Digestive System Flashcards
Mesentery
Peritoneal layers that support most of the abdominal organs (keeps them in place).
Omentum
Multi-layered folds of the peritoneum
that drapes over intestines like an
apron. Used for adipose deposits
(for insulation)
Peristalsis
Bands of smooth muscle contract alternatingly to propel substances through
Deglutition
To swallow (delivering the bolus from the pharynx to the stomach)
Oral Cavity: Gross Anatomy
- Includes teeth (dentition),
tongue, and salivary glands - Receives and mechanically
digests food through mastication, performs some chemical digestion through saliva (creating bolus)
Oral Cavity: Microscopic Anatomy
- Stratified squamous, non-keratinized lined mucosa
- Skeletal muscle muscularis
- Digestive Process:
oSalivary amylase breaks down polysaccharides (carbohydrates) into
disaccharides
oLingual lipase initiates triglyceride breakdown into glycerol & fatty
acids
Pharynx
- Passageway for food, fluids & air
- Stratified squamous, non-keratinized lined mucosa
- Muscularis layer contains pharyngeal constrictors for deglutition (swallowing)
Esophagus
- Straight, collapsible tube. Passageway for food & fluids.
- Mucosa transitions from non-keratinized stratified squamous epithelium to simple columnar
- Muscularis layer transitions from skeletal to smooth muscle
Stomach: Gross Anatomy
- J-shaped pouch that receives bolus and
mixes it with gastric juice in response to
the hormone gastrin. - Contains impermanent gastric folds called rugae for distention (stretch)
- Gastroesophageal and pyloric sphincters
are its gatekeepers/ valves
Stomach: Functions
- Initiates protein digestion
- Carries on limited absorption (very small amounts of water & some small molecules)
- Produces chyme
Stomach: Microscopic Anatomy
- Simple squamous mucosa with goblet cells (mucus prevents ulceration)
- Contains gastric pits that lead to gastric glands
- Muscularis has 3 layers (oblique, circular, and longitudinal)
Parietal Cells:
Secrete HCl and intrinsic factor (for vitamin B12 absorption)
Chief Cells:
Secrete inactive pepsinogen (enzyme). When pepsinogen contacts HCl, it is
activated and becomes pepsin.
Pepsin breaks polypeptides (proteins) down into smaller peptide fragments
Enteroendocrine cells:
Releases hormones such as gastrin to
regulate stomach secretions & motility
Duodenum
- Initial C-shaped curvature of the small intestine
- Receives acidic chyme and mixes it with bile and pancreatic juice to neutralize the chyme and continue chemical digestion
Pancreas: Gross Anatomy
- Located retroperitoneally
- Lies horizontally in the abdomen,
emptying into the duodenum - Responds to the duodenal hormones cholecystokinin (CCK) and secretin
Pancreas: Microscopic Anatomy
- Composed of simple cuboidal cells that form acini
- Acini secrete pancreatic enzymes
Pancreatic Amylase:
Breaks down polysaccharides into disaccharides
Pancreatic Lipase:
reaks down triglycerides into glycerol & fatty acids
Trypsin, Chymotrypsin, and Carboxypeptidase:
Proteolytic enzymes, break down polypeptides into smaller peptides
Nuclease:
Breaks nucleic acids into nucleotides
Liver & Gallbladder
- Liver is the largest internal organ in the body, composed of lobes that metabolize carbohydrates, lipids, and proteins.
- The liver also stores glycogen, filters & detoxifies blood, and secretes bile.
- Gallbladder is a small sac that concentrates and stores the bile that the liver produces.
- Both respond to the duodenal hormone cholecystokinin (CCK).
Liver & Gallbladder
- Liver is composed of lobules containing hepatocytes and macrophages.
- Bile salts emulsify fats and aid in the absorption of fatty acids, cholesterol, and
certain vitamins
Jejunum =
middle segment of small intestine
Ileum =
final segment, leads chyme to the cecum (beginning of colon) via the ileocecal sphincter.
Jejunum & Ileum: Gross Anatomy
- Lined with permanent circular folds that maximizes digestion of chyme &
nutrient absorption.
Jejunum & Ileum: Microscopic
Anatomy
- Mucosa has villi that are composed of simple columnar cells with microvilli (brush border), and goblet
cells. - Intestine’s enteroendocrine cells secrete CCK and secretin.
- Muscularis has 2 layers (circular and
longitudinal layers)
Peptidase:
Breaks peptides into amino acids
Sucrase, Maltase, and Lactase:
Breaks disaccharides into monosaccharides
Phosphatase:
Breaks nucleotides into nucleosides and
phosphates
Nucleosidase:
Breaks nucleosides into nitrogenous
bases and ribose/ deoxyribose
Large Intestine
- Includes the cecum, ascending colon, transverse colon, descending colon, sigmoid colon, rectum, & anal canal
- Absorbs majority of water and electrolytes from chyme to form feces
- Pockets of haustra are created by
bands of teniae coli - The appendix projects from the cecum (part of MALT)
Large Intestine: Microscopic Anatomy
- Majority of the mucosa is composed of simple columnar epithelium with goblet cells. Anal canal mucosa requires stratified squamous epithelium.
- Majority of the muscularis layer has 2 layers of smooth muscle (circular and longitudinal layers).
- Anal canal has 2 anal sphincter layers:
o Internal = smooth muscle
o External = skeletal muscle
Review: Hepatic Portal System
- Splenic vein, inferior mesenteric vein, and superior mesenteric vein merge to form the hepatic portal vein
- Blood enters the liver to be filtered by the hepatic portal system
- Filtered blood is sent through hepatic veins that return blood to the IVC
- Special Features:
- Liver lobules contain central veins with hepatocytes radiating from them
- Phagocytic macrophages reside in the live
GERD
Gastroesophageal Reflux Disease, requires PPIs (proton pump inhibitors to raise stomach pH), antacids, and dietary modifications
Emesis
- Vomiting
Impaction
Severe obstruction of bowels (hardened, rock-like stools)
