Digestive System 1 Flashcards
What is the digestive system composed of?
the alimentary canal, its associated organs and exocrine glands.
organs- teeth, tongue
glands- salivary glands, liver, pancrease
What is the digestive system?
A system which includes both tubular and parenchymal organs.
- alimentary canal + all other parenchymal organs
What is the digestive tract? What is its different name?
name: ALIMENTARY CANAL
- includes only the organs in the digestive system which are tubular.
- eg. mouth, esophagus, stomach, intestine, etc.
What do all organs in the digestive tract have in common?
lumen
What does the digestive tract begin with?
lips and cheeks
What are lips and cheeks?
Folds of tissue with:
- skin on the external surface,
- mucous membrane adjacent to the oral cavity.
What is the structure of the mucous membrane in the lips and cheeks?
stratified squamous epithelium
keratinized in ruminants and horses
What is the difference between species in the lips and cheeks?
Ruminants and horses have a keratinized stratified squamous epithelium.
What does the underlying tissue of the cheeks and lips contain?
Tissue underlying the stratified squamous epithelium contains:
- serous or mixed glands
- skeletal muscle
What skin tissue lines the body? What skin tissue lines the internal surfaces of the mouth?
stratified squamous epithelium
What is the difference between the stratified squamous epithelium in different species?
the level of keratinization:
- cats and dogs eat meat (not rough food) –> does not damage the internal surface of the mouth –> not keratinized
- ruminants and horses eat rough food –> keratinized
What does the keratinization of tissue do?
gives additional protection features
What does the keratinization level of epithelium depend on?
- different species (their diets)
- individuals
Explain another reason why certain species may have keratinized epithelium in the mouth.
- adaptation reaction
- epithelium becomes keratinized to be protected from specific food.
What does the keritinization of stratified squamous epithelium depend on?
- species
- individual (adaptation reaction)
Why is the epithelium in the mouth stratified and not simple?
If the epithelium was simple, then it would be too thin, and it would get damaged every time that food was injested.
What is the thickest type of epithelium (from all epithelium classes)?
stratified squamous epithelium
What are the two types of palates?
- hard
- soft
Explain the structure of the hard palate.
- keratinized
- stratified squamous epithelium
- located on the surface with underlying connective tissue that blends with the periosteum of the palate bones.
What does the hard palate connect with?
connective tissue which blends with the periosteum of the palate bones.
What is the function of the dental pad?
It functions in place of upper incisors in ruminants.
What does the dental pad have?
Very thick keratin.
What is located further caudally in the oral cavity?
the soft palate
Explain the structure of the soft palate.
Mucous membrane fold with:
- respiratory epithelium (nasal side)
- stratified squamous epithelium (oral side)
What is special about the soft palate?
It is a fold which seperates two differerent systems:
- alimentary system (digestive tract)
- respiratory system
What is skin mobility based on?
Connective tissue beneath the epithelium.
Why is the hard palate not movable?
There is no connective tissue below the epithelium which allows for movement.
Can the dental palate be moved? Why?
Cannot be moved!
- does not have connective tissue below the epithelium
What is the dorsal epithelium of the tongue?
stratified squamous epithelium
What does the dorsal stratified squamous epithelium of the tongue vary in?
the degrees of keratinization
Explain the structure of the ventral epithelium of the tongue.
thin and non-keratinized
What is the difference between the dorsal and ventral epithelium of the tongue?
dorsal- thick and keratinized
ventral- thin and non-keratinized
What does the tongue additionally have? Where are they located?
Papillae (varous small outgrowths), located on its upper surface
What are papillae?
various small outgrowths
What do papillae vary in?
- size
- appearance
Explain a difference in size and appearance of papillae. include names!
filiform: threadlike projections or bear spines
circumvallate/fungiform: cushion shaped
foliate: take the form of a succession of folds
What do filiform papillae have unique to them?
threadlike projections or bear spines
What do circumvallate / fungiform papillae have unique to them?
cushion shape
What do foliate papillae have unique to them?
take the form of a succession of folds
Where are taste buds located?
In the epithelium of circumvallate, foliate and fungiform papillae.
What tissue is the tongue made out of? What is special?
- striated skeletal muscle tissue
- fibers go in various directions
What is the tongue made out of? core? top-later?
core: striated skeletal muscle
top-layer: striated squamous epithelium
Why is the ventral part of the tongue smooth?
ventral part = smooth because it is not keratinized
Why is the tongues top part rough?
- keratinized epithelium
- small projections (papillae)
What type of structures are papillae?
macroscopic structures (not histological!)
- can be seen by the naked eye (–> anatomy)
Do papillae have multiple features??
they can be ‘taste buds’, yet
some are just mechanical.
What are taste buds?
Organs associated with the sense of taste.
Explain the map of taste buds.
No such map!
All taste buds are scattered around the tongue equally.
- thresholds may be different (speed of feeling senses)
Why do cats have such a rough tongue?
a great proportion of filliform papillae (projections).
needed to clean their fur, and drink water (water droplets lifted)
What is the function of papillae in cats?
1) clean fur
2) drink water (direct water droplets)
3) detatch muscle from the bone during eating (big cats only!)
licking meat detaches meat from bone.
What type of organ is a taste bud?
sensory organ
chemical compounds trigger taste buds causing one type of chemical energy to be transformed into electrical energy (impulse sent to the brain).
What substances are teeth composed of?
- enamel
- dentine
- cementum
What is enamel? What does it form?
- hardest substance in the body
- forms the outer surface of the crown of brachydont teeth
What is dentine? What does it form?
- composed of tubules of collagen fibers and mineral
- lies deep to the enamel
What is known as the neck region of the tooth?
where the crown narrows just below the gingival surface.
What is the gingival sulcus?
The space between he neck of the tooth and surrounding gingiva
What is cementum? What does it cover?
- substance made out of collagen and mineral
- covers the outer surface of the tooth root
Is a tooth similar to a bone?
no. nothing is similar.
It is an organ of the digestive system.
What are the two parts of a tooth? What are they covered by?
crown (covered by enamel)
root (covered by a thin later of cementum)
both parts have dentine and pulp.
What is the pulp of the tooth?
A connective tissue with all nerves and blood vessels.
What is dentine made up of?
- ODONTOBLASTS
- 90%** type I collagen**
- 70% (wetweight) hydroxypatite
What is enamel made up of?
- AMELOBLASTS (tall columnar cells)
- 96% is mineralized:** crystals/prisms of calcium phosphate**
When is enamel produced? Explain. What produces enamel? What happens when it dies?
Enamel is produced before the tooth erupts.
Each ameloblast has a Tomes process (elongated tip) that secretes the organic matrix of the enamel rod.
When ameloblasts die (when the tooth errupts), the enamel layer cannot be repaired.
What secretes the organic matrix of an enamel rod?
Tomes process (tip of ameloblast).
What cells produce dentine and enamel respectfully?
odontoblasts and ameloblasts
What is harder dentine or enamel?
Final pattern of enamel is similar due to the multiple processes of calcium phosphate.
almost no water (all mineralized = hardest substance in the body.
enamel is the hardest substance in the body as it has almost no water (all mineralized). Dentine is softer as it has water particles.
balance between organic and inorganic elements is not equal
When do ameloblasts die?
When the tooth errupts (go up from the gums).
Explain cementum. What is it composed of?
- produced by CEMENTOBLASTS
- 45%-50% hydroxylapatite (inorganic material)
- 50%-55% water by weight (organic material)
Slightly softer than dentin
What type of teeth are brachidont?
most general type of teeth.
covered by enamel from the outermost part of the crown.
What teeth (species) are hypsodont teeth?
all equine teeth
the porcine canine tooth
some bovine teeth
What is the outer surface of hypsodont teeth formed by?
cementum which overlies the enamel.
What makes up the center of equine teeth? What occurs? What is formed?
the cementum invaginates into the enamel and dentine.
forms the INFUNDIBULUM
center of teeth
What invaginates into what in equine teeth?
the CEMENTUM invaginates into the enamel and dentum.
What is the major difference between the hypsodont tooth and the other.
In the hypsodont tooth, the cementum is the outermost layer in the entire tooth (root and crown).
Why is cementum being the outermost layer of the tooth so important?
- makes an extra layer in the teeth for wear and tear.
- horses and cows eat ROUGH FOOD–> teeth have extra layer of substances.
How can one tell the age of a horse looking at its teeth?
The amount/layer of cementum reflects the age of the horse (amount eaten in lifetime).
How can one classify the secretory adenomeres of salivary glands? What is the classification based on?
- serous
- mucous
- mixed
based on the epithelial cell types.
Explain serous salivary adenomeres of glands. What do they contain?
- contain apical, acidophilic zymogen granules:
- stored protein
- polysaccharide precursors of saliva
Explain mucous salivary adenomeres of glands. What do they contain?
- light-staining cytoplasm
- basal nucleus
Explain mixed salivary adenomeres of glands. What do they contain?
can have either/or:
- intermixed regions of serous and mucous cells
- mucous cells with surrounding serous demilunes.
Where to does the salivary duct open?
The final salivary duct opens to the mouth.
What is an adenomere? What does it do?
- the secretory, end part of a salivary gland
- it produces the secretions
What does the type of adenomere (name) depend on?
the substance that the adenomere is producing.
- serous: watery substance (with proteins and carbohydrates)
- mucous: slippery material (multiple different substances: glucoproteins, immunoglobulins, antimicrobial enzymes, inorganic salts, etc.)
- mixed: both
How does the typical serous cell look in comparison to the other secretory adenomeres? Colour? Nucleus?
darker.
- typically dyed in the pink colour (because it is acetophyllic)
- nucleus of the cell is always in the middle
How does the typical mucous cell look in comparison to the other secretory adenomeres? Colour? Nucleus?
- typically dyed in the white colour
- nucleus of the cell is always on the bottom
What two aspects allow to distinguish between the different secretory adenomeres?
- colour (cells are dyed)
- location of nucleus
How do mixed cells look like? Why? What colour?
SEROUS DEMILUNES (look like a half of a moon)
(moon is pink, remaining part is white)
What cells surround the secretory units? What do they do?
Myoepithelial cells:
- surround the secretory units (end parts of the gland)
- contract to assist discharge of the salive into the duct system
What properties do myoepithelial cells have?
both those of epithelial and muscle cells.
Explain the release of saliva in the salivary glands.
- saliva is usually over produced, (more is produced then can be held within the duct system) and therefore it is automatically expelled.
- myoepithelial cells assist the secretion of saliva
What does the intralobular portion of the salivary gland duct system begin with? What is it lined by?
begins with a short intercalated duct, which is lined by simple cuboidal epithelium.
What does the cuboidal epithelium continue as in the intercallated duct? With what? Where?
the simple cuboidal epithelium continues as simple columnar epithelium with extensive basal plasma membrane infoldings in the STRIATED DUCT.
What is unique to the salivary gland duct system?
striated ducts
What do striated ducts empty into? What follows?
interlobular ducts which are followed by lobular ducts.
What changes in the epithelium in the larger ducts?
epithelium height increases: simple cuboidal —> simple columnar —> stratified columnar
What is special about salivary glands?
very big network of ducts.
