E3: GI Flashcards
What are the primary components of the Oral cavity?
- Lip
- External Skin
- Vermillion Zone
- Internal Mucosa
- Tongue
- Surface;
- Lingual Papillae
- Taste Buds
- Core
- Surface;
- MALT
- Palatine Tonsils
- Nasopharyngeal Tonsils (Adenoids)
- Major Salivary glands
- Parotid
- Sublingual
- Submandibular
What is this image of?
What are the components that can be seen here?
Lip:
Interior: Oral mucosa (NK.St.Sq & minor Salivary Glands)
Vermillion zone: Thin, lightly K.St.Sq | No oil/sweat glands
Exterior: Haired Skin (K.St.Sq), Sebaceous g.
Underlying Skeletal m.: Orbicularis Oris m.
What is this?
What are the labels?
Oral mucosa:
- NK.St.sq. epithelium
- Minor saliv glands
- Replenished every 2-3 wks
P: Papillary Lamina
R: Reticular Lamina
MSG: Minor Salivary Glands
SM: SMooth m.
What are the types of Lingual papillae?
Which have Tastes buds?
Lingual papillae:
- Filiform p.
- Foliate p.
- Fungiform p.
- Vallate p.
Those with Taste buds are bolded
This image is of what?
Where is it located?
Characteristics?
Filliform papillae
Located sparsely around surface of the tongue
Lightly keratinized pointed projections, creating a rough surface allowing the tongue to “grip” food
This image is of what?
Where is it located?
Characteristics?
Foliate Papillae
Located on the lateral edges of the tongue
Forms deep moats; Taste buds in lateral surface epithelium
Receives saliva from lingual glands.
This image is of what?
Where is it located?
Characteristics?
Fungiform p.
Located sparsely placed on the anterior surface of the tongue
Projects above the anterior surface of the tongue
Taste buds on apical surface
This image is of what?
Where is it located?
Characteristics?
Vallate p.
Located at posterior of tongue; forms a V-shaped row
Dome shaped
Largest & least numerous of the papillae
Taste buds located on the lateral surface of the pits
What are the 5 tastes?
Is there any regional specificity?
Which lingual papillae are there taste buds on?
Tastes:
- Bitter
- Salty
- Sweet
- Sour
- Umami
No regional specificity
Located on;
- Fungiform p.
- Foliate p.
- Vallate p.
What is this a picture of?
What are the components?
Tongue: Core
Skeletal m. & Minor Salivary Glands
ID the MALT within the oral/ nasopharyngeal cavities
Palatine tonsils:
- Left & right at back of throat
- Removed if subject to recurring Infections
Lingual tonsils:
- Posterior of the tongue
Nasopharyngeal tonsils: Adenoids
- Roof of nasopharynx
- Epithelial lining; St.Sq*
What are the Major Salivary glands of the oral cavity?
Where are they located?
3 major salivary glands:
- Divided into lobules by CT capsule
1. Parotid gland
2. Sublingual gland
3. Submandibular gland
What does the Major Salivary glands look like?
What type of gland is this?
ID the Duct
What type of gland is this?
ID the duct
What is Barretts esophagus?
Dx: Barrett’s Esophagus
Long-standing gastroesophageal reflux disease (GERD), which causes stomach contents to back up into the esophagus
Increased risk for esophageal adenocarcinoma
Describe the BASIC layer trend of the GI tract
Superficial to Deep;
- Serosa:
- Muscularis Externa:
- Outer longitudinal
- Inner circular
- Submucosa:
- Mucosa:
- Muscularis mucosae
- Lamina Propria
- Epithelium
Describe the esophagus histologically
Mucosa:
- NKstSq
- LP
- Muscularis mucosa: Thicker than most of GI
Submucosa:
- Sporadic glands
Muscularis propria:
- Inner: Circular
- Mid: Myenteric Plexus
- Outer: Longitudinal
- Up 1/3: SkM
- Mid 1/3: Mixed
- Low 1/3: Sm
Esophagus lining:
- Mostly thoracic: Adventitia
- Short segment in peritoneum: Serosa
ID this tissue
Esophagus
ID this image.
Esophageal-Gastric Junction
What are the regional sections of the stomach?
Stomach:
- Cardia
- Fundus
- Body
- Pylorus
Describe the internal surface of the stomach. Function?
What are the secretions of the stomach?
Stomach:
Function: digestion
- Rugae (folds in the mucosa) allow for expansion
Secretions:
- HCl
- Gastric lipase
- Pepsin
- Intrinsic factor
Describe the mucosa of the stomach & the components
Gastric Pits:
- Apical layer: Epithelial invaginations
- Lining: Foveolar (surface mucous) cells
- Basal Nuclei; light cytoplasm
- Lightly stained
Parietal Cells:
- Mid-section
- Highly eosinophilic; Due to high quantity of Mitochondria
- Secretes: Acid & Intrinsic Factor
Chief Cells:
- Highly Basophilic
- Secretes: Pepsinogen & Lipase
Enteroendocrine Cells:
- Sparsely placed (“dotted”) in base
- G-cells present in in GI
- Paracrine Secretion: Gastrin
Describe the Parietal cell function
Intracellular canaliculi
- Deep invaginations of apical pm
- Thousands of microvilli
[H+/K+ pump]
- Antiport: H+ in; K+ out
- Located on
[Carbonic anhydrase]:
- Catalyze cytoplasmic: [H_2 O+〖CO〗_2→〖HCO〗_3^-+H^+]
Antiporter on basal surface exchanges HCO3– for Cl-
Result: Acidic lumen & Neutral LP
How is the stomach protected from it’s own production?
How is the stomach protected?
- HCl forms in the lumen (not in the cell)
- Pepsin forms in the lumen, not in the cell
- Pepsinogen is secreted & cleaved
- [Gastric Lipase] is an acidic lipase
- Works only in acidic pH
- Surface mucus protects against acid
- Traps components that neutralize acid near the epithelium
- Gastric acid reduces ingested microbial burden
- Limits colonization
- 1 exception; H. Pylori
What are the sections of the Small intestine?
What is the function?
Sections:
Duodenum, jejunum, ileum
- Similar histology
Exceptions;
- Duodenum: Brunner’s glands
- Ileum: Peyer’s patches
Function:
- Terminal food digestion
- Nutrient absorption
- Endocrine secretion
- Mucosal immunity
- Peyer’s Patches (Ileum)
Where are Peyer Patches concentrated?
Why?
Peyers patches:
- Concentrated in distal Ileum
Why?
- Due to high concentration of microbiome in colon
Describe the histology of the Gastroduodenal Junction
Pylorus:
- Mostly gastric pits
- Gastric glands (parietal/chief) become sporadic
Duodenum:
- Mucosa: intestinal villi appear to increase SA (absorptive epithelium)
- Submucosa: Brunner’s glands
- Secrete an alkaline mucus
Describe the 3 levels of Small intestine surface area
- Plicae Circulares
- Villi
- Microvilli
Describe the mucosa of the small intestine
Mucosa:
Villi lined with;
- Enterocytes (S. Columnar)
- Goblet cells
- Enteroendocrine cells (Sporadic)
- Stem cells (base)
- Paneth cells (base)
Lamina propria
- Vessels
- Lymphatics
- Immune cells
What are enterocytes?
What is their function?
Enterocytes:
- Simple Columnar epithelium
- Absorb nutrients
- Paracellular Transport
- Transcellular Transport
- Secrete digestive enzymes
What are Paneth cells?
What do they secrete?
Paneth Cells:
- Located @ Base of crypts in Small intestine
- Eosinophilic granules
- Lysozyme: Cell wall breaking enzyme
- AntiMicrobial Peptides (AMP)
What is the function of enteroendocrine cells?
Enteroendocrine cells:
- Sense nutrients
- Activation triggers basolateral release of peptide hormones
- Diffuse in tissue fluid
Role:
- Gut motility
- Enzyme secretion
- Bile secretion
- Satiety
Just know G-cells which secrete Gastrin
What distinguishes the Duodenum?
Brunners gland in Submucosa
Describe the Duodenal mucosa & Submucosa
Mucosa:
Epithelium lined villi
- LP in the center of villi; Lumen in between
- Lining: simple columnar (enterocytes)
- Numerous goblet cells
Submucosa:
- Brunner’s glands
Describe the Ileum mucosa
Mucosa:
Typical small intestinal villi
- Sporadic goblet cells in epithelium within a villus is classic ileum
- *Goblet cells are staining darker due to stain
- Abundant MALT: Peyer’s patches
Where are stem cells located in the;
- Esophagus
- Stomach
- Small intestine
- Esophagus: Basal
- Stomach: isthmus/neck of gastric pit
- Small intestine: in the crypts
Identify this tissue:
- Esophagus
- Tongue
- Oral Mucosa
- Epiglottis
Tongue: Vallate Papillae
Identify this tissue
- Esophagus
- Jejunum
- Duodenum
- Gastric Pit
- Ileum
- Esophageal-Gastric Junction
Esophagus:
Identify this tissue:
- Small intestine
- Esophagus
- Oral Mucosa
- Stomach
- Gastro-duodenal Junction
Stomach: gastric tubules
What is the arrow pointing to?
- Myenteric Plexus
- Villus
- Muscularis Propria
- Serosa
Serosa
Identify this tissue:
- Stomach
- Small intestine
- Esophageal-Gastric Junction
- Gastric-duodenal Junction
Small intestine
Describe the basic structure & functions of the large intestine
Anatomy:
- Gross: Wall divided into sacs (haustra)
- Micro: all regions similar histologically
- Sections: Ascending > Transverse > Descending > Sigmoid
Function:
- Water Absorbtion
- Waste Elimination
- Microbiome (enormous)
ID this tissue.
Cross-section of Colon Mucosa
Straight tubular glands; lined with goblet cells
Nuclei at the base form the dark outline
LP in between circular tubules
ID this tissue
Colon Mucosa
Epithelium invaginates into straight tubular glands w/ many goblet cells
Cross section of colon can be distinguished from the Small intestine via presence of LP in between glands, while in SI, it is the lumen
What type of cell is this?
Where is it located?
What does it secrete?
Paneth cell
Base of the Small intestine crypts.
Secreted Lysozyme & AntiMicrobial Peptides
What is the arrow pointing to?
Teniae coli m.
- Outer longitudinal layer form 3 separate longitudinal ribbons
- Contraction causes the wall to bunch into haustra
- Teniae coli disappear at the rectum (back to MP)
- Converges together at Appendix
Describe the trend of microbiota within the GI tract
Sterile at birth, colonized by feeding
Microbiota varies by location:
Mouth: Abundant
Stomach: Scant (due to acid)
Small intestine: Scant, except distal ileum
Colon: Largest microbiome in the body
50% of dry fecal weight is alive
The gut-brain axis? Major focus of study
Dysbiosis of the gut microbiome: (out of order)
Ex.:
- Use of Antibiotics
- C-Diff
What is the function of the pancreas?
Basically describe it’s histology
Pancreas:
Both Endocrine & Exocrine organ
Exocrine: Secretes digestive enzymes into ducts to the duodenum
Endocrine: Islets of Langerhans secretes into fenestrated capillaries
What is this tissue?
What are the decernable components?
Pancreas:
Exocrine Acini & Endocrine glands (islets)
Microanatomy:
- Capsule
- CT divides acini into lobes
- All Serous
- Similar to a salivary gland
What is the tissue displayed?
What types of ducts are present?
Secretory acini (serous)
- Multiple digestive enzymes;
- Secreted as zymogens
- Activated by [enteropeptidase] in duodenum
Ducts:
Intralobular:
•Smaller; within the lobules
Interlobular:
- Large
- Simple Cuboidal (sometimes Columnar)
- CT surrounding it
What is produced from the cells depicted?
Protein:
- Trypsinogen
- Chymotrypsinogen
- Carboxypeptidase
- Elastase
Carbohydrates:
- α-amylase
Lipids:
- Triacylglycerol lipase
- Phospholipase A2
Nucleic Acids:
- RNAse
- DNAse
Bicarbonate ions
- (From ducts)
- Neutralizes the acid from the stomach
How do the enteroendocrine cells of the small intestine regulate pancreatic function?
Hormonal:
Enteroendocrine (EE) cells in the duodenum
- Secretin: Promotes secretion of bicarbonate
- Cholecystokinin (CCK), Gastrin: Stimulates exocytosis of zymogens
Neural:
- Stimulation of the Vagus n. (CN X)
- Anticipation of a meal
What structure is shown here?
Islets of Langerhans:
- Concentrated in the tail portion
- Pale-staining
- Clusters of cells
- Fenestrated capillaries; Secretes into these
Function:
- Maintain stable blood glucose levels
Describe the breakdown of endocrine cells in the pancreatic islets
a cells: (20%) Glucagon
B cells: (70%) Insulin
d cells: (<10%) Somatostatin
PP cells: (Rare) Pancreatic Polypeptide
Describe the functions of the liver
Functions:
-
Synthesis of plasma proteins
- Albumins, clotting factors, apolipoproteins, transferrin
-
Nutrient processing/storage
- Glycogenolysis
- Synthesis of glucose from non-CHO sources during starvation (gluconeogenesis)
- AA metabolism/urea cycle (removed by kidneys)
- Energy storage (glucose/triglycerides)
- Vitamin A, Fe storage
- Bile synthesis
- Toxin detoxification
-
Structure-function: Major interface with the blood
- 75% of blood comes from the hepatic portal vein
- Stomach/small intestine
- 25% is from the hepatic artery: Oxygen supply
- 75% of blood comes from the hepatic portal vein
What is the functional unit of the Liver?
Functional Unit: Hepatic lobule
- Plates of hepatocytes radiating from a central venule
- Surrounded by sinusoids
- Bounded peripherally by 3 to 6 portal triads.
- Branch of hepatic artery (oxygen)
- Branch of portal vein (from GI)
- Branch of bile duct
Bile Flow & blood flow in opposite directions*
- Blood: Portal -> Central v.
- Bile: Canaliculi -> Portal
What structure is shown?
Portal Triad
Venule
- Thin walled
- Large lumen
Arteriole
- Smooth m.
- Smaller than venule
Bile Duct
- Simple Cuboidal epi.
ID structures present
What is ID’ed in blue in this image of Liver tissue?
Sinusoids:
•Fenestrae are clustered into Sieve plates
Kupffer cells:
- Permanent liver resident
- Patrol the lining
- Phagocytize & digest old RBCs
Describe the pathway between blood cells to the hepatocytes
Space of Disse: (AKA Perisinusoidal space)
- Space between ECs & hepatocytes
- Hepatocytes: Numerous microvilli
- Bathed in plasma
- Contains hepatic stellate cells (aka Ito cells)
- Stores vitamin A
- HSCs are pericytes (contractile cells surrounding capillaries)
What is Bile?
Function?
Synthesis?
Bile:
Function:
- Emulsifies lipids, promoting easier digestion by [lipases]
Components:
- Cholesterol
- Salts
- Bilirubin (RBC breakdown product)
Bile Formation:
- Hepatocytes synthesize & secrete Bile within Bile canaliculi
- Space between 2 adjacent hepatocytes
- Drain into bile ducts
What structure is displayed?
Bile Duct: S.Cuboidal
Hepatic Summary
Portal Triad:
- Deoxygenated & Oxygenated Blood combine & flow to Central v.
Kupffer cells:
- Patrol sinusoids for sinescent cells
Space of Disse:
- Space between hepatocytes & endothelial lining
- Stellate (ito) cells within
Bile:
- Synthesized in Bile canaliculi and flows to Portal Triad
What is in the image?
Gallbladder:
Function:
- Stores & concentrates bile from the liver until needed
Anatomical Layers:
Folded mucosa:
- Simple columnar epith; Basal Nuclei
- LP
Muscularis
Adventitia
Regulation:
- Fat stimulates CCK release (EE/sm intest)
- SM contraction
- Bile released into duodenum
Describe the Enterohepatic circulation
Recycling of bile acids:
- Most: small intestine
- Some: large
Clinical significance:
- Hepatoxicity of some drugs
- Digestive problems in IBD due to recycling defects
