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z PP1: Intro Physiology > GI Track Exam 6 > Flashcards

GI Track Exam 6 Flashcards

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1
Q

Digestive System: Continuous Tube

A

From mouth to anus
-mouth, pharynx, esophagus, stomach, small intestine, large intestine

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2
Q

Digestive system: Accessory Digestive Organs

A

Teeth, tongue, salivary glands, liver, gallbladder, pancreas
-Breakdown of food (teeth, tongue)
-Secretions into GI tract (salivary glands, liver, gallbladder, pancreas)
—Enzymes and mucous

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3
Q

Mucosa (inside)

A

Epithelium
Lamina propria is connective tissue
Musclaris mucosa -> thin layer of smooth muscle (small movement mucosal surface)

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4
Q

Submucosa

A

Connective tissue containing blood and lymph vessels
Network of neurons (submucosal plexus)

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5
Q

Muscularis External

A

-Circular (thick; narrowing the lumen) and longitudinal muscles (shorten the tube) in most of the tract
-Myenteric plexus (neurons) between muscle layer

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6
Q

Serosa (outside ab cavity)

A

Connective tissue -> connects serosa to ab wall

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7
Q

Enteric Nervous System (ENS): myenteric and submucosal plexus

A

Myenteric (Auerbach’s) Plexus:
Control motility

Submucosal (Meissner’s) Plexus:
-Innervates epithelial cells and smooth muscle of muscularis
-It senses the environment in the lumen -> control local secretion, absorption and local blood flow

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8
Q

Innervation of interneurons and sensory neurons

A

Interneurons:
-Integrate info from sensory neurons to motor neurons in plexus
Sensory Neurons:
-receives info from sensory receptors in mucosa and muscles

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9
Q

What is the overall function of the digestive system

A

Process ingested foods into molecular forms that can be absorbed and circulation can distribute them to cells

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10
Q

What are the 5 major processes of the digestive system

A

Secretion (cells in GI tract and accessory organs)
-Release of water, acid, buffers, and enzymes into lumen
-Food mix with the secretions

Digestion:
-Mechanical digestion by churning food (muscle contraction)
-Chemical digestion (enzymes) -> hydrolysis of food-producing smaller molecules

Motility:
-Muscular movements (wavelike) along part of the GI tract

Absorption:
-Molecular forms pass into blood or lymph

Elimination:
-Elimination of waste by defecation

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11
Q

Processes of the GI tract

A

-Absorption products of digestion, water, minerals, vitamins into blood
-Secretion of ions, enzymes, and bile salts into the GI tract
-Larynx and esophagus are not important in digestion, but muscles in the wall are involved in swallowing
-Small intestine is where most digestion, absorption, and secretion occurs

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12
Q

What does the mouth, esophagus, stomach, small intestine, colon, anus do?

A

Mouth: bolus formation starts digestion
Esophagus: moves bolus to stomach
Stomach: chyme formation, digestion and storage
Small intestine/Colon: absorption of water and alcohol (limited amount)
Anus: Waste elimination

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13
Q

Mechanical Digestion

A

Food grounded by teeth into smaller particles
Mixed with saliva and formed into a bolus (soft, rounded mass)

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14
Q

Chemical Digestion

A

Enzymes
-Salivary amylase
-Salivary or Lingual lipase

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15
Q

Enzymes in Saliva: salivary amylase, salivary or lingual lipase, lysozyme

A

Salivary amylase:
Activated by food (breakdown carbohydrates)

Salivary or Lingual Lipase:
Activity continues into stomach (breakdown of lipids)

Lysozyme:
Enzyme that kills bacteria -> protection of oral cavity (breakdown of proteins)

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16
Q

The stomach functions

A

-Dissolves and partially digests macromolecules
-Mixing chamber -> mixing saliva, good, gastric juice
-Bolus is converted into CHYME
-Storage -> reservoir for food before releasing it into the small intestine
-Regulated the rate at which it empties chyme into small intestine

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17
Q

What does secretion of mucus, gastric acid and intrinsic factors do

A

-Mucus and HCO3- -> protective glands
-Gastric acid (HCl) -> kills bacteria, denatures proteins
-Intrinsic factor -> Vit B12 absorption

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18
Q

What does the secretion of pepsinogen, gastric lipase, and gastrin do

A

-Pepsinogen originates pepsin that digests proteins
-Gastric Lipase -> triglycerides digesition
-Secretion of gastrin (hormone)
—Causes release of gastric acid
—Stimulates pancreas (enzymes), liver (bile), intestine (movement)

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19
Q

Acid Secretion by Parietal Cells: H+ and Cl- transport

A

Secrete H+ and Cl- separately into the lumen of the stomach and then HCL is formed in the gastric lumen

H+ comes from carbonic acid and are transported into the lumen of the stomach by H+/K+ ATPase

Cl- moves into cells in exchange for HCO3- using the Cl-/HCO3- antiporter

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20
Q

Regulation of gastric acid secretion in parietal cells

A

Acetylcholine -> released by parasympathetic neurons
Gastrin -> secreted from G cells
Histamine -> released by ECL cells

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21
Q

Direct Regulation of Gastric Acid

A

-Direct regulation involves the binding of ACh, gastrin and histamine to receptors on the surface of parietal cells
-Increase cAMP (histamine) and Ca2+ (Ach and gastrin) activate PKA
-PKA phosphorylates and activates H+/K+ ATPase -> production of gastric acid

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22
Q

Indirect regulation of gastric acid secretion: gastrin and ACh

A

Gastrin:
-gastrin activates CCK receptors on ECL cells

ACh:
-ACH activates M1 muscarinic receptors on ECL cells
-ACh release from neurons of the enteric system

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23
Q

What cells release histamine

A

ECL cells

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24
Q

Histamine activates H2 receptors on _________ cells -> production of _______ acid

A

parietal, gastric

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25
What is the main regulatory pathway in indirect gastric acid secretion
Gastrin - histamine pathway
26
______________-like cells are located in the gastric gland of the gastric mucosa -> close to ________ cells
enterochromaffin, parietal
27
Chemical Digestion in Stomach: Gastric Acid
Secreted by parietal cells secrete -> H+/K+ ATPase -gastric acid partially denature proteins -gastric acid activates pepsinogen and gastric lipase -pepsinogen (inactive molecule), secreted by chief cells, is activated to pepsin by HCl
28
Chemical Digestion in Stomach: what does pepsin do, how are triglycerides broken down
Pepsin breaks down peptide bonds Gastric Lipase together with lingual lipase break down triglycerides in the stomach
29
Chemical Digestion in Stomach: how are stomach cells protected
They are protected from acid by alkaline mucus produced by surface and neck mucous cells
30
Mechanical Digestion in Stomach: Mixing waves
Mixing -> several minutes after food enter stomach mixing waves pass over stomach every 15-25 seconds
31
Mechanical Digestion in Stomach: movements, peristaltic waves
-Propulsion and retropulsion movements -Peristaltic waves produced by pacemaker cells in the longitudinal smooth muscle -> signal is then passed to circular muscle
32
Mechanical Digestion in Stomach: Movements resulting in chyme
-Salivary amylase is inactivated and lingual and gastric lipases are activated in the stomach -Lower esophageal sphincter prevents stomach contents from entering the esophagus
33
Mechanical Digestion in Stomach: Gastric Emptying
Chyme passes through the pyloric sphincter 3 ml at a time
34
Small Intestine: absorption and secretion
Absorption of most nutrients Finishing the digestion of proteins, carbs, and lipids for absorption Secretion from accessory organs (pancreas, liver, gallbladder) to help with digestion
35
What are the three regions of the small intestine
Duodenum (short) Jejunum Ileum (longest)
36
What two parts of the small intestine cause chemical digestion and absorption of most nutrients
Duodenum and Ileum
37
Anatomy of the small intestine
Circular Folds: Folds of mucosa and submucosa in intestinal wall -> cause the chyme to spiral Villi: fingerlike projections of the mucosa that cover the folds Microvilli: -Small projections of the apical membrane of absorptive cells (enterocytes) on the surface of each villus -Known collectively as brush border
38
Special features of Villi center
Capillary Network (arteriole and venule) Lateral (lymphatic capillary) -Nutrients absorbed by the lateral reaches the general circulation from the lymphatic system into large veins
39
Epithelial Cells: Absorptive, globet, enteroendocrine, paneth cells
Absorptive Cells (enterocytes): Digestion and absorption Globet: Secrete mucous for lubrication and protection Enteroendocrine cells secrete: Secretin (HCO3-) Cholecystokinin (pancreatic and gastric secretion and gallbladder contraction) Paneth Cells (at the bottom): Secret Lysozyme Involved in phagocytosis
40
Brush-Boarder Enzymes: digestive enzymes, microvilli
-Digestive enzymes are synthesized by absorptive cells or enterocytes and inserted in the plasma membrane of microvilli -Microvilli form a fuzzy line called the brush boarder that extends into the lumen of the small intestine
41
Brush-Boarder Enzymes: enzymatic digestion and specific enzymes
-Some enzymatic digestion occurs at surface of enterocytes rather than in the lumen of the small intestine Enzymes: carb digesting, protein digesting (peptidases) & nucleotide digesting
42
Mechanical digestion and absorption in duodenum of small intestine
Mechanical Digestion: Peristalsis and segmentation movements (rapidly in duodenum or small intestine) Absorption: Digested food forms pass through the absorptive epithelial cells lining the mucosa into blood and/or lymphatic vessels
43
Peristalsis and Segmentation in mechanical digestion in small intestine
Peristalsis: pushing chyme forward by contracting cells behind (longitudinal cells) Segmentation: circular muscles contract breaking chyme into smaller pieces until chyme mixed with digestive juices
44
Accessory Organs in small intestine functions
Pancreas -> exocrine cells (acini) secrete pancreatic juice containing enzymes Liver -> secretes bile Gallbladder -> stores secreted bile between meals
45
Acini in pancreas
-99% of clusters -Glandular epithelial or acinar cell clusters -Exocrine portion of the organ secretes pancreatic juice with digestive enzymes
46
What is pancreatic secretions stimulated by
secretin and CCK
47
Pancreatic Secretions: Sodium Bicarbonate
Changes chyme to less acidic -> stop pepsin activity Important for activity of enzymes in small intestine
48
Pancreatic Secretions: Digestive Enzymes
Pancreatic Enzymes -> starch metabolism Trypsin, chemotrypsin, carboxypeptidase, elastase -> metabolism of proteins Pancreatic lipase -> metabolism of triglycerides Deoxyribonuclease & Ribonuclease -> nucleic acid metabolism
49
Pancreatic Enzymes
Inactive enzymes: Trypsin, chemotrypsin, carboxypeptidase, elastase Trypsinogen is activated to trypsin by enterokinase enzyme in small intestine and then activates the other peptidases
50
What is the liver functional unit
Hepatic Lobule -> contains cells or hepatocytes and portal triads with branches of the bile duct, hepatic and portal veins and hepatic artery
51
What do the Kupffer cells do in sinusoids in the liver
They are macrophages that destroy old WBCs and RBCs, bacteria and foreign matter
52
Hepatic artery brings _________ blood with ________ to the liver
oxygenated, nutrients
53
______ veins bring absorbed substances to the liver from the small intestine. _____ veins drain into the ________
portal, portal, sinusoids
54
Substances absorbed from the small intestine end up in the ________ ________
hepatic sinusoids -> can reach vena cava via the central vein or they are taken up by the hepatocytes to be processed
55
Eliminated substances and bile are secreted by the __________ into the bile _________, which form the common hepatic bile duct
hepatocytes, canaliculi
56
What is enterohepatic circulation
Recycling pathway from the liver to the intestine and back to the liver
57
What do the bile salts do in enterohepatic circulation
-Are secreted into the small intestine to digest a fatty meal, absorbed by the transporter in the ileum -Absorbed and taken to the liver via the hepatic portal vein to the liver -Then secreted back into the bile -Small amounts do not recycle -> eliminated in the feces and liver synthesizes more to replace them
58
Function of the gallbladder: bile
-Stores and concentrates the bile produced by the liver -Gallbladder muscle contracts when food enters releasing bile via the cystic duct into the common bile duct and duodenum -Bile emulsifies fats
59
Gallstones are ____________ that crystallized in the gallbladder
cholesterol
60
Digestion is completed in the small intestine by components in ...
pancreatic juice, bile, and intestinal juice
61
What do carbohydrates intake
Starch, disaccharide glucose, and lactose
62
What enzymes metabolize simple monosaccharides
Pancreatic Amylase and Brush Boarder Enzymes
63
How is fructose, glucose and galactose absorbed in carb digestion and absorption
Fructose -> absorbed into the cell by facilitated diffusion via glucose transporter Glucose and Galactose -> absorbed by active transport coupled to sodium Monosaccharides are absorbed across the basolateral membrane by facilitated diffusion
64
Protein Digestion
Starts in stomach by pepsin and continues in small intestine
65
What pancreatic juices enzymes need to be activated for protein digestion
Trypsin, chymotrypsin, and elastase -> cleave peptide bond between specific AA and its neighbor Carboxypeptidase -> Splits off the AA at the carboxyl end of a peptide (also in brush border)
66
Brush-boarder peptidases in protein digestion
They complete protein digestion Aminopeptidase cleaves AA at the amino end of a peptide Dipeptidase splits dipeptides into single AA Carboxypeptidase
67
Protein Absorption
Amino Acids enter absorptive cells via Na+ dependent active transporter Small peptides use secondary active transport with H+ - peptides are then hydrolyzed to single AA in the cell Animo Acids move out of the cell (basolateral) via facilitated diffusion via different specific transporter -They are transported to the liver and then to circulation
68
Emulsification of Lipids (small and large droplets)
-Lipids are insoluble in water and aggregate into large lipid droplets -Pancreatic lipase is a water-soluble enzyme and works only at the surface of droplets -Large droplets are divided into many very small droplets -> increase lipase action and rate of digestion -Needed for emulsification -Mechanical disruption of large droplets -> GI tract motility -Emulsifying agent (prevents reaggregation of smaller droplets) -> phospholipids and bile salts in bile and phospholipids in food
69
Formation of Micelles
-Formation of micelles increases the rate of absorption of water-insoluble products of the lipase reaction -Micelles are similar to emulsion droplets but much smaller -Micelles consist of bile salts, fatty acids, monoglycerides and phospholipids in a cluster -Non-polar portion forms the micelle core, where there is also vitamins and cholesterol -Micelles are in equilibrium with fat digestion product (free in solution) -> individual molecules release from the micelles are absorbed
70
Lipids and Bile Salts Absorption
-Fatty acids and monoglycerides enter the enterocytes -In the cell, fatty acids and monoglycerides are used to resynthesize triglycerides in smooth ER -Triglycerides combine with phospholipids, cholesterol and lipid-soluble vitamins and then coated with proteins forming lipoprotein known as chylomicron -Chylomicron are released from cells -Bile salts are reabsorbed and go back to the liver
71
Chylomicrons Absorption
-Chylomicrons are extruded from the cells -They enter lacteals of the villi and are transported away from the intestine -Chylomicron-rich lymph then drains into the lymphatic system, which rapidly flows into the blood
72
Electrolytes and Nutrients Absorption
Sodium Ions: diffusion, actively transported out by Na/K ATPase Bicarbonate, Cl, I, N: passively follow sodium or actively transported Ca: Active transported stimulated by calcitriol (active Vit D) Fe, K, Mg, P: Active transport Vitamins: -Fat-soluble vitamins (A,D,E,K), ingested with dietary lipids in micelles, simple diffusion -Water soluble (B,C), simple diffusion, vitamin B12 combines with intrinsic factor (active transport in ileum) Water: Via osmosis following concentration gradients
73
Functions of Large Intestine
Large intestine (colon) is much wider and shorter than the small intestine Lacks digestive enzymes and secretions contain mucus and fluid with HCO3 and K Function is to absorb water, salts, and vitamins and remove solid waste -> time of food in here is important
74
Final stages of digestion
Chyme is prepared for elimination by the action of bacteria present in the cells -Ferment carbs (not digested in small intestine) ---Release hydrogen, CO2, methane gases -> causes flatulence (excessive gas) Break amino acids into indole, skatole, hydrogen sulfide Decompose bilirubin into stercobilin Produces vitamins (B and K) -> absorption
75
Absorption and Feces Formation
Chyme remained in the large intestine and becomes solid or semi-solid due to water reabsorption -> feces
76
What does feces consist of
Water, inorganic salts, sloughed epithelial cells, bacteria, products of bacterial decomposition, unabsorbed digestion material, indigestible parts of food
77
Absorption Pathways
-Fats enter the lacteal where lymph vessels empty in a large vein near the heart -> chylomicrons deliver content to body cells -All other absorbed nutrients move to intestinal capillaries then to veins -Venous drainage from small and large intestine, pancreas and portion of stomach goes to the liver through the portal vein -Liver can process these materials if needed -In the liver the blood goes into capillaries and then leaves for the heart
78
Problems with lipid digestion
Lipids in food present as large globules -> it is difficult for lipase to act on them Lipids are hydrophobic, and poorly soluble in the aqueous environment of the GI tract Lipase (water soluble) only works at the surface of fat globules -> low rate and efficiency
79
Emulsification process -> solution
During emulsification, the large globules break down into smaller globules -> bile is important Smaller globules are held in suspension Lipase can act on larger surface area -> increase the efficiency of lipid digestion

z PP1: Intro Physiology (10 decks)

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