Digestive System (Exam 3) Flashcards
What are the 6 functions of the digestive system?
Ingestion Secretion Mixing/Propulsion Digestion Absorption Defecation
What is digestion?
The actual breakdown of material
What are the two types of digestion?
Mechanical digestion and Chemical digestion
What is mechanical digestion?
The mashing up of food
What are the two main groups of Digestive organs?
GI Tract organs and Accessory organs
What are the organs of the GI Tract?
Stomach Anus Mouth Pharynx Large Intestine Esophagus Small intestine
SAMPLES (the “cavity” organs)
What are the Accessory organs of the digestive system?
Teeth Tongue Salivary Glands Liver Gallbladder Pancreas
TTSLGP
What are the GI Tract layers from inner to outer?
Mucosa
Submucosa
Muscularis
Serosa
Mucosal layer is tissue that is open…
… to the environment.
Is the mucosa well vascularized?
No
What are the three layers of the Mucosal Lining?
Epithelium
Lamina propria
Muscularis Mucosae (smooth muscle)
Does the tissue type of the mouth differ from the tissue type of the Intestines?
Yes
As the GI Tract organs descend from the mouth to the intestines, what tissue change occurs?
In the mouth the epithelium of the mucosal tissue is stratified squamous which is thicker and offers mostly protection and by the time it descends to the intestines, the tissue is simple columnar epithelium which is thinner and offers mostly absorption.
What is the thickness and purpose of stratified squamous epithelium?
Stratified squamous epithelium is very thick and offers protection
What is the thickness of simple columnar epithelium and its purpose?
Simple columnar epithelium is comparatively thinner that stratified squamous epithelium and its purpose is absorption.
What type of tissue is found in the mouth?
Stratified squamous epithelium
What type of tissue is found in the intestines?
Simple columnar epithelium
What type of tissue is the submucosal layer made of?
areolar connective tissue
What is the muscularis layer made up of?
Higher up in the digestive system there is skeletal muscle, but mostly smooth muscle in the lower portions
What is the muscularis layer responsible for?
Mixing and propulsion
What is the serosa?
the visceral layer of the peritoneum
The parietal layer of the peritoneum is located…
… on the abdominal wall
How is the digestive system innervated?
via the enteric nervous system
Is the enteric nervous system part of the autonomic nervous system?
Yes
The myenteric plexus is responsible for…
… mobility
Myo- means…
muscle
The submucosal plexus is responsible for…
stimulating the glands
The myenteric and submucosal plexus are connected by…
interneurons
The enteric nervous system is regulated by…
… the autonomic nervous system
Parasympathetic innervates or inhibits?
innervates
Sympathetic innervates or inhibits?
inhibits
What is the peritoneum?
It is the largest serous membrane that has five major folds and is parietal and visceral
Is the peritoneum all one structure?
yes
What are the five major folds of the peritoneum?
Greater omentum Falciform ligament Lesser omentum Mesentery Mesocolon
What is the purpose of the folds of the peritoneum?
the folds keep everything suspended in place rather than gravity causing everything to jumble up
What is the purpose of the greater omentum?
it’s a big area for lymph nodes and collects adipose tissue
What is the purpose of the falciform ligament?
it attaches the liver to the diaphragm
What is the purpose of the lesser omentum?
To suspend the stomach and duodenum from the liver
What is the purpose of the mesentery?
to suspend the small intestine from the posterior wall
What major folds of the peritoneum has blood vessels and lymphatic organs/vessels running to and from it?
Mesentery and mesocolon
What is the purpose of the mesocolon?
It suspends the large intestine from the posterior wall; it is what the mesentery is to the small intestine
What are the 4 functions of the mouth?
Ingestion
Mastication
Beginning of chemical digestion
Movement of bolus to oropharynx
What is mastication?
Chewing
Where does starch begin to break down?
The mouth
Define bolus
a wad of food
What are the accessory organs of the mouth?
Salivary glands
Tongue
Teeth
What are the 3 salivary glands?
Parotid
Submandibular
Sublingual
What are the two major components of the tongue?
Papillae and lingual frenulum
What kind of muscle is the tongue made of?
Skeletal muscle
How many deciduous teeth are there?
20
How many permanent teeth are there?
32
What are the four types of teeth present on the upper and lower jaw?
Incisors
Canines
Bicuspid
Molars
How many incisors are there per jaw?
4
How many canines are there per jaw?
2
How many bicuspids are there per jaw?
4
How many molars are there per jaw?
4-6
Are mouth glands endocrine or exocrine glands?
Exocrine
What does exocrine mean as it relates to glands?
They are glands that have ducts which deliver fluid directly to the local area
Mechanical digestion is driven by…
… mastication
Mastication includes what structures/fluids?
Tongue
Teeth
Saliva
Creates a bolus
What are the enzymes released in the mouth?
Salivary amylase and Lingual lipase
What does salivary amylase do?
breaks down starches to disaccharides like maltose, alpha dextrins
Where is salivary amylase released and where is it active?
It is released in the mouth and active there as well
What does lingual lipase do?
It breaks down triglycerides to fatty acids and diglycerides; breaks down lipids
Where is lingual lipase released and where is it active?
Released in the mouth and activated in the stomach
What is gustation?
Taste
What are some other functions of saliva besides chemical digestion?
Destroy bacteria via Lysozyme, IgA
Lubricate food via mucus
Remove waste
Aid gustation (water)
The upper esophageal sphincter is made of what type of muscle?
Skeletal muscle
The lower esophageal sphincter is made of what type of muscle?
Smooth muscle
What structure does the bolus pass through via the diaphragm?
the esophageal hiatus
What is deglutition?
swallowing
What are the three stages of deglutition?
Voluntary stage
Pharyngeal stage
Esophageal stage
Define peristalsis
the symmetrical contraction and relaxation that propagates in a wave down a tube ie the esophagus
What kind of mechanical digestion occurs in the stomach?
Mixing waves that produce chyme and promote gastric emptying
What is chyme?
“paste-like” material
What is pepsin?
an enzyme activated by the acidic environment in the stomach that turns proteins into smaller peptides; pepsin is initially pepsinogen until activated by the HCl in the stomach
What is absorbed in the stomach?
Water
Ions
Fatty Acids
Some drugs and alcohol
What kind of glands are gastric glands?
exocrine glands
What do gastric glands do?
release gastric juice
What is gastric juice composed of?
HCl
Pepsin
Gastric lipase
Mucous
HCl in gastric juice serves what two purposes?
kills microbes
converts pepsinogen to pepsin by providing an acidic environment
What does gastric lipase do?
breaks down triglycerides to fatty acids and monoglycerides
What does mucous in gastric juice do?
protects stomach lining from acids and digestive enzymes, etc
What type of gland is the pancreas?
Endocrine and exocrine, though only certain portions of the organ do one or the other
What two hormones do the pancreatic islets produce?
insulin and glucagon
What does insulin do?
lowers blood sugar
what does glucagon do?
increases blood sugar
What side of the pancreas produces insulin and glucagon
the endocrine side
what is the exocrine protion of the pancreas called?
acini
is the pancreas a critical organ?
yes
what is in pancreatic juice?
sodium bicarbonate and enzymes to digest all four macromolecule groups
is sodium bicarbonate acidic or basic?
very basic
What are the enzymes contained in pancreatic juice?
Pancreatic amylase trypsin chymotrypsin carboxypeptidase elastase pancreatic lipase ribonuclease deoxyribonuclease Other enzymes activated by trypsin formation from trypsinogen
what does amylase do?
breaks down starch
what do trypsin, chymotrypsin, carboxypeptidase, and elastase do?
all work on different aspects of protein breakdown
what does lipase do?
breaks down lipids
what does ribonuclease and deoxyribonuclease do?
breaks down RNA and DNA
What does tryspin do?
sets off a cascade reaction
what does bicarbonate do?
buffers gastric juice in chyme
Is the liver an essential organ?
yes
the lobes of the liver are divided into…
… hexagonal lobules
Hepatic refers to…
… the liver
Cells around the liver are referred to as…
… hepatocytes
what do the hepatocytes around the central vein do?
secrete bile and also metabolize a lot of different products such as alcohol, drugs, medicine, etc
what do the Kupffer cells do?
they clean; are essentially macrophages
What are sinusoids?
capillaries
what do sinusoids do?
sinusoids bring venous blood from the GI tract into the liver lobule
secretion of bile occurs in the …
liver
bile is stored where?
the gallbladder
is storage of bile necessary?
no, which allows for the gallbladder to be removed
what is the liver used for?
excretion of bilirubin (remember hemoglobin)
emulsification of lipids by bile salts
easier absorption of lipids
excretion of drugs and hormones
glycogen storage and glucose release/production
lipid metabolism
protein metabolism
storage of vitamins and minerals
detoxification
phagocytosis of old blood cells and some bacteria
activation of vitamin D
is emulsification considered mechanical or chemical digestion?
mechanical
Where is bile produced?
the liver
What is the flow of bile from the bile canaliculi?
bile canaliculi > bile ductules > bile ducts > hepatic duct joins cystic duct and forms the common bile duct
What does glycogen do?
it allows for sugar to be stored; similar to a banking system or links to a chain
where is glycogen stored?
in the liver and muscles
What is the hepatic portal system?
System in which deoxygenated blood from the GI tract flows to the liver where hepatocytes absorb nutrients/toxins and secrete products that are then sent back into circulation from the central vein back to the hepatic vein
where does 90% of all absorption occur?
the small intestine
What is absorption aided by in regards to the small intestine?
Length (10 ft avg)
Villi (1mm)
Microvilli (1 um) - known as the “brush border”)
What are villi and how do they help with absorption?
mucosa folds; they increase surface area into which things can be absorbed
What absorbs monomers in the small intestine?
capillaries or lacteals
What is the flow of the small intestine from the duodenum?
duodenum to jejunum to ileum
Finishing enzymes come from what glands?
intestinal glands
Do the duodenal glands secrete alkaline or acidic mucus and why
they secrete alkaline mucus which buffers stomach acid
What type of cell secretes mucus?
goblet cell
FYI
Pancreas (which releases digestive enzymes) ports into small intestine
FYI
Small intestine has circular folds that allow for better absorption
What three structures are the villi composed of?
Absorptive cells
capillaries/lacteals
microvilli
What are the two components of mechanical digestion in the small intestine?
Segmentations and peristalsis
Describe peristalsis in the small intestine
Occurs post segmentation and is a slow migration from stomach to ilium
Small intestine: Chem digestion: brush border enzymes: the -ase’s : name and describe function
alpha dextrinase
maltase
sucrase
lactase
convert their input to monosaccharides (mostly glucose)
-Maltase works on maltose, sucrase on sucrose, etc
Small intestine: Chem digestion: brush border enzymes: the enzymes that work on peptides/proteins : name and describe function
aminopeptidase
dipeptidase
convert to amino acids; or catalyze the the cleavage of amino acids in petides/proteins
Purpose and location of nucleosides and phosphatases
take nucleotides and break them down into parts
located in small intestine
What are the three main components of chemical digestion in the small intestine?
Brush border enzymes
intestinal juices
pancreatic juice
FYI
Bile and intestinal juice work in combination with eachother
What are the three main components of mechanical digestion in the large intestine?
Haustral churning
Peristalsis
Mass peristalsis
What are Haustra and what is Haustral chruning?
Haustra are the pockets in the large intestine and Haustral churning is the contraction following distension
Describe chemical digestion in the large intestine
Bacteria is the large intestine consume the contents of the large intestine (not for our benefit), but their byproducsts are useful to us (and also create farts)
Where is the last stop for absorption of water, ions, and vitamins?
The large intestine
FYI
Diarrhea indicates that water is not being absorbed well in the large intestine
where are feces formed?
in the large intestine
What is feces composed of?
Water inorganic salts bacteria and their products unabsorbed/indigestible material epithelial cells
What are the five steps of the defecation reflex and are they voluntary or involuntary?
Rectum distends - involuntary
Stretch receptors are triggered from the spinal cord - involuntary
The parasympathetic nervous system causes contraction of colon and rectum - involuntary
Internal anal sphincter opens - involuntary
External anal sphincter is voluntarily relaxed - voluntary
What are the four macro molecules and subtypes, if any?
Carbohydrates - Mono- and polysaccharides
Proteins - Amino acids form polypeptides
Lipids - Simple, complex, steroids
Nucleic acids
What are the enzymes involved in the chemical digestion of carbs?
Salivary and pancreatic amylase alpha dextrinase sucrase lactase maltase
what do amylases do?
break down starch into maltose or alpha dextrins
what does alpha dextrinase do?
breaks down alpha dextrins to glucose or more accurately breaks down disaccharides into monosaccharides
Monosaccharides are absorbed where?
the small intestine
fructose travels via
facilitated diffusion
glucose and galactose travel via
secondary active transport
What are the enzymes involved in the chemical digestion of proteins?
pepsin trypsin chymotrypsin elastase carboxypeptidase aminopeptidase dipeptidase
what do pepsin, trypsin, chymotrypsin, and elastase do?
turn protein into peptides
what does carboxypeptidase do?
turns peptides into smaller peptides or amino acids
what do aminopeptidase and dipeptidase do?
turn peptides into amino acids
they are also known as the finishing enzymes
Where are amino acids, dipeptides, and tripeptides absorbed and via what transport method(s)
absorbed in the small intestine via active or secondary active transport
what are the enzymes involved in the chemical digestion of fats?
lingual lipase
gastric lipase
pancreatic lipase
bile salts
what is the purpose of the lipases?
they turn triglycerides into fatty acids or monoglycerides/diglycerides
what is the purpose of bile salts?
they ease the absorption of long-chain fatty acids and are used in emulsification
Through what transport method are lipids absorbed?
All lipids are absorbed by diffusion
Short chain fatty acids are carried via what type of vessel?
capillaries
long chain fatty acids are carried via what type of vessel?
lacteals
FYI
the longer the fatty acid, the more likely it is carried by the lacteals
What is beta oxidation as it applies to metabolism?
beta oxidation is when 2 carbons are removed from the fatty acid + CoA to create acetyl CoA which then leads in to the Krebs Cycle
Describe the 4 steps of deanimation as it applies to metabolism
The amino group is removed form the amino acid
NH3 is converted to urea by the liver which eventually becomes urine
The amino acid is converted to Krebs molecules and oxidized for ATP
Amino acid is is also converted to glucose and fatty acids
What are the enzymes involved in the chemical digestion of nucleic acids?
Ribonuclease
deoxyribonuclease
nucleosidases
phosphatases
what is the purpose of ribonuclease
breaks down RNA into nucleotides
what is the purpose of deoxyribonuclease
breaks down DNA to nucleotides
what is the purpose of nucleosidases and phosphatases
break down nucleotides into 3 parts
through what transport method are the parts of nucleic acid absorbed?
absorbed via active transport
what is the pH of saliva?
6.5 (acidic)
what is the pH of gastric juice?
2 (acidic)
what is the pH of pancreatic juice?
7.1 - 8.2
what is the pH of intestinal juice?
7.6
pH is adjusted by what type of feedback and what are some examples?
adjusted by negative feedback, examples include buffers and hormone release
what are the three hormones involved in digestion?
Gastrin
Cholecystokinen
Secretin
what is the purpose of gastrin?
triggers an increase in gastric juice which leads to the cascading effect of increased gastric emptying and sphinter control
what is the purpose of cholecystokinen?
triggers an increase in pacreatic juice which leads to the cascading effect of increased bile release leading to increased gastric emptying and satiation
what is the purpose of secretin?
triggers an increase in pancreatic juice which leads to a decrease in gastric juice
Where is it released? Where is it active? What is its job?
Salivary amylase
Release by salivary glands in mouth
active in the mouth
job is to break down starch to maltose and dextrins
Where is it released? Where is it active? What is its job?
Pancreatic amylase
released by pancreas
active in small intestine
job is to break down starch to maltose and and dextrins
Where is it released? Where is it active? What is its job?
Alpha dextrinase
released by brush border of small intestine
active in small intestine
job is to break down starch/glycogen to glucose
Where is it released? Where is it active? What is its job?
Sucrase
released by brush border of small intestine
active in small intestine
job is to convert sucrose to glucose
Where is it released? Where is it active? What is its job?
Lactase
released by brush border of small intestine
active in small intestine
job is to convert lactose into glucose
Where is it released? Where is it active? What is its job?
Maltase
released by brush border of small intestine
active in small intestine
job is to convert maltose into glucose
Where is it released? Where is it active? What is its job?
Lingual Lipase
released by salivary glands in mouth
active in small intestine
job is to break down triglycerides to fatty acids and diglycerides
Where is it released? Where is it active? What is its job?
Gastric Lipase
released in stomach
active in stomach and small intestine
job is to break down triglycerides to fatty acids and diglycerides
Where is it released? Where is it active? What is its job?
Pancreatic lipase
released in pancreas
active in small intestine
job is to break down triglycerides to fatty acids and diglycerides
Where is it released? Where is it active? What is its job?
Pepsin
released by chief cells in stomach
active in stomach
job is to break down proteins into polypeptides
Where is it released? Where is it active? What is its job?
Trypsin
released by pancreas
active in small intestine
job is to break down polypeptides into small peptides
Where is it released? Where is it active? What is its job?
Chymotrypsin
released by pancreas
active in small intestine
job is to break down proteins into polypeptides
Where is it released? Where is it active? What is its job?
Elastase
released by pancreas
active in small intestine (activated by trypsin)
job is to break down proteins into polypeptides
Where is it released? Where is it active? What is its job?
Carboxypeptidase
released by pancreas
active in small intestine
job is to break down proteins into polypeptides
Where is it released? Where is it active? What is its job?
Aminopeptidase
released by brush border of small intestine
active in small intestine
job is to break down protein, specifically removing the amino portion
Where is it released? Where is it active? What is its job?
Dipeptidase
released by brush border of small intestine
active in small intestine
job is to break down protein to convert to amino acids
Where is it released? Where is it active? What is its job?
ribonuclease
released by pancreas
active in small intestine
job is to break down RNA to nucleotides
Where is it released? Where is it active? What is its job?
deoxyribonuclease
released by pancreas
active in small intestine
job is to break down DNA to nucleotides
Where is it released? Where is it active? What is its job?
nucleosidases
released by brush border enzymes
active in small intestine
job is to break down nucleosides
Where is it released? Where is it active? What is its job?
phosphatases
released by liver
active in liver
job is to break down nucleotides into 3 parts
Gastrin: Where is it produced? Where is it active? What triggers it? What does it do?
produced in stomach by gastric glands
active in stomach
triggered by the smell or sight of food
causes gastric juice increase which leads to increase of gastric emptying
Cholecystokinen: Where is it released? What does it do?
Released in the small intestine
causes increase in pancreatic juice which leads to increase in bile release which leads to increased gastric emptying and satiation
Secretin: Where is it released? What does it do?
Released by the small intestine
Causes increase in pancreatic juice which leads to decrease in gastric juice
