Digestive System Anatomy and Function Flashcards
What are the 3 stages of swallowing?
- Voluntary stage
- Pharyngeal stage
- Esophageal
What is mastication?
Chewing-mechanical manipulation of food
-turns it into a bolus
What secretions are there in the mouth?
- Salivary amylase
2. Lingual lipase
What is peristalsis?
Movement of bolus down the esophagus achieved through coordinated contractions and relaxations of both the circular and longitudinal muscles
What controls peristalsis?
Medulla oblongata
-involuntary
How is peristalsis initiated?
If food is still loved in the esophagus
What happens to bolus in the stomach?
Liquifired to enhance enzymatic digestion, then mixed thoroughly via muscle contractions
How much gastric juice is secreted into the stomach per day?
2-3L
What is the purpose of the stomach?
Reservoir for food before entering into the SI
-holds food for the right amount of time
What are the 2 sphincters present in the stomach?
- Lower esophageal sphincter: lets food in and prevents it from coming back up
- Pyloric sphincter: allows little bits of chyme into SI
What are the 3 divisions of the stomach?
- Fundus: receives food when it enters
- Body: Where secretions are coming from
- Antrum: Secretes hormones
What are the 4 types of stomach layers?
- Mucosa: Endo or exocrine cells, contains pits, has blood vessels, capillaries and collagen
- Submucosa: Neural network, connects mucosa to smooth muscle, blood and lymph vessels
- Smooth Muscle (Muscularis Externa): Muscle, neural network
- Serosa: External layer of dense connective tissue, protects outside off stomach
What are the 3 kind of exocrine cells?
- Mucus neck cells: Mucus and bicarbonate. Keeps neutral layer to protect the stomach acid from itself
- Chief cells: Pepsinogen and gastric lipase
- Parietal cells: Intrinsic factor, H+, Cl- (combine to make HCl)
What is the only endocrine cell?
G cells: Hormone gastrin
How does the stomach reduce the bolus to chyme?
Gentle mixing waves sent every 15-25 seconds to mix contents with secretions. Moree vigorous mixing occurs as digestion proceeds beginning at the body and intensifying towards antrum.
What is gastric emptying?
Pyloric sphincter is slightly open to allow small amounts of chyme into the SI
What is chyme?
Liquified food that goes from the stomach into the SI
How long does it take to breakdown the food once it enters in your stomach?
Depends on what content of the food was
What are the 3 processes that occur until all contents of the stomach are gone?
- Propulsion: gentle mixing waves
- Grinding: vigorous mixing from body to pyloric
- Retropulsion: Slight opening at pyloric sphincter where small amounts of chyme enter the duodenum
What happens to salivary amylase in the stomach?
Gastric juices inactivate salivary amylase
What happens to lingual lipase in the stomach?
Lingual Lipase is activated in the gastric juices
What is pepsinogen and what is its role?
Pepsinogen is a protein that must encounter acid to produce the active enzyme called pepsin
What is pepsin and what is its role?
Pepsin is responsible for beginning portent digestion in the stomach
What are the 7 different functions of stomach acid?
- Activates lingual lipase
- Activates pepsin
- Inactivates salivary amylase
- Kills micorbes
- Denatures proteins
- Stimulates secretion or hormones
- Gastric lipase
In which part of the digestive tract does the most digestion occur?
Small intestine
-specifically the duodenum
Where do the liver and pancreases solutions first interact with the chyme?
In the duodenum
What are the 3 regions of the small intestine?
- Duodenum
- Jejunum
- Ileum
What are properties of the duodenum ?
- Location of enzymes mixing the chyme
- Most digestion occurs here
- Increase or decrease motility to optimize chemical digestion
- smallest part
What are properties of the jejunum?
- Villi to increase surface area for optimal absorption
- Most absorption occurs here
- Medium in size
What are properties of the ileum?
- Less villi but can still absorb nutrients if necessary
- Largest part
What are the 4 layers of the small intestine?
- Mucosa: mixed epithelial cells, exo and endocrine, small blood and lymph vessels, crypts (invaginations), villi
- Submucosa: Neural network, get info from mucosa to let train know contents and how much
- Muscularis: Layers of smooth muscle (circular and longitudinal). neural network
- Serosa: thin layer of connective tissue
What is segmentation?
specialized mixing contractions in the small intestine to mix chyme with digestive juices that are secreted
What kind of contractions is segmentation?
Localized mixing contractions that also function to increase the interactions of the food particles in the chyme with the absorptive cells in the intestinal mucosa
What are the 7 cell types in the intestinal wall?
- Absorptive cells-epithelial cells with microvilli
- Goblet cells- secret mucus
- Intestinal gland cells- secretes intestinal juice (watery mucus, slightly alkaline)
- Paneth cells- secrete lysozyme
- S cells- secretes secretin
- CCK cells- secretes cholecystokinin
- K cells- secretes glucose dependent insulinotrophic peptide (GIP)
What are microvilli?
Also known as the brush border, increase the surface area of plasma membranes fo more nutrients can be absorbed
What do microvilli contain?
Brush border enzymes to help in digesting some macromolecules
What are the 6 brush border enzymes and what do the digest?
- Lactase- glucose+galactose
- Sucrase- glucose+fructose
- Maltase- glucose+glucose
- Aminopeptidase- removes AA side of a protein
- Dipeptidase-cuts dipeptide into 2 single AA
- Enteropeptidase-cuts trypsinogen into trypsin
What is the main function of the large intestine?
- To finish process of absorption
- nutrients absorbed here are generally not those that were absorbed in the small intestine - Production of certain vitamins
- Formation of feces
What are the 3 sections of the large intestine?
- Ascending colon
- Transverse colon
- Descending colon
What is the appendix?
Little area attached to the start of the large intestine that contains the good bacteria
What is a haustra?
Intestine bubbles/sections.
When chyme passes from bubble to bubble it flips/turns in each section. this helps to get nutrient and water out that is still in there. Flips through every bubble
What is the gastroileal reflex?
Presence of food stimulates the opening of the ileocecal valve
What is the haustral churning?
Mixing of large intestine contents from one haustra to the next
What is peristalsis and mass peristalsis of the large intestine?
Unidireftional movement of the lumen contents out of the large intestine
-Mass: allows for a more forceful contraction to signal you have to go to the bathroom
