1/2- intro + salivary gland, esophagus, stomach histo

chief goal of GI

break down macromolecules (proteins, fats, starch) → smaller molecules (amino acids, fatty acids, glucose) to be absorbed

3 fundamental processes of GI

1. secretion: delivery of enzymes, mucus, ions into lumen + hormones into blood

2. absorption: transport of water, ions, nutrient from lumen → across epithelium → blood

3. motility: contractions of smooth muscle in the wall of the tube that crush, mix, propel contents

7 organs of the GI in order

1. mouth

2. esophagus

3. stomach

4. liver

5. pancreas

6. small intestine

7. large intestine

which GI organ does not provide any digestive function

esophagus

3 major salivary glands

1. parotid

2. submandibular

3. sublingual

3 minor salivary glands

1. labial

2. palatine

3. pharyngeal

what % of saliva is secreted from the major salivary glands

90+%

what % of mucous is secreted from the minor salivary glands

~70%

4 ways saliva provides protection

1. moistens/lubricates oral mucosa

2. prevents drying

3. flush/cleanse/protects teeth

4. facilitates speech

2 ways saliva provides buffering

1. neutralizes acids

2. maintains pH through HCO₃^-

2 types of units found in salivary glands

1. serous

2. mucous

differentiate serous vs. mucous

• serous: acinar (grape shape), watery fluid, darker stain

• mucous: tubular, viscous fluid, lighter stain w/ squished nuclei

which gland has mostly serous units

parotid

which gland has more serous than mucous units

submandibular

which gland has more mucous than serous units

sublingual

what is this

submandibular gland (note: more serous than mucous)

what is this

parotid (note: mostly serous units, no mucous pictured)

what is this

sublingual gland (note: more mucous than serous)

what is this

parotid gland

what is this

submandibular gland

what is this

sublingual gland

what are the 3 ducts found in all major salivary glands

intralobular ducts:

1. intercalated: simple cuboidal epithelium

2. striated: simple columnar epithelium

interlobular ducts:

1. excretory: psuedostratified epithelium

how do you differentiate between intercalated vs. striated ducts

• intercalated: cannot distinguish a cell’s boundary

• striated: can distinguish a cell’s boundary

what’s the blue + green label

• blue: intercalated duct

• green: striated ducts

why are striated ducts “striated”

basal lamina (basement membrane) infoldings in between the mitochondria

what are the big pink circles

striated ducts

what are the numbers

1. excretory duct (interlobular) (note: pseudostratified epithelium)

2. striated duct (intralobular)

3. lymphoid tissue

4. serous acinar

5. mixed acinar

6. artery

7. vein

what are myoepithelial cells

branching cells w/ actin + myosin that wrap their processes around secretory cells to expel secretions

what’s the yellow

myoepithelial cell processes using actin stain

what’s the circular structure in the center

striated duct

which minor salivary gland has serous excretions

Ebner (gustatory) glands

Ebner glands are located near which papillae

vallate + foliate papillae

identify the Ebner glands in this image

what’s the 3rd most common autoimmune disease

Sjogren’s

identify the labial glands in this image

what’s Sialolithiasis

formation of calculi or mineralized concretion that blocks a salivary duct

4 layers of the esophagus inside → out

1. mucosal lining

2. submucosa

3. muscularis externa

4. adventitia/serosa: thorax/abdominal cavity

3 things that make up the mucosal lining of the esophagus

1. simple stratified non-keratinized epithelium (SSNKE)

2. lamina propria

3. muscularis mucosae

2 things that make up the submucosa of the esophagus

1. loose CT

2. esophageal glands

2 things that make up the muscularis externa of the esophagus

1. inner circular muscle

2. outer longitudinal muscle

what type of muscle is in the muscularis externa of the esophagus

• upper 1/3 of esophagus: only skeletal muscle

• middle 1/3: skeletal/smooth mixed

• lower 1/3: only smooth

what are the numbers

cross-section of esophagus:

1. SSNKE lining

2. mucosa

3. muscularis mucosa

4. submucosa

5. muscularis externa

6. adventitia/serosa

what are the numbers

cross-section of esophagus:

1. SSNKE

2. lamina propria

3. muscularis mucosa

4. submucosa

what are the letters

• A: mucous unit of esophageal submucosal glands

• B: serous unit

what the boundary between the esophagus + stomach

zigzag line: squamocolumnar mucosal junction

what’s Barrett’s esophagus

abnormal squamocolumnar mucosal junction where SSNKE of esophagus turns into gastric/intestinal epithelium

what is this + what are the numbers

normal squamocolumnar mucosal junction

1. esophageal epithelium

2. gastric (stomach) epithelium

what is this + what are the letters

gastroesophageal junction

• A: mucosa associated lymphoid tissue (MALT)

• B: surface mucous cells

• C: gastric pit

• D: muscularis mucosa

4 layers of the stomach (inside → out)

1. mucosa

2. submucosa

3. muscularis externa

4. serosa (mainly)/adventitia

which has no glands: mucosa or submucosa of stomach

submucosa

what 3 muscles are in the muscularis externa of the stomach

1. inner oblique (limited)

2. middle circular

3. outer longitudinal (limited)

3 types of stomach mucosal glands

1. cardial gastric

2. gastric glands proper (fundic)

3. pyloric

what type of cells are found in fundic glands of the stomach

1. mucous neck

2. stem

3. parietal

4. zymogenic chief

5. enteroendocrine

what’s important in this image

stomach surface mucous cells which cover inner surface + gastric pits

what type of stomach mucosal gland is pictured

gastric glands proper (fundic)

what are the numbers

fundic gland:

1. surface mucous cell

2. opening of gastric pit

3. surface mucous cell of pit

4. parietal cell

5. mucous neck cell

6. zymogenic (chief) cell

7. lamina propia

8. parietal cell (polyploid)

what are the arrows pointing to

parietal cells of fundic glands (note: egg appearance, abundant mitochondria, pink cytoplasm)

function of parietal cells in stomach

secretes:

1. HCl

2. intrinsic factor (for vitamin B12 absorption)

what are the arrows pointing to

zymogenic chief cells (note: basophilic cytoplasm)

function of zymogenic chief cells

secrete pepsinogen + lipase

which muscle of the stomach muscularis externa is used for churning

inner oblique

what are the numbers

stomach layers:

1. mucosa

2. submucosa

3. muscularis externa

4. serosa

which one is improperly matched

b. gastric glands are in mucosa

what are the letters

fundic gland of stomach:

• A: parietal cell

• B: chief cell

• C: gastric pit