DIGESTIVE SYSTEM LECTURE Flashcards
1
Q
List the different terms for the digestive tract.
A
the digestive tract is also known as the alimentary canal or the gastrointestinal tract
2
Q
Approximately how long is the digestive tract?
A
the digestive tract is approximately 30ft
3
Q
What are the main organs of the digestive system?
A
the main organs of the digestive tract are the oral cavity, pharynx, esophagus, stomach, small intestine, and large intestine
4
Q
List the accessory organs of the digestive system.
A
the accessory organs include the teeth, tongue, salivary glands, liver, gallbladder, and pancreas
5
Q
What are the functions of the digestive system?
A
the digestive system functions to process and absorb food while also eliminating waste
6
Q
How many steps are in the major digestion process?
A
the are six steps in the major digestion process
7
Q
List the first three steps of the major digestion process.
A
the first three steps are ingestion, propulsion, and mechanical breakdown
8
Q
What are the last three steps of the major digestion process?
A
the last three steps of the major digestion process are digestion, absorption, and defecation
9
Q
Describe the ingestion stage of the digestion process.
A
the ingestion stage is when food/ liquids are consumed
10
Q
Describe the propulsion stage of the digestion process.
A
the propulsion stage is moved along by swallowing and peristalsis
11
Q
Describe the mechanical stage of the digestion process.
A
the mechanical stage is when food is physically being broken down
12
Q
Describe the digestion stage of the digestion process.
A
the digestion stage is when chemicals/ enzymes break down food into its smallest forms
13
Q
Describe the absorption stage of the digestion process.
A
the absorption is when nutrients from food are absorbed into blood/ lymph
14
Q
Describe the defecation stage of the digestion process.
A
the defecation stage is when waste products are eliminated via feces
15
Q
What mechanisms control the digestive tract?
A
the digestive tract is controlled via the neural and hormonal mechanisms
16
Q
Define peristaltic contractions.
A
peristaltic contractions are wave-like contractions that propel the food bolus down the digestive tract
17
Q
Define peritoneum.
A
the peritoneum are slippery serous membranes found in the abdominopelvic cavity
18
Q
Describe the visceral peritoneum.
A
the visceral peritoneum covers the external surfaces of most digestive organs
19
Q
Describe the parietal peritoneum.
A
the parietal peritoneum lines the body wall
20
Q
Describe the peritoneal cavity.
A
the peritoneal cavity is a slit-like space found between the two peritoneums
21
Q
Which peritoneum layer contains the peritoneal fluid?
A
the parietal peritoneum contains peritoneal fluid
22
Q
What is the function of the peritoneal fluid?
A
the peritoneal fluid functions to reduce friction in the abdominal cavity
23
Q
Parietal fluid is secreted by what?
A
parietal fluid is secreted by the serous membrane
24
Q
Describe the mesentery layer.
A
the mesentery layer is a double-layered peritoneum that extends to digestive organs
25
What is the function of the mesentery layer?
the mesentery layer function to provide blood vessels, lymphatics, nerves; also holds organs in place and stores fat
26
What are the four primary tunics of the alimentary canal?
the four primary tunics are the mucosa, submucosa, muscularis externa, and serosa
27
Describe the mucosal layer of the alimentary canal.
the mucosa is mucous membrane and is the innermost layer; moist epithelial that lines the walls
28
Describe the submucosa layer of the alimentary canal.
the submucosa is external to the mucosa and contains elastic fibers, blood/ lymphatic vessels, lymph nodes, and nerves
29
Describe the muscularis externa layer of the alimentary canal.
the mucularis externa is external to the submucosa and contains round and smooth muscle
30
Describe the functions of the muscularis externa.
the muscularis externa is responsible for segmentation and peristalsis
31
Describe the serosa layer of the alimentary canal.
the serosa layer of the alimentary canal is the outermost layer and is the protective visceral peritoneum
32
Describe the characteristics of splanchnic circulation.
splanchnic circulation contains arteries that branch off the abdominal aorta
33
What is the function of the arteries in the splanchnic circulation?
the arteries in the splanchnic circulation nourish the digestive organs and hepatic portal circulation
34
What is the function of the cephalic trunk?
the cephalic trunk functions to supply blood to the spleen, liver, and stomach
35
What is the function of the mesenteric arteries?
the mesenteric arteries function to supply blood to the small and large intestines
36
Describe the functions of the enteric nervous system.
the enteric nervous system are neurons functioning to regulate digestive tract motility, secretion, and blood flow
37
What are the functions of the mouth?
the mouth functions to promote ingestion, mechanical/ chemical digestion, and deglutition
38
Describe the tongue.
the tongue is a muscular organ that contains taste buds
39
What is another term for taste buds?
taste buds are also known as lingual papillae
40
What are the functions of the tongue?
the tongue functions to grip and reposition food, mix saliva with food, and initiate swallowing
41
The mixing of saliva with form forms a process known as what?
the mixing of saliva with food is a form of chemical digestion
42
Define bolus.
bolus is the end result of food that has been chewed and combined with saliva.
43
What are the functions of the oral palates?
the palates function separate the oral cavity from the nasal cavity and allows breathing while eating
44
The oral palate is separated into what two parts?
the palate is separated into the hard palate and the soft palate
45
At posterior portion of the soft palate dangles what?
at the posterior end of the soft palate is the uvula
46
Which teeth are responsible for cutting?
incisors are responsible for cutting
47
Which teeth are responsible for tearing/ piercing?
canines are responsible for tearing/ piercing
48
Which teeth are responsible for grinding/ crushing?
premolars/ molars are responsible for grinding/ crushing
49
At what age do deciduous teeth form?
deciduous teeth form between the ages of 6-30 months old
50
At what age do permanent teeth form?
permanent teeth form between the ages of 6-25 years old
51
At what ages do wisdom teeth form?
wisdom teeth form between the ages of 17-25 years old
52
What are the two major regions of teeth?
the two major regions of teeth are the crown and the root
53
Describe the crown portion of the teeth.
the crown portion of the teeth is the exposed enamel covered portion
54
Describe the root portion of the tooth.
the root portion of the tooth is the portion that is embedded in the jaw
55
What percentage of saliva is water?
saliva is 97-99% water
56
What is the normal pH range of saliva?
saliva is normally between a pH of 6.8-70
57
What are the functions of saliva?
saliva functions to:
- moisten the mouth
- digest some starch
- cleanse the teeth
- inhibit bacterial growth
- dissolve molecules
- and moisten food
58
What are two enzymes in the oral cavity that aid in digestion?
salivary amylase and lingual lipase are enzymes in the oral cavity that aid in digestion
59
What is the function of salivary amylase?
salivary amylase functions to begin carbohydrate digestion before it is swallowed
60
What is the function of lingual lipase?
lingual lipase is an enzyme that digests fats/ lipids after is has been swallowed
61
Where is salivary amylase activated?
salivary amylase is activated in the mouth
62
Where is lingual lipase activated?
lingual lipase is activated in the stomach
63
What is the function of mucus?
mucus functions to bind and lubricate food creating bolus and aids in swallowing
64
Describe the function of a lysosome.
lysosomes function to kill bacteria
65
What is a lysosome?
a lysosome is an immunoglobin A (IgA) antibody that inhibits bacterial growth
66
What are a few electrolyte/ metabolic waste products?
some examples of electrolyte and metabolic waste products are NA+, K+, Cl-, HCO3-, urea, and uric acid
67
What are the two types of salivary glands?
the two types of salivary glands are the intrinsic (minor) and extrinsic (major) types
68
What are the functions of the intrinsic (minor) salivary glands?
the intrinsic salivary glands function to secrete small amounts of saliva at a constant rate
69
Where are intrinsic (minor) salivary glands located?
intrinsic salivary glands are located inside if the oral tissue
70
Where are extrinsic (major) salivary glands located?
extrinsic salivary glands are located outside of the oral mucosa
71
What is the function of extrinsic (major) salivary glands?
extrinsic salivary glands function to secrete large amount of saliva when stimulated by food
72
How do extrinsic salivary glands communicate with the oral cavity?
extrinsic salivary glands communicate with the oral cavity via ducts
73
What is a clinical condition that occurs in the extrinsic salivary glands?
mumps is a clinical condition that occurs in the extrinsic salivary glands
74
List a few types of extrinsic (major) salivary glands.
a few types of extrinsic salivary glands are the parotid glands, submandibular gland, and sublingual gland
75
List the first two steps of salivation.
food stimulates the tactile, pressure and taste receptors in the mouth and sends signals to the salivary nuclei in the brainstem
76
What are the last three steps of salivation?
salivary nuclei in the brainstem are activated and then activate motor neurons which stimulate salivary glands and initiates the production of saliva
77
What is the function of pharynx?
the pharynx functions to push food down the digestive tract
78
How long is the average esophagus?
the esophagus is ~10 inches long
79
Describe the function of the esophagus.
the esophagus functions to pass food down the mediastinum; penetrating the diaphragm and meeting the stomach
80
What is the contact between the esophagus and the diaphragm called?
the contact between the diaphragm and the esophagus is called the esophageal hiatus
81
What is the contact between the esophagus and the stomach called?
the contact between the esophagus and the stomach is called the cardiac orifice
82
The cardiac orifice contains what?
the cardiac orifice contains the gastroesophageal and cardiac sphincter
83
Describe this clinical condition: heartburn/ acid reflux.
heartburn is when stomach contents move backwards/ upwards through the sphincter muscle of the cardiac orifice
84
What is the first symptom of gastroesophageal reflux disease (GERD)?
the first symptom of gastroesophageal reflux disease is heartburn
85
Define peristalsis.
peristalsis is a wave of muscular contraction triggered by stretching in upper esophagus
86
What is the function of peristalsis?
peristalsis functions to push bolus ahead of it and down the digestive tract
87
How long does is take liquids to reach the stomach?
it takes liquids ~1-2 seconds to reach the stomach
87
What is the role of gravity in digestion?
gravity assists digestion when sitting upright however peristalsis moves food down the digestive tract regardless of anatomical position
87
How long does it take for food to reach the stomach?
it takes food ~4-8 seconds to reach the stomach
88
What are the functions of the stomach?
the stomach functions to store, break down/ liquefy food, and begin the chemical digestion of proteins and smalls amounts of fat
88
Define rugae.
rugae are the ridges in the stomach that flatten when the stomach is filled to allow expansion to occur
88
Describe the anatomical position of the stomach.
the stomach is a j-shaped muscular sac that is located in the upper-left abdominal cavity below the diaphragm
89
What is the internal volume of the stomach when empty?
when empty, the internal volume of the stomach is 50ml
89
What is the internal volume of the stomach after a normal meal?
the internal volume of the stomach after a normal meal is 1.0-1.5L
90
Define chyme?
chyme is a soupy mixture of semi-digested food
90
What is the internal volume of the stomach after a large meal?
after a large meal, the internal volume of the stomach is 4L
90
Where does chyme go after it is finishing being processed in the stomach?
chyme enters the small intestine after it has been processed in the stomach
91
How many regions of the stomach are there?
there are four regions of the stomach
92
What is another term for the body of the stomach?
the body of the stomach is also known as the corpus
92
What are the four regions of the stomach?
the four regions of the stomach are the cardiac, fundic, body, and pyloric regions
93
Describe the fundus region of the stomach.
the fundus region is the thin muscle layer (fundus) is located
94
What is the function of the angular incisura?
the angular incisura functions to separate the stomach into right/ left portions
94
Describe the pyloric region of the stomach.
the pyloric region of the stomach is a thick muscular layer that contains the pyloric sphincter
95
What is the function of the greater/ lesser omentums?
the greater/lesser omentums are mesenteries that tether the stomach to other digestive organs and body wall
96
Describe the system of blood supply to the stomach.
blood to the stomach is supplied and drained into the hepatic portal circulation and is filtered through the liver
96
True or False: the stomach only receives sympathetic nerve fibers.
false; the stomach receives both parasympathetic and sympathetic nerve fibers
97
What are the three glands that the stomach wall contains?
the stomach walls contains the cardiac, pyloric, and gastric glands
97
What are the functions of the three glands located in to stomach walls?
the glands located in the stomach wall function to secrete mucus, acid and enzymes, and hormones
98
How many liters of gastric juice do gastric glands secrete per day?
gastric glands secrete 2-3L of gastric juice per day
99
What are the main components of gastric juice?
the main components of gastric juice are water, hydrochloric acid, and pepsin
100
Describe hydrochloric acid (HCl).
hydrochloric acid is a component of gastric juice that has a pH as low as 0.8; very acidic
101
Which cells of the stomach contain gastric glands?
parietal cells contain gastric glands
102
List the functions of stomach acid.
stomach acid functions to:
- activate pepsin and lingual lipase
- brake up connective tissues and plant cell walls
- convert iron into an absorbable form
- destroy digested bacteria/ pathogens
103
What is the function of pepsin?
pepsin is an enzyme that digests dietary proteins to shorten peptide chains
104
Hydrochloric acid converts pepsinogen to what?
hydrochloric acid converts pepsinogen to pepsin
104
What is the function of chief cells?
chief cells function to secrete pepsinogen
105
What is the function of enteroendocrine cells?
enteroendocrine cells release a variety of chemicals
106
What are examples of the chemicals that enteroendocrine cells release?
some examples are histamine, serotonin, and gastrin
107
Describe the process of gastric motility.
gastric motility is when the stomach exhibits and rhythm and peristaltic contractions
107
How often do peristaltic contractions occur?
peristaltic contractions occur every 20 seconds
108
Where do peristaltic contractions initially occur?
peristaltic contractions initially occur in the fundus and grow stronger toward the pyloric region
108
How is the peristaltic contraction pace set?
peristaltic contraction rate is set by enteric pacemaker cells
109
Where are the pacemaker cells for peristaltic contractions located?
pacemaker cells for peristaltic contractions are locate between smooth muscle layers
109
What is the function of stomach contractions?
stomach contractions churn food and mix it with gastric juice; promotes physical/ chemical digestion
110
How do stomach contractions affect chyme?
each contraction forces a small amount of chyme into the duodenum
111
Approximately how much chyme is forced into the duodenum per stomach contraction?
~3L is forced into the duodenum per muscle contraction
111
How long does it take the stomach to empty after a regular meal?
it takes the stomach ~4 hours to empty
112
How long does it take the stomach to enter after a high fat meal?
it takes the stomach ~6 or more hours to empty after a high fat meal
113
What are some causes of vomiting?
some causes of vomiting are stomach stretching excessively, psychological stimuli, and/ or chemical irritants
113
Where is the emetic center located?
the emetic center is located in the medulla oblongata
114
What is the function of the emetic center?
the emetic center functions to stimulate the lower esophageal sphincter and cause it to relax while also stimulating the diaphragm and abdominals to contractq
115
How much digestion/ absorption takes place in the stomach?
very little digestion takes place in the stomach and no nutrient absorption
116
Which enzymes in the stomach are responsible for partial digestion?
enzymes such as salivary and gastric enzymes in the stomach
117
What are some of the contents that salivary and gastric enzymes of the stomach partially digest?
some nutrients that are partially digested by gastric/ salivary enzymes are proteins, fats, and some starches
118
Intrinsic factor is secreted by what?
intrinsic factor is secreted by the stomach
119
What is the function of intrinsic factor?
intrinsic factor functions to absorb vitamin B12
120
Describe the mucous coating of the stomach.
the mucous coating of the stomach is a thick, alkaline mucus that is rich in bicarbonate
121
What is the function of the mucosal layer of the stomach?
the mucosal layer of the stomach functions to protect the walls of the stomach from gastric juice
122
Define this clinical condition: gastritis
gastritis is an inflammation of the stomach
123
What are some of the results of gastritis?
gastritis may result in a peptic (gastric) ulcer
124
What does current research suggest about the cause of peptic (gastric) ulcers?
current research indicates that peptic ulcers may be caused by acid-resistant bacteria that burrow within the mucosal layer
125
What is the name of the acid-resistant bacteria that burrows within the mucosal layer of the stomach?
helicobacter pylori are acid-resistant bacteria that burrow within the mucosal layer of the stomach
125
What are the functions of tight junctions within the stomach?
tight junctions function to join epithelial cells of mucosa and prevent gastric juice from leaking into deep tissue layers
126
Describe what occurs with epithelial cell replacements.
stem cells that reside where the gastric pit join the gastric gland are replaced
127
How long do stem cells in the stomach live for?
stem cells live 3-6 days in the stomach before they are replaced
128
True or False: only neural controls stimulate gastric juice secretion.
False; neural and hormonal cells stimulate gastric juice secretion
129
What controls the cephalic phase of gastric juice secretion?
vagus nerve excitation controls the cephalic phase
130
the cephalic phase of gastric juice secretion is controlled by which nervous system?
the cephalic phase of gastric juice secretion is controlled by the peripheral nervous system
131
Describe what happens during the cephalic phase of gastric juice secretion.
gastric juice is released into the stomach due to the anticipation of food; not entered the stomach yet
132
When does the gastric phase of gastric juice secretion occur?
the gastric phase of gastric juice secretion occurs once food has entered the stomach
133
How long does the gastric phase last?
the gastric phase lasts 3-4 hours
134
What stimuli triggers the gastric phase of gastric juice secretion?
the gastric phase is stimulated by stretch receptors in the stomach and chemoreceptors detecting partially digested food
135
What are a few inhibitions/ results of the gastric phase?
some results of the gastric phase are a lowered pH and emotional triggers
136
What are some examples of emotional triggers caused by the gastric phase of gastric juice secretion?
some examples of emotional triggers resulting from the gastric phase are stress, fear, and anxiety
137
Describe the inhibitory phase of gastric juice secretion.
the inhibitory phase begins with a brief stimulus followed by inhibition/results
138
What stimuli triggers the intestinal phase of gastric juice secretion?
stimuli that trigger the intestinal phase are a lowered pH and when partially digested food enters the duodenum
139
What are some inhibitions/ results of the intestinal phase of gastric juice secretion?
some inhibitions are the distension of the duodenum and the presence of chyme
140
Describe the liver.
the liver is a reddish brown gland located immediately below the diaphragm on the right side
141
Describe the microscopic anatomy of the liver.
the liver is composed of hexagonal-shaped liver lobules
142
What are the functional units of the liver?
liver lobules are the functional units of the liver
143
What are hepatocytes?
hepatocytes are liver cells that are arranged in stacks within the liver and radiate outward from a central vein
144
List the functions of liver cells.
liver cells function to:
- secrete bile
- process nutrients
- use AA to make plasma proteins
- store fat-soluble vitamins
- clear toxins
145
How much bile is secreted from liver cells each day?
~900ml of bile is secreted per day
146
Liver cells convert ammonia into what?
liver cells convert ammonia into urea
147
Describe the portal triad.
the portal triad is three structures at each of the six corners in a liver lobule
148
Describe the function of the hepatic artery branch.
the hepatic artery branch supplies oxygen rich blood to the liver
149
Describe the function of the hepatic portal vein.
the hepatic portal vein functions to supply nutrient rich blood from the gastrointestinal tract to the liver
150
What is the function of bile ducts?
bile ducts function to transport bile from the liver to the duodenum
151
What are liver sinusoids?
liver sinusoids are heavily fenestrated pockets between hepatocytes and plates
152
Describe the movement of nutrient rich blood through the hepatic portal system.
hepatic arteries/ veins moves blood slowly through sinusoids and empty into the central vein then hepatic veins drain liver into the inferior vena cava
152
What is the function of hepatic macrophages?
hepatic macrophages line the sinusoid walls clearing debris and old erythrocytes
153
What are bile canaliculi?
bile canaliculi are tiny canals that run between adjacent hepatocytes to the bile duct of the portal triad
154
What is the function of bile canaliculi?
bile canaliculi function to transport secreted bile
154
Describe bile.
bile is a yellow-green like alkaline fluid that functions to emulsify fats
155
What are the components of bile?
bile is composed of cholesterol, neutral fats, minerals, phospholipids, electrolytes, bile pigments, and acids
156
What is bilirubin?
bilirubin is a principle bile pigment derived from the decomposition of hemoglobin
157
What are bile salts?
bile salts are steroids synthesized from cholesterol that aid in fat digestion and absorption
158
Define enterohepatic circulation.
enterohepatic circulation is the process of conserving bile salts
159
What is process of enterohepatic circulation?
enterohepatic circulation is the reabsorption of bile salts in the ileum to the liver and its incorporation into new bile
160
Describe the usages of bile salts.
95% of bile salts are recycled and the other 5% excreted in feces
161
Describe what occurs with the hepatopancreatic sphincter between meals.
between meals, the hepatopancreatic sphincter closes and prevents bile from entering the small intestine
162
Describe the anatomy of the gallbladder.
the gallbladder is a thin-walled green muscular sac on the underside of the liver
163
What is the function of the gallbladder?
the gallbladder functions to store and concentrate bile
164
What are gallstones?
gallstones are hard masses in the gallbladder or bile ducts
165
What are the causes of gallstones?
gallstones are caused by too few bile salts/ to much cholesterol that allows cholesterols to crystalize
166
Define jaundice.
jaundice is the yellowing of the skin
167
What are the causes of jaundice?
jaundice is caused by bilirubin accumulation and poor fat digestion caused by little bile entering the small intestine
168
Describe the anatomical position of the pancreas.
the pancreas is a spongy gland posterior to the greater curvature of the stomach
169
How much pancreatic juice is secreted per day?
~1,500ml of pancreatic juice is secreted per day
170
Pancreatic juice is secreted into what?
pancreatic juice is secreted into the pancreatic duct and eventually joins the bile duct to enter the small intestine
171
Describe pancreatic juice.
pancreatic juice is an alkaline mixture containing enzymes that digest starches, fats, and proteins
172
Which component of pancreatic juice breaks down starches?
pancreatic amylase breaks down starches
173
Which component of pancreatic juice breaks down lipids?
pancreatic lipase breaks down fats
174
Which component of pancreatic juice breaks down proteins?
trypsinogen breaks down proteins
175
Bile and pancreatic juice are secreted in response to what?
bile and pancreatic juice are secreted in response to hormones and parasympathetic stimulation
176
What is the function of the small intestine?
the small intestine functions to conduct nearly all chemical digestion and nutrient absorption
177
Describe the length and diameter of the small intestine.
the small intestine is 6-7 meters long is ~1 inch in length
178
Describe the surface area of the small intestine.
the small intestine is highly folded causing an increased surface area
179
What is the result of the circular folds in the small intestine?
the circular folds in the small intestine result in the flow of chyme in a spiral path along the small intestine slowing its progression and promote mixing and absorption
180
Which portions of the small intestine have circular folds?
the duodenum and jejunum have circular folds
181
Describe the anatomical location of the small intestine.
the small intestine is a coiled mass filling most of the abdominal cavity inferior to the stomach and liver
182
What are the three regions of the small intestine?
the three regions of the small intestine are the duodenum, jejunum, and ileum
182
Describe the duodenum.
the duodenum is the first 10cm of the small intestine from the pyloric valve
183
What is the function of the duodenum?
the duodenum functions to receive chyme, pancreatic juice, and bile
184
What is the ileocecal junction?
the ileocecal junction is the end of the ileum that joins the first part of the large intestine
184
Describe the anatomy of the jejunum.
the jejunum is the next 8ft of the small intestine after the duodenum
185
List the first two processes that occur once food has entered the duodenum.
the first two processes are the neutralization of stomach acids and the emulsification of fats by bile acids
185
List the second two processes that occur once food has entered the duodenum.
the second to process are the inactivation of pepsin and the overtaking of pancreatic enzymes in the digestion process
186
Describe the anatomy of the ileum.
the ileum is the next 12ft of the small intestine after the jejunum
187
Describe the function of the ileocecal valve.
the ileocecal valve functions to prevent feces back into the small intestine
188
Describe the microscopic anatomy of the small intestinal walls.
the walls of the small intestine are fuzzy due to villi that make up the brush border
189
Describe the contents of villus.
villus contains columnar and mucus-secreting goblet epithelial cells
190
Describe the contents of villus cores.
villus cores contains an arteriole, capillary network, a venule, and lymphatic system capillary (lacteal)
191
What is the function of the lacteals located in the villus core?
lacteals located in the villus core function to absorb fats
191
What is the function of the capillaries located in the villus core?
capillaries located in the villus core function to absorb nutrients
192
Describe the function of the brush border in the small intestine.
the brush border functions to increase the absorptive surface area of the small intestine
193
The brush border contains which enzymes that aid in the absorptive process.
the brush border contains enzyme integral proteins
194
What is the function of the duodenal (Brunner) glands?
the duodenal glands secrete bicarbonate-rich mucus neutralizing stomach acids and protecting the intestinal walls
195
What are the functions of lymphocytes in the small intestine?
lymphocytes in the small intestine function to intercept pathogens before they enter the bloodstream
196
What is the function of Peyer's Patches in the small intestine?
peyer's patches in the small intestine function to prevent bacteria in the distal end of the small intestine from entering the bloodstream
197
What are Peyer's Patches?
peyer's patches are mucosa-associated lymphoid tissue (MALT)
198
What are intestinal cypts?
intestinal crypts are tubular glands located on the floor of the small intestine between the bases of the villi
199
What is the function of intestinal crypts?
intestinal crypts function to secrete 1-2L of intestinal juice per day
200
What are the contents of intestinal juice?
intestinal juice contains water, mucous, and some enzymes
201
Describe segmentation.
segmentation is the circular constriction of the small intestine that cuts, churns, and mixes chyme
201
List the three functions of the small intestine.
the small intestine functions to:
- mix chyme with intestinal juice, bile, and pancreatic juice in order to neutralize acid and absorb nutrients-
- churn chyme so it can be absorbed and digested
- move residue towards the large intestine
202
Describe peristalsis.
peristalsis is the succession of contractile waves that move undigested residue down the small intestine
203
Which enzyme digests carbohydrates?
carbohydrates are digested by amylase
204
List the forms that carbohydrates/ starch take during its digestion process.
starch -> oligosaccharides -> disaccharides (maltose) -> glucose
205
Which form of carbohydrates is absorbed into the bloodstream?
glucose is absorbed into the bloodstream
206
What is the function of salivary amylase?
salivary amylase hydrolyses starches and converts them to oligosaccharides
207
In what conditions is salivary amylase activated?
salivary amylase is activated in the mouth at a pH of 6.8-7.0
208
In what conditions is salivary amylase inactivated?
salivary amylase is inactivated in the stomach at a pH of <4.5
209
What percentage of dietary starch is digested in the stomach?
50% of starch is digested in the stomach before entering the small intestine
209
When does carbohydrate/ starch digestion resume after it leaves the stomach?
starch digestion is resumed in the small intestine when chyme mixes with pancreatic amylase
210
Starch is completely converted into what during its digestion process?
starch is completely converted into oligosaccharides and maltose during digestion
211
What signifies the completion of digestion for starches?
digestion is completed once chyme contacts brush border enzymes
212
What are some examples of brush border enzymes that help digest starches?
some examples of brush border enzymes are dextranase, maltase, and glucoamylase
213
Dietary saccharides sucrose and lactose are digested by which brush border enzymes?
sucrose and lactose are digested by enzymes sucrase and lactase
214
What is the result of sucrose and lactose digestion?
sucrose and lactose digestion produce glucose and fructose and are immediately absorbed
215
True or False: glucose and fructose are polysaccharides.
False: glucose and fructose are monosaccharides
216
What is the cause of lactose intolerance?
lactose intolerance is caused by and absence of lactase to break down lactose; fermentation occurs
217
Describe how starch is absorbed.
~80% of glucose is absorbed via the sodium glucose transport protein (facilitated diffusion)
218
Proteins are digested by which enzyme?
proteins are digested by proteases
219
True of False: the mouth has an abundance of proteases.
False; proteases are absent in saliva
220
Where are proteases activated?
proteases are activated in the stomach
221
Protease combines with HCl- to form what?
protease combine with HCl- to form pepsin
222
What is the function of pepsin?
pepsin is an enzyme that functions to break down ~10-15% of dietary proteins in the stomach
223
Where is pepsin inactivated?
pepsin is inactivated in the duodenum and combined with pancreatic juice
224
What is the function of pancreatic enzymes trypsin and chymotrypsin?
trypsin and chymotrypsin take over protein digestion by breaking down polypeptides forming smaller oligopeptides
225
How are oligopeptides broken down?
oligopeptides are taken apart 1 AA at a time by 3 brush border enzymes
226
What are the three brush border enzymes that break down oligopeptides?
the brush border enzymes that break down oligopeptides are carboxypeptidase, aminopeptidase, and dipeptidase
227
Amino acids are similar to what molecule? Why?
amino acids are similar to monosaccharides because they use facilitated diffusion with sodium
228
Lipids are digested by which enzyme?
lipids are digested by lipases
229
True or False: lipid digestion is the hardest form of digestion.
True; lipid digestion is the hardest form of digestion
230
Where is lingual lipase secreted?
lingual lipase is secreted by salivary glands of the tongue
231
Where is lingual lipase activated?
lingual lipase is activated by stomach acid
232
What percentage of fat in the stomach is digested by lingual lipase?
10% of stomach fat is digested by lingual lipase
233
Where does most lipid digestion occur?
most of lipid digestion occurs in the small intestine due to pancreatic lipase and bile
234
How long does it take for fat in an average meal to be digested in the small intestine?
it takes ~1-2 minutes for fat to be digested in the small intestine
235
Describe the process of lipid absorption.
chyme enters the duodenum -> fat is broken down into emulsification droplets by lecithin and bile acids
236
True or False: long chain fatty acids are too big to be absorbed?
True; long chain fatty acids are too big to be absorbed into the bloodstream
237
Describe the absorption process of long chain fatty acids.
triglycerides form two fatty acids and a monoglyceride -> molecules are coated in bile acid and form micelles -> micelles break apart molecules to allow diffusion across the membrane
238
What are the functions of intestinal cells in reference to lipids?
intestinal cells function to absorb lipids from micelles, resynthesize triglycerides, and turn phospholipids into protein-coated chylomicrons
239
packaged chylomicrons are released by what?
packaged chylomicrons are released by exocytosis and enter the lacteal of the villus
239
What is the function of the Golgi complex?
the golgi complex functions to package chylomicrons in -to secretory vessels
240
Absorbed fatty acids enter the blood stream where?
absorbed fatty acids enter the blood stream at the left subclavian vein through the thoracic duct
241
How long does it take for short/ medium fatty acid chains to be absorbed?
short/ medium chains are immediately absorbed into blood capillaries
242
Describe the form vitamins take during their absorption.
vitamin are absorbed unchanged in the small intestine
243
Are mineral absorbed into the bloodstream?
yes, minerals are absorbed along the length of the small intestine
244
Where is water absorbed?
9L/day of water is absorbed in the small intestine and 0.8L/day is absorbed in the large intestine
244
What causes diarrhea?
diarrhea is caused by fast moving fecal matter and low amounts of water being absorbed in the large intestine
245
What causes constipation?
constipation is caused when fecal matter is moving too slow and too much water is reabsorbed
246
Describe the anatomical structure of the large intestine.
the large intestine is about 5ft long and 2.5 inches wide
247
Describe the mucosal lining of the large intestine.
the large intestine has no circular folds or villi
248
How much absorption takes place in the large intestine?
very little absorption takes place in the large intestine
249
Where does the large intestine begin?
the large intestine begins at the cecum
250
What is the cecum?
the cecum is a pouch in the lower right abdominal area that initiates the large intestine
251
Describe the appendix.
the appendix is a 2-7cm long tube attached to the lower end of the cecum
251
What is the function of the appendix?
the appendix functions to store lymphocytes and immunity cells
252
What is the colon?
the colon part of the large intestine between the ileocecal junction and anal canal
253
What are the four regions of the colon?
the four regions of the colon are the ascending, transverse, descending, and sigmoid
254
What is the rectum?
the rectum is the straight portion of the large intestine after the sigmoid colon
255
What is the anal canal?
the anal canal is the final 3cm of the large intestine that ends at the anus
256
What are the bacteria that populate the large intestine called?
the large intestine is populated with bacteria called bacterial flora
256
How much does the average person expel intestinal gas (fart)?
the average person farts ~500ml a day
257
What are the functions of bacterial flora?
bacterial flora ferment cellulose/ other undigested nutrients and synthesizes vitamins
258
What is intestinal gas (fart)?
intestinal gas is typically swallowed air that has worked its way through the digestive tract
259
How long does it take for the large intestine to create feces?
it takes 12-24 hours for the large intestine to form feces
260
The large intestine is reabsorbs what from residue?
the large intestine reabsorbs some water and electrolytes from residue
261
What are haustral contractions?
haustral contractions are slow segmenting movements in the large intestine
262
Describe the movements of mass/ feces in the large intestine.
the movement of mass in the large intestine is long, slow-moving, but powerful contractile waves over large areas of the colon
262
How long do haustral contractions last?
haustral contraction one minute every 30 seconds
263
How often do mass movements occur?
mass movements occur 3-4 times each day typically after eating
264
What are the components of feces?
feces is 75% water and 25% solids
265
List the solids that make up 25% of feces.
solids that make up feces are:
- bacteria
- undigested fiber
- some protein
- old cells
- mucus
- digestive secretions
266
Define defecation.
defecation is the process of peristaltic waves driving feces downwards and relaxes to anal sphincter to dispel feces
