L15- Cartilage And Bone Flashcards
A) What are the 3 types of cartilage?
B) what do all 3 have in common?
A) Hyaline cartilage, Elastic cartilage and fibrous cartilage
B) all have Chondrocytes and all have a matrix containing proteoglycan and hyaluronic acid
HYALINE CARTILAGE:
A) Composition: cells and matrix
B) Where where it found?
C) function
A)
Cells: Only contains chondrocytes that are present singly or in isogenous groups
Extracellular matrix: proteoglycan and hyaluronic acid bound to fine collagen matrix (type 2 fibres)
Isogenois= equal origin
B) Parts of articulating surface ( articulater joints) epiphyseal plate until growth ceases and parts of the rib cage, nose, trachea, bronchi and larynx
C) Endochondral ossification- hyaline cartilage is the precursor model of the bones that develop in this way
A) Function of chondrocytes and where are they found?
B) what does the extracellular matrix in all cartilage consist of and its function?
A) Produce and maintain the extracellular matrix
- lie in a lacuna: a depression
- lay down extracellular matrix in vesicles in the cell and when they burst release the matrix
B) Proteoglycan and hyaluronic acid: brings h20 into tissue, assists resilience to the repeated application of pressure, good shock absorber- makes a stiff gel like substance
How does hyaline cartilage grow?
- Grows from the perichondrium- contains fibroblast like cells that develop into chondroblasts and then into chondrocytes
- chondroblasts produce and maintain extracellular matrix
Can either grow just from the periphery: appositional growth OR from two sides: interstitial growth
Why is the extracellular matrix so important in cartilage?
Hyaluronic acid brings water into tissues, water is non-compressible and so permits resilience to increase loads
Outline the structure and function of cartilage in the tracheal wall
Tube formed by C-shaped hyaline cartilage ring
- reinforces trachea
- protect and maintain airway (prevents it from collapsing so gas change can occur)
- lined with pseudostratified ciliated epithelium
ELASTIC CARTILAGE:
A) Composition: cells and matrix
B) Where where it found?
C) function
A)
Cells: only chondrocytes
Matrix: elastic fibres and elastic lamellae (layers)- confers elasticity
B) only in 3 places:
- Pinna of the ear
- Eustachian tube
- Epiglottis
C) extra flexibility and support
What would you see in a histology of the trachea?
- Pseudostratified columnar ciliated epithelium and submucosa- glands and goblet cells
- Perichondrium: connective tissue sheath that covers cartilage.
Vascular. Contain fibroblast-like-cells that develop into chondroblasts then chondrocytes - Hyaline cartilage ring (c shaped: contain chondrocytes in a lacuna and extracellular matrix
What would you see in a histology slide of the pinna of the ear?
- Skeletal muscle- striated
- Adipose tissue (white areas)
- Fibrocollagenous tissue with chondroblasts on edge
- Elastic cartilage: dark staining elastin fibres, sometimes holes where chondrocytes used to be
- Dermis/epidermis
- Keratinised material on surface
FIBROCARTILAGE:
A) Composition: cells and matrix
B) Where where it found?
C) function
A)
Cells: chondrocytes AND fibroblasts
Only type of cartilage that contains type I and type II collagen (combination of dense regular connevgtive tissue and hyaline cartilage)
B) Intevertebral discs, articulate discs of sternoclavicular and temporomandibular joints and menisci of the knee joint and in the pubic symphysis
C) found in areas of directional stress, where resistance to compression, durability and tensile strength are needed
Resilience to act as a shock absorber and resist shearing forces
Why does fibrocartilage not have any distinct perichondrium?
Because it blends with other tissues such as tendon or hyaline cartilage
A) What is bone ossification?
B) what are the types?
C) what is the similarities and differences?
A) the process of bone formation
B) Intramembranous and endochondral
C) Both of them begin with a mesenchymal tissue precursor
- Intramembranous: the formation of bone from clusters of mesenchymal stem cells in the centre of the bone- forms the flat bones of the skull, clavicle and most of cranial bones
- Endochondral: begins with mesenchymal tissue transforming into a cartilage intermediate. Uses cartilage as a template which is later replaced by bone and forms remainder of axial skeleton and long bones
Outline the structure of long bones
- include the structure if it was a growing bone
Two parts:
- Diaphysis: tubular shaft in the middle. Hollow region: medullary cavity (yellow marrow) and walls: compact bone
MEDULLARY CAVITY:
- inside lining called endosteum (growth and remodelling)
- Fibrous membrane surface called periosteum (blood vessels, nerves that nourish bone)
- Epiphysis: wider section at each end of the bone, filled with spongy bone with red marrow
- covered with articular cartilage that reduces friction
If a growing bone:
Would have an epiphyseal plate (growth plate with a layer of hyaline cartilage)
If adult hood:
Epiphyseal plate replaced by epiphyseal line
Outline the process of endochondral ossification
Developing long bones e.g. femur
Hyaline cartilage model
Begins in fetal development:
- Mesenchymal cells —> chondrocytes (proliferate and secrete ex cell matrix to form hyaline cartilage and perichondrium)
- collar of periosteal/ compact bone appears in the shaft
- Primary ossification centre formed: central cartilage calcifies
- nutrient artery penetrates, supplying bone depositing osteogenic cells
Post natal:
4. Medulla becomes cancellous bone. Cartilage form Epiphyseal growth plates.
Secondary ossification centres develop in the epiphyseal region
5. Epiphyses ossify and growth plates continue to move apart, lengthening the bone.
6. Epiphyseal growth plate replaced by bone but the hyaline ARTICULAR cartilage stays.
What happens to the epiphyseal growth plate of adults?
It disappears after the cessation of growth.
A) Composition of bone matrix?
B) composition of bone cells?
A)
- 65 percent inorganic: calcium hydroxyapatite (ca, po4, carbonate, cl) and magnesium salts
- 35 percent organic:
- collagen 1
- GAGS and proteoglycans
- non- collagenous proteins
B)
1. Osteoprogenitor: undifferentiated stem cell, produce osteoblasts.
Found in inner layer (endosteum) and outer layer (periosteum)
- Osteoblasts: intermediate cells: immature bone cell that secretes organic components of matrix (divide into osteocytes). When trapped becomes osteocyte
- Osteocytes: mature bone cell that maintains the bone matrix (trapped within osteon/ matrix)
- Osteoclasts: huge cells that are fused monocytes (multinucleate) Secrete acids and enzymes to dissolve bone matrix. Reabsorption of existing bone
Outline the process of Intramembranous ossification
- MSC aggegrate (form tight cluster)
- MSC differentiate into osteoprogenitor cells and then osteoblasts
- osteoblasts group form an ossification centre- begin secreting osteoid (unmineralised collagen-proteoglycan matrix that can bind calcium)
- Osteoid mineralises- crystals of calcium form in and around it to form rudimentary bone tissue spicules (surrounded by osteoblasts and contain osteocytes)
- leads to entrapment of osteoblasts- formation of osteoblasts to osteocytes
- Spicules join to form trabeculae which merge to spongy bone
- trabeculae replaced by lamellae of mature compact bone
Outline the microstructure of Compact/cortical bone
- Functional unit: Osteon (cylinders): layers of compact mineralised collagen which has a central canal called the Haversian canal
- Matrix (mineralised collagen) traps osteoblasts (produce bone) and then form osteocytes
- Between the layers of collagen the osteocytes are located in lacunae
- Haversian canal: contain blood vessels that are parallel (vertical) to long bone
- the volkmanns canal (horizontal) connect the blood vessels
- Osteoclasts are found on the edges (periosteum and endosteum) and not in cortical bone
How do osteocytes communicate?
- maintain connections with each other through channels within bone called canaliculli.
- Osteocytes extend processes called filopodia
through the canaliculli. - Filopodia from adjacent cells contact each other and communicate via gap junctions.
How could you identify the following cells in a histology slide?
A) Osteoblasts
B) osteoclasts
C) osteoid
A) they would be around the edge of the osteoid
B) multinucleated and are found in regions where bone appears to be carved out- they would be surrounded by blue osteoid
C) osteoid would be the blue matrix that entraps the cells
What is the difference between osteoarthritis and rheumatoid arthritis?
Osteoarthritis:
- age related degeneration
- mechanical failure of the articular cartilage leading to narrowing of the joint space: bone rubs against bone
- growth of bony spurs causes inflammation and pain
Rheumatoid arthritis (RA)
- autoimmune disease
- osteoclasts will degrade the bone and macrophages will come in digest the bond sending signals to stimulate an immune response, T cells will create an autoimmune response damaging the cartilage
- fibroblasts lay down scar tissue
- extensive angiogenesis leads to more fluid and more inflammation
Inflammation of the synovial membrane and thickening of the joint capsule: bone and cartilage disintegrate
Outline the microstructure of cancellous/spongy bone
- consists of trabeculae: lamellae that are arranged as rods or plates
- red bone marrow found between the trabeculae
- blood vessel within this tissue deliver nutrients to osteocytes and remove waste
a) Outline the structure and function of hyaline articular cartilage
b) How would this look on histology?
a) covers articular surfaces of synovial joints
No perichondrium
Very flexible
Shock absorption
Chondrocytes are embedded in lacunae.
b) You would see the synovial fluid/joints
How would you see elastic cartilage on histology slides?
CM contains a threadlike meshwork of elastic fibers.
How can spongy bone be converted into compact bone
Bone remodelling
In a histology slide how would you be able to tell a bone is arising from endochondral ossification or intramembranous ossification ?
Intramembranous: has osteocytes, osteons, haversian and volkmanns canals
a) What is the perichondrium?
b) Where is it found and not found?
c) Function?
a) dense layer of fibrous connective tissue that covers cartilage in various parts of the body
b) elastic cartilage in parts of the ear, nose, hyaline cartilage in the larynx and trachea, epiglottis, area where the ribs connect to the sternum and area between the spinal vertebrae
-In adults, perichondrium tissue does not cover articular cartilage in the joint
c) Contain fibroblast-like-cells that develop into chondroblasts then chondrocytes
- it is vascular and its vessels supply nutrients to chondrocytes
Difference between chondroblasts and chondrocytes
The extracellular matrix of cartilage is secreted by chondroblasts, (chondro = cartilage), which are found in the outer covering layer of cartilage. As the chondroblasts secrete matrix and fibres, they become trapped inside it, and mature into cells called chondrocytes
What is osteoid?
unmineralised collagen-proteoglycan matrix that can bind calcium
Difference in appositional and interstitial growth of cartilage?
- Appositional: growth from the OUTSIDE/periphery
- chondroblasts in perichondrium secrete matrix (on the edges), perichondrium then grows larger and then the chondroblasts become chondrocytes, grows in WIDTH - Interstitial: growth from within tissue
- chondrocytes are in isogenic groups and secrete new matrix from within the lacunae and they spread apart, increases in LENGTH
