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MBCHB1 exam > Phase 1 week 1 > Flashcards

Phase 1 week 1 Flashcards

1
Q

What are the three main functions of skin?

A

Physical and immunological barrier, physiological regulation, Sensation

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2
Q

In what ways does the skin act as a barrier?

A

Protects against; mechanical impacts, pressure, variations in temperature, micro-organisms (Lymphocytes), radiation

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3
Q

How is the skin involved in physiological regulation of the body?

A

Body temperature via sweat and hair, changes in peripheral circulation, fluid balance via sweat, synthesis of vitamin D

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4
Q

Describe sensation in the skin

A

Network of nerve cells detect and relay changes in the environment (heat, cold, touch, pain)
Itch is a unique feature of the skin

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5
Q

Describe vitamin D synthesis in the skin

A 
During exposure to UV light, UVB photons are absorbed by 7-dehyrocholesterol in the skin and converted to provitamin D(3)
Provitamin D(3) undergoes transformation within the plasma membrane of cells to active vitamin D(3)
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6
Q

What are the layers of the epidermis?

A 
Stratum corneum
Stratum lucidum
Stratum granulosum
Stratum spinosum
Stratum basale
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7
Q

Describe Eccrine glands

A

Everywhere on skin apart from nail bed and lips
secrete sweat
most abundant on palms, soles and axillae

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8
Q

Describe apocrine glands

A

Scent glands, role unclear

Axillae and genitals

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9
Q

Describe sebaceous glands

A

Present everywhere except palms and soles
Enlarge greatly at puberty in response to androgens (acne)
Main function is to provide lipids which lubricate the hair shaft

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10
Q

What is the main type of cell found in the epidermis and what proportion does it make up?

A

keratinocyte - 95%

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11
Q

What types of cell are found in the epithelium?

A

keratinocytes
dendritic cells - langerhans cells
melanocytes

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12
Q

what are the properties of keratinocytes?

A

They form keratinised squamous epithelium
waterproof
protection against friction, microbial invasion and desiccation
Held together by desmosomes - intermediate filaments and cadherins

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13
Q

Describe melanocytes

A

Found in the basal layer of the epidermis

Melanin is transferred to keratinocytes via their dendritic processes

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14
Q

Describe normal skin regeneration

A

Some cells in the stratum basale are stem cells
These can divide to form new stem cells or undergo terminal differentiation as they migrate towards the surface of the skin
It takes 1 month for epidermal turnover
2 weeks from granular layer to stratum corner
2 weeks for the corneocyte to surface the stratum corneum and to be shed to the environment
The epidermis is made up at keratinocytes at different stages of development

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15
Q

What is a wound?

A

The breakdown in the protective function of the skin

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16
Q

What types of wounds are there?

A

Erosion - only epidermis lost
Ulceration - structures deep to epidermis
Partial thickness - epidermis and some dermis
Full thickness - epidermis and all of dermis and deeper structures

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17
Q

What are the 3 phases of wound healing?

A

Inflammation - platelets and WBCs gather
tissue proliferation - epithelialisation and granulation tissue formation
Tissue remodelling

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18
Q

Describe phase 1 of wound healing

A

Platelets arrive first and initiate haemostats and release growth factors
GFs attract other cells to fight infection
New cells migrating to the area cause characteristic signs of inflammation
Neutrophils and macrophages kill microorganisms and secrete more GFs

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19
Q

What are the two part in phase 2 of wound healing?

A

re-epithelialisation and neovascularisation

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20
Q

Describe re-epithelialisation

A

Within 1-2 days of the wound, keratinocytes move from the skin appendages and near the edge of the wound
the cells adapt - they lose their adhesion properties and become flatter
Re-epithelialisation occurs either by the “leap frog” method or the “train method”

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21
Q

Describe neovascularisation

A

Chemotactic factors cause cells to migrate and proliferate
Fibroblasts multiply and lay down collagen in a haphazard way to form a fibrous network that supports new capillary loops
This tissue formed is called granulation tissue
Fibroblasts contract to pull the edges of the wound together

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22
Q

Describe phase 3 of wound healing

A

The collagen is organised into thick bundles and extensively cross-linked to form a mature scar

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23
Q

What factors affect wound healing?

A 
size of wound
blood supply to area
presence of microorganisms
age and health of the patient
Drugs patient takes
nutritional status of the patient
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24
Q

Describe the most common form of staining

A

Haematoxylin and eosin
Most commonly used stain
Basic dye (haematoxylin) to differentiate nuclei
Followed by acidic eosin to highlight everything else

25
Q

How can epithelia be classified in terms of layers?

A

Simple -single layer
stratified - 2 or more layers
pseudo stratified - one layer with a mixture of cell shapes

26
Q

What are different shapes of epithelial cells?

A

squamous - flat
Cuboidal - cube shaped
columnar - tall cylindrical shape
transitional - readily changes shape

27
Q

What are the components of the plasma membrane?

A 
Phospholipid bilayer
cholesterol
lipid rafts
carbohydrates
proteins
28
Q

What is the structure of the phospholipid bilayer?

A

Hydrophilic heads towards the extracellular space and the cell lumen. Hydrophobic tails face inwards.

29
Q

What do integral plasma membrane proteins do?

A

Allow the transfer of small molecules across the membrane through pumps, carriers and channels

30
Q

What do plasma membrane receptors do?

A

They interact with specific chemical signals (ligands) to initiate a cascade of chemical signals in the cell. e.g. EGF receptor

31
Q

How is genomic DNA stored?

A

Packaged as chromatin

32
Q

Describe features of the structure of the nucleus

A

bound by a double membrane, supported by a network of nuclear lamins, contains nuclear pores

33
Q

Describe the compartments within the mitochondria

A

Outer membrane - selective permeability - e.g. pyruvate
Inner membrane - folded into numerous cristae - electron transport chain
Matrix - enzymes for citric acid / TCA cycle
Inter membrane space - important in electron transport chain and other enzymatic reactions

34
Q

Describe the role of the mitochondria in apoptosis

A

Cellular injury / stress leads to the release of Bcl2
release of cytochrome c into the cytoplasm
activation of caspases “proteolytic cascade”
Destroy nuclear lamins
activates DNases
Destroy cell adhesion properties

35
Q

what is the difference between RER and SER?

A

Rough endoplasmic reticulum is associated with ribosomes and is for protein synthesis
Smooth endoplasmic reticulum is not associated with ribosomes and is involved in lipid synthesis and calcium storage

36
Q

Explain the role of the Golgi apparatus

A

Proteins are sent from the ER to the Golgi
They are carried in vesicles and fuse to become the cis cisterna
According to the cis maturation model, the proteins move through the Golgi stack
They undergo enzymatic modification which labels them for their destination
e.g mannose - 6-phosphate is the “address label” for proteins for the lysosome

37
Q

What are lysosomes?

A

Vesicles containing proteolytic enzymes

38
Q

What are endosomes?

A

Vesicles involved in the transport of molecules from the plasma membrane to the lysosomes

39
Q

What are peroxisomes?

A

compartment for enzymes involved in oxidative reactions: biosynthesis of bile acids, fatty acid metabolism, detoxification

40
Q

What are the key differences between lysosomal and proteasomal degradation of proteins?

A

Lysosomal - long half life, membrane proteins, extracellular proteins
Proteasomal - short half life, key metabolic enzymes, defective proteins

41
Q

Give examples of lysosomal enzymes

A

lipases, nucleases, proteases (all of which are activated by an acidic environment )

42
Q

Describe lysosomal degradation

A

Used for proteins with a half-life of >20 hours
membrane proteins via endocytosis
extracellular proteins via receptor-mediated endocytosis
pathogenic proteins via phagocytosis

43
Q

Describe proteosomal degradation

A

Proteins to be removed quickly

Proteins covalently tagged with ubiquitin in a 3-step pathway

44
Q

What does phosphorylation do?

A

Alters the activity of a protein

45
Q

What does acetylation do?

A

In histones - regulation of gene expression

46
Q

What does farnesylation do?

A

targets protein to the cytoplasmic face of the plasma membrane

47
Q

What does ubiquitination do?

A

Targets protein for degradation

48
Q

what are the main function of the cytoskeleton?

A

organise cell structure and to maintain the shape of the cell
supports fragile plasma membrane
provides mechanical linkages that let the cell / tissue bear stress
allows cell to adopt specific behaviours

49
Q

What are the 3 types of cytoskeletal filament?

A

microtubules
Microfilaments
intermediate tubules

50
Q

Give examples of microtubules

A

Tubular (dynein, kinesin)

51
Q

Give examples of microfilaments

A

actin (myosin)

52
Q

Give examples of intermediate filaments

A

keratin, vimentin, desmin, lamins

53
Q

What are the key functions of intermediate filaments?

A

structrural integrity
keratin in epidermis
vimentin in fibroblasts of the dermis
nuclear lamina - nuclear organisation and membrane support

54
Q

What are the key functions of microfilaments?

A

Movement and structural
cell projections - microvilli, stereo cilia
cytoplasm - cell contraction, shape change
Membrane extensions (lamellipodia) cell motility
contractile ring - cytokinesis

55
Q

What are the key functions of microtubules?

A

Mitotic / meiotic chromosomal movement
intracellular vesicle / organelle transport
axonemes composed of microtubules and dyne
Kinesics move cargo away from centrosome
Dyneins move cargo towards the centrosome

56
Q

what are the three types of cell junction?

A

Anchoring
occluding / tight
communication / gap

57
Q

Describe anchoring junctions

A

cell - cell cytoskeleton
adherens - actin
desmosomes - intermediate filaments

cell - ECM contacts
focal adhesions - actin
hemidesmisomes - intermediate filaments

58
Q

Descrive tight junctions

A

cell - cell contact
connect to the actin cytoskeleton
maintain polarity of epithelial cell
form a barrier e.g. blood-brain

59
Q

Describe gap junctions

A

cell-cell contact
composed of hexamers of connexins
allows passage of small molecules

MBCHB1 exam (28 decks)

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