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GI lectures > important GI > Flashcards

important GI Flashcards

1
Q

what is the blood supply to the foregut?

A

coeliac trunk

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2
Q

what nerves innervate the foregut?

A

greater splanchnic nerve T5-9

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3
Q

what is the blood supply to the midgut?

A

Superior mesenteric artery

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4
Q

what nerves innervate the midgut

A

lesser splanchnic nerve T10-11

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5
Q

what is the blood supply to the hindgut

A

Inferior mesenteric artery

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6
Q

what nerves innervate the hindgut

A

least splanchnic nerve T12

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7
Q

what are rugae

A

muscular ridges on the stomachs inner surface

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8
Q

what are the 2 openings to the stomach

A

cardiac and pyloric

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9
Q

what are the 5 parts of the stomach called

A

cardia, fundus, body, antrum, pylorus

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10
Q

what are the 2 sphincters in the stomach?

A

cardiac sphincter

pyloric sphincter

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11
Q

what gives the stomach its blood supply?

A

branches of the coeliac trunk

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12
Q

blood supply to the greater curvature of the stomach

A

R & L gastroepiploic artery
(R arises from common hepatic artery via the gastroduodenal artery
L is a branch of the splenic artery)

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13
Q

blood supply to the lesser curvature of the stomach

A

R & L gastric arteries
(L is direct from coeliac trunk
R arises from the common hepatic artery)

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14
Q

where does the fundus of the stomach get it’s blood supply from?

A

short gastric arteries (branches of the splenic artery)

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15
Q

where do the common bile duct and main pancreatic duct empty into the duodenum

A

the second part of the duodenum via the major papilla and the flow is controlled by the sphincter of Oddi

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16
Q

what are the 4 parts of the duodenum

A

superior, descending, inferior, ascending

mucosa of D1 is smooth, whereas the rest has plicae circulares

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17
Q

what proportions do the jejunum and ileum comprise of

A

2/5 jejunum

3/5 ileum

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18
Q

which is wider the jejunum or ileum?

A

jejunum

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19
Q

describe the walls of the jejunum vs ileum

A 
jejunum = thick + double 
ileum = thin
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20
Q

what is the blood supply of the jejunum

A

long arteries & few vasa rectae

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21
Q

what is the blood supply of the ileum

A

short arteries & many vasa rectae

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22
Q

describe the arterial blood supply of the large intestine

A

Ascending = right colic artery from superior mesenteric artery
Transverse = middle colic artery from superior mesenteric artery
Descending – left colic artery from inferior mesenteric artery
Sigmoid = sigmoidal arteries from inferior mesenteric artery

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23
Q

describe the venous drainage of the large intestine

A 
Ascending = superior mesenteric vein
Transverse = superior mesenteric vein
Descending = inferior mesenteric
Sigmoid = inferior mesenteric vein
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24
Q

what is the difference between the longitudinal muscle layer in the small and large intestine

A

small: continuous
large: not continuous - 3 muscles called tenae coli

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25
Q

which intestine has appendices apiploicae

A

large

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26
Q

do the small and large intestines have pilicae?

A

small: yes
large: no

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27
Q

external oblique

A
  • Fibres run inferomedially (as if into your pockets)

- Function = contralateral rotation of the torso

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28
Q

internal oblique

A

Fibres run superomedially
Function = bilateral contraction compresses the abdomen
Function = unilateral contraction ipsilaterally rotates the torso

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29
Q

transversus abdominus

A

Function = compression of abdomen

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30
Q

what muscles from aponeurosis - rectus sheath

A

external/ internal oblique and transversus abdominus form rectus sheath

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31
Q

describe the abdominal wall muscles above the arcuate line

A

In front = superior oblique, some of internal oblique

Behind = some of internal oblique, transversus abdominus

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32
Q

describe the abdominal wall muscles below the arcuate line

A

All fascia lies in front

Only peritoneum & transversalis fascia behind rectus abdominus here

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33
Q

where is the transpyloric plane of addison?

A 
crosses many important structure at the level of T1
Gallbladder
Pancreas
Pylorus
Duodenal-jejunal flexure
Kidneys
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34
Q

where is McBurney’s point?

A

2/3s of the way from the umbilicus to the anterior superior iliac spine. This is where the appendix lies in the abdomen.

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35
Q

regions of the abdomen

A

right/left hypochondriac region, epigastric region, right/left lumbar region , umbilical region, right/left iliac region, hypogastric region

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36
Q

what is found in the foregut

A

oesophagus, stomach, proximal half of duodenum, liver, gallbladder & biliary tree, pancreas, spleen

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37
Q

what is found in the midgut

A

distal half of duodenum, jejunum, ileum, caecum, appendix, ascending colon, right 2/3rds of transverse colon

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38
Q

what is found in the hindgut

A

left 1/3rd of transverse colon, descending and sigmoid colon, rectum, anal canal

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39
Q

histology of the lips

A 
Outer = highly keratinized
Inner = less keratinized
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40
Q

histology of the tongue

A 
Ventral = non-keratinising squamous epithelium
Dorsal = keratinizing
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41
Q

histology of the tongue papillae

A 
Filiform - anterior 2/3
Don’t contain taste buds
Fungiform 
Mushroom-shaped, at sides & tip
Circumvallate
Dome-shaped, arranged in V-shape
V-shape separates anterior 2/3 & posterior 1/3
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42
Q

cell type in oesophagus

A

stratified squamous non-keratinising

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43
Q

cell type in stomach

A

simple columnar

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44
Q

cell type in small and large intestine and rectum

A

simple columnar

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45
Q

cell type in anal canal

A

stratified squamous - becomes keratinised at distal end

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46
Q

what are the muscle layers of the oesophagus

A

longitudinal (outer)

circular (inner)

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47
Q

what are the muscle layers of the stomach

A

longitudinal (outermost)
circular (middle)
oblique (innermost)

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48
Q

where are chief and parietal cells mainly found ?

A

body of stomach

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49
Q

layers of intestine - out to in

A

muscularis propria
submucosa
mucosa
lumen

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50
Q

histology of the duodenum

A 
Few plicae circularis
Broad and leaf-like villi
Few goblet cells
Brunner's glands - Secrete alkaline mucus, Neutralises chyme, Only found in duodenum
Long crypts
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51
Q

histology of the jejunum

A 
Close-packed plicae circularis
Long, narrow villi
Finger-like
Many goblet cells
Short crypts
Lymph nodes at lamina propria
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52
Q

histology of the ileum

A

Fewer plicae circularis
Shorter villi
Goblet cells increase towards distal end
Peyer’s patches- Large, In submucosa, Lymphoid tissue, Only found in ileum

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53
Q

histology of the colon

A 
All the colon looks the same
Little folding
No villi
Mucosa contains closely packed crypts
Abundant goblet cells
Muscularis externa
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54
Q

what is the function of saliva

A

Lubricant – for mastication
Maintaining oral pH – bicarbonate/carbonate buffer system, pH 6.2-7.4
Begin starch digestion – alpha amylase
Anti-bacterial – lysozyme

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55
Q

what are the 2 different types of secretions in salvia

A 
Mucous = mucins for lubrication
Serous = alpha amylase for starch digestion
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56
Q

parotid gland

A

Serous secretion

CN IX parasympathetic

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57
Q

sublingual gland

A

Mucous secretions

CN VII parasympathetic

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58
Q

submandibular gland

A

Mixed secretions

CN VII parasympathetic

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59
Q

minor glands

A

Predominantly mucous, some serous

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60
Q

serous acinus

A

Dark staining nucleus
Nucleus in basal third
Small central duct
Secrete: water & alpha amylase

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61
Q

mucous acinus

A 
Pale staining - “foamy”
Nucleus at base
Large central duct
Secrete: mucous (water & glycoproteins)
Found in submandibular & sublingual glands
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62
Q

what are acini

A

secretory cells

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63
Q

what are intercalated ducts

A

Connect acini to striated ducts

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64
Q

striated ducts

A

Microvilli – highly folded
Mitochondria  energy for active transport
HCO3- and K+ secreted
Na+ and Cl- absorbed

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65
Q

what do striated ducts lead to

A

interlobar (excretory) ducts

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66
Q

mucous cells

A

secrete mucous

function: lubrication, protection of mucosa

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67
Q

parietal cells

A

secrete: gastric acid (HCl) and intrinsic factor
functions: HCL - digestion, activates pepsinogen, kills pathogens
intrinsic - absorption of B12 in terminal ileum

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68
Q

chief cells

A

secrete: pepsinogen
functions: converted to pepsin - protease enzyme for digestion

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69
Q

enterochromaffin like cells

A

secrete: histamine
function: stimulates HCl secretion

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70
Q

G cells

A

secrete: gastrin
function: stimulates HCl secretion, stimulates histamine secretion

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71
Q

D cells

A

secrete: somatostatin
function: inhibits HCl secretion

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72
Q

what are the 4 stages of gastric acid secretion

A

Cephalic stage ON
Gastric stage ON
Gastric stage OFF
Intestinal phase OFF

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73
Q

intestinal phase

A 
In duodenum
Distension
Low pH
Hypertonic solutions
Amino acids + fatty acids
All decrease HCl secretion via: Parasympathetic nerve inhibition (less Ach), Somatostatin
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74
Q

conversion of pepsinogen to pepsin

A 
Converted by:
HCl
Pepsin
Moist efficient conversion when pH <2
20% of total protein digestion
Increases surface area for later digestion
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75
Q

what is the empty stomach volume

A

50 ml

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76
Q

what is the maximum stomach volume after eating

A

1.5L

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77
Q

what is gastric motility mediated by

A

Ach (parasympathetic – Vagus nerve)

Nitric Oxide & Serotonin (enteric)

78
Q

describe peristalsis

A 
Ripple movement begins in body
More powerful contraction wave in antrum
Pyloric sphincter closes
Not much chyme can enter duodenum
Antral contents forced back to body – mixing
79
Q

what do the interstitial cells of cajal do?

A

Pacemaker cells – determine frequency of peristaltic contractions
3x per minute

80
Q

what increases the strength of gastric contractions?

A

Gastrin

Gastric distension – mechanoreceptors

81
Q

what decreases the strength of gastric contractions

A 
Duodenal distension
Increase in duodenal fat
Increase in duodenal osmolarity
Decrease in duodenal pH
Increased sympathetic NS stimulation
Decreased parasympathetic NS stimulation
82
Q

what are some protective mechanisms of gastric mucosa

A

Alkaline mucus on luminal surface
Tight junctions between epithelial cells
Rapid cell replacement of damaged cells by stem cells present in base of pits
Feedback loops for regulation of gastric acid secretion

83
Q

what is the consequence of an insufficient defence of the gastric mucosa

A

peptic ulcers

84
Q

what are some causes of peptic ulcers

A

Helicobacter pylori infection
NSAIDs
Chemical irritants (alcohol, bile salts)
Gastrinoma

85
Q

what is the Basal metabolic rate (BMR)

A

The amount of energy needed to stay at live rest

Roughly = 24kcal/Kg/day

86
Q

what factors increase BMR

A

Being overweight, Fever, being male, pregnancy, caffeine, hyperthyroidism, exercise, low temperature

87
Q

what factors decrease BMR

A

Increase in Age, being female, malnutrition/starvation, hypothyroidism

88
Q

how do you calculate BMI and what is a normal BMI and obese

A

weight/height ^2
normal = 18.5-25
obese = 30-40

89
Q

what are the fat soluble vitamins

A

A,D,E,K
Absorbed along with fat – in micelles
Absorbed in ileum

90
Q

what are the water soluble vitamins

A

B,C
Absorbed in jejunum
Except B12 – terminal ileum

91
Q

vitamin B12 absorption

A

B12 ingested orally
Intrinsic factor produced by parietal cells in stomach
B12 binds to intrinsic factor
Intrinsic factor binds to specific sites on epithelia cells in terminal ileum
B12 absorbed via endocytosis

92
Q

vitamin A

A

functions: cellular growth, vision ect.
sources: liver, dairy , ect.
consequences: night blindness, growth retardation ect.

93
Q

vitamin C

A

function: collagen synthesis, antioxidant ect.
sources, citrus fruit, green veg, potatoes
consequences: scurvy, bleeding gums, aching bones

94
Q

vitamin B12

A

functions: erythrocyte formation, DNA synthesis, brain development
sources: meat & fish, eggs, milk
consequences: pernicious anaemia

95
Q

vitamin D

A

function: calcium absorption in gut, resorption in kidneys
sources: plants, UV
consequences: frequent bone fractures, muscle weakness and bone pain

96
Q

vitamin E

A

function: antioxidant, protects cell walls
sources: nuts & seed, vegetable oils
consequences: muscle weakness, degeneration of retina

97
Q

vitamin K

A

function: formation of clotting factors (1972) in liver
sources: green leafy veg, meet, eggs, cereal
consequences: gum bleeding, easy bruising

98
Q

digestion of carbohydrates

A

begins at mouth (alpha amylase at pH 6.7)
95% of digestion in small intestine (pancreatic alpha amylase via pancreatic duct - broken into disaccharides)
enzymes on luminal membranes of SI epithelial cells breakdown di into monosaccharides

99
Q

where are carbs absorbed

A

broken down into monosaccharides then absorbed into bloodstream

100
Q

protein digestion and absorption

A 
starts in stomach (pepsin pH 1.6-3.2)
small intestine (pancreatic enzymes e.g. trypsin)
digested into free fatty acids by exopeptidases 
FFA then absorbed into blood stream
101
Q

water absorption

A

80% in SI

98% of fluid load is reabsorbed

102
Q

how is sodium absorbed

A

Active transport
Co-transport with glucose, amino acids etc.
Na+ absorption enhances osmotic gradient for water absorption

103
Q

how is potassium absorbed

A

passive diffusion

104
Q

how is chloride absorbed

A

Active transport – in exchange for bicarbonate (HCO3-)

This makes the intestinal contents more alkaline

105
Q

iron storage

A

Iron is bound to TRANSFERRIN after being absorbed by duodenal epithelial cells
Most is utilised by the body, rest is stored
Most stored iron is in the liver
More specifically, in Kupffer cells
Stored in cells as FERRITIN

106
Q

iron distribution

A

50% is in haemoglobin
25% is in haem-containing proteins
25% is in liver ferritin

107
Q

glycogen storage

A

Liver maintains blood glucose levels
Excess glucose is stored as glycogen
Formation is stimulated by insulin release
Breakdown is stimulated by glucagon release
Liver is normally stores 100g of glycogen
300g is stored in skeletal muscle

108
Q

xenobiotics definition

A

A foreign chemical substance not normally found or produced in the body which cannot be used for energy requirements
e.g. drugs

109
Q

microsomes definition

A

They’re fragments of endoplasmic reticulum with attached ribosomes
microsomal enzymes are found in microsomes

110
Q

phase 1 reactions

A

Makes the drug more HYDROPHILLIC to be excreted by kidneys
Introduce/ expose hydroxyl (-OH) and other polar groups
Carried out via oxidation, reduction, and hydrolysis
Reactions facilitated by MICROSOMAL enzymes

111
Q

Cytochrome P450

A

Important type of microsomal enzyme
Uses haem group (Fe2+) to oxidise substances
Cytochrome p450 reductase - transfers electron from NADPH to CYP450 using flavoprotein

112
Q

phase 2 reactions

A

Conjugation reactions:
- Attachment of substituent groups
- Inactive products
- Catalysed by transferases
- Significantly increases hydrophilicity
Glucuronidation reactions:
Adding a glucuronic acid group
Increases hydrophilicity
Done by glucuronosyltransferase/ UGT
UDPGA is an essential co-enzyme for glucuronidation reactions
Most phase 2 reactions are done by NON-MICROSOMAL enzymes.
EXCEPT for glucuronidation which is done by a MICROSOMAL enzyme

113
Q

albumin

A

Most common plasma protein 2 main functions:
- Maintain colloid osmotic pressure
- Binding & transporting
large/hydrophobic molecules

114
Q

what is the purpose of the glucose-alanine cycle

A

The purpose of this cycle is to move proteins from muscles to the live when glycogen stores are low

115
Q

urea cycle steps

A
  1. Ammonia and CO2 are added to ornithine
  2. Another ammonia is then added to citrulline to make arginine
  3. Arginine is cleaved by arginase into urea and ornithine and the cycle goes around again
116
Q

how is energy stored

A

Triglycerides – 78%
Protein – 21%
Carbohydrate – 1%

117
Q

Low density lipoproteins (LDL)

A

Formed in plasma
Main cholesterol carrier
Delivers cholesterol to all cells in body
Essential for cell membrane and steroid hormone production

118
Q

High density lipoproteins (HDL)

A

Formed in liver
Removes excess cholesterol from blood and tissues delivering it to the liver to be secreted into bile
“Good” cholesterol

119
Q

very low density lipoproteins

A

Synthesised in hepatocytes

Deliver triglycerides from liver to adipocytes

120
Q

what does lipoprotein lipase do

A
  • Hydrolyses triglycerides in lipoprotein into 2 free fatty acids and 1 monoglyceride molecule
121
Q

what does hepatic lipase do

A 
Found in the liver and adrenal glands
Converts IDL (intermediate density lipoprotein) into LDL thereby packaging it with more triglycerides to be released in the body
122
Q

where does fatty acid beta oxidation occur and what is it

A

It is the catabolism of fatty acids to produce energy

Occurs in mitochondria of hepatocytes

123
Q

bile

A

Produced and secreted by LIVER hepatocytes
Emulsifies fats
Excretory pathway e.g. hormones
Stored and concentrated in the GALL BLADDER by absorbing NaCl & H2O
Secreted under the action of cholecystokinin (CCK)
CCK released in response to increased fatty acid conc in duodenum

124
Q

bile constituents

A 
Bile salts
Lecithin (a phospholipid)
HC03-
Cholesterol
Bile pigments e.g. bilirubin
125
Q

Enterohepatic circulation

A

95% of secreted bile salts are recycled
Bile salts enter intestinal tract via bile
Reabsorbed by Na+ coupled transporters
Majority of reabsorption is in terminal ileum and some in jejunum
Returned to liver by hepatic portal vein (HPV) to be used again in bile
Small amount of bile salts escape (5%)
Liver synthesises new bile salts from cholesterol

126
Q

what colour is bilirubin

A

yellow

127
Q

what do old erythrocytes break down into

A

heam and globin then heam forms bile pigments e.g. bilirubin

128
Q

stages of bilirubin metabolism

A
  1. RBCs ingested by macrophages/ Kupffer cells
  2. Haemoglobin broken down into haem and globin
  3. Globin broken into amino acids – used to make new RBCs in bone marrow
  4. Haem is further broken down into biliverdin and Fe2+ & CO. Catalysed by haem oxygenase (HO)
  5. Biliverdin (green pigment) is reduced by biliverdin reductase to make unconjugated bilirubin
  6. Unconjugated bilirubin (UCB) is bound to albumin and transported to liver
  7. Undergoes glucuronidation to make conjugated bilirubin. Catalysed by enzyme UDP Glucuronyl Transferase (UDPGT)
  8. Conjugated bilirubin (CB) is now soluble and is dissolved in bile
  9. Excreted into the duodenum with the rest of the bile
  10. Intestinal bacteria in terminal ileum REDUCE the CB into urobilinogen
  11. Urobilinogen is lipid-soluble. 10% is reabsorbed into blood, bound to albumin, transported to liver, and oxidised to urobilin
  12. Urobilin is re-cycled into bile or transported to kidneys and excreted in urine (responsible for yellow urine colour)
  13. Remaining 90% of urobilinogen is OXIDISED by a different intestinal bacteria into stercobilin
  14. Stercobilin is excreted in the faeces (responsible for brown colour)
129
Q

what are the exocrine functions of the pancreas

A

Acini of pancreas produce digestive enzymes

Released via pancreatic duct into duodenum

130
Q

what are the endocrine functions of the pancreas

A

Islet of Langerhans produce insulin, glucagon & somatostatin

Large role in regulating glucose

131
Q

what does the exocrine pancreas secrete ?

A

HCO3- (bicarbonate) – neutralises chyme
Digestive enzymes
Zymogens (precursor enzymes)

132
Q

HCO3 - secretion from pancreas

A

Protects duodenum from gastric acid
Buffers chyme to a suitable pH
Stimulated by secretin release
Pancreatic duct cells secrete HCO3- into the duct lumen via Cl-/HCO3- exchanger
HCO3- comes from the disassociation of H2CO3 (carbonic acid)
The Cl- is recycled back into the lumen via a CFTR channel

133
Q

what is CCK

A

principle stimulus for delivery of pancreatic enzymes into duodenum

134
Q

cephalic phase of secretion

A

Sensory experience
Seeing and eating food
Parasympathetic vagus nerve stimulation to acinar cells
Produce digestive enzymes

135
Q

gastric phase of secretion

A

Presence of food within stomach
Parasympathetic X nerve stimulation to acinar cells
Produce digestive enzymes

136
Q

where does the foregut start and end?

A

mouth to common bile duct

137
Q

where does the midgut start and end?

A

common bile duct to 2/3rds of the transverse colon

138
Q

where does the hindgut start and end?

A

2/3rds transverse colon to the anal canal

139
Q

what 2 planes does embryonic folding occur and in what week ?

A

horizontal - 2 lateral body folds
medial - cranial + caudal
week 4

140
Q

what forms the GI tract (embryology)

A

endoderm + visceral mesoderm

141
Q

how is the primitive gut tube formed?

A

endoderm moves towards the midline and fuses - incorporating the dorsal part of the yolk sac

142
Q

what does the endoderm give rise to in the GI tract?

A

epithelial lining of digestive tract
hepatocytes of the liver
endocrine and exocrine cells of the pancreas

143
Q

what does the visceral mesoderm give rise to in the GI tract?

A

muscle, connective tissue & peritoneal components of the wall of the gut
connective tissue for the glands

144
Q

describe how the mouth arises from the foregut

A

embryo is temporarily closed by the oropharyngeal membrane which at the end of week 4 ruptures to form the mouth

145
Q

describe the formation of the vitelline duct

A

midgut is connected to yolk sac then at week 5 the folding continues, yolk sac narrows into a stalk - vitelline duct

146
Q

describe how the anus arises from the hindgut

A

hindgut temporarily closed by cloacal membrane - 7w this ruptures to form the anus

147
Q

where do the pharyngeal arches extend from

A

oropharyngeal membrane to respiratory diverticulum

148
Q

what week do the pharyngeal arches develop

A

4th & 5th

149
Q

what are the pharyngeal arches formed from

A

mesenchymal tissue which are invaded by cranial neural crest cells

150
Q

describe the coverings of the pharyngeal arches

A

external - endoderm (pharyngeal clefts)

internal - ectoderm (pharyngeal pouches)

151
Q

1st pharyngeal arch - innervation, muscles, bone

A
  • Innervation: Mandibular nerve (V3 - i.e third branch of trigeminal (V) • Muscles: mastication, tensor tympani, digastric, myolohyoid
  • Bone: maxilla, mandible, incus, malleus
152
Q

2nd pharyngeal arch - innervation, muscles, bone

A
  • Innervation: Facial nerve (VII)
  • Muscles: facial expression, stapedius, stylohyoid
  • Bone: stapes, styloid and lesser horn of hyoid cartilage
153
Q

3rd pharyngeal arch - innervation, muscles, bone

A
  • Innervation: Glossopharyngeal nerve (IX)
  • Muscles: stylopharyngeus of the pharynx
  • Bone: body & greater horn of hyoid cartilage
154
Q

4th pharyngeal arch - innervation, muscles, bone

A
  • Innervation: Superior laryngeal nerve of Vagus nerve (X)
  • Muscles: Cricothyroid
  • Bone: thyroid cartilage & epiglottic cartilage
155
Q

6th pharyngeal arch - innervation, muscles, bone

A
  • Innervation: Recurrent laryngeal nerve of Vagus nerve (X)
  • Muscles: All muscles of the larynx except the cricothyroid
  • Bone: cricoid cartilage, arytenoid cartilages, corniculate & cuneiform cartilage
156
Q

describe the development of the oesophagus

A

w4 - respiratory diverticulum gets divided by tracheoesophageal septum into respiratory primordium and dorsal oesophagus

157
Q

describe the dorsal mesentery (embryology)

A

lower foregut, midgut, major part of hindgut - suspended from posterior abdominal wall

158
Q

describe the ventral mesentery (embryology)

A

foregut - derived from septum transversum - liver develops in it and later divides it into the lesser omentum and falciform ligament

159
Q

what causes the thinning of the dorsal mesentery

A

stomach rotations - is now called greater omentum

160
Q

what is the epiploic foramen

A

small opening where the greater and lesser sacs can communicate

161
Q

innervation of the nasopharynx

A

maxillary nerve

162
Q

innervation of the oropharynx

A

IX (glossopharyngeal)

163
Q

innervation of the laryngopharynx

A

X (vagus)

164
Q

first stage of swallowing

A

voluntary
food compressed against roof of mouth and pushed back by tongue
buccinator & supra hyoid muscles manipulate food and elevate hyoid bone - flatten floor of mouth

165
Q

second stage of swallowing

A

involuntary
nasopharynx closed by soft palate being elevated
- Impulses from the swallowing centre
inhibit respiration, raise the larynx and close the glottis - keeping food from entering
the trachea
As the tongue forces the food farther back
into the pharynx the food tilts the epiglottis
backward to cover the closed glottis -

166
Q

third stage of swallowing

A

involuntary
The sequential contraction of the constrictor muscles (circular) followed by the depression (return) of the hyoid bone and pharynx
Before food can enter the oesophagus the upper oesophageal sphincter relaxes - immediately after the food has passed through the sphincter closes, the glottis opens and breathing resumes

167
Q

describe the gag reflex

A
  • The reflex elevation of the pharynx - often followed by vomiting cause by irritation of the oropharynx - the back of the tongue
  • Reflex arc between the glossopharyngeal (IX) and the vagus (X) nerves
168
Q

factors affecting the composition & amount of saliva produced

A 
circadian rhythm 
type & size of gland 
duration and type of stimulus 
diet
drugs 
age 
gender
169
Q

what salivary glands are continuously active?

A

submandibular
sublingual
minor

170
Q

what are unstimulated components of the salivary system dominated by?

A

submandibular components

171
Q

when does the parotid gland become the main source of saliva

A

only when stimulated

172
Q

where is the parotid gland located?

A

between:
- Zygomatic arch
- Sternocleidomastoid
- Ramus of mandible

173
Q

where is the parotid duct located?

A

crosses masseter muscle and pierces through the buccinator muscle
opens near 2nd upper molar

174
Q

what structures pass through the parotid?

A
  • External carotid artery
  • Retromandibular vein
  • Facial nerve
175
Q

describe the anatomy of the submandibular glands

A

Two lobes separated by mylohyoid muscle - larger superficial lobe and a smaller deep lobe in the floor of the mouth
empties at the sublingual papillae

176
Q

where are the sublingual glands located?

A

Located in the floor of the mouth between mylohyoid muscles and oral mucosa of floor of mouth

177
Q

what is secreted in the glands in the upper , thin portions of the body of the stomach

A

mucous, hydrochloric acid (parietal cells) and the enzyme precursor pepsinogen (chief cells)

178
Q

what is secreted in the lower thicker antrum of the stomach

A

gastrin

179
Q

what is pepsinogen mediated by

A

input from the enteric
nervous system via neurotransmitter ACh
(parasympathetic)

180
Q

what is gastroparesis

A

delayed gastric emptying

181
Q

what is the absoptive state

A
  • During which ingested nutrients enter the blood from the GI tract - During this state, some of the ingested nutrients provide the energy requirements of the body and the remainder is added to the body’s energy stores to be called upon during the next postabsorptive state
182
Q

what is the postabsorptive state

A

During which the GI tract is empty of nutrients and the body’s own stores must supply energy

183
Q

what is a microsome

A

small particle consisting of endoplasmic reticulum to which ribosomes are attached

184
Q

what is an example of a microsomal enzyme

A

Cytochrome P450

185
Q

describe non-microsomal enzymes

A

mainly phase II reactions
located in the cytoplasm and mitochondria of hepatocytes in the liver
involved in all conjugation reactions except glucuronidation
e.g. protein oxidases

186
Q

lipophilic definition

A

to be able to pass through plasma membranes to reach metabolising enzymes

187
Q

what is glucuronidation

A

adding a glucuronic acid group to the drug to make it more hydrophilic

188
Q

what is produced in overdose of paracetamol

A

NAPQI

189
Q

what are the 4 starling forces

A
  1. Capillary hydrostatic pressure (favouring fluid movement out of the
    capillary)
  2. Interstitial hydrostatic pressure (favouring fluid movement into the
    capillary
  3. Osmotic force due to plasma protein concentration (favouring fluid
    movement into the capillary)
  4. Osmotic force due to intestinal fluid protein concentration (favouring
    fluid movement out of the capillary
190
Q

describe lysosomal protein breakdown

A

reticulo-endothelial system of the liver
Sinusoidal endothelial cells remove soluble proteins and fragments from the blood
through the fenestrations known as sieve plates on their luminal surface - they are
important for removing; fibrin, fibrin degradation products, collagen & IgG
complexes. In liver these proteins are fused into lysosomes - containing lysozyme which are hydrolytic enzymes that break down the protein into
amino acids
- Kupffer cells - phagocytose particulate matter thereby packaging them in to phagosomes in the cell which contain hydrolytic enzymes which will break down the protein into amino acids

191
Q

ubiquitin-proteasome pathway

A

cytoplasm of cells
Proteins targeted for degradation by the attachment of ubiquitin to the protein. directs the protein to a
proteasome - which unfolds the protein and breaks it
down into small peptides

192
Q

what is in the hepatic triad

A

hepatic artery and vein & common bile duct

GI lectures (16 decks)

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