GI Flashcards
1
Q
Primary purpose of digestive tract
A
Primary purpose – Transfer nutrients from ingested food into body’s internal environment – Ingested food is essential as an energy source and as the building blocks of tissues
2
Q
schematic pathway through GI
A
Oral cavity -> esophagus->
stomach -> small intestine ->
large intestine -> rectum
3
Q
What is the statement concerning the amount of liquid entering and leaving Gi
A
The volume of fluid entering the GI tract must equal
the volume leaving
4
Q
4 major functions of GI
A
1. Motility- muscular contractions that mix food and move it forward 2. Secretion- of digestive juices 3. Digestion- Biochemical breakdown of complex food stuffs 4. Absorption –of small absorbable units and water 5. Excretion-elimination of feces
5
Q
2 types of motility in GI
A
Peristaltic contractions ( propulsion) Segmentation contractions : mixing
6
Q
What is the general composition of digestive secretions
A
– Water, electrolytes, and specific organic constituents (enzymes) – Secretions are released into digestive tract lumen on appropriate neural or hormonal stimulation – Normally reabsorbed in one form or another back into blood after their participation in digestion
7
Q
What is digestion
A
the biochemical breakdown of
structurally complex foodstuffs into smaller,
absorbable units
– Accomplished by enzymatic hydrolysis
8
Q
What is enzymatic hydrolysis
A
adding water at the bond site
allows enzymes in the digestive secretions to break
down the bonds that hold the smaller molecular
subunits within the nutrients.
9
Q
Absorbable units of macronutrients
A
- Carbohydrates → monosaccharides
- Proteins → amino acids
- Fats → glycerol and fatty acids
10
Q
Parts of stomach
A
– (cardia)->Fundus ->body -> pyloric antrum
11
Q
what are the parts of the rest of GI after the stomach (also valves)
A
Pyloric valve • Small intestine – Duodenum à jejunum à ileum • Accessory organs: pancreas and liver • Large intestine: colon and rectum • Anus
12
Q
4 general tissue layers in GI
A
- Mucosa
- Submucosa, connective tissue and glands
- Muscularis externa
- Serosa
13
Q
Describe mucosa layer in GI
A
Innermost layer, epithelium, connective
tissue, muscle
14
Q
Describe muscularis externa in GI
A
inner layer of
circular outer of longitudinal, nerves
organized into a plexus-regulate
movement, mechanical breakdown
15
Q
What is serosa in GI
A
Outer layer, connective tissue, fold
connect to form mesentry
16
Q
Three layers in mucosa
A
Mucous elithelium
Lamina propria
Muscularis mucosae
17
Q
2 types of muscular layer in muscularis externa
A
Circular and on top longitudinal
18
Q
Serosa role
A
To prevent friction between other organs
Anchoring everything in place to prevent twisting
19
Q
3 major pairs of salivary glands
A
Parotid gland
Submandibular gland
Sublingual gland
20
Q
Composition of saliva
A
• 99.5% H2O
• 0.5% electrolytes and protein
(amylase, mucus, lysozyme)
21
Q
Salivary gland composition
A
Serous cells are specialized to secrete an enzyme solution
Mucous cells
and then duct is lined with duct epithelium
22
Q
Functions of saliva
A
• Salivary amylase begins digestion of carbohydrates (1 hour then deactivated) • lingual lipase (activated in stomach) • Facilitates swallowing by moistening food • Mucus provides lubrication • Antibacterial action – Lysozyme destroys bacteria – Saliva rinses away material that could serve as food source for bacteria • Rich in bicarbonate buffers (amylase works best at slightly basic pH)
23
Q
In what layer lymphoid nodules are found in GI
A
In lamina propria (mucosa)
24
Q
What cells line the esophagus and what layers
A
Lined with stratified squamous epithelium (has same four layers as entire digestive tract) 1.Mucosa 2.Submucosa, connective tissue and glands 3.Muscularis externa 4.Serosa
25
Esophagus extends between ___
pharynx and
| stomach
26
How food is pushed through esophagus
Peristaltic waves push food through esophagus
27
What sphincters esophagus has at each end
Pharyngoesophageal sphincter
– Keeps entrance closed to prevent
large volumes of air from entering
esophagus and stomach
– Gastroesophageal (cardiac)
sphincter
– Prevents reflux of gastric contents
28
Outter serosa in esophagus has another name and it is ___
Adventitia
29
Stomach is
J-shaped sac-like chamber lying between
| esophagus and small intestine
30
3 main functions of stomach
1. Store ingested food until it can be emptied into
small intestine
2. Secretes hydrochloric acid (HCl) and enzymes
that begin protein digestion(pepsin)
3. Mixing movements convert pulverized food to
chyme
31
2 curvatures of the stomach and where do they attach to
Lesser curvature to organs behind the stomach
| Greater curvature to the large intestine
32
Folds in stomach are called
Rugae
33
What glands are found in the mucosa of the stomach and what they secrete
```
Secretory cells: mucous,
chief (enzymes), parietal (HCl
and intrinsic factor) and
endocrine (ghrelin hormone
that regulates appetite)
• Gastric pits and
• Glands secrete most of the
gastric juice-mucous fluid
containing digestive enzymes
and HCl
```
34
What does inner epithelial layer contains and what does it secrete and serves as
```
• Serves as protective surface
• Modified for secretion and
absorption
• Contains
– Exocrine gland cells – secrete
digestive juices
– Endocrine gland cells (secretes
into blood or tissue) – secrete
blood-borne gastrointestinal
hormones
– Epithelial cells – specialized for
absorbing digestive nutrients
```
35
What is lamina propria, what does it have
```
Lamina propria-thin layer of
connective tissue
• Houses gut-associated lymphoid
tissue (GALT)
– Important in defense against
disease-causing intestinal
bacteria (at the base of each crypt there are cells secreting bactericidal enzymes)
```
36
what type of muscles is in muscularis mucosa
Smooth muscle
37
Rugae is marked by ___
depressions
| called gastric pits
38
We have villi only in
Small intestine
39
Submucosa role and what is it
```
Thick layer of
connective tissue
• Provides
digestive tract
with distensibility
and elasticity
• Contains larger
blood and lymph
vessels
• Contains nerve
network known
as submucosal
plexus (imp for
exocrine function
and contraction
of muscles)
```
40
Difference between circular and longitudinal muscles
```
Circular layer
• Inner layer
• Contraction
decreases
diameter of lumen
– Longitudinal layer
• Outer layer
• Contraction
shortens the tube
```
41
What is mesenterius
Double sheets of serous membranes composed
of parietal and visceral peritoneum
- Stabilize the positions of some organs
- Prevent intestines from getting tangled during
digestion
- Provide a pathway for blood vessels, nerves,
and lymphatic vessels servicing the digestive
tract
42
Digestive motility and secretion are regulated by
– Autonomous smooth muscle function
| – Gastrointestinal hormones
43
4 aspects in gastric motility and characteristics of each
– Filling
• Involves muscular relaxation
– Enhances stomach’s ability to accommodate the extra
volume of food with little rise in stomach pressure
– Triggered by act of eating
– Storage
• Takes place in body of stomach
– Mixing
• Takes place in antrum of stomach
– Emptying
• Largely controlled by factors in duodenum
44
Mixing
actions in the stomach
include both
propulsion
| and retropulsion
45
____ is main factor that influences
| strength of contraction
Amount of chyme in stomach
46
In what state the food should be before moving to small intestine
Liquid
47
How duodenum and stomach regulate the emptying of chyme to SI on the example of fat
Fat is digested and absorbed more slowly than other
nutrients
• Fat digestion and absorption takes place only within lumen of
small intestine
• When fat is already in duodenum, further gastric emptying of
additional fatty stomach contents is prevented until the
existing fat is completely processed
• For ex a high fat meal may take 6 hours to empty whereas a
lean meat and potatoes meal may take only 3 hours
48
How duodenum and stomach regulate the emptying of chyme to SI on the example of acid
The stomach secretes HCl and highly acidic chyme is
neutralized in the duodenum by sodium bicarbonate
(secreted by the pancreas)
• Unneutralized acid in duodenum inhibits further emptying of
acidic gastric contents until neutralization can be
accomplished
49
How duodenum and stomach regulate the emptying of chyme to SI on the example of hypertonicity
build up of amino acids and glucose
molecules slows gastric emptying. When osmolarity
of duodenal contents starts to rise closure to stomach.
50
How duodenum and stomach regulate the emptying of chyme to SI on the example of distension
Too much chyme in duodenum inhibits emptying of even
| more gastric contents
51
Factors Controlling Gastric Emptying
One of the Factors (fat, hypertonicity, acid, distension) trigger either
1. A Neural response
• Collectively called enterogastric reflex acts to slow the peristaltic
activity – smooth muscle contractions-autonomic system
OR
2. Hormonal response
• Release of GIP (gastric inhibitory peptide), endocrine hormone that
acts on gastric muscle to decrease peristalsis and thus slow
passage of food into the duodenum
• Additional factors that that influence gastric motility
– Emotions
• Sadness and fear – tend to decrease motility
• Anger and aggression – tend to increase motility
– Intense pain – tends to inhibit motility
52
Two distinct areas of gastric
mucosa that secrete gastric
juice
– Oxyntic mucosa
• Lines body and fundus
– Pyloric gland area (PGA)
• Lines the antrum
53
Gastric juice : content
(strongly acidic
secretion from glands,
enzymes ex pepsin, intrinsic
factor, mucus, water)
54
Three phases of gastric secretion:
Cephalic phase
Gastric phase
Intestinal phase
55
What is cephalic phase
Sensation or thought
about food are relayed to the brainstem (medulla). In response
parasympathetic signals to the gastric mucosa are
initiated. Stimulates secretion of gastric juice.
56
What is gastric phase of juice secretions
The distension of the stomach caused by the presence of food
triggers local and parasympathetic reflexes that increase secretion
of gastric juice. Gastrin (secreted by endocrine G cells) is a
digestive hormone secreted by mucosa in presence of food causes
increased secretion of gastric juice.
57
What is Intestinal phase
Triggers endocrine response
Once food enters the SI, stomach activity is inhibited by decreased gastric
juice secretion initiated by GIP (gastric inhibitory peptide), CCK and secretin
–opposes gastric juice secretion. Opposes action of gastrin. Stimulates
ejection of bile from the pancreas required for neutralization of HCl in the
duodenum
58
Two type of secretory tissues in the stomach
```
Oxyntic mucosa ( the upper layer)
Pyloric gland area ( near the pyloric sphincter)
```
59
In what layer gastric pits are found
Mucosa
60
What cells oxyntic layer has
Contains contains gastric glands which have endocrine, chief, parietal, ECL (enterochomaffin-like) cells
61
What connects gastric gland with the surface of the stomach and what is found there
Gastric pit, with mucosa cells
62
Mucous cells: role and type of gland
Exocrine
secrete mucus,
protects epithelial cells in the stomach against pepsin and acid
63
Chief cells: role and type of gland
exocrine
release pepsinogen and chymosin
pepsinogen when
activated begins protein digestion
64
Parietal cells: role and type of gland
Exocrine
```
HCl, activates
pepsinogen, denatures proteins,
breaks down connective tissue,
kills microorganisms, intrinsic
factor imp for vitamin B12
absorption
```
65
ECL: role and type of cell
Exocrine neuroendocrine
| Release histamine that stimulates parietal cells
66
Pyloric gland area has what type of cells
contain mucous
| cells and G cells, D cells
67
Role of g cells and what type of cells
Endocrine
G-cells secrete gastrin which stimulates
exocrine cells- to secrete greater gastric
juice which has high HCl and pesinogen.
Mechanism to ensure that when there is
food in the stomach there will be enough
juice and enzymes there to digest it.
promotes digestion
68
D cells : role and type of cell
Endocrine
```
D cells produce the only inhibitiry
secretions-somatostatin
• Acts to inhibits parietal cells (HCl), G
cells (gastrin which increases digestive
juice secretion) and ECl cells.
```
69
difference between endocrine and exocrine glands
Endocrine: ductless glands
that secrete hormones
• Exocrine-secrete through
ducts into a cavity
70
Role of HCl
```
Activates pepsinogen to
active enzyme pepsin
and provides acid
medium for optimal
pepsin activity
– Aids in breakdown of
connective tissue and
muscle fibers
– Denatures protein
– Along with salivary
lysozyme, kills most of
the microorganisms
ingested with food
```
71
How HCl gets produced in gastric parietal cells
H-K pump on the apical surface of parietal cells pumps K in and H+ out. NOTE: H+ is coming from carbonic acid, a combination of CO2 and H2O in parietal cells. It is unstable , so it breaks down to HCO3- and H+. HCO3- goes out of the cells to the capillary through chloride shift and this Cl- from blood can get inside parietal cells
Chloride ions are pumped into the lumen of the stomach, where it reacts with H+
72
The gastric mucosal barrier made up of the following components enables the stomach to contain acid without injuring itself:
1) The luminal membranes of the gastric mucosal cells are impermeable to H+ so that HCl cannot penetrate into the cells
2) The cells are joined by tight junctions that prevent HCl from penetrating between them
3) A mucus coating over the gastric mucosa offers further protection
73
What happens when the gastric mucosal barrier is damaged
Gastric ulcers
74
What is the cause of 60% of ulcers
Helicobacter pylori
75
How H.pylori survives the acid in the stomach
H pylori has a unique, acid gated membrane channel, which effectively controls the amount of alkali produced by the bacterium to combat gastric acid, allowing it to survive and grow in gastric acid.
76
Where usually you can find H.pylori in the stomach
In Fundus where there is less acid
It uses flagella to burrow itself below mucus cells
77
How H.pylori causes ulcers
Damage mucus barrier and
tight junction
• Allows HCl to damage
intestinal tissue
78
H.pylori is treated with
Antibiotics
79
What is the other cause of ulcers apart form H.pylori
emotion/stress can increase
| gastric juice secretion
80
What is the way to treat ulcers if not concentrating on bacteria
By PPI (Proton pump inhibitors) to prevent HCl formation
81
Examples of PPI
omeprazole, Lansoprazole
82
Action of PPI
It can act at different levels: inhibit H/K ATPase, so no Hydrogen pumped into the stomach
83
What is GERD and what is the treatment
When lower esophageal sphincter fails to stay closed and stomach acid damages the lining of the esophagus
Treated with PPIs
84
Ulcers can be from ____
the
overuse of NSAIDs (a drug class that reduce pain, decrease fever, prevent blood clots and, in higher doses, decrease inflammation) or H.
Pylori or stress/emotions
85
Pancreas is
Mixture of exocrine and endocrine tissue
• Elongated gland located behind and below the
stomach
86
Endocrine function of pancreas
```
performed by Islets of Langerhans
• Found throughout pancreas
• Secrete insulin (Beta cells-causes uptake of
glucose) and glucagon (released when low
glucose)
```
87
Exocrine function of pancreas
```
Secretes pancreatic juice consisting of
• Pancreatic enzymes (Trypsinogen,
lipases, nucleases) actively secreted by
acinar cells
• Aqueous alkaline solution actively secreted
by duct cells that line pancreatic ductsimportant
for neutralizing stomach contents
in duodenum
```
88
What cells secrete pancreatic enzymes
Acinar
89
exocrine secretion of pancreas are regulated by
Secretin-(from intestinal mucosa)
– CCK-Cholecystokinin (from intestinal mucosa)
– Both act to stimulate release of pancreatic juice
90
What are proteolytic enzymes in pancreas
Trypsinogen - converted to active form trypsin (converting
enzymes sits poised on mucosal epithelium)
• Chymotrypsinogen – converted to active form chymotrysin
91
Action of pancreatic amylase
Converts polysaccharides into the disaccharide amylase
92
What is particular about pancreatic lipase
Only enzyme secreted throughout entire digestive system that
| can digest fat
93
What cells secrete NaHCO3 in pancreas
Duct cells
94
What is proteose
a water-soluble compound produced during
| digestion by hydrolytic breakdown of proteins
95
Protein is broken down to peptides and proteoses by proteases in gastric and pancreatic juices.
What is going to break down peptides and proteoses to amino acids
peptides:intestinal peptidases
Proteoses: proteases in pancreatic juices
96
Is pepsinogen active?
No, pepsin is active
97
How liver is important to digestion
secretion of bile
| salts which are important for fat digestion
98
What is the largest gland in the body
Liver
99
Anatomy of liver
Consists of two lobes which are highly vascularized
100
Liver functions
detoxification
- bile secretion
- stores iron, vit D, A B12
- site of hematopoiesis during fetal development
101
Right and left lobe of the liver is separated by
Round ligament
102
All the nutrients from the intestine are going to the liver by
Hepatic portal vein
103
Functional unit of liver is
Liver acinus
104
Liver acinus has the form of ___, and each end has ___
Hexagon
| Hepatic triad: hepatic portal vein, hepatic artery and bile ductule
105
Functions of liver
Synthesis and secretion of bile
Storage of glycogen and lipid reserves
Maintenance of normal blood levels of glucose, AAs and FAs
Synthesis and interconversion of nutrient types
Synthesis and release of cholesterol bound to transport proteins
Inactivation of toxins, lipid-soluble drugs
Storage of iron reserves
Storage of fat-soluble vitamins
Absorption and breakdown of circulating hormones (insulin, epinephrine) and immunoglobins
106
How liver and gall bladder is connected to intestine
ducts from the liver that carry the bile to be ejected into the
duodenum
• The hepatic ducts fuse with the gallbladder cystic duct, to
form the common bile duct that enters into the duodenum
107
Where bile is stored between meals
Stored and concentrated in gallbladder
108
What are lecithins, where they are produced and what is their function
Derivatives of cholesterol
– Convert large fat globules into a liquid emulsion
– After participation in fat digestion and absorption,
most are reabsorbed into the blood
109
Blood flow through liver
From intestine - hepatic portal vein
From the heart: hepatic artery
From liver to inferior vena cava-hepatic vein
110
What nutrients are stored in the liver
Glucagon
| Fat-soluble vitamins A, D, E, and K
111
How liver monitors and adjust circulating nutrients
High blood glucose triggers synthesis of glycogen
• Low blood glucose triggers breakdown of glycogen and
release of glucose
112
What is the function of Phagocytic Kupffer cells in the liver
remove old or damaged
| RBCs, debris, and pathogens from blood
113
What is the function of plasma proteins secreted by liver
Determine osmotic pressure of plasma
– Function as nutrient transporters
– Key elements of clotting and complement cascades
114
What is NAFLD
The most frequent form of fatty liver disease
– namely the non-alcoholic fatty liver disease
(NAFLD)
– form of chronic liver disease, resembling the
histological changes of alcoholic liver disease
– found in subjects who do not abuse alcohol
– Is tightly-linked with type II DM
– prevalence of NAFLD is growing worldwide due
to the increasing prevalence of obesity, diabetes
and the metabolic syndrome.
115
What is NASH and how it is identified
Non Alcoholic Steatohepatitis (NASH)
```
Identified by
abnormal lipid
accumulation and
presence of
inflammatory cells
```
116
NAFLD progression
Healthy liver->NAFLD->NASH
This steps are reversible
From NASH to cirrhosis is irreversible
117
What is steatosis
comprises abnormal accumulation of triglycerides in
| hepatocytes in response to metabolic, toxic, and viral conditions
118
What is the normal thing about liver and aging
Macrovesicular steatosis
119
A progression of macrovesicular steatosis is
Microvesicular
120
What is cirrhosis
```
chronic or scarred liver as a
result of chronic inflammation due to
hepatits, chemicals that destroy
hepatocytes, parasites that infect the liver,
or alcoholism
```
121
What is hepatitis
inflammation of the liver caused
| by viruses, drugs, and chemicals
122
Hepatitis A: cause, symptoms and effect
```
spread by fecal
contamination of objects (food, clothing,
toys, eating utensils: fecal-oral route)
- Loss of appetite, malaise, diarrhea,
nausea, fever, chills
- Does not cause lasting liver damage
```
123
Hepatitis B: cause, symptoms and effect
spread primarily through
sexual contact and contaminated syringes
and transfusion equipment; also via saliva
and tears (bodily fluids)
- Can produce cirrhosis and possible liver
cancer
- Can be carriers
124
Hepatitis C is similar to
Hepatitis B
125
Common bile duct and pancreatic duct are both controlled by
Hepatopancreatic sphincter
126
Where gallbladder is found
the posterior surface of the
| liver’s right lobe
127
Functions of the gallbladder
Stores bile
– Releases bile into duodenum, but only under
stimulation of hormone cholecystokinin (CCK
128
How much bile there can be in gallbladder and what is happening with it over time
```
Full gallbladder contains 40–70 mL bile
– Bile composition gradually changes in
gallbladder:
• Water is absorbed
• Bile salts and solutes become concentrated
```
129
Where most digestion and absorption of food happens and what is done to make it more efficient
Small intestine
Surface area increased by circular folds, villi, and
microvilli
130
The end of small intestine is
ileocecal valve
131
Functions of small intestine
Segmentations mix chyme with digestive juices
and bring food to mucosa for absorption; peristalsis
2. Completes the digestion of carbohydrates,
proteins, and lipids; begins and completes
digestion of nucleic acids
3. Absorbs ~90% of nutrients (including water) that
pass through the digestive system
132
What is folds of mucosa
| and submucosa
Circular folds (plicae circulares):
133
What is villi and microvilli
Villi: fingerlike projections of mucosa; increase SA
```
- Microvilli: projections of the apical membrane of the
absorptive cells (villi)
```
134
Structure of villi
- Each is covered by epithelium with a core of
lamina propria with an arteriole, a venule, a
capillary network, and a lacteal embedded)
135
3 parts of small intestine
```
Duodenum-the uppermost
(shortest)portion and is the
part to which the pyloric end
of the stomach attaches
– Jejunum- commences at point
where the tube turns
downwards
– Ileum –(longest) last segment
with no clear demarcation
```
136
2 types of digestive motility and their function
Propulsive (peristaltic) movements
– Push contents forward through the digestive tract
• Mixing movements (segmentation)
– Serve two functions
» Mixing food with digestive juices promotes digestion
of foods
» Facilitates absorption by exposing all parts of
intestinal contents to absorbing surfaces of digestive
tract
137
Segmentation movements
ringlike contractions
138
Segmentation is initiated by
pacemaker cells in small intestine
| which produce basic electrical rhythm (BER)
139
Circular smooth muscle responsiveness is initiated by
distension of intestine, gastrin, and
| extrinsic nerve activity
140
What is migrating motility complex
a cyclic, recurring motility pattern that occurs in the stomach and small bowel during fasting; it is interrupted by feeding.
Sweeps intestines clean between meals
141
Who is doing the work of digestion in small intestine
Juice secreted by small intestine does not contain
any digestive enzymes
• Digestion
– Pancreatic enzymes continue carbohydrate and
protein
– Brush-border enzymes complete digestion of
carbohydrates and protein
– Fat is digested entirely within small intestine
lumen by pancreatic lipase
142
Most of absorption happens in
duodenum and jejunum
143
Lining of small intestine is changed every __
3 days
144
How TGs undergo hydrolysis and absorption
```
Triglycerides are
subsequently broken into
monoglycerides and longand
short-chain fatty acids
• Short-chain fatty acids can
often be absorbed
• Bile salts surround longchain
fatty acids and
monoglycerides forming
tiny spheres called
micelles
• Then undergo hydrolysis
by pancreatic lipase
• Absorbed by brush border
```
145
Where chylomicrons are assembled
Golgi in small intestine cells and then through lacteal into lymph
146
Amylase function
breaks down starch, glycogen into disaccharides
147
How proteins are absorbed
After digestion
Di and tripeptides cotransport paired with H+ via Na(in)-H(lumen)+( pump
Amino acids contransport with Na
Small peptides are carried intact across the cell by transcytosis-" blood
148
Parts of large intestine
– Colon
– Cecum
– Appendix
– Rectum
149
Parts of colon
ascending colon, transverse colon,
| descending colon, sigmoid colon
150
Function of large intestine
```
Reabsorption of water
– Reabsorption of bile salts
– Absorption of vitamins (vitamin K, pantothenic
acid B5, biotin) produced by bacteria
-Preparation of feces for excretion
```
151
Difference between anatomy of large and small intestine
Has a larger diameter and thinner wall than small intestine
– The wall of the colon:
• Forms a series of pouches (haustra)
152
What is haustra
Haustra permit expansion and elongation of colon
Muscle tone in taeniae coli creates the haustra
153
What is taeniae coli
Three longitudinal bands of smooth muscle (taeniae coli):
• Run along outer surfaces of colon
• Deep to the serosa
• Similar to outer layer of muscularis externa
154
Borders of ascending and transverse colon
Ascending Colon
– Begins at superior border of cecum
–
bends at right colic flexure (hepatic flexure)
• Transverse Colon
– Crosses abdomen from right to left; turns at left colic
flexure (splenic flexure)
– Is separated from anterior abdominal wall by greater
omentum
155
Sigmoid colon starts ___
At sigmoid flexure
156
When we start to have an urge to defecate
Movement of fecal material into rectum
157
2 sphincters in anal
Internal anal sphincter:
• Has smooth muscle cells, not under voluntary control
– External anal sphincter:
• Encircles distal portion of anal canal
• A ring of skeletal muscle fibers, under voluntary control
158
Histology of the large intestine
Lack villi or other structures that increase SA
– Abundance of mucous cells; mostly absorptive
and goblet cells
159
when haustral churning occurs
Haustra remain relaxed and become distended
while they fill
- Distension reaches a certain point, walls contract
and squeeze contents into next haustrum
- Peristalsis occurs at a slower rate
160
What is appendix
Vestigial organ: shrunken remainder of cecum
– Is dominated by lymphoid nodules (a lymphoid
organ
161
What is appendicitis, cure, causes
```
Inflammation of the appendix
• High mortality
• Requires immediate surgical removal
• Possible causes:
- Obstruction
- Low transit time
- Low dietary fiber intake
- (none are mutually exclusive)
```
162
Gastrin: stimulus, origin, target and effects
Vagus nerve stimulation or arrival of food in the stomach (produced in stomach)
Arrival of chyme containing large quantities of undigested proteins ( produced in duodenum)
Target: stomach
Effects; stimulate production of acids and enzymes, increases motility
163
Secretin: stimulus, origin, target and effects
Arrival of chyme in the duodenum
Produced in duodenum
Target: pancreas, stomach, liver
Effects: stimulates production of alkali buffers
inhibits gastric secretion and motility
Increases rate if bile secretion
164
CCK: stimulus, origin, target and effects
Arrival of chyme containing lipids and partially digested proteins
Secreted in duodenum
Pancreas-stimulates production of pancreatic enzymes
Gallbladder: Stimulated contraction of gallbladder
Duodenum: causes relaxation of sphincter at base of bile duct
stomach-inhibits gastric secretion and motility
CNS-may reduce hunger
165
Gastric inhibitory peptide: stimulus, origin, target and effects
Arrival of chyme containing large quantities of fats and glucose
ORIGIN: duodenum and stomach
Target: pancreas -stimulates release of insulin
In stomach -inhibits gastric secretion and motility
166
What is the second leading cause if cancer mortality in Canada
Colon cancer
167
potential causes of colon cancer
Incidence increased among persons with family history
• Also increases with persons with Crohn’s
disease, ulcerative colitis and those with
adenomatous polyposis (genetic: autosomal
dominant)
• Diet also plays a role
- Dietary fat intake (increases bile acid synthesis,
may be converted into carcinogens by bacterial
flora in colon)
- Refined sugar intake (enhances above)
- Fiber intake (increases stool bulk thereby diluting
and removing potential carcinogens)
- Adequacy of protective micronutrients such as
vitamins A,C, and E in diet (refined diets often
contain reduced amounts of A,C, and E which
may act as oxygen free radical scavengers
-Polips grow
