Key Terminology & Definitions - Pathology Flashcards
Aetiology
Cause of disease
Pathogenesis
Mechanisms (progression from initial stimulus to disease expression) that lead to diseased state in response of cells and tissues to aetiologic agent.
Gross pathology
Recognition and description of macroscopic, morphological changes to tissues and organs in the live or dead animal at biopsy, surgical removal or PM examination.
Antemortem
Before death
Post mortem
After death
The examination of a body after death =
PM examination / necropsy / autopsy
Yellow
Icterus
Pallor
Loss of blood/anaemia
Red-purple
Congestion, sepsis, bruising
Haemorrhage
Green
Bile imbibition, pseudomelanosis (green-black) (bacteria making sulfur compounds (H2S) = smell), some fungi
Gelatinous
Oedema, serous atrophy of fat
Pluck
Trachea, tongue, larynx, thyroids and parathyroids, oesophagus, heart and lungs.
Agonal
Changes that occur at or around time of death
Algor mortis
Cooling of the body after death
Rigor mortis
Contraction of muscles after death (due to lack of ATP, no re-cock of myosin head).
Autolysis
Breakdown of tissue as result of enzymes contained within cells = self-digestion
Putrefaction
Breakdown of tissues by bacteria
Desiccation
Loss of H2O from tissues exposed to the air after death
Livor mortis
Pooling of blood in dependent sites due to gravity
White / grey / yellow
Lack of blood, necrosis, icterus, fibrosis
Black
Melanin (melanosis, flat, melanoma, raised)
Gas (consistency)
Trapped in tissue = emphysema or autolysis
Fluid (consistency)
Looks or feels wet = oedema, blood, transudates, fluid
Soft (consistency)
Fluid rich, cell/stroma poor
Firm (consistency)
Fluid poor, cell/stroma rich
Hard/gritty (consistency)
Mineralised stroma/matrix, cartilage, bone, calcified tissue
Innate immunity
Pre-existing frontline defence that is always there; normal immune system animals are born with (non-specific)
Pathogen-associated molecular patterns (PAMPs)
Molecules with conserved motifs that are associated with pathogen infection that serve as ligands for host pattern recognition molecules such as Toll-like receptors (innate immunity)
Pattern recognition receptors (PRRs)
Recognise PAMPs and target them for clearance
Macrophage
APC - phagocytosis and activation of bactericidal mechanisms
Adaptive immunity) - stimulate already primed effector and memory T-cells (B cells as well
Dendritic cell
APC - antigen uptake in peripheral sites, specialised in activation of naive T-cells
Neutrophil
Phagocytosis and activation of bactericidal mechanisms
Eosinophil
Killing of antibody-coated proteins
Basophil
Promotion of allergic responses and augmentation of antiparasitic immunity
Mast cell
Release of granules containing histamine and active agents
Selectins
Bind carbohydrates and initiate leucocyte-endothelial interaction
Integrins
Bind to cell-adhesion molecules = an extracellular matrix, strong adhesion
Immunoglobulin superfamily
Various roles in cell adhesion, ligand for integrins
Phagocytosis
Engulfment and internalisation of materials such as microbes for their clearance and destruction
The complement system
A group of serum proteins circulating in inactive form, once activated —> target cell membrane lysis, chemotaxis, opsonisation to enhance phagocytosis
Opsonisation
Bacteria are altered by opsonins so as to become more readily and more efficiently engulfed by phagocytes
Enhancement of macrophages and phagocytosis
TLRs
Toll-like receptors (PRR) - innate immunity
CLRs
C-type lectin receptors (PRR) - recognise cell wall components - sugars/polysaccharides of bacteria/fungi
RLRs
Rig-i-like receptors (PRR) - RNA helicases, recognise viral RNAs
NLRs
Nod-like receptors (PRR) - sense bacterial products in products
Epitope
Part of an antigen molecule to which an antibody attaches itself
cDC
Conventional dendritic cells - professional APC, constitute expression of co-stimulatory molecules and stimulate naive T cells
MHC
Major histocompatibility complex that presents antigen to T-cells (MHC I = CD8^+, MHC II = CD4^+)
MHC I
Co-expressed but not covalently linked - CD8^+ (cytotoxic T helper cells = co-receptor)
MHC II
Heterodimer of alpha and beta chain - CD4^+ (T helper cells = co-receptor)
Cytokines
Proteins that mediate the effector functions of the immune system, they have endocrine, paracrine and autocrine actions
Enhance the expression of adhesion molecules in acute inflammation
E.g. TNF and IL-1
Chemokines
Chemoattractants for different leucocytes
Large family of small, secreted proteins that signal through cell surface G protein-coupled heptahelical chemokine receptors
Stimulate the migration of cells, most notably white blood cells (leukocytes)
Large family of cytokines
Many act on granulocytes
Granulocyte
Type of white blood cell that has small granules, containing proteins,
E.g. Neutrophils, eosinophils, and basophils
CD
Cluster of differentiation molecule
Pleiotropy (cytokines)
One cytokine produces multiple effects
Redundancy (cytokines)
More than one cytokine induces the same effect
Synergy (cytokines)
Two (or more) cytokines work together to induce an effect
Antagonism (cytokines)
One cytokine can inactivate the effect of another
IL-1 family (cytokines)
Promote inflammation (most are proinflammatory)
Interferons (INFs)
A group of signalling proteins made and released by host cells in response to the presence of several viruses
TNF
Tumour necrosis factor - cytokine that regulates development, effector function and homeostasis of cells of the skeletal, neuronal and immune systems
Adaptive immune responses
Humoral and cell-mediated responses using B and T lymphocytes, slower to develop and more specific
Antigen
Processed peptide derived from a foreign or altered-self protein and presented by MHC class I (e.g. cytotoxic CD8 t cell) or II (e.g. helper CD4 t cell) May be protein, lipid, carbohydrate, nucleic acid - soluble, particulate, simple or complex
BCR
Membrane-bound immunoglobulin
Antibody
Secreted immunoglobulin
CH regions
Encode for different isotypes (functional classes) of antibodies
Thymocyte
Very early T cell lymphocyte in the thymus
Positive selection
Selects thymocytes bearing receptors capable of binding self-MHC molecules, resulting in MHC restriction
Negative selection
Selects against thymocytes bearing high-affinity receptors for self-MHC/peptide complexes, resulting in self-tolerance