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medical sciences > Module 1.02 > Flashcards

Module 1.02 Flashcards

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USMLE® Step 1 flashcards
1
Q

what are the cell types in the small intenstine and what are their functions?

A 
enterocytes = absorptive
Goblet cells = mucus
Paneth cells = lysozyme
Enteroendocrine cells = CCK
S cells = secrete secretin
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2
Q

what are peyers patches and where are they found?

A
  • mucousa associated lymphoid tissue (MALT)

- most common in distal illeum

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3
Q

what is the function of brunners glands and where are the found?

A
  • mainly duodenum
  • secrete HCO3-
  • Neutralise
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4
Q

what are the adaptations of the small intestine?

A
  • plicae circulares -> most numerous in jejenum -> forces chyme to spiral
  • villi
  • microvilli
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5
Q

what are the cells found in the large intestine?

A

enterocytes - absorption

goblet cells - mucus

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6
Q

what is the gut flora?

A
  • microorganisms, mostly bacteria, present in a normal healthy individual
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7
Q

what are the effcets of changes in the gut flora?

A
  • changes in general health
  • local trauma
  • hormonal changes
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8
Q

what are the benefits of the flora?

A
  • production of inhibitory substances
  • colonisation causes resistance to virulent bascteria
  • digest nutrient in the bowel
  • resists other colonisation
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9
Q

decsribe a parasite

A
  • behave like a tiny animals, living in or on a host and feeding from it
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10
Q

describe a virus

A
  • made up of genetic code (DNA or RNA) which is coated by a protein
  • invades host cells to divide
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11
Q

describe bacteria

A

made of a single cell

- live anywhere, only pathogenic bacteria cause disease

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12
Q

describe fungi

A
  • cause infection when they over grow, contain nucleus etc

- protected by thick cell walls, makes them hard to kill

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13
Q

How can bacteria be classified?

A

bacteria can be classified as gram positive and gram negative via gram staining

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14
Q

describe the process of gram staining?

A

1) primary staining with CV which penetrates the cell wall making the cell purple
2) grams iodine (I) is added and forms CV-I complex
3) alcohol exposes peptidoglycogen layer
- > in gram positive purple stain stays
- > in gram negative CV-I washed away

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15
Q

characteristics of IgG

A

enhance phagocytosis of bacteria and viruses
most abundant isotype in blood serum
fixes complement and passes to the fetal circulation

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16
Q

characteristics of IgA

A
  • provides localized protection on mucous membranes
  • found in secretions such as saliva, tears and mucous
  • transported across the interior of the cell via transcytosis
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17
Q

which T-cells produce CD 4 and CD 8

A

Helper T cells : express CD4

Cytotoxic T cells: express CD 8

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18
Q

characteristics of IgE

A

-least abundant isotype in blood serum
provides immunity to parasites such as helminths
-mediates type 1 hypersensitivity reactions
binds to Fc receptors found on the surface of mast cells and basophils

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19
Q

what are the 4 layers of the gastrointesinal tract from the lumen out?

A
  • mucousa
  • submucousa
  • muscle
  • serosa
20
Q

what are 3 adaptations for absorption in the small intestine?

A

Plicae circulares - folds in lining, causes chyme to spiral and contact all parts of epithelium lining
Villi - projection of lamina propia (part of mucousa layer)
Microvilli - projections of absorptive cell membranes, forms brush border

21
Q

what is protein broken down to in the stomach?

A

protein becomes peptide fragments with pepsin as the enzyme

22
Q

what digestive enzymes are found in the small intestine to breakdown proteins?

A
  • trypsin, chymotrypsin and elastase (cleave specific peptide bonds)
  • carboxypeptidase (cleaves the carboxyl end of the peptide)
23
Q

how are proteins digested in brush border, which digestive enzymes are involved?

A
  • Aminopeptidases cleaves the terminal amino acid

- Dipeptidase cleaves amino acids

24
Q

how is starch broken down in the upper GI tract (enzyme and products) ?

A

enzyme: salivary/ pancreatic enzymes
products: maltose, maltotriose, a-dextrins

25
Q

what enzymes involved in the digestion of starch are present in the brush border of the small intestine?

A
  • maltase
  • a-dextrinase
  • sucrase
  • lactase
26
Q

what enzymes are involved in the breakdown of triglycerides and what are the products? (in both stomach and small intestine)

A

Stomach:
- enzyme: lingual/ gastric lipase
- products: monoglyceride and 2 fatty acids
Small intestine:
- enzymes: pancreatic lipase
- products: monoglyceride and 2 fatty acids

27
Q

what enzymes are involved in breakdown of nucleic acids in the small intestine and what are the products?

A

enzyme: deoxyribonuclease, ribonuclease
product: nucleotide

28
Q

what enzymes are involved in the breakdown of nucleotides in the brushborder of the small intestines and what are the products?

A

enzyme: nucleosidases/phosphatases
products: Pentose, Phosphate, Base

29
Q

what are the 3 functions of the large intestine?

A

1) absorption of water and ions
2) storage of faeces
3) maintenance of gut flora - mainly gram negative and anaerobic
- most common organism= bacteriodes fragillis

30
Q

describe the innervation of the musculature of the GI tract

A

The muscle layers are innervated by intrinsic nerves of the myenteric plexus that receive branches from the submucosal plexus and parasympathetic vagal nerves from the medulla.

31
Q

describe the electrical and conctractile activity of gastric smooth muscle

A
  • rythmic contractile activity driven by pacemaker cells in the greater curvature of the stomach
  • this is driven by fluctuations in the membrane potential of muscle known as slow waves (does not depend on input)
  • if threshold is reached muscle will contract and electrical activity spreads in a circular motion causing a band of contraction
32
Q

what type of gastric smooth muscle does charge pass through more quickly?

A
  • electrical coupling between smooth muscle cells is faster in the circular than in the longitudinal direction
33
Q

where are pancreatic enzymes synthesised?

A
  • in the rER of acinar cells
34
Q

where are the myenteric plexus and the meissener plexus found in layers of GI tract and hoe does this effect its function?

A

myenteric plexus: inbetween longitudinal and circular layer of muscle and is responsible for gut motility
messiner plexus: found in submusocusal layer and is reponsible for absorption and secretion

35
Q

what are the pacemaker cells of the GI tract?

A
  • ICCs (interstitial cells of Cajal)
36
Q

how does fluid move between compartments?

A
  • Hydrostatic Pressure
  • Oncotic pressure
  • Net fluid movement
37
Q

how odes hydrostatic pressure and oncotic pressure differ?

A
  • they are two competing forces
  • hydrotatic pressure pushes water out
  • oncotic pressure pulls water in
38
Q

how does oncotic pressure act on capillaries?

A
  • Water moves by osmosis from an area of low oncotic pressure to high oncotic pressure
  • Interstitial fluid contains less protein than blood – lower oncotic pressure
  • Water PULLED back into capillaries
39
Q

How does hydrostatic pressure work on capillaries?

A
  • Water moves from an area of high hydrostatic pressure to low hydrostatic pressure
  • High blood hydrostatic pressure in capillaries
  • Low interstitial hydrostatic pressure
  • Water PUSHED from capillaries to tissues
40
Q

how can net pressure be calculated?

A

(HP in caplillary - HP in surround tissue) - ( OP from plasma protein - OP from protein in ISF)

41
Q

what are 3 assumptions for net pressure to be correct?

A

1) proteins dont cross the capillary wall
2) Hydrostatic pressure is constant
3) water flows freely across the capillary wall

42
Q

What is the difference between gram positive and gram negative bacteria?

A
  • gram positive cell walls have a thick peptidoglycan layer and a cell membrane
  • gram negative have 3 layers: inner and outter membranes and a thinner petidoglycan layer
43
Q

how can bacteria be identified? (7)

A
  • gram reaction
  • cell shape
  • endospore
  • fastidiousness
  • key enzymes
  • serological reactions
  • DNA sequences
44
Q

what 3 bacteria are found in the normal flora of the small intestine?

A
  • enterobacteriaceae
  • enterococci (e.coli)
  • candida
45
Q

what 4 bacteria are found in the normal flora of the lower bowel (larger intestine) ?

A
  • bacteriodes
  • bifidobacteria
  • clostridium
  • peptostepdococci
46
Q

what are the main differences between prokaryotic and eukaryotic cells?

A
  • prokaryotes are smaller
  • prokaryotes have no nucleus
  • prokaryotes are unicellular and eukaryotes are multicellular
  • prokaryotes dont have : ER, golgi apparatus, vacuole
  • in prokaryotes chlorophyll is scattered in the cytoplasm

medical sciences (11 decks)

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