TOB Flashcards
1
Q
What is the meaning of the term tissue?
A
A collection of cells specialised to perform a particular function
2
Q
What is an organ?
A
An aggregation of tissues
3
Q
What are the different types of tissue classification?
A
Epithelial tissue
Connective tissue
Muscle tissue
Nervous tissue
4
Q
Why is histology important?
A
It is the gold standard of diagnosis
5
Q
What is the relationship between milli-, micro- and nanometers?
A
m = 1000mm = 1^9nm Millimetre = 10^-3m Nanometer = 10^-9m
6
Q
How big is a normal cell?
A
10-20 micrometers (1 micrometer = 10^-6m)
7
Q
How big is a red blood cell?
A
7.2 micrometers (1 micrometer = 10^-6m)
8
Q
What are the common biopsy techniques?
A
Smear - cervix or buccal cavity Curettage - endometrial lining of uterus Needle - brain, breast, liver, kidney, muscle Direct incision - skin, mouth, larynx Endoscopic - lung, intesting, bladder Transvascular - heart, liver
9
Q
What is a biopsy?
A
The removal of a small piece of tissue from an organ or part of the body for microscopic examination
10
Q
Why does tissue need to be fixed and state which fixtures are commonly used?
A
Preserve cellular structure, no autolysis or putrefaction
Glutaraldehyde, formaldehyde
11
Q
What are the common stains and what do they stain?
A
Haematoxylin - stains acidic components purple/blue (e.g. RNA, DNA)
Eosin - stains basic components pink (e.g. cytoplasmic proteins, extracellular fibres)
Periodic Acid-Schiff (PAS) - stains carbohydrates and glycoproteins magenta
12
Q
Define epitheila
A
Sheets of contigous cells, of varied embryonic origin, that cover the external surface of the body and line internal surfaces
13
Q
What are the different types of epithelia?
A
Simple squamous, cuboidal & columnar
Pseudostratified
Stratified squamous, cuboidal, columnar and transitional
14
Q
What is the basement membrane?
A
Thin, flexible, acellular layer that lies between epithelial and subtending connective tissue to which the epithelial cells adhere
15
Q
Give an example of where simple squamous epithelia are located and their functions?
Little bears play ball - little grey active bears
A
Squamous - Lining of vessels (Endothelium), linings of body cavities (pericardium, pleura, peritoneum), pulmonary alveoli, bowman’s capsule (kidney)
Functions: Lubrication, active transport, barrier, gas exchange
16
Q
Give an example of where simple cuboidal epithelia are located and their functions?
The secret’s out kid - her majesty’s secret army boys
A
Thyroid follicles, small ducts of exocrine, kidney tubles, ovary surface
Function: Hormone synthesis, storage and mobilisation, absorption and secretion, barrier/covering
17
Q
Give an example of where simple columnar epithelia are located and their function?
Slog us - and surrender to love
A
Stomach, small and large intestine, gallbladder, large duct exocrine glands, oviducts, uterus
Function: Absorption, secretion, lubrication, transport
18
Q
Give an example of where stratified squamous epithelia are located and their functions?
4 P’s
A
Keratinised - Skin
Functions: Protection against abrasion, prevents water loss, prevents invasion of microbes, protects against UV rays
Non-keratinised - Mouth, larynx, anal canal, corneal surface, vagina
Functions: Protect against abrasion, reduce water loss but remains moist
19
Q
Give an example of where stratified cuboidal epithelia are located and their functions?
Weights stacked up at gym
A
Sweat glands
Function: protection, secretion
20
Q
Give an example of where stratified transitional epithelia are located and their functions?
A
Bladder, ureters, renal calyces
Function: protection, distensibility
21
Q
Give an example of where stratified columnar epithelia are located and their functions?
A
Conjuctiva
Function: protection
22
Q
Give an example of where pseudostratified epithelia are located and their functions?
Tiny naughty bears are terrible - caps
A
Nasal cavity, trachea, bronchi, auditory tube, tympanic cavity
Function: protection, secretion, cilia-mediated transport of particles trapped in mucus, absorption
23
Q
What is the rate of renewal for the skin and the small intestine?
A
Skin - 28 days
Small intestine - 4-6 days
24
Q
Define a gland
A
An epithelial cell or collection of cells specialised for secretion
25
How can glands be classified?
By destination of secretion
By structure of gland
By nature of secretion
By method of discharge
26
What is the difference between an endocrine and exocrine gland?
Endocrine - ductless glands which secrete into bloodstream
| Exocrine - glands with ducts
27
What are the difference structure classifications of glands?
Unicellular/multicellular
Acinar/tubular
Coiled/branched
and
```
Simple gland (single duct)
Compound gland (branched ducts)
```
28
Describe the two types of secretions
Mucous - contain mucus, rich in mucins (highly glycosylated polypeptides)
Serous - secretions (often enzymes) are water, free of mucus. Stain pink in H&E
29
Describe the different methods of secretion
Merocrine - Exocytosis
Apocrine - Non-membrane dound structure approaches cell surface and pushes it up making a think layer of membrane and cytoplasm surround it, then pinches off
Holocrine - Disintegration of cell, releases contents, discharge of whole cell
30
Describe the process of exocytosis
Proteins and lipids are packaged into vesicles within the RER.
Travel through the Golgi, cis-medial-trans, where modifications occur.
Secreted either through regulated or constitutive pathways
31
Describe the glycocalyx and how destruction affects its function
Glycocaylx is the extracellular glycoprotein on epithelial and other kinds of cells.
Branching sugars on it offer complex shapes for specific interactions
Destruction alters:
1. Adhersion to substrates and neighbouring cells
2. Mobility of cells
3. Communication with neighbouring cells
4. Contact inhibition of movement and division
32
What are the different controls of secretion? (4)
Nervous
Endocrine
Neuroendocrine
Negative feedback
33
Where are mucous membranes found?
Line certain internal tubes which are open to the exterior
| e.g. alimentary tract, respiratory tract, urinary tract
34
What are the layers of a mucous membrane?
Epithelium
Lamina propria
In alimentary tract muscularis mucosae
This is all known as the mucosa
35
Where are serous membrane found?
They are thin, two part membranes which line certain closed body cavities
e.g. peritoneum, pleural sacs, pericardial sacs
36
What does a serous membrane consist of?
Simple squamous epithelium (mesothelium), visceral serosa and parietal serosa
Thin layer of connective tissue (attaches epithelium to adjacent tissues)
37
What are the layers of the gut? (4)
Musoca (epithelium, lamina propria, muscularis mucosa)
Submucosa - connective tissue containing glands, arteries, veins and nerves
Muscularis externa - 2 layers, longitudinal & circular
Serosa - peritoneum
38
What are the layers of the oesophagus? (4)
Mucosa (epithelium, lamina propria, muscularis mucosa)
Submucosa - containing mucous secreting glands
Muscularis externa - 2 layers, longitudinal & circular
Adventitia - connective tissue
39
What are the layers of the stomach? (3)
| What does the stomach contain that is unique?
Mucosa (epithelium, lamina propria, muscularis mucosa)
Submucosa
Muscularis externa - 3 layers, obilque, circular, longitudinal
Contains rugae (folds of gastric mucosa)
40
What does the jejunum have that is unique?
Contains plicase circulares - circular folds of mucosa and submucosa projecting into gut lumen
41
What does the large intestine have that is unique?
Crypts of Lieberkuhn (gland in the epithelial lining)
42
What are the layers of the trachea? (4)
Mucosa - epithelium, lamina propria
Submucosa - containing seromucosa glands
Hyaline cartilage - calcifies with age
Adventitia - connective tissue
43
What are the layers of bronchus (3), bronchiole and alveoli?
Bronchus:
Mucosa - epithelium, smooth muscle lamina propria
Submusoca - contains glands
Cartilage
Bronchiole does not have cartilage or submucosa
Alveoli do not have submucosa or muscle - they are covered in a network of elastic fibres and capiliaries (epithelium, basement membrane)
44
What are the layers of the ureter? (2)
Mucosa - epithelium, fibroelastic lamina propria
| Muscularis externa - circular
45
What are the layers of the bladder wall? (2)
Mucosa - epithelium, smooth muscle in lamina propria
| Muscularis externa - 3 interwoven layers
46
What are the layers of the urethra? (3)
Mucosa - epithelium, lamina propria
Muscularis externa - 2 layers, longitudinal and circular
Adventitis
47
How does a transmission electron microscope work?
Heated filament (electron source) is passed through specimen onto fluorescent screen (condenser lends, objective lens and projector lens required)
48
Define the limit of resolution
The minimum distance at which two objects can be distinguished
49
Why are electron microscopes capable of finer resolution than light microscopes?
Limit of resolution proportional to wavelength
Resolution improves as wavelength decreases
Electron wavelength = 0.004nm
Light wavelength = 400nm
50
Describe the following components of a cell's ultrastructure:
Plasma membrane, glycocalyx, nucleus, nuceolus, nuclear envelope, SER, RER, ribosomes, Golgi, secretory vesicles, lysosomes, peroxisomes, mitochondria, cytoskeleton
Plasma membrane - bilipid membrane, amphipathic, impermeable barrier to water-soluble molecules, contains proteins
Glycocalyx - polysaccharide side chains on outside of the plasma membrane
RER & SER - site of protein synthesis
Ribosomes -
Golgi - modification, packaging and sorting of proteins synthesised on RER (cis-trans)
Secretory vesicles - contain proteins for secretion extracellularly
Lysosomes - synthesised by golgi and contain many hydrolytic enzymes - fuse with material requiring digestion
Peroxisomes - Detoxify molecules including alcohol phenols, formic acid and formaldehyde
Mitochondrial - contain folds called cristae, generate ATP by oxidative phosphorylation, contain their own genetic information and can divide (inherited maternally)
Cytoskeleton - contains microfilaments of actin, epithelia cells contain intermediate filaments, Microtubules are hollow cylinders found in structures that are moved
51
What is a connective tissue?
Forms a continuum throughout the body, linking together muscle, nerve and epithelial tissue. Also provides support in metabolic and physiological ways
52
What are the function of connective tissues? (CADDIS)
1. Provide cushion between tissues and organs
2. Attach muscle to bone, and bone to bone
3. Provide a medium for diffusion of nutrients and wastes
4. Defend against infection
5. Aid in injury repair
6. Provide substance and form to body and organs
53
What are the components of connective tissue?
1. Cells
| 2. Extracellular matrix: ground substance (hyaluronate proteoglycan aggregates), fibres (collagen, reticular, elastic)
54
In terms of connective tissue which cell lines are derived from mesenchyme cells (embryonic connective tissue)
```
Chondroblasts (cartilage)
Lipoblasts (fat)
Fibroblasts (ligament, tendons, capsules, general supporting tissues)
Osteoblasts (bone)
Myoblasts (skeletal muscle)
```
55
What is reticulin and where is it found?
Fibre present in connective tissue - type 3 collagen
| Lymph node
56
How can connective tissue be classed?
Loose
Dense: regular & irregular
Specialised
57
What are elastic fibres made from?
Elastin make up elastic fibres but are surrounded by microfilbrils called fibrillin
58
What is the composition of loose irregular connective tissue?
Wispy collagen (non-branching) and many fibroblasts
Branching elastic fibres
Mast cells
e.g. lamina propria between crypts of lieberkuhn, submucosa of colon, areolar
59
What is the composition of dense irregular connective tissue?
Densely packed collagen in irregular arrangement (resists forces in multiple directions), fewer fibroblasts, some elastic fibres
e.g. dermis
60
What is the composition of dense regular connective tissue?
Collagen bundles that lie in parallel, densely packed
Rows of elongated flattened fibroblasts lie between
e.g. Tendons, ligaments
61
What is the function of fibroblasts?
Synthesise and secrete both ground substance and fibres that lie within the ground substances
62
What is the function of macrophage?
Derived from blood monocytes which move into loose connective tissue, especially during local inflammation.
Phagocytic - degrade foreign organisms and cell debris
63
What is the function of mast cell?
Found near blood vessels Contain granules of heparin, histamine, substances that attract eosinophils, neutrophils - secretion results in immediate hypersensitivity reactions, allergy and anaphylaxis
64
What are specialise connective tissue?
Adipose tissue, blood, cartilage, bone, lymphatic tissue, heamopoietic tissue
65
What are the layers of the epidermis?
Stratum corneum
Granular layer
Prickle cell layer
Basal layer
66
How does the epidermis proliferate?
Keratinocyte mitosis occurs at basal layer
Upward movement to form prickle layer where terminal differentiation begins and kerationcytes lose ability to divide, joined by desmosomes (intercellular junctions)
In granular layer keratinocytes lose plasma membrane and begin differentiating into corneocytes
Stratum corneum contains flattened corneocytes (barrier)
67
What do keratinocytes synthesise and what is it's function?
Keratins - strengthen epidermis
68
What other cells are present in the epidermis?
Melanoctyes - produce melanin (pigment of skin), occur at intervals along basal layer
Langerhans cells - mediate immune reactions, scattered throughout prickle cell layer, presented antigens to T lymphocytes
69
Describe the structure of the dermis
Tough, fibrous, vascular layer
| Contains collagens, type 1, elastin, fibroblasts, blood vessels, lymphatic vessels, mast cells, nerves
70
What are the skin appendages?
Hair follicles
Sebaceous glands
Sweat glands - exocrine, apocrine
Nails
71
What are the main functions of skin?
Barrier function
Sensation
Thermoregulation - thermoregulatory exocrine sweating
Psychosexual communication
72
What is the composition of cartilage?
Extracellular matrix produced and maintained by chrondrocytes, composed of hyaluronate proteoglycans aggregate and type 2 collagen
73
What are the three major types are cartilage
Hyaline
Elastic
Fibrocartilage
74
What is the composition of hyaline cartilage? Give an example of where it is found
Matrix: Proteoglycans, hyaluronic acid and type 2 collagen
Chondrocytes lie in lacuna (small clusters called isogenous groups)
Covered by perochondrium containing fibroblast-like cells which can develop into chrondrocytes
Calcifies with age
Location: Articulating surfaces (no pericondrium), joints, rib cage, nose, trachea, bronchi, larynx, epiphyseal growth plate
75
What is the composition of elastic cartilage? Give an example of where it is found
Proteoglycans, hyaluronic acid, type 2 collagen and many elastic fibres - gives elasticity
Locations: pinna, external meatus, epiglottis, eustachian tube
76
What is the composition of fibrocartilage? Give an example of where it is found
Combination of dense regular connective tissue and hyaline cartilage
Type 1 collagen plus proteoglycans, hyaluronic acid and type 2 collagen
No surrounding perichondrium
Cells often seen in rows
Locations: intervertebral discs, articular discs of sternoclavicular & temporomandibular joints, menisci of knee
77
What is the difference between appositional and interstitial growth of cartilage?
Appositional - grows from periphery (fibroblast-like cells give rise to new chondroblasts)
Interstitial growth - Deposition of matrix by isogenous groups of chondrocytes
78
What is the function of Haversian and Volkmann's canals?
Carry blood vessels, lymph vessels and nerves
Haversians run vertically
Volkmann's run horizontally
79
What is the difference between immature and mature bone?
Immature bone has osteocytes with are fairly randomly arranged
Mature bone has osteocytes arranged in concentric lamellae of osteons
80
What is the structure of spongy (cancellous) bone?
Trabeculae - spaces for bone marrow
Osteocytes lie in-between lamellae
No Haversians or Volkmann's
81
Explain the function of osteoblasts and osteoclasts
Osteoblasts - deposit new bone
| Osteoclasts - resorbing bone to remodel (cuts a tunnel through bone)
82
What is endochondral ossification?
Replacement of pre-existing hyaline carrilage template by bone
83
Describe the steps in endochondral ossification
1. Collar pf periosteal (compact) bone appears in shaft (embryo 6-8 weeks)
2. Central cartilage calcifies, nutrient artery penetrates - primary ossification centre formed (fetus 8-12 weeks)
3. Medulla becomes cancellous bone (middle/shaft), cartilage forms epiphyseal growth plates, epiphyses develop secondary centres of ossification (postnatal)
4. Epiphyses ossify and growth places continue to move apart (prepubertal)
5. Epiphyseal growth plates replaced by bone, hyaline articular cartilage persists (mature)
84
Describe intramembranous ossification
Condensations of mesenchymal tissue to form flat bones
85
Describe the effects that growth hormone has on growth of bone
Growth hormone
Before puberty - excess causes gigantism, insufficient causes pituitary dwarfism
Adult - excess causes acromegaly
86
Describe the effects that sex hormones has on growth of bone
Sex hormones influence development of ossification centres
Give rise to pubertal growth spurt, premature closure of epiphyses
Deficiency can cause tall stature - epiphyseal pleats persist
87
What is the role of vitamin D in bone?
Increases calcium absorption by the small bowel
| Promotes mineralisation of bone
88
What are the three types of muscle?
Striated muscle - skeletal & cardiac
| Non-striated muscle - smooth
89
What are the two types of skeletal muscle fibres?
Red - Smaller, myoglobin rich, numerous mitochondria, slow/repetitive contraction, slow to fatigue, fewer neuromuscular junctions
White - opposite
90
Describe skeletal muscle structure
Epimysium surrounds muscle
Fascicles make up muscle - surrounded by permysium
Fascicles made up from fibres - surrounded by endomysium
Fibres made up from myofibrils - surrounded by sarcolemma
Myofibrils made up from sarcomere
91
Describe the structure of sarcomere
```
ZIAHM
Z disc - actin filaments join
I band - actin filaments where myosin does not overlap
A band - where myosin lie
H band - area between actin filaments
M line - central C protein
```
92
Explain how calcium causes contraction
Calcium binds to C subunit of troponin which causes a conformation change moving tropomyosin away from actin binding sites - allowing myosin heads to bind to actin
93
Explain the sliding of actin during contraction
1. ATP binds to myosin head causing it to uncouple from actin filament
2. Hydrolysis of ATP to ADP causes bending of head
3. Release of Pi and ADP causes power stroke
94
Explain how muscles are innervated
1. Action potential causes release of acetylcholine into synaptic cleft of neuromuscular junction causing local depolarisation
2. Voltage-gated Na+ channel open
3. General depolarisation spreads over sarcolemma and down T tubules
4. Voltage sensor proteins of T tubule membrane change conformation
5. Gated Ca2+ channels open and Ca2+ enters sarcoplasm
6. Ca2+ binds to TnC subunit of troponin
95
What is the difference between cardiac muscle and skeletal muscle?
Centrally placed nuclei
Intercalulated discs - where Z bands meet
Branching
T tubules lie in register with Z bands and is a diad rather than triad
Unable to regenerate - lays down scar tissue
96
Describe the composition of Purkinje fibres
Abundant glycogen
Sparse myofilaments
Extensive gap junction sites
Connect sinoatrial note to atrivoventricular node
97
Describe features of smooth muscle
```
Spindle-shaped
Central nucleus
No striation, sarcomeres or t-tubules
Contaction still relies on actin-myosin interactions (criss-crossed along spindle)
Contraction is slower, more sustained
```
98
What are the meninges of the brain and spinal cord? (DAP)
1. Dura mater
2. Arachnoid mater
3. Pia Mater (innermost)
99
What does leptomeninges refer to?
The arachnoid mater and pia mater when taken together - cerebrospinal fluid flows within the leptomeninges
100
Describe the structure of a nerve?
Epineurium surrounds the nerve in which there are nerve fascicles
Perineurium lines nerve fascicles which contain a collection of axons
Endoneurium surrounds an axon
101
What is a neurone?
A specialised functional unit of the nervous system
| Includes cell body (with extending dendrites) and axon
102
What is the function of dendrites?
Increase surface area of the cell body
| Some can develop further appendages called spines - They are associated with learning experiences
103
Describe the componens of an axon
Myelin sheath - Schwann cell wrapped around - increases action potential speed
Node of Ranvier - where there is no myelination
Axonal terminal
104
How do neurones communicate? What is the difference between excitatory and inhibitory signals?
Submicroscopic gaps called synapses through neurotransmitters
Excitatory - depolarisation
Inhibitory - hyperpolarisation
105
What are the functional classes of neurones?
Sensory neurones
Motor neurones
Interneurones
106
What pathways relays information from the body to the brain?
Afferent - sensory neurones
107
What pathways relays information from the brain to the body?
Efferent - motor neurones
108
What are the divisions of the ANS?
Sympathetic - rest and digest - short preganglionic (terminates in paravertebral sympathetic chain), long postganglionic
Parasympathetic - fight/flight - long preganglionic, short postganglionic
109
What are the neurotransmitters?
Acetylcholine and noradrenaline
110
What the the ANS?
Autonomic nervous system - part of the Peripheral nervous system (outside the brain)
111
Communication between pre- and post-ganglionic sympathetic and parasympathetic neurones is...?
Cholinergic (involves acetylcholine) via nicotinic receptors - parasympathetic
Or
Noradrenergic (noraldreanline)
112
What is the life of a RBC?
120 days
113
What is the life of a platelet?
10 days
114
What is the function of bone marrow?
Produce RBCs, platelets, WBCs from progenitor stem cells
115
What are the functions of RBCs?
```
Deliver oxygen
Carry haemoglobin
Maintain haemoglobin in its reduced state
Maintain osmotic equilibrium
Generate ATP
```
116
Describe how RBCs structure facilitates its function
Biconcave flexible disc facilitates passage through the microcirculation (capillaries)
117
What are the two main metabolic pathways within RBCs?
Embden Meyerhof Pathway - glucose metabolised to lactate (ATP generated)
Hexose monophosphate pathway - glucose-6-phosphate metabolised (generates NADPH)
118
How is erythropoiesis controlled?
Reduced O2 pressure detected in interstitial peritubular cells in kidney
Increased produced of erythropoietin
Stimulates maturation and release of RBCs from bone marrow
Haemoglobin rises
O2 pressure rises
Erythropoietin production falls (negative feedback)
119
How are RBCs catabolised?
RBCs brown down in the spleen to release heam group which is broken down until bilirubin
Bilirubin transported to liver which travels down bile duct into large intestine
120
How are platelets produced?
Megakaryocytes produce platelets - they bud off from the cytoplasm - controlled by thrombopoietin
121
What are the functions of the platelet?
Adhersion to connective tissue
Aggregation with other platelets
Phospholipid membrane to facilitate clotting (glycoprotein receptors for clotting factor and platelet adhersion)
122
What is the function of neutrophils? What do they release?
Phagocytosis - first arrival in inflammatory response
Once granules are used up they die
Chemokines - attacts more phagocytes
123
What is the function of monocytes?
Mature into macrophages in tissues
124
What is the function of eosinophils?
Degranulating cells - release heparin, histimine
| Involved in allergy and asthma
125
Which cells undergo degranulation?
Mast cells, eosinophils, basophils
126
What is the function of basophil?
Degranulation cell - releases histimine and heparin
127
What are the features innate immune system?
```
Inbulit immunity to resist infection
Present from birth
Non-specific
No memory
Involved in the triggering and amplification of adaptive immune response
```
128
What is adaptive immunity?
Immunity established to adapt to infection
Learnt by experience
Pathogen specific
Has memory
129
What is the function of the lymphocyte?
Adaptive immune response (T & B lymphocytes)
| Recognise non-self antigens and generate a specific response to eliminate foreign antigen
130
Which cells are phagocytes?
Macrophages and neutrophils
131
Describe the role of epithelial cells in first line of defence to pathogens
```
Mechanical, selectively permeable barrier
Produce natural antibodies
Produce cytokines
Motile cilia
Rapidly renewable
```
132
What is the complement system?
Marks pathogens for destruction by covalently binding to their surface - activated by sugars on surface of antigen
133
What are the cells of the adaptive immune response? And what do they do?
T helper cells (CD4) - release cytokines which activate cytotoxic T cells & increase activity of phagocytes
Cytotoxic T cells (CD8) - cell-mediated immunity (no cytokines secreted), they secrete interferon
B lymphocytes - receptors can be secreted into intercellular space (immunoglobin or antibody), binds on surface of pathogen, stimulates innate immune system
134
Describe the general scheme of immune response
Pathogens break epithelial barrier
Activated epithelial cells release cytokines
Inflammatory mediators promote endothelium (capillary) to become permeabilised allowing cell and fluid migration (antibodies and complement)
Opsonisation (binding of antibody) to pathogen
Attracting phagocytes for phagocytosis
135
What are the cells involved in innate immunity?
```
Monocytes - macrophages
Neutrophil
Eosinophil
Basophil
Mast cell
Natural killer cells
```
136
Describe the adaptive immune response
Clonal selection - recognition of receptor needed by naive T & B lymphocytes
Clonal expansion - mitotic division (daughter cells)
Elimination of antigen
T & B cell apoptosis
Seeding of memory
137
What is opsonisation?
The coating of a microorganism by antibodies or complement to render it recognisable as foreign by phagocytes - enhancing phagocytosis
138
What are the antigen receptors expressed on lymphocytes?
B cell = surface immunoglobulin (membrane-bound antibody)
T cell = T cell antigen receptor (distinct molecule, not membrane-bound)
Each expresses a single antigen receptor specificity
139
What are the three main ways which antibodies protect the host from infection?
Neutralisation - prevents bacterial adherence
Opsonisation - promotes phagocytosis
Complement activation - enhances opsonisation and lyses some bacteria
140
What is a pathogen?
Microbes that cause human disease
141
What is an infection?
Presence and multiplication in a host of a causal organism in abnormal circumstances and with an associated host reaction
142
Describe the gram stain procedure
Crystal violet is added
Iodine is added
Decolourisation with alcohol/acetone
Counter staining with safranin
143
How does gram staining work?
Crystal violet and iodine are absorbed into cell and form and purple complex
During deolourisation:
Gram -ve loses outer lipopolysaccharide membrane and purple complex is washed away - counter stain then used
Gram +ve becomes dehydrated trapping purple complex
144
What is the difference between gram +ve and -ve bacteria?
Gram +ve has a thick layer of peptidoglycan
| Gram -ve has a thin layer of peptidoglycan with an outer lipopolysaccharide membrane
145
Which type of bacteria cannot be seen using gram stain? What stain is used?
Mycobacteria - acid-fast
146
Which groups of bacteria are gram +ve?
Staphylococcus
Streptococcus
Clostridium
147
Which groups of bacteria are gram -ve?
```
Everything not staph, strept or clostridium
Neisseria
Salmonella
Helicobacter
Pseudomonas
Bacteroides
```
148
Which viruses have DNA and an envelope?
Hepatitis B, herpes viruses, smallpox
149
Which viruses have DNA and no envelope?
Papillomaviruses (warts, cervical cancer)
150
Which viruses have RNA and an envelope?
Rubella, HIV, ortho- & para- myxoviruses (measles, mumps)
151
Which viruses have RNA and no envelope?
Picomaviruses (polio, hepatitis A, colds)
152
What does Koch-henle postulates?
Identification of particular microbe as causing disease
1. Isolate organism from every case
2. Propagate the organism in pure culture in vitro
3. Reproduce disease by injecting the organism into a suitable recipient
4. Re-isolate the organism
153
What are the components in the transmission of infection?
Reservoir - immediate source - mode of transport - susceptible host
154
Describe the pre-ganglionic and postganglionic neurones in the parasympathetic nervous system
Long pre-ganglionic neurone - synapses locally to effector
| Short post-ganglionic neurone - synapses at effector
155
In terms of infection, what is R0?
The basic reproductive rate of an infection after introduction into a susceptible population
R0 >1 - infection propagates
R0 <1 - infection dies out
156
What are the stages of fracture repair?
1. Haematoma formation - blood clot forms in which granulation tissue
2. Fibrocartilaginous callus formation - Fibrocartilaginous callus replaces procallus of granulation tissue (bone trabeculae is developing in callus)
3. Boney callus formation - Endochondral & intramembranous ossification gives rise to a bony callus of spongy bone
4. Bone remodelling - cancellous bone replaced by compact bone
157
Describe the pre-ganglionic and postganglionic neurones in the sympathetic nervous system
Short pre-ganglionic neurone - synapses in spinal column
| Long post-ganglionic neurone - synapses at effector
158
What is interferon?
Interferon is released by cells that have become infected - prevents further cells from becoming infected & switches off cellular machinery necessary for viral replication
