Digestion

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What’s the inner layer of the GIT?

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1

What’s the inner layer of the GIT?

mucosa

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2

Name 2 types of mucosas and where they are found and why?

  1. folded→ absorption / digestion

  2. straight→ quick movement (oesophagus)

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3

What’s over the mucosa?

Submucosa

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4

What’s the enteric nervous system?

3rd division of nervous system

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5

What’s in the submucosa?

Blood vessels + Nerves + Glands

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6

What’s the function of the Meissner’s Plexus?

Determine vessels diamter/ secretions

→ control of submucos

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7

What are the two layer of muscle ?

Inner= circular

Outer= longitutal

(inner part of the egg (zoltko) is a circular ball, outer is a long oval)

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8

What’s the serosa?

smooth muscle layer

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9

List the three phases of swallowing?

  1. oral

  2. pharyngeak (respiratory inhibited to prevent choking)

  3. oesophageal

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10

Where’s the swallowing centre?

Medulla

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11

What receptors are in the pharynx?

Touch receptors

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12

What are the 3 commands that the swallowing centre sends in the medulla?

  1. soft palate blocks nasal and epiglottis and larynx blocks the trachea

  2. upper oesophageal sphincter relaxes

  3. peristakic wave

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13

What cells line the oesophagus?

Squamous (flat cells)

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14

What are the types of muscle that control the oesophagus?

1/3 skeletal

1/3 skeletal & smooth

1/3 smooth

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15

Where’s the lower oesophageal spincter?

near the stomach to prevent reflux

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16

In the stomach what does the mucosa contain?

Gastric glands that release gastric juices

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17

What do goblet cell secrete?

mucus and HCO3-

(both protect the stomach from autodigestion)

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18

What do pariental cells secrete?

HCl and intrinsic factor

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19

What does intrinsic factor contain?

B12

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20

Why is B12 needed?

To absorbe iron (pernicious anaemia)

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21

What do enterochromaffin-like cells secrete?

Histamine and Serotonin

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22

What does serotonin and histamine control?

Pancreas

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23

What do chief cells secrete?

pepsinogen

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24

What activates pepsinogen?

HCl

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25

Name the 2 hormone secreting cells in the stomach?

G cells

D cells

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26

What do G cells secrete?

Gastrin

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27

What do D cells secrete?

Somatostatin

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28

What are secretagogues?

They gauge out secretions (cause the secretion of an other substance)

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29

What stimulates the release of HCl?

  • histamine

  • Acetylcholine

    • gastrin

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30

How does the stomach churn?

Peristaltic waves

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31

How is the gastric slow wave regulated?

by the pacemaker zone in the fundus

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32

What’s stronger fundus& body or antrum?

Antrum at the bottom because that’s where most food is

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33

What’s the pylorus?

Sphincter acting

→ prevents chyme in the duodeum

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34

What nerves cause the contriction of the pylorus?

Sympathetic and Vagus

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35

What does the vagus do to the pylorus?

constrict and relax

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36

How does the antrum work with the duodeum?

contracts as a unit “ atral systole”

duodeum relax

a few ml of chybe → duodeum

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37

What are the three regions of the duodeum?

Duodeum/ Jejunum/ Illeum

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38

What are the functions of the jejunum and illeum?

reserve , most work happens in the duodeum

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39

What’s the brush border?

Microvilin

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40

What are the brush border enzymes?

sucrase , aminopeptidases

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41

Where is the pacemaker for the small intestine?

Near bile duct

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42

What does the dile duct do?

Deliver liver and pancreatic secretions

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43

Does motility get faster or slower as yoi go down in the small intestine?

Slower

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44

What segmentation?

Mixes chyme with enzymes and mucous

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45

What cells generate the contraction pace in the SI?

Interstitial cells of Cajal

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46

What kind of waves are produced by the interstitial cells of Cajall

slow

(faster at the proximal end)

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47

What’s the function of the large intestine?

Absorb salt and water

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48

What’s the haustra?

Folded outer surface of the large intestine

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49

Order

sigmoid colon/ transverse colon/ descending colon and rectum

Transverse

Descending

Sigmoid

Rectum

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50

What’s the valsalva manoeuvre?

Expiring against a closed glottis which raises vein pressure

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51

Is digestion regulated?

No, only secretions and motility is

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52

What regulates the GIT?

Hormones and neural control

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53

What cells produce gastric acid?

Pariental cells

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54

Why is gastric acid needed?

Pepsinogen→ pepsin

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55

How do pariental cells generate protons?

CO2+ H20

(carbonic anhydrase)

H2CO3→ H+ + HCO3-

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56

What happens to the H+ generated by pariental cells?

Pumped outside the cell into the gland duct by active transport

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57

What happens to Cl- in the pariental cells?

Pumped against conc. gradient in the cell

this allows HCO3- to get out

no overall change in charge!

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58

What ion is taken in when the proton leaves the pariental cell?

(anion exchange H+ & ____)

K+

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59

What cells secrete pepsin

Chief cells

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60

What stimulates pepsin?

gastrin , acetylcholine and acid

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61

What cells make the mucous?

Gastric neck cells

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62

What cells secrete bicarbonate?

Epithelial cells

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63

What are the three phases of gastric acid regulation?

Cephalic (brain)

Gastric

Intestinal

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64

How is the cephalic phase initiated?

Smell taste→ tells pariental cells stimulated

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65

What nerve controls the cephalic phase response?

Vagus

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66

What initiates the stimulatory gastric phase?

Food in stomach

amino acids released

G Cells release gastrin→ gastrin stimulates pariental cells→ HCl released

→ chief cells release pepsinogen

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67

How is the gastric phase regulated?

If pH falls below 2 = negative feedback and parinetl cells stop producing HCl

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68

What type of response is the intestinal phase?

Inhibitory

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69

What mediates the intestinl phase?

chyme in duodeum= imhibition of more acid released

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70

What three things are released in the inhibitatory intestinal phase?

  1. Secretin

  2. Gastric Inhibitatory Peptin

  3. Cholecytokin CCK (stops motility and secretion)

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71

What are peptic ulcers

erosion of mucous membrane

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72

What two nerve thingies make up the enteric nervous system?

Meissner’s Plexus = control of secretions (sounds german and they love when sauerkraut secretes acidic juices)

Auerbach/ myenteric = control of muscles layers

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73

What nerves supply the enteric nervous system?

para/ sympathetic?

Para and sympathetic

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74

How does the ENS control the pacemaker cells in the GIT?

They can speed it up/down

not activate (will work regardless of ENS status)

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75

What’s the gastroileal reflex?

gastric activity= illeal motility

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76

How is the gatroileal reflex protectory?

If intestine stretches (ouch) = stomach will slow down

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77

How do paracrine secretions act?

Locally

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78

Where do paracrine secretions get released from

intestinal/ gastric mucosa

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79

What does motilin do?

Stimulate contraction of stomach antrum and duodeum

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80

Where do exocrine glands secrete?

Into ducts

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81

What are the 3 pairs of salivatory glands?

  1. Parotid

  2. Submandibular

  3. Sublingual

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82

What are the 2 cell types in salivatory glands?

  1. Serous acinar cells

  2. Mucous acinar cells

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83

What do mucous acinar cells do?

secrete glycoproteins

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84

What do glycoproteins do?

Make mucin

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85

What do serous acinar cells do?

secrete water, ionrganic salts and amylase

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86

Compare plasma and saliva ion levels?

lower Na+ and Cl-

higher K+ and HCO3-

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87

What’s the pH of saliva?

6.2

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88

Is saliva hyper/ hypotonic?

Hypotonic

less ions than in plasma (plasma has more functions)

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89

What is the first stage of saliva formation?

serous cells produce isotonic secretions

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90

What does the isotonic secretion contain?

Amylase

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91

What happens to the isotonic secretion?

Duct cells extract Na+ and Cl-

Add K+ and HCO3-

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92

Which division of the nervous system controls the secretion?

Parasympathetic

(salivaring at icecream is very much not flight r fight)

But sometimes you have to fight for the icecream

  • a little sympathetic

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93

Is the pancreas endocrine or exocrine?

both!

endo= insulin (that travels!)

exo= enzymes into ducts

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94

What are the two compoments of the pancreatic juices?

  1. enzymes

  2. bicarbonate (neutralises chyme)

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95

What stimulates the secretion of enzymes from the pancreas?

Secretin and ACh

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96

What produces the aqueous component of pancreatic juice?

Epithelial cells lining the duct

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97

Is the aqueous compoment hypotonic?

Nope

Isotonic

however HCO3- levels are increased due to the need to neutralise

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98

How is bicarbonate produced in the epithelial cell of the duct?

water and carbon dioxide move into the cell

bicarbonate is made

H+ fucks off into the plasma and therefore Na+enters

HCO3- goes to do its job in the duct and Cl- goes in the cell to neutralise

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99

So how is the primary aqueous secretion modified?

water addded

Na+ and HCO3- added

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100

What inactive enzymes do acinar cells release?

Trypsin

Chymotripsin

Carboxypeptidase

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