Digestive System Flashcards
Swallowing
Begins with voluntary muscle action but finishes with involuntary peristalsis.
Upper one-third of the esophagus, the muscularis is exclusively skeletal muscle
The middle portion of the esophagus has a combination of skeletal and smooth muscle fibers
The lower third the muscularis is exclusively smooth muscle
Esophagus layers
The four layers of the GI tract are present. The esophageal mucosa has nonkeratinized stratified squamous epithelium.
Innermost: Mucosa
Submucosa
Muscularis
Outermost: Serosa
Esophageal glands
Small mucus-secreting glands in the submucosa which lubricate and protect the mucosa.
Stomach functions
Functions:
To continue the digestion of carbohydrates initiated by the amylase of
saliva,
To add an acidic fluid to the ingested food and mixing its contents into a viscous mass called chyme by the churning activity of the muscularis
To begin digestion of triglycerides by a secreted lipase
To promote the initial digestion of proteins with the enzyme pepsin.
Stomach regions
The wall in all regions of the stomach is made up of all four major layers of the GI tract.
Cardia, pylorus, fundus, and body
Cardia
A narrow transitional zone, 1.5-3 cm wide, between the
esophagus and the stomach
Pylorus
The funnel-shaped region that opens into the small intestine. Both regions produce mucus and are similar histologically.
Fundus and body
The much larger fundus and body regions are identical in structure and are the sites of gastric glands releasing acidic gastric juice.
Rugae
The mucosa and submucosa of the stomach have large, longitudinally
directed folds called rugae, which flatten when the stomach fills with food.
Mucosal surface
A simple columnar
epithelium that invaginates deeply into the lamina propria. The invaginations form millions of gastric pits.
Gastric glands
The gastric pits of the mucosal surface lead to long, branched, tubular gastric glands. In
the fundus and body the gastric glands themselves fill most of the mucosa.
Secretory cells of the gastric glands
Mucous neck cells
Parietal (oxyntic) cells
Chief (zymogenic) cells
Enteroendocrine cells
Mucous neck cells
Secretes acidic fluid containing mucin
Parietal (oxyntic) cells
Produces hydrochloric acid (HCl).
Chief (zymogenic) cells
Has all the characteristics of active protein-secreting cells. They produce pepsins, which starts the breakdown of protein, and gastric lipase, which starts the breakdown of lipids.
Enteroendocrine cells
Scattered epithelial cells with endocrine or
paracrine functions. Some secrete serotonin and others produce the peptide gastrin.
Gastric and duodenal ulcers
Painful erosive lesions of the mucosa that may extend to deeper layers.
Can occur anywhere between the lower
esophagus and the jejunum.
Causes:
Bacterial infections with Helicobacter pylori.
Effects of nonsteroidal anti-inflammatory drugs
Overproduction of HCl or pepsin.
Lowered production or secretion of mucus or
bicarbonate.
Small Intestine
The site where the digestive processes are completed and where the nutrients are absorbed.
Same four layers as other parts of the GI tract
Mucosa (inner), submucosa, muscularis, serosa, outer mesentery
Small Intestine segments
Duodenum (first), jejunum, and ileum
Mucosa of small intestine
Densely covering the entire mucosa of the small intestine are short mucosal outgrowths called villi that project into the lumen.
Villi of small intestine
finger- or leaflike mucosal projections covered by a
simple columnar epithelium of absorptive cells called
enterocytes, with many interspersed goblet cells that produce mucus.
plicae circulares
The mucosa and
submucosa form circular
folds or plicae circulares,
which increase the
absorptive area.
Small Intestine Cell Types in Mucosa
Enterocytes
Goblet cells
Paneth cells
Enteroendocrine cells
Enterocytes
The absorptive cells, are tall columnar cells. The
apical end of each enterocyte displays a striated (or brush) border, which is a layer of densely packed microvilli through
which nutrients are taken into the cells.
Goblet cells
Secrete mucus to protect and lubricate the lining of
the intestine.
Paneth cells
For innate immunity. They release lysozyme and
other peptides that break down membranes of microorganisms.
Celiac disease (celiac sprue)
A disorder of the small
intestine mucosa that causes malabsorption and can lead to damage or destruction of the villi.
An immune reaction
against gluten or other proteins in wheat. The resulting inflammation affects the enterocytes, leading to reduced nutrient absorption.
Crohn disease
A chronic inflammatory bowel disease in
the ileum or colon; its cause is not understood. a
combination of immune, environmental, and genetic factors.
Large Intestine
Absorbs water and electrolytes and forms
indigestible material into feces, has the following regions: the short cecum,
with the ileocecal valve and the appendix; the ascending, transverse,
descending, and sigmoid colon; and the rectum, where feces is stored prior to evacuation.
Mucosa of the large intestine
The mucosa lacks villi and except in the rectum has no major folds.
Cell types:
Goblet cells
Enterocyte
Enteroendocrine cells
Colonocytes
Colonocytes
Have irregular microvilli and dilated intercellular spaces indicating active water absorption.
Lymphoid tissue of the large intestine
The richness in MALT (lymphatic nodules) is related to the large bacterial population of the large intestine.
Muscularis of the colon
The fibers of the outer layer gathered in three
separate longitudinal bands called teniae coli.
Colorectal cancer
An adenocarcinoma that
develops initially from benign adenomatous polyps in the mucosal epithelium.
Rectoanal junction
At the rectoanal junction the simple columnar
epithelium is replaced by stratified squamous
epithelium, typical of the epidermis.
Hemorrhoids
Swollen blood vessels in the mucosa or submucosa
of the anal canal
Results from a low-
fiber diet, constipation, prolonged sitting, or straining at defecation, conditions that produce increased pressure on these blood vessels.
Functions of salivary glands
(1) to moisten and lubricate ingested food and the oral mucosa
(2) to initiate the digestion of carbohydrates and lipids with amylase and
lipase, respectively.
(3) to secrete innate immune components such as lysozyme.
Three epithelial cell types of salivary glands
Serous cells
Mucous cells
Myoepithelial cells
Serous cells
Protein-secreting cells (enzymes and other proteins).
Mucous cells
Contain apical granules with mucins that provide lubricating properties in saliva.
Myoepithelial cells
have contractile processes around the secretory unit
or duct that move secretory products into and through the ducts.
Parasympathetic stimulation of salivary glands
Usually elicited through the smell or taste of
food, provokes a copious watery secretion with relatively little organic content.
Sympathetic stimulation of salivary glands
Inhibits such secretion and produces dry mouth
often associated with anxiety
Pancreas
A mixed exocrine-endocrine gland that produces both digestive
enzymes and hormones.
Pancreas exocrine
The digestive enzymes are produced by cells of serous acini in the larger exocrine portion. This somewhat resembles the parotid gland histologically.
Secretes alkaline pancreatic juice into duodenum where bicarbonate ions neutralize the acidic chyme from the stomach
Pancreas endocrine
Involves primarily smaller cells located in clusters called the pancreatic islets (islets of Langerhans)
Pancreatic cancer
Usually a carcinoma of
duct cells, occurs most often in the head of the
organ.
Liver
The largest internal organ, in adults
Main digestive function is production of bile, needed for the emulsification, hydrolysis, and uptake of fats in the duodenum.
Major interface between the digestive system and the blood.
Hepatocytes
Liver cells
Functions:
Secretion of bile
Endocrine secretion into the blood of the major plasma proteins, including albumins, fibrinogen, and
many others
Conversion of amino acids into glucose
Breakdown (detoxification) and conjugation of ingested toxins, including many drugs
Amino acid deamination, producing urea removed from blood in kidneys
Storage of glucose in glycogen granules and triglycerides in small lipid droplets
Storage of vitamin A and other fat-soluble vitamins
Removal of erythrocytes (by specialized macrophages, or Kupffer cells)’
Storage of iron in protein complexes.
Liver: Arteries and Veins
Hepatic portal vein brings blood laden with nutrients and waste from intestines, and into the liver for processing.
Hepatic vein collects processed blood from liver and brings it to the inferior vena cava.
Bile
Bile acts as a surfactant, helping to emulsify the lipids in the duodenum, promoting their digestion and absorption.
Bile canaliculi form a complex network of channels.
Hepatocytes secrete bile into the canaliculi
Bilirubin
A pigmented breakdown product of heme (an
iron-containing molecule). It is released into the
duodenum and is converted by intestinal bacteria into
other pigmented products. These give feces and urine
their characteristic brownish and yellowish colors.
Liver cirrhosis
Occurs late in chronic liver disease, fibrosis and proliferation of fibroblasts and hepatic stellate cells occur beyond the portal areas. The excessive connective tissue may disrupt the normal hepatic architecture and interfere with liver function.
Gall Bladder
A saclike structure that stores and concentrates bile, and releases it into the duodenum after a meal.
Cholangiocytes
The cuboidal or low
columnar epithelial cells lining the gallbladder have microvilli and large intercellular spaces; these cells actively transport water, in this case for
concentrating bile.
Cholecystokinin (CCK)
Released from enteroendocrine cells of
the small intestine, causes contraction of the gallbladder muscularis layer to move bile into the duodenum.
Cholelithiasis
Reabsorption of water from bile in the gallbladder is involved in the formation
of gallstones in the gallbladder or biliary ducts, a condition called
cholelithiasis.
The portal lobule is a functional component of the liver that is primarily concerned with the
Flow of bile from hepatocytes into the bile duct
Reversed prompt
Begins with voluntary muscle action but finishes with involuntary peristalsis.
Upper one-third of the esophagus, the muscularis is exclusively skeletal muscle
The middle portion of the esophagus has a combination of skeletal and smooth muscle fibers
The lower third the muscularis is exclusively smooth muscle
Swallowing
Reversed prompt
The four layers of the GI tract are present. The esophageal mucosa has nonkeratinized stratified squamous epithelium.
Innermost: Mucosa
Submucosa
Muscularis
Outermost: Serosa
Esophagus layers
Reversed prompt
Small mucus-secreting glands in the submucosa which lubricate and protect the mucosa.
Esophageal glands
Reversed prompt
Functions:
To continue the digestion of carbohydrates initiated by the amylase of
saliva,
To add an acidic fluid to the ingested food and mixing its contents into a viscous mass called chyme by the churning activity of the muscularis
To begin digestion of triglycerides by a secreted lipase
To promote the initial digestion of proteins with the enzyme pepsin.
Stomach functions
Reversed prompt
The wall in all regions of the stomach is made up of all four major layers of the GI tract.
Cardia, pylorus, fundus, and body
Stomach regions
Reversed prompt
A narrow transitional zone, 1.5-3 cm wide, between the
esophagus and the stomach
Cardia
Reversed prompt
The funnel-shaped region that opens into the small intestine. Both regions produce mucus and are similar histologically.
Pylorus
Reversed prompt
The much larger fundus and body regions are identical in structure and are the sites of gastric glands releasing acidic gastric juice.
Fundus and body
Reversed prompt
The mucosa and submucosa of the stomach have large, longitudinally
directed folds called rugae, which flatten when the stomach fills with food.
Rugae
Reversed prompt
A simple columnar
epithelium that invaginates deeply into the lamina propria. The invaginations form millions of gastric pits.
Mucosal surface
Reversed prompt
The gastric pits of the mucosal surface lead to long, branched, tubular gastric glands. In
the fundus and body the gastric glands themselves fill most of the mucosa.
Gastric glands
Reversed prompt
Mucous neck cells
Parietal (oxyntic) cells
Chief (zymogenic) cells
Enteroendocrine cells
Secretory cells of the gastric glands
Reversed prompt
Secretes acidic fluid containing mucin
Mucous neck cells
Reversed prompt
Produces hydrochloric acid (HCl).
Parietal (oxyntic) cells
Reversed prompt
Has all the characteristics of active protein-secreting cells. They produce pepsins, which starts the breakdown of protein, and gastric lipase, which starts the breakdown of lipids.
Chief (zymogenic) cells
Reversed prompt
Scattered epithelial cells with endocrine or
paracrine functions. Some secrete serotonin and others produce the peptide gastrin.
Enteroendocrine cells
Reversed prompt
Painful erosive lesions of the mucosa that may extend to deeper layers.
Can occur anywhere between the lower
esophagus and the jejunum.
Causes:
Bacterial infections with Helicobacter pylori.
Effects of nonsteroidal anti-inflammatory drugs
Overproduction of HCl or pepsin.
Lowered production or secretion of mucus or
bicarbonate.
Gastric and duodenal ulcers
Reversed prompt
The site where the digestive processes are completed and where the nutrients are absorbed.
Same four layers as other parts of the GI tract
Mucosa (inner), submucosa, muscularis, serosa, outer mesentery
Small Intestine
Reversed prompt
Duodenum (first), jejunum, and ileum
Small Intestine segments
Reversed prompt
Densely covering the entire mucosa of the small intestine are short mucosal outgrowths called villi that project into the lumen.
Mucosa of small intestine
Reversed prompt
finger- or leaflike mucosal projections covered by a
simple columnar epithelium of absorptive cells called
enterocytes, with many interspersed goblet cells that produce mucus.
Villi of small intestine
Reversed prompt
The mucosa and
submucosa form circular
folds or plicae circulares,
which increase the
absorptive area.
plicae circulares
Reversed prompt
Enterocytes
Goblet cells
Paneth cells
Enteroendocrine cells
Small Intestine Cell Types in Mucosa
Reversed prompt
The absorptive cells, are tall columnar cells. The
apical end of each enterocyte displays a striated (or brush) border, which is a layer of densely packed microvilli through
which nutrients are taken into the cells.
Enterocytes
Reversed prompt
Secrete mucus to protect and lubricate the lining of
the intestine.
Goblet cells
Reversed prompt
For innate immunity. They release lysozyme and
other peptides that break down membranes of microorganisms.
Paneth cells
Reversed prompt
A disorder of the small
intestine mucosa that causes malabsorption and can lead to damage or destruction of the villi.
An immune reaction
against gluten or other proteins in wheat. The resulting inflammation affects the enterocytes, leading to reduced nutrient absorption.
Celiac disease (celiac sprue)
Reversed prompt
A chronic inflammatory bowel disease in
the ileum or colon; its cause is not understood. a
combination of immune, environmental, and genetic factors.
Crohn disease
Reversed prompt
Absorbs water and electrolytes and forms
indigestible material into feces, has the following regions: the short cecum,
with the ileocecal valve and the appendix; the ascending, transverse,
descending, and sigmoid colon; and the rectum, where feces is stored prior to evacuation.
Large Intestine
Reversed prompt
The mucosa lacks villi and except in the rectum has no major folds.
Cell types:
Goblet cells
Enterocyte
Enteroendocrine cells
Colonocytes
Mucosa of the large intestine
Reversed prompt
Have irregular microvilli and dilated intercellular spaces indicating active water absorption.
Colonocytes
Reversed prompt
The richness in MALT (lymphatic nodules) is related to the large bacterial population of the large intestine.
Lymphoid tissue of the large intestine
Reversed prompt
The fibers of the outer layer gathered in three
separate longitudinal bands called teniae coli.
Muscularis of the colon
Reversed prompt
An adenocarcinoma that
develops initially from benign adenomatous polyps in the mucosal epithelium.
Colorectal cancer
Reversed prompt
At the rectoanal junction the simple columnar
epithelium is replaced by stratified squamous
epithelium, typical of the epidermis.
Rectoanal junction
Reversed prompt
Swollen blood vessels in the mucosa or submucosa
of the anal canal
Results from a low-
fiber diet, constipation, prolonged sitting, or straining at defecation, conditions that produce increased pressure on these blood vessels.
Hemorrhoids
Reversed prompt
(1) to moisten and lubricate ingested food and the oral mucosa
(2) to initiate the digestion of carbohydrates and lipids with amylase and
lipase, respectively.
(3) to secrete innate immune components such as lysozyme.
Functions of salivary glands
Reversed prompt
Serous cells
Mucous cells
Myoepithelial cells
Three epithelial cell types of salivary glands
Reversed prompt
Protein-secreting cells (enzymes and other proteins).
Serous cells
Reversed prompt
Contain apical granules with mucins that provide lubricating properties in saliva.
Mucous cells
Reversed prompt
have contractile processes around the secretory unit
or duct that move secretory products into and through the ducts.
Myoepithelial cells
Reversed prompt
Usually elicited through the smell or taste of
food, provokes a copious watery secretion with relatively little organic content.
Parasympathetic stimulation of salivary glands
Reversed prompt
Inhibits such secretion and produces dry mouth
often associated with anxiety
Sympathetic stimulation of salivary glands
Reversed prompt
A mixed exocrine-endocrine gland that produces both digestive
enzymes and hormones.
Pancreas
Reversed prompt
The digestive enzymes are produced by cells of serous acini in the larger exocrine portion. This somewhat resembles the parotid gland histologically.
Secretes alkaline pancreatic juice into duodenum where bicarbonate ions neutralize the acidic chyme from the stomach
Pancreas exocrine
Reversed prompt
Involves primarily smaller cells located in clusters called the pancreatic islets (islets of Langerhans)
Pancreas endocrine
Reversed prompt
Usually a carcinoma of
duct cells, occurs most often in the head of the
organ.
Pancreatic cancer
Reversed prompt
The largest internal organ, in adults
Main digestive function is production of bile, needed for the emulsification, hydrolysis, and uptake of fats in the duodenum.
Major interface between the digestive system and the blood.
Liver
Reversed prompt
Liver cells
Functions:
Secretion of bile
Endocrine secretion into the blood of the major plasma proteins, including albumins, fibrinogen, and
many others
Conversion of amino acids into glucose
Breakdown (detoxification) and conjugation of ingested toxins, including many drugs
Amino acid deamination, producing urea removed from blood in kidneys
Storage of glucose in glycogen granules and triglycerides in small lipid droplets
Storage of vitamin A and other fat-soluble vitamins
Removal of erythrocytes (by specialized macrophages, or Kupffer cells)’
Storage of iron in protein complexes.
Hepatocytes
Reversed prompt
Hepatic portal vein brings blood laden with nutrients and waste from intestines, and into the liver for processing.
Hepatic vein collects processed blood from liver and brings it to the inferior vena cava.
Liver: Arteries and Veins
Reversed prompt
Bile acts as a surfactant, helping to emulsify the lipids in the duodenum, promoting their digestion and absorption.
Bile canaliculi form a complex network of channels.
Hepatocytes secrete bile into the canaliculi
Bile
Reversed prompt
A pigmented breakdown product of heme (an
iron-containing molecule). It is released into the
duodenum and is converted by intestinal bacteria into
other pigmented products. These give feces and urine
their characteristic brownish and yellowish colors.
Bilirubin
Reversed prompt
Occurs late in chronic liver disease, fibrosis and proliferation of fibroblasts and hepatic stellate cells occur beyond the portal areas. The excessive connective tissue may disrupt the normal hepatic architecture and interfere with liver function.
Liver cirrhosis
Reversed prompt
A saclike structure that stores and concentrates bile, and releases it into the duodenum after a meal.
Gall Bladder
Reversed prompt
The cuboidal or low
columnar epithelial cells lining the gallbladder have microvilli and large intercellular spaces; these cells actively transport water, in this case for
concentrating bile.
Cholangiocytes
Reversed prompt
Released from enteroendocrine cells of
the small intestine, causes contraction of the gallbladder muscularis layer to move bile into the duodenum.
Cholecystokinin (CCK)
Reversed prompt
Reabsorption of water from bile in the gallbladder is involved in the formation
of gallstones in the gallbladder or biliary ducts, a condition called
cholelithiasis.
Cholelithiasis
