Cartilage And Bone Flashcards by Harpreet Kaur

Name the 3 types of cartilage and briefly explain their composition

HYALINE (extracellular matrix; CHONDROCYTES)
ELASTIC (matrix similar to hyaline cartilage; contains many elastic fibres and elastic lamellae)
FIBRO (matrix similar to hyaline cartilage; abundant in type I collagen fibres assembled into thick bundles)

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What does the extracellular matrix of hyaline cartilage consist of?

Type II collagen
Hyaluronic protein aggregates between collagen fibrils (composed of GAGs and hyaluronic acid)
CHONDROCYTES

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What is a GAG and what is its role in the extracellular matrix?

GLYCOSAMINOGLYCAN
Combines with hyaluronic acid to form HYALURONATE PROTEOGLYCAN AGGREGATES
Highly NEGATIVE charges on GAGs so attract water to form a hydrated gel

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Explain the role of chondrocytes in cartilage

Produce and maintain extracellular matrix

- Sit in a LACUNA within the extracellular matrix

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What is an isogenous group?

Chondrocytes which have undergone mitotic division and cluster together
Isogenous groups separate as they elaborate extracellular matrix

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What is meant by an ‘articulating surface’?

Surface where bones meet joints

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List 5 places in the body where you might find HYALINE cartilage

Costal rib cage
Nose
Trachea
Bronchi
Larynx

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What is the arrangement and role of hyaline cartilage in the upper respiratory tract?

Arrangement: C shaped rings

- Role: hold airways open and prevent them from collapsing

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What is the perichondrium and what does it consist of?

DENSE CONNECTIVE TISSUE
Lies on the margins of hyaline cartilage
Contains flattened fibroblast-like cells which can develop into CHONDROBLASTS
Chondroblasts secrete matrix components and develop into CHONDROCYTES

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Distinguish between APPOSITIONAL GROWTH and INTERSTITIAL GROWTH of cartilage

APPOSITIONAL GROWTH is the growth of cartilage from the periphery (from the edges)
INTERSTITIAL GROWTH results from the separation and deposition of isogenous groups as they lay down further into the extracellular matrix

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Explain why there is no perichondrium present at articulating surfaces

Perichondrium is a thin layer of connective tissue

- Abrasion at articulating surfaces will cause perichondrium to wear away

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Describe the position of hyaline cartilage at the end of a long bone

Hyaline cartilage lines articulating surface of bone
Also forms EPIPHYSEAL GROWTH PLATE (boundary between spongy/cancellous and compact bone)
No perichondrium present at either of these sites

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State 2 differences between hyaline and elastic cartilage

Elastic cartilage has elastic fibres in the extracellular matrix
Elastic cartilage does not undergo ossification

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Where in the body might you find elastic cartilage?

Located mainly in head and neck:

Epiglottis
Eustachian tube
External ear (pinna)
Acoustic meatus

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How could you distinguish between hyaline and elastic cartilage histologically?

Elastic cartilage contains dark stained areas where there is an abundance of elastic cartilage

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Name the 2 cell types found in FIBROCARTILAGE

Chondrocytes

- Fibroblasts

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Describe the distribution of cells in fibrocartilage

Arranged in rows

- Parallel to direction of dense regular connective tissue

Describe the composition of fibrocartilage

Dense regular connective tissue
Type I (and type II) collagen
Chondrocytes and fibroblasts in rows
No perichondrium present

What is the main role of fibrocartilage?

RESILIENCE

- Acts as a shock absorber and resists shearing forces

List 4 places where fibrocartilage is located in the body

Intervertebral discs in vertebrae (spine)
Articulating discs of sternoclavicular and temporomandibular joints
Meniscus of knee (2 pads on each cap)
Pubic symphysis

What are the 2 types of bone?

Compact (dense)

- Spongy/cancellous (trabecular)

Describe the general composition of bone

65% minerals
23% collagen
10% water
2% non-collagen proteins

What composes the spongy/cancellous bone?

Network of fine bony columns/plates called TRABECULAE
Bone marrow in between spaces
Avasuclar (no vessels)
Combines STRENGTH with LIGHTNESS

What are the main features of compact bone?

ENDOSTEUM (inner surface adjacent to bone marrow)
PERIDOSTEUM (outer surface)
Arranged in OSTEONS
Concentric and interstitial LAMELLAE
Haversian canals and Volkmann canals

What is an osteon?

- Haversian canal surrounded by concentric lamellae - Osteocytes present throughout lamellae - Have the ability to branch out and terminate - LONGITUDINAL in same direction/plane as bone

List 3 common features of a Haversian canal and Volkmann canal

- Contain blood vessels - Contains nerves - Contains lymph vessels

How does immature bone differ from mature bone?

Osteocytes and blood vessels are randomly arranged

Explain how INTERSTITIAL LAMELLAE are formed

- Successive generations of Haversian systems formed by OSTEOBLASTS - OVERLAPPING of successive Haversian systems where positioning does not necessarily precede that of the previous Haversian system

What is the role of the OSTEOCYTE CANALICULI?

- Slender cytoplasmic processes which project to adjacent osteocytes - Connect via GAP JUNCTIONS - Allow transfer of nutrients between osteocytes - Removal of waste products by gaseous exchange

Explain how cancellous bone is remodelled

- OSTEOCLASTS bore holes into bone via a cutting cone. Old bone material is digested by lysosomal enzymes and acids secreted by the cells - OSTEOBLASTS lay down new bone material to form new osteons (do not necessarily follow the pattern of the preceding osteon) - Osteoblasts become submerged in new bone material and form OSTEOCYTES

How does the breaking of a bone result in a HAEMOTOMA?

- Breakage of blood vessels that lie in bone and periosteum - Cells around fracture die due to lack of blood supply and nutrients - Inflammatory cells invade - Phagocytes and macrophages digest dead cells and material

Explain how a fibrocartilagious callous is formed

- Procallous of GRANULATION TISSUE develops which is rich in capillaries and fibroblasts - Some fibroblasts produce collagen fibres which span the breakage; others differentiate into chondroblasts (further into chondrocytes) which give rise to a sleeve of hyaline cartilage - Fibrocartilagious callous splints the bone - Osteoblasts invade breakage zone and begin producing new cancellous bone

Explain the formation of a bony callous

- Formation of new trabecular bone - Endochondral ossification of hyaline cartilage - Intramembranous ossification adds to cancellous bone to form contact bone - Bony callous formation continues for 2 months until a very firm union is formed

Define ENDOCHONDRAL and INTERMEMBRANEOUS ossification

- Endochondral ossification is the conversion of hyaline cartilage to bone - Intermembranous ossification is the formation of new cancellous bone

What is the purpose of bone banks?

- Supply viable bone for grafting purposes by orthopaedic surgeons - Bone fragments are frozen to preserve them

Describe the composition of TRABECULAE in spongy/cancellous bone

- Hint of concentric lamellae - Osteocytes lie between lamellae - NO HAVERSIAN OR VOLKMANN CANALS - Osteocytes gain nutrients from surrounding bone marrow - Osteoblasts lie on the peripheral of trabecula laying down new bone

Define the terms autograft, homograft and heterograft in relation to bone grafting techniques

- Autograft - bone graft is from the same individual - Homograft - bone graft is from a different individual - Heterograft - bone graft is from a different species/animal

Which bone grafting technique is the most successful and why?

- Autograft - Graft will not be seen as 'foreign' as it is from the same individual (same antigens) - Less chance graft will be rejected by body

When does intramembraneous ossification occur?

Formation of flat bones of skull, face and clavicle

When does endochondral ossification occur?

- Hyaline cartilage is replaced by bone through mineralisation (osteoid) - Occurs at epiphyseal growth plates (during formation on long bones) and development of skeleton from fetal skeleton