Flashcards in ToB 11 Cartilage and Bone Deck (99)
Name the 3 types of cartilage:
1) Hyaline cartilage
2) Fibrous cartilage
3) Elastic cartilage
What is the function of chondrocytes?
Chondrocytes produce and maintain the extracellular matrix within cartilage
How can you tell the upper edge of cartilage from the middle, in a histology slide?
The upper edge has flattened cells, which are the developing chondrocytes, and the middle of the cartilage will be full of extracellular matrix
Describe the properties of extracellular matrix within cartilage:
Solid, firm, pliable
Large amounts of WHAT in the ECM of cartilage gives it resilience to the repeated application of pressure?
How do the proteoglycans and hyaluronic acid molecules allows the cartilage ground substance to form a hydrated gel?
The high density of negative charges on the GAGs in cartilage ground substance attracts water molecules strongly, forming the hydrated gel.
What molecules in cartilage ground substance form the hydrated gel consistency?
Proteoglycans, hyaluronic acid molecules and water
What is hyaline cartilage extracellular matrix composed of?
- Hyaluronic acid molecules
- Type II collagen
What type of cells are present in hyaline cartilage?
What is elastic cartilage extracellular matrix composed of?
- Hyaluronic acid molecules
- Type II collagen
- Elastic fibres (form lamellae)
What is different between the composition of hyaline cartilage extracellular matrix compared with elastic?
Elastic cartilage is the same as hyaline, but with the addition of elastic fibers.
What is fibrocartilage extracellular matrix composed of?
- Hyaluronic acid molecules
- Type I collagen
- Type II collagen
What are the main differences in the composition between hyaline and fibrocartilage?
- Fibrocartilage contains abundant type I collagen, which is not a component of hyaline cartilage
- Fibrocartilage contains less cells compared to hyaline cartilage
Why do chondrocytes sometimes form isogenous groups?
Chondrocytes form these clusters if they have recently divided, but will separate.
What is the name of the process by which fetal hyaline cartilage develops into bone?
What type of cartilage is the precursor for the human skeleton (ie present in foetus)?
Where is hyaline cartilage present while long bones are developing?
- Articulating surfaces
- Epiphyseal plates
Where is hyaline cartilage sited?
- Articulating surfaces of joints
- Costal cartilage (extend ribcage)
- Larynx, trachea, bronchi
What is the name of the dense layer of cells which cover the margin of hyaline cartilage?
How can you tell the perichondrium from the main hyaline cartilage in a histology slide?
The perichondrium is at the edge of the cartilage, and contains many elongated cells, compared to the main hyaline cartilage which contain large cells surrounded by ECM.
What type of cells produce and maintain cartilage extracellular matrix?
What type of cells are contained in the perichondrium?
Describe the formation of chondrocytes:
Fibroblast-like cells from the perichondrium develop into chondroblasts, which then develop into chondrocytes.
What is meant by 'appositional growth'?
Growth by the addition of new layers on those previously formed - growth from the periphery.
What types of growth does cartilage undergo?
Appositional and interstitial growth
What is meant by 'interstitial growth'?
Growth within layers that have already been formed.
How does cartilage grow via interstitial growth?
Chondrocytes deep in the cartilage may divide, increasing the number of cells present, so ECM is increased.
What factors give hyaline cartilage resilience against varying pressure loads?
- Highly hydrated extracellular matrix
- Transient movement of water
What name describes the ECM close to chondrocytes, which stains dark with H&E?
What two types of matrix can be differentiated when the hyaline cartilage is stained with H&E? Why can they be differentiated?
1) Territorial matrix
2) Interterritorial matrix
The territorial matrix stains darker than the interterritorial matrix, as it is more highly sulphated
What are the white lacunae that the chondrocytes lie within, which can be viewed on histology slides?
These are artefactual shrinkages due to slide preparation.
How do pressure loads direct the synthetic activity of chondrocytes?
Pressure loads create mechanical, electrical and chemical signals, to which the chondrocytes respond to.
At which cartilage surfaces is a perichondrium present?
What are the 2 types of bone present in the body?
What is cancellous bone?
It is very porous and contains red bone marrow, where blood cells are made. It is weaker and easier to fracture than cortical bone.
What is cortical bone?
Very dense and strong bone, which is difficult to fracture. Its primary purpose is providing structural support to the body and its organs and tissues.
Long bones can be split into 5 sections, what are they?
1) Proximal epiphysis
5) Distal epiphysis
What is the name of the shaft-part of a long bone?
Why is it important that an articulating surface of bone is very smooth?
To allow a friction-free environment, for articulation with the adjacent bone
Describe the appearance of the boundary between hyaline cartilage and underlying bone in an epiphysis of a long bone:
Name a type of cartilage that does not calcify:
Name a type of cartilage which does calcify:
Where is elastic cartilage found in the human body?
- External ear
- Eustachian tube
- External acoustic meatus
What is the eustachian tube?
Narrow tube from nasal pharynx to the cavity of the middle ear, which allows the equalisation of pressure either side of the ear drum.
What type of cartilage is found in the epiglottis?
What type of cartilage is 'costal cartilage'?
What is the dark staining material present in a histology slide of elastic cartilage?
Elastin fibres within the ECM
Which type of cartilage stains darker: hyaline or elastic? Why?
Elastic cartilage stains darker due to abundant elastin fibres present.
What cell types are present in fibrocartilage?
What types of connective tissue is fibrocartilage a combination of?
- Dense regular connective tissue
- Hyaline cartilage
In what types of cartilage is a perichondrium present?
What type of cartilage does not have a perichondrium?
Where is fibrocartilage found in the human body?
- Intervertebral discs
- Articular discs of sternoclavicular joints
- Articular discs of temporomandibular joints
- Menisci of knee joint
- Pubic symphysis
In what type of cartilage are the chondrocytes often arranged in rows?
What type of collagen fibres are present in fibrocartilage?
- Type I
- Type II
What types of cartilage contains more cells than fibres?
What type of cartilage contain more fibres than cells?
What is an 'enthesis'?
The point of attachment between tendons and bones. May be fibrous or fibrocartilaginous.
What lies within the trabeculae of cancellous bone?
Red bone marrow
Why are all bones not cortical?
What and where is the endosteum?
A thin vascular membrane lining the cavity of cancellous bone (separates compact bone from cancellous)
What and where is a Haversian canal?
Canal through the middle of an osteon of cortical bone, which carries blood and lymph vessels, and nerves.
What and where is a Volkmann's canal?
Canal which connects adjacent osteons within cortical bone, linking with Haversian canals.Carries blood, lymph and nerves.
What and where is the periosteum?
A vascular membrane which envelopes bones, but is not present at articulating surfaces of joints.
How can you tell immature bone from mature?
Mature bone is organised into osteons, and osteocytes are arranged in the lamellae of these osteons. Immature bone is randomly arranged.
What is a resorption canal?
Canal within mature cortical bone, where bone is broken down and reformed.
Why is bone usually decalcified to create histology slides?
Calcified bone would be so dense that it would damage the microtome blade, so must be decalcified.
Why do interstitial lamellae of osteons form?
As bone is constantly remodelled, parts of an osteon is broken down and reformed in a slightly different way, causing overlap, creating interstitila lamellae.
Are osteons usually straight or branched?
How can you tell a Haversian canal from a Volksmann's canal?
Haversian canals have concentric lamellae of osteons, Volksmann's canals do not.
Why do osteocytes have tiny canaliculi?
To allow them to connect to the canals and/or adjacent osteocytes, supplying nutrients.
How do osteocytes recieve nutrients?
They have canaliculi, which may connect to the canals within cortical bone, which carry blood vessels, which supply nutrients.
The canaliculi may instead connect to adjacent osteocytes, which they can recieve nutrients from via gap junctions between canaliculi.
Describe the internal structure of a trabeculae of cancellous bone:
Organised into interstitial lamellae, inbetween which lie osteocytes.
How do the osteocytes within cancellous bone trabeculae recieve nutrients?
From the bone marrow.
Which 2 types of cells are responsible for remodelling cancellous bone?
What is 'osteoid'?
A gelatinous substance secreted by osteoblasts, which is the unmineralised portion of the bone matrix. This will mineralise and become bone.
What type of cell becomes an osteocyte?
How does an osteoblast become an osteocyte?
Osteoblasts secrete osteoid, and become trapped in the bone matrix
How do osteoclasts break down bone?
Secrete H+ and lysosomal enzymes
What is a 'cutting cone'?
A boring tunnel via which osteoclasts break down bone.
What determines the amount of remodelling a bone goes under?
The amount of stress put on the bone
What is the composition of bone?
65% Mineral - Calcium hydroxyapatite crystals
23% Type I Collagen
2% Non-collagen proteins
What factor allows bone to have a degree of flexibility?
Osteons can slip slightly at the margins of each lamellae, allowing a slight bend before breaking
What are the 4 main stages of fracture repair?
2) Fibrocartilaginous callus formation
3) Bony callus formation
4) Bone remodelling
What causes the haematoma immediately after a fracture?
The breaking of blood vessels in the bone
What is a 'haematoma'?
Mass of clotted blood
Why do bone cells at the edge of a fracture die?
Lack of blood/nutrient supply
What type of cells remove dead and damaged tissue from a fracture site?
- Phagocytic cells
What type of cells remove the haematoma from a fracture site?
What is granulation tissue?
New tissue rich in capillaries and fibroblasts, which forms on the surface of a wound during healing.
What happens during the fibrocartilaginous callus formation stage of fracture repair?
- New blood vessels infiltrate haematoma
- Granulation tissue is formed (procallus)
- Fibroblasts produce collagen fibres
- Collagen fibres span the fracture
- Fibroblasts differentiate into chondroblasts
- Chondroblasts produce sleeve of hyaline cartilage
What happens during the bony callus formation stage of fracture repair?
- Osteoblasts (from periosteum and endosteum) invade fracture site and form cancellous bone
- Trabeculae develop, replacing the fibrocatilaginous callus with cancellous bone
What occurs after the bony callus has formed during fracture repair?
How long does bone remodelling continue for, after a fracture?
What type of cells remove the bulging bone which forms after a fracture?
How does a remodelled bone (after a fracture) have the same shape as the original bone?
Because it responds to the same set of mechanical stressors.
What type of donor provides bone for a heterograft?
A different species to that of the recipient.
What is the most successful type of bone graft, and why?
Autograft, as bone donor is the recipient, so recipient is very unlikely to reject the donated bone.