chapter 24: digestive system Flashcards
1
Q
what is the collection of neurons in the peripheral nervous system that can control GI activity independent of the
CNS?
A
enteric nervous system
2
Q
abdominal organs that are supported by mesenteries are called what organs whereas those that are anchored to the body wall are called which organs?
A
peritoneal & retropertioneal
3
Q
what is the mesentery fold that supports the
intestine?
A
greater omentum
4
Q
all venous return from the intestine enters the what for
circulation to be delivered to the liver?
A
hepatic portal
5
Q
the GI epithelium is attached to an areolar connective tissue layer called the what?
A
lamina propria
6
Q
what layer is located between the submucosa and the serosa (adventitia) & is used for peristalsis?
A
muscularis externa
7
Q
the majority of saliva is produced by what salivary gland?
A
submandibular
8
Q
what innveration of the salivary glands will result in less secretion?
A
sympathetic
9
Q
the cells that produce and maintain dentin are what cells?
A
odontoblasts
10
Q
the chisel shaped teeth at the front of the mouth are what?
A
incisors
11
Q
the space at the back of the mouth is called the what?
A
pharynx (oropharynx)
12
Q
what is the circular muscle thickening that constricts the esophagus at the stomach to prevent stomach contents from entering esophagus?
A
gastroesophageal sphincter/cardiac sphincter
13
Q
what is another word for deglutition?
A
swallowing
14
Q
the most superior part of the stomach that contacts the diaphragm is what?
A
fundus
15
Q
the pyloric sphincter controls movement of material from the stomach to what?
A
duodenum
16
Q
the accordion like folds of mucosa & submucosa in the stomach are what?
A
rugae
17
Q
what cells produce intrinsic factor and HCl?
A
parietal cells
18
Q
name the substance produced in the stomach of infants to curdle milk?
A
rennin
19
Q
D cells of the stomach produce what functions to what stomach activity?
A
somatostatin & inhibit
20
Q
an infection by Helicobacter pylori is the most common cause of what?
A
peptic ulcer
21
Q
during the intestinal phase, what effect will lipids, carbohydrates, and peptides
have on stomach activity?
A
decrease & inhibit
22
Q
what hormone is produced by either G cells of the stomach or the enteroendocrine cells of the small intestine functions to stimulate all stomach
activity?
A
gastrin
23
Q
most of the digestion and absorption of food occurs in the what portion
of the small intestine?
A
jejunum
24
Q
the finger-like extensions of the mucosa layer of the small intestine are the what?
A
villi
25
collectively the velvet-like collection of microvilli on the surface of the epithelium
of the small intestine is called the what?
brush border
26
what cells are the mucin-secreting cells among the columnar epithelial cells of the intestine?
goblet
27
the Peyer’s patches of the ileum are what?
lymphoid follicles/nodules
28
what reflex stimulates motility and secretion along the length of the small intestine?
gastroenteric
29
why does the soft palate rise during the emesis reflex?
to prevent vomit from shooting out your nose
30
what cells of the pancreas produce the enzymes & buffers?
acinar
31
pancreatic islets produce insulin and what to control blood sugar?
glucagon
32
trypsinogen is activated/converted into trypsin by the brush border enzyme what?
enterokinase
33
the liver has four lobes: right, left, caudate and which other?
quadrate
34
a portal triad consists of a hepatic artery, a hepatic portal vein, and a what duct?
bile duct
35
entry of materials into the duodenum from the common bile duct is controlled by what sphincter?
hepatopancreatic
36
the function of bile is to buffer chyme & what lipids?
emulsify
37
what's the disease condition of chronic inflammation of the liver that results in the replacement of hepatocytes with collagen & adipose?
cirrhosis
38
cholecystitis is inflammation of what organ?
gallbladder
39
what's released from the duodenum when chyme is acidic, stimulates the release of bile and buffers and reduces stomach activity?
secretin
40
the proximal end of the large intestine where the appendix is located is called
the what?
cecum
41
the color, odor & gas associated with feces all come from the activity of what?
bacteria
42
what contractions are the segmenting contractions of the colon that facilitate water absorption?
haustral
43
someone who is lactose intolerant does not produce what enzyme?
lactase
44
what functions to hydrolyze polysaccharides into di- & tri- saccharides?
amylase
45
water is absorbed from the intestine into the blood by what?
osmosis
46
digestive system
-responsible for providing raw materials to support life
-food molecules catabolized for energy & building blocks to supply anabolic reactions
47
ingestion (function of digestive system)
take in food
48
propulsion (function of digestive system)
move food through GI swallowing & peristalsis
49
mechanical processing (function of digestive system)
chewing, churning, mixing & compacting
50
chemical digestion (function of digestive system)
enzymatic breakdown of large molecules into building blocks
51
secretion (function of digestive system)
enzymes, acids, mucus, water & cell wastes
52
absorption (function of digestive system)
move organic molecules, electrolytes, vitamins, water from gut to interstitial fluid, lymph & blood
53
excretion (function of digestive system)
cell waste, secretions, indigestible foodstuffs ejected from body
-defecation of feces
54
digestive activity controlled by chemical or mechincal stimuli:
-stretching
-osmolarity
-pH
-substrate concentration
-end product cencentration
55
enteric nervous system (neural control)
nerve plexus of the gut
56
neural control of gut
-ENS
-short reflexes: ENS only "gut brain"
-long reflexes: involve imput from ANS (CNS)
57
hormonal control of gut
18 hormones produced by enteroendocrine cells in GI: target may be same organ or different organ (specific hormones for specific foods)
58
local mechanisms of gut
prostaglandins & histamine can trigger localized secretion based on contents of GI tract
59
location of the gut:
-most in peritoneal cavity in abdomen
-cavity: lined with parietal peritoneum
-organs: covered with visceral peritoneum
-both layers secrete peritoneal fluid to reduce friction during movement
60
ascites
excess peritoneal fluid -> swelling of abdomen, distortion of organs: can cause heart, indigestion, back pain
61
peritonitis
inflammation of peritoneum from damage or infection: can cause pain & organ failure
62
mesenteries
sheets of peritoneum that support the bulk of the digestive system
-mesenteries also hold blood vessels, lymphatic vessels, nerves & adipose (protection, insulation, energy reserve)
63
peritoneal organs
supported by mesenteries (sheets of peritoneum)
64
retroperitoneal organs
anchored to body wall
65
lesser omentum (special mesentery folds)
holds stomach
66
falciform ligament (special mesentery folds)
holds liver
67
greater omentum (special mesentery folds)
holds intestine
68
blood supply of the gut
-digestive organs receive 1/4 CO
-this can increase following a meal
-all venous return from GI enter hepatic portal circulation (liver)
-liver processes or absorbs nutrients from gut before blood returns to circulation
69
mucosa (mucous membrane)
-function to secrete mucus, digestive enzymes & hormones, to absorb and products of digestion and provide protection from pathogens
a. epithelium
b. lamina propria
c. muscularis mucosae
70
epithelium (mucosa membrane layer)
stratified squamous: oral cavity, pharynx, esophagus, anus
simple columnar: stomach, intestine: has goblet cells (mucus) & enteroendocrine cells (hormones)
71
lamina propria (mucous membrane)
loose areolar CT tissue with blood vessels, lymphatic vessels, nerves, mucous glands & lymphoid tissue (extending from submucosa): MALT or tonsils
72
muscularis mucosae (mucous membrane)
-band of smooth & elastic fibers: one layer circumferential one longitudinal
-functions to change shape of plicae & villi
73
villi (mucous membrane)
finger-like projections of mucosa layer & increases surface area
74
plicae (mucous membrane-small intestine)
folds of mucosa & submucosa & increase surface area
75
rugae (mucous membrane-stomach)
pleats of mucosa & submucosa & expand to accommodate volume
76
submucosa
-dense irregular CT, contains large vessels, glands to secrete digestive enzymes & mucus
-houses submucosal nerve plexus
77
submucosal nerve plexus (submucosa)
autonomic nervous system control of glands & smooth muscle of mucosa
78
muscularis externa
-consists of inner circular layer & outer longitudinal layer of smooth muscle for mixing & moving lumenal contents
-circular layer(thick) creates sphincters at junctions to prevent backflow
-contains myenteric nerve plexus
79
myenteric nerve plexus (muscularis externa)
controls GI mobility via local reflexes arcs & ANS stimulation
80
serosa
visceral peritoneum: areolar CT plus mesothelium, covers all abdominal/peritoneal GI tract organs
81
adventitia
dense irregular CT, anchors organs to surrounding tissues, covers oral cavity, pharynx, esophagus & rectum
82
movements in the gut:
-coordinated by short local reflex arcs of ENS
-most ANS to gut is parasympathetic
83
ENS innervated by ANS allowing extrinsic control of digestive activity:
-parasympathetic = increased muscle activity & secretion -sympathetic = decreased muscle activity & secretion
84
peristalsis (movement in gut)
waves of contraction, move food bolus along length of gut
85
segmentation (movement in gut)
single point contraction, chop up bolus, allow enzymes to access inner regions
86
oral cavity/mouth/buccal cavity
-connects environment to pharynx
-lined with stratified squamous epithelium
-walls = muscular cheeks
-floor contains tongue
-hard & soft palate
87
hard & soft palates (roof of mouth)
-hard palate: anterior
-soft palate: posterior -> close off nasopharynx during swallowing
88
function of the oral cavity/mouth/buccal cavity
1. analyze food (taste buds)
2. mechanically process food (chew)
3. lubricate food (saliva)
4. digest starches (amylase)
89
tongue (accessory organ of mouth )
-muscular
-surface covered by papillae: provide friction & house taste buds
90
functions of the tongue
1. speech
2. manipulate food into teeth for mastication
3. compress food into bolus for swallowing
4. analyze food for texture, taste, temp
5. produce secretions
91
what are the 2 secretion made by the tongue?
a. mucin = lubrication
b. lingual lipase = start lipid digestion
92
salivary glands (accessory organs of mouth)
-produce 1-2L saliva/day
-low levels of saliva produced by parasympathetic stim. -> increased secretion (food cue) & sympathetic stim. -> decreased secretion (dry mouth)
93
saliva (salivary glands -> accessory organs of mouth)
99% water + enzymes (amylase for starch), electrolyte buffers, mucin (lubrication), antibodies & antimicrobials (lysozyme & defensins)
94
functions of saliva:
1. cleanse mouth, control oral bacteria
2. dissolve food chemicals for taste
3. moisten food for bolus formation
4. begin chemical digestion of carbohydrates
5. buffer oral pH
95
parotid salivary glands
inferior to zygomatic arch, thick secretion, high salivary amylase (25% of saliva)
96
sublingual salivary glands
inferior to tongue, watery secretion, high in buffers (5% of saliva)
97
submandibular salivary glands
posterior floor of mouth, buffers, mucin, amylase (70% of saliva)
98
functions of teeth (accessory organ of mouth)
mastication, mechanical digestion
99
pulp cavity (structure of teeth)
soft center, blood vessels & nerved in CT called pulp
100
dentin (structure of teeth)
bone-like, surrounds pulp cavity, contains odontoblasts which secret & maintain dentin
101
crown (external surface of teeth)
exposed region, covered in enamel composed of hydroxyapatite (calcium salt crystals)(like bome but no collagen)
-cells that produce enamel degenerate after eruption (no repair)
102
root (external surface of teeth)
embedded region, covered in cementum, attached to periodontal ligaments: hold tooth in alveolus of jaw
103
incisors (type of tooth)
chisel-shaped, single root, 8 total, used for cutting
104
cuspids/canines/eyeteeth (type of tooth)
conical-shaped, single root, 4 total, used for tearing & piercing
105
bicuspids/premolars (type of tooth)
2 ridges/cusps, 1 or 2 roots, 8 total, used for crushing, mashing & grinding
106
molars (type of tooth)
4-5 cusps, 3 or more roots, 12 total, used for crushing, grinding
3rd molars = wisdom teeth
107
deciduous/milk teeth
under age 12 -> 20 teeth
-replaced by age 21 -> 32 permanent teeth
108
impacted tooth
fails to erupt, remians in jaw causing pain
-surgical fix
109
dental caries
demineralization of enamel & dentin by bacteria exposes nerve, pain
110
periodontal disease
infection of gingival, immune response erodes bone around teeth, teeth fall out
111
pharynx
-oropharynx (back of mouth)
-laryngopharynx (superior to voice box)
-connects oral cavity to esophagus
-shared space with respiratory system
-stratified squamous epithelium
-lamina propria has tonsils & mucus glands
-skeletal muscles surround for swallowing
112
esophagus
-muscular tube connects pharynx to stomach
-25cm long
-passes through diaphragm to abdomen
-at rest, superior & inferior regions constricted to keep air out & stomach contents in
113
gastroesophageal sphincter
inferior constriction point acts as a valve that keeps food & stomach acid in the stomach and prevents the stomach's contents from regurgitating back into the esophagus.
114
gastroesophageal reflux disease (GERD)
-"heart burn"
-gastric juice regurgitates into esophagus causing erosion
115
features of esophagus:
1. stratified squamous
2. large folds in mucosa & submucosa to keep lumen closed during rest
3. esophageal glands in submucosa secrete mucus to reduce friction
4. upper 2/3 of muscularis externa contains skeletal muscle
5. anchored by adventitia
116
deglutition
-swallowing
-pharynx & esophagus function in food propulsion from mouth to stomach
117
buccal phase - voluntary (deglutition)
-soft palate raised to protect nasopharynx
-bolus pushed against hard palate
-bolus pushed into oropharynx
118
pharyngeal phase -Involuntary reflex (deglutition)
-epiglottis blocks entry to trachea
-contractions move bolus past glottis
119
esophageal phase -involuntary reflex (deglutition)
-peristaltic waves push bolus toward stomach
-gastroesophageal sphincter opens
-bolus enters stomach
120
stomach functions:
1. store digested food (~1L)
2. mechanical breakdown of food (churning)
3. chemical breakdown of food (denatures & digests proteins)
4. produce intrinsic factor for VitB12 uptake
5. holds chyme
121
chyme
acidic mixture of enzymes & food
122
cardia (region of the stomach)
-where esophagus connects via gastroesophageal sphincter
-gastric glands produce mucus to protect esophagus
123
fundus (region stomach)
superior region, contact diaphragm
124
body (region of stomach)
-majority of stomach
-hold chyme
-gastric glands secrete enzymes & acids for digestion
125
pylorus (region of stomach)
-inferior region
-connects to duodenum via pyloric sphincter: regulates chyme entry into duodenum
-gastric glands secrete hormones to stimulate gastric activity
126
features of the stomach
-muscualris externa has 3 layers (oblique) to assist mixing chyme
-when empty mucosa & submucosa folded into rugae
-simple columnar epithelium with goblet cells(mucus)
-mucosa perforated by gastric pits, which connect gastric glands to laminate propria
-stem cells replaced every 3-6 days
127
gastric glands
-produce 1-3L gastric juice/day: secretion vary per regiom
1. cardia
2. fundus & body
3.pyloric
128
cardia gastric glands
mucus
129
fundus & body gastric glands
digestive enzymes & acid
- 2 types: parietal & chief
130
parietal cell (fundus & body gastric cell)
-secrete
1. intrinsic factor (VitB12)
2. H+ & Cl- ions combine to make HCl in stomach
131
pepsinogen (chief cell -> fundus & body gastric cell)
converted to pepsin by acid in stomach: hydrolyzes proteins
132
rennin (chief cell -> fundus & body gastric cell)
infants only, curdles milk protein to aid digestion
133
acid production important to gastric function:
1. kill microbes
2. denature proteins
3. breakdown plant cell walls & animal CT
4. activate pepsin
134
pyloric gastric glands
mucus & hormones
-2 important hormone-producing cells: G cells & D cells
135
G cells (pyloric gastric gland)
-produce gastrin
-stimulates secretion by parietal & chief cells
-promotes contraction of gastric wall
secreted in response to food or parasympathetic stimulation
136
D cells (pyloric gastric gland)
-produce somatostatin
-inhibits release of gastrin (thus inhibits gastric activity)
-secreted in response to sympathetic stimulation
137
gastritis
inflammation of gastric mucosa caused by drugs, stress, infection: chronic can lead to ulcer
138
peptic ulcer
erosion of stomach lining, caused by too much acid, not enough mucus, or, most commonly, helicobacter pylori (bacteria)
139
regulation of gastric activity
-secretion & mobility controlled by 3 factors:
1. innervation from CNS (ANS)
2. reflexes of ENS
3. hormones
-mechanism relies on stimuli from three
140
cephalic phase (regulation of gastric activity)
-CNS
-prepares stomach for food
-triggered by seeing, smelling, or thinking of food
-lasts a few minutes
141
neural response of cephalic phase (regulation of gastric activity)
parasympathetic ANS triggers increase in all gastric secretions (mucus, enzymes, acid) & triggers G cells to release gastrin
142
gastric phase (regulation of gastric activity)
-initiates stomach digestive activities
-triggered by food entering stomach (stimuli = dissension, peptides low, low acidity)
-lasts 3-4 hours
143
neural response of gastric phase (regulation of gastric activity)
stretch receptors activate ENS reflexes & parasympathetic ANS innervation; both stimulate secretions from parietal cells (acid), chief cells (pepsin) & G cells (gastrin)
144
hormonal response of gastric phase (regulation of gastric activity)
triggered by neural response, peptides & increased pH, G cells release gastrin, which triggers secretion by parietal & chief cells and gastric mobility
145
local response of gastric phase (regulation of gastric activity)
triggered by distortion, mast cells release histamine, which stimulates parietal cells
146
what sympathetic stimulation show down down in gastric secretion?
shuts down gastric secretion via somatostatin from D cells
147
greatest acid production via 3 -fold stimulation of parietal cells:
1. Ach from ENS & parasympathetic ANS
2. gastrin from G cells
3. histamine from mast cells
148
intestinal phase (regulation of gastric activity)
-controls chyme entry into duodenum
-triggered by chyme entering duodenum
-last many hours
-involves excitatory & inhibitory control of gastric activity depending on chyme composition
149
neural response of intestinal phase (regulation of gastric activity)
stretch receptors trigger enterogastric reflex, which turns off ENS & parasympathetic stimulation of G cells and stimulates sympathetic stimulation of pyloric sphincter
150
hormone response of intestinal phase for lipids, carbohydrates & peptides (regulation of gastric activity)
cholecystokinin & gastric inhibitory peptide
-inhibit gastric secretion & motility (stimulates pancreas + gallbladder secretion)
151
hormone response of intestinal phase for proteins (regulation of gastric activity)
intestinal gastrin
-stimulates parietal & chief cells, stimulates gastric mobility
151
hormone response of intestinal phase for low pH (regulation of gastric activity)
secretin
-inhibits gastric secretion (stimulates pancreas + liver secretions)
152
what are 2 things that are absorbed in the stomach?
drugs & alcohol
153
food doesn't remain in stomach for more than 4hrs but total depends on chemical makeup of food:
-carbohydrate-rich = passes quickly
-fatty foods can cause chyme to remain in stomach 6+ hrs
154
small intestine
-major division organ
-chemical digestion completed
-90% of nutrients absrobed
-20ft long, 3 major subdivisions
155
duodenum (small intestine)
-first 10 inches
-retroperitoneal
-receives chyme from stomach through pyloric sphincter
-receives digestive secretions from pancreas & liver through duodenal ampula controlled by hepatopancreatic sphincter
-mixing pot
156
jejunum (small intestine)
-8ft
-peritoneal
-majority of chemical digestion & nutrient absorption occur here
-has the most plicae & villi
157
ileum (small intestine)
-12ft
-peritoneal
-mucosa rich in lymphoid tissue
-connect cecum at ileocecal valve
158
plicae (small intestine)
mucosa & submucosa folded into circular plicae that cause chyme to serial slowly
159
villi (small intestine)
plicae covered with finder-like projections of mucosa called intestinal villi, base of each has crypt/intestinal gland
160
microvilli (small intestine)
simple columnar epithelial cells have microvilli on apical surfaces: membrane collectively called brush border of intestine
161
histology of small intestine
-4 layers adapted for absorption
-plicae + villi + microvilli = 3.6 ft
-lamina propria of each villus contains capillaries that carry small nutrient molecules to liver via hepatic portal vein
-contain lacteals
162
lacteal
the special lymphatic capillary collects larger molecules that can't enter capillaries (lipid-protein complexes)
163
contraction of muscularis mucosae:
-move villi to expose surface to new chyme
-squeeze lacteals to move lymph
164
goblet cells
between columnar epithelium cells
-secrete mucus (mucin)
165
intestinal glands of small intestine
variety of cells in crypt, located in lamina propria at base of each villus
-produce: intestinal juice, lysozyme, hormones, epithelium cells
166
intestinal juice (intestinal gland product of small intestines)
1-2L/day, watery mucus, aids solubilization & absorption of nutrients
167
lysozyme (intestinal gland product of small intestine)
from Paneth cells, lyse bacteria
168
epithelial cells (intestinal gland product of small intestine)
-stem cells in glands
-new cells created, migrate up villus, shed at tip, complete turnover 3-6 days
-shed cells carry digestive enzymes in plasma membrane that function in lumen
169
brush border enzyme
complete digestion of carbohydrates & proteins
-epithelial cell
170
Peyer's Patches
aggregated lymphoid nodules in ileum for immune defense
171
when does secretion from intestinal glands begin in the small intestine?
-before chyme enters due to parasympathetic stimulation
-when chyme present, stretch receptors & enterocrinin stimulate secretions of mucus, hormones & juice
172
myenteric reflexes (ENS) (small intestine movements)
peristalsis to move chyme slowly through small intestine
173
gastroenteric reflex (parasympathetic reflexes -> small intestine movement)
stimulates motility & secretion along whole small intestine
174
gastroileal reflex (parasympathetic reflexes -> small intestine movement)
relaxes ileocecal valve, materials pass fro ileum to cecum (large intestine)
175
emesis/vomiting reflex
-controlled by emetic center of medulla oblongata
176
emesis/vomiting reflex process
1, pyloric sphincter relaxes, contents of duodenum & upper jejunum discharged in stomach
2. salivary secretion enhanced (buffer stomach acid)
3. soft palate rises to close off nasopharynx
4. diaphragm & abdominal wall muscle contract, stomach contents regurgitated
177
pancreas
-retroperitoneal
-inferior to stomach
-exocrine & endocrine
-pancreatic juice released into pancreatic duct & joins with common bile duct
-enter duodenum at duodenal ampula & controlled by hepatopancreatic sphincter
178
pancreatic islets
-endocrine, 1%
-cells secrete insulin & glucagon to control blood sugar
179
pancreatic acini
-exocrine, majority
-acinar cells (simple cuboidal) produce digestive enzymes & buffers: pancreatic juices
180
pancreatic juice
~1.5L/day in response to parasympathetic & hormonal control
-water + proenzymes + electrolytes (buffer)
181
pancreatic enzymes
~70% secreted as proenzymes, activated in gut
-all proteolytic enzymes are secreted inactive must be activated in gut (prevent autolysis)
182
enterokinase
-brush border enzyme
-activates pancreatic trypsinogen -> trypsin
-trypsin activates all pancreatic proteolytic pro-enzymes via cleavage
183
pancreatic alpha-amylase (pancreatic enzyme)
hydrolyzes starch
184
pancreatic lipase (pancreatic enzyme)
hydrolyzes lipids & fatty acids
185
nucleases (pancreatic enzyme)
hydrolyze nucleic acids (RNA, DNA)
186
proteolytic enzymes (pancreatic enzyme)
-majority
-each digest-specific peptide bond
- 2 main classes: proteases & peptidases
187
proteases (proteolytic enzymes ->pancreatic enzyme)
hydrolyzes large proteins into peptides
188
peptidases (proteolytic enzymes ->pancreatic enzyme)
hydrolyze peptide chains into amino acids
189
pancreatitis
inflammation of the pancreas, ducts blocked -> injury to acinar cells
-necrotic cells release lysosome enzymes -> activate pro-enzymes -> autolysis
190
diabetes mellitus
destruction of Islet cells due to pancreatitis or autoimmune attack results in loss of regulation of blood sugar levels
191
liver
-right side, inferior to diaphragm
-largest visceral organ
-four lobes -> anterior separated by falciform ligament (fetal umbilical vein) & posterior: tiny caudate & quadrate lobe
192
lobule
hexagonal functional unit of liver
-separated by interlobular septa
-central vein in middle
-six portal triads on hexagonal corners
193
hepatic artery of liver
O2 rich blood
194
hepatic portal vein of liver
nutrient-rich blood from small intestine
195
bile duct of liver
collect bile produced by hepatocytes
196
hepatocytes
function in nutrient regulation & bile production, arranged in rows around central vein, sinusoids between rows
197
blood flow in lobule:
-blood from arteries & veins of triads flow through sinusoids
-allows molecule exchange with hepatocytes
-blood flows out through central vein
198
Kupffer cells
-fixed macrophages in sinusoids
1. remove pathogen, cell debris, damages eyrhocytes
2. remove & store iron
3. remove & store lipids
4. remove & store heavy metals
199
bile flow
-bile secreted by hepatocytes
-flows through bile canaliculi between cells
-canaliculi -> bile duct of triads -> merge into common hepatic duct
-hepatic duct exits liver, joins cystic duct from gallbladder creating common bile duct
-common bile duct connects to duodenum at duodenal ampula
200
metabolic regulation (liver/hepatocyte function)
-hepatocytes regulate blood nutrient levels
-nutrient-rich blood from GI goes to liver so excess can be removed & deficits can be corrected
201
carbohydrate metabolism by hepatocytes
-too much glucose -> hepatocytes store glucose as glycogen
-too little -> hepatocytes break down glycogen or perform glucogenesis
202
what do hepatocytes carry out besides carbohydrate metabolism?
lipid & amino acid metabolism, waste removal, vitamin storage, mineral storage and drug & toxin inactivation
203
hematological regulation (liver/hepatocyte function)
a. liver serves as blood reservoir
b. Kupffer cells recycle RBCs
c. Kupffer cells perform antigen presentation to lymphocytes
d. hepatocytes remove/recycle hormones & antibodies
e. hepatocytes & Kupffer cells remove, inactivate, or store toxins, drugs & heavy metals
f. hepatocytes produce plasma proteins
204
bile components:
water, bilirubin, phospholipids, electrolytes, cholesterol & bile salts
205
bile functions
a. buffer chyme (electrolytes)
b. emulsify fats: break large lipids globs into small droplets (phospholipids & bile salts
206
function of emulsification
-allows enzymes to access lipids
-promote solubilization & absorption of lipids in blood & lymph
207
digestion: bile synthesis & secretion (liver/hepatocyte function)
-bile creation
-emulsification
-circulation of bile
-secretin from duodenum promotes secretion of bile from liver
208
enterohepatic circulation of bille
bile salts absorbed in lipid droplets & recycled back to liver, not metabolized
209
hepatitis
inflammation of liver, due to viral infection, restricts blood flow to lover, six known viruses with different severity
210
cirrhosis
chronic inflammation due to severe hepatitis or alcoholism: damaged hepatocytes replaced by fibrous tissue & adipose, can cause portal hypertension -> veins swell & rupture
211
gallbladder
-anterior & inferior to liver
-functions to concentrate & store bile produced by liver
-cholecystokinin from duodenum causes release of bile by stimulating contraction of gallbladder & relaxation of hepatopancreatic sphincter
212
gall stones
crystalization of over-concentrated bile
213
cholecystitis
inflammation caused by large gall stones that block or damage the gallbladder
214
ANS (neural mechanism in coordination of secretion & absorption in small intestine)
-parasympathetic = increased digestive activity
-sympathetic = decreased digestive activity
215
ENS reflexes (neural mechanism in coordination of secretion & absorption in small intestine)
coordinate movement od material from one region to the next
216
hormonal mechanisms (coordination of secretion & absorption in small intestine)
hormones from intestinal glands of duodenum control small intestine, stomach & accessory organs to coordinate digestive activities
217
enterocrinin (hormonal mechanism in coordination of secretion & absorption in small intestine)
released when chyme enter duodenum, stimulates mucus production in duodenum
218
intestinal gastrin (hormonal mechanism in coordination of secretion & absorption in small intestine)
released when chyme contains protein, stimulates gastric activity
-"activity" = secretion & motility
219
gastric inhibitory peptide (hormonal mechanism in coordination of secretion & absorption in small intestine)
released when chyme contain lipids & carbohydrates, inhibits gastric activity
220
secretin (hormonal mechanism in coordination of secretion & absorption in small intestine)
released when chyme is acidic, stimulates the release of bile from liver & buffers from pancreas and reduces gastric activity
221
cholecystokinin (hormonal mechanism in coordination of secretion & absorption in small intestine)
released when chyme contains lipids & peptides, stimulates:
-secretion of enzymes from pancreas
-contraction of gallbladder for bile release
-relaxes hepatopancreatic sphincter to allow entry of bile & enzymes into duodenum
-inhibits gastric activity
-reduces hunger sensation (20 min post food consumption)
222
vasoactive intestinal peptide (hormonal mechanism in coordination of secretion & absorption in small intestine)
released when chyme enters duodenum, inhibits gastric secretion, stimulates intestinal secretion, dilates local capillaries for absorption
223
somatostatin (hormonal mechanism in coordination of secretion & absorption in small intestine)
released in response to sympathetic stimulation
-inhibits gastric activity
-inhibits secretion from pancreas & gallbladder
-inhibit blood flow to intestine, inhibiting absorption
224
large intestine
~5ft long
-no digestion except microbes
-water absorption important to feces: too much = diarrhea -> too little = constipation
225
functions of the large intestine
1. reabsorb any remaining water & compact feces
2. absorb vitamins & electrolytes
3. storage of feces & defecation
226
bacteria of large intestine produces vitamins:
-VitK: clotting factor
-biotin: glucose metabolism
-VitB5: steroid hormone & neurotransmitter synthesis
227
bacterial metabolism produces characteristics of feces:
-bilirubin -> urobilins & stercobilins = brown
-fermentation of organics -> ammonia, indole, H2S = odor
-fermentation of carbs -> methane, CO2 = flatus
228
histology specialization of large intestine
-mucosa has deep crypts with intestinal glands that produce mucus
-no plicae or vili
-lamina propria has large nodules
-epithelium is simple columnar with goblet cells
229
taeniae coli (large intestine)
muscularis externa made up of 3 longitudinal bands of muscle
230
haustra (large intestine)
pouches created by the contraction of taeniae coli
231
cecum (subdivision of large intestine)
-attached to ileum via ileocecal valve
-functions to begin compaction of feces
-appendix hangs off side
232
appendix (side of cecum -> large intestine)
has lymphoid nodules that are part of the MALT
233
appendicitis
blockage of appendix results in bacterial growth, causing inflammation & swelling, rupture will release bacteria into abdomen -> peritonitis -> sepsis -> death
234
colon (subdivision of large intestine)
-absorbs water, vitamins, electrolytes
-four major regions:
1. ascending colon
2. transverse colon
3. descending colon
4. sigmoid colon
235
diverticulitis
pockets form in colon wall & are site of recurrent inflammation & infection due to a lack of fiber
236
rectum (subdivision of large intestine)
-stores feces
-has 3 valves to separate feces & flatus
-exits at anal canal
-lined with stratified squamous
-defecation controlled by 2 sphincters: internal & external anal sphincters
237
internal anal sphincter
smooth muscle from muscualris externa, involuntary
238
external anal sphincter
skeletal muscle under voluntary control
239
haustral contractions (large intestinal movement)
local, slow, segmenting contraction, shift feces for water absorption
240
mass movements (large intestinal movement)
powerful peristaltic contractions, force feces toward rectum, occur few times per day, can trigger defecation reflex via stretch receptor in rectum
241
defecation reflex (large intestinal movement)
stretch receptors -> parasympathetic stimulation -> contraction of sigmoid colon & rectum and relaxation of internal anal sphincter, voluntary control of external anal sphincter controls timing of defecation
242
diarrhea
movement through large intestine too fast = too much water in feces
243
constipation
movement too slow through large intestine = too little water in feces
244
chemical digestion
-large molecules catabolized into monomers
-monomers absorbed by mucosa
-enzymatic breakdown = hydrolysis
245
carbohydrate digestion method
-amylases (saliva, pancreas) = polysaccharides-> di- & trisaccharides
-brush border enzymes (small intestine) = di- & trisaccharides -> monosaccharides
246
carbohydrate absorption method
-facilitated diffusion (w/ protein, no ATP) & cotransport of monosaccharides (2 substances at once, ATP used)
-cellulose (fiber) not digested aids in intestinal mobility
247
lactose intolerant
fail to produce lactase (brush border enzyme); undigested lactose creates osmotic gradient that causes feces to remain hydrated (diarrhea), bacteria ferment lactose, producing flatus
248
lipid digestion method
-bile salts (liver) = emulsification
-lipases (tongue, pancreas) = triglycerides -> monoglycerides & fatty acids
249
lipid absorption method
-micelles form: monoglycerides, fatty acids & bile salts
-chylomicrons exocyst into lumen
chylomicrons absorbed by lacteal
250
chylomicrons
micelles absorbed by intestinal epithelium, proteins added
251
protein digestion method
-mastication (chewing) & churning (stomach) = disrupt protein structure
-pepsin + acid (stomach) = protein -> polypeptide
-proteases + peptidases (pancreas, brush border) = polypeptide -> amino acid
252
protein absorption method
-facilitated diffusion (w/ protein, no ATP) & cotransport of amino acids (2 substances at once, ATP used)
253
nucleic acid digestion method
-nucleases (pancreas) = nucleic acid -> nucleotides
-brush border (small intestine) = nucleotides -> nitrogenous bases + sugar + phosphate ions
254
nucleic acid absorption method
activate transport (burn ATP to pump into blood) of nitrogenous bases + sugar + phosphate ions
255
water digestion method
-no digestion required -> absorption
-2L from food, 7L from secretions
256
water absorption method
-osmosis (95% in small intestine
~150ml lost in feces
257
ion digestion method
-no digestion required -> absorption
-from food or secretion
-must be regulated for homeostasis
-control osmosis & pH, needed for enzyme function
258
ion absorption method
diffusion (no ATP), cotransport & active transport (ATP required & pumped into blood)
*depends on the ion
259
vitamin digestion method
-no digestion required
-fat-soluble = A, D, E, K
-water-soluble = most B & C
-VitB12
260
vitamin absorption method
- fat-soluble = mixed with fats (travel w/lipids) in micelle -> chylomicrons
-water-soluble = diffusion
-VitB12 = bound to intrinsic factor(intestine), binds receptors, endocytose to blood (B12)
261
age-related changes
1. epithelium division rates decline -> ulcers more likely
2. smooth muscle tone decreases
-constipation(slow movement)
-diverticulitis & hemorrhoids from weak walls
-GERD from open sphincters
3. cumulative damage to teeth (wear, carries) & liver (toxin, lipid build-up)
4. increased cancer rate
