Test 3 Digestive System Flashcards
What accessory Digestive organs make considerable contribution to digestion?
Liver
Pancreas
What provides initial mechanical breakdown of food?
Teeth
What are the cells of the Gastric Mucosa?
Mucous Surface Cell
Mucous Neck Cells
Oxyntic (Parietal) Cells
Peptic (Chief) Cells
What is excreted by all cells of the Gastric Mucosa?
Water
What is excreted by the Mucous Surface Cells?
Mucus
Bicarbonate
Water
What is Excreted by the Oxyntic (Parietal)Cells?
Hydrogen Ions
Chloride Ions
Intrinsic Factor
Water
What is Excreted by the Peptic (Chief) Cells?
Pepsinogen
Water
Mucus (Foveolar) Cell function in the stomach?
Mucus-producing cells which cover the inside of the stomach, forms a protective barrier from corrosive gastric acid and digestive enzymes
Like bone, teeth require what?
Collagen-like proteins and glycoproteins
Name some of the collagen-like Proteins and Glycoproteins that are required for teeth?
- Amelogenin (Protein)
- Ameloblastin (Protein)
- Enamelin (Protein)
- Tuftelin (Glycoproteins)
The Collagen-like proteins and glycoproteins organize, initiate, and direct what?
Calcium Phosphate (Ca3(PO4)2) crystal formation and anchor teeth to gums
What causes dental plaque?
Enzymatic process mainly by normal oral bacteria
What is significant about organisms in plaque located closest to the teeth?
Exist in an oxygen-deficient environment and convert to anaerobic respiration for energy
In an anaerobic environment, Carbohydrates are turned into what from what?
Lactic Acid from Pyruvate
The formation of Lactic Acid results in what regarding pH and leads to what?
pH below 5.5 leading to tooth decay (the demineralization process that causes cavities)
What are the main carbohydrate sources for formation of lactic acid?
Glucose, Fructose, and especially Sucrose
What Phase consists of thoughts of eating, feelings of hunger, and saliva production controlled by neuro biochemical processes?
Cephalic Phase
This phase occurs from the physical presence and act of chewing and tasting food eliciting further signals that enhance saliva formation and expression?
Gustatory Phase
What is the saliva-produced hormone that activates calmodulin-dependent cAMP phosphodiesterase involved in taste bud formation?
Gustin
What is the Composition of Saliva?
- Water (98-99%)
- Electrolytes
- Major Digestive Enzymes
What electrolytes are found in saliva?
Sodium Potassium Calcium Magnesium Chloride Bicarbonate Phosphate
What Major Digestive Enzymes are found in Saliva?
Alpha-Amylase Lingual Lipase (secreted by the tongue)
Alpha-amylase initiates random digestion of what, producing what in the process?
Initiates random digestion of amylose and amylopectin chains, producing maltotriose, maltose, amylose, glucose, and oligosaccharides
Lingual Lipase initiates hydrolysis of what and continues to where?
Initiates hydrolysis of long-chain triglycerides into diacylglycerol and free fatty acids, which continues into and through stomach.
For optimal activation of Lingual Lipase what is required and in turn where does this occur?
Acidic (pH4) environment, vast majority of activity is in the stomach
Name the minor digestive enzymes found within Saliva?
- Salivary Acid Phosphatases A + B
- N-acetylmuramoyl-L-alanine Amidase
- NAD(P)H Dehydrogenase (quinone)
- Superoxide Dismutase
- Glutathione Transferase
- Aldehyde Dehydrogenase (class 3)
- Glucose-6-Phosphate Isomerase
What antibacterial compounds are found in Saliva?
H2O2
Immunoglobulin A
What is the function of Superoxide Dismutase?
Reduces highly reactive superoxide molecules
What does Superoxide Dismutase reduce highly reactive superoxide molecules into?
Oxygen and Hydrogen Peroxide (H2O2)
How does Superoxide Dismutase reduce Highly reactive superoxide molecules?
Oxidation of a metal ion
This Enzyme detoxifies molecules containing the sulfur -containing, tripeptide glutathione, produced from the cysteine, glutamic acid, and glycine AA’s, via reduction and conjugation?
Glutathione Transferase
What compound is the main immunoglobulin in saliva and plays a critical role in mucosal immunity?
Immunoglobulin A
What antimicrobial enzymes are found in saliva?
Lactoferrin
Lactoperoxidase (Salivary)
Lysozyme
Thiocyanate (SCN)
What is the composition of mucus within saliva?
Mucopolysaccarides
Glycoproteins
What are the approx. numbers of cells (human and bacterial) within saliva and what is significant about their metabolism?
8 million human/ml; 500 million Baterial.ml
-Bacterial metabolism leads to production of thiols, amines, and organic acids causing bad breath
What is the medical term for bad breath?
Halitosis
Which antimicrobial enzyme produces small peptides, called lactoferricin and kaliocin-1, which, coupled w/ iron, inhibit bacterial and viral binding to cell membranes? Also exhibits antifungal properties.
Lactoferrin
This antimicrobial enzyme kills bacteria via formation of reactive bromine and iodine species?
Lactoperoxidase (salivary)
What secretion offers lubrication and protection to teeth, tongue, and epithelial cells of the gums/inner mouth as well as the remainder of the digestive tract?
Mucus
Methamphetamine act of which receptors of the vasculature of salivary glands, causing vasoconstriction and reducing salivary flow?
Alpha-Adrenergic Receptors
What is the significance to reduced salivary flow?
Deprives oral environment of saliva’s buffering activity to counteract acidity and prevent demineralization of enamal
Methamphetamine overstimulates what portion of the Nervous system?
Sympathetic Nervous System
This overstimulation of the sympathetic Nervous system causes what?
Depleting of Norepi and dopamine, altering concentrations of serotonin, acetylcholine, and glutamate leading to increased demand for ATP
Users of Meth compensate by consuming more of what?
Carbohydrates (Sugars)
Decreased saliva, increase mouth acidity, excess sugar, and lack of plaque control (oral hygiene) leads to what?
Accelerated Dental Caries
Aside from the teeth providing mechanical breakdown of food, what else provides for mechanical breakdown?
Smooth muscle layers of the digestive tract
What portion of the Nervous system regulates and coordinates secretion of H ions and digestive enzymes?
Autonomic Nervous System and Hormones
The actions of each cell type and resulting environment of the stomach are controlled by?
Vagus (CN-X) Cranial Nerve signals
The activation and activity of a number of regulated enzymes is due to what?
Exposure to acid environment (pH 1-2) that initiates metabolism
What are the different cells types of the Gastric Mucosa?
Mucous Surface Cells
Mucous Neck Cells
Oxyntic (Parietal) Cells
Peptic (Chief) Cells
What are the secretory products of the Mucous Surface Cells and Mucous Neck Cells?
Mucus, Bicarb, water (Mucus (Neck) or Foveolar)
What are the secretory products of the Oxyntic (Parietal) cells?
H ions, Cl ions, intrinsic factor, water
Parietal (Oxyntic)
What are the secretory products of the Peptic (Chief) Cells?
Pepsinogen, water (Chief (Zymogenic))
What covers the inside of the stomach, forming a protective barrier from corrosive gastric acid and digestive enzymes?
Mucus-producing cells
What do the mucus-producing (Foveolar) cells produce?
Viscous mixture of protective enzymes and Mucins (large glycoproteins), via stimulation of C kinase
These are interlinked by Cysteine-Cysteine Disulfide bonds to form large aggregate gels filled w/buffered H2O and protect from enzymes by their dense carbohydrate coating?
Mucin Glycoproteins
Mucins have decreased glycosylation where in its AA sequence?
NH3 and COOH terminal ends
Mucins have increased glycosylation where in its AA sequence and via what?
Via: Serine, Threonine, and Asparagine AA’s
In: Central part of its AA sequence
Where are parietal (oxyntic) cells located?
Fundus of the stomach
What stimulates parietal (oxyntic) cells?
- Histamine
- Gastrin
- Vagus (Parasympathetic) Nerve
Via what receptor and name the sequences of stimulation for Histamine on Parietal (oxyntic) Cells?
Via H2 receptor
(Gs–> adenyl cyclase–> cAMP–>H+/K+ ATPase
active transport channel to produce gastric acid)
Via what receptor and name the sequence of stimulation for Gastrin on Parietal (oxyntic) Cells?
Via CCK2/gastrin receptor on ELCs
Gq–> Phospholipase C–> IP3–>Ca2+–> Histamine–> Parietal cells
Vagus (parasympathetic) Nerve via what receptors and name the sequence?
Via ACh and M3 receptors
Gq–> Phospholipase C–> IP3–> Ca2+
Parietal (Oxyntic) Cells secrete Gastric Acid (mainly H ions and Cl ions) is secreted via what?
H+/K+ ATPase active transport channel against high gradient (3M:1)
What role does gastric acid paly in digestion?
Denatures proteins
Activates Pepsinogen
Inhibits Bacterial Growth
Secreted Bicarb (HCO3-) secreted by Parietal Cells plays what role in digestion?
Excreted into blood to balance H+ pumped into stomach
What is required for absorption of Vitamin B12?
Intrinsic Factor (Secreted by Parietal Cells)
Chief (Zymogenic/Peptic) Cells produce what and this is a proenzyme form of what?
Pepsinogen, proenzyme form of Pepsin
(Cleaves peptide bonds at hydrophobic and aromatic (phe, trp, tyr) AA’s
Chief (Zymogenic/Peptic) Cells are stimulated by what?
Vagus Nerve
Acidic Conditions (Gastric Acid)
Hormones Gastrin or Secretin
Where are the hormones Gastrin and Secretin produced?
Duodenum
In infancy Chief Cells also produce what enzyme?
Rennin
What is the importance of Rennin?
Aids in milk absorption by breaking the phe-met peptide bond in milk protein (k(kappa)-casein)
What stimulates rennin secretion and what occurs later in life?
Stimulated by ingestion of milk by infant
-Gene is turned off later in life
Enterochromaffin-Like Cells (ELCs) are found where, secrete what, stimulated by, and inhibited by what?
- Found: Gastric Glands
- Secrete: Histamine activating parietal cells to increase gastric acid
- Stimulated: gastrin, pituitary adenyl cyclase-activating peptide and Vagus Nerve
- Inhibited: Somatostatin
G-Cells are found where, Secrete what to stimulate what cells and stimulated by what nerve?
- Found: Pyloric Antrum
- Secretes: Gastrin–> Stimulates parietal cells (w/histamine) to increase gastric acid and Chief cells to produce pepsin
- Stimulate: Parasympathetic Vagus nerve activity via release of gastrin-releasing peptide or increase AAs in stomach, increases gastrin
What receptors do Gastric Mucosal cells have?
PGE2 receptors
What function does Prostaglandin E2 binding to stomach receptors have?
- Stimulates smooth muscle contraction of GI
- Decreases parietal cell secretion of gastric acid
- Increases mucus production
PGE2 provides it function via what?
Gi protein receptor, which inhibits the production of cAMP by adenyl cyclase and therefore, parietal cell H+/K+ ATPase pump activity
What medication is a synthetically produced Prostaglandin E1, used in the prevention of gastric ulcers normally for treatment of/prophylaxis against nonsteroidal anti-inflammatory drug induced peptic ulcers?
Misoprostol
What medication are more effective for long-term care of acid reflux and similar disorders?
H2-receptor blockers
Proton Pump Inhibitor (PPI)
