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Revision Year 2 > GIT > Flashcards

GIT Flashcards

1
Q

Type of Cells in Mouth, oesophagus, anal canal

A

stratified squamous

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2
Q

Type of Cells in Stomach, small + large intestine

A

simple columnar

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3
Q

Lamina propria

A

Loose connective tissue (glands, blood/lymph vessels)

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4
Q

enteric nervous system (ENS)

A

Submucosal (Meissners) + Myenteric plexuses

between circular and longitudinal muscles of muscularis externae

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5
Q

What drains the gut?

A

Hepatic Portal Vein

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6
Q

What drains the liver?

A

Hepatic Vein

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7
Q

Where and which enzyme is responsible for fat digestion?

A

Small intestine by pancreatic lipase

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8
Q

water-soluble enzyme

A

Lipase

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9
Q

Micelles

A

Absorption in small intestine enhanced
Micelles smaller to emulsion droplets
Micelle = bile salt + monoglycerides + FA + phospholipids
Polar portions of molecules at micelle surface
non-polar portions (FA Chains) form micelle core

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10
Q

What does bile contain and what is its function?

A

Bile salts + phospholipids secreted in bile
amphiphatic molecules whose non-polar portions associate with non-polar interior of lipid droplet leaving polar portions exposed at water surface.

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11
Q

Chylomicrons

A

Extracellular fat droplets
Contain phospholipids, cholesterol; fat-soluble vitamins

Transport lipids absorbed from the intestine to muscle tissue

Pass into lacteals between endothelial cells (cannot pass through capillary basement membrane)

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12
Q

Fat-soluble vitamins

Water-soluble vitamins

A

A, D, E, K

B group, C and folic acid
Passive diffusion or carrier-mediated transport.

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13
Q

Vitamin B12

A

Binds to intrinsic factor in stomach to form complex which is absorbed in distal ileum.

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14
Q

B12 deficiency

A

pernicious anaemia

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15
Q

Iron

A

10% of daily ingested iron absorbed across intestine into blood

transported across brush border membrane (via DMT1) into duodenal enterocytes

Iron ions incorporated into ferritin (protein)
(protein-iron complex intracellular iron store)

Unbound iron transported across serosal membrane blood. Iron in blood binds to transferrin

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16
Q

Hyperaemia

A

increased ferritin levels

more iron bound in enterocytes

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17
Q

Anaemia

A

decreased ferritin levels

more iron released to blood

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18
Q

Saliva Contains

A

Water: Softens, moistens, dilutes particles. Solvent

Mucins: Protein. Mucins + water = mucus.
Viscous solution - lubricant function

Amylase: Catalyses breakdown of polysaccharide (starch, glycogen) into disaccharide (maltose) + glucose

Electrolytes: Tonicity/pH

Lysozyme: Bacteriocidal - cleaves polysaccharide component of bacterial cell wall

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19
Q

Salivary Secretion

Parasympathetic

Sympathetic

A

Parasympathetic
Cranial nerves VII (facial) & IX (glossopharyngeal)
Stimulation and profuse watery salivary secretion

Sympathetic
Stimulation - small volume – viscous
High Mucus and Amylase

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20
Q 
High mucus (protein) content 
High amylase content
A

(a1 adrenoceptors)

b2 adrenoceptors

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21
Q

Receptive relaxation of stomach

A

Initiated following relaxation of LOS (Lower Oesophageal Sphincter) + entry of bolus into stomach
Vagal reflexes = relaxation of thin, elastic smooth muscle of gastric fundus and body

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22
Q

Stomach Functions

A

Temporary store of ingested material
Dissolve food particles and initiate digestive process
Control delivery of contents to small intestine
Sterilise ingested material
Produce intrinsic factor (Vitamin B12 absorption)

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23
Q

Mucous neck cells

A

mucus

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24
Q

Chief cells

A

pepsinogens

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25
Q

Parietal cells

A

HCl

Intrinsic factor

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26
Q

Stop Eating

A

Decrease Vagal Activity
Increase HCL (pepsinpogen to pepsin)
Decrease pH
Decrease Gastrin (Stomach)

Splanchnic reflex
Secretin release (Small Intestine)
- release of bicarbonate from pancreatic ducts
- inhibits secretion of gastric acid decreasing parietal cell secretions and therefore HCL

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27
Q

Fat in duodenum

A

GIP Gastric inhibitory polypeptide release - insulin

Decrease Gastrin and Parietal (HCl) secretion

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28
Q

Smell. Taste Food

Gastric acid secretion processes

A

Increase Vagus Stimulation - ACh - Parietal cells
- Neurocrine (vagus reflexes) - distention of stomach

G cells - Gastrin - Parietal cells
Endocrine (gastrin) - peptides in lumen

Gastrin/ACh - ECLcells - Histamine - Parietal cells
- Paracrine (histamine)

29
Q

Hormones released from gland cells in response to acid, hypertonic solutions, fatty acids or monoglycerides in duodenum

A 
Secretin, cholecystokinin (CCK), GIP 
Inhibit gastric acid secretion
Increase Pancreatic Secretion
Reduce gastric emptying 
(inhibit motility/contract pyloric sphincter)
30
Q

Pepsinogen

A

(zymogen = inactive precursor of pepsin) secreted by Chief cells

31
Q

Defaecation Reflex

A

parasympathetic control – via pelvic splanchnic nerves
Contraction of rectum
Relaxation of internal and contraction of external anal sphincters
Increased peristaltic activity in colon

32
Q

Enterotoxigenic Bacteria

A

Vibrio cholerae, Escherichia coli

Produce protein enterotoxins which activate intestinal chloride secretion from crypt cells

Elevate - cAMP, cGMP, calcium

+ H2O secretion swamps absorption in villus cells

33
Q

Secretory Diarrhoea Treatment

A

Give sodium / glucose solution

Oral rehydration therapy (ORS)

34
Q

Functions of Duodenum

Jejunum

Ileum

A

Gastric acid neutralisation; Digestion; Iron absorption

Nutrient absorption - 95%

NaCl/H2O absorption - chyme dehydration

35
Q

Villus cell

Crypt cell in small intestine

A

Absorbs: NaCl,
Monosaccharides, Amino acids, Peptides, Fats
Vitamins, Minerals, Water

Secretes: Cl & Water
(From epithelial cells lining crypts of Lieberkuhn)

36
Q

H2O secretion in small intestine importance

A

H2O secreted passively (osmotically) as a consequence of active secretion of chloride into intestinal lumen

Maintains lumenal contents in liquid state
Promotes mixing of nutrients with digestive enzymes
Aids nutrient presentation to absorbing surface
Dilutes and washes away potentially injurious substances

37
Q

Peristalsis

A

Following Segmentation and absorption of nutrients

Migrating Motility Complex (MMC)
Motilin (hormone) involved in initiation

1) Moves undigested material into large intestine
2) Limit bacterial colonisation of small intestine

As one MMC ends (terminal ileum) another begins
Arrival of food in stomach, cessation of MMC and initiation of segmentation

38
Q

Segmentation

A

Most common during meal

1) Contraction + relaxation of short intestinal segments
2) Moves chyme into adjacent areas of relaxation
3) Relaxed areas contract and push chyme back
4) Provides mixing with digestive enzymes
5) Brings chyme into contact with absorbing surface

Initiated by depolarisation generated by pacemaker cells in longitudinal muscle layer

Intestinal basic electrical rhythm (BER) produces oscillations in membrane potential

39
Q

Functions of the Pancreas

A

Endocrine - a and b cells secrete insulin and glycagon, somatostatin into bloodstream
(pancreatic islets; islets of Langerhans)

Exocrine - Acinar Cells secrete digestive enzymes
- main pancreatic duct - common bile duct

40
Q

Secretin

A 
S cells in duodenum
released in response to acid and fat in duodenum
Increases Pancreatic HCO3- secretion, 
Biliary Secretion
Decreases Gastric Acid Secretion
41
Q

Gastric inhibitory polypeptide (GIP)

Glucose-dependent insulinotropic peptide

A

Increase Insulin

Decrease Gastric H+ Secretion

42
Q

Brunnners Glands

A

HCO3- secretion in duodenum from pancreas or liver duct cells due to secretin release

43
Q

D-xylose absorption test

A

Distinguishes GI mucosal damage from other causes of malabsorption

44
Q

Manometry

A

Peristaltic Movements

45
Q

A liver sinusoid capillary / discontinuous capillary

A

Discontinuous endothelium that serves as a location for *mixing of the oxygen-rich blood from the hepatic artery and the nutrient-rich blood from the portal vein.

46
Q

Triacyclycerol contents before and after digestion

A

Glycerol and 3 Stearic Acids

Monoglyceride and 2 Fatty Acids

47
Q

Emulsification

A

Mechanical

  • smooth muscle contraction mixes lumenal contents.
  • dividing large lipid droplets into smaller droplets
  • increased surface area, accessibility to lipase action

Emulsifying agent
- prevents small droplets reforming into large droplets.

Bile salts + phospholipids secreted in bile

48
Q

Fundus

Body

Antrum Functions

A

Storage

Storage, Mucus
HCl, Pepsinogen, Intrinsic factor

Mixing/Grinding
Gastrin

49
Q

Gastric Mucus

A

Produced by surface epithelial cells + mucus neck cells

Protects mucosal surface from mechanical injury

Neutral pH (HCO3) - Protects against gastric acid corrosion and pepsin digestion

50
Q

Chewing

A

Voluntary
Somatic nerves - skeletal muscles of mouth/jaw

Reflex
Contraction of jaw muscles - pressure of food against gums, hard palate and tongue
- mechanoreceptors - inhibition of jaw muscles - reduced pressure - contraction

51
Q

Swallowing

A 
Oral Phase (voluntary)
Bolus pushed to back of mouth by tongue

Pharyngeal Phase
Presence of bolus - sequence of reflex contractions of pharyngeal muscles
Co-ordinated by swallowing centre (medulla)
Soft palate reflected backward and upward (closes off nasopharynx)

As bolus approaches oesophagus…
Upper oseophageal sphincter (UOS) relaxes and epiglottis covers opening to larynx

Once food has entered oesophagus…
UOS contracts (prevents food reflux)
52
Q

Acinar cells contain digestive enzymes stored as inactive zymogen granules. Function and how are they converted to an active form?

A

Prevents autodigestion of pancreas

Enterokinase (bound to brush border of duodenal enterocytes) converts trypsinogen to trypsin

Trypsin converts all other zymogens to active form

53
Q 
Proteases
Nucleases
Elastases
Phospholipases
Lipases

α-Amylase

A 
Cleave peptide bonds
Hydrolyse DNA/RNA
Collagen digestion
Phospholipids to fatty acids
Triglycerides to fatty acids+ glycerol

Starch to maltose + glucose

54
Q

Bare area

A

small area on diaphragmatic surface of liver surrounded by coronary ligament

Only part of liver not covered by connective tissue capsule and visceral peritoneum

55
Q

Septa

A

divide liver into hexagonal lobules

Central veins at centre of each lobule
Portal Triad at the corner of each lobule

56
Q

Portal triad

A

hepatic portal vein,
hepatic artery,
hepatic duct

57
Q

Hepatic cords

A

Radiate out from central veins and are
Composed of hepatocytes

Spaces between hepatic cords = hepatic Sinusoids (blood channels)

Bile canaliculus lies between cells within each cord

58
Q

Hepatocytes

A

bile synthesis
nutrient storage (glycogen, fat, vits (B12,A,D,E,K), Cu, Fe)
nutrient interconversion
detoxification

59
Q

Bile components

A

(1) Bile acids
(2) Lecithin
(3) Cholesterol solubilise Fat

(4) Bile Pigments Bilirubin (from haemoglobin)
(5) Toxic Metals Detoxified in liver
(6) Bicarbonate Neutralisation of acid chyme

(1) - (5) secreted by hepatocytes
HCO3 secreted by duct cells

60
Q

Bile Pigments

A

Breakdown products of haemoglobin from old/damaged erythrocytes

Bilirubin (predominant bile pigment) - extracted from blood by hepatocytes and secreted into bile
 yellow bile

Bilirubin modified by bacterial enzymes, brown pigments
 brown faeces

Reabsorbed bilirubin excreted in urine
 yellow urine

61
Q

Bile Acids

A

Synthesised in liver from cholesterol (0.5g/day)

Before secretion, bile acids conjugated with glycine or taurine to Bile Salts (Increased solubility)

Secreted bile salts recycled via enterohepatic circulation

62
Q

Sphincter of Oddi

A

Controls release of bile and pancreatic juice into duodenum

When contracted (closed) - bile forced back into gallbladder

63
Q

Fat in duodenum and CCK functions

A 
Fat in duodenum releases CCK
	CCK -  (A) Sphincter of Oddi relaxes
	  	    (B) Gallbladder contracts
Discharge of bile into duodenum - fat solubilisation
	CCK  - Pancreatic enzyme secretion
	 	  - Bile secretion
64
Q

H2O secretion important for normal digestive process:

A

Maintains lumenal contents in liquid state
Promotes mixing of nutrients with digestive enzymes
Aids nutrient presentation to absorbing surface
Dilutes and washes away potentially injurious substances

65
Q

Gastroileal Reflex

A

Gastric emptying - segmentation activity in ileum
Opening of ileocaecal valve (sphincter)
Entry of chyme into large intestine
Distension of colon
Reflex contraction of ileocaecal sphincter (prevents backflux into small intestine)

66
Q

Colon Functions

A

Absorption - Actively transports Na from lumen to blood

Osmotic absorption of water

Dehydration of chyme - solid faecal pellets

67
Q

Bacterial fermentation of undigested carbohydrate ??

A

Short chain fatty acids (energy source in ruminants)

Vitamin K (blood clotting)

Gas (flatus) - nitrogen, CO2, hydrogen, methane, hydrogen sulphide

68
Q

Defaecation Reflex

A

Under parasympathetic control
– via pelvic splanchnic nerves (no sympathetic influence)

Contraction of rectum
Relaxation of internal and
contraction of external anal sphincters

Increased peristaltic activity in colon
Increased Pressure on external anal sphincter - relaxes under voluntary control - expulsion of faeces

69
Q

Enterotoxigenic Bacteria

A

eg Vibrio cholerae, Escherichia coli

Produce protein enterotoxins which maximally turn on intestinal chloride secretion from crypt cells

Increase H2O secretion which swamps absorptive capacity of villus cells causing profuse watery diarrhoea

Act by elevating intracellular second messengers:
cAMP, cGMP, calcium

Enterotoxins don’t damage villus cells

Give sodium/glucose solution to Drive H2O absorption and allow rehydration

Revision Year 2 (14 decks)

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