Digestive System Lecture Flashcards
Alimentary Canal
(Gastrointestinal tract, GI)
A hollow tube that runs from mouth to anus. Maintaining homeostasis of the lumen in this canal is important.
Pathway of Alimentary Canal
oral cavity, pharynx, esophagus, stomach, small intestine, large intestine –> anus
Accessory Digestive Organs
Organs that mostly sit outside of alimentary canal and send substances to the lumen.
Examples: tongue, teeth, salivary glands, liver, gallbladder, and pancreas.
Ingestion
Taking food in at the oral cavity
Propulsion
Ability to move substances through the alimentary canal
Examples: swallowing and peristalsis
Mechanical Digestion
Using physical force to break apart large structures to smaller ones
Examples: mastication, segmentation, and churning
Churning
Using force to twist food inside the stomach into smaller substances
Chemical Digestion
Breaking chemical bonds in the foods that we eat using enzymes.
Purpose: to get to smallest absorbable form
Absorption
Allow nutrients and h2o from lumen in the alimentary canal to be absorbed by our blood/ lymphatics
Defecation
Ability to get rid of all indigestible and non-absorbable substances
Peristalsis
Type of propulsion; as smooth muscle in alimentary canal constricts, foodstuff gets moved
Segementation
Type of mechanical digestion; contracts smooth muscle nonadjacent walls in lumen so foodstuffs can collide and break apart
Layers of Alimentary Canal
-Mucosa (innermost)»_space;epithelium, lamina propia, & muscularis mucosae
-Submucosa
-Muscularis externa
-Serosa or adventitia (outermost)
Epithelium
In mucosa layer composed of non keratinized stratified squamous ET which can take damage.
Also composed of simple columnar ET w/ goblet cells
Lamina Propia
In mucosa layer composed of areolar CT w/ blood vessels, lymphatic vessels, nerves, and MALT
Muscularis mucosae
In mucosa layer composed of smooth muscle that can dislodge stuck particles
Submucosa
Made of areolar CT w/ blood vessels, lymphatic vessels, nerves, and MALT. Also contain submucosal nerve plexus
Musularis externa
Made of inner layer of circular and outer layer of longitudinal arranged smooth muscle. Also contain myenteric nerve plexus
Serosa
Is seen if organ is within abdominal cavity
Adventitia
Is seen in outer layer if organ is outside of abdominal cavity
Intrinsic Innervation
Comes from enteric nervous system.
Includes: submucosa plexus and myenteric plexus
Submucosa nerve plexus
(Occurs via intrinsic innervation)
Located in submucosa that regulates digestive secretion and reacts to the presence of food
Myenteric nerve Plexus
(Occurs via intrinsic innervation)
Located in muscularis mucosae that controls motility
Extrinsic Innervation
By autonomic nervous system.
Includes: SNS & PSNS
Sympathetic Nervous System
(Occurs via extrinsic innervation)
Inhibits the digestive process, “fight or flight”
Parasympathetic Nervous System
Digesting occurs, “rest & digest”
Short Reflexes
Involves the intrinsic nerve plexuses that occurs entirely within the gastrointestinal wall. Wall can sense change via receptors and respond accordingly with effectors such as smooth muscle or glands
Long Reflexes
Extrinsic innervation that involves CNS and ANS.
Enteroendocrine cells
Secretes GI hormones into the blood stream to travel to the target organ
Peritoneum
In abdominal cavity that contain serous membranes
Parietal peritoneum
Lines wall of abdominal cavity
Visceral peritoneum
Lines outer layer wall of organ
Peritoneal cavity
Between visceral and parietal peritoneum. Filled with peritoneal fluid to reduce friction of moving organs
Peritoneal fold
Mesenteries: double serous membrane that provides a pathway to get vessels and blood from posterior wall out to organs suspended within the abdominal cavity
Retroperitoneal organs
Located outside the peritoneum and most often in back body wall. Examples: kidney, spleen, and duodenum
Function of Peritoneal fold
Provide nutrients, oxygen, lymphatics, and nerves to organs that are suspended within the abdominal cavity
Mesocolon
A mesentery that attaches the transverse colon to the mesocolon
Greater omentum
Attaches the greater curvature to the transverse colon
Lesser omentum
Attaches the lesser curvature to the liver
Falciform Ligament
Attaches the right and left lobe of liver
Functions of oral cavity
Ingests food, mastication to create bolus, begins chemical digestion of carbs, and moves food to pharynx
Salivary amylase
A carb digesting enzyme secreted by salivary glands to start digestion
What is oral cavity lined in?
Lined in non keratinized stratified squamous ET for protection against heat, chemicals, and abrasion
Tongue
An accessory digestive organ that sits in oral cavity lined in non keratinized stratified squamous ET
Filiform Papillae
“spiky like structures” that gives surface grip. No taste buds.
Fungiform Papillae
Contains taste buds, located towards front of tongue
Vallate Papillae
10-12 of them in an inverted V located in back of tongue. Contain very deep crips with taste buds
Teeth location?
In mandible and maxilla
Dentin
Bone-like tissue that is avascular
Pulp cavity
Contain blood vessels and nerves that supply the teeth
Enamel
Covers crown of teeth. Hardest substance in body that contains hydroxyapatites
Function of teeth?
Mastication
Location of minor salivary glands?
Mouth and tongue
Loaction of major salivary galnds?
Outside oral cavity
Function of major salivary glands
Secrete saliva. EX: parotid glands, submandibular glands, and sublingual glands
Saliva composition
Mostly water (98-99.5%). Contain ions (bicarbonate, K+, Cl), salivary amylase, proteins (mucin, lysozyme, lgA), and nitrogen containing metabolic wastes
Digestion of carbs begins where?
In oral cavity because salivary amylase digest carbohydrates
Submandibular glands contain what cells?
Both serous and mucous cells
Parotid glands contain what cells?
Mostly serous cells
Sublingual glands contain what cells?
Mostly mucous cells
Function of minor salivary glands?
Keep mouth moist by secreting low volume of saliva
Taste receptors pick up?
Taste chemicals; leads to increase in saliva production
chemoreceptors pick up?
Chemicals in food we eat; leads to increase in saliva production
Mechanoreceptors pick up?
Can sense presence of food in the mouth; leads to increase in saliva production
Irritated G.I tract stimulates will cause?
Will increase salivation
Location of salivatory nuclei
Brainstem in pons
Parasympathetic impulses do what to oral cavity?
Produce more saliva in major glands
Sympathetic impulses do what to oral cavity?
Inhibit salivation resulting in dry mouth
Pharynx passage
mouth to oropharynx to laryngopharynx
Pharynx routes food and fluid to?
The epiglottis
Pharynx routes air to?
Larynx then trachea
What ET lines pharynx?
Non-keratinized stratified ET due to abrasion
Deglutition
Process of swallowing
Voluntary phase
Having concious control of swallowing via pushing tongue against roof of mouth and pushing bolus back
Pharyngeal phase
Involuntary controlled by medulla
Esophageal phase
Involuntary controlled by medulla.
Layers in esophagus?
Contains all 4 alimentary canal layers. Mucosa, submucosa, muscularis externa, and adventitia.
How many phases of deglutition?
3
Stomach functions
Mechanical digestion, chemical digestion, and can absorb very little
Pepsin
A protein digesting enzyme in stomach
Gastric lipase
A fat digesting enzyme in stomach
How does chyme form?
Stomach juices mix together with bolus to form pasty acidic chyme
Chyme is delivered to
C shaped duodenum
Function of rugae
Folded wrinkle bits covering entire stomach that can stretch or decrease in shape when empty
Mucosa layer in stomach contains
Gastric pits and gastric gland
Gastric pits are lined in?
Mucus cells that serve for mucous secretion
Gastric glands contain?
Gastric juice that is very acidic
Epithelium layer in stomach contains
Simple columnar ET w/ lots of goblet cells
Mucosal barrier
Contain surface barrier cells that secrete bicarbonate rich mucus to make environment less acidic. Cells are connected by tight junctions
Breakdown of mucosal barrier can lead to?
Peptic erosions and ulcers
Majority of ulcers caused by?
Excessive intake of non-sterodial anti inflammatory drugs EX: aspirin and Helicobacter pylori infection
Mucous neck cells
Are thin cells that contain acidic mucus and sit close to gastric pits
Parietal cells secrete?
Secrete hydrochloric acid and intrinsic factor
Purpose of HCL
Denatures proteins and changes structure via unfolding in parietal cells
Purpose of intrinsic factor
Needed to absorb vit B-12 in parietal cells
Chief cells secrete?
Secrete pepsinogen and gastric lipase
Purpose of pepsinogen
Activate propase to digest proteins in stomach in chief cells
Purpose of gastric lipase
Digests milk fats in chief cells
Enteroendocrine G cells
Secrete gastrin that travels in blood to stomach leading to an increase in gastric juice secretions
Phases of gastric secretion
1) Cephalic phase
2) Gastric phase
3) Intestinal phase
Cephalic phase
(head area) Before food has even entered the stomach
Cephalic phase pathway
Medulla + hypothalamus–> vagus nerve–> increased gastric secretions
Stimulatory events of cephalic phase
Smell, thought, taste, and sight of food. Communicate to PSNS
Inhibitory events of cephalic phase
Rotten food, food you dislike, depression, and loss of appetite
Stimulatory events of gastric phase
More proteins in stomach, high pH, and increase of caffeine. Communicate to enteroendocrine G cells
Inhibitory events of gastric phase
Sympathetic nervous system being stimulated
Intestinal Phase
3rd phase of gastric secretion.
Stimulatory events of intestinal phase
Enteroendocrine G cells in duodenum secrete intestinal gastrin that increase gastric juice
Inhibitory events of intestinal phase
Enterocendocrine cells in duodenum secrete CCK and secretin
Gastric filling
Reflective relaxation occurs in stomach coordinated by swallowing center of the brain stem. Is a stress relaxation response of smooth muscle
Peristaltic mixing waves
About 3 per minute occur and mix food with gastric secretion to create chyme. Are more powerful near pylorus
Gastric emptying
Rhythmic mixing waves force 3ml of chyme through pyloric sphincter
Stomach empties every?
In 2-4 hours. Carb rich chyme empties fastest and triglyceride rich chyme causes food to remain in stomach for 6+ hours
Secretory cells in gastric glands include? (4)
Mucous neck cells, parietal cells, chief cells, and enternoendocrine G cells
Liver
Largest gland in body consisting of 4 lobes
Name 4 lobes of liver
R and L lobe, quadrant lobe, and caudate lobe
Associated peritoneal lobes in liver
Falciform ligament and lesser omentum
Hepatic portals ? (3)
Hepatic artery, hepatic portal vein, and common bile duct
Hepatic Artery
Major artery delivering blood to the liver
Hepatic Portal Vein
Brings deoxygenated but nutrient rich blood from the digestive organs and portal that blood to liver to process nutrients
Common Bile Duct
Takes bile away from the liver all the wya to the duodenum
Hepatic Lobules
Hexagonal shaped structure in liver
Components of hepatic lobules? (3)
1) Hepatocytes
2) Bile canaliculi
3) Hepatic sinusoids
Hepatocytes
Liver cells
Bile Canaliculi
Allow for drainage of bile away from lobules into ducts
Hepatic sinusoids
(Permeable) Open spaces between hepatocytes where blood pools
Open area in lobule?
Central vein where blood travels to
Hepatocytes filter what?
Filter nutrient-rich blood
Portal triad location?
At corners of each liver lobule
Portal triad consists of? (3)
1) bile duct
2) branch of hepatic artery
3) branch of hepatic portal vein
Bile duct
Take bile away from a hepatic lobule
Branch of hepatic artery
Brings oxygenated blood into a sinusoid to be taken to central vein
Branch of hepatic portal vein
Brings deoxygenated but nutrient rich blood to the sinusoids
Kupffer cells
Fixed microphages in plates of hempatocytes. Phagocytize foreign cells
Liver functions
-Produce bile, cholesterol and lipoproteins, process bloodborne nutrients, store fat soluable vitamins, and perform detoxification
High density lipoproteins
(“Happy”) Transport fatty substances via bloodstream back to the liver for processing
Low density lipoproteins
(“Lousy”) Keep fats in bloodstream rather than taking to liver for processing. Contribute to plaque buildup
Glycogenolysis
Breaks down glycogen in liver
Gluconeogenesis
Uses fats and proteins to make new glucose in liver
Bile is made by?
Hepatocytes in liver towards duodenum
Color of bile
Yellow brown or yellow green alkaline solution
Bile contains
Water, electrolytes, bile salts, bilirubin, phosphates, and cholesterol
Bile salts
Cholesteral derivative
Lipid emulsification
Emulsify fats to keep droplets apart from each other and increase surface area. Occur in bile salts
Fat absorption
Coat digestive fat with bile salts to from micelles. Important for absorbing dietary fats
Bilirubin
Pigment produced from breakdown of hemoglobin due to heme metabolizing. Gives bile its pigment.
Stercobilin
Made by bacteria in large intestine and is what gives feces its brown color
Enterohepatic Circulation
Bile salts are reclaimed (recycled) by the enterohepatic circulation. Bile salts are picked up by capillary bed from the Ileum
Gallbladder
Muscular sac that stores and propels bile to the duodenum
Bile travels where in gallbladder?
Into cystic duct, to common bile duct, and into open sphincter
Pancreas
A retroperitonial organ located by C shaped duodenum
Exocrine function of pancreas
Produce enzyme rich pancreatic ducts by acinar cells and bicarbonate rich pancreatic juice by ducts
Endocrine function of pancreas
Secretes hormones via pancreatic islets to outside of body to regulate blood glucose levels
Pancreatic juice composition
Mostly water, salts, sodium bicarbonate to make pancreatic juice alkaline, and digestive enzymes
Pancreatic proteases are secrated in what form?
Inactive form that arrive from pancreas
Enteropeptidase
Brush border enzyme thats sits on microvilli
Trypsinogen
Is converted to trypsin via enteropeptidase
Trypsin
Once activated can convert Chymotrypsin into chymotrypsin and procarboxypeptidase into carboxypeptidase
Pancreatic enzymes are secreted in what form?
Active form activated in small intestine
Pancreatic amylase
chemically digest carbs
pancreatic lipase
chemically digest fats
ribonuclease and deoxyribonucleas
chemically digest nucleic acids
DNA to DNA nucleotides
RNA to nucleotides
CCK and secretin are produced where and by what ?
Duodenum by enteroendocrine G cells to travel in bloodstream
Secretin is secreted why?
in response to acidity of chyme in duodenum. Target stomach
CCK is secreted why?
In response to fats and proteins in chyme. Target stomach
Secretin target what
pancreas duct cells to increase bicarb ions, hepatocytes in liver to increase bile, and inhibits stomach activity
CCK target what
pancreas acinar cells to secrete more digestive enzymes, gallbladder to take bile to sphincter, hepatopancreatic sphincter to let bile and juice into duodenum, and hypothalamus to satisfy hunger
Small intestine regions
duodenum, jejunum, and ileum
Small intestine functions?
Mechanical digestion, chemical digestion, and absorption
Ways to increase surface area in small intestine?
circular folds, villi, and microvilli
Circular folds
increase surface area, slow chyme down and spiral as it hits walls of lumen
Villi
Contain blood capillaries and lacteals= specialized lymphatic capillaries
Microvilli
Brush border that are inside villi for even more surface area
Goblet cells produce what
Musin which become mucous
Dextrin
Broken down by brush border enzyme dextrinase into glucose
lactose
broken down by brush border enzyme lactase into glucose and galactose. In small intestine
sucrose
broken down by brush border enzyme sucrase into glucose and fructose
maltose
broken down by brush border enzyme maltase into glucose
Enterocytes
Absorptive cells that have microvilli with fixed brush border enzymes
EX: lactase, dipeptidase
Aminopeptidase
A brush border enzyme that breaks off amino acid from amine side of chain
Carboxypeptidase
Comes from pancreas. breaks off carboxyl chain in amino acid chain
Dipeptidase
A brush border that takes 2 proteins and cuts into 1 to be able to absorb in simplest form
Phosphates function
break the phosphate of nucleotide
Nuclosidases
breaks the nitrogen containing bond of nucleotide
Are there fat digesting enzymes in brush border?
No, only in pancreatic lipase from pancreas and lingual lipase
Enteroendocrine cells
In mucosa of small intestine that secrete hormones to blood; include intestinal gastrin, secretion, and CCK
Paneth cells
secrete defenses and lysozyme (antimicrobial)
Duodenal glands
bicarbonate rich mucosa in submucosa of duodenum
Peristalsis works how?
Each wave starts distal to previous wave.
Gastroileal reflex
increases force of segmentation to ileum. Causes iliocecal sphincter relaxation
gastrin secretion
increases motility in ileum. Causes iliocecal sphincter relaxation
Functions of large intestine
Finish absorption of water, synthesize vitamins, and eliminate feces
rectum
3 rectal valves help prevent simultaneous passage of feces and gas
Internal anal sphincter
part of muscularis externa layer, smooth muscle (no voluntary control)
External anal sphincter
Skeletal muscle (voluntary control)
bacterial flora
trillions of bacteria live within large intestine
Functions of bacteria flora
-ferment indigestible carbs, release irritating gases that create flatus, synthesize vit K, and keep pathogenic bacteria in check.
Semisolid feces contain
-undigested food residue, ET cells, millions of bacteria, mucus, stercobilin, and enough water for smooth passage
Haustral contractions
weak, sluggish contractions. Slow peristalsis. Initiated when food residue is in colon
Mass movement
strong contractions, initiated by the gastrocolic reflex when food is in stomach, and initiates defecation reflex
Kidney functions?
filter blood, regulate pH and blood pressure, regulate solute concentrations, endocrine function, and activate vit D
How to activate vit D
cholecalciferol (inactive vit d) to calcitriol (active vit d)
Fibrous capsule
(innermost) Made of dense irregular connective tissue that prevents kidney from risk of infection
Renal fat pad
adipose tissue that serves for cushioning, shock absorption, and protection of kidney
Renal fascia
(outermost) Thick and tuff that anchors kidney in place
Outer renal cortex
where majority of filtration occurs
Inner renal medulla
w/ renal columns, renal pyramids (for filtration), and renal papillae
renal lobes
renal pyramid + cortex
Calyx
Minor leads to major calyx and to renal pelvis
renal hilum
concave curvature where blood vessels and urine enter the kidney
Urine flow ?
Renal papilla to minor calyx to major calyx to renal pelvis to ureter—> take urine to urinary bladder
(once in minor calyx urine is destined)
Nephron functions
Filtration, reabsorption, and secretion.
-Takes filtrate of blood and modifies it into urine
Renal corpuscle
Sac like structures that creates filtrate
renal tubules
returns nutrients and fluids that have been filtered from the blood, but the body needs back in blood.
Renal corpuscle is made of ?
1) Glomerulus
2) Glomerulus capsule
Glomerulus
A capillary bed fed by larger afferent arteriole to smaller efferent arteriole = making a pressure
Glomerulus capsule
w/ parietal layer of simple sq. ET(innermost), capsular space (contains filtrate that is caught), and visceral layer
Visceral layer contain ?
podocytes with filtration slits
