GI Flashcards
1
Q
What are the 3 components of the pharynx
A
Nasopharynx
Oropharynx
Laryngopharynx
2
Q
What nerve stimulates the nasopharynx
A
Maxillary branch of the trigeminal nerve
3
Q
What nerve stimulates the oropharynx
A
Glossopharyngeal
4
Q
What nerve stimulates the laryngopharynx
A
Vagus
5
Q
What are the three stages of swallowing
A
Voluntary
Involuntary
Involuntary
6
Q
What happens in the first voluntary stage of swallowing?
A
Food Is compressed against the roof of the mouth and pushed towards the oropharynx by the tongue
Buccinator and supra hyoid muscles manipulate food during chewing, lift the hyoid bone and flatten the floor of the mouth
7
Q
What happens in the secondary involuntary stage of swallowing?
A
- Nasopharynx is closed off by the muscles of the soft palate which tense and elevate - forms food bolus
- Pharynx is shortened and widened by contraction of the longitudinal muscle
- Impulses from the swallowing centre inhibit respiration, raise the larynx and close the glottis to stop food entering the trachea
- As the tongue pushes food further back into the pharynx, the epiglottis folds over the closed glottis to prevent food aspiration
8
Q
What happens in the third involuntary stage of swallowing>
A
Sequential contraction of the pharyngeal constrictor muscles which depresses the pharynx and the hyoid bone. Before food enters the oesophagus, the Upper oesophageal sphincter relaxes then as soon as food passes through it closes, the glottis opens and breathing resumes. Once the food is in the oesophagus, peristaltic waves move it
9
Q
Describe the innervation and location of the pharyngeal constrictor muscles
A
Innervated by the vagus nerve, 3 overlying circular muscles that form the posterior and lateral walls and contract sequentially to force food bolus into oesophagus
10
Q
What muscles enables depression of the pharynx and hyoid bone to keep the mouth open?
A
Infra-Hyoid muscle
11
Q
Describe the musculature of the oesophagus
A
Upper 1/3 = skeletal muscle
Lower 2/3 = Smooth muscle
12
Q
Where are the oesophageal sphincters located?
A
Upper OS is a ring of skeletal muscle just below the pharynx
Lower OS is a ring of smooth muscle in last portion of the oesophagus
13
Q
How long does it take for a peristaltic wave to reach the stomach?
A
9 sec
14
Q
Describe the gag reflex and its innervation
A
Reflex elevation of the pharynx often followed by vomiting
Reflex arc of the glossopharyngeal and vagus nerves
15
Q
What are the three main functions of saliva?
A
Lubrication for mastication
Maintain oral pH at 7.4
Digestion - alpha amylase released from the parotid gland
Defence of the oral cavity - washes away food particles which bacteria use as metabolic support
16
Q
What is the daily secretion of saliva in adults>
A
800-1500ml
17
Q
What is the function of serous saliva?
A
Contains alpha amylase for starch digestion
18
Q
What is the function of mucous saliva?
A
Contains mucin components to lubricate mucosal surfaces
19
Q
What sort of gland is the parotid gland?
A
Serous
20
Q
What sort of gland is the submandibular gland
A
Mixed - both serous and mucous (M for Mixed)
21
Q
What sort of gland is the sublingual gland
A
Mucous and serous but mainly mucous
22
Q
What affects the composition and amount of saliva produced?
A
Circadian rhythms Age Time of day Type and duration of the stimulus Diet Drugs Flow rate Type/size of gland
23
Q
What are the defence systems of the oral cavity?
A
Saliva - washes food away
Mucosa - physical barrier
Palatine tonsils - acts as surveillance system for the immune system
24
Q
What sort of gland is the minor salivary glands?
A
all are mucous except the serous glands of von Ebner
25
Which salivary glands are continuously active>
Submandibular, sublingual and minor glands
26
Which salivary gland dominates the unstimulated component of salivary system
Submandibular
27
Which salivary gland dominates the salivary system when stimulated?
Parotid
28
Which epithelium lines the oral cavity
Keratinised stratified squamous epithelium
29
What are the two main components of the salivary gland structure
```
Acinar Cells (Functional unit)
Duct cells (Lined by acinar cells)
```
30
What are the two types of acini>
Mucous and serous
31
Describe the properties of a serous acini
```
Dark stain
Nucleus in the basal 1/3
Small central duct
Secrete alpha amylase and water
Mainly found in parotid gland
```
32
Describe the properties of mucous acini
```
Pale stain
Nucleus at base
Large central duct
Secrete mucins, glycoproteins and water
Mainly found in submandibular and sublingual glands
```
33
What are the 2 components of the interlobular duct of a salivary gland
Intercalated duct and the striated duct
34
Describe the function of the intercalated duct
Short narrow segment of cuboidal cells that connect the acini to the larger striated ducts
35
Describe the function of the striated duct
Major site for NaCl reabsorption and are striated at the basal end
Basal end is highly folded into microvilli to aid the active transport of HCO3 against its concentration gradient
Have mitochondria to provide the necessary energy
36
What is absorbed and what Is secreted by ducts
Na+ and Cl- are REABSORBED and K+ and HCO3- are SECRETED
| Water is also reabsorbed
37
What is the final composition of the saliva like?
Hypotonic
38
What percentage of salivary flow do the major and minor salivary glands contribute respectively
Major = 80%
Minor = 20%
39
Where are the minor salivary glands found?
Lips
Cheeks
Hard and soft palate
Tongue
40
Describe the nerve supply to the parotid gland
Sympathetic inhibitory innvervation from lateral horn of T1 that synapse in superior cervical ganglion an form a plexus around the external carotid artery
Parasympathetic stimulatory innervation from the inferior salivary nucleus in medulla oblongata to the glossopharyngeal nerve which gives the tympanic branch and tympanic plexus with gives the lesser petrosal nerve which synapses at the otic ganglion from which auriculotemporal branch of mandibular division of trigeminal nerve
41
What structures pass through the parotid gland?
Facial nerve and its branches (temporal, zygomatic, buccal, mandibular, cervical)
Retromandibular vein
External carotid artery
42
Describe the structure of the submandibular gland
```
Consists of superficial (Larger) and deep (smaller) lobes that are separated by mylohyoid muscle
Submandibular duct (Whartons duct) begins in the superficial lobe, wraps around the posterior border of mylohyoid and runs in to the floor of the mouth and empties at the sublingual papillae
```
43
Describe the sensory innervation of the submandibular gland
Superior salivary nucleus via the chorda tympani branch of the facial nerve that becomes part of the trigeminal lingual nerve
44
Describe the innervation of the sublingual gland
Parasympathetic by the chorda tympani branch of the facial nerve via the submandibular ganglion
45
What is the effect of parasympathetic innervation of the salivary system
Stimulates secretion
46
What is the effect of the sympathetic stimulation on the salivary system
Inhibits salivary secretion
47
What are the causes of xerostomia (dry mouth)
Cystic fibrosis or Sjorgrens syndrome (autoimmune where immune cells attack glands resulting in no saliva - mainly women)
Medication
irradiation for neck and head cancers
48
Describe where and why salivary glands can become obstructed
Saliva contains calcium and phosphate ions that can form salivary calculi (Stones) - most likely tp form in the submandibular gland where they block the duct at the bend around mylohyoid or at the exit at the sublingual papillae
49
What are the common causes of inflammation of the salivary gland
Infection secondary to obstruction
| Infection caused by mumps
50
Why might salivary glands degenerate
Complication of irradiation from head and neck cancer
| Sjorgens syndrome
51
What are the 8 functions of the stomach
```
Store and mix food
Dissolve food and continue digestion
Regulate emptying into duodenum
Kill microbes
Secrete protease
Secrete intrinsic factor
Lubrication
Mucosal protection
```
52
What do mucous cells produce
Mucous
53
What do parietal cells produce?
Gastric acid and intrinsic factor
54
What do chief cells produce?
Pepsinogen
55
What do ECL cells produce?
Histamine
56
What do G cells produce?
Gastrin
57
What do D cells produce?
Somatostatin
58
What is the pH of stomach acid and how much is produced a day?
HCL pH 2 (H+) >150mM
| Approx 2L produced per day
59
Describe the difference sin the epithelium between the upper and Lower portions of the stomach
epithelium of stomach invaginate into mucosa
Body of stomach is thinned wall and is concerned with secretion of mucus, HCL and pepsinogen
Antrum of stomach is thicker layer of smooth muscle and is for mixing contents of stomach - glands here secrete little acid but secreted gastrin hormone instead
60
Outline how parietal cells secrete H+
1. H20 in parietal cells breaks down into H+ and OH-
2. Co2 and H20 from respiration are converted into H2CO3 by carbonic anhydrase but rapidly dissociates into HCO3- and H+
3. HCO3 is pumped out into capillaries in exchange for CL-
4. H+ produced can react with the OH- from H20 breakdown to reform H2O or can be pumped into the stomach lumen via the H+/K+ ATPase
5. K+ diffused back into the stomach via K+ channels and Cl- ions enter stomach through Cl- channels
6. In the stomach, H+ and Cl- ions combine to form HCl
61
What is the effect of increased acid stimulation?
Increased migration and insertion of H+/K+ ATPase channels in the membrane increasing the amount of H+ pumped into the stomach lumen
62
Describe how the cephalic phase increases gastric acid secretion
Triggered by the smell, sight or taste of food
Parasympathetic NS
Ahh acts indirectly on parietal cells
ACh triggers the release of gastrin from G-cells and histamine from ECL cells
These increase insertion of H+/K+ ATPase in plasma membrane of parietal cells
63
Describe how the gastric phase increases gastric acid secretion
Triggered by gastric distension and the presence of peptides and AA in the stomach
Causes gastrin to be released which acts directly on parietal cells
Causes Histamine to be released from ECL cells which acts directly on parietal cells
Causes increase K+/H+ ATPase insertion on the plasma membrane
64
Why is histamine a good therapeutic target in stomach acid production?
Because it acts directly on parietal cells but also mediates the effects of gastrin and acetylcholine
65
What is the effect of protein in the stomach?
Direct stimulus from gastrin release
Protein in the lumen acts as a buffer, mopping up H+ which causes the stomach pH to rise. Somatostatin secretion is subsequently inhibited and parietal cell activity increases
66
What two phases result in decreased stomach acid production
Gastric phase
| Intestinal Phase
67
Describe the gastric phase in the decrease of stomach acid
Low luminal pH causes inhibition of gastrin secretion and indirect inhibition of histamine secretion
Low luminal pH stimulates the release of somatostatin which inhibits parietal cells
68
Describe the role of the intestinal phase in reducing stomach acid secretion
Occurs in the duodenum
Initiated by duodenal distension, low pH, hypertonic solutions and fatty acids and amino acids
Causes the release of enterogastrones including
1. Secretin --> Inhibits gastrin and promotes somatostatin
2. CCK
also triggers long and short neural pathways to reduce ACh
69
What is a peptic ulcer?
breach in the mucosal surface
70
What are the causes of peptic ulcer
Helicobacter pylori
Drugs (NSAIDs)
Chemical Irritants (Alcohol+bile salts)
Gastrinoma
71
How does helicobacter pylori damage the mucosa?
Lives in the gastric mucosa
Secretes urase which splits urea into CO2 and ammonia
Ammonia combines with H+ to form ammonium
Ammonium is toxic to the gastric mucosa and reduces mucus secretion
Ammonium secreted proteases, phospholipase and vacuolated cytotoxin A damage gastric epithelium
Causes reduced mucosal defence
72
How do NSAIDs damage the gastric mucosa?
Mucus production is stimulated by prostaglandins but requires COX-1 for production
NSAIDs inhibit COX-1
Use prostaglandin analogues instead
73
How do chemical irritants such as alcohol and bile salts damage the mucosa?
Wash away the protective mucus lining
Bile salts reflux into the stomach by the duodenal-gastric reflux
Regurgitated bile strips away the mucus layer
74
What is a gastrinoma?
tumour of the parietal cells that causes increases gastrin release which causes increased gastric acid release which attacks the gastric mucosa causing an ulcer
75
What are the 4 ways that the gastric mucosa defends itself?
Alkaline mucus
Tight junctions between epithelial cells
Replacement of damaged cells
Feedback loops
76
Name 3 ways to reduce gastric acid secretion
1. Proton pump inhibitors such as omeprazole block the pump that pumps H+ into the lumen but not the factors that stimulate it
2. H2 receptor antagonists such as cimetidine block histamine receptors reducing secretion
3. Prostaglandin analogues such as misoprostol
77
Describe the process of protease secretion
The zymogen pepsinogen is released from chief cells under influence of ACh release from the enteric nervous system. once in the stomach lumen, the low luminal pH causes autocatalytic conversion into pepsin. Once pepsin is released it causes positive feedback for release of more,.
78
How is pepsin inactivated?
HCO3- released in the duodenum irreversibly inactivates pepsin
79
What is the role of pepsin?
Not required as protein digestion still occurs if stomach removed but accelerates process by breaking collagen so forms chunks with larger SA
Accounts for 20% of protein digestion
80
What is the normal volume of the stomach and what is the volume after eating? why does it increase?
50ml normally
1.5L when eating
Increases without increase in intraluminal pressure as smooth muscle in fundus and body relax
81
How does receptive relaxation of stomach smooth muscle occur?
Receptive relaxation is mediated by the enteric NS which releases NO and serotonin and by the parasympathetic NS via the vagus nerve
82
Describe the process of gastric motility
1. Waves in the body of the stomach are too weak for proper mixing
2. Waves in the antrum are more powerful = mixing
3. Pyloric sphincter closes when peristaltic wave arrives but small amount of chyme passes through into duodenum
4. Closing of PS forces antral contents back into body for more mixing and digestion
83
Describe which cells determine the rate of peristaltic waves in the stomach
Interstitial pacemaker cells of Cajal in the muscularis propria give off constant waves (3/minute)
Cells undergo cycles of depolarisation and repolarisation with depolarisation travelling through gap junctions to adjacent smooth muscle
84
What factors increase the strength of peristaltic contractions in the stomach?
Presence of gastrin
| Gastric distension mediated by mechanoreceptors
85
What factors decrease the strength of peristaltic contractions in the stomach?
```
Duodenal distension
Increased duodenal fat content
Increased duodenal osmolarity
Decreased duodenal pH
Increased sympathetic stimulation
Decreased parasympathetic stimulation
```
86
What is the main cause of dumping syndrome?
Volume of stomach is greater than the duodenum so if duodenum becomes overfilled with hypertonic solution, dumping occurs
87
What are the 8 symptoms of dumping syndrome?
Bloating, vomiting, diarrhoea,
| Cramping, weakness, dizziness, sweating, fatigue
88
What is gastropariesis?
Delayed gastric emptying
89
What are the 8 causes of gastropariesis?
Idiopathic, autonomic neuropathies, abdominal surgery, PD, MS, scleroderma and amyloidosis
90
What are the 5 common symptoms of gastropariesis?
Abdominal pain/bloating, vomiting undigested food, nausea and early satiety and GORD
91
What 7 drugs are associated with causing gastropariesis?
```
H2 receptor antagonists
Proton pump inhibitors
Opioid analgesics
Diphenhydramine
B-adrenergic receptor agonists
Ca2+ channel blockers
Levodopa
```
92
What are the 6 routes of fluid intake into the GIT and how much water do we get from each?
```
Ingest = 2L
Saliva = 1.5L
Gastric Secretions = 2L
Pancreatic Juice = 1.5L
Bile = 0.5L
Intestinal secretion = 1.5L
TOTAL = 9L IN
```
93
What are the 3 routes of fluid loss from the GIT and how much water is lost at each?
Small intestine absorbs 7.5L
Colon absorbs <1.5L
Excreted <200ml
94
What is the most abundant substance in chyme?
Water
95
Which part of the small intestine absorbs the most water?
Jejunum
96
Why doesn't the stomach absorb water?
Doesn't have a large enough surface area and lacks solute absorbing mechanisms to create the osmotic gradient for absorbing water
97
What is the most abundant solute in chyme?
Na+
98
In which parts of the small intestine is Na+ actively transported?
Ileum and jejunum
99
Describe and draw a diagram for the process of Na+ reabsorption in the small intestine
Occurs by a TRANSCELLULAR ROUTE
1. Glucose and 2Na+ are absorbed from the intestinal lumen into epithelial cell by the Na+/glucose symporter
2. Glucose passes into the blood across the basolateral membrane of epithelial cell by GLUT2
3. Na+ crosses into blood via Na+/K+ ATPase
100
Describe and draw a diagram for the process of Na+ reabsorption in the small intestine
Occurs by a TRANSCELLULAR ROUTE
1. Glucose and 2Na+ are absorbed from the intestinal lumen into epithelial cell by the Na+/glucose symporter (SGLT1)
2. Glucose passes into the blood across the basolateral membrane of epithelial cell by GLUT2
3. Na+ crosses into blood via Na+/K+ ATPase
101
Describe and draw a diagram for the process of intestinal excretion
K+/Na+/2Cl- cotransporter moves Cl- into epithelial cells which increases cAMP which increases the secretion of Cl- into the intestinal lumen. Increasing Ca2+ levels in the cell as a result of IP3 action also increases Cl- secretion. Water follows down an osmotic gradient via a paracellular route
102
Describe the absorption of Na+/K+ and Cl- in the colon
Colon Is iso-osmotic with the blood so Na+ actively absorbed from lumen and water follows
K+ absorbed by passive diffusion due to concentration gradient
Cl- reabsorbed in exchange for bicarbonate causing intestinal contents to become more alkaline
103
How does the cholera toxin increase intestinal secretion?
Binds to intestinal cells and stimulates adenylate cyclase to produce more cAMP which causes a dramatic efflux of CL- ions which is followed by water resulting in a watery diarrhoea
104
Name the 2 functional states the body undergoes for providing the energy for cellular activities
Absorptive
| Post absorptive
105
Define the absorptive state
ingested nutrients enter the blood from the GIT. Some ingested provided energy and some are added to the bodies energy store
106
Define the post-absorptive state
GIT is empty and bodies own stores supply the energy
107
What are the three main fatty acids we absorb?
Palmitic, stearic and oleic
108
Describe the structure of a triglyceride
A glycerol molecule with three fatty acid molecules attache d
109
Where does triglyceride digestion predominantly occur?
mainly in the small intestine but small amount in the mouth and the stomach
110
Describe the action of lipase on fats
Lipase cleaves the 1 and 3 carbon bonds producing a monoglyceride and two fatty acids
111
Describe the process of fat emulsification
1. Lipids are water insoluble so aggregate into larger droplets in the upper stomach
2. These are converted into smaller droplets in a 2 stage emulsification process
3. Mechanical disruption occurs due to the motility of the GIT in lower stomach and intestine causing mixing
4. Emulsification by two emulsification agents, phospholipids from food and bile salts made from cholesterol in the liver
112
How to phospholipids and bile salts emulsify fat?
```
Phospholipids are amphiphatic molecules containing two non polar fatty acids, glycerol and a phosphate group
Bile salts (cholic) from liver are also amphiphatic
Non polar (hydrophobic) portion of phospholipids and bile salts aggregates with the non polar interior portion of lipid droplet leaving the outer polar portion exposed which prevents the reaggregation of smaller droplets into larger ones
Outer, hydrophilic regions help to draw the fat droplet into the intestinal chyme to allow pancreatic lipase to act
```
113
The emulsification process impairs the action of lipase, how is this overcome?
Pancreas produces co-lipase that holds pancreatic lipase in place on the lipid droplets allowing breakdown to occur into FFA and monoglycerides
114
What is the average daily intake of lipid
70-100g
115
Other than emulsification, what also happens in the absorption of fat?
Micelles form which contain bile salts, fatty acids, phospholipids and fat soluble vitamins (A, D, E, K). Micelles are in equilibrium with free products of fat digestion this micelles are constantly breaking down and reforming.. When a micelle breaks down its contents become available to diffuse across intestinal lining. As the concentration of free lipids fall, because of diffusion, micelles break down to release more lipid
116
Describe the process of fat absorption at the small intestine
1. Micelles break down into fatty acids and monoglycerides which are absorbed into epithelial cells
2. These are reformed into triglycerides in the smooth endoplasmic reticulum
3. This decreases the cytosolic concentration of fatty acids and monoglycerides creating a concentration gradient for their entry into epithelial cells
4. Small fat droplets reform in the rough ER and are carried in vesicles to the Golgi apparatus where they are converted to chylomicrons which are released by exocytosis
5. Chylomicrons contain triglycerides, cholesterol, and fat soluble vitamins
6. Chylomicrons are absorbed into the lacteals and are carried into the lymphatic system before draining into the thoracic duct
7. Lipoprotein lipase breaks off triglycerides into FFA and monoglycerides which enter the adipose and skeletal muscle
8. Remaining chylomicron goes to the liver to make VLDL
117
How are the fat soluble vitamins A, D, E and K absorbed?
Are absorbed in the ileum and following the same pathway as fat - are carried in micelles
118
How are the water soluble vitamins except vitamin B12 absorbed?
Diffusion or mediated transport in the jejunum
119
How is water soluble vitamin B12 absorbed?
Large charged vitamin so must bind to intrinsic factor first which is secreted by parietal cells.
When bound to intrinsic factor vitamin B12 binds to specific sites In the lower ileum by endocytosis
120
Why is vitamin B12 required and what does an absence of intrinsic factor lead to?
Erythrocyte formation
| Pernicious anaemia
121
How much protein do we Ingest each day?
40-50g
122
Why do we need to eat protein?
To supply the 8 essential amino acids and to provide nitrogen amino acids used in the urea cycle
123
Describe the digestion of protein
Starts in stomach where pepsinogen from chief cells is converted to pepsin by low pH which cleaves the bond between aromatic amines and second amino acid forming peptide fragments
Digestion also occurs in small intestine by pancreatic enzymes trypsin and chemotrypsin (Endopeptidases)
Fragments are further digested to free AA by carboxypeptidases from the pancreas and amino peptidases on the luminal membrane of intestinal epithelial cells. These enzymes split off amino acids from the carboxy and amino ends respectively
124
What are the two types of pepsinogen and where are they found>
Pepsinogen I found in HCl secreting region (body)
| Pepsinogen II found in pyloric region
125
What is the optimum pH for pepsin action =?
1.6-3.2 so action is terminated on exit from the stomach ie. in the duodenum when pH is 6.5
126
Describe the absorption of proteins
1. Free AA enter the epithelial cells y secondary active transport coupled to sodium
2. there are multiple transporters with different specialties for 20 types of AA
3. Short chains of two or three AA are absorbed by secondary active transport
4. These di/tri peptides are hydrolysed to AA which enter the blood stream via facilitated diffusion carrier in basolateral membrane
127
What is the daily intake of carbohydrate
250-300g
128
Give 3 examples of monosaccharides
Glucose, fructose and galactose
129
Give 3 examples of disaccharides
Sucrose and lactose and maltose
130
Give 2 examples of polysaccharides
Starch and glycogen
131
Describe the structure of glycogen
Glucose polymer containing alpha 1-4 glycosidic bonds and branching alpha 1-6 glycosidic bonds
132
Describe the structure of starch, how is it different from glycogen?
Starch has alpha 1-4 glycosidic bonds and some alpha 1-6 branching chains but less than the amount found in glycogen
133
Describe process of starch digestion in the oral cavity
Ptyalin, the salivary alpha amylase has optimal pH of 6.7 and accounts for small amount of starch digestion. Action is terminated by gastric acidity
134
Describe the process of starch digestion in the small intestine
Accounts for 95% of starch digestion via pancreatic alpha amylase that catalyses alpha 1-4 linkages. Products of both amylases are disaccharides (maltose, sucrose and lactose) which are broken down into monosaccharides glucose, fructose and galactose by enzymes on the brush border of intestinal epithelial cells (Maltase, sucrase and lactase)
135
Describe the process of monosaccharide absorption at the brush border of the small intestine
Hexose and pentose sugars are rapidly absorbed across the intestinal mucosa
Glucose and Na+ use the same transporter (SGLT1) thus a high conc of Na+ at mucosal surface promotes glucose uptake (Gradient in enterocytes generated by Na+/K+ ATPase on basolateral membrane
Fructose uptake is independent of Na+ and occurs by facilitated diffusion through GLUT5
From there, monosaccharides diffuse into the blood through capillary pores and GLUT2 transporters and are carried to the liver
136
What digestive enzymes do salivary glands secrete
Amylase --> Starch
| Lipase --> triglycerides
137
What digestive enzymes do stomach secrete
Pepsin --> protein
| Lipase --> Triglycerides
138
What digestive enzyme does the pancreas secrete
```
Amylase --> Starch
Lipase and collapse --> Triglycerides
Phospholipase --> Phospholipids
Trypsin --> Peptides
Chmyotrypsin --> Peptides
```
139
What digestive enzymes do the intestines secrete
Enterokinase - activates trypsin
| Peptidases - peptides
140
What are the 6 muscles/groups of muscles used in swallowing?
1. Buccinator.
2. Suprahyoids.
3. Muscles of the palate.
4. Muscles of the floor of the mouth.
5. Infrahyoids.
6. Pharyngeal constrictor muscles
141
What are the 4 layers of the GIT wall from innermost to outermost
mucosa
submucosa
Musculares externa
Serosa
142
What are the two divisions of the mucosa
Lamina propria
| Muscularis mucosa
143
What does the muscularis external contain
Circular muscle
Longitudinal muscle
Myenteric plexus
144
What does the muscularis external contain
Circular muscle
Longitudinal muscle
Myenteric plexus
145
What happens to amino acids i
Most enter cells and are used to make protein
Some enter the liver and are de-aminated to form keto-acids - removed amino groups are used to synthesise urea which enters the blood
Ketoacids enter Krebs and provide energy for liver cells
146
What happens to amino acids in the liver?
Some are converted to ammonia then into urea
Some converted to FA
Some converted to CO2, Water and energy
147
What happens to glucose that reaches the adipose tissue>
converted to alpha glycerol phosphate and fatty acids which then combine into triglycerides
148
What happens to glucose in the brain
Converted to Acetyl Coa and goes through Krebs to form ATP
| No storage
149
What happens to glucose in the brain
Converted to Acetyl Coa and goes through Krebs to form ATP
| No storage
150
What is glycogenolysis?
Breakdown of glycogen into glucose-6-phosphate monomers occurring in liver an skeletal muscle via the action of glucagon
151
What is glycogenolysis?
Breakdown of glycogen into glucose via the action of glucagon
152
How is glucose produced following a short fast?
Glycogenolysis
153
What is gluconeogenesis
Production of glucose from non glycogen sources
ie. AA from muscles
Lactate from RBCs
Glycerol from adipocytes
154
what happens to triglycerides produced from glucose in the liver?
Some are stored but most triglycerides are packaged into aggregates with lipids and proteins into lipoproteins (VLDL) and enter the blood
155
Describe the function and location of lipoprotein lipase
Found on the blood facing surface of capillary endothelial cells, especially in adipose cells which breaks down VLDL into monoglycerides and fatty acids
156
Describe the function and location of lipoprotein lipase
Found on the blood facing surface of capillary endothelial cells, especially in adipose cells which breaks down VLDL into monoglycerides and fatty acids
157
What sort of hormone is a insulin and how does it work
Peptide hormone that binds to specific receptors on the plasma membrane of target cells triggering transduction pathways that influence plasma membrane transport proteins
158
What sort of hormone is a insulin and how does it work
Peptide hormone that binds to specific receptors on the plasma membrane of target cells triggering transduction pathways that influence plasma membrane transport proteins
159
What are the effects of increased plasma insulin on muscle?
Increased glucose uptake and utilisation
Net glycogen synthesis
Net AA uptake
Net protein synthesis
160
What are the effects of increased plasma insulin on adipocytes?
Increased glucose uptake and utilisation
| net triglyceride synthesis
161
What are the effects of increased plasma insulin on the liver?
Increased glucose uptake
Net glycogen synthesis
Net triglyceride synthesis
No ketone synthesis
162
What are the effects of decreased plasma insulin on muscle
```
decreased glucose uptake and utilisation
Net glycogen catabolism
net protein catabolism
net AA release
FA uptake and utilisation
```
163
What are the effects of decreased plasma insulin on liver?
Increased glucose release due to glycogen catabolism and gluconeogenesis
Increased ketone synthesis
164
What are the effects of decreased plasma insulin on liver?
Increased glucose release due to glycogen catabolism and gluconeogenesis
Increased ketone synthesis
165
What are the effects of cortisol on fuel metabolism and where is it produced?
```
Produced in the adrenal glands and prepares for stress response
Lipolysis
Protein breakdown
Gluconeogenesis
Glycogen storage
```
166
What disease does long term increase in cortisol cause?
Cushings disease
167
What are the effects of adrenaline on fuel metabolism
Causes flight or fight
Glycogenolysis
Gluconeogenesis
Lipolysis
168
Effects of thyroxine on fuel metabolism
```
Glycolysis
Cholsterol synthesis
Glucose uptake
Protein synthesis
Sensitises tissue to adrenaline
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169
What are the effects of growth hormone on fuel metabolism
Gluconeogenesis
Glycogen synthesis
Lipolysis
Protein synthesis
170
What are the effects of grehlin
Stimulates appetite
171
What are the effects of grehlin
Stimulates appetite
172
What are the functions of the liver?
```
Carbohydrate metabolism
Fat metabolism
Protein metabolism
Hormone metabolism
Toxin/drug metabolism
Storage
Bilirubin and excretion
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173
What protein is responsible for iron storage
Ferritin
174
What are the functions of vitamins
Gene activators
Free-radical scavengers
Co-enzymes/co-cofactors in metabolic reactions
175
Which vitamins are water soluble
B and C
176
Which vitamins are fat soluble
A, D, E and K
177
Where is vitamin A stored
Ito cells and spaces of Disse in the liver
178
What are the functions of vitamin A (Retinoids)
```
Vision
cellular growth and differentiation
Reproduction
Lymphocyte production
Embryological development
Stabilisation of cellular membranes
```
179
What are the sources of vitamin A?
Retinols come from liver, oily fish, dairy and margarine
| Carotenoids come from carrots, spinach, sweet potato and tomatoes
180
What is the function of vitamin B?
Important in cell metabolism & energy production
181
What is the function of vitamin B?
Important in cell metabolism & energy production
182
What are the sources of vitamin B?
Main one is B-12: found in fish, poultry, meat & eggs
183
What disease results from a deficiency of vitamin B
pernicious anaemia - reduced production of RBC
184
What are the functions of vitamin D?
Increased intestinal absorption of calcium
Resorption and formation of bone
Reduced renal excretion of calcium
185
What are the sources of vitamin D?
Vitamin D3 is formed by UV light
| Vitamin D2 comes from plants
186
What are the sources of vitamin D?
Vitamin D3 is formed by UV light
| Vitamin D2 comes from plants
187
What is the main function of vitamin E?
Anti-oxidant
188
What are the main sources of vitamin E?
Oils
Carrots
Spinach
Avacado
189
What does a deficiency in vitamin E cause?
Fat malabsorption
premature infants
Abetalipoproteinaemia
190
What does a deficiency in vitamin E cause?
Fat malabsorption
premature infants
Abetalipoproteinaemia
191
What are the functions of vitamin K?
Responsible for the activation of some blood clotting factors
necessary for liver synthesis of plasma clotting factors II, VII, IX and X
192
What are the four sources of vitamin K
VK1 = Phylloquinone (Synthesised in plants and food)
VK2 = Menaquinone (Synthesised in intestinal bacteria)
Synthetic vitamin K's
K3 (Menadione)
K4 (Menadiol)
193
What does a deficiency in vitamin K result in?
Haemorrhagic disease of the newborn
194
What are the sources of vitamin C
Fresh fruit and vegetables
195
What are the functions of vitamin C
Collagen synthesis
Antioxidant
Iron absorption
196
What does a deficiency in vitamin C causes ?
Easy bruising and bleeding
Teeth and gum disease
Hair loss
197
Where is folate found?
Foods high in folic acid
198
What does a deficiency in folate cause?
Macrolytic anaemia
High homocysteine levels
Foetal development abnormalities
199
What does a deficiency in folate cause?
Macrolytic anaemia
High homocysteine levels
Foetal development abnormalities
200
Describe the length of the foregut?
Runs from the mouth to the common bile duct
201
Describe the length of the midgut?
Runs from the common bile duct to 2/3 transverse colon
202
Describe the length of the hindgut
Runs from the 2/3 transverse Colon to the anal canal
203
What is the blood supply of the foregut?
coeliac artery
204
what is the blood supply of the midgut?
superior mesenteric artery
205
What is the blood supply of the hindgut?
Inferior mesenteric artery
206
What are the components of the foregut?
pharynx, oesophagus, stomach, proximal half of duodenum
207
What are the components of the midgut?
```
Distal half of the duodenum
jejunum
Ileum
Caecum
Appendix
Ascending colon
right 2/3 of transverse colon
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208
What are the components of the hindgut?
```
Left 1/3 of the transverse Colon
Descending colon
sigmoid colon
rectum
Anal canal
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209
At what point does embryonic folding begin?
4th week
210
In what two planes does embryological folding occur?
Horizontal
| Medial
211
What does embryological folding in the horizontal plane form
two lateral body folds
212
What does embryological folding in the medial plane form
A cranial and caudal fold
213
How is the primitive gut tube formed?
Endoderm folds towards the midline and fuses incoporating the yolk sac to form a tube
214
How is the primitive gut tube formed?
Endoderm folds towards the midline and fuses incoporating the yolk sac to form a tube
215
What is the primitive gut tube derived from
Endoderm and visceral mesoderm
216
What does the endoderm give rise to in the gut?
Epithelial lining of GIT
Hepatocytes
Endo/Exocrine cells of pancreas
217
What does the visceral mesoderm give rise to in the gut?
Muscle, connective tissue and peritoneal components of the gut wall
Gland connective tissue
218
How and when does the mouth form?
Foregut at cranial end closed by oropharyngeal membrane which ruptures at 4th week to form mouth
219
How and when does the anus form?
Hindgut lies at the caudal end and is closed by the cloacal membrane which ruptures at 7th week forming anus
220
What is the nerve supply of the foregut?
Greater splanchnic nerve T5-T9
221
What is the nerve supply of the hindgut?
Least splanchnic nerve T12-L1
222
What is the nerve supply of the hindgut?
Least splanchnic nerve T12-L1
223
How is the primary intestinal loop connected to the yolk sac?
By the vitelline loop
224
What does the cephalic portion of the primary intestinal loop form?
distal duodenum
Ileum
Jejunum
225
What odes the caudal portion of the primary intestinal loop form?
```
Lower Ileum
Caecum
Appendix
Ascending Colon
Proximal 2/3 transverse colon
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226
Name the 5 stages of midgut formation
1 and 2 = Elongation and herniation
3. Rotation
4. Retraction of herniated loops
5. Fixation
227
What happens in stage 1 and 2 of midgut formation
Elongation and herniation
Elongation of cephalic limb of primary intestinal loop
Intestine herniates into extra embryonic cavity due to expansion of liver making the abdominal cavity too small
228
What happens in stage 4 of midgut formation?
Retraction of herniated loops occurs in 10th week due to regression of mesonephric kidney, reduced liver growth and expansion of abdominal cavity
Proximal jejunum returns first
Caecal bud returns last and lies in upper right quadrant before descending into right iliac fossa placing ascending colon and hepatic flexure
229
What happens in stage 4 of midgut formation?
Retraction of herniated loops occurs in 10th week due to regression of mesonephric kidney, reduced liver growth and expansion of abdominal cavity
Proximal jejunum returns first
Caecal bud returns last and lies in upper right quadrant before descending into right iliac fossa placing ascending colon and hepatic flexure
230
What happens during stage 5 of midgut formation?
Fixation
Ascending and descending colon reach definitive positions and their mesenteries press against peritoneum and fuse so become anchored retroperitoneally
Appendix, lower caecum and sigmoid colon retain their free mesenteries and flexibility
Transverse colon fuses with posterior wall greater omentum and maintains flexibility
231
What component of the abdominal cavity are mobile?
```
Stomach
Jejunum
Ileum
Appendix
Transverse colon
Sigmoid colon
```
232
What component of the abdominal cavity are mobile?
```
Stomach
Jejunum
Ileum
Appendix
Transverse colon
Sigmoid colon
```
233
What are the three main substrates for gluconeogenesis?
Lactic acid
AA
Glycerol
234
What does the dorsal mesogastrium become?
Greater omentum
235
What does the dorsal mesogastrium become?
Greater omentum
236
Describe the composition of the primary secretion
Amount of Na+ and Cl- is equal to water so is Isotonic compared to blood plasma
237
Describe the composition of the secondary secretion
Na+ and Cl- have been removed so are less than water content so is HYPOTONIC compared to blood plasma
238
How does the submandibular gland enter the oral cavity?
Through the submandibular duct (Wharton's Duct) which attaches to the lingual frenulum
239
Which cranial nerve supplies the parotid gland innervation
Glossopharyngeal
240
Which cranial nerve supplies the submandibular and sublingual innervation
Facial
241
Which salivary glands does the superior salivary centre innervate?
Submandibular and sublingual
242
Which salivary gland does the inferior salivary centre innervate
Parotid
243
Describe the course of the nerve supply of the parotid gland
Inferior salivary centre to glossopharyngeal to jugular foramen to middle ear cavity to lesser petrosal nerve to lesser petrosal foramen to otic ganglion to the parotid
244
Describe the course of the nerve supply of the parotid gland
Inferior salivary centre to glossopharyngeal to jugular foramen to middle ear cavity to lesser petrosal nerve to lesser petrosal formamen to otic ganglion to the parotid
245
What is the anterior border of the oral cavity?
Oral vestibule (Gap between the teeth and lips
246
What is the posterior border of the oral cavity?
Palatoglossal arch
247
Which 4 muscles depress the mandible?
Lateral pteygoid
Digastric anterior belly
Mylohyoid
Geniohyoid
248
What is the innervation of lateral pytergoid muscle
Mandibular division of trigeminal nerve
249
What is the innervation of the digastric anterior belly
Mandibular division of trigeminal nerve
250
What is the innervation of myelohyoid
Mandibular division of trigeminal nerve
251
What is the innervation of geniohyoid
Cervical Plexus (Mainly C1)
252
What are the three mandibular elevators and what is their innervation?
Masseter
Temporalis
Medial Pterygoid
All innervated by mandibular division of trigeminal nerve
253
What is the role of the intrinsic muscles of the tongue in the oral phase of swallowing
Creates central trough on tongue for bolus to slide down
254
What is the role of the extrinsic muscles of the tongue in the oral phase of swallowing
Elevate the tongue so the tip touches the hard palate
255
What cranial nerve innervates the intrinsic and extrinsic muscles of the tongue
Hypoglossal nerve
256
What are the two arches of the oral cavity and which is more anterior? what is the space between the arches called?
Palatopharyngeus
Palatohypoglossus
Space between is tonsilar fossa
Palatoglossal is more anterior
257
Which cranial nerve stimulates the uvula to contract and close off the nasopharynx during swallowing?
Vagus nerve
258
What are the two muscles that elevate the soft palate
Levator veli palatini
| Tensor veli palatini
259
What is the innnervation of Levator veli palatini?
Vagus nerve
260
What 3 processes occur to stop the food bolus entering the larynx?
The true vocal cords adduct the glottis
Epiglottis retroverts to cover larynx
Suprahyoids contract to elevate the larynx and pull it anteriorly
261
What muscles contract to help the bolus enter the pharynx?
Palatoglossus
| Palatopharyngeus
262
Which muscles contract to elevate the pharynx and the larynx
Outer longitudinal muscles including stylopharyngeus, salpingopharyngeus and palatopharyngeus
263
Which nerve innervates stylopharyngeus
Glossopharyngeal
264
Which nerve innervates salpingopharyngeus and palatopharyngeus
Vagus
265
Which muscles enable pharyngeal peristalsis to occur?
Superior, middle and inferior pharyngeal constrictors (Inner circular muscles)
266
Which muscle makes up the upper oesophageal sphincter?
Cricopharyngeus which is part of the inferior pharyngeal constrictor
267
What are the two major carbohydrates in food and describe their structure
Amylopectin (Branched) contains alpha 1,4 and alpha 1,6 glycosidic bonds
Amylose (Linear) only contains alpha 1,4
268
What bonds does salivary and pancreatic alpha amylase break
Alpha 1,4 glycosidic bonds
269
What does alpha amylase break amylopectin and amylose into?
Maltose, Maltriose, alpha limit dextrin, lactose, sucrose
270
What are the 4 brush border enzymes in carbohydrate digestion?
Lactase, maltase, sucrase, isomaltase (Breaks down alpha limit dextrin
271
What are the three types of lipase that act in fat digestion?
Lingual lipase
Gastric lipase (From chief cells)
Pancreatic lipase
272
What does bile contain that is important in the emulsification of fats
```
Bile salts (Cholic, chendooxycholic acid
Phospholipids (Lecithin)
```
273
What enzymes does the pancreas release to aid fat digestion
pancreatic lipase
Phospholipase A2
Cholesterol ester hydrolase
274
What does cholic acid react with to form a bile salt?
Taurine
275
What does chendeoxycholic acid react with to form a bile salt
Glycine
