Basic Science For Mrcs

Front 1

Definition of cell death

Back 1

Irreversible loss of cell's ability to maintain independence form environment

Front 2

Two major forms of cell death

Back 2

apoptosis

necrosis

Front 3

Necrosis vs. Apoptosis

Back 3

Necrosis - cellular/tissue death in living organism

Apoptosis - energy dependent process for deletion of unwanted individual cell

Front 4

Name six different types of necrosis

Back 4

Coagulative

Colliquative

Caseous

Gangrenous

Fibrinoid

Fat

Front 5

Coagulative necrosis - defintion

Back 5

Denaturation of intracytoplasmic proteins

Dead tissue will initially become firm and swollen but later soft (e.g. venticular rupture after MI)

Typically occur in ischaemic injury (NOT the brain)

Front 6

Colliquative necrosis - definition

Back 6

Seen in brain, probably due to lack of supporting stoma

Necrotic brain tissue liquefies

Glial reaction at periphery with cyst formation occurs eventually

Front 7

Caseous necrosis - definition

Back 7

Typically in TB

Macroscopically cheese-like

Microscopically structureless

Front 8

Gangrenous necrosis - definition

Back 8

Necrosis with putrefaction of tissues due to certain bacteria e.g. clostridia, strep

Tissue is black due to iron sulphide from degraded Hb

Front 9

Fibrinoid necrosis - definition

Back 9

Associated with malignant hypertension

Necrosis of arteriole SM wall with seepage of plasma into tunica media and deposition of fibrin

Smudgy eosinophilic appearance on H+E sections

Front 10

Fat necrosis - definition

Back 10

Direct trauma to adipose tissue and extracellular liberation of fat

Enzymatic lysis of fat by lipase, splitting fat into fatty acid which combines with Ca to precipitate as soaps

Front 11

Function of apoptosis

Back 11

Morphogenesis (elimination of cells in embryonal development)

Removal of cells which have undergone DNA damage

Removal of virally infected cells

Tolerance to self-antigens by removing autoreactive T cells

Front 12

Four mediators of apoptosis and function

Back 12

p53 - tumour suppressor gene which checks integrity of genome prior to mitosis. Switches cells with damaged DNA into apoptosis

BCL-2 - inhibits apoptosis. bcl-2 is overexpressed in neoplasia

fas (cd 95) - plasma membranee receptor which when activated is coupled to the activation of intracellular proteases

Caspases - present in all cells and unless inhibited will lead to apoptosis

Front 13

Describe process of apoptosis

Back 13

Cell shrinkage + chromatin condensation --> membrane blebbing --> continued blebbing + nuclear collapse -->apoptotic body formation --> lysis of apoptotic bodies

Front 14

Disease of increased apoptosis

Back 14

HIV

Neurodegenerative diseases

Front 15

Disease of decreased apoptosis

Back 15

Neoplasia

Autoimmune disease

Front 16

regeneration vs repair

Back 16

Regeneration - total healing of wound with restitution of original tissue in their usual amounts, arrangements and normal function

Repair - original tissue is not totally regenerated defect is made good to a variable extent by scar tissue

Front 17

Describe different levels of potential for cell renewal

Back 17

Labile cells - good capacity for regeneration e.g. surface epithelial cells continuously being replaced from deeper layers e.g. skin oesophagus, vagina

Stable cells - replaced by mitotic division of mature cells and lost cells rapidly replaced e.g. liver, renal rubular epithelium

Permanent cells - never divide in post natal life e.g. nerve cells, myocardial cells

Front 18

Summary of process of repair of tissue

Back 18

Fibrinous exudate --> removal of fibrin and dead tissue and phagocytes --> migration of fibroblasts and capillaries forming granulation tissue --> replacement of exudate by vascularised fibrous tissue --> collagen rich scar

Front 19

What is granulation tissue

Back 19

Combinatino of capillary loops and myofibroblasts

Front 20

Process of granulation

Back 20

Angiogenesis

Migration and proliferation of fibroblasts (secrete collagen and matrix component)

Fibroblasts become myofibroblasts by acquiring muscle filaments

Wound contraction

Front 21

Describe healing by 1st intention

Back 21

Healing by 1st intention (incised surgical wound)

- Edges of incision apposed

- Fibrin sticks edges together

- Capillaries bridge tiny gaps

- Fibroblasts invade fibrin network

- After 10 days wound is strong, suture removed, remodelling occurs

Front 22

Describe healing by 2nd intention

Back 22

Healing by 2nd intention e.g. wound left open (e.g. infected) or tissue loss e.g. trauma

- Phagocytes remove any debris

- Formation of granulation tissue at base of wound

- Myofibroblasts cause wound contraction

- Centripetal growth of epithelium from edges to cover defect

- Tissue deficit eventually made good by scar issue

Front 23

Name 2 abnormalities of skin healing

Back 23

Keloid = Excessive fibroblast proliferation and collagen production

Collagen deposition beyond and above the wound itself

Hypertorphied scar - wound broad and riased, does not extend beyond wound. Usually settles spontaneously in up to 18 months

Front 24

Nam the seven ladders of the reconstructive ladder

Back 24

Primary closure

Delayed primary closure

Split-thickness skin graft

Full thickness skin graft

Local/random pattern flap

Regional/pedicled flap

Free flap

Front 25

Definition of graft

Back 25

Composed of skin but may contain variety of tissue incl. skin, cartilage, tendon, bone or combination of above

NOT transferred with own vascular supply and depends on formation of new vascular system at new site

Front 26

Name different types of graft

Back 26

autograft - own tissue

Allograft - e.g. cadaver bone

xenograft - e.g. animal tendon

Front 27

Full thickness skin graft vs split thickness

Back 27

full thickness - epidermis and all of dermis

split thickness - epidermis and variable thickness of dermis

Front 28

Mechanism of skin graft

Back 28

Adherence - fibrin bonds graft to recipient site, occurs in <12 hours

Plasmic imbibition - graft absorbs essential nutrients from recipient site, occurs at 24-48 hours

Inosculation - revascularisation of the graft via growth of vascular buds, occurs at 48-72 hours

Front 29

Common donor sites for split skin grafts

Back 29

thighs

buttocks

upper arms

Front 30

Which takes better at recipient site - split vs full thickness skin graft and why?

Back 30

Split as thinner helping survive imbibition process

Front 31

Which one results in more contraction at recipient site - split vs full thickness skin graft

Back 31

split thickness

Front 32

Common donor sites for full thickness skin graft

Back 32

Groin

pre/post auricular area

Supraclavicular region

Front 33

Definition of flap

Back 33

unit of tissue transferred with own blood supply

Front 34

What are flaps used for?

Back 34

- large defect

- places where graft would produce poor cosmetic outcome e.g. face

- where base of defect would not support a graft e.g. bare bone, exposed tendon or poorly vascularised bed