Skeletal System Flashcards
Specialized CT include _______.
Bone, Cartilage, Blood
Bone is a type of _____________.
Connective tissue
Connective tissue is made of ________
Cells, ECM (Ground Substance + Collagen fibers)
Cartilage is a type of ___________. What are its functions?
Specialized Connective tissue
- Embryonic skeleton (bone growth), airways are held open
- Shock absorption, resisting compression via intervertebral discs, menisci,
- Smooth gliding surfaces as articular surfaces of bones within joints.
_________ has a disc made of _________.
Dental Application
TMJ has a disc made of cartilage
What are the three types of cartilage?
Which one is most abundant?
Hyaline Cartilage - Most Abundant
Fibrocartilage
Elastic Cartilage
Where can hyaline cartilage be found?
Pubic Symphysis
Articular cartilage of joint
Meniscus
Costal (Rib)
Nose
Where can fibrocartilage be found?
Intevertebral discs, near knee joints
Where can elastic cartilage be found?
External ear, epiglottis
Bones have a ______ precursor.
cartilage
What is responsible for the synthesis of cartilage-specific ECM-components?
Chondrocytes
What are chondroblasts?
ChondroCYTE precursors capable of forming cartilage specific ECM material not yet encased within the matrix
(They transition to chondrocytes)
What structures do you expect to be abundant in cells that produce lots of proteins?
RER- Collagen
Golgi Body- Proteoglycans
What is the ECM of cartilage made of?
Type II collagen
Proteoglycans
Chondrocytes originate from _________ which can give rise to _________.
What is required for the expression of __________ to differentiate from _______ progenitor cells to chondrocytes.
mesenchymal stem cells, osteoblasts, myoblasts, adipocytes
Type II, mesenchymal
Sox9!
What is Sox9?
A transcription factor required to activate the differentiation of mesenchymal stem cells to chondrocytes.
What can mesenchymal stem cells make?
Chondrocytes
Osteoblasts
Myoblasts
Adipocytes
Fibroblasts
Cartilage ECM components are _________ and _________
- Ground substance containing large proteoglycan aggregates (Aggrecan) in a hyaluronic acid core that interact with collagen
- Glycosaminoglycans which are negatively-charged chains on proteoglycans that bind water.
What do GAGs contain that make then _______-charged?
negatively
Chondroitin sulfate and keratin sulfate
What is the purpose of the ECM of cartilage
Create shock absorber due to stiffness and elasticity
Describe the arrangement of the cartilage ECM
Network of Type II collagen fibril is interwoven with a long hyaluronic acid chain with several proteoglycan aggregates that interact with the collagen.
GAGs are located on the collagen fibril that contain chondroitin sulfate and keratin sulfate.
Why is it important that GAGs bind ______?
Water allows diffusion of things through the cartilage matrix
How does cartilage get its nutrients and oxygen?
Cartilage is AVASCULAR so it nutrients and oxygen must diffuse through the ECM.
This limits cartilage growth and repair.
Chondrocytes have a ______ metabolic rate and do not require __________ to perform.
low, high oxygen
What is perichondrium?
A sheath of DCT surrounding most cartilage.
It contains vasculature, nerves and lympathic vessels
From the outer to inner layer approaching the matrix, what is the perichondrium made of?
Outer layer: Fibroblasts will differentiate into chondroblasts and also provide the vasculature
Inner Layer: Chondroblasts
How does a perichondrium appear on a histological section?
A thick pink layer with a few cells. There is NO clear border but will end close to where there is an abundance of cells laying down the matrix.
What are fibroblasts?
Cells that can differentiate into chondroblasts and osteoblasts as well as produce collagen ECM.
Growth and cartilage is attributed to two processes. What are they?
The first is appositional growth. This is where cells differentiate from the perichondrium to become chondroblast cells. This is the most common way that cartilage increases girth postnatally.
The second is interstitial growth within the ECM. This is the mitotic division of pre-existing chondrocytes.
Where does interstitial growth occur?
Epiphyseal plate for increasing longbone length, articular cartilage regeneration because it lacks a perichondrium.
KNOW FOR EXAM
__________ cartilage lacks a perichondrium.
Articular and Fibrocartilage
Hyaline cartilage is the most common. True or false?
True
Where is hyaline cartilage found?
What fibers are found in it?
What is its growth pattern?
Pubic Symphysis
Costal (ribs)
Nose
Joints of knees
Growth Plates
Walls of large respiratory passages
Type II Fiber
Interstitial and appositional
What does the cartilage matrix look like on a histological sample?
Large mass of purple cells (basophilic)
Chondrocytes sit in _______ in the ECM.
Lacunae
Articular cartilage is a form of ________.
Hyaline Cartilage
Where is articular cartilage found?
Articular surfaces of bones
Articular cartilage lacks a _________. How does it replace the function of this structure?
Perichondrium
It diffuses oxygen and nutrients from synovial fluid.
Where is elastic cartilage found?
What fibers are found in it?
What is its growth pattern?
Ear, Walls of auditory canals, Epiflottis, Eustachian tubes
Elastic fibers and Type II collagen
Appositional and Interstitial
How does elastic cartilage stain?
Elastin fibers will stain as thin wispy lines. It will be BLUE
Chondrocytes will exist
Where is fibrocartilage found?
What fibers are found in it?
What is its growth pattern?
Intervertebral discs, attachments of certain ligaments, pubic symphysis, menisci, TMJ!!
Type I collagen and small amounts of Type II collagen
Interstitial
How does fibrocartilage stain?
Fibrocartilage is an intermediate between DCT and hyaline cartilage. So it can look like DRCT.
There is NO distinct perichondrium.
What makes up most of the connective tissue?
Bone ; 200 distinct skeletal elements
What are the functions of bones?
Framework
Levels for locomotor function
Protection
Hematopoeisis in bone marrow
Calcium Homeostasis
There are ___ types of bone. What are they and where are they found in the bone?
- Compact/Cortical
Very thick in middle of shaft and thinner at the ends. Makes up outside of bone.
- Trabecular/Cancellous/Spongy
Located at the ends of bones, has spaces for connective tissue or marrow
List the parts of a long bone from Superior to Posterior.
Epiphysis
(Epiphyseal/Growth plate)
Metaphysis made of spongy and compact bone
Diaphysis with bone marrow
Metaphysis
Epiphysis containing articular cartilage
The entire internal structure is covered by an endosteum. The bone itself is covered by periosteum
What happens to the epiphyseal plate once the bones have reached max length?
It will disappear!
The endosteum is important for what two regions?
Lining the internal structures of the bone and holding osteoprogenitor cells.
The epiphysis of the bone is made of ________.
Hyaline / Articular cartilage
The periosteum is made of what two layers?
Fibrous and osteogenic
Where are blood vessels in the bone?
The Medullary cavity in the bone marrow into trabecular bone
Bone is mineralized. How does it get nutrients?
Describe the structure.
Multiple Haversion systems or Osteons run longitudinally parallel to the length of the bone. They are separated by interstitial lamella
Osteons contain vessels in the middle that houses the blood vessels coming from Volkmanns Canals in a direction perpendicular to the Haversian canal.
Where do blood vessels for bones come from?
Periosteum or inside of bone
Cartilage is made of Type ___ collagen. Bones are made of ________ collagen.
Type II
Type I - Bones
The bone matrix is made of ________
Type I collagen arranged in a helical orientation to offer extra support
Mineralized products
What are located between the lamellae of osteons?
Osteocytes sit in osteocyte lacunae and are interconnected with other osteocytes by cell processes lodged in caniculli.
What are canaliculi and why are they important?
Little tunnels that host cell processes in the osteocyte lacunae that connect osteocytes to one another via gap junctions.
They allows cells closest to the blood vessel to cascade a message to cells all the way to the cells distally located.
Osteoblasts are responsible for ________.
What is their shape?
How does it stain?
Synthesis and mineralization of bone ECM.
Cuboidal cells that line bone-forming surfaces.
What is the fate of osteoblasts?
First osteoblasts lay down the collagen and non-collagenous proteins (non-organic). The matrix will become mineralized by osteoblasts and contain calcium phosphate
Osteoblasts can become encased in their own matrix and become osteocytes.
What is an osteoid?
The first thin organic layer of bone laid by osteoblasts.
The matrix of bone is made of _________. (compound)
calcium phosphate or hydroxyapetate
Osteoblasts originate from _________ which can give rise to _________.
What is required for the expression of __________ to differentiate from _______ progenitor cells to ________.
mesenchymal stem cells, chondrocytes, myoblasts, adipocytes
Runx2 ; Type I collagen
mesenchymal progenitor cells to Type I collagen, oseocalcin and non-collagenous proteins
Osteocytes result from _________. They make up over _______ of bone cells
osteoblasts being encased in bone matrix. 90%
Osteocytes maintain contact with __________ via ________.
Other osteocytes, Haversian canals, Periosteum, endosteum, sites of vasculature
via dendritic processes
Mesenchymal stem cells are precursors for __________.
Chondrocytes , Osteoblasts (which become osteocytes)
Osteoclasts are responsible for ______________.
They are located in ______ and are derived from ________ which also make ________.
Bone resorption or degradation of mineralized matric
Howship’s lacunae/ Resorption pit
hematopoetic stem cells, macrophaes and monocytes
Osteoclasts are multinucleated. True or False
True
Describe the structure of an osteoclast.
The periphery of an osteoclast seals the osteoclast to the bone via a region called the sealing zone. The zone contains integral proteins that make the connection between osteoclast and the bone.
The membrane inside the sealing zone creates a ruffled border to form a space for osteoclast processes to take place.
How do osteoclasts resorb bone?
- Chloride ions will cause a rise in H+ via a cascade reaction which lower the ph of the cell.
- Lysosomal enzymes are activated by the increase in H+ (acid anhydrases) and break down the organic matrix.
- Broken down collagen is excreted by the osteoclast cell distally from the bone (away from the sealing site)
What is another name for the sealing zone of an _______?
Osteoclasts
Clear Zone
We want a net ________ of bone when we are growing.
When we are matured, we want out bone to be ________ net.
When we get older, net bone is _______.
Positive
equal
negative
What maintains the balance of bone breaking and making?
RANK-L
- M-CSF (macrophage colony stimulating factor) stimulates osteoclast progenitors to express the RANK receptors to commit them to osteoclast lineage.
- RANK-L (RANK-Ligand), produced by BM stromal cells and osteoblasts binds to RANK to induce osteoclast formation and activation.
- Osteoprotegerin is also produced by BM stromal cells and osteoblasts that is a deocy RANK-L receptor to make RANK-L unable to bind to RANK.
__________ and _______ are both produced by BM stromal cells and osteoblasts to control bone breaking and making.
What ratios of these two facts show a higher rate of osteoclasts? Osteoblasts?
RANK-L - Osteoclast activation
Osteoprotegerin- RANK-L Decoy
Higher OPG = more osteoblasts
Higher Rank- L = more osetoclasts.
What 3 organs can regulate calcium levels?
- Bone
- Intestine
- Kidneys
Calcitonin _______________ in __________ and ________.
Decreases calcium and phosphate resorption in bone and reabsorption in kidney
PTH _____________ in bone but ___________ in kidney.
Increases calcium and phosphate resorption in bone
Increases calcium and decreases phosphate reabssorption
What is phosphaturia?
A kidney condition caused by an excessive decrease in phosphates.
What is osteogenesis?
What are the TWO ways it can happen?
Bone tissue formation
Intramembranous - Tissue is formed directively in primitive connective tissue (mesenchyme)
Endochondral
Bone tissue replaces a hyaline cartilage template
Which osteogenesis mechanism happens most often?
Endochondral
The replacement of hyaline cartilage with bone tissue is what allows the bones to grow and give us the growth plates.
Describe intramembranous bone formation
Mesenchymal cells condense and differentiate into osteoblasts and lay down bone.
Blood vessels bring in osteoclasts and themselves creating an island of bone that fuses with other islands.
Describe endochondral ossification.
Hyaline cartilage is the template of long bone.
The chondrocytes in the lacunae of cartilage enlarge forming hypertrophic cells. They produce a vascular endothelial growth factor to induce sprouting of blood vessels from the periCHONDRIUM.
Hypertrophic chondrocytes produce Type 10 collagen. These chondrocytes eventually die and leave spaces for blood vessels to invade. They bring in osteoblast progenitors to sit in the cartilage remnants to calcify it. This is the primary center of ossification and increases bone length by growing laterally in both up and down.
As this is happening in the center of the bone in the diaphysis, at the epiphysis’s (either end of the bone), the same process is occur in an outward direction to create a space for the metaphysis. An epiphyseal plate is now formed to allow for continued bone growth. Secondary ossification center.
Eventually, this plate gets thinner and thinner and dissapears.
What is the primary ossification center?
The central region of the bone, where bone tissue replaces cartilage, is known as the primary ossification center. It is the first site of bone formation and occurs in the diaphysis (shaft) of long bones.
Involved in Endochondral ossification
What is the secondary ossification center?
After birth, similar processes to primary ossification occur at the ends of long bones (the epiphyses), forming secondary ossification centers.
These centers of ossification develop later and contribute to the growth of bone in length.
Ossification in the diaphysis and epiphysis endochondrally occurs at the same time. True or false
Not necessarily! It can occur at different times.
Describe the 4 endochondral ossification zones
- Reserve Zone
Primitive hyaline cartilage responsible for the growth in length of bone.
- Proliferating Zone
Proliferating chondrocytes
- Hypertrophic zone
Apoptosis of chondrocytes and calcification of territorial matrix, secretion of Vascular endothelial growth factor
- Vascular invasion Zome
Blood vessels penetrate calcified septa and carry osteoprogenitor cells with them.
Proliferating zone is a good example of _______ growth.
Interstitial
Which “zone” of endochondral ossification secrete vascual endothelial growth factor?
Hypertrophic
Bone resorption occurs most on ________ and is formed on the _______. However, resorption occurs _____ which allows for the growth.
the inside, outside, slower
Fractures are repaired by which type of ossification?
Endochondral AND Interstitial
Steps of Fracture Healing
- Hematoma Formation
Swelling, hematoma, recruitment of neutrophils, and Mesenchymal Stem Cell progenitor populations.
LOW O2 promotes MSC differentiation into chondrocytes to produce cartilage and new blood vessels (angiogenesis)
- Callus Formation
Soft Callus - Fibrous and cartilaginous collar surrounds fracture and collar (callus) widens and stiffens to immobilize fractured ends.
Hard Callus - Initial bone formation in callus endochondrally. Intramembranous ossification occurs on surface.
- Bone Remodeling
Conversion of immature woven bone to mature lamellar bone with Haversian systems.
Low O2 promotes what two things during fracture healing?
- MSC differentiation into chondrocytes to produce cartilage
- Angiogenesis.
Children have _________ and better _______ periosteum which makes fracture healing quick.
thicker and better vascularized periosteum
What is another name for mature bone?
Lamellar Bone
What can affect fracture healing?
Lack of mobility
Extent of Gap
Vascularization
Oxygen Concentration
Calcium Deficiency
Osteoporosis
(Bone Loss)
Aging, Post-menopausal estrogen deficiency, Inflammation, Disuse, Diabetes
Increases RANKL/OPG ratio or decreasing OPG or both
Rickets/Osteomalacia
Inadequate mineralization
Defective Vitamin D intake or metabolism
Defective mineralization of osteoid
Increased osteoid thickness
Increased fracture risk
BOWING OF LEGS
Treatment: Vitamin D
Joints are classified by ________ and ______.
Types of tissue
Fibrous
Cartilaginous
Synovial
Degree Movement
Synarthrosis - Immobile
Cartilaginous- Slightly mobile
Synovial- Freely mobile
Sutures are _______ joints.
fibrous, synarthrosis
Gomphoses such as ________ are _____ joints.
teeth articulating in their sockets in jaw.
synarthrosis fibrous
Syndesmoses such as _________ are ________ joints.
interosseous membrane between radius and ulna
fibrous cartilaginous
Synchondroses are ________ and are ________ joints.
by bones connected by hyaline cartilage, cartilagenous synarthrosis joints
ribs to sternum, epiphyseal plate
Symphses are _________ and are _______ joints.
bones united by fibrocartilage, slightly movable cartilagenous.
Intervertebral discs, pubic symphysis
What is a synovial joint?
Fluid filled cavity contained in fibrous CT capsule. Synovial fluid secreted by synovial membrane.
