Cartilage And Bone Flashcards
How does cartilage resist repeated application of pressure?
Extracellular matrix is pliable also has a high amount of hyaluronic acid and so forms hydrated gel.
How do chondrocytes obtain their nutrients?
Cartilage is avascular. High ratio of GAGs to collagen permits ready diffusion of nutrients from the blood vessels surrounding the cartilage
What are the three types of cartilage?
Hyaline cartilage
Elastic cartilage
Fibrocartilage
What does hyaline cartilage contain?
Chondrocytes
Type 2 collagen
Ground substance - proteoglycans and hyaluronic acid
Hyaluronate proteoglycan aggregates are bound to collagen.
What does elastic cartilage contain, in addition to that found in hyaline cartilage?
Elastic fibres and elastic lamellae
What does fibrocartilage have in addition to hyaline cartilage?
Type 1 collagen
What is a group of recently divided chondrocytes called?
Isogenous group
What causes chondrocytes in an isogenous group of chondrocytes to separate?
Elaboration of matrix
Where is hyaline cartilage found?
Articulating joints. Rib cage Nose Trachea, larynx, and bronchi Epiphyseal growth plates.
What covers the margin of hyaline cartilage?
Perichondrium
What cells are present in the perichondrium, and what do they differentiate into?
Fibroblast like cells, which differentiate into chondroblasts and then chondrocytes.
Classify perichondrium as a type of connective tissue.
Dense connective tissue (? Irregular)
What are the two ways by which cartilage grows?
Appositional growth - matrix secreted by chondroblasts in the perichondrium.
Interstitial growth - matrix secreted by chondrocytes deeper in the cartilage.
What is the difference between territorial and interterritorial matrix?
Territorial matrix is more highly sulphated.
Territorial matrix closely surrounds the chondrocytes, recently laid down, interterritorial is further away.
What do chondrocytes lie in, and what happens during fixation?
Lacunae, chondrocytes shrink during fixation.
What directs the synthetic activity of chondrocytes?
Pressure loads create mechanical, electrical and chemical signals.
What makes up the skeleton of the fetus?
Hyaline cartilage.
Does the hyaline cartilage on articulating surfaces have a perichondrium?
No.
Does elastic cartilage calcify?
No
Where is elastic cartilage found?
External ear (pinna), external acoustic meatus, Eustachian tube, epiglottis.
How might you identify elastic fibres in a micrograph?
They stain darker.
What cells are present in fibrocartilage?
Fibroblasts and chondrocytes.
How are the cells often arranged in fibrocartilage?
In rows
Where is fibrocartilage found?
Pubic symphysis, articulating discs of the temperomandibular and sternoclavicular joints, intervertebral discs, menisci of the knee.
What is the role of fibrocartilage?
Resist shearing forces
Shock absorption
Does fibrocartilage have a perichondrium?
No.
What lies in the centre of an osteon, and what does it carry?
Haversian canals. Blood vessels, lymphatic vessels and nerves.
What canals run perpendicular to the length of the bone, and what do they carry?
Volkmann’s canals - blood vessels, lymph vessels and nerves.
What are the different possible locations of lamellae in bone?
Inner circumferential lamellae
Outer circumferential lamellae
Interstitial lamellae
Lamellae within an osteon
What is the difference between mature and immature bone?
Immature bone has randomly arranged osteocytes.
Mature bone has osteocytes arranged within concentric lamellae of osteons. Resorption canals are parallel with osteons.
How are osteons arranged in bone?
Able to branch and terminate.
What are canaliculi?
Tunnels in which cytoplasmic extensions of osteocytes lie, that permit transport of substances to osteocytes further away from the Haversian canal.
Cytoplasmic extensions are connected by gap junctions.
What is the structure of cancellous bone?
Arranged in trabeculae, which have no Haversian or Volkmann’s canals, osteocytes lie between concentric lamellae.
What lies in the cavities of cancellous bone?
Red bone marrow - haemopoietic cells
Yellow bone marrow - adipose cells
How do osteoclasts resort bone?
Release Hydrogen ions and lysosomal enzymes
What is a cutting cone?
Bone remodelling unit - osteoclasts followed by osteoblasts laying down osteoid.
What is the composition of bone?
65% calcium hydroxyapatite crystals.
23% type 1 collagen
2% non collagen proteins
10% water
How does bone resist fractures?
High tensile and compressive strength
Flexibility - lamellae able to slip relative to each other
What is the process of fracture healing?
Haematoma forms, granulation tissue forms
Procallus forms of fibrocartilage, bony trabeculae form
Ossified (endochondral and intermembranous) forms cancellous bone
Cancellous bone replaced by cortical bone, then remodelled.
How does the fibrocartilaginous callous form?
Capillaries invade haematoma.
Tissue rich in fibroblasts and blood vessels (Procallus) forms.
Fibroblasts secrete collagen type one which spans the break.
Other fibroblasts differentiate into chondroblasts - secrete a sleeve of hyaline cartilage
Osteoblasts from periosteum and endosteum form spongy trabecular bone.
What occurs during haematoma formation?
Blood vessels in bone are broken, bleeding into fracture, clot = haematoma.
Swelling and inflammation.
Osteocytes cells at edge of fracture die due to lack of blood supply.
Phagocytes and osteoclasts remove dead bone
Macrophages eventually remove haematoma.
How does bony callus formation in fracture repair occur?
Bony trabeculae form and endochondral ossification converts the fibrocartilaginous callus to cancellous bone.
Continues for 2 months
How does bone remodelling in fracture repair occur?
Cancellous bone converted to cortical bone.
Bulging edges removed by osteoclasts.
Eventually takes original shape as responding to same mechanical stressors
Occurs for several months.
What are the three different bone grafts?
Autograft - from the recipient (most successful)
Homograft - from another human - may be rejected.
Heterograft - another species - least successful, but calf bones lose antigenicity on refrigeration.
