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Stage 1 > GI Theme 3 > Flashcards

GI Theme 3 Flashcards

1
Q

What is the structure of amylose ?

A

linear polymer of alpha 1-4 glycosidic links

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2
Q

What is the structure of amylopectin ?

A

branched polymer with alpha 1-4 and alpha 1-6 glycosidic links

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3
Q

Where can you find alpha amylase ?

A

pancreatic juice and saliva

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4
Q

What does amylase hydrolyse and what cant it ?

A

hydrolyses alpha 1-4 links

cant hydrolyse alpha 1-6 links or alpha 1-4 linkks close to terminal branches ?

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5
Q

Starch digestion release what

A

maltose
maltotriose
alpha limit dextrins

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6
Q

What are alpha limit dextrins?

A

branched polymers of glucose 5-9 units long

formed due to the inability of amylase to hydrolyse alpha 1-4 links next to branch points

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7
Q

What happens to alpha limit dextrins in the mouth ?

A

they can be taken up by bacteria and used as an energy source

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8
Q

The length of time food is in the mouth detemrines what ?

A

how much maltose and maltotriose is released

they are carcinogenic

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9
Q

What carbohydrate digestion takes place in the stomach ?

A

none- acidic pH inhibits alpha amylase

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10
Q

What carbohydrate digestion takes place in the duodenum ?

A

pancreatic alpha mylase

digests remaining starch into maltose , maltotriose and alpha limit dextrins

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11
Q

Which is faster salivary alpha amylase or pancreatic alpha amylase ?

A

pancreatic alpha amylase

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12
Q

What is the role of oligosaccharidases ?

A

on the brush border

they further digest the maltose, maltotriose and the alpha limit dextrins

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13
Q

Where can you find oligosaccharidases ?

A

in the duodenum and the jejunum

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14
Q

What does isomalatase (alpha dextrinase) do ?

A

hydrolyse alpha 1-6 links that amylase csnt

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15
Q

What does maltase do ?

A

hydrolyse maltose and maltotriose into glucose

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16
Q

What does lactase do ?

A

hydrolyse lactose into glucose and galactose

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17
Q

What does sucrase do ?

A

hydrolyse sucrose into glucose and fructose

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18
Q

What are the end products of digestion with oligosaccharidases ?

A

monosaccahrides- glucose , fructose and galactose which can be absorbed by the duodenum and jejunum

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19
Q

Where does the absorption of monosaccahrides occur ?

A

duodenum and upper jejunum

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20
Q

How are glucose and galactose actively uptaken ?

A

by sodium-glucose transporter 1

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21
Q

What type of active transport does the sodium-glucose transporter use ?

A

secondary active transport

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22
Q

What creates the electrochemical gradient in sodium-glucose active transport ?

A

Na/K ATPase

basolateral membrane

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23
Q

How do glucose and galactose leave the epithelial cell ?

A

glucose transporter protein 2

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24
Q

How is the entry of galactose and glucose into the epithelial cell mediated ?

A

by the presence of sodium in the GI lumen

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25
Q

How does fructose enter and leave the intestinal epithelial cell ?

A

enters using facilitated diffusion - glucose transporter 5

exits using glucose transporter 2

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26
Q

What is sucrase-isolmaltase deficiency ?

A

low levels of sucrase and isomaltase in the brush border
intolereane to starch and sucrose
fructose and glucose are tolerated

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27
Q

What is glucose-galactose malabosprtion syndrome ?

A

mutation in SGLT-1

fructose can be given

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28
Q

What type of transport is SGLT?

A

secondary active trnasport

symport

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29
Q

What is the type of transport with GLUT proteins ?

A

facilitated diffusion

uniport

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30
Q

What are alpha limit dextrins hydrolysed by ?

A

isomaltase

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31
Q

How is pepsinogen converted to pepsin ?

A

by protons

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32
Q

How much protein does pepsin digest ?

A

15%

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33
Q

What is pro elastase ?

A

converted to elastase

digests serine in elastin

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34
Q

What are the peptidases ?

A

aminopeptidase
dipeptidase
dipetidyl aminopeptidase- cleaves a dipeptide from end of the dipeptide

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35
Q

How can small peptides be further hydrolysed ?

A

by peptidases in the cytosol

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36
Q

What is present on the apical membrane to provide gradients for peptide transport ?

A

Na/H transporters

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37
Q

What are the amino acid transport systems on the apical membrane ?

A

5 dependent on Na - active
2 are facilitated
7 in total

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38
Q

What are the amino acid transport systems on the basolateral membrane ?

A

5
3 are Na independent - efflux of amino acids into blood
2 are Na dependent - active

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39
Q

How do fat soluble vitamins diffuse ?

A

diffuse acorss the brush border membrane

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40
Q

Where is vit B12 absorbed ?

A

ileum

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41
Q

How is B12 found in foods ?

A

bound to proteins

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42
Q

What happens to b12 in the stomach ?

A

released and binds to R proteins - high affinity

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43
Q

What is intrinsic factor ?

A

vitamin b12 binding protein
secreted by gastric parietal cells
binds to B12 with less affinity than R proteins

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44
Q

What degrades the R - protein B12 complexes ?

A

pacnreatic proteases

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45
Q

What happens to the B12 afte degradation from R proteins ?

A

binds to IF- resist protease degradation

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46
Q

What happens to the B12 afte degradation from R proteins ?

A

binds to IF- resist protease degradation

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47
Q

What does the brush border of the ileum contain ?

A

receptors for B12- IF complexes

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48
Q

What might happen in pancreatic insuffficinecy ?

A

no degradation from R proteins

B12 deficiency might occur

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49
Q

What is the B12 carrier ?

A

transcobalamine II

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50
Q

What inhibits gastric emptying locally ?

A

CCK - lipid present in the duodenum

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51
Q

What emulsifies lipids ?

A

bile salts and lecithin

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52
Q

What is the purpose of emulsification ?

A

increase the surface area for water soluble enzymes to act

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53
Q

What are the lipolytic enzymes found in pancreatic juice ?

A

pancreatic lipase
co-lipase
cholesterol esterase
phospholipase A

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54
Q

How is pancreatic lipase inhibited ?

A

bile salts bind to fat surface and prevent lipase binding

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55
Q

What does co lipase do ?

A

displaces bile salts on the fat surface enabling lipase to fucntion

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56
Q

What are the products of triglyceride break down ?

A

2-monoglyceride

2 x NEFA

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57
Q

What does cholesterol esterase do ?

A

cleaves a fatty acid from cholesterol esters

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58
Q

What does phospholipase A2 do ?

A

turns phsopholipids into lypophospholipid and NEFA

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59
Q

What is micelle formation ?

A

bile salts form micelles with the products of fat digestion

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60
Q

What do the bile salts act as in micell formation ?

A

surfactant

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61
Q

What is the structure of micelles ?

A

lipid molecules arranged in a spherical form

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62
Q

Where does absorption of lipids take place ?

A

in the ileum and the jejunum

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63
Q

What is the unstrirred layer ?

A

mucus layer
with microvilli between the lumen and the brush border
molecules pass through and become more disorgansied as they approach the apical membrane

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64
Q

What lipid transport occurs at the brush border membrane ?

A

cholesterol transporter mediates facilitated transport
microvilli membrane fatty acid binding protein transports long chain fatty acids by secondary active transport - Na/K ATPase

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65
Q

What is the role of cytosolic transport membrane ?

A

transport the products of lipid digestion to the smooth endoplasmic reticulum

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66
Q

What are the cytosolic lipid transport proteins ?

A

fatty acid binding protein and sterol carrier

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67
Q

What happens to lipids in the smooth endoplasmic reticulum ?

A

they are esterified again
enter pre chylomicrons
go to golgi
too large to leave across the basement membrane
lacteals - lymphatic capillaries- large enough - empty into the lymph and the the blood by the thoracic duct

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68
Q

Where does absorption of bile salts occur ?

A

in the terminal ileum

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69
Q

How are conjugated bile salts actively taken up ?

A

by an Na bile duct co transporter

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70
Q

How do bile salts enter the blood ?

A

they re enter the portal blood
bound to albumin
return to the liver

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71
Q

How does fructose get from the gut to the blood ?

A

enters via facilitated diffusion and then leaves bu GLUT 5

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72
Q

What are the brush border peptidases ?

A

aminopeptidase
dipeptidase
dipeptidyl aminopeptidase

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73
Q

Where does lipid break down occur in the GI tract ?

A

stomach
duodenum
jejunum

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74
Q

What 2 substances are responsible for emulsification ?

A

bile salts and lecithin

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75
Q

What is the role of R protein ?

A

to protect IF from gastric acid

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76
Q

Which compounds predominantly contribute to micelle formation ?

A

bile salts

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77
Q

What is the mechanism whereby lipids in the duodenum prevent gastric emptying ?

A

CCK

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78
Q

what are anciliary organs of digestion

A

pancreas, gallbladder and liver

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79
Q

how long is the human gut

A

5m long

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80
Q

how is the sa increased in the human gut

A

folds and microvilli in the SI

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81
Q

outline the journey through the gut

A 
Oesophagus
Pyloric sphincter and stomach
Upper small intestine
Lower small intestine
Caecum
Colon
Rectum
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82
Q

what are the GI Tract Disorders

A

Physical (blockages/strictures/ fat deposition)
Functional (nerve-peristalsis/muscle)
Environmental insult (infections, toxins, DNA mutations)
Immune-related ( defence becomes attack)
Unknown aetiology
All may have metabolic implications

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83
Q

what disorder affect the whole length of the GI tract

A

GI cancers

Crohns disease

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84
Q

what disorders move down the GI tract

A

oesophagus:
- Dysphagia (difficulty swallowing)
Oesophageal stricture/tumours
Oesophageal varices (liver disease)
Oesophageal reflux/indigestion
Barret’s oesophagus

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85
Q

what is dysphagia

A

oropharygeal

  • neuromuscular disorders or stroke
  • cant close trachea
  • choking
  • aspiration pneumonia
  • anxiety, anorexia
  • dehydration
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86
Q

how can dysphagia be managed

A

soft diet
pureed diet
thickened fluids
PEG- feeding tube, long term feeding

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87
Q

what happens in dysphagia

A

food can go to lungs

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88
Q

what is oesophageal stricture

A 
food sticking after swallowing 
caused by
- achalasia
-astrictures 
-present with dysphagia
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89
Q

how can oesophageal stricture be treated

A

dietery management

surgical

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90
Q

what is Gastroesophogeal Reflux Disease (GORD)

A

Reflux of gastric contents through lower oesophageal sphincte

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91
Q

what is Chronic: GORD

A

potential progression to Barret’s Oesophagus/cancer

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92
Q

what can GORD be aggrevated by

A

Spicy and fatty foods, tomatoes, onion, garlic
Caffeine and alcohol, carbonate drinks
Obesity and pregnancy

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93
Q

what is Laryngo-pharyngeal Reflux (LPR)

A

refluxate that travels above the upper oesophageal sphincter

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94
Q

is LPR physiological

A

no

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95
Q

How is GORD linked to erosive tooth wear

A

Intrinsic acids from the stomach can travel to the mouth and can damage enamel and dentin

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96
Q

how is erosive tooth wear managed in those with GORD

A

dental treatment & PPI therapy

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97
Q

what is hiatus hernia

A

stomach protrudes up to chest cavity

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98
Q

what is dyspepsia

A

discomfort in upper abdomen thta is food related

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99
Q

what is the cause of dyspepsia

A

peptic ulcer (by bacterial infection- helicobacter pylori)

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100
Q

what is the treatment for peptic ulcers

A

single 14 dyacourse combinatin therapy leading to healing

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101
Q

why are 2 antibiotics needed to treat peptic ulcers

A

h pylori can be antibiotic resistant

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102
Q

what is perniciuos anaemia

A

automimmune destrcution of gastric parietal cells that produce IF

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103
Q

what happens to rbc in pernicious aneamia

A

large

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104
Q

what are the symptoms of pernicuous anaemia

A 
extreme fatigue 
shortness of breath 
pins and needles 
muscle weakness
mood swings 
memory
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105
Q

how is pernicuous anaemia treated

A

vit b injection every 3 mnths

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106
Q

what are the oral symptoms of B12 deficiency

A

atrophic glossitis (sore and red beefy tongue)
mouth ulcers
angualr chleiltis

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107
Q

what is coeliac disease

A

autoimmune resposne to gluten and gliadin proteins

- wheat, rye, barley. oats

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108
Q

what happens in coeliac disease

A

damage to villi which affects absorption of nutrients

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109
Q

what are the complication in coeliac disease

A

anaemia
osteoporosis
neurological conditions
increased risk of small bowel cancer and intestinal lymphoma

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110
Q

how is coelaic disease managed

A

complete avoidance of gluten
gluten free breads
iron calcium and folate supplement

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111
Q

what crohns disease

A

inflammatory disease

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112
Q

what causes crohns disease

A

genetics
inapropirate immune response to commensal bacteria
environmental trigger

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113
Q

where can crohns disease occur

A

any where in gi tract from mouth to anus

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114
Q

what are the symptoms of crohns disease

A 
Abdominal pain
Diarrhoea
Nausea and vomiting
Fatigue
Weight loss
fistule- 2 parts of SI join 
anal fissures
115
Q

Crohn’s Disease Complications

A 
Inflammation 
Strictures/blockages 
Abscesses 
Fistulae- 2 parts of SI join 
Anal fissures
Bacterial Overgrowth
Toxic megacolon
116
Q

what are treatments for crohns disease

A 
Steroids
Antibiotics
Liquid diet
Supplementary nutrition
Surgeries (multiple
117
Q

what are the oral symptoms of crohns disease

A

mouth sores
ulcers
swellings
gum problems

118
Q

what are the oral symptoms of crohns disease

A

mouth sores
ulcers
swellings
gum problems

119
Q

what are the disorders moving down the gi tract (large intestine)

A

diverticular disease

irritable bowel disease

120
Q

what is diverticular disease

A

pockets created in teh lining trapping food and waste

121
Q

what is diverticular disease caused by

A

thickening of msucle in colon casuing extra pressure

122
Q

how is diverticular disease treated

A

fibre in diet

123
Q

what is IBS

A

disorder of the motor activity whole bower but mostly colon

124
Q

how can IBS be managed

A

low FODMAP

125
Q

how is IBS diagnosed

A

when all other caused are ruled out

126
Q

what is the microbiome

A

role of bacteria in periodontitis

role in digestion, vit production, immune function

127
Q

what does the gut microbiome have implications for

A

obesity
cancers
mental health
autism?

128
Q

What are the functions of the kidney ?

A

Excretion
Homeostasis
Hormone production

129
Q

What does the kidney excrete ?

A

foreign substances and products of metabolsim
urea
creatinine
hormones and drugs

130
Q

What does the kidney regulate in homeostasis ?

A 
ECF volume 
blood pressure 
osmolarity 
ion levels- calcium and potassium 
regulation of pH
131
Q

What hormones does the kidney produce ?

A

renin

132
Q

Urine produced by the kidney travels where ?

A

out of the kidney via the ureter and into the bladder where it is expelled by the urethra

133
Q

Where does the renal vein drain back into ?

A

inferior vena cava

134
Q

What are the 2 types of nephrons ?

A

cortical- Superficial cortical and the midcortical

juxtamedullary- penetrate deeply into the medulla and surrounded by the vase recta

135
Q

where is the loop of henle longer

A

in the juxtameduallry nephrons therefore th urine id more cocnentrated

136
Q

What is the glomerulus ?

A

a cluster of blood vessels

water and solutes flter from the blood into the renal tubule through the glomerulus

137
Q

What is the glomerulus bounded by ?

A

the afferent and the efferent arterioles

138
Q

What is the purpose of the afferrent and the efferent arterioles ?

A

they contain smooth muscle which contracts to increase blood pressure

139
Q

What is the nephron surrounded by ?

A

the peritubular capillaries

140
Q

What happens in the renal corpuscle ?

A

the production of filtrate

141
Q

What happens in the loop of henle ?

A

urinary concnetration

142
Q

What happens in the distal tubule ?

A

control of water and Na balance

143
Q

What happens in the collecting duct ?

A

control of water and sodium balacne

144
Q

What is the average glomerular filtration rate (GFR) ?

A

125mL a min

180 L a day

145
Q

What does the filter cocnsit of ?

A

fenestrated endothelium
collagen basement membrane
epithelium of bowmans capsule which has podocyte filtration slits

146
Q

How does the filter restrict solute movement ?

A

based on size and charge

147
Q

What is the first step in the production of urine ?

A

production of ultrafiltrate - contains no cellulr elements or proteins (RBCs and albumin)

148
Q

The concentrations of solutes in the ultrafiltrate is similar to ?

A

the plasma

149
Q

What is filtered out of the plasma ?

A

all plasma constituents except for RBCs and serum albumin

150
Q

What is proteinuria ?

A

the presence of proteins in the urine as they are more readily filtered

151
Q

What is haematuria ?

A

the presence of RBCs in the urine

152
Q

What are the 3 pressures that determine the overall net pressure in the bowmans capsule ?

A

outwards- hydrostatic pressure in glomerular capillaries
inwards
- colloid osmotic pressure
- hydrostatic pressure in the bowman’s capsule

153
Q

what does autoregulation of the GFR do?

A

Maintains Renal Blood Flow (RBF) & GFR within narrow limits despite Blood Pressure fluctuations

154
Q

What are the 2 mechanisms of autoregulation of the GFR ?

A

myogenic response

tubuloglomerular feedback

155
Q

What is the myogenic response ?

A

arterial pressure increases the renal afferent arteriole is stretched and flow increases
vascular smooth muscle responds by contracting and thus increasing resistance
flow returns to normal

156
Q

Where is the loop of henle situated between ?

A

the afferent and the efferent arterioles

157
Q

What is communication between the tubules and the arterioles mediated by ?

A

macula densa- plaque of epithelial cells in loop of henle adjacent to the arterioles in the tubules- they sense flow rate
granular cells

granular cells (juxtaglomerular cells) in afferent ateriole which secrete renin)

158
Q

What happens if there is an increase in GFR ?

A

flow through the tubule increases
flow past the macula dense increases
paracrine are sent from the macula densa to the afferent arterioles
the afferent atriole contricts and the efferent atriole pressure increased
hydrostatic pressure in thhe glomerulus decreased
GFR decreases

159
Q

what happens to GFR when the afferent atreriole constricts

A

decreases

160
Q

what happens to GFR when efferent ateriole constricts

A

increased

161
Q

How can we measure GFR ?

A

by using a substance that isnt excreted or absorbed into the tubules

162
Q

What is inulin ?

A

a polymer of glucose that is not indogeneous

163
Q

What is GFR and what is it measured in ?

A

rate of filtrate production

ml/min

164
Q

What is the equation for GFR ?

A

Amount filtered=Amount excreted

Pinulin x GFR=V x Uinulin

165
Q

What are the units for the plasma and the urine concentrations of the inulin ?

A

mg/ml

166
Q

What is the unit for the rate of urine production ?

A

ml/min

167
Q

What are the requirements for a substance to be able to measure GFR ?

A

must be freely filtered at the glomerulus
must not be abosrorbed or secreted into the nephron
Must not be subject to metabolsim or produced by the kidney
Must not alter the GFR

168
Q

What are suitable substances for the measurement of GFR ?

A

Creatinine and Inulin

169
Q

What is creatinine ?

A

product of skeletal muscle metabolism
Amount produced is proportional to the muscle mass
constantly produced therefore constantly excreted

170
Q

What is the need for the GFR ?

A

allows us to assess the perfomrance of the kidney
see any signs of kidney disease
analyse the way the kidney handles solute

171
Q

What is the clearance rate ?

A

mls of plasma totally cleared of a given solutein 1 minute

172
Q

What is the equation for clearance rate ?

A

Px x Cx=Ux x V

173
Q

If there is no reabsorption no secretion what is the relationship of the CR and the GFR ?

A

GFR=CR

eg. inulin

174
Q

f there is total reabsorption and no secretion what is the relationship of the GFR and the CR ?

A

CR= 0

175
Q

If there is net absorption what is the relationship between the GFR and the CR ?

A

Cx

176
Q

If there is net secretion what is the relationship between the GFR and the CR ?

A

CR>GFR

177
Q

What affect does diabetes have on the urine ?

A

Excess plasma glucose means that more glucose is filtered out of the blood- not all of this can be reabsorbed therefore theire is glucose in the urine
increased osmolarity in the tubule meas that fluid is drawn in - triggers the thirst response and more urine is produced

178
Q

What are the anatomical features of the kidney ?

A 
renal artery 
renal vein 
urteter 
renal medulla and the renal cortex 
papilla
179
Q

Is the cortex or the medulla more densely supplied by the renal artery ?

A

cortex

180
Q

How is urine concentrated ?

A

More water abosorption through the CD as it is permeable to water
increases the concentration inside the tubule and urine is hyperosmotic

181
Q

Where is ADH produced ?

A

in the supraoptic and paraventricular nuclei of the thalamus

182
Q

Where is ADH released from ?

A

posterior pituitary gland

183
Q

What stimulates ADH release ?

A

increased plasma osmolarity

decreased blood pressure and blood volume

184
Q

What are the actions of ADH ?

A

increases permeability of the CD
increases urea permeability of the CD
increases NaCl resbsorption in the TAL

185
Q

What is the net effect of ADH ?

A

increases water absorption

186
Q

What are changes in osmolarity detected by ?

A

osmoreceptors in the hypothalamus

187
Q

Where do the osmoreceptors of the hypothalamus send a message to ?

A

posterior pituitary to release ADH

188
Q

If there is an increase in plasma osmolarity ?

A

ADH secretion increases

189
Q

How is ADH destroyed ?

A

liver and the kidneys

190
Q

What is the cellular mechanism by which ADH increases water absorption ?

A

ADH binds to receptors on the basolateral membrane
stimulates the production cyclic AMP from ATP by adenylyl cyclase
activates protein kinse
insertion of AQP2 channels on the CD membrane - apical cell membrane
water permability increases and water is taken into the blood

191
Q

If ADH is present what is the condition of urine ?

A

ADH increases water reabsorption from the CD therefore the urine is hyperosmotic

192
Q

What happens if ADH is absent ?

A

there is no stimulation of the downstream aquaporin production therefore no water reabsorption and the urine is dilute

193
Q

What is the the role of the supraoptic and paraventricular nuclei of the hypothalamus ?

A

stimulate ADH secretion from the posterior pituitary

194
Q

What happens if there is a decreased ECF osmolarity ?

A

ADH release is supressed
thirst response is supressed
CD not permeable

195
Q

What is the effect of ANP on ADH ?

A

ANP inhibits ADH

196
Q

What is the affect of alcohol on ADH ?

A

alcohol inhibits ADH

197
Q

What is the effect of nicotine on ADH ?

A

nicotie promotes ADH

198
Q

What is the main role of aldosterone ?

A

Aldosterone is the main hormone regualting sodiium balance

199
Q

Where is aldosterone released from ?

A

Zona Glomerulosa of the adrenal cortex

200
Q

What stimulates aldosterone ?

A

hyperkalaemia
low blood pressure
angiotensin II in the RAS

201
Q

What are the actions of aldosterone ?

A

increase potassium secretion into the DT and the CD
Increases sodium reabsorption in the DT and the CD
leads to increased blood volume and pressure

202
Q

What is the cellular mechanism of aldosterone action ?

A

Aldosterone binds to receptors in the cytoplasm
initiates transcription of sodium channels
number of sodium channels on apical surface increases
increased sodium uptake
sodium goes through the basolateral membrane into the blood and inreases blood pressure

203
Q

What are the 3 stimuli of aldosterone ?

A

Increased potassium
Decreased blood pressure
Decreased flow past the macula densa

204
Q

What is the inhibitor of aldosterone release ?

A

Increased plasma osmolarity

205
Q

What are the 3 components of the juxtaglomerular apparatus ?

A

Juxtglomerular cells
macula densa
extraglomerualr mesangial cells

206
Q

Where do the extraglomerular mesangial cells sit ?

A

between the TAL and the afferent arteriole

207
Q

What is the mode of activity in resposne to Sympathetic activity of the heart ?

A

high HR
to return to normal the wall tension in the afferent arterioles decreases
sodium delivery to the macula densa decreases
low blood volume

208
Q

What does angiotensin II do to renin ?

A

it acts as a negative feedback loop and stops renin release

209
Q

What is ANP ?

A

anti-natriuretic peptide

210
Q

Where is ANP produced from ?

A

atria when stretched

211
Q

What is the effect of ANP ?

A

increases water and sodium excretion

212
Q

What affect does ANP have on the adrenal cortex ?

A

it stops aldosterone release

213
Q

What affect does ANP have on the kidney ?

A

stops renin
increases GFR
inhibis sodium chloride and water reabsorption

214
Q

What is the affect of aldosterone on the hypothalamus ?

A

stops ADH release from posterior pituitary

215
Q

What is secreted into the proximal tubule ?

A

urea and creatinine

216
Q

What is reabsorbed in the proximal tubule ?

A

Glucose
proteins
aminaoacids
lactate

217
Q

What is reabsorbed from the descending limb ?

A

water

218
Q

What is secreted into the loop of henle ?

A

urea

219
Q

What is absorbed from the ascending limb ?

A

sodium and chloride

220
Q

What is absorbed from the distal tubule ?

A

ions

221
Q

What is secreted into the distal tubule ?

A

protons

ammonium ions

222
Q

What is reabsorped from the collecting duct ?

A

water

urea

223
Q

What percentage of water and solutes of the filtrate are reabsorbed into the PCT ?

A

70%

224
Q

What is the average GFR

A

125 ml/min

225
Q

what are the three layer of glomerular filter

A

Collagen basement membrane
fenestrated enothelium
epithelium of bowmans capsule with podocyte slits

226
Q

How does the macula dens work ?

A 
increased flow past the macual densa
paracrine released from the macula densa and acts on the affferent arteriole 
increases resistance 
reduces hydrostatic pressure 
GFR reduces
227
Q

What is the normal blood osmolarity ?

A

290 mOsmoles

228
Q

What is the affect of nicotine on ADH production ?

A

stimulates ADH

229
Q

What are the channels that Aldosterone promotes ?

A

ENACC channels

Na/K pump

230
Q

What is reabsorbed i the proximal convuluted tubule ?

A

70% water and solutes

231
Q

What is present on the apical surface of PCT ?

A

microvilli

232
Q

What are the functions of the PCT ?

A

Reabsorption of the bulk of filtered NaCl
Reabsorption of glucsoe,amino acids
Secretion or organic molecules
pH homeostasis

233
Q

What is the form of Na+ transport on the apical membrane ?

A

Na transport acorss the apical membrane is mediated by glucose and amino acids in secondary active transport
counter exchange of Na/H exchanger

234
Q

What is the form of Na transport in the basolateral membrane ?

A

Na is rmeoved by the Na/K ATPase on the basolateral membrnae
this is followed by chloride and water by a paracellualr route

235
Q

What happens in the descending limb of the loop of henle ?

A

Water moves out

NaCl stays

236
Q

What happens in the ascending limb of the loop of henle ?

A

Water stays

NaCl moves out

237
Q

What are the mechanisms of Sodium transport in the loop of henle ?

A

Na/Cl/L transporter
Na/H transporter - allows the acidification of urine
Na/K ATPase on the basolateral membrane

238
Q

What happens in the DCT ?

A

NaCl moves out the blood and H20 stays

239
Q

What are the mechanisms of Na transport in the DCT ?

A

NaCl moves into the blood

NaCl transporter and Na?K ATPase on the basolateral membrane

240
Q

What happens in the collecting duct

A

NaCl movement

241
Q

what are the 2 types of cells in the collecting duct

A

principle and intercalated cells

242
Q

what can block Na+/K+/2Cl transport in the loop of henle

A

loop diuretics

243
Q

what can block Na/Cl cotransporters in the DCT

A

thiazide Diuretics

244
Q

what do principal cells do

A

regulate ion balance based on expression of channels on the apical membrane

245
Q

What are examples of the action of principal cells ?

A

aldosterone increases ENac Channels on the apical membrane

ADH increases aquaporins on the CD membrane

246
Q

What are the actions of intercalated cells ?

A

Acid/base homeostasis

247
Q

What are the two types of intercalated cells ?

A

Alpha and beta

248
Q

What is the role of alpha intercalated cells ?

A

excrete protons into the urine and reabsorb bicarbonate into the blood

249
Q

What channels does the alpha intercalated cells use ?

A

secrete protons by the H ATPase and H/K exchanger

Cl/HCO3 exchanger on the basolateral membrane

250
Q

What is the role of beta intercalated cells ?

A

they excrete bicarbonate and reabsorb protons into the blood

251
Q

What channels do the beta intercalated cells use ?

A

Cl/HCO3 exchanger

H ATPase

252
Q

What happens after a high water load ?

A

water must be excreted in excess - dilute urine that is hyposmotic to the plasma

253
Q

What is the normal plasma osmolarity ?

A

290 mOsml

254
Q

What happens after a water restriction ?

A

water msut be retained

hyperosmotic urine to the plasma is produced

255
Q

How is excretion of a dilute or concentrated urine achieved ?

A

by the countercurrent mechanism

256
Q

What acts as the countercurrent multiplier ?

A

loop of henle

257
Q

What acts as the countercurrnent exchanger ?

A

vasa recta

258
Q

What does countercurrent flow mean ?

A

2 parallel limbs with fluid moving in opposite directions

259
Q

What is the osmolarity of the PCT compared to the interstitial fluid ?

A

isotonic

260
Q

What happens in the ascending limb of the loop of henle and what is the consequence

A

solutes move into the interstitium

increases the osmolarity of the interstitium

261
Q

What happens in the descending limb of the loop of henle ?

A

fluid becomes more concentrated as water move out to equilibrate the interstitium

262
Q

What happens as more fluid enters the loop of henle ?

A

more concentrated fluid is formed in the descending limb and enters the ascending limb
a gradient forms from top to bottom in the interstitium

263
Q

What is the condition of the fluid at the bottom of the loop of henle ?

A

Hypertonic as water had moved out

264
Q

What is the condition of the fluid at the DCT ?

A

hypotonic as solute has moved out

265
Q

What are the vasa recta ?

A

long extensions of the peritubular capilaaries

run parallel to the loop of henle in juxtamedulalry nephrons

266
Q

What are the functions of the vasa recta ?

A

water and solutes are reabsorbed by the vasa recta

provides o2 to the medulla

267
Q

What happens in the descending vasa recta ?

A

solutes move into the VR down their conc gradient

water moves out the VR

268
Q

What happens in the ascending vasa recta ?

A

water moves into the VR

Solutes move out the VR

269
Q

What is the role of urea ?

A

important for maintaining medullary concentration gradient

270
Q

What are the 3 mechanisms of pH control ?

A

buffers
respiratory control
renal control

271
Q

What happens if the metabolic rate increases ?

A

co2 increases - equilibrium pushed to the right
increased protons cant be buffered by bicarbonate but can be buffered by non bicarb buffers such as Hb
bicarb is much higher now and can buffer protons from non resp sources

272
Q

what is the consequence of increased protons in metabolism being released from organic acids ?

A

bicarbonate can act as a buffer

273
Q

How is respiratory control of pH carried out ?

A

high levels of co2 signalled by the carotid and aortic peripheral chemoreceptors and they go to the respiratory centre and signal an increased VR

274
Q

How is pH controlled in acidosis ?

A

H is high in the interstitial space reacts with bicarbonate to make co2 and water which dissociates into protons and bicarbonate and the protons are excreted by a H/K ATPase
alpha intercalated cells

275
Q

How is pH controlled in alkalosis ?

A

beta intercalalted cells
carbon dioxide and water in the cell are reacted into protons and bicarbonate and the cl/HC03 exchanger excretes bicarbonate into the urine

276
Q

What does contraction of the afferent arteriole lead to ?

A

reduces renal blood flow and reduces GFR and hydrostatic pressure

277
Q

What does contraction of the efferent arteriole lead to ?

A

reduces RBF

increases hydrostatic pressire and increases GFR

278
Q

What does dilation of the afferent arteriole lead to ?

A

increases RBF and increases GFR and hydrostatic pressure

279
Q

What does dilation of the efferent arteriole lead to ?

A

increases RBF but decreases hydrostatic pressure and GFR

280
Q

What does the macula densa do if therie is increases GFR ?

A

increased NaCl in the distal tubule
macual densa sense an increased flow
release paracrine that act on afferent arterioles
increases ressitance of the afferent arteriole and therefore reduce plasma flow

281
Q

What are renal arterioles innervated by ?

A

sympathetic neurones

282
Q

What are he sympathetic neurones activated in response to

A

fear
pain
response to fall in blood pressure

283
Q

What does the sympathetic inenrvation cause ?

A

constriction of renal blood arterioles

Stage 1 (21 decks)

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