Digestive System Flashcards
1
Q
digestive system
A
responsible for providing raw materials to support life: food molecules catabolized energy and building blocks to supply anabolic reaction
2
Q
anabolism
A
uses raw materials to synthesize essential compounds
3
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anabolic processes
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cell division, repair, secretions, etc.
4
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catabolism
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decomposes substances to provide energy cells need to function
5
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catabolic reactions require two essential ingredients to break down macromolecules
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oxygen and organic molecules broken down by intracellular enzymes (ex. carbohydrates, fats and proteins)
6
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components of the alimentary canal/gastrointestinal tract (G.I.)
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oral cavity, pharynx, esophagus, stomach, small intestine, large intestine, rectum, anus
7
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accessory digestive organs
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teeth, tongue, salivary glands, liver, gallbladder, pancreas
8
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digestive tract
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gastrointestinal (GI) tract or alimentary canal
is a muscular tube
extends from oral cavity to anus
9
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7 functions of the digestive system
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ingestion, propulsion, mechanical processing, chemical digestion, secretion, absorption, excretion
10
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ingestion
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occurs when materials enter digestive tract via mouth
11
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propulsion
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move food through GI swallowing and peristalsis
12
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mechanical processing
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chewing, churning, mixing, compacting
makes materials easier to propel along digestive tract
13
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chemical digestion
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enzymatic chemical breakdown of large food molecules into small organic fragments (building blocks) for absorption by digestive epithelium
14
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secretion
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release of water, acids, enzymes, mucus, salts, and cell waste by epithelium of digestive tract and glandular organs
15
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absorption
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movement of organic substrates, electrolytes, vitamins, and water from the gut, into interstitial fluid, lymph, and blood
16
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excretion
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removal of cell waste products, secretions, indigestible foodstuffs from the body
defecation of feces
17
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digestive activity (gland secretions or lumen movement) is controlled by
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chemical or mechanical stimuli:
1. stretching
2. osmolarity (osmotic concentration)
3. pH
18
Q
osmolarity measures
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solute concentrations-> osmoles of solute particles per unit volume in secretion
substrate concentration
end product concentration
19
Q
control of digestive function
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- neural mechanisms
- hormonal mechanisms
- local mechanisms
20
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neural mechanisms
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enteric (or intrinsic) nervous system (ENS)
input from ANS (in CNS)
21
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hormonal mechanisms
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at least 18 hormones produced by enteroendocrine cells in GI: target may be same organ or distant organ
specific hormones for specific foods
22
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local mechanisms
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prostaglandins and histamine can trigger localized secretion based on contents of GI tract
23
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the lining of the digestive tract safeguards surrounding tissues against
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- corrosive effects of digestive acids and enzymes
- mechanical stresses, such as abrasion
- bacteria either ingested with food or that reside in digestive tract
24
Q
peritoneal cavity
A
most organs- in peritoneal cavity of abdomen
is located within two layers of serosa
25
cavity
lined with serosa, parietal peritoneum
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organs
covered with serosa, visceral peritoneum
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both serous membrane lining (parietal and visceral) secrete
peritoneal fluid
28
peritoneal fluid function
provides essential lubrication
allows sliding without friction or irritation
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mesenteries
sheets of peritoneum
support a bulk of the digestive system
30
peritoneal organs
supported by mesenteries
double sheets of peritoneum serous membrane
31
retroperitoneal organs
anchored to body wall
32
functions of mesenteries
connect parietal peritoneum with visceral peritoneum
provide an access route to and from the digestive tract for passage of blood vessels, nerves and lymphatic vessels
stabilize positions of attached organs
prevent intestines from becoming entangled
33
mesentery development during embryonic development
digestive tract and accessory organs are suspended in peritoneal cavity by dorsal and ventral mesentery
34
special mesentery folds
lesser omentum, falciform ligament, greater omentum
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lesser omentum
stabilizes position of stomach
provides access route for blood vessels and other structures entering or leaving liver
36
falciform ligament
helps stabilize position of liver
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greater omentum
holds intestines hanging like an apron from lateral and inferior borders of stomach
38
adipose tissue in greater omentum
pads and protects surfaces of abdomen
provides insulation to reduce heat loss
stores lipid energy reserves
39
blood supply
digestive organs receive 1/4 cardiac output
this can increase following a meal
liver processes or absorbs nutrients from gut before blood returns to circulation
40
all venous return from GI enters
hepatic portal circulation
delivered to liver
41
disorders of peritoneal cavity
ascites
peritonitis
42
ascites
excess peritoneal fluid-> swelling of abdomen and distortion of organs
can cause heart burn, indigestion, back pain
43
peritonitis
inflammation of peritoneum from damage or infection
can cause pain and organ failure
44
4 major layers along entire length of digestive tract
1. mucosa
2. submucosa
3. muscularis externa
4. serosa
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mucosa
is the inner lining of digestive tract
46
mucosa functions to
1. secrete mucus, digestive enzymes, and hormones
2. absorb end products of digestion
3. provide protection from pathogens
47
mucosa layers
A. epithelium
B. lamina propria
C. muscularis muscosae
48
mucosa epithelium
continuously renewed, surface cells last 2-6 days
stratified squamous-> mechanical stresses- oral cavity, pharynx, esophagus, anus
simple columnar-> absorption- stomach, intestines with goblet cells (mucus) and enteroendocrine cells (hormones)
49
lamina propria
loose areolar connective tissue with-> blood vessels, lymphatic vessels, nerves, mucous glands
lymphoid tissue (extending from submucosa)
MALT (mucosa associated lymphatic tissue e.g. Peyer's patches) and tonsils
50
muscularis muscosae
bands of smooth muscles and elastic fibers
one layer circular, one layer longitudinal
functions to change shape of plicae and villi
51
villi
finger-like projections on the mucosa layer
increase surface area
52
plicae (small intestine)
permanent folds of mucosa and submucosa
increase surface area
53
rugae (stomach)
pleats of mucosa and submucosa
expand to accommodate volume
54
enteroendocrine and goblet cells
are scattered along columnar cells of digestive epithelium
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enteroendocrine cells secrete hormones that
coordinate activities of the digestive tract and accessory glands
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goblet cells secrete
gel-forming mucins
57
submucosa
layer of dense irregular connective tissue
surrounds muscularis mucosae
houses the submucosal nerve plexus
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submucosa contains
large blood vessels and lymphatic vessels
exocrine glands: secrete digestive enzymes and mucus into digestive tract
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submucosal nerve plexus
autonomic nervous system control of glands and smooth muscle of mucosa
also called the plexus of Meissner
innervates the mucosa and submucosa
60
submucosal plexus contains
sensory organs
parasympathetic ganglionic neurons
sympathetic postganglionic fibers
61
muscularis externa
is dominated by smooth muscle cells
is arranged in inner circular layer and outer longitudinal layer
contains the Myenteric Nerve Plexus
62
functions of smooth muscle
mixing and moving lumenal contents
circular layer thickened to create sphincters at junctions to prevent backflow
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Myenteric Nerve Plexus
enteric nervous system- ENS
control GI mobility via local reflex arcs and ANS stimulation (mostly parasympathetic)
64
serosa
membrane covering muscularis externa
visceral peritoneum- areolar connective tissue plus mesothelium (simple squamous epithelium)
covers all abdominal/peritoneal GI tract organs except oral cavity, pharynx, esophagus and rectum
65
adventitia
covers muscularis externa of oral cavity, pharynx, esophagus and rectum
dense irregular connective tissue sheath of collagen fibers
function to anchor organs to surrounding tissues
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movement of digestive materials
movement from visceral smooth muscle tissue
coordinated by short reflex arcs of ENS
peristalsis and segmentation
67
peristalsis and ENS
ENS also innervated by ANS allowing extrinsic control of digestive activity
68
parasympathetic
increase muscle activity and secretion
most ANS to the gut is parasympathetic
69
sympathetic
decrease muscle activity and secretions
70
peristalsis
waves of contraction
move food bolus along length of gut
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segmentation
single point contractions
chop up bolus
allow enzymes to access inner regions
72
peristaltic motion
1. circular muscles contract behind bolus- while circular muscles ahead of bolus relax
2. longitudinal muscles ahead of bolus contract- shortening adjacent segments
3. wave of contraction in circular muscles- forces bolus forward
73
oral cavity/mouth/buccal cavity
connects environment to pharynx
lined with stratified squamous epithelium
walls- muscular cheeks
floor contains tongue
roof- hard palate (anterior)
soft palate (posterior) with uvula- close off nasopharynx while swallowing
74
functions of the oral cavity
1. analyze food: taste buds
2. mechanically process food: chew
3. lubricate food: saliva- mixing with mucus and salivary gland secretions
4. digest starches: amylase- limited digestion of carbohydrates and lipids
75
oral cavity/mouth/buccal cavity accessory organs
tongue
salivary glands
teeth
76
tongue
muscular
surface covered by papillae
provide friction, house taste buds
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salivary glands
produce 1-2 L saliva/day
saliva=99% water plus enzymes, electrolyte buffers, mucins, antibodies, antimicrobials
78
three pairs of salivary glands
1. parotid salivary glands
2. sublingual salivary glands
3. submandibular salivary glands
each pair produces saliva with different properties
79
parotid salivary glands
25% of saliva
inferior to zygomatic arch
produce serous secretion- enzyme salivary amylase (breaks down starches)
80
sublingual salivary glands
5% of saliva
inferior to tongue
watery secretion, high in buffers
81
3. submandibular salivary glands
posterior floor of mouth
secrete buffers, glycoproteins (mucins), and salivary amylase
82
salivary glands sympathetic vs parasympathetic
low levels saliva produced continuously
parasympathetic stimulate increase secretion: food cue
sympathetic stimulate decrease secretion: "dry mouth"
83
teeth
mastication, mechanical digestion
structure: pulp cavity, dentin, above and below gums
84
pulp cavity
soft center that receive blood vessels and nerves in CT from the root canal-> called pulp
85
dentin
bone like, surrounds pulp cavity, contains odontoblasts which secrete and maintain dentin throughout life
86
above and below the gums
crown- covered in enamel
root- covered in cementum, attached to periodontal ligaments
87
contain 4 types of teeth
1. incisors
2. cuspids (canines)
3. bicuspids (premolars)
4. molars
88
incisors
blade-shaped teeth, located at front of mouth
8 total used for clipping or cutting
have a single root
89
cuspids (canines)
conical shaped
4 total used for tearing and piercing
single root
90
bicuspids (premolars)
2 ridges/cusps
8 total used for crushing, mashing, grinding
one or two roots
91
molars
4-5 ridges/cusps
12 total used for crushing and grinding
three or more roots
92
under age 12
you have 20 deciduous/milk teeth
primary dentition
replaced by age 13-21-> you get 32 permanent teeth- secondary dentition
93
disorders of teeth
1. impacted tooth
2. dental caries
3. periodontal disease
94
impacted tooth
fails to erupt
remains in jaw causing pain
surgical fix
95
dental caries
demineralization of enamel and dentin by bacteria
exposes nerves-> pain
96
periodontal disease
infection of gingiva (gums)
immunes response erodes bone around teeth-> teeth fall out
97
the pharynx
a common passageway for solid food, liquids and air
connects oral cavity to esophagus
shared space with respiratory system
stratified squamous epithelium
lamina propria has tonsils and mucus glands
skeletal muscles surround for swallowing
98
oropharynx
back of mouth
99
laryngopharynx
superior to voice box
100
esophagus
a hollow muscular tube, connects pharynx to stomach
about 25 cm long and 2 cm wide
passes through diaphragm to abdomen
at rest superior and inferior regions constricts to keep air out and stomach contents in
101
inferior constriction point of esophagus
gastroesophageal sphincter
102
"heartburn"
gastroesophageal reflux disease (GERD)
gastric juice regurgitates into esophagus causing erosion
103
histology of the esophagus
stratified squamous epithelium
large folds in mucosa and submucosa to keep lumen closed during rest
esophageal glands in submucosa secrete mucus to reduce friction
upper 2/3 of muscularis externa contains skeletal muscle
adventitia anchors esophagus
104
pharynx and esophagus
function in food propulsion from mouth to stomach
105
deglutations (swallowing)
1. buccal phase- voluntary
2. pharyngeal phase- involuntary reflex
3. esophageal phase- involuntary reflex
106
stomach functions
1. storage of ingested food (~1L)
2. mechanical breakdown of ingested food- churning
3. chemical breakdown of food- denature and digest proteins, disrupt chemical bonds in food by acids and enzymes
4. produce intrinsic factor for vitamin B12 uptake- vitamin B12 necessary for erythropoiesis- glycoprotein required for absorption of vitamin B12 in small intestine
107
chyme
stomach holds acidic mixture of enzymes and food
typically 1L but up to 4L
108
four major regions of the stomach
fundus
cardia
body
pylorus
109
fundus
superior region, contact diaphragm
110
cardia
where esophagus connects via gastroesophageal sphincter
gastric glands produce mucus to protect esophagus
111
body
majority of stomach
holds chyme
gastric glands secrete enzymes and acids for digestion
112
pylorus
inferior region
connects to duodenum via pyloric sphincter
regulates chyme entry into duodenum
gastric glands secrete hormones to stimulate gastric activity
113
features of the stomach
muscularis externa has 3 layers (+ oblique) assist mixing chyme
when empty mucosa and submucosa folds into rugae- can expand for large volume
mucosa has simple columnar epithelium with goblet cells that secrete alkaline mucus
mucosa perforated by deep gastric pits which connect to gastric glands in lamina propria
stem cells in gastric pits replace stomach epithelium every 3-6 days
114
gastric glands
produce 1-3L gastric juice/day
secretions vary per region
115
cardia gastric glands
mucus
116
fundus and body gastric glands
digestive enzymes and acids
117
two types of gastric cells
parietal cells & chief cells
118
pyloric gastric glands
mucus and hormones
119
2 important hormone producing gastric cells
G cells and D cells
120
parietal cell secretions
intrinsic factor (Vitamin B12 uptake)
H+ and Cl- ions combine to make HCl in stomach
121
chief cell secretions
pepsinogen
rennin
122
pepsinogen
converted to pepsin by acid in stomach; hydrolyzes proteins
123
rennin
infants only, curdles milk protein to aid digestion
124
acid production important to gastric function
1. kill microbes
2. denature proteins- digestion, destroy enzymes in food
3. break down plant cells walls and animal CT
4. activate pepsin
125
G cells
produce gastrin hormones
stimulates secretion by parietal and chief cells
promote contraction of gastric wall
secreted in response to food or parasympathetic stimulation
126
D cells
produce somatostatin hormone
inhibits release of gastrin
thus inhibits gastric activity
secreted in response to sympathetic stimulation
127
stomach disorders
gastritis
peptic ulcer
128
gastritis
inflammation of gastric mucosa
caused by drugs, stress, infection
chronic can lead to ulcer
129
peptic ulcer
erosion of stomach lining
caused by: too much acid and not enough mucus
most common: helicobacter pylori (bacteria)
130
secretion and motility of gastric activity controlled by 3 factors
1. innervation from CNS (ANS)
2. reflexes of the ENS
3. hormones
131
mechanisms of gastric activity rely on stimuli from 3 regions
head, stomach, and small intestines
132
3 phases of gastric regulation
cephalic, gastric, and intestinal phases
may all act simultaneously to alter gastric activity
133
digestion in stomach
much digestion occurs in the stomach but not much absorption- except alcohol and drugs
food does not usually remain in the stomach for more than 4 hours, but total time depends on the chemical makeup of food
134
how long it will take to digest in the small intestines
carbohydrate rich: pass quickly
fatty foods can cause chyme to remain in the stomach for 6+ hrs
135
small intestines
major digestive organ
chemical digestion completed
90% of nutrients absorbed- remaining absorbed in large intestine
20 ft long, 3 major subdivisions
136
3 major subdivisions of small intestines
duodenum
jejunum
ileum
137
duodenum
first 10 inches
retroperitoneal (behind the peritoneum)
receives chyme from stomach through pyloric sphincter
receives digestive secretions from pancreas and liver through duodenal ampula controlled by hepatopancreatic sphincter
mixing pot
138
jejunum
peritoneal
is the middle segment of small intestine-> 2.5 meters (8.2 ft) long
is the location of most: chemical digestion, nutrient absorption
139
ileum
peritoneal
last 12 ft
mucosa rich in lymphoid tissue
connects to cecum at ileocecal valve
140
small intestines histology
same 4 layers, but adapted for absorption
plicae, villi, microvilli
141
plicae in small intestine
mucosa and submucosa folded into circular plicae
cause chyme to spiral slowly
142
villi in small intestine
plicae covered with finger-like projections of mucosa called intestinal villi
base of each has crypt/intestinal gland
143
microvilli of small intestine
simple columnar epithelial cells have microvilli on apical surface
membrane called brush border of intestines
144
small intestines histology
plicae + villi + microvilli = 2200 ft2 surface area (compare to 3.6 ft2 for flat wall)
lamina propria of each villus contains capillaries- carry small nutrient molecules to liver via hepatic portal vein
larger molecules that cannot enter capillaries (lipid-protein complexes) are connected by special lymphatic capillary called a lacteal
contractions of muscularis mucosae: move villi to expose surface to new chyme, squeeze lacteal to more lymph
145
glands of small intestine
goblet cells
intestinal glands
146
goblet cells of small intestine
between columnar epithelial cells
secrete mucus (mucin)
147
intestinal glands of small intestine
variety of cells in the crypts
located in the lamina propria at the base of each villus
produce many products- intestinal juice, lysozyme, hormones
148
intestinal juice
(1-2L/day)
watery mucus, aids solubilization and absorption of nutrients
149
lysozyme
from Paneth cells, lyse bacteria
150
hormones
from enteroendocrine cells
all control GI activity
intestinal gastrin, cholecystokinin, secretin, gastric inhibitory peptide, vasoactive intestinal peptide, somatostatin, enterocrinin
151
intestinal cell regeneration
stem cells in glands
new cells are created from epithelial stem cells
cells migrate up villus
shed at tip
complete turnover 3-6 days
shed cells carry digestive enzymes in plasma membrane that function in lumen
152
brush border enzyme
complete digestion of carbohydrates and proteins
153
small intestinal movements
chyme arrives in duodenum
weak peristaltic contractions move it slowly toward jejunum
Myenteric reflexes- not under CNS control
parasympathetic stimulation accelerates local peristalsis and segmentation
154
Myenteric reflexes (ENS)
peristalsis to move chyme slowly through the small intestine
155
parasympathetic reflexes (stretch receptors)
accelerate movement
gastroenteric reflex
gastroileal reflex
156
gastroenteric reflex
stimulates motility and secretion along entire small intestine
157
gastroileal reflex
relaxes ileocecal valve
materials pass from ileum to cecum
158
pancreas
retroperitoneal
inferior to stomach
regions of the pancreas
head- broad, in loop of duodenum
body- slender, extends toward spleen
tail- short and rounded
159
lobules of the pancreas
are separated by connective tissue (septa)
contain blood vessels and tributaries of pancreatic ducts
160
in each lobule of pancreas
ducts branch repeatedly
end in blind pockets (pancreatic acini)
161
pancreatic acini (exocrine)
acinar cells= simple cuboidal epithelium
produce digestive enzymes and buffers-> pancreatic juice
162
pancreatic islets (endocrine) 1%
cells secrete insulin (increase storage of glucose-> decreases blood sugar levels) and glucagon (increase blood sugar levels) to control blood sugar
163
pancreatic juice
~1-1.5L/day in response to parasympathetic and hormonal control
water + electrolytes (buffer)
contain pancreatic enzymes: pancreatic alpha-amylase, pancreatic lipase, nucleases, proteolytic enzymes
164
pancreatic enzymes
~70% secreted as proeznymes, activated in the gut
1. pancreatic alpha-amylase- hydrolyzes starch
2. pancreatic lipase- hydrolyzes lipids and fatty acids
3. nucleases- hydrolyzes nucleic acids (RNA, DNA)
4. proteolytic enzymes- MAJORITY
165
proteolytic enzymes
many, each digests specific peptide bonds
2 main classes- proteases, peptidases
all proteolytic enzymes are secreted inactive
MUST be activated in the gut, this prevents autolysis
166
proteases
hydrolyze large proteins into peptides
167
peptidases
hydrolyze peptide chains into amino acids
168
pancreas exocrine secretions
pancreatic juice is released into pancreatic ducts-> joins with the common bile duct-> enters duodenum at duodenal ampula-> controlled by the hepatopancreatic sphincter
169
disorders of the pancreas
pancreatitis
diabetes mellitus
170
pancreatitis
inflammation of the pancreas
inflammation-> blocked ducts-> injury of acinar cells
necrotic cells release lysosome enzymes-> activate pro-enzymes-> autolysis
171
diabetes mellitus
destruction of islet cells
cause-> pancreatitis or autoimmune attack
result-> loss of regulation of blood sugar levels
172
the liver
is the largest visceral organ (1.5 kg)
right side, inferior to diaphragm
four lobes
anterior- large right and left lobes- separated by falciform ligament= fetal umbilical vein
posterior: tiny caudate lobe and quadrate lobe
173
lobules
hexagonal function units
separated by interlobular septa
central vein in the middle
six portal triads on hexagonal corners
174
hepatic artery
oxygen rich blood
175
hepatic portal vein
nutrient rich blood from small intestine
176
bile duct
collect bile produced by hepatocytes
177
hepatocytes
function in nutrient regulation and bile production
arranged in rows around central veins with sinusoids between rows
178
blood flow in lobule
blood from arteries and veins of triads flows through sinusoids
allows molecule exchange with hepatocytes
blood flows out through the central vein
179
Kupffer cells
sinusoids also contain Kupffer cellls (fixed macrophages)
functions to remove pathogens cell debris, damaged erythrocytes
remove and store ion
remove and store lipids
remove and store heavy metals
180
bile flow
bile secreted by hepatocytes-> flows through bile canaliculi between cells-> bile ducts of triads-> merge into common hepatic duct-> exits the loiver-> joins cystic duct from gallbladder creating common bile duct-> connects to duodenum at duodenal ampula controlled by hepatopancreatic sphincter
181
3 functions of liver
1. metabolic regulation
2. hematological regulation
3. digestive: bile production and secretion
182
metabolic regulation of liver
hepatocytes regulate blood nutrient levels
nutrient rich blood from GI goes to liver-> excess can be removed and deficits can be corrected
183
carbohydrates metabolism
too much glucose-> hepatocytes store glucose an glycogen
too little glucose-> hepatocytes break down glycogen or perform gluconeogenesis (synthesis from non-card) to release glucose
184
hepatocytes also carry out
lipid and amino acid metabolism
vitamin and mineral storage
waste removal, drug and toxin inactivation
185
composition of circulating blood
all blood leaving absorptive surfaces of digestive tract: enters hepatic portal system, flows into the liver
liver cells extract nutrients or toxins from blood: before it reaches systemic circulation through hepatic veins
liver removes and stores excess nutrients: corrects nutrient deficiencies by mobilizing stored reserves or performing synthetic activities
186
hematological regulation
liver serves as blood reservoir
kupffer cells- recycle RBCs and perform antigen presentation to lymphocytes
hepatocytes- remove/recycle hormones, remove antibodies, produce plasma proteins
hepatocytes and kupffer cells remove, inactivate, or store toxins, drugs, and heavy metals
187
bile components
water, bilirubin, phospholipids, electrolytes, cholesterol, bile salts (lipids)
188
bile functions
buffer chyme with electrolytes
emulsify fats- break large lipid globs into small droplets of phospholipids and bile salts
189
functions of emulsification
allow enzymes to access lipids
promote solubilization and absorption of lipids in blood and lymph
190
disorders of the liver
hepatitis
cirrhosis
191
hepatitis
inflammation of liver
cause-> viral infection
result-> restricts blood flow to liver
six known viruses with different severity
192
cirrhosis
chronic inflammation
cause-> severe hepatitis or alcoholism
result-> damaged hepatocytes are replaced by fibrous tissue and adipose
results in portal hypertension-> veins swell and rupture
193
the gallbladder
anterior and inferior to liver
functions to concentrate and store bile produced by liver
194
cholecystokinin (CCK) from duodenum causes:
1. release of bile by stimulating contraction of gallbladder
2. relaxation of hepatopancreatic sphincter
195
disorders of the gallbladder
1. gall stones- crystalizations of over concentrated bile
2. cholecystitis- inflammation caused by large gall stones that block or damage the gallbladder
196
the large intestine
~5 feet long
less than 10% of nutrient absorption
prepares fecal matter for ejection from the body
no digestion, except by microbes
water absorption important to feces consistency
too much water = diarrhea
too little water = constipation
197
functions of large intestine
1. reabsorb any remaining water and compact feces
2. absorb vitamins and electrolytes
3. storage of feces and defection
198
3 parts of large intestine
1. cecum- the pouchlike first portion
2. colon- the larges portion
3. rectum- the last 15 cm of digestive tract
199
cecum
attached to ileum via ileocecal valve
function-> begin compaction of feces
appendix on side- has lymphoid nodules that are part of the MALT
200
appendicitis
blockage of appendix
results in bacterial growth causing inflammation and swelling
rupture will release bacteria into abdomen-> peritonitis-> sepsis-> death
201
colon
absorbs water, vitamins, electrolytes
four major regions: ascending colon, transverse colon, descending colon, sigmoid colon
202
diverticulitis
pockets form in the colon wall
site of recurrent inflammation and infection
due to lack of fiber
203
rectum
stores feces
has 3 valves to separate feces and flatus
exits at anal canal
lined with stratified squamous epithelium
204
defecation controlled by two sphincters
1. internal anal sphincter- involuntary control, smooth muscle from muscularis externa
2. external anal sphincter- voluntary control- skeletal muscle under voluntary control
205
bacteria of large intestine
~2 lb bacteria in gut
some produce vitamins
vitamin K, biotin, vitamin B5
206
vitamin K
clotting factor synthesis
207
biotin
glucose metabolism
208
vitamin B5
steroid hormone and neurotransmitter synthesis
209
histology specialization of large intestines
muscularis externa made up of three longitudinal bands of smooth muscle called-> taeniae coli
contraction of taeniae coli produces pouches called-> haustra
mucosa has deep crypts with intestinal glands that produce mucus
no plicae and vili
lamina propria has large lymphoid nodules
epithelium is simple columnar with abundance of goblet cells
210
large intestine movements
1. haustral contractions
2. mass movements
3. defecation reflex
211
haustral contractions
local, slow segmenting contractions
shift feces for water absorption
212
mass movements
powerful peristaltic contractions
force feces toward rectum
occur few times/day
can trigger defecation reflex via stretch receptors in rectum
213
defecation reflex
stretch receptors-> parasympathetic stimulation->
1. contraction of sigmoid colo
2. relaxation of internal anal sphincter
voluntary control of external anal sphincter controls timing of defecation
214
time in colon controls water absorption
movement too fast-> too much water in feces = diarrhea
movement too slow-> too little water in feces = constipation
215
chemical digestion
large molecules catabolized into monomers
monomers absorbed by mucosa
enzymatic breakdown = catabolism; hydrolysis
216
a balanced diet contains:
carbohydrates, lipids, proteins, vitamins, minerals, water
217
carbohydrate digestion method
amylases (saliva, pancreas)
polysaccharides-> di and trisaccharides
brush border enzymes (small intestine)
di and trisaccharides-> monosaccharides
218
carbohydrate absorption method
facilitated diffusion or cotransport of monosaccharides
cellulose not digest: "bulk" fiber, aids intestinal mobility
219
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
220
lipid digestion method
bile salts (liver)-> emulsification
lipases (tongue, pancreas)
triglycerides-> monoglycerides and fatty acids
221
lipid absorption method
micelles form-> monoglycerides, fatty acids and bile salts
micelles absorbed by intestinal epithelium
proteins added = chylomicron (water soluble)
chylomicrons exocytosed into lumen
chylomicrons absorbed by lacteal
222
protein digestion method
mastication (mouth)
churning (stomach)
pepsin + acid (stomach)- protein-> polypeptide
protease + peptidases (pancreas, brush border)- polypeptide-> amino acids
223
protein absorption method
facilitated diffusion or cotransport of amino acids
224
nucleic acid digestion method
nucleases (pancreas)- nucleic acid-> nucleotides
brush border enzymes (small intestine)- nucleotides-> nitrogenous bases + sugar + phosphate ions
225
nucleic acid absorption method
active transport of nitrogenous bases + sugar + phosphate ions
226
water digestion method
no digestion required
2L from food, 7L from secretions
227
water absorption method
osmosis (95% in small intestine)
~150 mL lost in feces
228
ions
from food and secretions
must be regulated for homeostasis
control osmosis and pH, needed for enzyme function
229
ions digestion method
no digestion required
Na+, Ca++, K+, Mg++, Fe++, Cl-, I-, HCO3-
230
ions absorption method
diffusion, cotransport. active transport
231
vitamins digestion method
no digestion required
fat soluble: A, D, E, K
water soluble: most B vitamins, C, vitamins B12
232
vitamins absorption method
fat soluble: mixed with fats in micelle-> chylomicrons
water soluble B and C: diffusion
water soluble B12: bound to intrinsic factor-> binds receptors-> endocytosed
233
aging on the digestive system
1. epithelium division rates decline- ulcers more likely
2. smooth muscle tone decreases- constipation from slow movement, diverticulitis and hemorrhoids from weak walls
3. cumulative damage- teeth-> wear, liver-> toxin, lipid build up
4. increased cancer rate
