Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

2nd Year > GI physiology > Flashcards

GI physiology Flashcards

1
Q

What are the 4 functions of the digestive system

A

Digestion (mechanical breakdown of food)
Secretion ( chemical breakdown)
Absorption (nutrients taken from outside your body and transferred into your body)
Motility (muscular aspect to allow everything to be pushed along)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What happens in the mouth

A

Foodstuffs broken down by chewing; saliva added as lubricant

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Whats the function of the oesophagus in digestion

A

conduit between mouth and stomach

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the stomachs function in digestion

A

Digestion of proteins; foodstuffs reduced to liquid form; storage; sterilisation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the pancreas function in digestion

A

Digestive enzymes for digestion of fats, carbs and proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the Livers function in digestion

A

Bile salts for digestion/absorption of fats in small intestine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Function of gallbladder

A

Stores and concentrates bile

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Function of small intestine in digestion

A

Final stages of chemical digestion and nutrient absorption

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Function of the Large intestine in digestion

A

Water absorption, bacterial fermentation and formation of faeces

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are the 4 distinctive layers of the alimentary canal

A
  1. Mucosa: epithelium, lamina propria, muscularis mucosa
  2. Submucosa
  3. Muscularis externa
  4. Serosa/adventitia
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What type of epithelium is present in the mouth, oesophagus, and anal canal

A

Stratified squamous

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What type of epithelium is present in stomach, small and large intestine

A

Simple columnar

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is Lamina propria

A

Loose connective tissue (glands, blood/lymph vessels)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is Muscularis mucosa

A

Thin smooth muscle layer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is Submucosa

A

Thick, irregular connective tissue which supports mucosa

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is serosa / adventitia

A

Connective tissue outer layer of alimentary canal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What does serosa do outside the peritoneal cavity

A

Attaches oesophagus and rectum to surrounding structures

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What does serosa do inside the peritoneal cavity

A

Surrounds stomach, small intestine and large intestine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is muscularis external

A

Two concentric thick layers of smooth muscle:
Inner layer = circular muscle (constricts lumen)
Outer layer = longitudinal muscle (shortens tube)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Where is the myenteric plexus

A

Between circular and longitudinal muscle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What do the submucosal and myenteric plexus make

A

enteric nervous system (ENS) = independent control of gut function

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Nervous control of alimentary function:
Long Parasympathetic
1.What nerve and 2.how does it affect secretion and motility

A
  1. Vagus nerve ( except salivation)

2. Increase secretion and motility

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What are SHORT ENS reflexes

A

Just within the gut wall itself - CNS not involved in processes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Sympathetic control:

1. What nerve and 2. How does it affect secretion and motility

A

Inhibitory (except salivation)

  1. splanchnic nerve
  2. decreases secretion and motility
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Arterial supply to GI tract:

Celiac trunk supplies what structures?

A

Stomach
Small intestine
Pancreas
Liver

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Superior mesenteric artery supplies what structures?

A

Small intestine
Caecum
Ascending colon
Transverse colon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Inferior mesenteric artery supplies what structures

A

Descending colon
Sigmoid colon
Rectum

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Venous drainage from GI tract:

Where does the stomach drain to

A

Gastric veins - hepatic portal vein - hepatic vein - IVC

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

Where does the pancreas drain to

A

Splenic vein - hepatic portal vein - hepatic vein - IVC

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Where do the small intestine, caecum, ascending colon and transverse colon drain to

A

Superior mesenteric vein - hepatic portal vein - hepatic vein - IVC

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Where do the descending colon, sigmoid colon, rectum drain to

A

Inferior mesenteric vein - hepatic portal vein - hepatic vein - IVC

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

What 2 sugars make lactose and what enzyme is involved

A

glucose and galactose

enzyme = lactase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

What 2 sugars make sucrose and what enzyme is involved

A

glucose and fructose

enzyme = sucrase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

What 2 sugars make maltose and what enzyme is involved

A

Glucose and Glucose

enzyme = maltase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

What 2 sugars have a-1,4 glycosidic bonds

A

starch

glycogen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

What sugar has B-1,4 glycosidic bonds

A

cellulose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

Where is the brush border and what does it do

A

In the apical membrane

Increasing surface area

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

What do proteases or peptidases do

A

Enzymes which hydrolyse peptide bonds and reduce proteins or peptides to amino acids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

What do endopeptidase act on

A

The interior of the protein

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

What do exopeptidase act on

A

On the terminal amino acids - getting one shorter each time - can work at either end

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

What is NHE3

A

hydrogen and sodium exchange

roughly 70% of protein in diet comes in this way

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

Almost all ingested fat is in the form of what

A

Triacylglycerol (insoluble in water)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

All fat digestion in small intestine is by what

A

Pancreatic lipase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

What is lipase

A

Water-soluble enzyme

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

What is emulsification

A

dividing large droplets into smaller droplets.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

What does emulsification require

A

mechanical disruption
emulsifying agent
bile salts and phospholipids
amphipathic molecules

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

What are micelles

A

similar to emulsion droplets but much smaller

= bile salt + monoglycerides +fatty acids + phospholipid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

Describe micelle breakdown

A

Release of small amounts of free fatty acids and monoglycerides into solution - diffusion across plasma membrane of absorbing cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

Dynamic equilibrium between fatty acids and monoglycerides in solution and in micelles does what?

A

retains most of fat digestion products in solution while constantly replenishing supply of free molecules for absorption

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
50
Q

What is a chylomicron

A

Extracellular fat droplet - contain phospholipid, cholesterol and fat soluble vitamins.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
51
Q

How do chylomicrons travel

A

Pass into lacteals between endothelial cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
52
Q

How are triacylglycerol droplets transported through the cell

A

In vesicles formed from Smooth endoplasmic reticulum - processed through golgi apparatus and exocytosed into extracellular fluid at serosal membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
53
Q

What are the fat soluble vitamins

And how are they absorbed

A

A,D,E,K

Follow same absorptive path as fat

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
54
Q

What are the water soluble vitamins

and how are they absorbed

A

B group, C and folic acid

Absorbed by passive diffusion or carrier - mediated transport

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
55
Q

What is Vitamin B-12 and what does it bind to in the stomach

A

Large charged molecule

Binds to intrinsic factor in stomach to form complex which is absorbed via specific transport mechanism in distal ileum

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
56
Q

Where is iron transported

A

Across brush border membrane (via DMT1) into duodenal enterocytes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
57
Q

Where is unbound iron transported

A

Across serosal membrane to the blood

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
58
Q

What does iron in blood bind to

A

Transferrin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
59
Q

How is ferritin expression regulated

A

Body iron status

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
60
Q

What is hyperaemia

A

Increased ferritin levels - more iron bound in enterocytes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
61
Q

What is anaemia

A

Decreased ferritin levels - more iron released to blood

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
62
Q

Why do we chew

A

Prolong taste

defence against resp failure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
63
Q

How is chewing controlled

A
  1. Voluntary - somatic nerves - skeletal muscles of mouth and jaw
  2. Reflex - contraction of jaw muscles - pressure of food against gums, hard palate and tongue - mechanoreceptors - inhibition of jaw muscles - reduced pressure - contraction…
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
64
Q

Saliva is secreted by which 3 pairs of glands

A

Parotid
Submandibular
Sublingual

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
65
Q

What is in saliva and what does each component do

A
  1. Water - 99% of secreted fluid. Softens, moistens, dilutes particles. solvent
  2. Mucins - major protein component. Mucins + water = mucus. viscous solution - lubricant function
  3. a - Amylase - catalyses breakdown of polysaccharide (starch, glycogen) into disaccharide (maltose) + glucose
  4. Electrolytes - tonicity / pH
  5. Lysozyme - bactericida - cleaves polysaccharide component of bacterial cell wall
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
66
Q

How is salivary secretion controlled - parasympathetic

A

Cranial nerves VII (facial) and IX (glossopharyngeal)

stimulation - profuse watery salivary secretion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
67
Q

How is salivary secretion controlled - sympathetic

A

Stimulation - small vol, viscous salivary secretion high mucus content (a1 adrenoreceptors)
high amylase content (B2 adrenoreceptors)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
68
Q

How is salivary secretion controlled - Reflex control

A

Presence of food in mouth - chemoreceptors / pressure receptors (wall of mouth/tongue)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
69
Q

What do upper and lower oesophageal sphincters regulate

A

movement of material into and out of oesophagus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
70
Q

Muscularis externa is split into upper and lower - how is it split?

A

Upper 1/3 (superior) = skeletal muscle

Lower 2/3 (inferior) = smooth muscle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
71
Q

Swallowing: 1.Oral phase

A

Voluntary

Bolus pushed to back of mouth by tongue

72
Q

Swallowing: 2.Pharyngeal phase

A

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

73
Q

Swallowing: As bolus approches oesophagus

A

Upper oesophageal sphincter (UOS) relaxes and epiglottis covers opening to larynx (prevents food entering trachea

74
Q

Swallowing: Once food has entered oesophagus

A

UOS contracts ( prevents food reflux)

75
Q

Swallowing : 3. Oesophageal phase

A

Propulsion of bolus to stomach
peristaltic wave sweeps along entire oesophagus
propelled to stomach in 10secs

76
Q

Swallowing: As bolus nears stomach

A

LOS relaxes - bolus enters stomach

77
Q

Receptive relaxation of stomach

A

Vagal reflexes - relaxation of thin, elastic smooth muscle of gastric fundus and body.
Stomach vol - 50ml - 1500ml (no change in pressure)

78
Q

What are the main functions of the stomach

A
  1. Temporary store of ingested material
  2. Dissolve food particles and initiate digestive process
  3. Control delivery of contents to small intestine
  4. Sterilise ingested material
  5. Produce intrinsic factor ( Vit B 12 absorption)
79
Q

Histology of stomach:

What are the 3 layers of muscularis externa

A

Longitudinal (outer)
Circular (middle)
Oblique (inner)

80
Q

What is present in the lumens surface

A

Surface mucus cells - gastric pits - gastric glands - mucus neck, parietal and chief cells

81
Q

Submucosa and mucosa are folded when stomach is empty and what when filled?

A

rugae

stretch as stomach fills

82
Q

What is the function of the fundus of the stomach

83
Q

What are the functions of the body of the stomach

A 
Storage 
Mucus 
HCL
Pepsinogen
Intrinsic factor
84
Q

What is the function of the antrum of the stomach

A

Mixing and Grinding

Gastrin

85
Q

What do mucous neck cells produce

86
Q

What do chief cells produce

A

pepsinogens

87
Q

What do parietal cells produce

A

HCl

intrinsic factor

88
Q

What 3 mechanisms control gastric acid secretion

A

Neurocrine (vagus/local reflexes)
Endocrine (gastrin)
Paracrine (histamine)

89
Q

What are enterogastrones and give examples

A

Hormones released from gland cells in duodenal mucosa

e.g. secretin, cholecystokinin , GIP

90
Q

When are enterogastrones released

A

Released in response to acid, hypertonic solutions, fatty acids or monoglycerides in duodenum

91
Q

What do enterogastrones do

A

Act collectively to prevent further acid build up in duodenum

92
Q

How do enterogastrones prevent acid build up in duodenum

A

Inhibit gastric acid secretion

Reduce gastric emptying (inhibit motility/ contract of pyloric sprinter)

93
Q

What is pepsinogen secreted by

A

Chief cells

94
Q

What produces gastric mucus

A

Surface epithelial cells and mucus neck cells

95
Q

What is the cytoprotective role

A

Protects mucosal surface from mechanical injury.

Neutral pH protects against gastric acid corrosion and pepsin digestion

96
Q

What is the only essential function of the stomach

A

Intrinsic factor

  • produced by parietal cells
  • required for B12 absorption
97
Q

Where is the intrinsic factor/B12 complex absorbed from

98
Q

Where do peristaltic wave travel

A

From body to antrum

99
Q

Describe the body of the stomach in terms of muscle, contraction and mixing

A

Thin Muscle
Weak contraction
No mixing

100
Q

Describe the antrum of the stomach in terms of muscle, contraction and mixing

A

Thick muscle
Powerful contraction
Mixing

101
Q

What happens when the pyloric sphincter contracts

A
  • Only small quantity of gastric content (chyme) entering duodenum
  • further mixing as antral contents forced back towards body
102
Q

What produces gastric peristaltic waves

A
  1. peristaltic rhythm - generated by pacemaker cells (longitudinal muscle layer)
  2. Slow waves - spontaneous depolarisation/repolarisation
103
Q

Describe slow wave rhythm

A

Basic electrical rhythm (BER)

Slow waves conducted through gap junctions along longitudinal muscle layer.

104
Q

Describe depolarisation and AP of slow waves

A

Slow wave depolarisation sub-threshold - require further depolarisation to induce AP = contraction
Number of APs/waves determines strength of contraction

105
Q

What happens to motility under neural/hormonal control

A

Gastrin = increases contraction
Distension of stomach wall - long/short reflexes - increased contraction
Fat/acid/amino acid/ hypertonicity in duodenum - inhibition of motility

106
Q

What is responsible for neutralisation of Acid in duodenum

A

Bicarbonate (HCO3) secretion from brunner’s gland duct cells (submucosal glands)

107
Q

What does acid in the duodenum trigger

A
  1. Long (vagal) and short (ENS) reflexes. HCO3 secretion
  2. Release of secretin from S cells. HCO3 secretion
    - secretin HCO3 secretion from pancreas and liver
    - Acid neutralisation - inhibits secretin in release (negative feedback control)
108
Q

What are the 3 parts of the pancreas.

A

Head (located within curvature of duodenum)
Body
Tail (extends to the spleen)

109
Q

Histology of endocrine portion of pancreas

A

Pancreatic islets ( islets of langerhans)

110
Q

What do islet cells produce

A

Insulin

Glucagon (control [glucose]blood) and somatostatin ( controls secretion of insulin and glucagon)

111
Q

Histology of exocrine portion of pancreas

A

Acing cells and lobules

112
Q

What is the anatomical structure of exocrine part of pancreas

A

Acini - Ducts - Pancreatic Duct

113
Q

What is the function of the exocrine part of pancreas

A

Secretion of bicarbonate by duct cells

Secretion of digestive enzymes by acinar cells

114
Q

Acinar cells contain digestive enzymes stored as what and what does this prevent

A

Inactive zymogen granules

Prevents auto digestion of pancreas

115
Q

What does enterokinase do

A

Converts trypsinogen to trypsin

116
Q

What does Trypsin do

A

Converts all other zymogens to active form

117
Q

What do proteases do

A

Cleave peptide bonds

118
Q

What do nucleases do

A

Hydrolyse DNA/RNA

119
Q

What do elastases do

A

Collagen digestion

120
Q

What do phospholipases do

A

Phospholipids to fatty acids

121
Q

What do lipases do

A

Triglycerides to fatty acids + glycerol

122
Q

What does a- amylase do

A

Starch to maltose + glucose

123
Q

Bicarbonate secretion is stimulated by what

124
Q

Secretin is released in response to what

A

Acid in the duodenum

125
Q

Zymogen secretion is stimulated by what

A

Cholecystokinin (CCK)

126
Q

CCK is released in response to what

A

Fat/ amino acids in duodenum

- also under neural control - triggered by arrival of organic nutrients in duodenum

127
Q

What is in the portal traid of the liver

A

Hepatic portal vein
Hepatic artery
Hepatic duct

128
Q

What are hepatic cords composed of

A

Hepatocytes = functional cells of liver

129
Q

What are the spaces between hepatic cords called

A

hepatic sinusoids

130
Q

What lies between cells within each cord

A

Bile Canaliculus

131
Q

What is the alimentary role of the liver

A

Production and secretion of bile

132
Q

What are the 6 components of bile

A
  1. Bile acids
  2. Lecithin ( all these 3 synthesised in liver. solubilise fat)
  3. cholesterol
  4. Bile pigments ( bilirubin)
  5. Toxic metals ( Detoxified in liver)
  6. Bicarbonate (neutralisation of acid chyme)
133
Q

What are the components of bile secreted by

A

1-5 secreted by hepatocytes (liver cells)

HCO3 secreted by duct cells

134
Q

What do bile pigments do

A

Breakdown products of haemoglobin from old/damaged erythrocytes

135
Q

Where is bilirubin (predominant bile pigment) extracted from and what is it secreted into

A

Blood by hepatocytes and secreted into bile

Yellow bile

136
Q

What is the result of bilirubin modified by bacterial enzymes

A

Brown pigments

Brown faeces

137
Q

What does reabsorbed bilirubin excreted in urine cause

A

Yellow urine

138
Q

Where are bile acids synthesised

A

In liver from cholesterol

139
Q

What do bile acids do before secretion

A

Bile acids conjugated with glycine or taurine - bile salts

increase solubility

140
Q

Secreted bile salts is recycled via what

A

enterohepatic circulation

141
Q

Where does the gall bladder lie

A

On inferior surface of liver

142
Q

What are the 3 layers in the wall of the gallbladder

A
  1. Mucosa (folded - rugae - expansion)
  2. Muscularis (smooth muscle) - contraction
  3. Serosa (connective tissue)
    * Gallbladder - cystic duct - common bile duct
143
Q

How does the sphincter of Oddi help in control of bile secretion

A

Controls release of bile and pancreatic juice into duodenum.
When contracted (closed) - bile forced back into gallbladder
Gallbladder concentrates bile 5-20 times (absorbs Na+ & H2O)
Fat in duodenum - release of CCK
- CCK - (A) sphincter of odds relaxes
- (B) Gallbladder contracts

Discharge of bile into duodenum - fat solubilisation
CCK - Pancreatic enzyme secretion
- Bile secretion

144
Q

What are the 3 parts of the small intestine and what do they do

A
  1. duodenum - gastric acid neutralisation; digestion; iron absorption
  2. Jejunum - Nutrient absorption - 95%
  3. Ileum - NaCl/H20 absorption - chyme dehydration

The absorptive surface area enhanced by folds, villi, microvilli

145
Q

Intestinal Absorption and secretin: What do villi absorb

A 
NaCl
monosaccharides 
amino acids 
peptides
fats
vitamins 
minerals 
Water
146
Q

What do Crypts secrete

A

Secretes Cl and Water

147
Q

Intestinal fluid secretion: How much water is secreted per day by the small intestine

148
Q

How is water secreted

A

Secretion comes from epithelial cells lining crypts of Lieberkuhn.
Water secreted passively as a consequence of active secretion of chloride into intestinal lumen.
Normally water secreted by crypts reabsorbed by villi

149
Q

Water secretion important for which normal digestive processes

A

A - Maintains lumens contents in liquid state
B - Promotes mixing of nutrients with digestive enzymes
C - Acids nutrient presentation to absorbing surface
D - Dilutes and washes away potentially injurious substances

150
Q

Intestinal motility:

What are the two distinct types of movement

A

Segmentation

Peristalsis

151
Q

Describe segmentation:

A
  1. Most common during meal
  2. contraction relaxation of short intestinal segments
    - Contraction (few seconds) moves chyme (up and down) into adjacent area of relaxation
  3. relaxed areas then contract and push chyme back
    - Provides through mixing of contents with digestive enzymes
    - bring chyme into contact with absorbing surface
152
Q

How is the generation of segmentation contractions initiated

A

By depolarisation generated by pacemaker cells in longitudinal muscle layer

153
Q

What determines the frequency of the segmentation

A

The basic electrical rhythm

BER decreases as move down intestine - rectum

154
Q

What effect does the parasympathetic NS have on contraction

A

Increases contraction

155
Q

What effect does the sympathetic NS have on contraction

A

Decreases contraction

156
Q

Describe peristalsis

A

Migrating motility complex (MMC)

  • Pattern of peristaltic activity travelling down small intestine (starts in gastric antrum)
  • As on MMC ends (terminal ileum) another begins
  • Arrival of food in stomach - cessation of MMC and initiation of segmentation
157
Q

What does Migrating motility Complex do

A

Move undigested material into large intestine

Limit bacterial colonisation of small intestine.

158
Q

What is the hormone involved in initiating MMC

159
Q

What is the law of the intestine

A

If intestinal smooth muscle is distended
Muscle on oral side of bolus contracts - muscle on anal side of bolus relaxes - Bolus is moved into area of relaxation towards colon.
Mediated by neurones in myenteric plexus

160
Q

What is the gastroileal reflex

A

Gastric emptying - increases segmentation activity in ileum.

  • opening of ileocaecal valve (sphincter)
  • entry of chyme into large intestine
  • distension of colon
  • reflex contraction of ileocaecal sphincter (prevents back flux into small intestine)
161
Q

What are the 4 parts of the large intestine

A

Ascending, transverse, descending and sigmoid

162
Q

What do large, straight crypts lined with and what do they do

A

Lined with large number of goblet cells

They are there for lubrication for movement of faeces

163
Q

Where is the rectum located

A

Straight, muscular tube - between end of sigmoid colon and anal canal

164
Q

What is the muscularis externa like in the rectum

A

Thick compared to other regions of alimentary canal

165
Q

Where is the anal canal

A

2-3 cm between distal rectum and anus

166
Q

Describe the 1. Muscularis

2. Sphincter and 3. Epithelium of the anal canal

A
  1. Muscularis thicker than rectum - internal anal sphincter
  2. External anal sphincter = skeletal muscle
  3. Epithelium: simple columnar - stratified squamous
167
Q

What happens in the colon

A

Actively transports sodium from lumen into blood - osmotic absorption of water - dehydration of chyme - solid faecal pellets

168
Q

Defaecation following a meal

A

Wave of intense contraction (Mass movement contraction) - colon –> rectum.
Distension of rectal wall produced by mass movement of faecal material into rectum –> mechanoreceptors –> defaecation reflex –> urge to defaecate

169
Q

What is the Defaecation Reflex

A

Under parasympathetic control - via pelvic splanchnic nerves

  1. Contraction of rectum
  2. Relaxation of internal and contraction of external anal sphincters
  3. Increased peristaltic activity in colon
    - increases pressure on external anal sphincter - relaxes under voluntary control = expulsion of faeces
170
Q

What causes constipation

A

No absorption of toxins from faecal material following long periods of retention.

171
Q

What are some symptoms associated with constipation

A

Headaches
Nausea
Loss of appetite
Abdominal distension

172
Q

What is diarrhoea

A

Too frequent passage of faeces which are too liquid

173
Q

What are the causes of diarrhoea

A 
Pathogenic bacteria 
Protozoans
viruses 
toxins
food
174
Q

What do enterotoxigenic bacteria do

A

Produce protein enterotoxins which maximally turn on intestinal chloride secretion from crypt cells.
Increases water secretion
- Elevate intracellular second messengers

175
Q

How do you treat secretory diarrhoea

A

Give sodium/glucose solution

  • drive water absorption - rehydration
  • secretion still going –> wash away infection
  • Oral rehydration therapy
176
Q

What does secreting help regulate and how?

A

pH of duodenum by:

1) inhibiting secretion of gastric acid from parietal cells.
2) stimulating production of bicarbonate from ductal cells of the pancreas

2nd Year (27 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions