Digestive System consists of the alimentary canal (what?) and principal associated organs (what)
canal begins with: oral cavity (esophagus, stomach, small/large intestines), tongue, teeth, salivary glands, pancreas, and liver
4 layers
Mucosa, sub mucosa, muscularis externa, serosa/ adventia
Mucosa faces the what and includes which components
faces the lumen
includes lining epithelium, lamina propria, muscularis mucsae
Submucosa consists of what kind of tissue? What does it contain?
dense connective tissue
Vascular plexus & submucosal nerve plexus (Meissner's plexus)
Muscularis Externa is composed of what kind of tissue? How organized? What does it contain?
Smooth muscle, skeletal (up 1/3 esophagus) mixed skeletal/smooth (middle 1/3 esophagus)
-organized into two layers: inner circular, outer longitudinal
-contains myenteric (Auerbach's) plexus
Serosa. where in body?
simple squamous epithelium (mesothelium) coving thin underlying layer of connective tissue. In peritoneal cavity.
Adventitia
thin layer loose connective tissue, blends into connective tissue of surrounding structures
Oral Cavity - does NOT have which layers?
muscularis externa, serosa/ adventitia
Oral cavity muscosa - components?
Epithelium (stratified squaous epithelium), lamina propria, NO muscularis mucosae.
-non-keratinized in most of oral cavity, keratinized in hard palate, gingiva, some of tongue
Oral cavity submucosa
not clearly separated from lamina propria. Contains submucosal glands (minor salivary glands)/
Oral cavity minor salivary glands
-secreation?
-shape?
-intrinsic or extrinsic? (located where?)
muscous-secreting, branched tubular, intrinsic within wall of oral cavity
Tongue
-epithelium cell type
-is it keratinized? Where?
-contains intrinsic and extrinsic muscles (Define)
-stratified squamous epihtelium
-often keratinized on dorsal surface
-intrinsic origin/insertion in tongue
-extrinsic origin outside, insertion in tongue
lingual papillae
4 types (filiform, fungiform, circumvallate, foliate)
filiform papillae
-function
-location
-taste buds?
-other features
mechanical
keratinized, points backwards
no taste buds
Over entire dorsal surface
Fungiform papillae
-shape
-location
-taste buds?
mushroom-shaped
more on tip on tongue
taste buds on apical surface
circumvallate papillae
-shape
-location
-features
round, dome shaped
back of tongue, 8-12
surrounded by moat-like groove
grove epithelium is thinner, has taste buds
von Ebner's serous salivary gland ducts empty into moats
Foliate papillae
-location
-shape
-taste buds
-other
few, sides of tongue, lateral ridges
taste buds in grooves, von ebner's serous lingual salivary glads drain into grooves just like circumvallate papillae
Taste buds
-where are they?
-shape
-staining?
-characteristics?
-Cells in taste bud?
fungiform, circumvallate, foliate papillae
oval, pale-staining, usually extend into epithelium
sensory and support cells, stimulation causes nerve impulse along postsynaptic sensory nerve
Major salivary glands
main role & functions
intrinsic or extrinsic?
parotid (in front/ below ear, largest, all serous), submadibular (floor of oral cavity, mixed mostly serous), sublingual (small, floor of oral cavity, mixed mostly mucous)
-production of saliva
-lubricate oral cavity, moisten food
-digestive enzymes, star
Major salivary gland structure
3 parts, components of each
secretory part,
-three types of acini
-serous
-euchromatic nucleus in center of cell, basal cell is basophilic b/c lots RER, apical cell w/ small secretory granules, cells are usually pyramidal shape. Serous acini are spherical in shape.
-mucous
-heteroch
myoepithelial cells
non secretory, in acini
contractile, basal part of secetory cells
salivary gland tumors
-characteristics
-most common type, made of what kinds of cells?
usually in major salivary glands, 80% benign, most common is pleomorphic adenoma (made of ductal and myoepithelial cells)
Esophagus mucosa
-epithelium
-lamina propria
-muscularis mucosae
non-keratinized stratified squamous epithelium
loose connective tissue, less celluar than rest of GI
longitudinally oriented smooth muscle, separated by connective tissue (rest is circularly oriented)
Barrett's esophagus
metaplasia of esophageal lining (displacement with intestinal columnar epithelium). Usually from GERD, males over 50. Common precursor to esophageal adenocarcinoma
esophagus glands
-where found?
-types
-secrete what?
found in mucosa and submucosa
-mucosal glands - esophageal cardiac glands, terminal part of esophagus, sometimes begining
-esophageal glands proper: in submucosa, small tubuloalveolar, along length of esophagus
esophagus submucosa
-tissue?
-contains
dense irregular connective tissue
-blood, lympphatic, nerve/ganglions (Meissner's/ submucosal Plexus)
contains esophageal glands proper
esophagus muscularis externa
-layers
-how differ from rest of GI?
inner circular and outer longitudinal layers
-has skeletal muscle in some parts
-upper 1/3 = skeletal muscle
-middle 1/3 = skeletal and smooth muscle
-lower 1/3 = smooth muscle
esophagus adventitia/ serosa
-mostly what composed of what?
Which part is different, how?
most is adventitia
loose connective tissue blending into surrounding connective tissue
very distal part in peritoneal cavity is serosa.
Stomach functions
-what's chyme?
food storage
food digestion: HCL and enzymes (pepsin, lipase) - break down food into triglycerides/ proteins
regulation of GI function (secretes hormones (gastrin)
mix food with gastric juices = chyme
Stomach rugae
when stomach is empty, folds of submucosa/ mucosa - decrease in height as stomach expands
stomach regions, contains?
cardiac - contains cardiac glands
fundic - largest, contains fundic glands
body (only anatomy)
pyloric - proximal to pyloric sphincter, contains pyloric glands
Layers
mucosa, submucosa, muscularis externa, serosa
surface epithelium
-epithelium type
-cell type -> produce what?
-apical portion filled with
-forms what?
simple columnar epithelium
surface mucus cells, produce INsoluble, thick, viscous, gel-like coat that adheres to epithelial surface, protects from chyme abrasion
apical protion filled with mucinigen granules
Gastric pits
-formed by what
-lined with what?
-are they glands?
-where loctated?
invaginations of surface epithelium
lined with surface mucus cells
stomach mucosa
NOT glands
Stomach mucosa glands
-located in which layer?
-open into what?
-types of gastric mucosal glands?
located in the lamina propria
open into bottom of gastric pits
fundic, cardiac, pyloric
Fundic glands
-shape
-3 segments
-location and course
brnached tubular, straight in middle, coiled at base
everywhere except cardiac/pyloric , from muscularis
3 segments: isthmus (apical), neck (middle), base/fundis (bottom) adjacent to muscularis mucosae.
mucosae to gastric pits
Cell types in fundic glands
parietal, gastric cheif, mucous neck, enteroendocrine, progenitor
Parietal cells
functions
structure
Clinical - loss of parietal cells?
produce HCL (starts protein digestion, converts pepsinogen to pepsin, kills bacteria) and Intrinsic factor (for intestine to absorb B12)
-largest, "fried eggs," intracellular canaliculi, microvilli, lots of plasma membrane - apcial membrane of non-secreat
Tubulovesicular system
where apical membrane of non-secreting cells stored
when parietal cells stimulated to secrete HCL, tubovesicular system fuses with apical membrane, allows formation of microvilli in the intracellular canaliculus
Gastric cheif cells
-location
-main function
-other characteristics
-base of the gland
-seceation of pepsinogen - converted to proteolytic enzyme, pepsin
-protein secreting
abundent RER in basal part of cell
basophilic appearance
secretory granules in apical protion of cell
Mucous neck cells
-location
-main function
-neck of gland
-secreate soluble mucous
-small cells, heterochromatic nucleus, at base of cell, cytoplasm filled with mucinogen granules, "frothy
Enteroendocrine cells
-where
-secrete product into what?
-function
-base of gland
-secrete product into lamina propria
-secrete gastrointestinal hormones, regulate alimentary canal function
eg, gastrin -> gastric aci d secretion, ghrelin-> appetite, hunger perception
small cells, rest on basement membrane, form microvill
Porgenitor cells
in isthmus of gland
replace mucous cells and fundic gland cells (like parietal, mucous neck, chief, enteroendocrin cells)
Short lifespan (3-5 days), cells within the fundic gland live longer (6-8 months) - which cells? enteroendocrine, mucous, gastic chei
Cardiac glands
-location
-function
-structure
-narrow ring surrounding esophageal orifice
-produce mucus for gastric juice, protects against acid reflux
-branched tubular, mucus-secreting cells
basally placed flattened nucleus, cytoplasm filled with mucinogen granules
NO praietal or cheif cells
Gastr
Pyloric Glands
-location
-function
in pyloric antrum
produce mucus that protects pyloric mucosa
deep gastric pits, more than 1/2 muscoa
Stomach lamina propria
loost connective tissue
between gastric pits/ glands
immune system elements (lymphocytes, plasma cells, macrophages)
if inflammation, neutrophils, eosinophils.
Stomach muscularis mucosae
-clinical - malignant tumors of gastric epithelium
sheet of smooth muscle with 2-3 thin layers
orthogonal (circular and longitudinal) orientation
-from surface epithelial cells, or from glandular epithelium
early stage = no penetration into submucosa, late - into muscularis externa/ further
STomach submucosa
-tissue type
-glands
dense irregular connective tissue
No glands
plexus of blood vessles, nerve plexus: meissner's (submucosal) plexus
Stomach Muscularis externa
-layers
3 layers of smooth muscle
-inner oblique
-middle circular
-out longitudinal
-myenteric nerve plexus (Auerbach's plexus) between middle circular and longitudinal layers
Stomach Serosa
mesothelim with thin layer of subserosal connective tissue
Small intestine
-characteristics
-Regions
-functions
-general strucutre and layers
*unique feature
longest part of alimentary cnal (over 6m)
Regions: duodenum, jejunum, ileum
principal site of digestion
nutrient absorption
synthesis and secretion of digestive enzymes
microbial growth control in lumen
regulate GI function via ndocrine secretion by enter
Plicae Circulares
-contain
-structure
-location
contain mucosa and submucosa
-transverse folds
-distal duedenum, proximal jejunum, increase surface for absorption
Enterocytes/ intestinal absorptive cells
-functions
-structure
-location
-nutrient absorption
-produce digestive enzymes for final digestion (carb protein final stages in glycocalyx of the cells)
-monoglycerides/ fatty acids from lipids diffuse accross absorptive cell membrane, syth into triglycerides in GOlgi, become chylomic
Goblet cells
-functions
-cell structure
-prodcution of mucus
-narrow base, wide apex
-filled with mucinogen granules
-frothy cytoplasm
-very pale.
nucleus is small, traingular, heterochromatic, located at cell base
M-Cells
-function
-cell structure
--antigen transport: take microorganisms from epithelial lumen to lymphoid follicles. Macromolecules are endocytosed, discharged in intercellular space near T-lymphoctyes
-large, dome-shaped. basal surface is invaginated, forms large pocket, separated fro
Intestinal Enteroendocrine cells
same as stomach
-base of gland
-secrete product into lamina propria
-secrete gastrointestinal hormones, regulate alimentary canal function
eg, gastrin -> gastric aci d secretion, ghrelin-> appetite, hunger perception
small cells, rest on basement membrane
Intestinal intraepithelial lymphocytes
Type of...
Derived from...
Provide...
T-lymphocyte
Blood-derived
provide mucosal immunity
Crypts of Lieberkuhn
-2 types of cells found in crypts of lieberkuhn, not in surface epithelium
mucosal glands
throughout intestine
tubular glands
invaginations of surface epithelium
-paneth cells, progenitor cells.
Paneth Cells
-location
-function
-structure
-bottom of crypts of lieberkuhn
-regulate bacterial growth
-numerous large, refractile eosinophilic granules in apical protion of cell
-contain antibacterial enzyme lysozyme, alha-defensins, etc.
-kills some bacteria, sustain normal bacterial flora in int
Progenitor cells
-location
-function
-in crypts of Lieberkuhn
-undifferentiated cells, replacement cells for surface epithelial cells, except intraepithelial lymphocytes,
Intestinal lamina propria
-cell type
-contains?
-blood supply
lymphatics
loose connective tissue
-lymphoid follicles - form the GALT (gut-asscuated lymphoid tissue), immunolgoic barrier between intestinal lumen and body)
-capillary loops, begin from artierioles, return to venules of plexus. Soluble nutrients (AA, carbs) transp
Peyer's patches
large groups of lymphoid follicles in the ileum
large structures
follicle-associated epithelium covering peyer's patches, mostly M-cells/
Small intestine lymphoma
on of most common cancer of small intestine
from B or T-lympocyte in lamina propria
wall of intestine becomes thickened, infiltrated by lympohocytes
lacteal
blind ended lymphatic capillary in lamina propria of small intestine villus
-drain into larger lymphatic vessels in submucosa
transport lipds as chylomicra produced by enterocytes
-chylomicra are secreted into laminao propria by enterocytes, picked up. tr
small Intestinal muscularis mucosae
-composed of
several sheets of smooth msucle
small Intestinal submucosa
typical, consists of dense connective tissue
contains vascular and nerve plexus (Miessner's)
-contains submucosal glands in the duodenum (Brunner's glands)
Brunner's glands
mucus producing
branched tubular
most abundent in proximal duodenum
highly alkaline secretions - protect intestinge by netralizing acid-containing chyme
small Intestinal muscularis externa
tpical
inner circular layer
outer longitudinal layer
nerve plexus (Auerbach's) between the two layers
small Intestinal adventita/ serosa
duodenum covered by adventitia
jejunum, ileum by serosa
How to identify regions of small intestine
-duodenum
-jejunum
ileum
-Dudenum: submucosal Brunner's glands, least # of goblet cells.
-Jejunum: tallest, villi, most prominent lacteals
-ileum: Peyer's patches, highest concentration of goblet cells, villi are shorter than duodenum/ jejunum
Large intestine
-regions
-functions
-general structure
cecum (+ veriform appendix), colon, rectm, anal canal
-reabsorption of electrolytes and water, elimination of undigested food and waste
-typical structure - mucosa, submucosa, muscularis externa, serosa/adventita
Large intestine mucosa
NO Villi
mucosal epithelium is like small intestine
-columnar intestinal absorptive cells (enterocytes)
-NO paneth cells
-goblet cells are more abundent than in small intestine - extensive mucus production, moves waste
-crypts of lieburkhun, same cells as
Large intestine submucosa
same as rest of alimentary canal (dense connective tissue, mseissner's plexus
large intestine muscularis externa
2 layers of smooth muscle
inner circular,
outer longitudinal
-outer longitudinal forms three layers, equally spaced bands called teniae coli
Large intestine serosa
has small fatty projections - omental appendices, visible on outer intestinal surface
Large intestine regional differences
colon - largest part. Well expressed taeniae coli (not in appendix or rectum)
veriform appendix - no important role in digestion or absorption, has a lot of aggregated lymphatic follicles
Rectum - mucosa similar to distal colon, contains prominent Transve