Locomotion Flashcards
There are no anastamoses between epiphyseal and metaphyseal vessels until skeletal maturity is reached. Why?
Due to growth plate blocking anastamoses formation
Drainage of cortical bone occurs where?
Periosteal venules
What makes up the bone matrix?
Collagen (type I)
Glycoproteins
Hydroxyapatite (calcium and phosphate)
Which bone cell type is thought to have a role in the sensing of mechanical strain?
Osteocytes. They have fine processes extending into canaliculi which form junction with processes from other cells
Which bone cell type is multinucleate? What do these cells do?
Osteoclasts
Secrete hydrogen ions and lysosomal enzymes to degrade bone matrix.
What is the sealing zone in bones?
Adhesion between osteoclasts and bone.
What type of nerve branches do Haversian canals have?
Vasomotor and sensory nerves
What is a volkmann’s canal?
Transverse blood vessel joining two Haversian canals
Where are osteoblasts and osteoclasts derived?
Osteoblasts: mesenchymal cells
Osteoclasts: haemopoietic cells (form mononucleate preosteoclasts)
In which domestic species are secondary ossification centres present at birth?
Ungulate species
What part of the femur ossifies the quickest and what part the slowest?
Femoral head is the quickest
Lesser trochanter is the slowest
Growth in bone length happens though which mechanisms? How about expansion of the epiphysis?
Chondrocyte proliferation in the growth plate
Chondrocyte proliferation in the articular-epiphyseal growth cartilage
Explain how remodelling occurs within cortical bone.
Osteoclasts tunnel through longitudinally
Osteoblasts follow and deposit concentric lamellae of bone
What factors stimulate osteoblasts activity?
Sex steroid hormones
BMPs/growth factors
Mechanical load
Infl. cytokines and prostaglandins
What factors stimulate osteoclast activity?
Mechanical unloading
Infl. cytokines and prostaglandins
PTH
(Effects mediated by osteoblasts through RANKL)
What are the four steps in fracture repair?
- Inflammation (haematoma—>infl mediators—>mesenchymal cells)
- Soft callus formation (mesenchymal cells—>chondrocytes/fibroblasts—>fibrocartilaginous plate)
- Hard callus formation (endochondral ossification)
- Remodelling (mineralised bone matrix)
What is interstitial growth?
Proliferation of chondrocytes resulting in pairs of chondrocytes within the same lacunae
What substances make up the extracellular matrix of cartilage?
▪️Type 2 collagen
▪️amorphous material
▫️proteoglycans (core protein and sulphate glycosaminoglycans) and hyaluronan (a non-sulphate GAG)
What characteristic of GAGs help it to resist compression?
They have multiple negative charge making the, strongly hydrophilic. Swelling pressure of proteoglycan aggregates helps resist compression and is resisted itself by tension in the type 2 collagen fibres
Which cartilage types have a perichondrium?
Hyaline and elastic
Hyaline cartilage has a high or low ratio of GAGs to collagen? What about fibrocartilage?
Hyaline: high
Fibro: low
Chondrocytes are arranged in columns in which type of cartilage?
In growth plate of hyaline cartilage and in fibrocartilage
Chondrocyte proliferation is stimulated by what factors? What inhibits it?
Growth hormone which acts through insulin-like growth factor (IGF-1) and BMPs
Inhibited by fibroblast growth factor
What stimulates cartilage matrix secretion?
IGF-1 and BMPs
What stimulates chondrocyte hypertrophy? What inhibits it?
Thyroid hormones acting through IGFs and FGFs and through inhibition of parathyroid hormone-related peptide
What does vascular endothelial growth factor stimulate?
Angiogenesis
What stimulates osteoblasts and osteoclast differentiation?
Osteoblasts: BMPs
Osteoclasts: RANKL
A mutation in Aggrecan results in what?
How about FGF4?
Aggrecan—> bulldog dwarfism in dexter cattle
FGF4–> short legs in dogs
What is micromelia?
Poorly developed limb
What is chondrodystrophy? What does it result in?
Disorder of bone growth due to primary lesions in growth cartilage. Results in disproportionate dwarfism.
What are some examples of chondrodysplasia?
Spider lamb syndrome (reduced inhibition of chondrocyte proliferation). Autosomal recessive condition
Bulldog calves (dexter and Holstein cattle)
Mushroom shaped long bones in Alaskan malamutes and thickened physes
What is the hallmark lesion of osteochondrosis?
Focal or multi focal retention of growth cartilage due to failure to become mineralised and replaced by bone.
What may cause acquired osteopetrosis?
BVD, FeLV, canine distemper
What are some nutritional causes of osteoporosis?
Vit C, calcium, copper or phosphorus deficiency
Hypoproteinaemia
Hypervitaminosis A
What are some endocrine disorders that may result in osteoporosis?
Hyperthyroidism
Hyperadrenocorticism (glucocorticoids inhibit collagen synthesis and stimulate bone resorption)
What are the two most common causes of rickets?
Vit D deficiency and phosphorus deficiency
Fibrous osteodystrophy is seen with what condition? Why?
Hyperparathyroidism due to increased PTH and hypercalcaemia resulting in widespread mineralisation
What lesions are produced by vit A toxicity?
Physeal damage
Osteoporosis
Exostoses
What are the routes through which infectious osteomyelitis may occur?
Haematogenous
Direct
Extension (locally from adjacent structures)
What are some anatomical factors favouring metaphyseal localisation of infectious osteomyelitis?
Capillaries make sharp loops
Capillaries are fenestrated and cause slow blood flow, thrombosis and necrosis
Phagocytosis in sinusoids is inefficient
Where are osteosarcoma most likely to metastasise?
The lungs
In the dog, what areas are most common,y affected with Marie’s disease?
Radius, ulna, tibia, metacarpals and metatarsals
What is micromelia?
Poorly developed limb
What is chondrodystrophy? What does it result in?
Disorder of bone growth due to primary lesions in growth cartilage. Results in disproportionate dwarfism.
What are some examples of chondrodysplasia?
Spider lamb syndrome (reduced inhibition of chondrocyte proliferation). Autosomal recessive condition
Bulldog calves (dexter and Holstein cattle)
Mushroom shaped long bones in Alaskan malamutes and thickened physes
What is the hallmark lesion of osteochondrosis?
Focal or multi focal retention of growth cartilage due to failure to become mineralised and replaced by bone.
What are some nutritional causes of osteoporosis?
Vit C, calcium, copper or phosphorus deficiency
Hypoproteinaemia
Hypervitaminosis A
What are the two most common causes of rickets?
Vit D deficiency and phosphorus deficiency
Fibrous osteodystrophy is seen with what condition? Why?
Hyperparathyroidism due to increased PTH and hypercalcaemia resulting in widespread mineralisation
What are the routes through which infectious osteomyelitis may occur?
Haematogenous
Direct
Extension (locally from adjacent structures)
What are some anatomical factors favouring metaphyseal localisation of infectious osteomyelitis?
Capillaries make sharp loops
Capillaries are fenestrated and cause slow blood flow, thrombosis and necrosis
Phagocytosis in sinusoids is inefficient
Where are osteosarcoma most likely to metastasise?
The lungs
What may cause acquired osteopetrosis?
BVD, FeLV, canine distemper
What are some endocrine disorders that may result in osteoporosis?
Hyperthyroidism
Hyperadrenocorticism (glucocorticoids inhibit collagen synthesis and stimulate bone resorption)
In the dog, what areas are most common,y affected with Marie’s disease?
Radius, ulna, tibia, metacarpals and metatarsals
Where is the coracoid process located?
Medial aspect of the supraglenoid tubercle
Where are the proximal palmar sesamoids located in the dog forelimb?
Paired set on metacarpophalangeal joints II-V.
Single one on metacarpophalangeal joint I
What are the boundaries of the pelvic inlet?
The promontory (dorsal margin) Cranial border (pecten) of the pubis (ventral margin) Arcuate lines extending from the auricular surface on the medial aspect of the ilium to the iliopubic eminence
What are the boundaries of the pelvic outlet?
Dorsally: first caudal vertebrae
Laterally: sacrotuberous ligament
Ventrally: caudal border of the ischiatic tuberosities and the ischiatic arch
In which species is the radius and ulna fused?
Ox and horse
Where is hyaline cartilage found?
Respiratory tract
Ventral ends of ribs
Articular cartilage
Growth plates of growing long bones.