Digestive System II Flashcards
What are the 4 layers of the esophagus and GI tract?
- Mucosal Surface - faces lumen
- Submucosa
- Mascularies Externa - no less than 2 layers of musculature, usually smooth muscle
- Serosa/Advensitia - serosa free, adventitia - anchors to other structures
What tissue type is the adventitia made of?
DCT
What tissue type is the mucosa made of? What does it contain?
Epithelium
Lamina Propria
Muscularis Mucosae
What is tissue type is the submucosa made of? In some locations they may contain what two accessories?
DCT
In some locations may contain glands or lymphatic nodule
What two layers compose the Muscularies externa?
Inner circular layer
Outer longitudinal layer
What does the muscularis externa do?
Allows for peristalsis
Pushes the food down the GI tract
What tissue type is in the serosa? What is its function?
Mesothelial lining (simple squamous epithelium) Created slick surface
What are the three layers of the mucosa?
- Epithelial Lining
- Lamina Propria
- Muscularis mucosae
What are contianed in the lamina propria?
Glands
What is contained in the submucosa?
Submucosal nerve plexus / Meissner’s Nerve Plexus
What two locations contain a submucosa?
- Esophagus
2. Duodenum
What is contianed int he muscularis externa?
Myenteric Nerve Plexus
What are the purposes of the two layers in the muscularis externa?
Inner Layer - circular: compress digestive materials
Outer Layer - longitudinal: corkscrew movement to push digestive materials along
What is the function of the esophagus?
Delivers food from pharynx to stomach
What is an identifying feature of the esophagus? What is its purpose?
The shape of the lumen, without food it collapses
Allows it to expand and contract as needed
Is there little or high amounts of regeneration of the epithelium of the esophogus?
There is constant regeneration of the epithelium
Is the muscularis mucosae thin or thick in the esophogus? What does this aid in?
The longitudinal smooth muscle in the proximal esophagus is thick
Aids in swallowing
What does the submucosa of the esophogus contain?
Submucosal (Meissner’s) plexus
Esophageal glands proper
How does the musculares externa of the esophagus change as you move down it?
Proximal 1/3 is skeletal muscle
Middle 1/3 is a combination of skeletal and smooth
Lower 1/3 is smooth muscle
Does the esophagus have adventitia or serosa?
Converts from adventitia to serosa upon entering the abdominal cavity
What do you see at the esophagus-stomach junction?
Transitions from stratified squamous to simple columnar
See the presence of pits
Thickening of musculature
What is the function of sphincters in the esophagus-stomach junction?
Control movement from one region to the next
Does the stomach perform endocrine or exocrine functions?
Mixed exocrine-endocrine organ
How does the stomach act as an endocrine system?
Releases digestive enzymes
How does the stomach act as an exocrine system?
DNES (diffuse neuroendocrine system): enteroendocrine
Release of ghrelin signals hunger
Release of gastric amylase, pepsinogen from chyme
What are the 4 parts of digestion?
- Carbohydrates
- Proteins
- Triglycerides
- Forms Chyme
What are the 4 anatomical regions of the stomach?
- Cardia: small, runs continuously
- Fundus: below cardia
- Body: bulk
- Pylorus: right before duodenum
Does the body of the stomach exist according to histologists?
No, the body and the fundus are made of the same tissue
What are rugae? Where are they located? What is their function?
Rugae are places where the submucosa juts upwards creating permanent longitudinal folds
Found in the stomach
Allows the stomach to expand with eating
When are Rugae most promienet?
When the stomach is empty
Where is the cardiac region of the stomach?
Narrow circular band surrounding the esophageal orifice
What is the function of the cardiac glands? Where are they found? Are there many pariental cells?
Found in the cardiac region of the stomach
Produce mucus and lysozyme
Few parietal cells
What is the function of gastric pits? What type of cells are they lined with? Where are they located?
Gastric pits are filled with musin and make insoluble mucus that goes over the entire surface of the stomach so it doesn’t get eaten away
Lined with surface mucous cell - give it a clear appearance
Begin at esophagogastric junction
What is the location of gastric (fundic) glands?
Fundus Stomach (bulk)
What are the three portions of the gastric (fundic) glands?
- Isthmus
- Neck
- Fundus
What type of cells are found in the isthmus region of gastric (fundic) glands?
Stem cells
What type of cells are found in the neck region of gastric (fundic) glands? (2)
Parietal Cells
Mucous Neck Cells
What type of cells are found in the fundus region of gastric (fundic) glands? (2)
Chief Cells
Enteroendocrine cells
What is the function of the mucous neck cells in the neck region of gastric (fundic) glands?
Make soluble mucus to solubilize chyme
What is the function of the parietal cells int he neck segments of the gastric (fundic glands)? What do they look like?
Make HCl and Intrinsic Factor
Big, pink, rounded or pyramidal in shape
What cells type is the most numerous in upper and middle neck regions of gastric (fundic) glands?
Parietal Cells
What happens when tubulovesicles decrease?
Microvilli increase in an actively-secreting cells
What does intrinsic factor fo?
Captures vitamin B12 and protects it until it can be absorbed in the ileum of the small intestine
Where are chief cells located? What do they look like?
Located in deeper part of gastric (fundic) glands, granular appearance
Basophilic cytoplasm with eosinophilic apices
What do chief cells secrete? What does it do?
Secrete pepsinogen > enters into acidic environment and becomes activated
Secrete lipase > breaks down lipids
Where are enteroendocrine cells located? What do they look like?
Enriched in fundus of gastric (fundus) glands
Clear cytoplasm
Closed = attached to basal domian but doesn’t extend to apocrine
Open = attached to basal domain, extends to apocrine, has microvilli
What is the function of enteroendocrine cells?
Closed - respond to neuronal stimulation
Open - Samples what is in the stomach (taste receptors), released gastrin (+ other hormones), responds to the immediate environment
What does the pylorus section of the stomach contain? (2)
Deep gastric pits
Pyloric glands
What do pyloric glands look like?
Longer pits with short coiled secretory part near muscularis mucosae
Glands curve
clear appearance because of surface mucosal cells
What is the function of pyloric glands? Are they abundant?
Secrete mucus and lysozymes
Is not as abundant as other pits
What 3 functions does the small intestine perform?
- Terminal Food Digestion
- Nutrient Absorption
- Endocrine Secretion
What are the 3 regions of the small intestine?
- Duodenum
- Jejunum
- Ileum
In what region of the small intestine does terminal food digestion mainly occur?
Duodenum
Why is the small intestine lines with tall columnar cells with microvilli?
Increased absorption and secretion
What is the plicae circularis? Where are they located? What is their function?
Folds in the small intestine
Analogous to the rugae in the stomach
Increase SA > increased absorption and secretion
What does the mucosa of the small intestine contain?
Epithelieum
Lamina Propria that extended into villi
Muscularis Mucosae
What does the submucosa of the small intestine contain? (2)
- Duodenal Glands / Brunner’s Glands
2. Peyer’s Patches (aka M cells)
What do duodenal/brunner’s glands of the small intestine produce? What is its function?
Make alkaline mucus that neutralizes the chyme from the stomach
What section of the small intestine has peyer’s patches?
The ilium
Does the small intestine have a serosa or adventitia?
Serosa
Absorption in the submucosa and mucosa is increased by what 3 structures?
- Plicae Ciculares - submucosa juts inward to create folds
- Villi - epithelium pushes out
- Microvilli - on all cells
In what 2 sections of the small intestine are plicae circulares folds most numerous?
- Distal duodenum
2. Proximal jejunum
What is the core of the villi in the small intestine? How do they differ in appearance in the ileum and duodenum?
Core of lamina propria
Leaf-like in the ileum
finger-like in the duodenum
How does the number of goblet cells change from the small intestine to the colon and rectum?
Increase the number of goblet cells as you move from the small intestine to the colon and rectum
Why do villi of the small intestine have an empty center?
Filled with lacteal which binds lymphatic vessel and catches lipids?
Where are the intestinal glands (Crypts of Lieberkuhn) located?
Extend from the muscularis mucosae to the luminal surface of the villi and are surrounded by lamina propria
What are the 5 accessory cells found in the mucosa of the small intestine?
- Enterocytes
- Goblet
- Paneth
- Enteroendocrine
- M cells
What is the function of enterocytes? What tissue type are they?
Simple columnar epithelial cell
Absorption
Secretion of digestive enzymes
What is the function of goblet cells? Where are they located?
Secrete mucin
Increase as you move toward the ileum
What is the function of paneth cells? What doe they look like?
Release antimicrobial peptides for bacterial defense
Eosinophilic granules with basophilic cytoplasm, look like a flower low key
What is the function of enteroendocrine cells? What system are they a part of?
Make and release paracrine and endocrine horomones
Part of the DNES (Diffuse Neuroendocrine System) (DNES is also in the stomach)
What is the function of M (microfold) cells? Is it unique to the small intestine? What is another name?
Aggregation of immune cells creates a small barrier over enlarged lymphatic nodules
Unique to the small intestine
AKA Peyer’s Patch
What does the lymphatic nodule under the M-cells do?
Surveillance of the lumen for the immune system
What are microvilli anchored into?
Terminal Web
What function does the microvilli perform?
Active transport to bring nutrients into the cell
Secrete out digestive enzymes
What type of cell in the small intestine has microvilli?
Enterocytes
What are the two states enteroendocrine cells can have in the small intestine?
Closed and open
Activation of taste receptors when open
Similar to cells in the stomach
What specific hormones do Enteroendocrine cells of the small intestine release? What are their functions? (2)
CCK - acts on gallbladder and pancreas
Secretin - acts on pancreas
Where are paneth cells located?
the base of intestinal glands of the small intestine
What are the 3 functions of the large intestine?
- Water absorption
- Vitamin absorption
- Feces storage
What are the 3 anatomical sections of the large intestine?
- Cecum
- Colon
- Rectum
What is included in the cecum of the large intestine?
Veriform appendix (which is before the cecum)
What is included in the colon of the large intestine? (4)
- Ascending
- Transverse
- Descending
- Sigmoid
What are Teniae Coli? What is their function? Where are they located?
Thicked bands of the outer longitudinal layer of muscularis externa
Penetrate the inner circular layer to create pouches = huastra coli
In the large intestine
What are haustra coli? What is their function? Where are they located?
Haustra Coli are sacculations of the colon caused by teniae coli
In the large intestine
Allow for independent contractions
What type of accessory cells are in intestinal glands of the large intestine?
Simple columnar
Goblet cells
Absorptive Cells
What cells do the intestinal glands of the large intestine lack?
No paneth cells
What accessory cells are in the lamina propria of the large intestine?
Lymphocytes
Large GALT
What are “large GALT” cells?
Gut Associated Lymphoid Tissue
What does the lamina propria of the large intestines lack?
Does not have lymphatic vessels
What are transverse rectal folds? What are they analogous to? Where are they found?
Submucosa pushes upwards to create folds
In the rectum
Similar to rugea and plica circulares
What type of cell is abundant in the rectum?
Goblet cells
Simple columnar epithelium
What 2 parts make up the anal canal?
- Anal Columns (upper)
2. Stratified Squamous (lower)
What is the anal canal?
Separates rectum and anus, very narrow
What is the anus?
External regions of the large intestine
What type of tissue make sup the anal canal vs anus?
Anal canal - non-keratinized stratified squamous
Anus - keratinized stratified squamous, hair follicles, sweat glands, apocrine glands
What is the internal anal sphincter? What muscle type is it made of?
Smooth muscle
Involuntary movement
Muscle thickens?
What is the external anal sphincter? What type of muscle type is it made of?
Skeletal Muscle
Voluntary movement
Rectum-Anal Junction what transitions do you see?
Simple columnar > non-keratinized stratified squamous > keratinized stratified squamous
What are the characteristics of anal glands? What is their function?
Extend into submucosa
Secrete mucus
What are circumanal glands? What is their function?
Apocrine glands
Sex attractant in some animals
