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Gastrointestinal > Alimentary Canal Physiology Pt.1 > Flashcards

Alimentary Canal Physiology Pt.1 Flashcards

1
Q

What is the digestive system

A

It is a system made up of the GIT and accessory organs

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2
Q

Names path of food going through the GIT

A

Oesophagus
Stomach
Duodenum
Jejunum
Ileum
Cecum
Ascending colon
Transverse colon
Descending colon
Sigmoid colon
Rectum
Anus

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3
Q

Name the accessory organs in the alimentary canal

A

salivary glands
liver
pancreas
gallbladder

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4
Q

What are the 4 main functions of the digestive system

A

digestion
absorption
secretion
motility

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5
Q

Is lumen of the GIT considered external or internal to the body

A

external

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6
Q

What is the function of the mouth

A

Foodstuffs broken down by chewing
saliva added as lubricant

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7
Q

What is the function of the oesophagus

A

Conduit between mouth and stomach

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8
Q

What is the function of the stomach

A

Digestion of proteins
foodstuffs reduced to semi-liquid form
storage
sterilisation

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9
Q

What is the function of the pancreas

A

Digestive enzymes for digestion of fats, carbohydrates and proteins

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10
Q

What is the function of the liver

A

Bile salts for digestion/absorption of fats in small intestine

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11
Q

What is the function of the gallbladder

A

Stores and concentrates bile

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12
Q

What is the function of the small intestines

A

Final stages of chemical digestion and nutrient absorption

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13
Q

What is the function of the large intestines

A

Water absorption
bacterial fermentation
formation of faeces

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14
Q

What are the four layers (tunics) of the GIT

A

Mucosa
Sub mucosa
Muscularis externa
Serosa/adventitia

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15
Q

What are the 3 layers of the mucosa and functions

A

Epithelium - lining of GIT (protection), Synthesis and secretion of digestive enzymes, hormones, mucus, absorbs products of digestion (function changes through out the tract
Lamina propria - loose connective tissue containing glands, blood and lymph vessels
Muscularis mucosae - thin layer of smooth muscle

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16
Q

What structures are found in the sub mucosa

A

connective tissue
neurones (sub mucosal plexus), blood vessels
glands in oesophagus and duodenum

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17
Q

What are the layers of the muscularis externa

A

Oblique muscle (in stomach)
circular muscle (constricts lumen)
longitudinal muscle (shortens tube)

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18
Q

What two plexus’s makes up the ENS and where are they found

A

Myenteric (Auerbach’s) plexus - found between longitudinal and circular muscle
Sub mucosal (Meissner’s) plexus - found between the circular muscle and submucosa

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19
Q

What is the difference between serosa and adventitia

A

Adventitia is found out with the peritoneal cavity eg. oesophagus, rectum
Serosa is found within the peritoneal cavity eg. stomach, small intestines, large intestines

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20
Q

What type of tissue is serosa

A

Connective tissue

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21
Q

Are long and short reflexes parasympathetic or ENS

A

Long - parasympathetic
short - ENS

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22
Q

Which parasympathetic nerves innervate the GIT

A

Vagus (X)
salivary glands - facial (VII) + glossopharyngeal (IX)

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23
Q

What is the effect of parasympathetic innervation on the GIT

A

Stimulatory
- increased secretion
- increased motility

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24
Q

Which sympathetic nerves innervate the GIT

A

Splanchnic nerves

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25
What is the effect of sympathetic innervation on the GIT
Inhibitory (except salvation) - decrease secretion - decreased motility
26
What are the - 3 abdominal branches of the aorta - their vertebral level - which organs do they supply
Coeliac trunk (T12) - foregut Superior mesenteric artery (L1) - midgut Inferior mesenteric artery (L3) - hindgut
27
What are the 3 main branches of the coeliac trunk
Splenic artery Left gastric artery Common hepatic artery
28
What veins drain the GIT
Gastric vein Splenic vein Superior mesenteric vein Inferior mesenteric vein
29
Where does venous drainage of GIT go
Hepatic portal vein => Hepatic vein => IVC
30
Why do we chew our food
Prolong tasting experience Defence against respiratory failure
31
Is chewing involuntary or voluntary Which nerves are used
Voluntary Somatic nerves of skeletal muscle in jaw/mouth
32
How many salivary glands do we have
3 pairs Sublingual glands Submandibular glands Parotid glands
33
What is in saliva What is its function
Water - solvent Mucins - added to water -> mucus alpha amylase - breaks down polysaccharides Electrolytes - tonicity/pH Lysozymes - bactericidal
34
What do serious alveoli produce
Alpha amylase and lysosomes
35
What do mucous alveoli produce
Mucins
36
Histologicially, what are salivary glands similar to
Pancreatic cells
37
Is stimulation of salivary glands sympathetic or parasympathetic
Both
38
What is the difference between salivary glands stimulation in sympathetic and parasympathetic
Sympathetic - small volume of viscous secretion - high mucous content (a1 adrenoreceptors) - high amylase content (B2 adrenoreceptors) Parasympathetic - watery salivary secretion
39
Which parasympathetic nerves stimulate salivary glands
Facial (VII) nerves Glossopharyngeal (IX) nerves
40
Does the oesophagus have skeletal or smooth muscle
Upper 1/3 - skeletal muscle Lower 2/3 - smooth muscle
41
How many phases of swallowing are there
3 phases Oral Pharyngeal Oesophagus
42
When swallowing why does the soft palate reflect backwards and upwards
Stops food going in to the nasopharynx
43
Why does the epiglottis cover larynx during swallowing
Prevents food from entering the trachea
44
What propels bolus (food) down the oesophagus
Peristaltic wave
45
How many oesophageal sphincters are there
2 sphincters Upper oesophageal sphincter Lower oesophageal sphincter
46
What is the stomach volume How does the pressure change
50ml -> 1500ml No change in pressure
47
What is the function of the stomach fundus
Storage
48
What is the function of the stomach body
Storage Mucus HCl Pepsinogen Intrinsic factor
49
What is the function of the stomach antrum
Mixing/Grinding Gastrin production from G cells
50
Which cells in the stomach produce mucus
Mucus neck cells
51
Which cells in the stomach produce pepsinogen
Chief cells
52
Which cells in the stomach produce HCl and intrinsic factors
Parietal cells
53
What is the name of the sphincter that controls food movement from the stomach to the duodenum
Pyloric sphincter
54
In HCl production CO2 is absorbed from the blood and mixes with H20 to produce which compound What enzyme catalyses the reaction What does it dissociate to produce
H2CO3 Carbonic anhydrase H+HCO3
55
In HCl production as bicarbonate is pumped out of the cell what is being pumped in to the cell
Chlorine Cl
56
To pump H ions in to the stomach what is being pumped in to the cell
Potassium K
57
How does parietal cell production of HCl affect pH of blood
Increases pH of blood slightly >7.4
58
Which medications can inhibit the H/K proton pump in parietal cells (and stopping HCl production)
PPIs E.g Omeprazole, esomeprazole, lansoprazole Antihistamines
59
What process activates the parietal cells H/K pump What enzyme causes this reactions
Phosphorylation Kinase
60
What four chemicals alter the amount of kinase in the cell
Gastrin Histamines Prostaglandins Acetylcholine
61
What receptor does gastrin bind to which alters the amount of kinase and how does the receptor work How does it alter the amount of Kinase Which type of kinase is produced
Cckb receptor - Increases Ca in the cell Increases kinase Protein kinase C
62
What receptor do histamines bind to which alters the amount of kinase and how does the receptor work How does it alter the amount of Kinase Which type of kinase is produced
H2 receptor - activates GS receptor->activates adenyl cyclase-> increase ATP converted to cAMP-> cAMP activates Kinase Increase kinase Protein Kinase A
63
What receptor do neurotransmitters (e.g. acetylcholine) bind to which alters the amount of kinase and how does the receptor work How does it alter the amount of Kinase Which type of kinase is produced
M3 muscarinic receptors (parasympathetic) - increases Ca in the cell Increases kinase Protein kinase C
64
What receptor do prostaglandins bind to which alters the amount of kinase and how does the receptor work How does it alter the amount of Kinase Which type of kinase is altered
EP3 receptors - activates G protein (GI)-> inhibits conversion of ATP to cAMP Decreases kinase Protein kinase A
65
Which three mechanisms control gastric acid secretion
Neurocrine - vagal/local reflex Endocrine - gastrin Paracrine - histamine
66
How many phases for gastric acid secretion stimulation are there What are they
Two Cephalic and gastric
67
Explain the cephalic phase for gastric acid secretion stimulation
Increased vagus nerve stimulation will produce acetylcholine and stimulate G cells to produce gastrin Also ECL cells produce histamines
68
Explain the gastric phase for gastric acid secretion stimulation
Distension-> vagal/enteric reflex-> produces ACh Peptides in lumen->G cells-> gastrin Gastrin/ACh-> ECL cells-> histamines
69
Why does acid secretion have to start before we begin eating
To sterilise food as soon as it is in our stomach
70
How many phases for gastric acid secretion inhibition are there What are they
Three Cephalic, Gastric, Intestinal
71
Explain the cephalic phase for gastric acid secretion inhibition
Stop eating-> decreased vagal activity
72
Explain the gastric phase for gastric acid secretion inhibition
Decreased pH (increased HCl concentration) -> decreased gastrin production
73
Explain the intestinal phase for gastric acid secretion inhibition
Acid in duodenum-> ENS reflex and secretin release-> decreased secretion and stimulation of parietal cells Fat/CHO in duodenum -> GIP release-> decreased secretion and stimulation of parietal cells
74
What are enterogastrones Name the three enterogastrones
Hormones released from gland cells in duodenal mucosa, released in response to acid, hypertonic solutions, fatty acids and monoglycerides in duodenum Seretin, chloecystokinin (CCK), gastric inhibitory peptide (GIP)
75
How do enterogastrones prevent further acid build up
Inhibits gastric acid secretion Reduce gastic emptying (inhibits motility)
76
What is a zymogen Give an example
Inactive form of an enzyme Pepsinogen, trypsinogen
77
What is the zymogen pepsinogen converted into What is the function of the enzyme
Pepsin Digests proteins in ingested food
78
What conditions are required to convert pepsinogen to pepsin Is the process reversible Why
pH <3 (acidic) Yes (at neutral pH) To protect the duodenum from damage
79
What is the role of gastric mucus
Cytoprotective role Protects mucosal surface from mechanical injury Neutral pH protects against gastric acid corrosion and pepsin digestion
80
What is produced by parietal cells and is essential for vitamin B12 absorption
Intrinsic factor
81
Where in the stomach do peristaltic waves take place
Weak in body Strong in the antrum
82
How many peristaltic waves are there a minute
Approx. 3/minute
83
What is the slow peristaltic wave rhythm called
Basic electrical rhythm (BER)
84
What generates the peristaltic rhythm Where are they found
Pacemaker cells in the longitudinal muscle
85
What determines contraction strength of peristaltic waves
The number of action potentials/wave
86
What types of control are there for peristaltic waves of the GIT
Neural - wall distention-> long/short reflexes-> increases contraction force Hormonal - gastrin Fat/amino acids/acids/hypertonicity in duodenum - motility inhibited
87
Why must acid be neutralised in the duodenum
Acid can damage duodenal walls and pancreatic enzymes
88
Where is bicarbonate (HCO3) produced
Duodenum - Brunner's glands
89
What causes HCO3 secretion what happens once acid is neutralised
Long (vagal) and short (ENS) reflexes Release of secretin from S cells (HCO3 secretion from liver and pancreas) Secretin inhibition (negative feedback)
90
What two types of hormones are produced by the pancreas
Exocrine and endocrine
91
Name the endocrine hormones and function of the pancreas Where in the pancreas are they produced
Insulin - decrease blood glucose Glucagon - increase blood glucose Somatostatin - controls insulin and glucagon secretion Pancreatic islets
92
Where do endocrine hormones from the pancreas go to How do they move there
Bloodstream Vein
93
What are endocrine hormones What are exocrine hormones
Endocrine - hormones go to bloodstream Exocrine - go to an epithelial surface
94
Name exocrine proteins of the pancreas and its function
Pancreatic amylase - breakdown of starch into maltose Digestive enzymes
95
Where are exocrine products of the pancreas produced
Acinar cells in lobules
96
Where do pancreatic exocrine products go How do they move there
Duodenum Via pancreatic duct (accessory duct in case of problems)
97
What is trypsinogen converted into What enzyme aids this process
Trypsin Enterokinase
98
What is the function of trypsin
Converts zymogens to enzymes
99
What are the categories of pancreatic enzymes
Protease Nuclease Elastase Phospholipase Lipase Alpha amylase
100
What does CKK control How does it achieve this
Digestion of fats and proteins Increases enzyme secretion
101
What does Secretin control How does it achieve this
Acid neutralisation Increases bicarbonate secretion
102
What is the largest internal organ
Liver
103
What are the four lobes of the liver
Left Right Caudate Quadrate
104
Portal hepatic vein-> ? -> IVC
Hepatic veins
105
What is the function of the liver
Production and secretion of bile
106
What are the 6 components of bile Where are they synthesised
Bile acids Lecithin Cholesterol Bile pigments Toxic metals Bicarbonate HCO3 Synthesised by hepatocytes except HCO3 (duct cells)
107
What are bile pigments produced from
Haemoglobin (damaged erythrocytes)
108
What is the most common bile pigment What colour does it make bile what extracts it
Bilirubin Yellow Hepatocytes
109
What causes the yellow colour of urine
Reabsorbed bilirubin that is excreted in the urine
110
What are bile acids synthesised from
Cholesterol
111
Bile acids conjugate with glycine or taurine What is the product Why do they conjugate
Bile salts Increase solubility
112
How are secreted bile salts recycled
Enterohepatic circulation
113
Where is bile stored and concentrated How is it concentrated How many times concentrated is it
Gallbladder Na and H20 are absorbed into the gallbladder 5-20x concentrated
114
Fat in the duodenum leads to the release of CCK How does CCK work
Relaxes sphincter of Oddi Contracts the gallbladder Bile is discharged into the duodenum Solubilises fat
115
How long is each section of the small intestines
Duodenum - 25cm Jejunum - 2.5m Ileum - 3.5m
116
Name functions of each part of the small intestines
Duodenum - Gastric acid neutralisation, digestion, iron absorption Jejunum - Nutrient absorption (95%) Ileum - NaCl/H20 absorption -> chyme dehydration, Vit B12 absorption
117
What increases surface area of the small intestines Why is this important
Fold, villi, microvilli Increases absorption
118
What is absorbed in the small intestines
NaCl, peptides, mineral, vitamins, fats, monosaccharides, amino acids, water,
119
Where does secretion take place in the small intestines
Crypts
120
What is secreted by crypts of the intestines
Chorine Water (1500ml/day) - reabsorbed by villi
121
What is the purpose of water secretion in the intestines
Maintains liquid state of luminal contents Promotes mixing of enzymes with digestive contents Aids nutrient presentation to absorbing surface Dilutes + washes away potential injurious substances
122
What are the two types of intestinal motility and there functions
Segmentation - provide mixing of contents and enzymes - brings chyme into contact with surfaces Peristalsis - Migrating motility complex (MMC) - gastric antrum -> terminal ileum (1 wave at a time) - moves undigested material - limits bacterial colonisation
123
Does segmentation get stronger or weaker as it travels towards the rectum
Weaker
124
What hormone causes peristalsis
MMC hormone - motilin
125
Do peristalsis and segmentation take place at the same time When do they start
No Segmentation starts once food reaches the stomach Peristalsis begins once segmentation ends
126
What plexus mediates the intestinal motility
Myenteric plexus (between circular and longitudal muscle layers of muscularis externa
127
What leads to increased segmentation activity in the ileum
Gastric emptying
128
Explain the gastroileal reflex
Ileolcecal valve opens Chyme enters the large intestines Colon distends Reflex contraction of ileocecal sphincter (prevents back flow)
129
How long is the colon
1.5-1.8m
130
Which muscle layer of the colon is complete and which is incomplete
Complete - circular Incomplete - longitudinal
131
What are the three bands of muscle the run the full colon called
Tenaie coli
132
What are the pouches in the colon called
Haustra
133
What type of epithelium is found in the colon mucosa
Simple columnar epithelium
134
What are the sections of the colon called
Cecum Ascending Transverse Descending Sigmoid
135
What is the rectum
Straight muscular tube
136
Is the muscularis externa of the rectum thicker or thiner compared to the rest of the GIT
Thicker
137
What type of epithelium is found in the rectum mucosa
Simple columnar epithelium
138
What type of epithelium is found in the anal canal mucosa
Simple columnar->stratified squamous
139
How long is the anal canal
2-3cm
140
Is the external anal sphincter smooth or skeletal muscle Is the sphincter under voluntary or involuntary control
Skeletal muscle Voluntary control
141
Does the colon have a role in nutrient absorption
No
142
What are the functions/characteristics of the colon
Transports Na from the lumen to the blood->osmotic absorption of water->chyme dehydration->solid faecal pellets Long residence time in the colon - bacterial colonisation
143
How many bacteria are found in the colon
1000000000000000 (10 to the power of 14) (approx. 1kg)
144
What is the function of the bacteria in the colon
Fermentation of undigested carbohydrates - short chain fatty acids - vitamin K - gas flatus
145
What gases are produced by the bacteria of the colon
Nitrogen, CO2, hydrogen, methane, hydrogen sulphide
146
What is the function of vitamin K
Blood clotting
147
Is the internal anal sphincter smooth or skeletal muscle Is the sphincter under voluntary or involuntary control
Smooth Automatic/involuntary
148
What cause the defection reflex
Rectal wall distention->mechanoreceptors->reflex-> defecation urge
149
Which parasympathetic nerves control the defecation reflex
Pelvic splanchnic nerves

Gastrointestinal (4 decks)

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