DIGESTIVE SYSTEM Flashcards
1
Q
gastric bypass
Hunger?
A
creating a small pouch at the top of the stomach and bypassing most of the stomach and the first part of the small intestine,
limiting how much food you can eat at once and reducing your appetite by altering the signals your body sends about hunger, leading to a feeling of fullness after consuming small meals; this means you will typically feel less hungry after the surgery compared to before
2
Q
DIGESTIVE SYSTEM
Two groups of organs
A
Alimentary canal (gastrointestinal tract
Accessory digestive organs
3
Q
Alimentary canal (gastrointestinal tract)
function and organs
A
Digests food and absorbs fragments
o Mouth
o Pharynx
o Esophagus
o Stomach
o Small intestine
o Large intestine
o Anus
4
Q
Accessory digestive organs
A
o Teeth, tongue, gallbladder
o Digestive glands
Salivary glands (Parotid, sublingual, submandibular)
Liver
Pancreas
5
Q
DIGESTIVE PROCESSES
Six steps
A
- Ingestion
- Propulsion
- Mechanical breakdown
- Chemical breakdown
- Absorption
- Defecation
6
Q
MOUTH (ORAL CAVITY) ANATOMY
A
- Vestibule
- Oral cavity proper
- Tongue
- Tonsils
7
Q
Vestibule cell type
A
non-keratinized strat. squam. epith
8
Q
tongue components
A
⚫ Hyoid bone, styloid processes of the temporal bone,
and lingual frenulum
Ankyloglossia
9
Q
Ankyloglossia
A
a condition that limits tongue movement due to a short, thick, or tight lingual frenulum.
10
Q
The lingual frenulum
A
membrane that connects the underside of the tongue to the floor of the mouth.
11
Q
Tongue functions
A
-Mechanical processing
- Assistance in chewing
and swallowing
- Formation of bolus
-Sensory analysis
-Lubrication
12
Q
Tonsils
components
A
⚫ Palatine
⚫ Lingual
13
Q
teeth
A
-Masticate food
-Humans have two sets of teeth
-Classification of Teeth
14
Q
Deciduous teeth
A
baby teeth
15
Q
Classification of Teeth
A
-Incisors - cutting
⚫ Canines - tearing or piercing
⚫ Premolars - grinding
⚫ Molars - grinding
16
Q
Three pairs of salivary glands
A
⚫ Parotid
⚫ Submandibular
⚫ Sublingual
17
Q
Salivary gland: saliva
A
Mucus and serous fluids
⚫ Helps to form a bolus
⚫ Dissolves chemicals
-gusTATION
-Contains salivary amylase
18
Q
starch digestion =
A
= breaks down complex
sugars
19
Q
DIGESTIVE ACTIVITIES OF THE MOUTH
A
Ingestion
Propulsion
Mechanical breakdown
20
Q
Mechanical breakdown
A
⚫ Mastication
⚫ Mixing with saliva
⚫ Initiation of swallowing by the tongue
-Allows for the sense of taste
21
Q
Chemical digestion
Starch —->
A
-Food is mixed with saliva
⚫ Starch is broken down into maltose (disaccaride) by
salivary amylase
22
Q
PHARYNX PHYSIOLOGY
A
Passageway for air and food
Lined with stratified squamous epithelium
Food is propelled to the esophagus
23
Q
Food is propelled to the esophagus by two muscle layers
A
- longitudinal (external, superficial) and
⚫ circular (internal, deep) layers
by Peristalsis
24
Q
ESOPHAGUS ANATOMY AND PHYSIOLOGY
A
- Tube: Pharynx to stomach
⚫ Conducts food by peristalsis
⚫ Passageway for food only
-non-keratinized stratified
squamous epithelium
25
Epiglottis
blocks passageway to trachea when swallowing or chewing
26
DEGLUTITION phases
Buccal phase
Pharyngeal-esophageal phase
27
Buccal phase
- Voluntary and occurs in the mouth
⚫ Bolus formed and forced into the pharynx by the
tongue
28
Pharyngeal-esophageal phase
⚫ Involuntary transport of the bolus
⚫ Peristalsis
⚫ Cardioesophageal sphincter is opened when food
presses against it
29
All passageways except to the stomach are blocked (what are they)
- Tongue blocks off the mouth
- Soft palate (and uvula) blocks the nasopharynx
- Epiglottis blocks the larynx
30
PERISTALSIS
MOVEMENT OF DIGESTIVE MATERIAL
o Visceral smooth muscle
o pacemaker cells
o Waves that move a bolus
31
LAYERS OF THE ALIMENTARY CANAL
- Mucosa
- Submucosa + glands
- Muscularis
-Serosa
32
Mucosa tissue
- non-keratinized stratified squamous epithelium
- lamina propria (areolar CT, vessels, nerves, IS [MALT])
- muscularis mucosae (smooth m.)
33
Muscularis: tissue
- (deep) circular
- (superficial) longitudinal
34
Serosa: tissue
- epithelium
- areolar CT
35
PERISTALSIS VS SEGMENTATION
- Smooth muscle regulated by
pacemaker cells
o Peristalsis causes waves that move
a bolus
o Segmentation churns, mixes, and
fragments a bolus
36
steps of swallowing and peristalsis
- Buccal phase
Tongue presses against the hard palate,
forcing the food bolus into the
oropharynx
- The pharyngeal-esophageal phase
*Uvula and larynx prevent food from entering respiratory passageways.
*The tongue blocks off the mouth.
*The upper esophageal sphincter relaxes, allowing food
to enter the esophagus.
- The upper esophageal sphincter contracts
(closes) after food enters
- Peristalsis moves
food through the
esophagus to the
stomach.
- The gastroesophageal
sphincter opens,
and food enters the stomach
37
FUNCTIONS OF THE STOMACH
- Mechanical breakdown
- Chemical breakdown
- Production of intrinsic factor
Storage
- Delivers chyme (processed food) to the
- small intestine
Very little absorption of nutrients
38
STOMACH ANATOMY
- Left side of the abdominal cavity
- cardioesophageal sphincter -- pyloric sphincter
(valves)
- Acid reflux / Heartburn
39
Regions of the stomach
⚫ Cardiac region
⚫ Fundus
⚫ Body
⚫ Pylorus is the funnel-shaped terminal end
40
Rugae
are internal folds of the mucosa
41
External regions of stomach
- Lesser curvature
⚫ Greater curvature
42
How could the beer have triggered or
heightened the heartburn symptoms.
essentially, the beer can cause the stomach to push acid back up into the esophagus, leading to heartburn.
43
STOMACH: MICROSCOPIC ANATOMY tunics
- Muscularis externa
Three layers of smooth muscle
- Mucosa
44
Muscularis externa
- inner layer allows stomach to churn, mix,
move, and physically break down food
45
mucosa has why type of cells
- Simple columnar epithelium and secretory cells
- Mucous cells
46
Mucous cells
Secrete two-layer coat of alkaline mucus
47
SECRETORY CELLS -- STOMACH MUCOSA
Mucous neck cells
Chief cells:
Parietal cells:
Enteroendocrine cells:
48
Mucous neck cells
thin, acidic mucus
49
Chief cells
digest Lipases
o Digest ~15% of lipids Rennin works on digesting milk protein in
infants, not adults
50
Chief cells pepsinogen breaks down
pepsin in acid
51
chief cells Rennin
works on digesting milk protein in
infants, not adults
52
parietal cells
- intrinsic factor (IF) for vitamin B 12
absorption
⚫ Hydrochloric acid (HCl)
Stomach content pH: 1.5-3.5
53
Enteroendocrine cells: Hormones
⚫ G cells secrete Gastrin
⚫ D cells secrete somatostatin
- ECL cells secrete Histamine
54
what happens with the presense of food
G cells from enteroendocrine relase gastrin
gastrin activate peristalsis, pepsinogen from cheif cells, hcl from parietal cells and mucos neck cells
pepsinogen from cheif cells activate pesin
hcl from parietal cells causes hostile environment
55
3 reflex pathways stimulate H+/K+ ATPase
(proton) pump to increase HCl secretion
- PSNS
⚫ Gastrin (by G-cells)
⚫ Histamine (by EnteroChromaffin-Like cells)
56
REGULATION OF DIGESTION: GASTRIC SECRETION
1) CEPHALIC PHASE
Sensory information to the brain associated to food triggers
PSNS (Vagus Nerve, CN X) to prepare gastric secretions to
receive food in the stomach
57
REGULATION OF DIGESTION: GASTRIC SECRETION
2) GASTRIC PHASE
Mechano-/stretch/chemo- receptors @wall of stomach
→ triggers ENS, PSNS
→ Stimulates gastric secretion
58
REGULATION OF DIGESTION: GASTRIC SECRETION
3) INTESTINAL PHASE
- Chemoreceptors @wall of SI
→ triggers ENS, PSNS
→ Stimulates gastric secretion
- Stretch receptors @wall of SI
→ triggers ENS
→ Inhibits gastric secretion
59
types of PROPULSION IN THE STOMACH
Segmental movements: 3 layers of muscle
Extrinsic gastrointestinal reflexes as food enters stomach
60
Extrinsic gastrointestinal reflexes as food enters stomach
- Enterogastric reflex:
⚫ Gastroileal reflex
⚫ Gastrocolic reflex:
61
Enterogastric reflex:
duodenal distension, acidic pH → inhibition of gastrin secretion (G-cells)
and gastric peristalsis
62
Gastroileal reflex
opens ileocecal valve → colonic peristalsis → defecation
63
Gastrocolic reflex:
sigmoid colon propels contents to rectum → defecation
64
small intestine Muscular tube w/3 subdivisions
Jejenum v.s. Ileum
Peyers patch?
Duodenum:
⚫ Jejunum: thin wall, lots of circular folds ,
⚫ Ileum: thick wall, more vascularity, first half had circular folds, lots of peyers patch
Pay role in immune system response to potential infections
65
small intestine SURFACE AREA
Complex histology
Circular folds (plicae circulares)
⚫ Villi
⚫ Microvilli
66
DIGESTION IN THE SMALL INTESTINE
Enzymes from the brush borde
Enzyme like maltase break down - disaccharides → simple sugars
⚫ enzyme like pepsin Complete some protein digestion
67
ABSORPTION IN THE SMALL INTESTINE
- Water
- Electrolytes
- Mostly active transport through cell membranes
-Lipids are absorbed by simple diffusion (hydrophobic compound)
- Fructose by facilitated diffusion
- Through blood,
to the liver
→ metabolism
16
68
DIGESTION IN THE SMALL INTESTINE what r broken down by Pancreatic enzymes play the major digestive function.
- Carbohydrate
⚫ Protein
⚫ Fat
⚫ Nucleic acid
69
PANCREAS
- Pancreatic duct penetrates duodenal wall
Endocrine functions (1%):
⚫ insulin, glucagon, somatostatin
70
Exocrine function (99%)
- Acini (clusters of secretory cells)
⚫ secrete pancreatic juice:
71
⚫ secrete pancreatic juice:
- bicarbonate to neutralize gastric acidic chyme
-salts
72
Digestive enzymes:
Active
Inactive
- in active form: lipases, amylases, nucleases
- as zymogens (inactive form): proteases
73
Liver
Bile?
⚫ Only digestive function → bile production
Bile – fat emulsifier
74
Gallbladder
⚫ Chief function → bile storage (& concentration)
Bile backs up
when hepatopancreatic valve is closed
75
CARBOHYDRATE
ABSORPTION
- pump
drives glucoseuptake bringing in Na into
intestinal cells.
- As Na + moves across the
membrane it
drives glucose against its
concentration gradient into
the cells.
-Fructose enters the cell
by facilitated diffusion
-All three monosaccharides
exit via facilitated
diffusion on the GLUT2 sugar
transporter.
76
PROTEIN
ABSORPTION
- Proteins and protein fragments
are digested to amino acids by
pancreatic proteases
- The amino acids are
absorbed by active transport into
the absorptive cells,
- The amino acids leave the villus
by facilitated diffusion
and enter the capillary
77
LIPID ABSORPTION
- Bile salts in the duodenum
emulsify large fat globules.
- Digestion of fat by lipase yields free fatty acids
and monoglycerides.
- Fatty acids and monoglycerides
diffuse into epithelial cells
78
ABSORPTION OF ELECTROLYTES
- Iron and calcium are absorbed in duodenum
- Na +
-Primary active transport Na+/K+ ATPase pump
(basolateral surface)
-at luminal surface: coupled with secondary active
absorption of glucose, galactose, and amino acids
79
ABSORPTION OF WATER
9 L water
⚫ 95% absorbed in the small intestine by osmosis
⚫ Also absorbed in large intestine
Concentration gradient established by active
transport of solutes
80
FUNCTIONS OF THE LARGE INTESTINE
- Absorption
- Compact material
- Feces
- Store fecal matter prior to defecation
81
Absorption
⚫ includes:
Water
Vitamins such as K, biotin, and B 5
Organic wastes
Bile salts
Toxins
82
LARGE INTESTINE ANATOMY
- villi
-columnar and types?
- No villi present, many intestinal glands
- Simple columnar epithelium:
⚫ Enterocytes
⚫ Goblet cells
83
Enterocytes
: absorptive cells
84
Goblet cells
alkaline mucus
85
LARGE INTESTINE ANATOMY
-digestive enzymes
-resident bacteria
-remaining materials
- No digestive enzymes produced
- Resident bacteria digest remaining nutrients
⚫ Produce some vitamin K and B
⚫ Release gases and acids
- Remaining materials → feces
86
LARGE INTESTINAL MOVEMENTS
-Peristalsis is the major means of moving food
-Defecation reflex
87
Defecation reflex
- Internal anal sphincter is relaxed
- Defecation occurs with relaxation
of the voluntary (external) anal sphincter
88
NUTRITION
- Used for growth, maintenance, and repair of all cells and
tissues in the body
89
Major nutrients
⚫ Carbohydrates
⚫ Lipids
⚫ Proteins
⚫ Water
90
Minor nutrients
⚫ Vitamins
⚫ Minerals
91
Energy Metabolism =
transformation of energy into
biologically useful forms
92
Energy is maximized through
aerobic respiration →
oxidative
phosphorylation
93
METABOLISM =
CATABOLISM + ANABOLISM
94
Metabolism:
Sum of all
biochemical reactions in
the body
95
Anabolism:
Reactions
that build larger
molecules
96
Catabolism:
Reactions
that break down complex
structures
97
ENERGY PRODUCTION: GLC → ENERGY
Carbohydrate metabolism by conducting…
-Glycolysis citric acid
-Very efficient
- Depends on Glc (& O 2)
access, concentration, and
transport
98
Glycogenesis (anabolic)
Synthesis of glycogen by polymerizing glucose
In liver
99
Gluconeogenesis (anabolic)
Synthesis of glucose from non-CHO pre cursors
In liver
100
Glycolysis (catabolic)
Splitting of glucose into two of pyruvate for an aerobic respiration or anaerobic fermentation
In all cells
101
Glycogenolysis (catabolic)
Splitting of glycogen into glucose monosaccharide
In liver and skeletal muscle cells
102
GLYCEMIA REGULATION
What diffusion
Limited and enhanced by what
- Glucose (Glc) must
be transported into
cells (from blood)
⚫ Facilitated diffusion
⚫ greatly enhanced by
insulin, limited by
glucagon
- Very efficient
- Depends on Glc (& O 2) access,
concentration, and
transport
103
INSULIN EFFECT
Fed state ?
What hormone needed?
What promotes insulin secretion
During fed state
(absorptive phase):
if ↗ Glucose (Glc) →
stimulates beta cells in
pancreas → ↗ Glc entry
in cells 20x
Hypoglycemic hormone:
Gastric Inhibitory
peptide secreted by
SI → ↗ insulin secretion
⚫ PSNS promotes insulin
secretion
104
GLUCAGON EFFECT
Fed state
What hormone needed ?
During fed state
(postabsorptive phase):
If glucose decreases a glucagon stimulates alpha cells in the pancreas
⇒ Hyperglycemic hormone :
Increase glycogenolysis and hepatocytes
Increase lipolysis in adipose tissue
105
integration in Glycemia Regulation:
Insulin (lowers blood glucose): what catabolic or anabolic reaction is used
Stimulates glycogenesis and glycolysis to store or utilize glucose.
106
integration in Glycemia Regulation:
Glucagon (raises blood glucose):
what catabolic or anabolic reaction is used
Stimulates glycogenolysis and gluconeogenesis to release or generate glucose.
107
Lipolysis:
Triglycerides
are degraded by lipases
108
If high [Glc] and
[ATP] ic →
Lipogenesis:
stores potential energy
109
PROTEIN METABOLISM: NEW PROTEINS & ENERGY
- Degradation of amino acids
- Protein Synthesis (all cells):
110
- Degradation of aa
- Transamination: amino acid turns to a-ketoglutarate forming glutamate + keto acid
- Oxidative deamination (in liver): glutamate broken down to release NH 4
NH4 converted to urea to detoxify it
- Keto acid modification: ketone acids modified to form metabolites for TCA to create ATP
111
- Protein Synthesis (all cells):
Proteins are synthetized if all aa needed are present at necessary
concentrations
112
Consumption =
Respiration + Production + Excretion
C = R + P + E
113
Respiration:
cost associated with basic
survival (basal), physical activity, feeding,
etc
114
Production:
cost associated with growth,
reproduction (shed gametes), replacing
lost tissues
115
Excretion:
Urinary loss, Feces
116
TOTAL METABOLIC RATE (TMR)
Total amount of kilocalories the body must consume to fuel
ongoing activities (R+P+E)
117
TMR must equal...
calories consumed to maintain homeostasis
and maintain a constant mass
118
C = TMR →
C > TMR →
C < TMR →
maintain mass
Gain mass
Lose mass
119
CONSUMPTION:
APPETITE REGULATION
Short term regulators:
120
Short term regulators:
Ghrelin
Peptide YY
Cholecystokinin
121
Ghrelin
(by parietal cells)
when empty
stomach → stimulate “hunger
122
Peptide YY
by enteroendocrine
cells in ileum and colon) →
gastroileal reflex, prevents stomach from
emptying quickly
123
Cholecystokinin (CCK)
(by
enteroendocrine cells in duodenum and
jejunum) →enterogastric reflex
124
Long-term regulators:
Insulin
Leptin
125
Insulin
(by pancreatic beta cells) → Glc
and aa uptake from blood to tissue cells
126
Leptin
(by adipocytes) → stimulates fat
breakdown (lipolysis) → “satiety”
127
The mucosal lining of the intestine experiences
rapid cell turnover thanks to stem cells present in the crypts (of Lieberkuhn) at the bottom of villi.
128
During vomiting (aka, emesis)
the stomach is relaxed, emesis occurs due to the forceful contraction of respiratory muscles (diaphragm, abdominal muscles).
129
Tight junctions of the small intestine prevent
anything from leaking between the epithelial cells.
130
If anabolic reactions exceed catabolic reactions in the adult, the result will be ____ .
weight gain
131
Triglycerides are transported by chylomicrons because
they cannot move easily in the blood stream because they are lipophilic, while the blood is hydrophilic
132
The gallbladder provides ____ that aid(s) in transport of lipids across the intestinal membrane.
bile salts
133
A deficiency in vitamin A can result in
improper eye development or sight
134
Parietal cells secrete _____.
HCl
