L35: GI I&II Flashcards
What cells will line alimentary canal, secrete acid/mucus/digestive juices/absorb nutrients?
Epithelial cells
Digestive system grouped into 3 categories
- Oral cavity 2. ALIMENTARY TUBE/ CANAL 3. Accessory glands
Characteristics of alimentary tube? (3)
- Tube has layered structure - Layers are variable - Layers relate to function
What are the layers of the alimentary tube?
- Mucosa 2. Submucosa 3. Muscularis externa 4. Adventitia or serosa
General characteristics of the mucosa layer (most varied)?
-Epithelium (protect, secrete, or absorb/ often folded to inc SA/ regeneration via stem cells) -Lamina propria (immune protection) - Muscularis mucosa (contract mucosa- smooth m)
General characteristics of the submucosa layer of alimentary tube?
- Supporting layer - Blood and lymphatic vessels - Folds - Submucosal glands
General characteristics of the muscularis externa of alimentary tube?
- Moves luminal content - 2 sub-layers of muscle - inner circular (restricts luminal flow via sphincters) [CM] - Outer longitudinal [LM] - Myenteric plexus for innervation * OCCURS BTWN CM and LM
General characteristics of Serosa or adventitia of alimentary tube?
Serosa- around suspended organs (simple squamous epi). SMOOTH* and dont attach structures Adventitia- around organs attached to pelvic wall (CT)- ROUGH*
Esophagus function?
Transports food from oral cavity to stomach
Lego pieces for esophagus: function of transport? (3)
- Strat squam epi for protection 2. Mucous glands for lubrication 3. Skeletal and smooth muscle
Mucosa layer of the esophagus consists of?
- Stratified squamous cells, has LP & MM
Submucosa layer of esophagus consists of?
Has esophageal gland w/ excretory ducts, and mucus for lubrication; blood and lymphatic vasculature
Muscularis externa layer of esophagus consists of?
- Inner circular and outer longitudinal sub-layers - Skeletal muscle proximal, smooth muscl distal - Myenteric plexus btwn sub-layers*
Esophagogastric junction epithelium- what is exclusive?
Stratified squamous to simple columnar
Stomach function? (3)
- Secretion of “Gastric juice” - Formation of chyme - function of breakdown
Lego pieces for stomach: function of breakdown? (2)
- Glands to secrete acids and protective layers 2. Smooth muscle
In the stomach what are the three histologically distinct regions?
Cardia, Fundus & body, Pylorus
What is the function of rugae? What is exclusive about this?
Increases SA so we can eat more / store more; it is not permanent
What are the layers (and describe) of the fundus and body of simple stomach: mucosa?
- Epithelium (simple columnar, gastric pits and glands) 2. Lamina Propria (fenestrated capillaries, lymphatic tissue/ vessels) 3. Muscularis mucosa (smooth muscle)
In the mucosal epithelium of the fundus and body, what are two features of the epithelium layer?
- Epithelium dives downward at GASTRIC PITS - Invagination of epithelium forms GASTRIC GLANDS
What are the gastric glands of the fundus/body? What do they do?
Body and fundus Mucous, parietal, chief (Parietal and chief found in all mammals) Make gastric juice
What are the gastric glands of the cardia and pylorus? What do they do?
Cardia and pylorus Only mucous cells Protection at ends
Gastric glands characteristic?
Divided into regions with specific cells, parietal and chief
What do the parietal cells and chief cells of the gastric glands do?
Parietal cells (secrete HCl) Chief cells (protein digestion)
Describe the feature of the gastric pit cell- also what TYPE of cell makes up the gastric pit?
-Parietal cells w/ large, central nucleus -Acidophilic cytoplasm - Fried egg look
Parietal cells and HCl- describe (4)
-Plentiful mitochondria -Acid secretion needs ATP -Folded cell membrane increases SA, microvilli, intracellular canaliculus - More folds in active parietal cells
The chief cells of the gastric glands specifically are found where, initiates what, secretes what, degrades what, lifespan?
- Found in base of glands (basal RER) in apical granules - Initiates protein digestion - Secrete pepsinogen (–>pepsin) into lumen - Degrades protein into peptides - Lifespan about 75 days
The evaginations of the submucosa layer form what and when is it used?
Rugae, which flatten when stomach is full
The muscularis externa of the fundus and body have what layers? Function*?
- Inner oblique, middle circular, outer longitudinal - Function: innervated by myenteric plexus*
What is the function of the stomach’s pyloric sphincter? (2)
-Continuous with circular layer of m. externa -Relaxation of sphincter and contraction of muscularis externa allows gastric emptying
Serosa: all parts of the simple stomach; what does the layer consist of? What does it do?
Thin CT Layer - covered by mesothelium of cuboidal cells - secretes small amount of serous fluid into peritoneal cavity for lubrication
Nonglandular portions of the stomach develop from ___?
Esophagus
In the ruminant compound stomach, what three things make up the forestomach/proventriculus? What do these things develop from?**
Rumen + reticulum + omasum DEVELOPS fro mthe esophagus, non-glandular
In the ruminant compound stomach, the mucosal lining of the reticulum can be described as_____? Why is it exclusive*?
Cornified; only place there are stratified keritanized cells
The Small intestine has a function of? (3)
- Finishes digestion - Absorbs proteins, fats, carbs - immune defense
What the lego pieces needed for the small intestine? (3)
- GLANDS to secrete mucous/enzymes - FOLDS to increase SA - NODULES to house immune cells
The mucosal epithelium cells of SI can be described as? (funny analogy)
Simple columnar w/ microvilli: brush border.. FLAT TOP HAIR
What are mucosal epithelium SI characteristics?
- Evaginates into villia - INvaginations into short intestinal glands
What doe the microvilli, villi, and glands of SI increase on the mucosal epithlium?
SA for absorp
The SI enterocytes of the mucosal epithelium have what characteristics/ functions? (4) think structure and what they do
- Absorptive function - Tall microvilli - INCREASE tight junctions: containment of luminal contents - INCREASE lateral enfoldings
What enzymes play a role in muscosal epithelium? (1)
Glycocalyx enzymes
Lifespan of mucosal epithelial cells?
5 days
The goblet cells of the mucosal epithelium do what?
Protect
The goblet cells of the mucosal epithelium have what structures? Lifespan of these?
- Apical mucinogen granules - Mucus prevents self-digestion 5 days
What does the Lamina propria of SI do? What is exclusive for the ileum only?**(know as opposed to LI)
Provides host defense - GALT: gut-associated lymphoid tissue - AGGREGATED** nodules- Peyer’s patch (only ileum)
What are two capillaries of the SI lamina propria? What do they do?
- Fenestrated capillaries: transport of proteins, carbs - Lymphatic capillaries: called lacteals, transport of dietary fats
What are features of the muscularis mucosa of SI? (2)
- Smooth muscle vontract intestinal glands - Some muscle extends up villi which help move lymph
What structure is the SI submucosa similar to?
Same as rest of GI tube
What are the two exceptions to the SI submucosa when comparing it to the GI tube?* Features of each?
- Brunner’s glands (only in duodenum) - Secretes alkaline fluid to raise pH of incoming chyme 2. Plicae circulares (jejunum & ileum) - Evaginated submucosa covered with mucosa
Unlike rugae in stomach, plicae circulares cannot do what? However, they can do what?
Flatten; However, they can increase SA for absorption
The inner circular layer of the muscularis externa of SI is responsible for ___? Whereas the outer longitudinal is responsible for ____?
Inner circular: segmentation Outer longitudinal: tube shortening
The SI inner circular and outer longitudinal functions in ___ and is innervated by _____*?
Functions in peristalsis Innervated by MYENTERIC PLEXUS (gap junction)
What makes up the serosa portion and which 2 parts of SI are they found in?
Portions of SI suspended in peritoneal cavity; Found in jejunum and ileum
What makes up the adventitia portion and which part of the SI are they found in?
Portions of tract fixed to abdominal wall; Only around duodenum
What is the large intestine a function of? (3)
Absorb water Immune defense Compaction of feces
What three parts make up the colon?
Cecum, colon, Rectum
What the lego pieces needed for large intestine?
- MUCOUS GLANDS for lubrication - NODULES to house immune cells - MUSCULAR SACS for compaction
What are the cells in the LI mucosal epithelium?
Simple columnar with short microvilli
What do the cells of the LI mucosal epithelium invaginate into?
Long straight intestinal glands/crypts
What do enterocytes of LI do?
Absorb water; dehydrate feces
Why are goblet cells inside the LI so dense?
Lubrication
In the LI, SA is __? why?
Reduced because it is not as critical as in the SI
Non-ruminant herbivores have a specialized cecum, which houses what to do what?
Microfauna to ferment and breakdown cellulose, similar to forestomachs of ruminants
There are no _____, intestinal crypts open at the surface
Villar expansion
Cecum have what cells?
Goblet cells
What does the Lamina propria of LI do? What is exclusive for the ileum only?**(know as opposed to SI)
Provides host defense - GALT: gut-associated lymphoid tissue - ISOLATED** nodules - NO LYMPHATIC CAPILLARIES- colon cancers take long time to spread
What is the muscularis mucosal layer like on LI?
- Smooth muscle - Contract intestinal glands - contractions shake loose lodged feces
What is the submucosa layer like on LI?
- Dense irregular CT - Blood and lymphatic vessels
Once cancer descends into submucosa, what occurs?
Metstasis occurs rapidly
What does the muscularis externa do in the LI?
Compaction of feces
What are the characteristics of the muscularis externa in the LI? (3)
- Colon compartmentalized into sacs called HAUSTRAE - Formed by specilized muscularis externa - Outer longitudinal layer reduced to 3 strips
The outer longitudinal sub-layer of the LI musclaris externa is reduced to thin strips called ? What 2 species this is found in?
Teniae coli; cows and horses only
What does the teniae coli look like compared to colon?
Shorter than colon; colon bunches up to form haustrae
What structures do the serosa and adventitia make up in the LI?
Serosa: cecum, appendiz, transverse & sigmoid colon Adventitia: ascending & descending colon, rectum
The anal canal has the function of?
Excreting feces
What are the lego pieces needed for the anal canal function? (3)
- Strat sqam epi for protection 2. Mucous glands for lubrication 3. Skeletal and smooth muscle
In the esophagus, the muscalris is consisted of what muscle type and what is it used for?*
Skeletal muscle; swallwing and regurgitating
In the muscularis externa, we have both levels (inner and outer layer) why?*
For mechanical breakdown!
What part is the ‘glandular’ portions? What about the non-glandular? (3) *
Abomasum ; Rumen, Reticulum, Omasum
