Digestive system Flashcards
List the organs of the alimentary canal
Mouth Pharynx Esophagus Stomach Small intestine Large intestine
List the accessory digestive organs
Teeth Tongue Gallbladder Salivary glands Liver Pancreas
List the 6 essential digestive processes
Ingestion Propulsion Mechanical digestion Chemical digestion Absorption Defecation
Describe peristalsis
Waves of contraction/ relaxation of muscles
Describe segmentation
Local constrictions of the intestines
Describe chemical digestion
Catabolic breakdown of food
Describe absorption
Movement of nutrients from GI Tract to blood/ lymph
Where does chemical digestion take place
Mouth
Stomach
Small intestine
What are the circulation systems to the digestive organs
Splanchnic circulation
Hepatic portal circulation
Describe Splanchnic circulation
Aorta Celiac trunk Hepatic Splenic Left gastric Inferior/ superior mesenteric
What is the function of the hepatic portal circulation
Collect nutrient rich blood
Deliver it to the liver for processing/ storage
Name the 4 tunics of the alimentary Tract
Mucosa
Submucosa
Muscularis externa
Serosa
Functions of mucosa
Secrete mucus
Absorption
Protection
What are the layers of mucosa
Epithelium- simple columnar
Lamina propria- areolar and reticular
Muscularis mucosae- smooth miscle
What do the mucosa of stomach and small intestine contain
Enzyme secreting cells
Hormone secreting cells
What is the function of the mucosa lamina propria
Nourish the epithelium
Absorption
Contain MALT
Where does the serosa get replaced by adventitia
Esophagus
What does the submucosa contain
Elastic fibers Blood Lymph vessels Lymph nodes Nerves
What does the enteric nervous system consist of
2 intrinsic nerve plexuses
- submucosal
- myenteric
What does submucosal nerve plexus regulate
Glands
Smooth muscle of mucosa
What does myenteric nerve plexus regulate
Control of GI mobility
Function of the intrinsic tongue muscles
Change the shape
Function of the extrinsic tongue muscles
Alter position
What are the 3 types of tongue papillae
Filiform
Fungi form
Circumvallete
What makes the tongue rough
Filiform papillae
Gives tongue reddish hue
Fungiform papillae
In the back of the tongue
v shaped row
Circumvallete papillae
Function of saliva
Clean mouth Moisten food Dissolve food Bolus formation Breakdown starch- amylase Contain mucin, lysozyme, Defensins,IgA
Name an intrinsic salivary gland
Function
Buccal gland
Keep mouth moist
Name some extrinsic salivary glands
Function
Parotid
Submandibular
Sublingual
Secrete enzyme rich saliva
What do extrinsic salivary glands respond to
Ingested food stimulating chemoreceptors and pressoreceptors
Thought of food
What inhibits salivation
Sympathetic stimulation
What is enamel made of
Acellular material
Calcium salts
Hydroxyapatite crystals
What is cementum
Calcified connective tissue that covers tooth root
Attaches to periodontal ligament
What is Dentin
Forms bulk of tooth
Bonelike material
What is pulp
Connective tissue
Blood vessels
Nerves
Inside of tooth
What are dental caries
Demineralization of enamel and Dentin by bacteria
Acid produced by bacteria dissolves calcium salts
What happens to organic matter without calcium salts
Proteolytic enzymes digest organic material
Why is calculus bad
Disrupts seal between teeth an gingivae
What is periodontitis
gum disease
Inflammation response
What are the 2 skeletal muscle layers of the pharynx
Inner longitudinal
Outer pharyngeal constrictors
Where does the esophagus extent from and go to
From laryngopharynx to cardiac orifice
Through the mediastinum/ diaphragm
What happens to mucosa from esophagus to stomach
Stratified squamous to simple columnar
What type of chemical digestion takes place in the mouth
Salivary amylase breakdown starch
What are the 2 phases of deglutination
Buccal phase
Pharyngeal esophageal phase
Describe buccal phase
Bolus is voluntarily forced into oropharynx
Describe pharyngeal esophageal phase
Controlled by medulla/ pons
Close airways
Open digestive ways
What lets food enter stomach
Gastroesophogeal cardiac sphincter opening
Where is food converted to chyme
Stomach
What makes up the pyloric region of the stomach
Antrum and canal
Terminate at pyloris
Describe mesentaries
Double layer of peritoneum fused
Where is lesser omentum
From liver to lesser curvature
Where is greater omentum
Greater curvature to small intestine
What type of mucus is in stomach from goblet cells
Thick alkaline mucus
Traps bicarbonate rich fluid beneath it
Where are gastric glands
In gastric pits
What do the gastric glands secrete
Mucus
Gastric juice
Gastrin hormone
List the 4 types of cells in the stomach glands
Mucous neck cells
Parietal
Chief
Enteroendocrine
Mucous neck cells secrete
Thin Acid mucus
Parietal cells secrete
HCL
Intrinsic factor
Chief cells secrete
Pepsinogen
Enteroendocrine cells secrete
Gastrin into lamina propria ( not lumen)
How is Pepsinogen activated
By HCL and pepsin
What keeps stomach from digesting itself
Bicarbonate rich mucus layer
Epithelium with tight junctions
Damaged cells replaced quickly
Functions of the stomach
Store food Degrade food Deliver chyme to small intestine Enzymatic ally digest protein with pepsin Secrete intrinsic factor
What regulates gastric secretion
Neural and hormonal controls
What are the 3 phases of gastric secretion regulation
Cephalic
Gastric
Intestinal
Function of the Cephalic phase
Prepares stomach for food
What occurs during Cephalic phase
Parasympathetic- vagus
Stimulate submucosal enteric plexus
Activate mucus, parietal, chief, and G cells
Function of gastric phase
Enhance secretions
Homogenize and acidify chyme
Initiate protein digestion by pepsin
What is the neural response of the gastric phase
Stretch/ chemoreceptors stimulate submucosal plexus as myenteric plexus
What is the hormonal response of gastric phase
Presence of peptides or caffeine stimulate Gastrin
Gastrin stimulates parietal/ chief cells
What stimulates HCl secretion
Ach- neural
Gastrin- hormonal
When is HCL release low
If only one ligand binds to a parietal cell
When is HCL release higher
If both Ligands bind to parietal cells
Hormonal/ neural stimulation
What happens to Cl during HCL secretion
Cl transported into stomach lumen
Maintain electrical balance
What happens to bicarbonate during HCL secretion
Bicarbonate ejected into capillary blood
What is the alkaline tide
Blood leaving the stomach is more alkaline than blood entering it
When does the intestinal phase begin
When chyme enters the small intestine
Describe what stimulates intestinal phase
Enterogastric reflex Distension of duodenum Acid- low ph Lipids Partially digested proteins
What occurs when the intestinal neural response is stimulated
Gastric contractions are inhibited
Pyloric sphincters close
What occurs during hormonal response of the intestinal phase
Release of enterogastrones
Inhibit gastric secretion
What are the enterogastrones
Cholecystokinin
Secretin
Vasoactive intestinal peptide
What is the rate of gastric contractions of peristalsis
3 per min Basic Electrical Rhythm
Toward pyloric valve
What increases stomach contractions
Distension of stomach wall
Activated chemoreceptors
What inhibits Gastrin and pepsin as chyme enters duodenum
Neural enterogastric reflex
Hormonal mechanisms- enterogastrones
Where do the bike duct and main pancreatic duct join duodenum
Hepatopancreatic ampulla
Controlled by Oddi
What do the villi of small intestine contain
Capillary bed
Lacteals- lymph
What makes up the brush border
Microvilli and enzymes
What is small intestine mucosa made of
Absorptive columnar cells
Goblet cells
Enteroendocrine cells
What is another name for intestinal crypts
Crypts of lieberkuhn
What do intestinal crypts secrete
Intestinal juice
Enzyme poor watery mucus
rapidly dividing stem cells
What do brunners glass secrete
Where are they
Alkaline mucus
Duodenum
List the lobes of the liver
Right
Left
Caudate
Quadrate
What does the Falciform ligament do
Separate right/ left lobes
Suspend liver from the diaphragm
Function of ligamentum teres( round)
Remnant of umbilical vein
Along edge of Falciform ligament
Where do hepatic artery/ vein enter liver
Porta hepatis
Where does arterial/ venous blood mix in liver
Sinusoids
What forms the central vein
Sinusoids converging
What are lobules made of
Hepatocytes
What is the triad made of
Bike duct
Hepatic artery
Hepatic portal vein
Describe sinusoids
Leaky capillaries between hepatic plates
House kupffer cells
Function of hepatocytes
Bile production
Processing blood borne nutrients/ toxins
Storage of fat soluble vitamins
Describe bile
Alkaline solution with bile salts and pigments
What do bile salts derive from
Cholesterol
What is the function of bile salts
Emulsify fat
Facilitate fat and cholesterol absorption
Help solublize cholesterol
How is bile recycled
Enterohepatic circulation
Absorbed in blood in the ilium
Return to liver via hepatic portal blood
What is main pigment in bile
Bilirubin
What causes release of bile
Acidic fatty chyme in duodenum - CCK and secretin Into blood
Bile salts and secretin stimulate bile production
What does CCK. Cause
Contractions of gallbladder
Hepatopancreatic sphincter to relax
What does pancreatic juice consist of
Enzymes
bicarbonate ions
What makes pancreatic juice
Acinar cells
What form are pancreatic enzymes released in
Inactive
Activated in duodenum
What is the function of pancreatic water solution and HCO3
Neutralize acidic chyme
Optimal ph for enzymes
Examples of inactive forms of pancreatic enzymes
Trypsinogen- trypsin
Procarboxypeptidase- carboxypetidase
What enzymes does the pancreas secrete in active form
Amylase
Proteases
Lipase
Nuclease
What are zymogens
Inactive enzymes
What activates trypsinogen
Enterokinase in duodenum
Then trypsin activates other enzymes
Example of proteases
Procarboxypeptidase
Chymotrypsinogen
What regulates pancreatic secretions
Parasympathetic nervous system
Local hormones
How does secretin regulate pancreas
Released in response to acid
Stimulates release of bicarbonate
Inhibits Gastrin
How does CCK regulate pancreatic secretion
Released in response to proteins/ fat
Stimulates release of digestive enzymes
What condition is chyme that enters the duodenum in
Hypertonic
Low ph
Carbs/ protein partially digested
No fat digested
What initiates segmentation in small intestine
Cajal pacemaker cells
Faster at duodenum
What is the migrating motility complex
Each wave of peristalsis is distal to the previous
What is function of large intestine
Absorb remaining water
Elimination
What are teniae coli
3 bands of longitudinal smooth muscle in Muscularis externa of lg intestine
What are epiploic appendages
Fat filled pouches of visceral peritoneum
What is the difference in internal/ external anal sphincters
Smooth vs skeletal muscle
Involuntary vs voluntary
How many valves does the rectum have
Function
3 valves
Prevent feces from passing with gas
What is large intestine lacking
Circular folds
Villi
Microvilli
What does large intestine have more of
Mucosa thickness
Crypts
Goblet cells
Function of anal sinuses
Excuse mucus
Compress feces
What is associated with the anal canal
Superficial venous plexuses
What happens when superficial venous plexuses are inflamed
Itching
Varicosities- hemorrhoids
Where do Colon bacteria come from
Survive through small intestine
Trough anus
Function of enteric bacteria
Ferment indigestible carbs
Release gas and acid
Synth B/ K vitamins
Compete with pathogens
What 2 types of movements occur in the large intestine
Haustral contractions
Mass movements
What stimulates haustral contractions
Distension
What stimulates mass movements
Gastrin
Slow powerful contraction
Just after eating
Describe defecation
Stretching of rectum- defecation reflex
Sensory nerves to spinal cord
Parasympathetic fibers relax internal sphincter
Voluntary control of external
Function of mesentery
Vascular and nerve supply to viscera
Hold organs in place
Store fat
What is another name for peritoneal organs
Mesocolons
List intraperitoneal organs
Small intestine
Transverse
Sigmoid colon
Where Does protein digestion begin
The stomach
Acid denatures
Pepsin converts proteins to peptides
Describe protein digestion in small intestine
Trypsin/ chymotrypsin- peptide fragments
Carboxypeptidase- remove single amino acids from carboxy terminus
Describe the brush border
Aminopeptidase
Carboxypetidase
Dipeptidase- cleaves last 2 aminos
How are proteins absorbed
Single aminos transported into epithelial cells
Aminos enter blood capillaries if villi
Transported to liver
Where is carbohydrate digestion started
Mouth
Amylase
What does amylase do
Starch into maltose
Describe carb digestion
Amylase- mouth/ sm intestine
Maltase, sucrase, lactase- sm intestine
Maltase
Breaks maltose into 2 glucose
Sucrase
Sucrose into glucose and fructose
Lactase
Lactose into glucose and galactose
Describe carbohydrate absorption
Monosaccharides into epithelium
By transporters
Into capillary blood of villi
To liver
Where does lipid digestion begin
Stomach
Describe lipid digestion
Stomach- mechanical
Small intestine- bile salts emulsify
Pancreas- lipase
What does lipase do
Digest triglycerides Into fatty acid and monoglycerides - micelles
Lipid absorption
Fatty acids/ monoglycerides leave micelles Diffuse across epithelium SER triglycerides are reformed Associated with protein Endocytosed Taken into lacteals
What is a chylomicron
Triglyceride with protein
How are nucleic acids absorbed
Active transport via membrane carriers
Villi
Liver
Where is most water reabsorbed
Small intestine
By osmosis
Metabolism
All chemical reactions necessary for life
Anabolic
Synth larger from smaller
Catabolic
Hydrolysis of structures to smaller ones
Cellular respiration
Catabolic
Glucose broken down to capture energy- ATP
3 major stages of metabolism
Digestion
Anabolism and formation of catabolic intermediates
Oxidative breakdown
Examples of oxidation
Rusting of iron
Burning of hydrogen
Oxides form
Example of reduction
Remove oxygen from metal oxide ores
Oxidation
Lose electrons
Reduction
Gain electrons
Reducing agent
Electron donor
Oxidized
Loses electrons
Oxidizing agent
Electron acceptor
Reduced
Gains
What happens to glucose and oxygen
Glucose oxidized
Oxygen reduced
2 important coenzymes
Flavin adenine dinucleotide FAD
Nicotinamide adenine dinucleotide NAD
What are the 3 carb metabolism pathways
Glycolysis
Krebs
ETC
Oxidative phosphorylation
Main points of glycolysis
Glucose oxidized into pyruvic acid
NAD to NADH
2 ATP
Where does the Krebs cycle take place
Mitochondrial matrix
What Are products of Krebs cycle
Co2 released
NAD to NADH
FADH
ATP
How many steps does Krebs have
8 steps
What occurs during Krebs
Acetyl coA is rearranged- keto acids
Decarboxylated
And oxidized
Where Is the ETC
Inner Mitochondrial membrane
How does oxidative phosphorylation work
H pumped into inner membrane space
Diffuses back via ATP synthase
What type of process is oxidative phosphorylation
Chemiosmotic process
Movement of substances across membrane couples reactions
What is glycogenesis
Formation of glycogen
Excess glucose
What promotes glycogenesis
Insulin
Through phosphorylation of glucose
What areas are most active in glycogenesis
Liver
Muscle
What is glycogenolysis
Breakdown of glycogen to replenish glucose levels
Glycogenolysis promoted by
GH
Glucagon
Glycogenolysis inhibited by
Insulin
What does glycogenolysis produce in most cells
In liver
Cells- glucose6 phosphate trapped in cells
Liver- free glucose
What is gluconeogenesis
Formation of sugar from noncarb molecules
What inhibits gluconeogenesis
Insulin
Promotes gluconeogenesis
Glucagon
Glucocorticoids- cortisol
Where does gluconeogenesis occur
Why
Liver
Protect brain
Ensure there is ATP
What is lipolysis
Catabolism of fat by 2 pathways
What 2 lipolysis pathways ate there
Glycerol
Fatty acid pathway
Describe glycerol lipolysis
Glycerol converted to glyceraldehyde phosphate
Then acetyl coA
Krebs
Describe fatty acid lipolysis
Fatty acids undergo beta oxidation
Then 2 carbon acetic acetyl coA
Krebs
What must be present for fatty acids to enter Krebs
Oxaloacetic acid
What happens when carbs are deficient
Oxaloatic acid converted to glucose
What happens without Oxaloacetic acid
Acetyl coA is converted into ketones in liver
What happens from ketone accumulation
Ketosis
Ketones in urine
Metabolic acidosis
Breathing increases to blow off carbonic acid
What causes carbohydrate deficiency
DM
Starvation
Dieting
Describe lipogenesis
Excess dietary glycerol and fatty acid form triglycerides
Why is glucose easily converted to fat
Acetyl coA is a glucose catabolism intermediate
Acetyl coA is start for synth of fatty acids
What type of cells synthesize phospholipids
All cells
What type of lipids are synthesized in the liver
Cholesterol
Lipoproteins for transport
Cholesterol from acetyl coA
Help form bile salts
What does excess dietary protein result in
Amino acids oxidized
Converted to fat
What must happen to amino acids prior to oxidation
Deaminatation
What are deaminated amino acids converted into
Pyruvic acid
Keto acid intermediate of Krebs
What happens to amine group during protein metabolism
Released as ammonia
Combined with CO2 in liver
Excreted as urea
What is the nutrient pool
Body’s total supply of nutrients
Can be interconverted
What is the absorptive state
Time during/ right after nutrient intake
What is post absorptive state
When GI tract is empty
Energy supplied by body reserves
What occurs during absorptive state
Anabolism
Energy storage
Glucose is major fuel
Excess aminos are deaminated and used/ stored
Absorptive in muscle
Amino acid- protein
Glucose to glycogen
Absorptive in liver
Amino acid- protein/ keto acid
Glucose- glycogen/ fat
Absorptive in adipose
Glucose/ fat converted and stored
What stimulates insulin release
Increased blood glucose Elevate amino acid levels Gastrin CCK Secretin
What does insulin enhance
Active transport of amino acids into cells
Facilitated diffusion of glucose into tissue
What occurs during post absorptive state
Catabolism
Replace fuel into blood
Glucose from glycogenolysis/ gluconeogenesis
Fatty acid/ ketones are major fuel supply
Amino acids converted to glucose in liver
Post absorptive in muscle
Protein broken into aminos
Glycogen converted to ATP/ pyruvic acid
Post absorptive in liver
Amino, pyruvate, glycogen. Converted to glucose
Fat into keto acids for ATP
Where can you get glucose from directly
Liver
Not muscle
Why don’t low carb meals cause hypoglycemia
Glucagon and insulin secreted together
What stimulates glucagon secretion
Decrease blood glucose
Elevated aminos acid levels
Glucagon stimulates
Glycogenolysis
Gluconeogenesis
Fat breakdown from adipose
Glucose sparing
What does low plasma glucose stimulate
Epinephrine release
Act on liver, muscle, adipose to promote glycogenolysis