Digestive System Flashcards
Structures in the Alimentary canal
mouth, pharynx, esophagus, stomach, small and large intestines, rectum and anus
Structures in the accessory digestive organs
Liver, Pancreas, Gallbladder, Salivary glands
Differentiate between segmentation and peristalsis. Where does segmentation take place?
Where does peristalsis take place?
Segmentation
* Contractions of smooth muscle move chyme (food product being digested) back and forth within canal to allow mixing and further breakdown
Peristalsis
* An organized contraction and relaxation of smooth muscle layers that propels food through the alimentary canal in one direction
List and briefly describe the 6 events that occur during digestion.
Ingestion->food through the mouth. …
Mechanical Digestion->chewing
Chemical Digestion->saliva
Movements->food to stomach
Absorption->intestines
Elimination->leave body
Differentiate between mechanical and chemical digestion.
Mechanical digestion
* Physical breakdown of food
particles
* Chewing, churning,
segmentation
Chemical digestion
* Enzymes and chemicals break down food
The alimentary canal is made of multiple layers of tissues. List from lumen to outermost layer, the 4 main layers of this canal
Lumen, Mucosa, Submucosa, Muscularis externa, Serosa
Name one organ lined with adventitia. Explain why this is the case.
esophagus, because it is not covered by peritoneum.
Compare the nerve plexuses of the enteric nervous system.
- Myenteric nerve plexus
- Controls peristalsis and segmentation
- Within muscularis externa
- Submucosal nerve plexus
- Controls secretions of glands &
muscularis mucosa contractions - Within submucosa
- Controls secretions of glands &
Describe the reflex arc that occurs in the enteric nervous system.
sensory neurons→ interneurons → motor neurons
What kind(s) of digestion occur in the mouth? Elaborate.
both mechanical and chemical -> chewing and saliva enzymes
What kind of epithelium lines the oral cavity? The lips?
oral cavity -> squamous stratified epithelium
lips -> stratified squamous non-keratinized epithelium
Which layer(s) of tissues common to the alimentary canal is/are missing from the oral cavity?
Muscularis Externa or serosa/adventitia
What kind of epithelial tissue covers the anterior surface of the tongue?
keratinized stratified squamous epithelium
Describe the structure of the 3 types of papillae on the tongue. Which one(s) have taste buds?
Filiform papillae
* Rough surface
* Fungiform and circumvallate
papillae
* Contain taste buds
What is another term for “tongue-tie”? What is a potential consequence of this condition?
ankyloglossia
* Makes saying sounds where
tongue touches teeth (letters such
as t, z, p)
Identify the 3 primary salivary glands and their ducts
Parotid gland -> upper cheek
Submandibular gland ->under tongue
Sublingual gland -> below tongue
What are some functions of saliva?
- Moistens mouth
- Dissolves food (so can taste)
- Contains digestive enzymes
- Amylase starts breakdown of carbohydrates
- Lipase begins digestion of fats
- Contains mucus (helps swallowing)
- Neutralizes acids produced by bacteria that
promote decay (has bicarbonate buffer) - Antibacterial and antiviral components
What macromolecule does saliva start to chemically digest? What is the name of this enzyme?
amylase breaks down carbohydrates
What do these terms mean? How do they relate to human dentition?
* Heterodont
* Deciduous teeth
* Permanent teeth
- Heterodont dentition
- Different shapes of teeth for different jobs
- Deciduous teeth
- “Baby teeth”
- 20 total
- Permanent teeth
- 32 total that gradually replace deciduous
What are the four main types of human teeth?
- Incisors, Canines, Premolars, Molars
Follow a piece of food in the alimentary canal from the entrance of the oropharynx to the
esophagus.
Oropharynx, Laryngopharynx, Esophagus
Describe the types of epithelial tissue that the food passes.
Stratified squamous epithelium
Describe the muscularis externa in the esophagus from superior to inferior (the muscle type).
What is the significance of this arrangement?
Upper 1/3: skeletal muscle
Middle 1/3: mix of skeletal and smooth
Lower 1/3: smooth muscle
Mucous neck cells
Secrete mucus
Identify the layers of the stomach from stomach wall to lumen
Serosa, muscularis externa, submucosa, mucosa
What is the significance of 3 layers to the muscularis externa for the stomach?
To digest food
What is a function of the rugae?
Folds of mucosa that increase surface area and allow stomach to expand
What kind of digestion occurs in the stomach?
- Mechanical digestion (churning)
- Chemical digestion (digestive enzymes and HCl)
Parietal cells
Produce and secrete 2 products
* HCl which destroys bacteria
* Gastric intrinsic factor (GIF) which is
necessary for vitamin B12 absorption in
small intestine
Chief cells
Produce and secrete pepsinogen
* Also secrete gastric lipase
* Fat digestion
Enteroendocrine cells
Release hormones
Undifferentiated stem cells
Found at junction between
gastric pits and gastric glands
* Because of harsh environment,
stomach cells are replaced every
3-7 days
Identify the steps involved in pepsin formation. What does pepsin do?
- Activated when food enters
stomach; releases gastrin into
bloodstream - Stimulated by gastrin
to release pepsinogen - Stimulated by
gastrin to release HCl
Pepsin breaks down proteins in food
* It is created when pepsinogen mixes with HCl
What does gastric lipase do?
digest fats
What are 4 features of the small intestine that contribute to its large surface area?
Length, Circular folds, Villi, Microvilli
What structures are found within a villus? What foods enter which of these structures?
- Lamina propria is highly vascular * Allows for increased absorption * Capillaries * Absorb proteins and carbs * Lacteals * Absorb fats (which are too large
to enter capillaries) - Muscularis mucosa * Moves villi within lumen to
increase contact with nutrients
What kind of epithelium lines the small intestine?
Simple columnar
List, from stomach to large intestine, the segments of the small intestine.
* Which is the longest?
* Which is the shortest?
longest: Ileum
shortest: Duodenum
middle: Jejunum
What is the material called that enters the small intestine?
bile enters from liver/gallbladder
Describe a lacteal
Absorb fats (which are too large
to enter capillaries)
Absorptive enterocytes (small intestine)
Majority of epithelial cells
* Lots of mitochondria
* Absorption of nutrients requires energy
* Abundant ER
* Assemble absorbed lipids into chylomicrons
Goblet cells
Secrete mucus
* Protects surface cells and lubricates chyme
Enteroendocrine cells
Secrete hormones to control
the release of other substances
What is the significance of the intestinal crypts?
Invaginations of mucosa, between villi
* Epithelial cells produce intestinal juice
* A watery liquid that mixes with chyme
Describe the cells found in the intestinal crypts (include their functions).
Undifferentiated epithelial cells (stem
cells)
* Rapid replacement of cells
* New lining every 3-6 days
* Paneth cells
* At base of crypt
* Secrete enzymes that selectively destroy
unwanted bacteria
* Help maintain healthy microbiota
* Role in protecting stem cells
Where do duodenal glands empty? What product do they produce?
ducts that open into intestinal crypts
* Found in submucosa of
duodenum only
* Secrete alkalinic mucus to
neutralize acidic chyme
What does MALT stand for? What is it involved with?
mucosa associated lymphoid tissue
provides defense
Where is bile produced? Where is it stored? What does bile do?
- Bile salts break emulsify fats in small
intestine - Bile is stored in gallbladder until released
into duodenum
Where does bile get released into?
duodenum
Describe the exocrine function of pancreas. Where do these sections get released?
Acinar cells produce and secrete pancreatic enzymes/juices
* Breakdown different food types
* Neutralizes chyme (bicarbonate)
* Pancreatic juices transported in
main pancreatic duct and released
by sphincter
What structure is the final control valve that regulates pancreatic and bile release?
Hepatopancreatic sphincter
Describe the influence of fats and acids on hormone secretion. What are the effects of these hormones?
-Chyme from stomach activates
-Presence of fat stimulates: Cholecystokinin (CCK), signals release of stored bile (breaks down fats for better absorption
-Presence of Acids stimulate: secretin signals release of pancreatic juice to neutralize acids
What do colonocytes do? What do they absorb?
absorb primarily
water/electrolytes
What is the significance of intestinal crypts in the large intestine?
Replace old cells
What are rectal valves’ claim to fame?
Transverse folds that prevent feces being
passed with flatus (gas)
What is the difference between the external and internal anal sphincters?
External anal sphincter
* Skeletal muscle, voluntary control
* Internal anal sphincter
* Smooth muscle, involuntary control
What are hemorrhoids?
- External and/or internal
hemorrhoidal vein swelling - Caused by excessive straining
(baby or defecating)
What are some functions of the liver?
Digestive function: produces bile
Metabolic functions: processes blood coming from stomach and intestines
Where is the hepatic portal vein?
behind stomach and liver
What is the green sac?
Gallbladder
Identify what these blood vessels carry (characterize the blood within them):
* Hepatic artery proper
* Hepatic portal vein
* Inferior vena cava
- Hepatic artery proper
- Provides oxygen-rich blood to liver
- Hepatic portal vein
- Transports nutrient-rich blood from stomach and intestines to liver
- Inferior vena cava
- Removes blood from liver after it has been processed
What is the microscopic shape of a liver lobule?
hexagon
What makes up portal triads? Where are these located?
Bile duct (transports bile out of lobule)
Portal venule (transports nutrient-rich blood into lobule)
Portal arteriole (transports oxygen-rich blood into the lobule)
What is a portal system?
Blood flows through 2 capillary beds before returning to the heart (stomach/intestine and liver)
What is the relationship between liver and gallbladder?
Gallbladder stores and concentrates bile
What are most gallstones made of?
Usually formed of cholesterol that precipitates out of bile while
stored in gallbladder
What controls the release of bile into the duodenum?
A sphincter at the duodenum
What causes most ulcers?
bacterium:Helicobacter pylori
Describe two forms of inflammatory bowel disease.
- Crohn’s Disease (more severe)
- Along entire intestine; primarily in terminal ileum
- Ulcerative colitis (less severe)
- Shallow inflammation large intestine; primarily in rectum
What are symptoms of IBS?
Cramping, diarrhea, weight loss, intestinal bleeding
Describe celiac disease.
Autoimmune -> Gluten triggers and immune response, damages
villi of small intestine
