tissue - The inner cellular layer contains osteoprogenitor cells, osteoblasts and osteoclasts
What is the outer fibrous layer of the periosteum made of?
connective tissue
What is the inner cellular layer of the periosteum made of?
osteoprogenitor cells
osteoblasts
osteoclasts
What is the central canal?
carries blood vessels and nerves through the center of each individual osteon
What is the perforating canal
opening in the bone where vessels and nerves through compact bone, interconnecting the central canal of osteons
What is the nutrient foramen?
- openings in bone where vessels and nerves exit and enter
What is the osteon’s structure?
-Each osteon has multiple layers of concentric lamellae surrounding the central canal
- Each lamellae is then composed of inorganic crystals between collagen fibers
-within the concentric lamellae each collagen fiber is parallel (collagen fibers are 90degrees away from collagen fibers in adjacent lamellae)
What are osteocytes and what do they do?
- Osteoblasts surrounded by mineralized bone matrix develop into osteocytes
- Cellular processes extend from the osteocyte cell body through thin small spaces called canaliculi
- allows cells to communicate with each other where the processes meet through gap junctions
- the innermost layer of osteocytes extends cellular processes to the central canal blood supply allowing for the exchange of nutrients, wastes, and respiratory gases
Where are osteocytes found?
- in small spaces called lacunae, located btwn adjacent concentric lamella
What are lacuna?
spaces that house osteocytes
What are canaliculi?
- thin small spaces housing cellular processes
How to osteocytes communicate?
- connect to other neighboring adjacent concentric lamellae through gap junctions found at their cellular processes
How do osteocytes respond to stress?
monitor stress and respond by stimulating osteoblasts, initiating bone deposition.
What are trabeculae
an open lattice of narrow rods and plates of bones in spongy bone
What are trabeculae comparable to in compact bone?
osteons
Where is spongy bone found?
various places dependent on shape of bone
What are trabeculae made of?
- parallel lamellae
Why are trabeculae made of parallel lamellae?
makes it thinner so diffusion of nutrients are easier
What is in the spaces between trabeculae?
bone marrow and blood vessels
Where does spongy bone get its nutrients?
outside (explaining why diffusion is so important)
Where does compact bone get its nutrients?
- central canal
Does compact bone have a periosteum?
yes
Does spongy bone have a periosteum?
no
Does spongy bone or compact bone have concentric lamellae?
compact bone
Does spongy or compact bone have parallel lamellae?
spongy
What type of bone has its own anatomy?
long bone
What are flat, irregular, and short bones composed of?
- central bone shaft that provides leverage and support
- exterior that has thick layer of compact bone covered by periosteum
- interior made of spongey bone
- no medullary cavity
- has bone marrow in spongy bone
-endosteum lines trabecullae of spongy bone
What covers the outer surface of trabeculae in spongy bone?
incomplete endosteum
What makes the outer surface of spongy bone?
incomplete endosteum
Do flat, irregular, and short bones have compact and spongy bone?
yes
What is dipole in flat bones?
- interior made of spongy bones
What type of bone has a dipole?
flat bones
Does short, flat, and irregular bone have a medullary cavity?
no
What is a long bone made of?
-diaphysis
-epiphysis
-metaphysis
-periosteum
-endosteum
What is the diaphysis?
-part of the long bone
-central bone shaft that provides leverage and support
-
What is the medullary cavity made of?
- exterior made of thick compact bone with thin spicules of spongy bone extending inwards
-all exterior areas covered with periosteum
-medullary cavity containing blood vessels and bone marrow?
Where in the long bone are blood vessels and bone marrow?
medullary cavity
What is red bone marrow?
- myeloid tissue that is hemopoietic tissue containing highly active stem cells for the formed elements of blood
Where is red bone marrow located?
- at first all bone marrow is red and then slowly converted to yellow as we age.
- in adults is only in regions of the axial skeleton and a few areas of the appendicular skeleton
What is yellow bone marrow made of?
adipose tissue
What is unique about yellow bone marrow?
- retains the potential to convert back into red bone marrow under stress
- like severe anemia
How many epiphysis’ are there in a long bone?
-proximal and distal
What is the epiphysis?
- enlarges surface ends “knobs” composed of a thin outer compact bone layer surrounding inner bone marrow filled spongy bone
What is at the end of the epiphysis?
-articular cartilage
Where is articular cartilage found?
at the end of the epiphysis
What is articular cartilage?
- protective hyaline cartilage layer found on some bone ends such as where joints occur
-reduces friction and absorbs shock in moveable joints
What is the metaphysis?
- the region that widens and transfers weight between the diaphysis and epiphysis
- once growth ceases bone tissue replaces all of the cartilage and epiphyseal line (composed of a thin line of compact bone) remains
What does the metaphysis contain?
- cartilage containing the epiphyseal plate, or growth plate, responsible for lengthwise growth in bones
What is the periosteum?
- a double layer sheath that covers the outside of bones
What does the periosteum do?
- protects bone from surrounding structures
-anchors blood vessels and nerves - acts as attachment site for ligaments and tendons
Where is the periosteum not found?
- patella and joint surface of long bones covered by articular cartilage
What are the parts of the periosteum?
-outer fibrous layer
-inner cellular layer
- perforating fibers
What does the outer fibrous layer of the periosteum do?
-anchors blood vessels (nutrient foramen) and nerves to bone surface
- attachment site for ligaments and tendons
What does the inner cellular layer of the periosteum contain?
osteoprogenator cells
osteoclasts
osteoblasts
What are the perforating fibers of the periosteum?
tuffs of collagen that fuse the periosteum to the outer compact bone layer
What is the endosteum of the long bone?
- an incomplete cellular layer containing osteoprogenitor cells, osteoblasts, and osteoclasts
- lines canals of compact bone
-covers medullary cavity of long bone - covers spongy bone tissue
Where is endosteum found?
- lines canals in compact bones
- covers spongy bone tissue
- lines medullary cavity of long bone
Where is the extracellular matrix found?
cartilage and bones
What is the bone equivalent of agricans?
hydroxyapatite crystals
What is the bone equivalent of chondroblasts
osteoblasts
Is cartilage calficied?
no
What is the bone equivalent of chondrocytes?
osteocytes
What is the cartilage equivalent of osteoclasts?
none- they cant destroy themselves
What is the bone equivalent of mesenchymal stem cells?
osteoprogenitor cells
Does bone or cartilage have a bigger lacuna?
cartilage
Why does cartilage have a bigger lacuna?
- it fits the whole cell including chondroblasts and chondrocytes
- bone lacuna only has osteocytes and the processes stick out into canaliculi
Can cells go back through mitosis in cartilage?
yes
Can cells go back through mitosis in bone
no
Is cartilage vascularized?
no
Is bone vascularized?
yes
Does cartilage have processes?
no
Does cartilage have organized layers?
no, no separation of space
Does bone have organized layers?
yes, highly organized
What is the extracellular matrix of cartilage?
- avascular mature tissue
- a gel-like protein matrix that includes aggrecan, a proteoglycan
What are proteoglycans?
water absorbing sugars giving cartilage the gel-like matrix, elasticity, helps with diffusion
What are the types of cartilage tissue cells?
- mesenchymal stem cells
- chondrocytes
- chondroblasts
What is the perichondrium?
- dense irregular connective tissue made of mostly collagen fibers that cover the cartilage surface
-most of the region has fibroblasts, the deepest layer has mesenchymal stem cells
What are mesenchymal stem cells?
- only found in deepest layer of perichondrium
-divides and forms chondroblasts
What are chondrocytes?
- maintains cartilage matrix
- found in individual lacunae
- forms chondroblasts and may create more chondroblasts
Whats the difference when looking at chondrocytes and chondroblasts?
-1 nucleus in lacuna = chondrocyte
- 2 nucleus in lacuna= chondroblast
Where are chondrocytes found?
individual lacunae
What are chondroblasts and what do they do?
- produces cartilage matrix
-matures into chondrocytes
-found in shared lacuna
Where does appositional growth occur?
- at the perichondrium (outside of tissue)
What does appositional growth do?
increases width
Where does the perichondrium surround cartilage?
costal cartilage, between spinal vertebrae, nose
How does appositional growth occur?
- Meiotic activity happens in mesenchymal stem cells within the deepest layers of perichondrium
- forms chondroblasts
- Chondroblasts secrete cartilage matrix, pushing each other further apart
- Hence why it adds
- chondroblasts mature into chondrocytes
Where and when does interstitial growth occur?
- occurs when internal chondrocytes divide
- occurs at epiphyseal plate
What does interstitial growth do?
- increases length
How does interstitial growth occur?
- A chondrocyte in the lacuna starts showing
- Chondrocyte cellular division forms 2 new chondroblasts in 1 lacuna
-each cell produces a new cartilage matrix and starts separating from its neighbor - previously secreted matrix matures, further separating individual cells in there own lacunae
When does skeletal development start?
8 weeks
How many bones do you start with and then end up with?
starts with 300 and ends with 206 because the bones fuse together
What does skeletal development start with?
-mesenchyme tissue
- startic material for all skeletal structures?
What are the two ways ossification can occur?
intramembranous or endochondral
What is intramembranous ossification?
when vascularized mesenchymal membrane becomes ossified
What bones does intramembranous ossification create?
- flat bones of the skull, some facial bones, mandible, central part of the clavicle
- doesn’t have growth plates
What are the steps to intramembranous ossification?
- Ossification centers form within thickened regions of the mesenchyme
- Osteoid undergoes calcification forming the ossification center
- Woven bone (primary bone) and bone membranes begin to form
- Lamellar bone (secondary bone) forms
How do ossification centers form within thickened regions of the mesenchyme?
mesenchyme cells become osteoprogenitor cells which differentiate into osteoblasts which secrete osteoid
How does osteoid undergo calcification and form the ossification center?
- calcification of matrix causes osteoblasts to become osteocytes
- Osteoblasts remain at the periphery continuing to deposit osteoid and allow for expansion of the bone deposition
What is woven bone?
newly formed bone
Describe woven bone
-newly formed bone
- poorly organized
-weaker
Does woven bone have lamellae?
no
How do woven bone and bone membranes begin do form?
- mesenchyme tissue condenses and forms the membranes
- when it condenses it form the periosteum
-endosteum begins to form - blood vessels move through space.
What does lamellar bone do?
replaces woven bone
What are the types of lamellar bone?
lamellar compact and lamellar spongy
When are the endosteum and periosteum fully developed?
in lamellar bone
What is endochondral ossification?
- when hyaline cartilage model becomes ossified
What does endochondral ossification produce?
most bones of the skeleton including long bones (upper and lower limbs, pelvis, vertebrae, ends of clavicle
What are the steps of endochondral ossification?
- Fetal hyaline cartilage develops and perichondrium forms
- Periosteal bone collar forms
- Primary ossification center forms
- Secondary ossification centers form in epiphysis
Hoe does fetal cartilage develop and the perichondrium form?
- perichondrium turns into periosteum
How does the periosteal bone collar form?
- nutrient foramen starts to develop and interior cartilage breaks down due to mineralization
What is the bone collar?
when it starts going from perichondrium to periosteum
How does the primary ossification center in endochondral ossification form?
- Periosteal bud blood vessels enter diaphysis
- cartilage in diaphysis ossifies and bone development extends in both directions toward epiphysis as bone replaces degenerating cartilage
How
How do the secondary ossification centers form?
- cartilage in epiphysis calcifies, and chondrocytes die
- Blood vessels enter carrying osteoprogenitor cells which become osteoblasts
- the woven bone in the diaphysis interior is removed by osteoclasts forming the medullary cavity
Where does lengthwise growth occur?
- at epiphyseal plate until bone is fully grown
What are epiphyseal growth plates?
-plates where cartilage is instead of bone
Can there by multiple epiphyseal growth plates on one bone?
yes
Do all epiphyseal plates fuse at the same time?
no, they fuse progressively depending on regions, gender affects when these close
Do males or females have their growth plates close sooner?
females
How can we use growth plates in forensics?
to determine age of death
What type of growth occurs from the epiphysis to the diaphysis?
-interstitial/endochondral
What are the Zones of bone growth?
- resting cartilage
-zone of proliferation
-zone of hypertrophy
-zone of calcification - zone of ossification
What is the resting cartilage zone?
- mature cartilage that secures epiphysis to epiphyseal plate
What happens in the zone of proliferation?
- chondrocytes undergo rapid mitotic division producing longitudinal columns of parallel flattened bone
What happens in the zone of hypertrophy?
- chondrocytes cease to divide and begin to hypertrophy
-walls of lacunae thin
What happens in the zone of Ossification?
- Lacunae cells break down capillaries and osteoprogenitor cells enter as new bone matrix deposited on the calcified cartilage matrix
- sex hormones play a role in allowing this to happen
Which zones of bone growth are cartilage?
- resting cartilage
- hypertrophy
-calcification
-proliferation
What happens in the zone of calcification?
- minerals deposited between lacunae killing chondrocytes
What is bone deposition?
adding bone tissue
What is bone resorbtion?
taking away bone tissue
Where does bone deposition and resorption occur?
- periosteum
-endosteum in compact bone and spongy bone trabeculae
Why does deposition occur?
- remodeling
- bone growth
- bone repair
Why does resorption occur?
- remodeling or Calcium needs
What helps with bone deposition?
osteoblasts that secrete osteoid
What helps with bone reasoprtion?
- osteoclasts
- proteolytic enzymes fo for organic matrix
- HCL goes for inorganic matrix
How does TH regulate bone growth?
- needed for proper development of GH which is needed for skeletal muscular growth
-The hypothalamus releases TRH which stimulates the pituitary gland to release TSH (directly stimulating bone growth and indirectly stimulating the secretion of TH)
-needed during skeletal development for recruitment and maturation of cartilage and bone cells
-especially important during childhood for promoting synthesis of bone matrix by increasing metabolic rate of bone cells
What does the hypothalamus release?
TRH
What does the pituitary gland release?
TSH
GH
What does GH do for bone growth?
-plays a bigger role in childhood
- released by the pituitary gland stimulating the production of IGF in the liver
- GH and IGF work synergistically so 1+1=3
- has a really strong effect on cartilage within the epiphyseal plate region, stimulating the elongation of the long bone
What do sex hormones do during bone growth?
- Hormone levels increase dramatically during puberty which has a large impact on an epiphyseal plate by stimulating bone and cartilage cells
- The bone rate of growth is greater than cartilage growth causing the closure of the epiphyseal plate and formation of the epiphyseal line
- Postmenopausal women don’t produce significant amounts of estrogen leading to a risk of osteoporosis
What are gluccocorticoids?
-steroid hormones released from the adrenal gland that regulate blood glucose levels
What do glucocorticoids do for bone growth?
-High levels cause increased bone loss and impair growth of the epiphyseal plate
-can be prescribed as anti-inflammatory medications (asthma) so patients must be monitored because it could potentially negatively impact child bone growth
What does calcitrol do?
-stimulates the absorbtion of calcium from the small intestine into the blood
Where does calcitriol form?
- in kidney
What does PTH do for Calcitrol?
- Calcitriol forms more regularly in the presence in PTH
- Calcitriol and PTH work synergistically to increase blood calcium levels
What is the calcitriol formation cycle?
- precursor is converted to vitamin D3
- which is then converted to calcidiol in the liver when an oh group is added
- Calcidiol goes to calictrol in the kidney when another OH is added
How is calcitonin released?
- Blood calcium levels rise then calcitonin is released by the thyroid
-specifically during exercise
What happens if blood calcium levels are too high?
- intestines and kidneys decrease the resorbtion of calcium since we already have too much
- this inhibits osteoclast activity and stimulates osteoblast activity
What does PTH do?
- ## enhances production of calcitriol with hormones working together to increase blood Calcium levels
When is PTH released?
- In response to decreased blood calcium levels, stimulates bone reabsorption, resulting in an increase in blood calcium levels
- stimulates osteoclast proliferation and reabsorption of bone by osteoclasts
- promotes reabsorbtion of Ca2+
-indirectly increases Ca2+ absorption by the small intestine
What is wolfe’s law?
- Hormones affect skeletal system but then bones respond to mechanical stress put upon them by strengthening so they can support that stress
-shows how bones adapt to their environment?
What are stresses placed on bone?
-gravitational forces
-skeletal contraction; muscles and body weight pull on bone
How does the bone respond to mechanical stress?
- Stress is detected by osteocytes which communicate to osteoblasts and trigger an increased synthesis of osteoid which adds bone strength
- Osteoblasts lay down more osteocytes
what does the removal of stress do to bone?
- reduces collagen formation and causes demineralization and reduces some bone mass
- immobilization (cast) or microgravity environment (space) can cause this
What are the types of bone breaks?
- complete fracture
- stress fracture
- compound fracture
- pathological fracture
What is a complete fracture?
bone is completely separated due to break
What is a stress fracture?
- thin break caused by repetitive actions
What is a compound fracture?
1 or more region of the bone is sticking out
- more susceptible to infections
- will need surgical alignment
What is a pathological fracture?
- break in bones that were already weakened by disease
What population group has fractures heal the fastest?
kids
What are the steps to bone healing?
- a hematoma forms from broken blood vessels
- A fibrocartilaginous (soft) callus forms as collagen fibers (fibroblasts) and dense connective tissue from chondroblasts aggregate
-basically the body’s way of doing an internal splint
- all about alignment - a hard callus (Bony) callus formas as adjactent osteoblasts produce bone tissue
- remodeling
When does bone density peak?
30
When does most bone deposition occur?
in childhood
Which type of bone is more susceptible to aging?
- spongy bones
-so vertebrae, mandible, epipysis - causes height, tooth loss and fragile limbs
What is aging’s impact on bone compostition?
- reduced tensile strength due to a decrease in osteoblast activity and protein production
- alters ratio of organic and inorganic resulting in brittle bones with increased fracture risk
-increased demineralization resulting in insufficient ossification and thinner, weaker bones (ostepenia)
What is osteopenia?
- demineralization resulting in insufficient ossification and thinner weaker bones
Is osteopenia normal?
yea
