histology digestive system

what part of the digestive system is this?

Pharynx

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esophagus

1. squamous mucosa

2. mucosa

3. muscularis mucosa

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esophagus

1. squamous mucosa

2. submucosa

3. muscularis externa

4. adventitia/serosa

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esophagus

1. glands

2. extensive muscularis mucosae

3. epithelium (nonkeratinized stratified squamous)

4. sm

5. ?

6. inner circular muscle

7. outer longitudinal muscle

what part of the digestive system is this, and what is each number labeling?

esophagus

1. epithelium

2. blood vessels

3. lamina propria

4. muscularis mucosae

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esophagus

1. mucosa

2. muscularis mucosae

3. submucosa

4. duct

5. muscularis externa

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muscularis externa

1. inner circular muscle

2. myenteric plexus (Auerbach’s plexus)

3. outer longitudinal muscle

what is this slide showing?

what part of the digestive system is this, and what is each number labeling?

Gastroesophageal Junction

1. stomach

2. esophagus

3. fundic/gastric glands

4. cardiac glands

5. muscularis externa

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stomach

1. rugae

2. pits

what is this slide showing?

fundic/gastric glands

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cardiac gland

1. pit

2. gastric pits

3. cardiac glands

4. esophageal epithelium

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fundic mucosa/gland

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Pylorus - Stomach

1. gastric pits

2. pyloric glands

3. muscularis mucosae

4. submucosa

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*mm = muscularis mucosae

sm = submucosa

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transition from pylorus to duodenum

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what part of the digestive system is this, and what is each number labeling?

small intestine

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duodenum

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Paneth cells of small intestine

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Paneth cells of the small intestine

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Small intestine: Paneth cells

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what part of the digestive system is this, and what is each number labeling?

what part of the digestive system is this, and what are the green lines labeling?

jejunum

goblet cells

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what part of the digestive system is this, and what is each number labeling?

what part of the digestive system is this, and what is each number labeling?

Ileum

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Ileum

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Ileum

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colon (large intestine)

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Colon (large intestine)

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Colon

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Colon

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Colon (large intestine)

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Colon

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appendix

lymphatic nodules

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Appendix

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Lip

1. glands

2. skeletal muscle

3. skin

4. vermillion border

5. oral mucosa

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tongue

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teeth

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tooth

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Anorectal junction

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anal canal

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Pancreas

Main Duct

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Pancreas

Arrows: Pancreatic Acini

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Liver

1. capillary

2. portal vein

3. hepatocyte

4. bile duct

5. hepatic artery

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Gallbladder

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Gallbladder

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Gallbladder

Pharynx structure

epithelium: nonkeratinized stratified squamous

CT: areolar CT and elastic fibers in lamina propria

NO submucosa, muscularis mucosa, or adventitia serosa

Muscle: skeletal muscle wall

esophageal muscularis

• first and second section of esophagus are skeletal muscle, by the third section this changes to smooth muscle

  • between w 2 layers of smooth muscle in third section are nervous cells/myenteric plexus

• 1st and 2nd sections have adventitia, 3rd section has serosa

esophagus overall structure

• 3 sections, all nonkeratinized stratified squamous, all sections have same mucosa and have extensive muscularis mucosa

• tubular acinar glands line tract (mostly in submucosa), but this changes when get to gastroesophageal junction

• 2 sphincters (upper esophageal at top and stays closed when breathing, inferior esophageal before entering stomach to keep stomach contents in stomach)

esophageal visual ID

• thick muscle and glands (different from urinary ureters)

• tubuloacinar glands in esophagus to secrete mucous vs cardiac glands which are closer to junction/stomach

• 3rd section of esophagus has special glands

Myenteric/Auerbach’s Plexus

fxn: one of only places where nervous tissue is found in digestive system

structure: myelinated, loose areolar CT, visible neurons

location: between muscle layers

Gastroesophageal Junction

fxn: separate stomach and esophagus, important in trying to prevent esophageal cancer

structure:

• simple columnar epithelium running up and down pits (abrupt change from nonkeratinized strat squam in esophagus to simple columnar in stomach)

• start seeing cardiac glands

• adipose in submucosa and dense IR CT for multidirectional tension

location: between esophagus and stomach

Cardiac Glands

fxn: counter acidity of stomach by releasing more neutralizing/basic, important in trying to prevent esophageal cancer

structure: simple columnar and nonkeratinized epithelium, deep pits, homogenous

location: gastroesophageal junction and cardia portion of stomach

4 areas of stomach and their glands

1. cardia - cardiac glands

2. fundus - gastric glands

3. corpus - gastric glands

4. pylorus - pyloric glands

rugae

fxn: increase SA

structure: folds, gastric pits running in these

location: mostly in fundus and corpus of stomach

Gastric glands (fundic glands)

fxn: lots of cells doing different jobs

structure: shallow pits, heterogenous, rugae

location: fundus and corpus of stomach

pyloric glands

simple columnar epithelium, deep pits that are homogenous and they go all the way down to the muscle layer

(difference bw these and cardiac glands are that pyloric glands are simple columnar to simple columnar, while cardiac glands are simple columnar and nonkeratinized strat squam)

Pylorus of Stomach

end of stomach, pyloric sphincter, no abrupt junction of different epithelium, pyloric glands, mostly mucous cells, fairly prominent submucosa

*visual ID: look for smooth muscle change

Gastroduodenal Junction

• going from simple columnar epi in stomach to simple columnar with microvilli

• submucosa layer getting larger and pits getting shallower

  • pylorus has deeper pits while duodenum has shallow pit

  • submucosa has lots of glands and vessels

    • going from no glands in stomach to lots of glands in the intestine

Plicae Circulares

fxn: big projections in small intestine that give more SA

structure: villi (with crypts between) coming off of these projections, simple columnar epithelium lining surface villi (enterocyte, each enterocyte has tons of microvilli)

Small Intestine

fxn: absorption

structure: areolar CT, crypts of Lieberkuhn, cardio and lymph vasculature, lymph nodules and goblet cells

How to tell if vasculature in small intestine is lymph or cardio

look if there’s a RBC in capillary -

• if yes = regular cardio vasculature

• if no = lacteal

• slits = lymph

what are the specialized cells in the small intestines?

enteroendocrine cells - Paneth cells and AUPD cells

Paneth cells

fxn: release bacterial resistant, precursor to lysosome, immune protective

structure: red-looking cells at very bottom of crypts, may have some visible granules depending on stain used

location: crypts of small intestine

AUPD cells

fxn: endocrine function, release hormones to bloodstream, associate with gastrin

location: crypts in small intestine

what are the three sections of the small intestine?

duodenum, jujenum, and ileum

duodenum

fxn: neutralizing acid from stomach

structure: very long villi, Paneth cells, thick submucosa, BRUNNER’S GLANDS, 2 layers smooth muscle (1 circular and 1 longitudinal), serosa, lots of goblet cells

location: 1st section of small intestine

Jujenum

fxn: absorption

structure: NO brunner’s glands, tongue shaped villi (much shorter and fatter/pyramid shaped), small crypts, thin layer of submucosa

location: middle section of small intestine

Ileum

fxn: protection and stopping things that need to be stopped

structure: dome shaped villi, have Peyer’s Patches (bunch of lymphatic nodules) in lamina propria, have specialized M cells

location: bottom third of small intestine nearest the large intestine

M cell in ileum

specialized cells on the surface that present antigens to lymphocyte and macrophages in order to upregulate immune system; big bubble appearance

Large Intestine

fxn: last area for absorption

structure:

• epithelium: lots of simple columnar epithelium with lots of goblet cells

• stem cells and lymph nodules (b/c lots of bacteria)

• thick and continuous muscle called taenia coli, thick cord/drawstring-type longitudinal muscle layer

  • pulls in one direction

• front of large intestine has serosa while back area has adventitia

• deep crypts, muscularis mucosa, thick submucosa

• dense IR CT and vessels

  • still have Auerbach’s plexus if zoomed in enough

Appendix

fxn: special area of colon that acts as first line of defense for the colon/immune receptor

structure: crypts, absorptive cells, goblet cells, M cells carry over from small intestine (good differentiating structure), lots of lymph nodules, serosa

*can see clear muscle layers and can see whole cross section on one slide → great differentiating factor between appendix and colon

location: entrance into large intestine from small intestine

Rectum

simple columnar, small lumen, lamina propria, thick circular muscle layer, adventitia, start seeing valves, LOTS of goblet cells to help with movement

Rectoanal Junction and Anus

• going from simple columnar (rectum) to nonkeratinized stratified squamous (anal canal), then transition to keratinized stratified squamous when merged with integument on outside of body

• 2 sphincters with smooth and skeletal muscle next to each other

  • internal sphincter = extension of circular smooth muscle layer

  • external sphincter = what we control, skeletal muscle

Pancreas

• fxn: both endocrine and exocrine functions

  • endocrine: insulin, glucagon, etc. → islets releasing hormones

  • exocrine: secreting enzymes

• structure: lots of simple cuboidal epithelium, NO muscle, tightly packed cells with loose areolar CT, NO clear/mucous cells, have a big main duct

*easy to mix up with salivary glands

Gallbladder

fxn: store and concentrate bile, regulate release of concentrated bile, lots of osmosis

structure: small crypts, 3 layers

• mucosae: simple columnar epithelium, rugae (as gallbladder stretches the rugae go away), microvilli, lamina propria, no submucosa

• muscle: interwoven layer of smooth muscle (not distinct, interwoven)

• adventitia/serosa

Gall Stones

water follows sodium, so pumping sodium out means water will follow and leave = concentrating the bile → when bile from gallbladder gets too concentrated and calcified it forms gall stones

Liver

fxn: largest gland in body, filters stuff, main function is nutrient interconversion

structure: capsule surrounding organ, lobules

Portal triad of liver

structure: composed of portal vein, bile duct, and hepatic artery

location: at the corners of hexagonal lobules of liver

Bile duct

part of portal triad in liver, simple cuboidal epithelial tissue

hepatic artery

part of portal triad in liver, delivers oxygen and has smooth muscle

Lobules of liver

composed of central vein, portal triad, hepatic sinusoids, Kupffer cells, and hepatocytes

Hepatic sinusoids

sinusoids large, between cells

Kupffer Cells (Stellate Reticuloendothelial Cells)

fxn: specialized macrophages for liver

structure: flat/elongated

location: in walls/linings of sinusoids

Hepatocytes

fxn: make bile

structure: lines and rows of hepatocytes, bile canaliculi connect hepatocytes and collect/transport bile towards bile duct

layering of the GI tract (innermost to outermost)

mucosa, submucosa, muscularis externa, adventitia or serosa

adventitia vs serosa

adventitia - covering of GI tract found outside the peritoneal (abdominal) cavity, lacks a mesothelium and the connective tissue blends with surrounding connective tissues

serosa - covering of GI tract within the peritoneal cavity, continuous with mesentery and peritoneal lining of abdominal cavity, contains a mesothelial lining (simple squamous epithelial lining)

Lips

structure: internal surface is nonkeratinized stratified squamous and external surface is covered in thin skin, skeletal muscle

thin skin of lips

thin skin may contain hair follicles and sebaceous glands (but lacks sweat glands)

vermillion border (red vermillion zone)

area of lip that’s the junction of skin and mucosa

Papillae of tongue

mucosal structures lining dorsal surface of tongue and base of tongue, where tastebuds are located (except filiform papillae, these are the only ones without tastebuds)

• dorsal surface papillae: filiform papillae, fungiform papillae, foliate papillae

• base papillae: vallate papillae

what cells make up tastebuds

gustatory cells, supportive cells, basal stem cells, and immature gustatory cells

regions of the tooth

• crown - exposed tooth above gumline

• neck - narrowing at gumline

• root - extends below gumline into alveolar bone socket

• alveolus - tooth socket in bone

alveolus of tooth

• periodontal ligament: attach bone to bone, has Sharpeys fibers (collagen), anchors tooth firmly into alveolus, and allows slight movement of tooth under pressure of chewing

• Gingiva/Gum: covers alveolar bone

Dentin

calcified tissue that makes up most of tooth; has odontoblasts and odontoblast processes

layers of dentin

• odontoblasts: elongated cells that produce matrix of dentin; derived from mesenchymal cells of pulp cavity

• odontoblast processes: extensions of odontoblast which are used in secretion of pre-dentin (this is then mineralized into dentin)