Physiology Flashcards
(175 cards)
1
Q
What are the four functions of the digestive system?
A
Digestion
Secretion
Absorption
Motility
2
Q
Name the three pairs of salivary glands?
A
Parotid Glands
Salivary Glands
Submandibular Glands
3
Q
List some functions of the stomach
A
Sterilises food,
Digests protein,
Temporary store of food.
4
Q
Function of the liver in the gastrointestinal system
A
Production of bile salts for digestion/absorption of fats in small intestine
5
Q
Function of the gallbladder
A
Stores and concentrates bile
6
Q
Functions of the pancreas
A
Digestive enzymes for digestion of fats, carbohydrates and proteins
7
Q
Function of small intestine
A
Final stages of chemical digestion and nutrient absorption
8
Q
Functions of large intestine
A
Water absorption, bacterial fermentation and formation of faeces
9
Q
Name the four basic layers of the gut wall
A
Mucosa (epithelium, lamina propria, muscularis mucosae)
Submucosa,
Muscularis externa
Serosa/adventitia
10
Q
Which parts of the gut tube have glands in the submucosa?
A
Oesophagus and duodenum
11
Q
What kind of epithelium makes up the mouth, the oesophagus and the anal canal?
A
Stratified squamous
12
Q
What kind of epithelium makes up the stomach, small and large intestine?
A
Simple columnar epithelium
13
Q
What are the two layers of muscularis externa in the gut tube?
A
Inner layer of circular muscle,
Outer layer of longitudinal muscle
14
Q
Where is the myenteric plexus located?
A
The myenteric plexus lies between the two layers of muscularis externa
15
Q
Where is the submucosal plexus located?
A
Outside the submucosa
16
Q
What is the autonomic reflex control of the alimentary tract?
A
Long (parasympathetic) and short (ENS reflexes)
17
Q
What does the parasympathetic nervous system do to the GI tract?
A
Simulates secretion and motility via the vagus nerve.
18
Q
What stimulates salivation?
A
The facial (VII) and glossopharyngeal (IX) cranial nerves
19
Q
What does the sympathetic nervous system do to the GI tract?
A
Inhibits secretion and motility via the splanchnic nerve
20
Q
What parts of the GI tract does the celiac trunk supply?
A
Stomach,
Small intestine,
Pancreas
LIver
21
Q
What parts of the GI tract does the superior mesenteric artery supply?
A
Small intestine,
Caecum,
Ascending Colon,
Transverse Colon
22
Q
What parts of the GI tract does the inferior mesenteric artery supply?
A
Descending Colon
Sigmoid Colon
Rectum
23
Q
What parts of the GI tract does the superior mesenteric vein drain?
A
Small Intestine,
Caecum,
Ascending Colon,
Transverse Colon.
24
Q
What parts of the GI tract does the inferior mesenteric vein drain?
A
Descending Colon,
Sigmoid Colon,
Rectum
25
What does the hepatic portal vein drain?
Superior mesenteric vein + Splenic vein
26
What does the hepatic portal vein drain into?
Hepatic vein, which then drains into the inferior vena cava.
27
What two sugars make up lactose?
Glucose and Galactose
28
What two sugars make up sucrose?
Glucose and Fructose
29
What two sugars make up maltose?
Glucose and Glucose
30
What enzyme breaks down alpha 1,4 glycosidic bonds
Alpha-amylase
31
How is glucose/galactose transported across the apical border?
Through the SGLT1 glucose symporter (Along with sodium).
32
How is glucose/galactose transported across the basolateral membrane?
Through the GLUT-2 transporter (down its concentration gradient)
33
How is fructose transported across the apical membrane?
Through the GLUT-5 transporter
34
What enzymes digest proteins to amino acids?
Proteases/Peptidases
35
What does the PepT1 transporter transport?
It is an symporter that transports di/tripeptides in along with Hydrogen ions (created by the acid microclimate)
36
In what form is most fat ingested?
Triacylglycerol
37
What enzyme breaks down fat in the small intestine?
Pancreatic Lipase
38
Why can lipase only act on the surface of fat?
Lipase is water soluble - cant pass through the fat molecule
39
What forms the mechanical disruption component of emulsification?
Smooth muscle contraction grinding and mixing luminal contents
40
What forms the emulsifying agent?
Bile salts and phospholipids
41
How is absorption of fat across the enterocytes enhanced?
Formation of micelles
42
How are fatty acids transported across the apical mebrane?
Micelles are broken down into free fatty acids and monoglycerides by the acid microclimate and movement in the lumen.
43
What happens to fatty acids and monglycerides upon entering enterocytes?
Enter Smooth endoplasmic reticulum - where they are reformed into triacyleglycerides and coated with an amphiteric protein
44
What are the fat droplets released as into the lacteals?
Chylomicrons
45
What are the fat-soluble vitamins
Vitamins A, D, E, K.
46
What does vitamin b12 bind to?
Intrinsic factor
47
What does B12 defiency lead to?
Pernicious anaemia
48
Where is Vitamin B 12 stored?
In the liver
49
How is iron transported across the apical membrane?
Iron is transported via DMT1
50
How is iron stored intracellularly?
As ferritin - expression is related to iron levels (More ferritin in high iron levels)
51
How is iron in blood transported?
As transferrin
52
How is chewing controlled?
Voluntary innervation - to skeletal muscles of the mouth/jaw
Reflexes - via mechanoreceptors
53
What makes up saliva?
Water, Mucins, Alpha-amylase, Electrolytes, Lysozymes
54
How is salivary secretion controlled?
Via both parasympathetic (Cranial nerves 7 and 10 - watery secretion), and sympathetic control (viscous secretion) - both stimulatory.
Also reflex control via chemi/pressure receptors
55
What kind of muscle makes up the muscularis externa of the oesophagus?
Upper 1/3 is skeletal muscle, Lower 2/3 is smooth muscle.
56
What stomach cells produce pepsinogens?
Chief cells
57
What stomach cells produce HCl?
Parietal cells
58
What stomach cells produce Intrinsic factor?
Parietal cells
59
What stomach cells produce mucus?
Mucous neck cells
60
What signalling mechanism does gastrin use in parietal cells?
PKC (Acts via calcium) - stimulates HCl
61
What signalling mechanism does ACh use in parietal cells?
PKC (Acts via calcium) - stimulates HCl
62
What signalling mechanism does Histamine use in parietal cells?
PKA (Acts via cAMP) - stimulates HCl
63
What signalling mechanism do Prostaglandins use in parietal cells?
PKA (Acts via cAMP) - inhibits HCl
64
What are the three mechanisms by which gastric acid secretion is controlled?
Neurocrine (vagus/local reflexes)
Endocrine (gastrin)
Paracrine (histamine)
65
What stimulus in the 'head phase' of acid secretion stimulates the vagus nerve?
Sight, smell or taste of food.
66
What stimulates gastrin production from G cells?
The vagus nerve, along with peptides in the lumen.
67
What stomach cells produce histamine?
ECL cells
| enterochromaffin-like
68
What stimulates histamine release from ECL cells?
Gastrin/Ach from vagal stimulation
69
What stimulus in the 'head phase' of acid secretion inhibits the vagus nerve?
Stopping eating
70
What stimulus in the 'gastric phase' of acid secretion inhibits acid secretion?
Decrease in pH - leading to reduced gastrin production (So that stomach maintains pH)
71
What does acid in the duodenum do to gastric acid secretion?
Reduces gastrin secretion (via secretin and eneterogastric (splanchnic) reflex
72
What does Fat/CHO in the duodenum do to gastric acid secretion?
Decreases it (Via GIP release acting on Gastrin secretion)
73
What converts pepsinogen to pepsin?
Acid hydrolysis (low PH in stomach)
74
What feedback mechanism does pepsin act on pepsinogen?
Positive feedback - stimulating its own production
75
What role does mucus have in the stomach?
Protects mucosal surface from injury
| Protects against gastric acid corrosion and pepsin digestion
76
What is required for vitamin b12 absorption?
Intrinsic Factor
77
What is the difference between serosa and adventitia?
Serosa - inside peritoneal cavity.
| Adventitia - outside peritoneal cavity (oesophagus and rectum)
78
What kind of epithelium line the oesophagus?
Stratified squamous (non-keratinised)
79
What is the function of the upper oesophageal sphincter?
Prevention of food reflux
80
What is the third muscular layer of the stomach?
Oblique layer
81
What is the upper portion of the stomach called?
Fundus (Storage funtion)
82
What is the lower portion of the stomach called?
Antrum (Mixing/Grinding function)
83
What controls entry into the duodenum?
Pyloric Sphincter
84
What name is given to the invaginations of the luminal surface of the stomach?
Gastric pits
85
What type of epithelium makes up the stomach?
Simple Columnar
86
What stimuli in the 'gastric phase' of acid secretion promote acid secretion?
Distension of stomach
Peptides in lumen
Gastrin/ACh - Activate ECL cells to produce histamine
87
What stimulus in the 'intestinal phase' of acid secretion inhibits acid secretion?
Acid in duodenum
| Fat/CHO in duodenum
88
What hormones, produced from duodenal mucosa, act to prevent further acid buildup in duodenum?
Secretin, cholecystokinin (CCK), GIP
89
How do secretin and CCK act to prevent acid buildup in the duodenum?
Inhibit gastric acid secretion
| Inhibit gastric emptying (inhibit motility/contract pyloric sphincter)
90
What is the only essential function of the stomach? (ie not compensated)
Intrinsic Factor
91
Which part of the GI tract absorbs the Intrinsic factor/B12 complex?
Ileum
92
What name is given to gastric content entering the duodenum?
Chyme
93
What produces peristaltic waves?
Peristaltic rhythm (produced by pacemaker cells)
Slow waves (spontaneous depol/repolarisation) - Basic Electrical Rhythm
94
What does gastrin do to peristaltic contraction?
Increases it
95
What does fat/acid/amino acid/hypertonicity in the duodenum do to motility?
Inhibits it
96
What substance is secreted from Brunner's gland cells to neutralise acid?
Bicarbonate (HCO3)
97
What controls release of duodenal bicarbonate (HCO3)?
-Long (vagal) and short (ENS)
reflexes
-Secretin release from S cells (also releases HCO3 from pancreas/liver)
98
What feedback mechanism exists for secretin release in the presence of acid neutralisation?
Negative feedback control - secretin release inhibited upon neutralisation
99
What is produced in the endocrine portion of the pancreas?
Insulin, Glucagon and Somatostatin
100
What is produced in the exocrine portion of the pancreas?
Secretion of bicarbonate by duct cells
| Secretion of digestive enzymes by acinar cells
101
What is the name for the common passage of the common bile duct and main pancreatic duct into the duodenum?
Sphincter of Oddi
102
What are digestive enzymes stored as in pancreatic acinar cells?
Inactive zymogen granules (prevents autodigestion)
103
What converts trypsinogen to trypsin?
Enterokinase
104
What is the function of trypsin?
Converts other zymogens to active forms
105
List some categories of pancreatic enzymes
Proteases, Nucleases, Elastases, Phospholipases, Lipases, α-Amylase
106
What stimulates zymogen secretion from the pancreas?
Cholecystokinin (CCK)
| Released in response to fat/amino acids in duodenum
107
What are the four lobes of the liver?
Right, Left, Caudate, Quadrate
108
Where does entry/exit of blood vessels, lymphatic vessels, ducts and nerves happen in the liver?
Porta hepaticus (on inferior surface)
109
What ligament separates the right and left lobes of the liver?
Falciform ligament
110
What ligament attaches the liver to the underside of the diaphragm?
Coronary ligament
111
What is the bare area of the liver?
Where it attaches to the diaphragm
| Elsewhere covered by capsule and visceral peritoneum
112
How do the connective tissue septa divide the liver?
Into hexagonal lobules
113
What makes up the components of the portal triad (located at the corner of each lobule)?
Hepatic portal vein, hepatic artery, hepatic duct.
114
What is the central vein within each lobule?
Hepatic veins
115
What radiates out from the central veins in the liver?
Hepatic cords (made of hepatocytes)
116
What exists within the spaces between hepatic cords?
Hepatic sinusoids (blood channels)
117
How is bile taken from the hepatocytes in the lobules to the hepatic duct?
Through bile canaliculi
118
List functions of hepatocytes
Bile synthesis
Nutrient storage (Glycogen, Fats, Vits, Cu, Fe)
Nutrient interconversion
Detoxification
119
What blood vessel carries O2-depleted, nutrient-rich blood to the liver?
Hepatic Portal Vein
120
What blood vessel carries O2-rich, nutrient-depleted blood to the liver?
Hepatic Artery
121
List components of bile
```
Bile Acids
Lecithin
Cholesterol
Bile pigments (bilirubin)
Toxic Metals
Bicarbonate
```
122
How is bilirubin produced?
Extracted from blood by hepatocytes and secreted into bile (breakdown product of haemoglobin)
123
What happens to bile acids prior to secretion?
Conjugation (w glycine/taurine) - ^ solubility
124
What are the three layers of the gallbladder wall?
Mucosae (Folded rugae)
Muscularis (Smooth muscle)
Serosa
125
What duct leaves the gallbladder to become part of the common bile duct?
Cystic duct
126
What is the function of the sphincter of oddi?
Controls release of bile and pancreatic juice into duodenum
127
What are the functions of the gallbladder?
Stores AND concentrates bile
128
What hormone controls Gallbladder contraction/Bile secretion?
Cholecystokinin (CCK)
129
What hormone controls both sphincter of Oddi relaxation and pancreatic enzyme secretion?
Cholecystokinin (CCK)
130
What is the overall action of secretin?
Neutralisation
131
What is the shortest part of the small intestine?
Duodenum
132
What is the function of the duodenum?
Gastric acid neutralisation, digestion, iron absorption
133
What is the function of the jejunum?
Nutrient absorption (95%)
134
What is the function of the ileum?
NaCl/H20 absorption (chyme dehydration)
135
How is the absorptive surface area enhanced in the small intestine?
Folds, Villi, Microvilli
136
Where do undifferentiated small intestinal cells exist?
Crypts of Leiberkuhn
137
What is the name of the lymph vessel projections in villi?
Lacteal
138
Where is the main area of absorption in a villus?
Top third area
139
Where is the main area of secretion in a villus?
Crypts of Leiberkuhn (secrete water and Cl)
140
What is the primary route for water uptake in the small intestines?
Following sodium-glucose transport.
141
Why is water secretion in the small intestine important?
- Maintains lumenal contents in liquid state
- Promotes mixing of nutrients with digestive enzymes
- Aids nutrient presentation to absorbing surface
- Dilutes and washes away potentially injurious substances
142
How does chlorine get into enterocytes basolaterally?
Through a sodium-potassium-chloride co-transporter
143
How does chlorine leave enterocytes on the apical surface?
Through CFTR (mutated in CF)
144
What are the two types of intestinal movement?
- Segmentation
| - Peristalsis
145
What takes place in segmentation?
Contraction followed by relaxation of short intestinal segments.
146
How is segmentation initiated?
Depolorisation of pacemaker cells in longitudinal muscle
147
What determines strength of contraction in segmentation?
Action potential frequency
148
What determines frequency in segmentation?
Basic Electrical Rhythm (BER)
149
What happens to BER as you move down the intestine?
It decreases (as does strength of contraction).
150
What does parasymp stimulation do to segmentation?
Increases contraction.
151
What does sympathetic stimulation do to segmentation?
Decreases contraction.
152
What is the function of peristalsis?
Clearance of undigested food
| Limit bacterial colonisation of small intestine
153
How is peristalsis controlled?
Migrating Motility Complex (MMC) - initiated by motilin hormone
(Mediated by neurones in myenteric plexus)
154
If an area of intestinal smooth muscle is distended, what happens to the muscle on the oral side of the bolus?
It contracts.
| Protective to avoid obstruction
155
What term refers to reflex ileocaecal sphincter contraction in response to colon distension?
Gastroileal reflex (prevents backflux)
156
What are the four parts of the colon?
Ascending, Transverse, Descending, Sigmoid
157
What name is given to the incomplete bands of longitudinal muscle overlying the colon?
Teniae coli
158
What do the crypts in large intestine have a large number of?
Goblet cells
159
What is the epithelium of the anal canal?
Stratified squamous epithelium
160
Is the internal anal sphincter under smooth or skeletal muscle control?
Smooth muscle
161
Is the external anal sphincter under smooth or skeletal muscle control?
Skeletal muscle (Voluntary control)
162
What is the function of the colon?
Osmotic absorption of water (through active transport of sodium)
(No important role in nutrient absorption)
163
What causes the defaecation reflex?
Distension of the rectal wall activating mechanoreceptors.
| Process under parasympathetic control
164
How is voluntary delay of defaecation achieved?
Descending neural pathways.
165
List some enterotoxigenic bacteria?
Vibrio cholerae, E.Coli
166
What is the pathogenesis of enterotoxigenic bacteria?
Maximally turn on chloride secretion -> ^^H20 secretion
167
What is used to treat diarrhoea?
Sodium/Glucose solution
| Oral rehydration therapy
168
In what ways does the small intestine maintain a barrier against pathogens?
- Immune sampling
- Monitoring presence of pathogens
- Translocation of bacteria
- Gut Associated Lymphoid Tissue (GALT)
169
What pancreatic enzyme is used to breakdown fat?
Pancreatic lipase
170
What pancreatic enzyme is used to breakdown carbohydrates?
Pancreatic amylase
171
What are the neuronal components that trigger nausea and vomiting?
Sympathetic and Vagal Components
Vomiting Centre
Chemoreceptor Trigger Zone (CTZ)
172
What are the functions of the liver?
Clotting factors
Bile acids
Carbohydrates -(Gluconeogenesis, Glycogenolysis, Glycogenesis)
Proteins -(Albumin synthesis)
Lipids - (Cholesterol synthesis, Lipoprotein and TG synthesis)
Hormones -(Angiotensinogen, insulin like growth factor)
173
What is the detoxification function of the liver?
Urea production from ammonia
Detoxification of drugs
Bilirubin metabolism
Breakdown of insulin and hormones
174
What is the contribution of the liver to immune function?
Combating infections
Clearing the blood of particles and infections, including bacteria
Neutralizing and destroying all drugs and toxins
175
What is included in the storage function of the liver?
Stores glycogen
Stores Vitamin A, D, B12 and K
Stores copper and iron
