Exam 4: GI Tract Flashcards
Gingiva is lined by
masticatory mucosa
Hard palate is lined by
masticatory mucosa (parakeratinized and keratinized epithelium) and submucosa
Burton’s Line
blue-gray ginigval margin - caused by lead poisoning
Most of the oral cavity is lined by
nonkeratinized, stratified sqamous epithelium
3 strata: stratum basale, stratum spinosum, stratum superficiale
Submucosa
Filiform papillae
specialized mucosa associated with tongue
Covers most of tongue surface
Keratinized epithelium
No taste buds
Fungiform papillae
Mushroom shaped
Stratified squamous epithelium
Has taste buds
Circumvallate papillae
Approximate to sulcus terminalis
Largest of papillae
Covered by stratified squamous epithelium
Along lateral margin on either side are taste buds
Deep moat along lateral margin - circle base filled with secretions from serous glands
Foliate papillae
Leek shaped
found on lateral margins of tongue
Contain taste buds in lateral margins
Also have moat and serous glands
Taste bud has 3 cell types
sensory, supporting, and basal
Area of lip facing oral cavity has what kind of epithelium?
lining mucosa (nonkeratinized stratified squamous)
Vermilion zone (red free margin)
transition zone between epidermis of skin (with sebaceous gland and hair follicles) and epithelium of mucosal lining (lamina propria and labial gland is submucosa)
Has no glands or hair follicles
Parotid gland
Only serous cells
Some adipose cells scattered
Submandibular gland
Mixed gland
Primarily serous cells with some mucous cells
Has serous demilunes
Sublingual gland
Mixed gland
Primarily mucous with some serous cells
Has serous demilunes
Anatomic crown of tooth
Enamel and Dentin
Root of tooth
Cementum and dentin
Center of tooth contains
pulp chamber - blood vessels, nerve fibers, connective tissue
Gets smaller as age
Bud stage of tooth development
Process of invagination induced by neural crest cells that made their way into underlying tissue
Cap stage of tooth development
Cells undergo differentiation
Growth of mesenchyme pushes inner enamel epithelium up
Forms dental papilla
Stage induced by Activin Beta-A and BMP 4
Bell stage of tooth development
Inner enamel epithelium bell shaped
4 clearly defined tissue components: outer enamel epithelium, stellate reticulum, stratum intermedium, & inner enamel epithelium
Ameloblasts
Secrete enamel on outer surface of enamel
Derived from oral epithelium of ectoderm
Completely gone when tooth erupts - enamel secretion stops
Odontoblasts
Secrete dentin on pulp cavity side of dentin - whole life
Derived from neural crest cells of neuroectoderm
Appositional stage of tooth development
Dentin and enamel layed down
Bone beginning to form around dental pulp (previous dental papilla)
Cementum
secreted by cementocytes
Avascular
Cellular cementum - lower root, thicker
Attached to bone by Sharpey’s fibers
Dentinal tubules
Fluid filled tubules with nerve cell inside
If exposed without being covered by enamel - tooth becomes oversensitive to temperature changes
Sharpey’s fibers
run from cementum to bone of tooth socket
Made of type I collagen fibers
principle component of periodontal ligament
4 layers of the GI tract
Mucosa, Submucosa, Muscularis externa, Serosa/adventitia
Most epithelium in the GI tract is
simple columnar
Mucosa of GI tract consists of
Epithelium with basal lamina
Lamina propria - connective tissue with lymphoid tissue and glands
Muscularis mucosae - usually 2 layers of smooth muscle (inner circular and outer longitudinal)
Submucosa of GI tract consists of
dense, irregular CT
Glands in esophagus and duodenum
Submucosal (Meissner’s) nerve plexus
Blood vessels and lymphatics
Meissner’s plexus (submucosal plexus)
Located in submucosal layer
Autonomic NS, post-ganglionic parasympathetic neurons
Regulates glands and blood flow, innervates muscularis mucosae
Myenteric plexus
Located in muscular externa (between two layers of muscle)
Autonomic NS, post-ganglionic parasympathetic
Movement of musculature of muscular externa - peristalisis
Key features of esophagus
Lined with stratified squamous nonker.
Esophageal cardiac glands in lamina propria; Esophageal glands proper in submucosa with ducts
Upper 5% striated muscle, next striated and smooth muscle, distal 50% esophagus smooth muscle
Thoracic - adventitia
Abdominal - serosa
Barrett’s esophagus
Metaplastic columnar epithelium with goblet cells
At risk from development into adeoncarcinoma
Achalasia
damage to certain neurons in myenteric plexus cause constriction of LES - leads to bird beak appearance in distal esophagus
Characteristics of stomach
simple columnar epithelium
Glands empty into Gastric pits
Most regions have 2 layer muscularis mucosae
Muscularis externa: some areas have inner longitudinal layer (3 layers)
Middle circular layer thickens around pylorus
Glands of Fundus and Body
Gastric glands (diverse, simple branched tubular) with short gastric pits located in mucosa layer
Gastric gland Isthmus
Stem cell niche - turns over epithelium to replace any of cell types
Mucus secreting cells at surface epithelium
Gastric gland Neck
Mostly parietal cells (with some chief cells) - acidophilic
Secrete HCL and intrinsic factor in response to gastrin, histamine, and acetylcholine
Gastric gland Base (fundus)
Mostly chief cells (with some parietal cells) - basophilic
Secrete pepsinogen in response to acetylcholine
Also has enteroendocrine cells - secrete hormones
Glands of Cardia
Cardiac glands deeper in lamina propria than gastric pits - simple or branched tubular glands
Short gastric pits
Shape and size more randomized, lightly stained
Mucus secreting mostly
Glands of Pylorus
deep gastric pits, short branched tubular glands
Mucous and enteroendocrine cells
(G cells secrete gastrin)
Gastroduodenal junction
Pyloric sphincter
Thickening between stomach and duodenum
Thickening of circular layer of muscular externa
3 structural modifications to increase surface area of small intestine
Plicae circulares, Villi, Microvilli
Plicae circulares
permanent folds of mucosa and submucosa
Slow movement of chyme through intestine for absorption
increase SA 3x
Villus
Fold of mucosa along plicae circulares
increase SA 10x
Core is lamina propria
Microvilli
Columnar cells facing lumen on villi - brush border
smallest of surface modifications
Increases SA 20x
Gluten enteropathy (celiac sprue)
No longer see villi (atrophy)
Enterocytes disarrayed
Epithelium in lumen - hyperplasia of intestinal gland
Inflammation of lamina propria
Zollinger-Ellison syndrome
Caused by gastrin-secreting tumor
Tumor may arise in duodenum, pancreas, or peripancreatic soft tissue
Characteristics of small intestine mucosa
Columnar epithelium with Goblet cells & brush border
Intraepithelial lymphocytes
Intestinal glands (crypts of Leiberkuhn) in lamina propria
Many blood and lymphatic vessels in lamina propria
Intraepithelial lymphocytes
in mucosa of small intestine
Constant immune surveillance
If goes into uncontrolled state cause inflammatory bowel disease
Intestinal glands (crypts of Lieberkuhn)
Simple columnar epithelium Openings between Villi simple tubular glands Paneth cells at base Enteroendocrine and stem cells (basal end)
Paneth cells
At base of intestinal glands
Acidophilic
secrete lysozymes, defensins, and tumor necrosis factor-a
Extend into right colon
Characteristic of Duodenum
Brunner’s glands in submucosa
Secrete alkaline mucus and human epidermal growth factor - protect against acidic content
Well developed proximally, less so distally
Characteristic of jejunum
nothing, more vascularized so red in living person
Characteristic of ileum
Peyer's patches (lymphatic nodules) in mucosa M cells (antigen transporting cells) Has villi (unlike appendix, which also has lymphatic nodules)
Characteristics of large intestine mucosa
Do not have plicae circulares - have plicae semilunares (incomplete, only between teniae coli)
No villi
More intestinal glands - longer
More goblet cells - increase distally
ill-defined brush border
Poorly developed lymphatic vessels (prevents intramucosal cancer from metastasizing)
Teniae coli
3 longitudinal bands of muscularis externa
Large intestine does not have a complete outer longitudinal layer
Characteristics of the appendix
No villi
Complete musc. externa (no teniae coli)
Lymphatic nodules
Appendicitis
Fecalith and intraluminal pressure
Alterations in blood flow
Infection and mucosal ulceration
Transverse rectal fold (Valve of Houston)
Permanent fold of mucosa, submucosa, and portions of muscularis externa
Teniae coli in rectum
don’t exist - splay out and cover whole rectum as complete longitudinal muscular layer
Anal columns
Longitudinal folds of mucosa and submucosa in anal canal
Anal valves and anal sinus
pouch contains place glands empty to lubricate anal canal
Anal valves located between distal adjacent anal columns and sinuses located lateral to valves
Can get infected or plugged
Pectinate (dentate) line
Above line is stratified squamous nonkeratinized epithelium and large plexus of veins in submucosa
Below line is stratified squamous keratinized epithelium as it becomes skin (has sebaceous glands) and large plexus of veins in lamina propria (no submucosa layer here)
Anal cushions
connective tissue, smooth muscle, blood vessels
Left lateral, right anterior, right posterior
Anal continence
Internal hemorrhoids
Above pectinate line
Do not cause pain
External hemorrhoids
Below pectinate line
Cause pain
Internal anal sphincter
Thickened inner circular smooth muscle layer
False diverticula
outpocketings of colonic wall
Only involves mucosa and submucosa (true diverticula involves all layers)
Occurs mostly at weak points
External anal sphincter
skeletal muscle
Anorectal abscess
Inflammation can penetrate through outer wall of anal canal and enter space between sphincters - intersphincter abscess
Can then come down toward skin - perianal abscess (most common anorectal abbscess)
Ulcerative colitis
increased density of lymphatic vessels in colon
Involves mucosa and submucosa
Crohn’s disease
Fistula may form
involves all layers of intestinal wall
Hirschsprung’s disease
Aganglionosis of both plexuses (absent)
Always involves rectum, may involve more proximal segments
Capsule of liver - Glisson’s capsule
Fibrous connective tissue - Type III collagen covering liver
Richly innervated by nerves
Outer aspect of capsule is visceral peritoneum (simple squamous epithelium)
Classic hepatic lobule
Hexagonal plates of hepatocytes and sinusoids
6 corners along periphery
At corners are portal canals - have 3-6 per lobule
Central vein in middle of hexagon
Portal canals
contain CT, portal triad, lymphatic vessles, and autonomic nerve fibers
At corners of hepatic lobules
Portal triad
branches of hepatic artery, portal vein, and bile duct in portal canals
Periportal space (space of Mall)
between connective tissue and adjacent hepatocyte
Origin of lymph
Kupffer cells
immune surveillance in liver
Take a little bite off RBC when they pass through
If something wrong with RBC, will be removed completely
Perisinusoidal space
has no basal lamina for rapid movement of blood
Numerous microvilli increase surface area
Perisinusoidal cell
in perisinusoidal space
has large lipid droplet that accumulates and stores Vitamin A
When activated can deposit collagen
Can become contractile and restrict blood flow
Portal lobule
exocrine (bile secreting) function of liver into bile duct
Hepatic acinus
diamond shaped territory on either side of shared wall/portal space between two hepatocytes
Zone 1 - gets most nutrients
Zone 3 - gets less nutrients and more metabolic waste - drain into central vein
Drug induced necrosis is most likely to occur in hepatocyte zone
3
Necrosis, fat accumulation
Liver functions to
detoxify through enzymes of sER Glycogen metabolism Blood protein synthesis Bile acid synthesis Bilirubin conjugation
Gilbert syndrome
decreased conjugation of bilirubin
Benign condition
Crigler-Najjar syndrome
Absent bilirubin conjugation (type I) Decreased conjugation (type II)
Dubin-Johnson syndrome
Decreased secretion of conjugated bilirubin due to absence of mdr-2 transport protein
Alcoholic cirrhosis
increased abuse of alcohol
Small nodules on surface of liver
proliferating masses of hepatocytes - trying to regenerate liver cells
Increased elaboration of connective tissue that forms a wall around masses - prevents exchange of material
3 layers of gallbladder wall
Mucosa (simple columnar epithelium, BL, LP, no muscularis mucosae)
Muscularis - smooth muscle random oblique orientation
CT layer of serosa/adventitia (on hepatic surface side)
Rokitansky-Aschoff sinuses
In gallbladder
may extend through muscularis
Cholesterolosis
benign & reversible
elevated levels of cholesterol accumulate in gallbladder macrophages (foam cells)
Exocrine pancreas
Compound acinar gland
Acinar cells secrete enzymes
Ductal cells secrete water and ions (HCO3-) to neutralize acidic chyme
Endocrine pancreas
islets of Lagerhans secrete hormones
Centroacinar cells
nuclei project into center of acini
Form intra-acinar portion of intercalated ducts
unique to pancreas
Intercalated ducts empty into intralobular ducts
Acute pancreatitis
Reversible lesions characterized by inflammation
Range from edema and fat necrosis to necrosis of functional tissue and hemorrhage
Caused primarily by alcohol and gallstones
