Digestive System Flashcards
What is alimentary canal?
the digestive tract (from mouth to butt)
Digestive system=
oral cavity + alimentary canal
Layers of digestive tube from inside to outside
Mucosa (epithelium, lamina propria, muscularis mucosa)
Submucosa
Muscularis
Adventitia/Serosa
What’s the difference between adventitia and serosa?
INTRAperitoneal organs=serosa= visceral peritoneum=mesothelium
RETROperitoneal organs=adventitia=loose CT
Parts of Mucosa
Epithelium, lamina propria, muscularis mucosa
Epithelium of digestive tract has the following….where are we?
a) folds
b) villi
c) peyer’s patches
a) folds= esophageal
b) villi= small intestine
c) peyer’s patches= illeum (lymphoid nodule aggregates)
Where would you find
a) Peyer’s patches
b) Aurebach’s plexus
c) Meissner’s plexus
d) Brunner’s gland
a) in epithelium (of illeum)
b) between two layers of muscle (all)
c) submucosa (all over)
d) submucosa (of duodenum)
A. Esophageal Mucosa–layers and contents
B. Esophageal submucosa
C. Muscularis externa
A. MUCOSA LAYER
1. epithelium=stratified squamous NON keratinized
2. Lamina propria= esophageal cardiac glands
3. Muscularis mucosa= single longitudinal layer of SMOOTH muscle
B. SUBMUCOSA= Esophageal glands proper
C. MUSCULARIS (from superior-inferior)
striated muscle–>smooth and striated–>smooth
Esophagus muscularis layers
Outer layer has fibers running in longitudinal direction, inner layer has fibers running around tube in circular direction. these fibers change from striated–>smooth muscle fibers as you move inferiorly in the esophagus
Esophageal glands- location, secretion, abundance
- Esophageal cardiac glands= in lamina propria: mucous
- Esophageal glands proper= in submucosa: mostly mucous secretions but also serous secretions (include lysozymes. MORE ABUNDANT*
What are lysozymes (how do they work), where are they secreted (x3)
Antibacterial defense mechanism that cleaves peptidoglycan in bacterial cell wall.
Secreted by 1) salivary glands, 2) esophageal glands proper (found in submucosa of esophagus), and 3) paneth cells.
Function of esophagus, how?
moves food from mouth to the stomach via action of muscularis externa (peristalsis)
Esophageal sphincters-
- made from what layer?
- Function
- types, function
- Muscularis externa
- Keep food from coming back up
- Upper= pharyngoesophagea l=initiates swallowing
Lower= gastroesophageal= keeps stomach acid from coming up
GERD
Caused by persistent acid reflux (failure of LES- lower esophageal sphincter)
Consequences of constant GERD
ulceration and dysphagia. Esophagus can become fibrotic and constrict.
Barrett’s Esophagus
- demographic
- abnormality–consequence of abnormality?
More common in males (X3). The lower esophagus makes simple columnar epithelium (intestinal) instead of stratified squamous (esophageal) –>more susceptible to acid from stomach= risk factor for esophageal adenocarcinoma
Hiatal Hernia
- cause
- consequence of?
- esophageal hiatus in diaphragm doesn’t close during development
- reflux esophagitis and ulceration –>dysphagia and feeling of lump in the throat
Gastric pits
Invaginations from epithelium to lamina propria leading into gastric glands. Deepest in pylorus and shallowest in cardia.
(deeper you go in the stomach, deeper the pits)
Stomach function
acidifies food to make chyme
makes digestive enzymes and hormones
Chyme characteristic affects the emptying rate of the stomach
Rugae
longitudinal folds in stomach mucosa AND submucosa that disappear when the tummy is distended
Parts of stomach?
Cardia, fundus, body, pyloric antrum, pylorus
REVIEW: Lump in the throat feeling can be caused by?
Hiatal hernia
Gastric Mucosa: Epithelium
Epithelium- simple columnar SURFACE LINING CELLS (mucous)
Cells found in gastric pit and gastric gland
- surface lining (pit),
- regenerative (isthmus of gland),
- mucous neck (neck of gland),
- oxyntic=parietal (upper half),
- zymogenic=chief (base of gland–in fundus only)
- enteroendocrine cells (base of gland0
Gastric mucosa: lamina propria
What are the contents (x7) and purpose?
Lamina propria is loose CT with:
- smooth muscle fibers
- lymphocytes
- plasma cells
- mast cells
- enterochromaffin-like cells
- fibroblasts
- highly vascularized (fenestrated capillaries receive bicarb from parietal cells)
- *provides support for gastric pits and gastric glands,
Gastric mucosa: muscularis mucosa
2 LAYERS (sometimes 3)
- poorly defined circular layer (inner)
- longitudinal layer of SM (outer)
- SOMETIMES- outermost circular layer
Gastric submucosa
type of tissue, contents?
Dense irregular COLLAGENOUS CT with fibroblasts, mast cells, lymphoid elements, and meissner’s plexus (PNS)
Gastric muscularis layer- parts?
-which one makes the pyloric sphincter?
3 LAYERS (inner to outer)
- incomplete inner oblique layer
- middle circular THICK=PYLORIC SPHINCTER
- Outer longitudinal layer
Gastric muscularis layer–function?
mixing gastric contents, emptying stomach.
Rate of emptying affected by chyme characteristics
Protein vs sugar vs fat with gastric emptying?
Protein is slowest, sugar is fastest, fat is in between.
Does stomach have serosa or adventitia?
SEROSA (intraperitoneal)
Glands of the fundus
- same as glands in ___ of stomach
- shape–be specific-what’s the pit like?
- cell types
- Body
- Shallow gastric pit leading to simple tubular glands with isthmus, neck and base.
- surface lining cells, parietal cells, chief cells, mucous neck cells, enteroendocrine cells, and regenerative cells
What is primary source of gastric juices?
Fundus- this way the food gets early exposure (not sure if this is true, but good way to remember it)
Surface lining cells
- type
- location
- function
- life span
- simple columnar
- found in epithelium of stomach
- secrete THICK VISCOUS mucous with high HCO3. Also has mucinogen granules (secrete mucin) on apical side of surface cells.
- 3-5 days
What secretes bicarbonate? What is the function of bicarb?
Secreted by surface lining cells of the stomach to protect the epithelium from the acid.
Compare Cardia, fundus and pylorus
Cardia= tubular glands with COILED end. Secrete mucous Fundus= shallow pits with simple tubular glands. Secrete gastric juices Pylorus= deep pits with branched glands- mucus and gastrin secreting.
- Where are parietal cells found?
- G-cells?
- chief cells?
- mainly fundus, some pylorus
(parietal->party= FUNdus, PYlorus –pies are at some parties) - Pylorus and duodenum (g-cells are type of enteroendocrine cell)
- Fundus
Compare muscularis MUCOSA of stomach and esophagus
Esophagus- single longitudinal layer (SM)
Stomach- 2 layers- inner circular, outer longitudinal (SM), and sometimes outer circular layer
Compare muscularis of stomach and esophagus
Esophagus- 2 layers- circular and longitudinal that changes from striated to smooth muscle as you move down
Stomach- 3 layers-incomplete oblique, thick circular, outer longitudinal. -all SM
Lesson we just learned about layers of stomach vs esophagus
Stomach one-ups esophagus in number of layers (muscularis mucosa and muscularis) .
Mucous Neck cells
- Location
- Characteristics
- Function & activation
- Life span?
- in NECK of gastric glands
- short microvilli, apical mucous granules, prominent golgi, shorter columnar cells
* *necks are kinda short–everything in it is short - Secrete SOLUBLE mucous, VAGAL activation
- Might be able to divide
What has apical mucinogen granules?
What has apical mucous granules?
Mucinogen granules=surface lining cells
Mucous granules= mucous neck cells
**mucinogen is a long word= surface lining cells are LONGER columnar cells than mucous neck cells.
What secretes soluble mucous? what secretes the thick viscous mucous?
Soluble= neck cells viscous= surface cells
Oxyntic cells (AKA?)
- Shape
- Staining (what stains opposite?)
- Location
- Function
- Characteristics
= parietal cells (Oxy at parties, duhh!)
- pyramidal
- pink in H&E vs purple chief cells
- upper half of gastric glands (neck/isthmus area?)
- Secrete HCL and gastric intrinsic factor
- lots of mitochondria (=pink staining), tubulovesicular system, intracellular canniliculi with microvilli
Resting vs active parietal (oxyntic) cell
**what constitutes active?
Resting: complex tubulovesicular system
Active: proliferation of intracellular canaliculi and microvilli–secretion of HCl
Gastric intrinsic factor
glycoprotein needed for vit B12 to be absorbed in small intestine
What stimulates HCl secretion?
acetylcholine and gastrin (APUD cells of pylorus) which causes structural change in the parietal cell to increase intracellular canaliculi (lined by microvilli)
Zymogenic Cells (AKA?)
- shape
- location
- staining (why?)
- Characteristics
- Function
Chief cells
- pyramidal shaped
- base of FUNDIC gland
- basophilic-lots of rER
- lots of rER (basal location), supranuclear golgi, zymogen secretory granules (apical)
- Secrete pepsinogen, renin precursors, lipase precursors