Digestive System Flashcards
introduction of food and liquid into the oral cavity
ingestion
chewing, which divides solid food into digestible pieces
mastication
muscular movements of materials through the tract
motility
lubricating and protective mucus, digestive enzymes, acidic and alkaline fluids, and bile
secretion
for local control of motility and secretion
hormone release
enzymatic degradation of large macromolecules in food to smaller molecules and their subunits
chemical digestion
four main layers
mucosa, submucosa, muscularis, and serosa
consists of an epithelial lining; an underlying lamina propria of loose connective tissue rich in blood vessels, lymphatics, lymphocytes, smooth muscle cells, and often containing small glands; and a thin layer of smooth muscle called the muscularis mucosae
mucosa
separating mucosa from submucosa and allowing local movements of the mucosa
muscularis mucosae
contains denser connective tissue with larger blood and lymph vessels and the submucosal (Meissner) plexus of autonomic nerves
submucosa
composed of smooth muscle cells organized as two or more sublayers
muscularis
In the internal sublayer (closer to the lumen), the fiber orientation is generally
circular
in the external sublayer it is
longitudinal
thin sheet of loose connective tissue, rich in blood vessels, lymphatics, and adipose tissue, and covered with a simple squamous covering epithelium or mesothelium, is the outermost layer of the digestive tract located within the abdominal cavity
serosa
large fold of adipose connective tissue, covered on both sides by mesothelium, that suspends the intestines
mesentery
serous membrane lining the abdominal cavity
peritoneum
layer of connective tissue continuous with that of surrounding tissues
adventitia
plexuses in the digestive tract’s enteric nervous system are absent or severely injured, respectively
hirschsprung disease or chagas disease
The keratinized cell layers resist damage from abrasion and are best developed in the ___ on the gingiva (gum) and hard palate
masticatory mucosa
Nonkeratinized squamous epithelium predominates in the ___ over the soft palate, cheeks, the floor of the mouth
lining mucosa
- covered by very thin keratinized stratified squamous epithelium and is transitional between the oral mucosa and skin
- lacks salivary or sweat glands and is kept moist with saliva from the tongue
vermilion zone
The papillary and tonsillar areas of the lingual surface are separated by a V-shaped groove called the
sulcus terminalis
- numerous, have an elongated conical shape, and are heavily keratinized, which gives their surface a gray or whitish appearance
- provide a rough surface that facilitates movement of food during chewing
filiform papillae
- less numerous, lightly keratinized, and interspersed among the filiform papillae
- mushroom-shaped with well-vascularized and innervated cores of lamina propria.
fungiform papillae
consist of several parallel ridges on each side of the tongue, anterior to the sulcus terminalis, but are rudimentary in humans, especially older individuals
foliate papillae
- largest papillae, with diameters of 1-3 mm
- Ducts of several small, serous salivary (von Ebner) glands empty into the deep, moatlike groove surrounding each vallate papilla
- provides a continuous flow of fluid over the taste buds that are abundant on the sides of these papillae, washing away food particles so that the taste buds can receive and process new gustatory stimuli
vallate papillae (circumvallate)
- ovoid structures within the stratified epithelium on the tongue’s surface, which sample the general chemical composition of ingested material
- 250 taste buds are present
taste buds
In the adult human there are normally ___ permanent teeth
32
deciduous or milk teeth that are shed
primary teeth
The crown is covered by very hard, acellular ___ and the roots by a bone-like tissue called cementum
enamel
The bulk of a tooth is composed of another calcified material, ___, which surrounds an internal pulp cavity
dentin
highly vascular and well-innervated and consists largely of loose, mesenchymal connective tissue with much ground substance, thin collagen fibers, fibroblasts, and mesenchymal stem cells
dental pulp
fibrous connective tissue bundles of collagen fibers inserted into both the cementum and the alveolar bone
peridontal ligament
calcified tissue harder than bone, consisting of 70% hydroxyapatite
dentin
long polarized cells derived from mesenchyme of the developing pulp cavity
odontoblasts
white exudate on the tongue’s dorsal surface
oral thrush
hardest component of the human body, consist- ing of 96% calcium hydroxyapatite and only 2%-3% organic material including very few proteins and no collagen
enamel
Enamel consists of uniform, interlocking columns called ___ (or prisms), each about 5 μm in diameter and surrounded by a thinner layer of other enamel
enamel rods
In a developing tooth bud, the matrix for the enamel rods is secreted by tall, polarized cells, the ___ which are part of a specialized epithelium in the tooth bud called the enamel organ
ameloblasts
An apical extension from each ameloblast, the ___ process, contains numerous secretory granules with the proteins of the enamel matrix
ameloblast (or Tomes)
comprises the structures responsible for maintaining the teeth in the maxillary and mandibular bones
periodontium
covers the dentin of the root and resembles bone, but it is avascular
cementum
fibrous connective tis- sue with bundled collagen fibers (Sharpey fibers) binding the cementum and the alveolar bone
periodontal ligament
lacks the typical lamellar pattern of adult bone but has osteoblasts and osteocytes engaging in continuous remodeling of the bony matrix
alveolar bone
Around the peridontium the keratinized oral mucosa of the ___ is firmly bound to the periosteum of the maxillary and mandibular bones
gingiva
bound to the tooth enamel by means of a cuticle, which resembles a thick basal lamina to which the epithelial cells are attached by numerous hemidesmosomes
junctional epithelium
muscular tube, about 25-cm long in adults, which transports swallowed material from the pharynx to the stomach
esophagus
lubricate and protect the mucosa
esophageal glands
begins with voluntary muscle action but finishes with involuntary peristalsis
swallowing
narrow transitional zone, 1.5-3 cm wide, between the esophagus and the stomach
cardia
- funnel-shaped region that opens into the small intestine
- involved with mucus production
pylorus
- sites of gastric glands releasing acidic gastric juice
fundus and body
- The mucosa and submucosa of the empty stomach have large, longitudinally directed folds called
- flatten when the stomach fills with food
rugae
present mainly clustered but also occur singly among the other cells in the necks of gastric glands and include many progenitor and immature surface mucous cells
mucous neck cells
produce hydrochloric acid (HCl) and are present among the mucous neck cells and throughout deeper parts of the gland
parietal cells (oxyntic)
a glycoprotein required for uptake of vitamin B12 in the small intestine
intrinsic factor
- predominate in the lower regions of the gastric glands and have all the characteristics of active protein-secreting cells
chief cells (zymogenic)
scattered epithelial cells in the gastric mucosa with endocrine or paracrine functions
enteroendocrine cells
responsible for the clinical symptoms caused by overproduction of serotonin
carcinoids
In the cardia and pylorus regions of the stomach, the mucosa also contains tubular glands, with long pits, branch- ing into coiled secretory portions, called
cardiac glands and pyloric glands
Pylorus, duodenum, and pancreatic islets
D cells
Stomach, small and large intestines
EC cells
Pylorus
G cells
Small intestine
I cells, Mo cells, S cells
Duodenum and jejunum
k cells
Ileum and colon
L cells,
Ileum
N cells
Somatostatin
D CELLS
Serotonin and substance P
EC CELLS
Gastrin
G CELLS
Cholecystokinin (CCK)
I CELLS
Gastric inhibitory polypeptide (GIP)
K CELLS
Glucagon-like peptide (GLP-1)
L CELLS
Peptide YY
L CELLS
Motilin
MO CELLS
Neurotensin
N CELLS
Secretin
S CELLS
Increased gut motility
EC CELLS
Gastric acid secretion
G CELLS
Pancreatic enzyme secretion, gallbladder contraction
I CELLS
- Insulin secretion
- H2O and electrolyte absorption in large intestine
L CELLS
Increased gut motility
MO CELLS
Pancreatic and biliary bicarbonate and water secretion
S CELLS
Secretion from other DNES cells nearby
D CELLS
Gastric acid secretion
I CELLS, K CELLS, L CELLS, N CELLS
Gastric acid secretion Sense of hunger
L CELLS
Gastric acid secretion Stomach emptying
S CELLS
composed of connective tissue with large blood and lymph vessels and many lymphoid cells, macrophages, and mast cells
submucosa
The stomach is covered by a thin ___
serosa
disorder of the small intestine mucosa that causes malabsorption and can lead to damage or destruction of the villi
celiac disease
Between the villi are the openings of short tubular glands called ___ (or crypts of Lieberkühn) and the epithelium of each villus is continuous with that of the intervening glands
intestinal glands or crypts
cell types of the small intestine
enterocytes
goblet cells
paneth cells
enteroendocrine cells
M (microfold) cells
absorptive cells, are tall columnar cells, each with an oval nucleus located basally
enterocytes
- interspersed among the absorptive enterocytes
- They secrete glycoprotein mucins, which are then hydrated to form mucus, whose main function is to protect and lubricate the lining of the intestine
goblet cells
granules release lysozyme, phospholipase A2, and hydrophobic peptides called defensins, all of which bind and break down membranes of microorganisms and bacterial cell walls
paneth cells
unique epithelial cells specialized for transepithelial transport of particles and microorganisms, located mainly in the ileum’s mucosa overlying the lymphoid follicles of Peyer patches
M (microfold) cells
The mucosa of the large bowel is penetrated throughout its length by tubular ___
intestinal glands
The columnar absorptive cells or ___ have irregular microvilli and dilated intercellular spaces indicating active fluid absorption
colonocytes
The muscularis of the colon has longitudinal and circular layers but differs from that of the small intestine, with fibers of the outer layer gathered in three separate longitudinal bands called ___
teniae coli
adenocarcinoma that develops initially from benign adenomatous polyps in the mucosal epithelium
colorectal cancer
The distal end of the GI tract is the ___, 3-4 cm long.
anal canal
Nonkeratinized stratified squamous epithelium; cardiac glands at lower end
esophagus
Small esophageal glands (mainly mucous)
esophagus
Both layers striated muscle
in upper region; both layers smooth muscle in lower region; smooth and striated muscle fascicles mingled in middle region
esophagus
Adventitia, except at lower end with serosa
esophagus
Surface mucous cells and gastric pits leading to gastric glands with parietal and chief cells, (in the fundus and body) or to mucous cardiac glands and pyloric glands
stomach
Three indistinct layers of smooth muscle (inner oblique, middle circular, and outer longitudinal)
stomach
No distinguishing features
stomach
Serosa
stomach
Plicae circulares; villi, with enterocytes and goblet cells, and crypts/ glands with Paneth cells and stem cells; Peyer patches in ileum
small intestine
Duodenal (Brunner) glands (entirely mucous); possible extensions of Peyer patches in ileum
small intestine
Mainly serosa
small intestine
Intestinal glands with goblet cells and absorptive cells
large intestine
Outer longitudinal layer separated into three bands, the teniae coli
large intestine
Mainly serosa, with adventitia at rectum
large intestine
Stratified squamous epithelium; longitudinal anal columns
anal canal
Venous sinuses
anal canal
Inner circular layer thickened as internal sphincter
anal canal
Adventitia
anal canal
lined primarily by mucosa with non keratinized stratified squamous epithelium, with keratinized stratified squamous epithelium on the hard palate and gingiva
oral caity
Enamel calcifies as parallel enamel rods in a process guided by the protein ___
amelogenin
secreted as elongated dentinal tubules from tall odontoblasts, which line the pulp cavity and persist in the fully formed tooth
predentin
From the esophagus to the rectum, the digestive tract has four major layers
mucosa, submucosa, muscularis, adventitia
varies regionally along the tract but always consists of a lining epithelium on a lamina propria of loose connective tis- sue and smooth muscle fibers extending from muscularis mucosae layer
mucosa
The stomach has four major regions
cardia, pylorus, fundus, and body
The mucosa of the stomach fundus and body is penetrated by numerous ___
gastric pits
include immature precursors of the surface
mucous cells but produce less alkaline mucus while migrating up into the gastric pits
mucous neck cells
large cells with many mitochondria and large
intracellular canaliculi for production of HCl in the gastric secretion; they also secrete intrinsic factor for vitamin B12 uptake
parietal cells
clustered mainly in the lower half of the gastric glands, secrete the protein pepsinogen that is activated by the low pH in the lumen to form the major protease pepsin
chief cells (zymogenic)
scattered epithelial cells of the diffuse neuroendocrine system, which release peptide hormones to regulate activities of neighboring tissues during food digestion
enteroendocrine cells
The small intestine has three regions:
duodenum, jejunum, ileum
In all regions of small intestine the mucosa has millions of projecting ___, with simple columnar epithelium over cores of lamina propria
villi
The large intestine has three major regions
cecum, colon, rectum
the simple columnar epithelium lining the rectum shifts abruptly to stratified squamous epithelium of the skin at the anus.
anal canal
In which of the following structures of the oral cavity would taste buds be localized in the highest concentration?
vallate papillae
Certain antibiotic therapies slow the replacement of the cells lining the small intestine. This may cause the loss of what tissue type?
simple columnar epithelium
The teniae coli of the large intestine represent an organ-specific specialization of which layer of the intestinal tract wall?
muscularis mucosa
Which of the following would most likely result from a reduction in the number of Paneth cells?
Increased number of intestinal bacteria
A medical student on a rotation in the pathology laboratory is given an unlabeled microscope slide with tissue provided by a gastroenterologist from a cancer patient she is attending. The mucosa and submucosa are poorly preserved, with only the thick muscularis well-stained, showing striated fibers. The slide most likely shows a biopsy of which region of the GI tract?
esophagus
Diarrhea may result if which of the following organs fails to carry out its role in absorbing water from the feces?
colon
Which of the following is true of the absorptive cells of the small intestine?
Synthesize triglycerides from absorbed lipids
A 52-year-old man is diagnosed with a carcinoid after an appendectomy. The enteroendocrine cells producing this disorder differ from goblet cells in which of the following?
The direction of release of secretion
A 14-month-old girl is brought to the pediatric dentistry clinic because her erupted deciduous teeth are opalescent with fractured and chipped surfaces. X-rays reveal bulb-shaped crowns, thin roots, and enlarged central cavities. Tissue immediately surrounding one tooth’s central cavity is biopsied and prepared for histology, which reveals irregular, widely spaced tubules. Which of the following applies to this irregular tissue layer?
It consists of mineralized collagen secreted by cells derived from the neural crest.
A 39-year-old woman presents with dyspnea, fatigue, pallor, tachycardia, anosmia, and diarrhea. Laboratory results are: hematocrit 32% (normal 36.1%-44.3%), MCV 102 fL (normal 78-98 fL), 0.3% reticulocytes (normal 0.5%-2.0%), 95 pg/mL vitamin B12 (normal 200-900 pg/mL), and an abnormal stage I of the Schilling test. Auto- antibodies are detected against a cell type located in one region of the GI tract. In which regions would those cells be found?
Body of the stomach
have secretory units of either protein-secreting serous cells, usually organized in round or oval acini, or of mucin- secreting mucous cells in elongated tubules
salivary glands
have only serous acini
parotid glands
mixed but have primarily mucous tubules, some with serous demilunes
sublingual glands
also mixed but have mainly serous acini
submandibular glands
Salivary secretory units are drained by simple cuboidal ___, which merge as simple columnar striated ducts, which merge further as the larger interlobular or excretory ducts
intercalated ducts
Cells of ___ have mitochondria-lined, basolateral membrane folds specialized for electrolyte reabsorption from the secretion
striated ducts
unusual in having stratified cuboidal or columnar cells.
excretory ducts
embedded in exocrine serous acinar tissue, which comprises most of the pancreas and in which the cells secrete hydrolytic digestive enzymes for delivery to the duodenum.
pancreatic islets
pyramidal, with secretory (zymogen) granules in the narrow apical end and Golgi complexes, much rough ER, and a large nucleus at the basal end
acinar cell
draining pancreatic acini, including their initial
centroacinar cells that insert into the acinar lumen, secrete bicarbonate ions (HCO −) to neutralize chyme entering the duodenum from the stomach.
intercalated ducts
- large epithelial cells with large central nuclei (polyploid and often binucleated), much smooth and rough ER, and many small Golgi complexes
- including endocrine(plasma protein secretion), exocrine (bile secretion), glucose storage (glycogen granules), and detoxification (using SER and peroxisomes).
hepatocytes
hepatocytes are organized into irregular plates to form polygonal ___ in which the hepatocyte plates radiate toward a small central vein
hepatic lobules
Each hepatic lobule is surrounded by sparse connective tissue that is more abundant in the ___ at the corners
portal areas
Portal areas or tracts contain a small lymphatic and the portal triad
portal venule, hepatic arteriole, bile ductule
branch from the portal vein
portal venule
branch of the hepatic artery
hepatic arteriole
branch of the biliary tree
bile ductule
In the lobules the portal venule and hepatic arteriole both branch into irregular ___ between the hepatic plates where the nutrient-rich and O2-rich blood mixes, flows past hepatocytes, and drains to the central vein
sinusoids
discontinuous and fenestrated
hepatic sinusoids
where exchange occurs between the hepatocytes and blood plasma
perisinusoidal space (of Disse)
The sinusoidal endothelium includes many specialized ___, which recognize and remove effete erythrocytes, releasing iron and bilirubin for uptake by hepatocytes
stellate macrophages or Kupffer cells
present in the perisinusoidal spaces are ___ (or Ito cells) containing many small lipid droplets for storage of vitamin A and other fat-soluble vitamins
hepatic stellate cells
Between adherent hepatocytes in the hepatic plates are grooves called ___, sealed by tight junctions, into which hepatocytes secrete water and bile components, including bilirubin and bile acids.
bile canaliculi
All bile conducting ducts after the bile canaliculi are lined by simple cuboidal or columnar cells called ___
cholangiocytes
The common hepatic duct leads to the ___, which carries bile to the gallbladder for temporary bile storage and concentration.
cystic duct
In a liver biopsy from a long-time drug user which of the following hepatocyte organelles would be expected to be more extensive than normal?
Smooth endoplasmic reticulum
Which description is true of pancreatic zymogens?
Are inactive until they reach the duodenal lumen
Which process increases in response to parasympathetic stimulation of the salivary glands?
Volume of secretion
Which feature is unique to the exocrine pancreas?
Centroacinar cells
Which description is true of the bile canaliculi?
Lumens are entirely sealed by junctional complexes
Which description is true of the gallbladder?
Secretes mucus
Which description is true for the hepatic space of Disse?
Is directly contacted by hepatocytes
A 50-year-old woman presents to the family medicine clinic. She admits to drinking a six-pack of beer each day with a little more intake on weekends. Laboratory tests show elevated alanine amino- transferase/serum glutamic oxaloacetic transaminase (AST/SGOT). Her sclerae appear jaundiced and her serum bilirubin is 2.5 mg/dL (normal 0.3-1.9 mg/dL). A biopsy shows hepatic fibrosis with significant loss of normal lobular structure. Jaundice is most likely to result when the proper location or orientation of what hepatic structures is disrupted?
Hepatocytes
A 48-year-old woman is referred to an allergy and rheumatology specialist with itching eyes, dryness of the mouth, difficulty swallow- ing, loss of the sense of taste, hoarseness, fatigue, and swollen parotid glands. She reports increasing joint pain over the past 2 years. She complains of frequent mouth sores. Laboratory tests show a positive antinuclear antibody (ANA) and rheumatoid factor (RF) levels of 70 U/mL (normal < 60 U/mL) by the nephelometric method. A parotid gland biopsy shows inflammatory infiltrates in the interlobular connective tissue with damage to the acinar cells and striated ducts. In this case, resorption of which of the following will be most altered by destruction of those ducts?
Na+
A young child presents with hepatomegaly and renomegaly, failure to thrive, stunted growth, and hypoglycemia. A deficiency in glucose-6-phosphatase is identified and the diagnosis of von Gierke disease is made. What cellular structures would be expected to accumulate in hepatocytes during progression of this disorder?
Glycogen granules
