Porth: Chpt. 28 Flashcards
(170 cards)
1
Q
What is the GI Tract also referred to as?
A
- Digestive Tract
- Alimentary Canal
- Gut
2
Q
What is the Intestinal Portion of the GI Tract called?
A
- Bowel
3
Q
Name the Accessory Organs that produce secretions & aid in digestion?
A
- Pancreas
- Liver
- Salivary Glands
4
Q
Major Physiologic Functions of the GI Tract
A
- Digest food
- Absorb nutrients
5
Q
How does the GI Tract carry on the functions of digestion & absorption?
A
- Motility
- Secretion
- Digestion
- Absorption
6
Q
What happens to the Unabsorbed Nutrients & Wastes in the Large Intestine?
A
- Collected
- For later elimination
7
Q
What must Nutrients do in order to become part of the body’s Internal Environment?
A
- Pass through Intestinal Wall
- Enter Blood & Lymph Channels
8
Q
For Simplicity’s Sake:
What are the 3 parts of the GI Tract?
A
- Upper part
- Mouth, Esophagus, Stomach
- Intake source & Receptable
- 1st portion of digestive process
- Mouth, Esophagus, Stomach
- Middle part
- Duodenum, Jejunum, Ileum
- Digestion & Absorption!
- Duodenum, Jejunum, Ileum
- Lower part
- Cecum, colon, recturm
- Storage channel
- Elimination of waste
- Cecum, colon, recturm
9
Q
Which President signed Father’s Day into Law?
A
- 1966, President Lyndon B. Johnson issued the first presidential proclamation honoring fathers, designating the third Sunday in June as Father’s Day.
- Six years later, the day was made a permanent national holiday when President Richard Nixon signed it into law in 1972.
10
Q
What does Saliva do?
A
- Moisten & lubricates food
- Eaiser to Swallow
- Enzymes
- Initial digestion of Lipids and Starches
11
Q
The Esophagus
A
- 25cm, straight, collapsible tube
- Connects oropharynx w/ stomach
- Conduit for passage of food
- Smooth muscle = Peristalsis!
- Mucosal/Sub-mucosal glands = Protects surface, lubricates food
12
Q
The Esophagus
&
Its Sphincters
A
- 2: Upper & Lower
-
Upper = pharyngoesophageal
- Striated muscle
- Keeps air from entering stomach
-
Lower = gastroesophageal
- Circular muscle
- Tonically contracted
- Zone of high pressure
- Prevents reflux
- Passes through hiatus in diaphragm to join w/ stomach
-
Upper = pharyngoesophageal
13
Q
The Esophagus
&
“Receptive Relaxation”
A
-
Lower = gastroesophageal sphincter
- Allows propulsion of esophagus contents into stomach
- Hiatus region = high pressure
- Prevents reflux
14
Q
The Stomach
A
-
Pouchlike structure
- Food storage reservoir
15
Q
The Stomach
+
Cardiac Orifice
A
Where esophagus opens into stomach
16
Q
The Stomach
+
Pyloric Sphincter
A
End of pyloric canal
Circular, Smooth muscle
Valve = controls rate of stomach emptying
+ Prevents regurgitation of intestinal contents into stomach
17
Q
Middle GI Tract
A
-
Duodenum:
- 22cm long
- Connects Stomach to Jejenum
- Opening for Common Bile Duct + Main duct
- Juices enter via ducts
-
Jejunum & Ileum:
- 7m (23ft) long [folded]
- DIGESTION & ABSORPTION!
18
Q
Lower GI Tract
A
- Large intestine = 1.5m (5ft) long
- Cecum, Colon, Rectum, Anal Canal
- Cecum = Pouch @ junction btwn Ileum & Colon
- Valves - prevent return of feces into small intestine
- Appendix = 1in from ileocecal valve
- Colon
- Descending colon extends to rectum
- Rectum = sigmoid colon to anus
- Anal Canal = btwn levator ani muscles
- Spinchter muscles = no incontinence
19
Q
How fast does a crack in glass travel?
A
When glass breaks, the cracks move faster than 3,000 miles per hour!!!
20
Q
GI Wall Structure
The Digestive Tract is a __________ tube
A
-
Four-Layered Tube
- Inner Mucosal Layer
- Epithelium, Lamina propria, Muscularis mucosa
- Submuscosal (2nd layer)
- Connective & Adipose
- Muscularis externa (3rd layer)
- Serosal (4th layer)
- Mesothelium (squamous)
- Inner Mucosal Layer
21
Q
GI Wall Structure
Inner Mucosal Layer - Functions
A
- Lubricates & Protects inner surface of alimentary canal
- Secretes digestive enzymes
- Break down food
- Absorb breakdown products
- Prevents entry of bad substances
- Lymphatics in here = 1st line of defense
22
Q
GI Wall Structure
Inner Mucosal Layer - Epithelial Lining
A
- Rapid turnover rate
- Replaced q 4-5 days
- Heals rapidly
- No scar tissue
23
Q
GI Wall Structure
Second Layer - Function
A
- Secretes digestive enzymes
- Has lots of vasculature
24
Q
GI Wall Structure
Third Layer - Function
A
- Circular smooth muscle cells
- AND
- Longitudinal smooth muscle cells
- =’s
- Facilitate MOVEMENT of GI Tract contents
- =’s
25
**GI Wall Structure**
Fourth Layer - Function
* Equivalent to:
* **Visceral Peritoneum**
* *Most superficial layer of digestive tract parts suspended in peritoneal cavity*
26
**The Peritoneum**
*Largest serous membrane in the Body!*
**_2 layers;_**
1. Visceral
2. Parietal
27
**The Peritoneum**
*What is between the 2 layers of the Peritoneum?*
Peritoneal Cavity!
*"Potential Space containing serous membrane fluid"*
Moint & Slippery Surface - preventing Friction!
28
**The Mesentery**
Double layer of peritoneum
Encloses abdominal viscera & attaches it to the abdominal wall
* **Contains:** Blood vessels, nerves, lymph vessels
* Supply intestinal wall
* Holds organs in place
* Stores Fat
29
**The Omentum**
* Double-layered extension of peritoneum
* Passes from stomach or proximal part of duodenum to adjacent organs in abdominal cavity/wall
* *Greater Omentum*
* *Lesser Omentum*
30
**The Omentum**
*Greater Omentum Functions*
* Contains fat
* can be A LOT in obese people
* Mobile
* Moves around in cavity w/ peristatsis of intestine
* Forms adhesions
* Fiborous scar tissue
* Walls of infection & prevents spread
* Cushions & Insulates!
31
**Which Continent contains the most Deserts?**
* Antarctica
* Antarctica is considered a desert, with annual precipitation of only 200 mm (8 inches) along the coast and far less inland
32
**The movements of the GI Tract can be:**
**Rhythmic & Tonic**
* **Rhythmic**
* _Intermittent contractions_
* Mix & Moves food along tract
* esophagus, antrum, small intestine
* **Tonic**
* _Constant level of contraction w/o relaxation_
* lower esophagus, upper stomach region, ileocecal valve, internal anal sphincter
33
**What parts of the GI Tract are NOT made of Smooth Muscle?**
* Pharynx
* Upper 1/3 of Esophagus
* External Anal Sphincter
34
**Basic Properties of the GI Tract Smooth Muscle**
* Cells electronically coupled by low-resistance pathways
* ='s electrical signals that contract muscle move *quickly* from one fiber to the next!
* Pacemaker cells
* Rhythmic, spontaneous oscillations
* ***SLOW WAVES***
* Enteric Nervous System run this
* Located in GI Tract wall
* PNS and CNS
* Peptides, NTs, Hormones assist in Motility!
35
**Enteric Nervous System**
* Myenteric & Submucosal Plexuses in wall
* Nerve fibers & ganglion cell bodies
36
**Enteric Nervous System**
***Myenteric Plexus***
* Linear chain of interconnecting neurons
* Btwn longitudinal & circular msucle layers
* Runs all way down wall
* **Motility along length of gut!**
37
**Enteric Nervous System**
***Submucosal Plexus***
* Btwn mucosal & muscle layers of intestine
* **Controls function of each segment of intestinal tract**
* **Local control of**
* Motility
* Intestinal Secretions
* Nutrient Absorption
38
**Enteric Nervous System**
***Myenteric & Submucosal Plexuses***
Regulation
* Local influences
* Input from ANS
* Interconnecting Fibers transmit Info
* Mechanoreceptors
* Monitor stretch & distention
* Chemoreceptors
* Monitor chemical composition (pH, osmolality...)
39
**Which Insect has the Longest Life Span?**
A queen termite has been known to live 50 years....gross!
40
**What mediates the Autonomic NS of the GI System?**
Sympathetic & Parasympathetic NS
1. Parasympathetic NS = Increase in Enteric NS activity
2. Sympathetic NS = Inhibits Activity
41
**Parasypathetic Inneveration occurs through what nerve?**
Vagus Nerve
*(+ some of the colon is innvervated by fiber that exits via sacral region of spinal cord)*
42
**Preganglionic Parasympathetic Fibers**
Synapse w/ Plexus Neurons
(or) Act directly on Intestinal Smooth Muscle
+ Provide afferent nerves!
**Receptors lie w/in various gut tissue**
These nerves project to spinal cord & brain
='s Sensory Input for Integration
43
**Most Parasympathetic Innervation is....**
**Excitatory!**
44
**How does Sympathetic Innveration occur?**
Via Thoracic chain of sympathetic ganglia, superior mesenteric, inferior mesenteric ganglia.
45
**Sympathetic Innveration**
* Controls extent of mucous secretion by mucosal glands
* Reduces motility
* (inhibits activity of intramural plexus neurons)
* Enhances sphincter function
* Increases vascular smooth muscle tone of blood vessels
46
**Sympathetic Innveration**
&
Its effect
Blocks release of the excitatory neuromediators in intramural plexuses, which inhibits GI Motility!
47
**What begins the Digestive Process?**
Chewing!
Breaks food into small particles to swallow
Lubricates it w/ salvia
Mixes starch food w/ Salivary Amylase
48
**Swallowing...**
**Voluntary, or Involuntary?**
* Initiated as Voluntary
* Becomes involuntary when reach _Pharynx_
49
**Where is the "Swallowing Center"?**
* Reticular formation of the medulla and lower pons
* Responds to the Tactile receptors in pharynx & esophagus
* Turns into motor response via Medulla & Pons
50
**What nerves carry out the Swallowing Phases?**
* V, IX, X, XII
* oral & pharyngeal
* X
* esophageal
51
**If you damage the nerves that help you swallow - What are you at risk for?**
* Asphyxiation
* Aspiration pneumonia
52
**Three Phases of Swallowing**
1. Oral
1. Voluntary
2. Bolus touches pharynx
2. Pharyngeal
1. Epiglottis covers larynx
2. Bolus moved by constrictive pharynx movements
3. *Involuntary!*
3. Esophageal
1. Peristalsis triggered as Esophagus walls are stretched
53
**2 Types of Peristalsis**
* Primary
* Controlled by swallowing center
* When food enters esophagus
* Secondary
* Mediated by smooth muscle fibers
* Occurs when primary is inadequate
54
**Where does Peristalsis begin and go?**
* Begins: Site of distention
* Goes: Downward
* Before wave reaches stomach
* Lower esophageal sphincter relaxes & allows bolus to enter stomach
55
**Why is it good to have greater pressure in the lower esophageal sphinter versus the stomach?**
To PREVENT REFLUX of gastric contents
56
**What's the difference between a dirty old bus station and a lobster with boobs?**
One's a crusty bus station, and the other is a busty crustacean.
57
**What is the creamy mixture of food in the stomach called?**
Chyme
58
**What is the Volume of an Empty Stomach?**
**& How big can it expand to?**
* 50mL = empty
* 1000 mL (before intraluminal pressure rises)
59
**Motility of the Stomach results in....**
* Churing & mixing of solid foods
* Regulates emptying of chyme into duodenum
* Begins in Pacemaker area in middle of stomach
* Moves to Antrum (contractions increase)
* Pyloric sphincter is contracted during antral contraction
* Gastric contents emptied into dueodenum btwn contractions
60
**Pyloric Sphincter constriction prevents**
* Backflow of gastric contents
* Allowing them to flow into duodenum at a good speed/rate
61
**Why is the prevention of backflow into the stomach important?**
* Backflow of bile salts & duodenal contents =
* Damage of mucosal surface of antrum
* **ULCERS!!**
62
**Neural & Humoral Signals**
* Regulates stomach emptying
* Signals from stomach & duodenum
* DUODENUM = gives the strongest signals
* signals at rate to digest & absorb chyme
63
**What slows Gastric Emptying?**
* Hypertonic Solutions in the Duodenum
* Duodenal pH below 3.5
* Presence of Amino Acids, Peptides & Fatty Acids in Duodenum
64
**Stimulation of Gastric Emptying**
* Enteric NS & PNS, SNS connections mediate reflexes
* Hormones:
* Cholecystokinin & Glucose-dependent insulinotropic peptide
* slow emptying
Stimulated by: Fats (& other foods)
65
**If Gastric motility is TOO SLOW due to Obstruction or Gastric Atony what can occur?**
* Gastric Retention
66
**Obstruction can be due to:**
* Formation of Scar Tissue in pyloric area after a Peptic ulcer
* Hypertrophic Pyloric Stenosis
* in infants w/ thick muscularis layer in terminal pylorus
* **Treatment:**
* ****Myotomy - Surgical incision of muscular ring
67
**Gastric Atony**
* Can occur as complication of Visceral Neuropathies in DM
* Distruption of Vagal Activities
68
**Abnormally Fast Emptying**
* *"Dumping Syndrome"*
* Surgical complications
* characterized by:
* Rapid dumping of highly acidic & hyperosmotic gastric secretions into Duodenum & Jejunum
69
**What is the National Animal of Scotland?**
UNICORN!!!!
70
**Small Intestine**
**Major site for what?**
Digestion & Absorption of food
Movements = mixing + propulsive
71
**Small Intestine**
2 Patterns of contractions
* Segmentation
* Peristaltic
72
**Small Intestine**
Segmentation Contractions
* Slow contractions
* Circular muscle layer
* Occlude lumen
* Drive contents forwards & backwards
* Most = local contractions
* Freq increases after meals
* Mix chyme + digestive enzymes
* & ensure absorption occurs
73
**Small Intestine**
Peristaltic Movements
* Rhythmic, propulsive
* Propels chyme along small intestine towards large
* Smooth muscle contracts -\> Contractile band forces intraluminal contents forward
* Regular movements begin in deodenum near the common & hepatic ducts
* Propulsive & synchronized
* then relaxation...
* Propelled to ileocecal junction
* Sphincter relaxes & fluid goes into cecum
74
**What is a simple way to assess bowel activity?**
* Auscultation
* Inflammatory changes often increase activity
* Transient interruption can occur post-GI surgery
75
**Colon Movement & Defecation!**
* _2 types of colon movements:_
* **Haustrations**
* Segmental Mixing Movements
* occur in haustra (sacculations)
* "Digging type action"
* Exposes all portions of fecal mass to intestinal surface
* **Propulsive Mass Movements**
* Large colon segments contract as a unit
* Last ~30seconds & 2-3min relax
* Series lasts ~10-30 minutes several times a day
76
**Defecation is initiated by what?**
**& What's its transit time?**
**& Normal Stool Weight?**
* Mass movement
* Transit: 24-48 hours
* Weight: 250g/day
77
**What 2 Sphincters control action of defecating?!**
1. **Internal Anal**
2. **External Anal**
1. ****Controlled by pudendal nerve (somatic NS)
2. Voluntary Control
78
**What Reflexes control Defecation?**
* Defecation Reflexes!!
* **1. Intrinsic Myenteric Reflex**
* Mediated by enteric NS
* Intiated by rectal wall distention
* **2. Parasympathetic Reflex**
* Sacral Cord
* Impulses increase peristaltic movements & relax the Internal Sphincter
79
**Thank you Cortex for.....**
**Preventing Involuntary Defecation !**
## Footnote
*(via Conscious Control - Constricting the External Sphincter)*
The cortex is alerted of a distended rectum via Afferent impulses arriving to let it know...
*& Afferent impulses get tired sometimes... Ceasing urge to defecate!*
80
**Which Dr. Suess Book has exactly _50_ words in it?**
Green Eggs and Ham!
81
**GI Hormones**
What is the Largest Endocrine Organ in the Body?
**GI Tract**
82
**GI Hormones**
Where do the GI Hormones go?
**Everywhere!**
* Locally
* Pass into general circulation
* Interact w/ CNS via enteric & autonomic NS
83
**GI Hormones**
What are some of them?
* Gastrin
* Ghrelin
* Secretin
* Cholecystokinin
* Incretin Hormones
* GIP
84
**GI Hormones**
What do they influence?
* Appetite
* GI Motility
* Enzyme activity
* Electrolyte levels
* Secretion & Action of other hormones
85
**GI Hormones**
Stomach Hormones
* Gastrin
* Ghrelin
86
**GI Hormones**
Stomach Hormones
*Gastrin*
* Gastrin
* Produced by: G cells
* Fxn: Stimulation of gastric acid secretion
* Growth producing effect on mucosa of small intestine, colon, & acid secreting area of stomach
* Removal of gastric producing tissues causes atrophy to these regions
87
**GI Hormones**
Stomach Hormones
*Ghrelin*
* Ghrelin
* Potent growth-releasing activity
* Stimulatory effect on food intake & digestive fxn
*Random fact: Isolation of this hormone = bringing insights into gut-brain regulation of growth hormone secretion & energy balance*
88
**GI Hormones**
Intestine Hormones
* Secretin
* Cholecystokinin
* Incretin
89
**GI Hormones**
Intestine Hormones
*Secretin*
* Secretin
* Secreted by S Cells in duodenum & jejenum
* Inhibits gastric acid secretion
* Chyme presence stimulates secretin
* Which then inhibits gastrin release
* Stimulates Pancreas to secrete fluid w/ [high bicarb. & low Cl]
90
**GI Hormones**
Intestine Hormones
*Cholecystokinin*
* Cholecystokinin
* Secreted by I cells
* Stimulates pancreatic enzyme secretion
* Potentiates action of secretin
* Stimulate biliary secretion of fluid & bicarbonate
* Regulates gallbladder contraction & gastric emptying
* Inhibit food intake (Mediator for appetite & meal size control!)
91
**GI Hormones**
Gut-Dervied Hormones
* &*
* the Incretin Effect*
* Incretin Effect
* Increase insulin release after an oral glucose load
* Gut-derived factors can stimulate insulin secretion after a high carb meal
* 2 Hormones involved:
* GLP-1
* GIP
92
**GI Hormones**
Gut-Dervied Hormones
* &*
* the Incretin Effect and the hormones GLP-1 & GIP*
* GLP-1 & GIP
* Augment insulin release in a glucose-dependent manner
* Targets as possible: Anti-diabetic drugs
* GLP-1
* suppress glucagon release
* slow gastric emptying
* augment net glucose clearance
* decrease appetite & body weight
93
What does **CHARGOGGAGOGGMANCHAUGGAGOGGCHAUBUNAGUNGAMAUGG** mean?
It means "you fish on your side, I fish on my side, and no one fishes in the middle."
There's a Native American lake named _Chargoggagoggmanchauggagoggchaubunagungamaugg_.
This lake is located in Webster, Massachusetts.
94
**2 Basic Functions of _Secretory Glands_**
**in the GI Tract**
1. Production of mucus to lubricate & protect mucosal layer of tract wall
2. Secretion of fluids & enzymes to aid in digestion & absorption of nutrients
95
**GI Secretions**
Each day 7000mL of fluid is secreted into GI tract & 50-200mL leaves in stool.
* Secretions = water + [Na & K]
* Excessive secretion or impaired absorption = Extracellular fluid deficit
96
**GI Secretions**
***What influences the secretory & digestive functions?***
* Local
* Humoral
* Neural
* via ANS
* Secretion increases w/ parasypathetic activity (like motility)
* Inhibited by sympathetic
* pH, osmolality, chyme - stimuli for neural & humoral mechanisms
97
**Salivary Secretions**
* Salvia is secreted
* Remember your glands from Anatomy!
* Parotid, submaxillary, buccal....
* **3 fxns:**
* Protection & Lubrication
* Muscus (sublingual & buccal glands)
* Protective antimicrobial action
* Lysozyme
* Ptyalin & Amylase
* Initiate digestion of starches
98
**Salivary Secretions**
* ANS regulates secretions
* Parasympathetic = incrases flow
* Sympathetic = decreases
* Dry mouth? Thank your sympathetic NS
* Mumps (parotitis)
* Parotid gland infection
* Can occur in ill person w/ bad oral hygiene
99
**Gastric Secretions**
* Stomach has mucus secreting cells & others:
* Pariteal (oxyntic) cells
* Secrete HCl & Intrinsic factor
* Chief cells
* Secrete pepsinogen
* Initiates protein-breakdown
* G cells
* Secrete Gastrin
100
**Gastric Secretions**
Pariteal (oxyntic) cells
* Secrete HCl & Intrinsic Factor
* Approximately 1 Billion cells in stomach
* Produce & Secrete 20mEq of HCl in several hundred mL of gastric juice/hour
* Intrinsic Facor
* Absorbs Vit. B12
101
**Gastric Secretions**
Gastric Mucosa Characteristics
* Resistant to highly acidic secretions it produces
* When damaged (via nsaids, etoh, bile), Hydrogens move into tissue & accumulate
* pH decreases
* Ezymmatic reactions impaired
* Structures disrupted
* Results in:
* Ischemia, vascular statsis, tissue necrosis
102
**Gastric Secretions**
Gastric Mucosa Characteristics
* Protected by Prostaglandins
* Aspirin & NSAIDs decrease PG synthesis...
* ='s impairs integrity
103
The average person spends 2 weeks of their lifetime waiting for the light to change from red to green.
Isn't that refreshing?
104
**Gastric Acid Secretion**
*What cellular mechanism is in charge of the HCl secretion in the Parietal Cells?*
* Hydrogen Ion (H+)/Potassium Ion (K+)-ATPase Transporter
+
* Chloride Ion (Cl-) channels
* (in the Luminal membrane)
105
**Gastric Acid Secretion**
*HCl Secretion Process*
Pt. 1
* CO2 combines with H2O
* catalyzed by carbonic anhydrase
* Forms carbonic acid
* Turns into H+ + HCO3-
* H+ + Cl- secreted into stomach
* HCO3- moves out of cell & into blood
106
**Gastric Acid Secretion**
*HCl Secretion Process*
Pt. 2
* HCO3- ='s alkaline increase (^pH) occuring after meal
* Proton pump (H+/K+-ATPase Transporter) moves H+ into stomach
* Cl- follows (via diffusion in luminal membrane)
107
**Gastric Acid Secretion**
*Proton Pump Inhibitor (PPI) Function*
* Inhibit gastric acid secretion by binding irreversible to sulfhydryl groups of H+/K+-ATPase transporter
* Treat Acid Reflux & Peptic Ulcer
108
**Gastric Acid Secretion**
*3 Substances that Stimulate HCl secretion*
* ACH (from vagal nerves)
* Gastrin (G cells)
* Histamine (endocrine cells)
Each bind to a different Parietal cell & different MOA, BUT:
-stimulate increase of H+ via Proton Pump
109
**Gastric Acid Secretion**
*H2 Receptor Blockers function*
* Treats peptic ulcer & GERD
* Binds to H2 Receptors & blocks action of Histamine on Parietal Cells
110
**Gastric Acid Secretion**
*Prostaglandin E2*
* Inhibits acid secretion & simulates mucous production
* Important in: Maintenance of Gastric Mucosal Barrier!
111
**Intestinal Secretions**
*Small Intestine*
* Secretes digestive juices & recieves secretions from liver & pancreas
112
**Intestinal Secretions**
*Brunner Glands*
* Mucus-producing glands
* Concentrated:
* where contents from stomach & secretions from liver + pancreas enter the duodenum
* Secrete alkaline mucus
* Protects from duodenum from acidic content
* Influenced by ANS
113
**Intestinal Secretions**
*Brunner Glands*
Activity Example
+ Peptic Ulcer FYI
* Sympathetic stimulation
* Marked decreased in mucous production
* ='s more susceptible to irritation
* **Between 75-80% of Peptic Ulcers occur at this site**
114
**Intestinal Secretions**
*Mucus + other Secretions in the Small Intestine....*
* **1. Mucus secretions**
* **2. Serous fluid**
* pH 6.5-7.5
* secreted by crypts of Liberkuhn
* ABSORPTION Vehicle
* **3. Surface Enzymes**
* Aid in absorption
* Ex: Peptidases & Disaccharidases
115
**Intestinal Secretions**
*Mucus + other Secretions in the Large Intestine....*
* Secretes only mucus (usually)
* ANS activity = influencer
116
**Intestinal Secretions**
*Mucus Secretion in the Large Intestine, pt. II*
* Intense Parasympathetic Stimulation
* Mucus secretion increases so much, that stool contains lots of mucus
* When bowel irritated or inflamed:
* Water & Electrolytes lost in large quantities
117
How long do Taste Buds last for?
Taste buds go through a life cycle where they grow from basal cells into taste cells and then die and are sloughed away.
Taste Bud's normal life cycle is anywhere from 10 days to two weeks.
118
**Intestinal Flora**
Major functions
* Gut = natural habitat of tons of bacteria
* Metabolic activites
* salvage energy & absorbable nutrients
* trophic effects on intestinal epithelial cells
* protection of colonized host against invasion of pathogenic organisms
119
**Intestinal Flora**
Stomach & Small Intestine
* Contain only a few species of bacteria
* B/c composition of luminal contents kills most microorganisms
* & B/C constant propulsive movements of this area
120
**Intestinal Flora**
Large Intestine
* Large & Complex Ecosystem
* **300-500 different species** of intestinal bacteria
* Anaerobic bacteria \> Aerobic Bacteria
121
**Intestinal Flora**
Colon-ization!
* Begins post-partum
* Influenced by:
* Passage through birth canal
* Infant's diet
* Other Environmental factors
122
**Intestinal Flora**
Major Metabolic Function
* Ferments of undigestable dietary residue & endogenous mucus
* Fermentation of non-digestable carbs (starches, cellulose, pectins...) ='s
* Major source of Energy!!
* Vitamin Synthesis
* Absorbs Ca, Mg, Fe
* Line of resistance to colonization by exogenous microbes
* Protective!
123
**Intestinal Flora**
Metabolic Endpoint
* Generation of short-chain fatty acids
* ='s aid in epithelial growth & differentiation
124
**Intestinal Flora**
Broad-Spectrum Abx
* Administration of broad-spectrum abx
* disrupts microbial balance
* allows overgrowth of species that can be BAD!
* ex: *C. diff*
125
**Intestinal Flora**
Probiotics
* Increasingly recognized
* Supplement to normal diet + treatment use
* Live microorganisms
* When ingested - modify composition of enteric microflora
* Common ones:
* lactobacilli, bifidobacterida, non-pathogenic *E. coli*
* Valuable in some diseases:
* ex: Remission in Ulcerative Colitis!
126
**Digestion**
Process of dismantling foods into constituent parts.
127
**Digestion**
Requirements
* Hydrolysis
* Breakdown of compound involves H2O
* Enzyme cleavage
* Fat Emulsification
128
**Digestion**
Intestines are impermeable to
* Large Molecules!
* Proteins, Fats, Carbs
* must be broken down
129
**Digestion**
Intestines are impermeable to
* Large Molecules!
* Proteins, Fats, Carbs
* must be broken down
130
**Digestion**
Digestion mainly takes place in....
**The Small Intestine!!**
* Fats to free fatty acids
* Monoglyceride breakdown
*The liver & pancreas supply digestive enzymes & help out!*
131
**Digestion**
Absorption
Process of moving nutrients & other materials from external environment in the lumen of the GI Tract into the Internal Environment
132
**Digestion**
Absorption- Accomplished by
Active transport & diffusion
133
**Digestion**
Absorption
*Large Intestine Absorption*
Focuses mainly on water reabsorption
134
**Digestion**
Distinguishing factor of the Small Intestine
LARGE Surface Area
(~250 m2)
Large b/c circular folds & MANY Villi!
135
**Digestion**
Villi of the Small Intestine
Contain:
* Artery
* Vein
* Lymph Vessel
* Bring blood to surface of intestine &
* Transport nutrientns & other materials
136
**Digestion**
Villi of the Small Intestine
&
Enterocytes + Mucus
* Covered in cells called _Enterocytes!_
* __Absorption & Digestion
* Goblet Cells
* Mucus
137
**Digestion**
Villi of the Small Intestine
&
Crypts of Lieberkühn
* Crypts of Lieberkühn
* Glandular structures that open into villi spaces
* New (replacement) enterocytes are created here
138
**Digestion**
Villi of the Small Intestine
&
Brush Border Enzymes
* Enzymes that aid in Carb & Protein digested
* Secreted by Enterocytes
* Stick to border of villus structures & eat up the carbs and protein as they come in contact w/ the intestine surface
139
**Digestion**
Villi of the Small Intestine
&
Where do digested Molecules go?
* Diffuse through membrane
* or
* Actively transported across mucosal surface to enter blood (fatty acids enter luteal)
* Molecules are transported through portal vein or lymphatics into systemic circulation
140
**What Animal is the _Sleepiest_ in the World?**
The koala sleeps 22 hours a day!
Next is the sloth (20 hours), armadillo and opossum (tied at 19 hours each), lemur (16 hours), then hamster and squirrel (tied at 14 hours each).
141
**Carbohydrate Digestion & Absorption**
* Carbs must be broken down into
* Monosaccharides
* (before absorption!)
142
**Carbohydrate Digestion & Absorption**
*Begins with the Action of.....*
* **Amylase!**
* Pancreatic secretions contain this.
* Breaks down starch into disaccharides.
143
**Carbohydrate Digestion & Absorption**
*Amylase breaks down Starch, then....*
* **Brush Border Enzymes**
* ****Break down Disaccharides into Monosaccharides
144
**Carbohydrate Digestion & Absorption**
*If Disaccharides cannot be Broken down:*
* Cannot be absorbed
* Remain osmotically acitve particles
* Causing:
* **Diarrhea**
145
**Carbohydrate Digestion & Absorption**
*Carbohydrate Breakdown chart*
146
**Carbohydrate Digestion & Absorption**
*What occurs when people have a lactase deficiency?*
* They cannot break down lactose
* So when they have dairy products (milk, etc..) ='s
* **Diarrhea**
147
**Carbohydrate Digestion & Absorption**
*Water absorption in the intestine is linked to?*
* Absorption of osmotically active particles
* (glucose & sodium)
*So - if you are having bowel disruptions, include glucose & sodium in fluids being consumed to decrease diarrhea*
148
**Fat Digestion & Absorption**
*What is the main type of Fat the average adult eats daily?*
* Triglycerides
149
**Fat Digestion & Absorption**
*First step in Lipid digestion*
* Break down large globules of dietary fat
* Make smaller particles
* so H2O soluble digestive enzymes can act on them
150
**Fat Digestion & Absorption**
*Emulsification*
* Breaking down of lipids to smaller particles
* Begins in the stomachs, continues in duodenum
* Bile from liver helps!
* Exposes lipids to pancreatic lipase ='s
* Creates free fatty acids & monoglycerides
151
**Fat Digestion & Absorption**
*Bile Salts Role*
* Form Micelles
* Transport broken down lipids to intestinal villi
152
**Fat Digestion & Absorption**
*What occurs when broken down Fats are brought to the Intestinal Villi?*
* Taken into epithelial cells & form NEW TRIGLYCERIDES!
* Released into the lymphatic system (as chylomicrons)
*(& some fatty acids are instead absorbed directly into portal blood - instead of becoming triglycerides)*
153
**Fat Digestion & Absorption**
*What do you call Fat that is NOT absorbed into the Intestine?*
* **Steatorrhea**
* ****Excreted in the stool
* \>20g+ of fat in stool in a 24-hour stool sample
154
**The Chapter is almost DONE!!**
Wahoo!
155
**Protein Digestion & Absorption**
Begins where? & Who is the main player?
* Begins in the: **Stomach**
* Player: **Pepsin******
*[Pepsinogen (enzyme precursor to pepsin) = secreted by chief cells in response to a meal & acid pH --\> Acid is required to convert to Pepsin.]*
156
**Protein Digestion & Absorption**
When does Pepsin gets inactivated?
* When it enters the Intestines
* alkaline pH inactives it
157
**Protein Digestion & Absorption**
Further Protein break-down
* Pancreatic Enzymes aid in breakdown
* Ex: Trypsin, Chymotrypsin....
* Proteins are broken down:
* into Peptides
* 1, 2, or 3 amino acids long
158
**Anorexia, Nausea, Vomiting**
Physiologic Responses common to MANY GI Disorders
* Are both:*
* Protective & Destructive*
159
## Footnote
**Anorexia**
**Loss of Appetite**
* Influences:
* Hunger
* Stimulated by empty stomach contractions
* Regulated by:
* Hypothalmus & assc. brain centers
* Smell = plays important role
160
**Anorexia**
*Factors for Loss of Appetite*
* Emotional Factors
* Fear, depression, anxiety...
* Drugs
* Diseases
* Ex: uremia (accumulation of nitrogenous wastes in blood)
*Is a "forerunner" of Nausea!*
161
**Nausea**
* Conscious sensation
* Stimulation of Medullary vomiting center
* Precedes/accompanies vomiting
* Stimulants:
* Foods
* Drugs
* Distention of duodenum or upper small intestine
162
**Nausea**
*Accompanied By:*
* ANS Manifestations:
* Watery Salivation & Vasoconstriction
* Pallor, sweating, tachycardia
163
**Retching**
* Retching:
* Rhythmic spasmodic movements of diaphargm, chest wall, abdomial muscles
* Precedes/alternates w/ vomiting
164
**Vomiting**
* Vomiting:
* Sudden & Forceful oral expulsion of contents of stomach
* preceded by nausea
* Physiologic Protective Mechanism:
* Limits damage of ingested noxious agents by emptying contents of stomach/sm. intestine
165
**Vomiting**
2 Medullary Centers
* 1. Vomiting Center
* Reflex, integrated here
* Near sensory nuclei of vagus
* 2. Chemoreceptor Trigger Zone
* Mediates emetic effects of blood-borne drugs & toxins
166
**Vomiting**
Factoids
* Gastroesophageal Sphinter relaxes
* Respiration ceases
* Accompanied by:
* Dizziness
* Light-headedness
* BP drop
* Bradycardia
167
**Vomiting**
Vomiting Center, pt. 1
* Input from
* GI Tract
* Cerebral Cortex
* Vestibular Apparatus
* (motion sickness)
* & Chemoreceptor Trigger zone
168
**Vomiting**
Vomiting Center, pt. 2
Causes of N/V:
* **Hypoxia**
* periods of: decreased cardiac output, shock, brain ischemia...
* **Intra-abdominal organ inflammation**
* b/c stimulates visceral afferent pathways
* **Distention or Irritation of the GI Tract**
* ****b/c stimulates visceral afferent neurons
169
**Vomiting**
Neuromediators
* Dopamine
* Serotonin
* Opiod
* Receptors found in GI Tract, vomiting center & chemoreceptor trigger zone
* ACH receptors = Excite vomiting center
* Norepinephrine receptors = stablizing influence resisting motion sickness
170
**Vomiting**
Neuromediator Drugs
* Dopamine antagonists = depress vomiting
* Serotonin Antagonists = depress N/V assc. w/ chemo
* Motion sickness drugs = CNS Anti-cholinergic effects
* Act on vomiting center + vestibular system
