Microvilli and Digestive System Functions

65 Questions

What type of muscle is found in the muscularis layer of the stomach?

Smooth muscle

Which region of the stomach has an abundance of mucus glands?

Cardia region

What is the function of chief cells in the stomach?

Secretion of pepsinogen

What is the name of the folds in the mucosal layer of the glandular stomach?

Rugae

Which type of teeth continue to grow after eruption?

Hypsodont teeth

What is the function of parietal cells in the stomach?

Secretion of HCl

Which layer of the esophagus contains mucous glands?

Submucosa

What is the name of the structure that increases the surface area of the stomach?

Rugae

What type of epithelium is found in the mucosa of the oral cavity?

Stratified squamous epithelium

What is the main function of the parotid gland?

To produce serous secretions

What is the function of the cementum in teeth?

To cover the entire external surface of the tooth below the gumline

What is the function of the odonotoblasts in teeth?

To form the dentin of the tooth

What is the characteristic of brachydont teeth?

They are short and cease to grow after eruption

What is the function of the periodontal ligament in teeth?

To hold the tooth in place in the socket

What is the function of the fibroblasts in the periodontal ligament?

To form the periodontal ligament

What is the function of the mucosa in the oral cavity?

To provide a protective layer for the oral cavity

What is the primary function of the Brunner's glands in the submucosa of the duodenum?

Producing alkaline mucus to protect from acidic chyme

What type of epithelium is found in the anus?

Stratified squamous epithelium

What is the primary function of the hepatocytes in the liver?

All of the above

What type of epithelium is found in the ileum?

Simple columnar epithelium

What is the function of the Kupffer cells in the liver?

To remove aged blood cells and pathogens from the blood

What is the function of the Ito cells in the liver?

To metabolize vitamin A and produce collagen

What is the main function of the large intestine?

Water absorption and electrolyte balance

What is the function of the omasum in the digestive system?

Squeezing and liquifying ingesta to move it to the abomasum

What is the primary function of M cells in the digestive system?

Sampling antigens from the lumen environment

What is the function of the submucosal gland in the digestive system?

Secretion of mucus to facilitate movement of particles

What is the function of the myenteric plexus in the digestive system?

Controlling GI tract motility

What is the function of the hepatic acinus in the digestive system?

Supplying oxygenated blood to hepatocytes

What is the characteristic of the mucosa of the reticulum?

Non-glandular keratinized stratified squamous mucosa

What is the primary function of the perisinusoidal space?

To facilitate exchange between blood and hepatocytes

What is the location of the central vein in the liver?

At the center of hepatic lobules

What type of epithelium lines the bile ducts?

Short columnar epithelium

Which of the following is NOT a function of the gallbladder?

Producing bile

What is the type of epithelium found in the rumen of the ruminant stomach?

Stratified squamous epithelium

What is the function of the pancreatic polypeptide?

To regulate pancreatic secretions

Which of the following enzymes is NOT produced by the exocrine pancreas?

Insulin

What is the characteristic of the connective tissue in the pancreas?

Thin connective tissue capsule with trabeculae and VANs

What is the function of the lacteal in the digestive system?

Blind-ended lymphatic vessels in the intestinal villi

What is the characteristic of the mucosa of the reticulum?

Non-glandular and keratinized

What is the location of the anal sacs in the digestive system?

Between the internal and external anal sphincters

What is the main function of the rugae in the glandular stomach?

To increase the surface area of the stomach

Which type of teeth do ruminants have?

Hypsodont teeth

What is the function of the muscularis layer in the stomach?

To mix and churn food

Which layer of the esophagus contains mucous glands?

Submucosa

What is the function of the chief cells in the stomach?

To produce pepsinogen

What is the function of the gastric pit in the stomach?

To denote entrances to the tubular-shaped gastric glands

What is the function of the adventitia layer in the esophagus?

To connect the esophagus to surrounding tissues

What is the primary function of the Brunner's glands in the duodenum?

Produce alkaline mucus to protect from acidic chyme

What type of epithelium is found in the rectum?

Simple columnar epithelium

What type of epithelium lines the bile ducts in the liver?

Cuboidal epithelium

What is the function of the ileum in the small intestine?

House Peyer's patches of the lymphatic system

What type of epithelium is found in the anus?

Stratified squamous epithelium

What type of epithelium is found in the mucosa of the ruminant stomach?

Stratified squamous

What is the function of the rumenal papillae?

To absorb volatile fatty acids

What is the percentage of the pancreas that is endocrine?

What is the function of the central vein in the liver?

To receive blood mixed in the liver sinusoids and return it to circulation

What is the characteristic of the connective tissue in the pancreas?

Thin and delicate

What is the function of the pancreatic polypeptide?

To regulate pancreatic secretions

What tissues are endoderm derived?

Epithelium, parenchymatous organs (e.g.liver and pancreas) and associated glands.

What type of lining epithelium is noted from the lips to the nonglandular stomach?

Stratified squamous epithelium

What type of lining epithelium lines the glandular stomach and intestine?

Simple columnar epithelium

Which of the following are components that form the oral cavity?

Lips, cheeks, tongue, pharynx palate

Match the following epithelium to its appropriate cavity/organ.

Oral cavity = Stratified squamous epithelium Tongue = Stratified squamous epithelium, keratinized on dorsal side Esophagus = Non-keratinized or keratinized stratified squamous epithelium Glandular stomach = Simple columnar

Which of the following are the four tissues that make up the periodontium?

Gingivae, periodontal ligament, cementum , alveolar bone

Which gland is predominantly mucous, but is still a mixed gland?

Sublingual

Study Notes

Microvilli and Cellular Functions

Microvilli are microscopic cellular membrane protrusions that increase surface area for diffusion and minimize volume increase
Involved in various functions, including absorption, secretion, cellular adhesion, and mechanotransduction

Digestive System Components

Oral Cavity:
- Mucosa: stratified squamous epithelium (keratinized or non-keratinized)
- Submucosa
- Salivary glands and tonsils
Salivary Glands:
- Major glands: parotid (serous), sublingual (mostly mucous), mandibular
- Stromal components: connective tissues, VANs, and lymph
- Parenchymal components: secretory units (adenomere), ducts
- Minor glands: lingual, palatal, labial, buccal, zygomatic (carnivores), molar (cats)
- Types of secretions: mixed, serous, mucous
Tongue:
- Mucosa: stratified squamous epithelium (keratinized on dorsal side)
- Dorsal aspect has gustatory and mechanical papillae
- Muscularis: skeletal muscle in 3 directions (longitudinal, transverse, and vertical)
Teeth:
- Layers:
  - Enamel: covers entire external surface above gumline
  - Cementum: covers entire external surface below gumline
  - Dentin: beneath enamel and cementum
  - Pulp: loose connective tissue and VANs
  - Periodontal ligament
- Types of teeth:
  - Brachydont: short and cease to grow after eruption
  - Hypsodont: tall and continue to grow after eruption
Esophagus:
- Epithelium: non-keratinized stratified squamous
- Lamina propria
- Muscularis mucosa
- Submucosa: contains mucous glands
- Muscularis: skeletal or smooth muscle (depending on species)
- Adventitia
Stomach:
- Gastric pit: indentations in stomach with entrances to tubular-shaped gastric glands
- Rugae: folds in mucosal layer to increase surface area
- Glandular stomach:
  - Mucosa: simple columnar with gastric pits
  - Muscularis: inner oblique, middle circular, outer longitudinal
  - Serosa
  - Regions:
    - Cardia region: entrance into stomach with many mucus glands
    - Fundus: proper gastric glands
    - Pylorus region: exit to duodenum with mucus glands and endocrine G cells
Small Intestine:
- Layers:
  - Epithelium: simple columnar (enterocytes and goblets)
  - Lamina propria: creates villi and microvilli
  - Muscularis
- Function: nutrient absorption and mucus secretion
- Areas:
  - Duodenum: Brunner's glands in submucosa produce alkaline mucus
  - Jejunum
  - Ileum: Peyer's patches (lymphatic system)
Large Intestine:
- Function: water absorption
- Simple columnar epithelium
- NO villi (intestinal crypts present)
Rectum:
- Simple columnar epithelium
- Functions: stores feces, secretes mucus
Anus:
- Stratified squamous epithelium
Liver:
- Components:
  - Hepatocytes: polygonal epithelial cells (detox, bile synthesis, gluconogenesis, energy storage)
  - Intrahepatic biliary tree: canals and ducts lined by cuboidal epithelium
  - Kupffer cells: phagocytes of liver (remove aged blood cells, pathogens, and toxins)
  - Sinusoid: capillaries with discontinuous basement membrane and epithelium
  - Perisinusoidal space (space of Disse): site of exchange between blood and hepatocytes
  - Central vein: found at center of hepatic lobules, receives blood mixed in liver sinusoids
Gallbladder:
- Concentrating/modifying reservoir for bile that dumps into duodenum via major and minor papillae
- Horse has NO gall bladder
- Mucosa:
  - Bile ducts lined by short columnar epithelium
  - Gall bladder lined by tall columnar epithelium
- Smooth muscle
- Serosa
Pancreas:
- Stroma:
  - Thin connective tissue capsule, trabeculae with VANs and lymph vessels (pacinian corpuscles)
- Parenchyma:
  - Exocrine: 95% of parenchyma (serous acinar glands producing zymogen granules)
  - Endocrine: 5% of parenchyma (islet of Langerhans, secretes insulin, glucagon, somatostatin, pancreatic polypeptide)

Ruminant Stomach

Mucosa of ruminant stomach:
- Non-glandular keratinized stratified squamous containing papillae
- Largest compartment: absorption of volatile fatty acids, mixing, regurge, eructation, movement of ingesta
Rumen:
- Non-glandular keratinized stratified squamous
- Function: absorption of volatile fatty acids, mixing, regurge, eructation, movement of ingesta
Reticulum:
- Non-glandular keratinized stratified squamous, honeycombed shape mucosa
- Function: absorption of volatile fatty acids, mixing, regurge, eructation, movement of ingesta
Omasum:
- Non-glandular keratinized stratified squamous
- Function: squeezes ingesta, liquifies and moves it to the abomasum
Abomasum:
- Glandular stomach

Definitions

M cell: specialized epithelium that samples antigens from the lumen environment
Intestinal crypt: site of stem cell regeneration
Absorption: movement of nutrients, water, and electrolytes from lumen into blood
Goblet cell: type of intestinal mucosal epithelial cell
Lacteal: blind-ended lymphatic vessels in intestinal villi
Submucosal gland: secretes mucus to facilitate movement of particles along tubes
Myenteric plexus: major nerve supply to GI tract, controls GI tract motility

Anorectal Junction and Associated Structures

Anorectal junction: site where rectum joins anus
Circumanal glands: present in subcutis around anus in dogs
Anal sacs: reservoir for anal gland material, keratinized stratified squamous epithelium
Anal glands: apocrine secretion in dogs, sebaceous and apocrine in cats

Ruminant Stomach

Function:
- Absorption of volatile fatty acids
- Mixing
- Regurge
- Eructation
- Movement of ingesta

Reticulum

Mucosa:
- Non-glandular keratinized stratified squamous
- Honeycombed shape
Function:
- Absorption of volatile fatty acids
- Mixing
- Regurge
- Eructation
- Movement of ingesta

Omasum

Mucosa:
- Non-glandular keratinized stratified squamous
Function:
- Squeezes ingesta
- Liquifies and moves it to the abomasum

Abomasum

Mucosa:
- Glandular stomach
Function:
- Not specified

Definitions

M cell:
- Specialized epithelium that samples antigens from the lumen environment
Absorption:
- Movement of nutrients, water, and electrolytes from the lumen of the small intestine into the cell, then into the blood
Goblet cell:
- Type of intestinal mucosal epithelial cell
Lacteal:
- Blind-ended lymphatic vessels in the intestinal villi
Submucosal gland:
- Secrete mucus to facilitate the movement of particles along the body's various tubes
Myenteric plexus:
- Major nerve supply to the gastrointestinal tract and controls GI tract motility

Anorectal Junction

Anorectal junction:
- Line
Sphincters:
- Not specified
Circumanal glands:
- Present in the subcutis around the anus in dogs
Anal sacs:
- Reservoir for anal gland material
- Keratinized, stratified squamous epithelium
- Located between the smooth muscle of the internal anal sphincter and the skeletal muscle of the external anal sphincter

Hepatic Lobule

Hepatic acinus:
- Supplies oxygenated blood to hepatocytes
Epithelium:
- Simple columnar (enterocytes and goblets)
Lamina propria:
- Creates the villi and microvilli
Intestinal crypts:
- At the base of villi (similar to gastric pits)
Mucularis:
- Not specified
Function:
- Nutrient absorption and mucus secretion
Areas:
- Duodenum:
  - Brunner's glands in the submucosa produce alkaline mucus to protect from acidic chyme from the stomach
- Jejunum:
  - Not specified
- Ileum:
  - Peyer's patches (lymphatic system)

Large Intestine

Function:
- Water absorption
Epithelium:
- Simple columnar
NO villi:
- Intestinal crypts present

Rectum

Epithelium:
- Simple columnar
Function:
- Stores feces and secretes mucus

Anus

Epithelium:
- Stratified squamous

Liver

Components:
- Hepatocytes:
  - Polygonal epithelial cells
  - Function:
    - Detox
    - Bile synthesis
    - Gluconogenesis
    - Energy storage
- Intrahepatic biliary tree:
  - Canals and ducts lined by cuboidal epithelium
  - Bile ducts in the portal triad
  - Oval cells: pluripotent stem cells
- Kupffer cells:
  - Phagocytes of the liver
  - Located within the blood sinusoids
  - Remove aged blood cells (hemosiderin), pathogens, and some toxins
- Sinusoid:
  - Capillaries of the liver with discontinuous basement membrane and epithelium
  - Pit cells: resident granular leukocytes
  - Ito cells: Vit.A metabolism, collagen production; contain large rounded lipid vacuoles

Esophagus

Epithelium:
- Non-keratinized stratified squamous
Lamina propria:
- Not specified
Muscularis mucosa:
- Not specified
Submucosa:
- Contains mucous glands
Muscularis:
- Skeletal or smooth muscle depending on the species
Adventitia:
- Not specified

Stomach

Epithelium:
- Gastric pit: indentations in the stomach that denote entrances to the tubular-shaped gastric glands
Rugae:
- Folds in the mucosal layer of the glandular stomach to increase surface area
Glandular stomach:
- Mucosa: simple columnar with gastric pits
- Muscularis:
  - Inner oblique
  - Middle circular
  - Outer longitudinal
- Serosa:
  - Not specified
- Regions:
  - Cardia region:
    - Entrance into the stomach
    - Lots of mucus glands
  - Fundus:
    - Magic happens here
    - Proper gastric glands
    - Chief cell:
      - Secrete pepsinogen - stains basophillic
    - Parietal cell:
      - Secrete HCl - stains eosinophillic
    - Endocrine G cell:
      - Produces gastrin - requires special staining
  - Pylorus region:
    - Exit to the duodenum
    - Mucus glands and endocrine G cells

Gallbladder

Function:
- Concentrating/modifying reservoir for bile that dumps into the duodenum via major and minor papillae
Horse:
- Has no gallbladder
Mucosa:
- Bile ducts lined by short columnar epithelium
- Gallbladder lined by tall columnar epithelium
Smooth muscle:
- Not specified
Serosa:
- Not specified

Pancreas

Stroma:
- Thin connective tissue capsule
- Trabeculae with VANs and lymph vessels (pacinian corpuscles)
Parenchyma:
- Exocrine:
  - 95% of the parenchyma
  - Serous acinar glands producing zymogen granules (eosinophilic)
  - Secrete:
    - Trypsinogen
    - Chymotrypsinogen
    - Lipase
    - Amylase
- Endocrine:
  - 5% of the parenchyma
  - Islet of Langerhans
  - Secrete:
    - Insulin
    - Glucagon
    - Somatostatin
    - Pancreatic polypeptide

This quiz covers the structure and functions of microvilli, and components of the digestive system including the oral cavity and salivary glands.

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