Lesson 4 Flashcards

Question

What diseases are the result of defective collagen synthesis?

Answer 1

``` Acquired • Scurvy Inherited • Ehlers-Danlos syndrome • Osteogenesis imperfecta • Alport syndrome ```

Answer 2

* Vitamin C Deficiency * Inadequate vitamin C dependent hydroxylation of procollagen alpha chains leads to reduced cross-linking and defective helix formation * Lacks strength, vulnerable to enzymatic degradation * Particularly affects collagens supporting blood vessels

Answer 3

* Unable to heal wounds, tendency to bleed * Tooth loss * Collagen in periodontal ligament has short half life and normal collagen is replaced by defective collagen * Old scars break down and open up as fresh wounds * Collagen turnover in scars remains high long after healing process appears clinically complete

Answer 4

* Heterogeneous group of 13 subtypes of inherited disorders * Defective conversion of procollagen to tropocollagen * Collagen fibres lack adequate tensile strength * Wound healing poor * Skin - hyperextensible, thin, fragile and susceptible to injury NB. Skin can recoil because elastic fibres are normal, it is just missing the tethering effect of normal collagen fibres

Answer 5

* Joints – hypermobile, predisposition to joint dislocation * In some forms: * Rupture of colon, large arteries or cornea * Retinal detachment * ‘Rubber people’

Answer 6

* = brittle bone disease, Lobstein’s disease * Too little bone tissue -> extreme skeletal fragility * Affected people - avoid mechanical stress * Some develop severe, progressive deformation of long bones * Blue sclerae – too little collagen within them, translucent * Hearing impairment/dental abnormalities

Answer 7

* Usually X-linked disease -> patients usually male * Type IV collagen abnormal * Dysfunction of glomerular basement membrane, cochlea of ear and lens of eye * Presents with haematuria in children/adolescents progressing to renal failure * Also neural deafness and eye disorders

Answer 8

* Complex/poorly understood processes * Cells communicate with each other to produce a proliferative response * Cell to cell signalling can be via: * Hormones * Local mediators (e.g., growth factors) * Direct cell-cell or cell-stroma contact

Answer 9

* Particularly important in wound healing * Polypeptides that act on cell surface receptors * Coded by proto-oncogenes * ‘Local hormones’ * Bind to specific receptors, stimulate transcription of genes that regulate entry of cell into cell cycle and the cell’s passage through it

Answer 10

* Inhibition of division * Locomotion * Contractility * Differentiation * Viability * Activation * Angiogenesis

Answer 11

* Epidermal growth factor * Vascular endothelial growth factor * Platelet derived growth factor * Tumour necrosis factor * Produced by cells such as platelets, macrophages, endothelial cells * NB: Names can be obsolete or misleading!

Answer 12

Contact inhibition – Signalling through adhesion molecules – Cadherins bind cells to each other – Integrins bind cells to the extracellular matrix Inhibits proliferation in intact tissue, promotes proliferation in damaged tissues Altered in malignant cells

Answer 13

* Descriptions of wound healing related to the size of the wound and the amount of lost tissue * Most often used for skin wounds

Answer 14

* Incised, closed, non-infected and sutured wounds * Disruption of basement membrane continuity but death of only small number of epithelial and connective tissue cells * Minimal clot and granulation tissue

Answer 15

* Epidermis regenerates * Dermis undergoes fibrous repair * Sutures out at about 10 days - approximately 10% normal strength * Minimal contraction & scarring, good strength

Answer 16

* Excisional wound, wounds with tissue loss and separated edges, infected wounds, e.g., infarct, ulcer, abscess * Open wound filled by abundant granulation tissue – grows in from wound margins

Answer 17

* Haematoma: fills gap and surrounds injury * Granulation tissue forms: cytokines activate osteoprogenitor cells * Soft callus: at 1 week, fibrous tissue and cartilage within which woven bone forms * Hard callus: after several weeks, initially woven bone – weaker and less organised than lamellar bone but can form quickly * Lamellar bone: replaces woven bone, remodelled to direction of mechanical stress, bone not stressed is resorbed and outline is re-established

Answer 18

Haematoma -> soft callus -> hard callus -> remodelling

Answer 19

Local factors: 1. Type, size, location of wound 2. Mechanical stress 3. Blood supply 4. Local infection 5. Foreign bodies

Answer 20

General Factors: 1. Age 2. Anaemia, hypoxia and hypovolaemia 3. Obesity 4. Diabetes 5. Genetic disorders 6. Drugs 7. Vitamin deficiency 8. Malnutrition

Answer 21

•Insufficient fibrosis • Wound dehiscence, hernia, ulceration • For example obesity, elderly, malnutrition, steroids •Formation of adhesions • Compromising organ function or blocking tubes e.g., intestinal obstruction following abdominal surgery •Loss of function • Due to replacement of specialised functional parenchymal cells by scar tissue e.g., healed myocardial infarction with non-contracting area of myocardium • Disruption of complex tissue relationships within an organ • Distortion of architecture interfering with normal function e.g., liver cirrhosis • Overproduction of fibrous scar tissue • Keloid scar • Excessive scar contraction • Can cause obstruction of tubes, disfiguring scars following burns or joint contractures (fixed flexures)

Lesson 4 Flashcards

(45 cards)