Oral cavity and oesophagus Flashcards
what are Accessory digestive organs?
- Salivary glands
Biliary system – - Liver
- Gallbladder
- Exocrine pancreas
Exocrine organs lie outside the
digrestive tract
Exocrine organs lie outside the digestive tract and empty their
secretions through the ducts into the digestive tract lumen
primary function of digestion ?
makes nutrients absirbable
function of digestion mechanically?
Large foodstuffs broken down into smaller pieces to increase surface area for enzymes
function of digestion biochemically?
Broken down into small, simple compounds and molecules that can be absorbed from the digestive tract
energy source of digestion?
- ATP
- predominantly glucose
- Alternative = amino acids/fatty acids
building supplies of digestion?
Renewal and synthesis of body tissues
- Fatty acids
- Amino acids
Four Basic Digestive Processes
Motility
Secretion
Digestion
Absorption
what is motility ?
Muscular contractions that mix and move forward the contents of the digestive tract
what are the voluntary contractions ?
Mastication (chewing)
Deglutition (swallowing)
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what is secretion?
A number of digestive juices are secreted into the digestive tract lumen by exocrine glands
function of secretory cells?
Extract large volumes of water and raw materials from the blood plasma to produce their particular secretion
secretions are reabsorbed back into the…
blood after digestion.
function of endocrine cells in the digestive tract?
Endocrine cells within the digestive tract secrete gastrointestinal hormones into the blood that control digestive motility and exocrine gland secretion.
what kinds of things are secreted in the digestive tract?
Water
Electrolytes: : Na+, K+, Ca2+, Mg2+, HCO3 −, etc…
Specific organic constituents
- Enzymes, bile salts, or mucus
Large molecules cannot be absorbed across …
… plasma membrane of the cells lining the digestive tract
define digestion
biochemical breakdown of structurally complex foodstuffs into smaller, absorbable units.
Humans consume three energy-rich foodstuffs:
carbohydrates
protein
fats
Digestion is accomplished by
hydrolysis by enzymes within the Gastro-Intestinal (GI) tract
what breaks down starch and glycogen
salivary amylase
whart breaks down Short chain polysaccharides and disaccharides (maltose, lactose, sucrose) ?
pancreatic amylase
what breaks down Short chain polysaccharides and disaccharides (maltose, lactose, sucrose, α-Limit Dextrins) ?
Maltase, lactase, sucrase, α-limit dextrinase
what absorbs monosaccharised (glucose, fructose, galactose)?
Intestinal capillaries and hepatic portal system to liver
polysaccharides are a …
… glucose polymer
polysachharides linked by …
… O-glycosidic bonds
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whats hydrolysis
break down by water
water is added. a covalent bond between monomers is broken
Complex macromolecular foodstuffs are broken down by
enzymatic digestion
Hydrolysis adds
water across the covalent bonds holding the units together, freeing them for absorption.
Digestive enzymes are specific in
the bonds that they hydrolyse.
As food passes through the digestive tract, it is subjected to
various enzymes, which break down the food molecules into smaller absorbable units in a progressive step wise fashion.
In the small intestine, digestion is
completed and most absorption occurs.
describe absorption in the SI
The small products of digestion together with water, vitamins, and electrolytes are transferred from the digestive tract lumen into the blood or lymph.
is the digesticve tract internal or external?
This is external to the body
The pH of the stomach can reach as low as
pH 2 due to HCl secretion
The pH of the stomach can reach as low as pH 2 due to HCl secretion, yet in the body fluids the range of pH is
6.8 to 8
The digestive enzymes that hydrolyse food molecules could also
destroy the body’s own tissues that produce them.
In the lower part of the intestine live…
billions of bacteria that, if entering the body, may be extremely harmful.
Foodstuffs are complex foreign particles that
would be attacked by the immune system if in contact with the body.
what is the digestive tract?
Essentially a tube, 15 m in length in its normal contractile state (30 m ‘relaxed’)
the digestive tract is continuousfrom
mouth to anus.
Continuous from mouth to anus, therefore the contents of the digestive tract are
technically outside of the body.
Only after a substance has been absorbed across the digestive tract wall is it
considered part of the bodfy
Layers of the digestive tract wall
A cross section of the digestive tract reveals four major tissue layers:
- Mucosa
- Submucosa
- Muscularis externa
- Serosa
The digestive tract wall has the same
general structure throughout most of its length with some local variations characteristic of each region.
layers of the mucosa?
mucus membrane
lamina propria
muscularis mucosa
whats mucus membrane?
Inner epithelial layer, protective surface, modified in particular areas for secretion and absorption.
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whats submucosa?
Thick layer of connective tissue that provides elasticity and distensibility
what does the submucosa contain?
Contains the larger blood and lymph vessels which send branches inwards to the mucosal layer and outwards to the surrounding thick muscle layer.
what is the submucosa plexus?
Nerve network that has both sensory and motor neurons that regulate the activity of glands in the mucosa and smooth muscle of the muscularis mucosa.
how many neurons in the neteric nervous system?
500 million neurons
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what does the oral (buccal) cavity consist of?
Lips
Palate
Uvula
Tongue
lips function
Help procure and contain food in the mouth.
Sound articulation
the lips have an abundance of…
… sensory receptors (pressure, touch, stretch, temperature
the palate forms…
arched roof of mouth
the palate separastes?
mouth from nasal passages
the palate allows…
… simultaneous breathing and chewing/sucking
whats the uvula?
Dangling projection that seals nasal passages during swallowing.
whats the tongue?
- floor of oral cavity
- Voluntary muscle that guides food during chewing and swallowing.
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what do malocclusion affect?
Affects ability to bite, tear, and chew food
the different malocclusions?
excessive spacing
crowding
open bite
overbite
crossbite (front teeth)
cross bite (back teeth)
underbite
overjet
abnormal
Odontostomatologic anomaly is commonly seen in
congenital genetic disorders such as :
gardners syndrome
cleidocranial dysostosis
cleft lip and palate
functions of chewing?
To grind and break up food into smaller pieces
to mix food with saliva
to stimulate the taste buds
chewing facilitates
swallowing
chewing creates a greater
surface area on which salivary enzymes can act.
To stimulate the taste buds – this reflex increases:
salivary,
gastric,
pancreatic,
bile secretion to prepare for the arrival of food.
act of chewing is voluntary, but most chewing during a meal is…
…a rhythmic reflex
Act of chewing is voluntary, but most chewing during a meal is rhythmic reflex
Activation of the …
… skeletal muscle of the jaws, cheeks, lips, and tongue in response to the pressure of food against oral tissues.
There are 4 types of lingual papillae on the tongue
3 involved in taste
1) foliate papilla
2) filiform papilla
3) Circumvallate (vallate) papilla
4) Fungiform papilla
what do Foliate papilla have?
Vertical folds on edges
Filiform papilla details?
Most numerous/small brush like
Not involved in tasting
how many Circumvallate (vallate) papilla ?
Usually, 8-12 in total
Circumvallate (vallate) papilla size?
Large (1-2 mm) – covered in stratified squamous epithelium
Fungiform papilla is scattered trhough the …
filiform papillae
Chemorecepters for taste are packaged int…
… taste buds
how many taste buds
10,000
the majority of taste buds are on the…
… upper surface of the tongue
tasdte buds contain
around 50 long taste receptors
taste buds are arranged like
orange segments
taste buds each have a small
opening
the small opening in taste buds is the
taste pore
taste buds are also known as
modified epithelial scells
tatse buds are activared by
a taste-provoking chemical (tastant)
Afferent (sensory) fibres take i
impulses via brain stem to thalamus to cortical gustatory area
what are taste receptor cells?
Modified epithelial cells with many surface folds (microvilli) that protrude slightly from the taste pore.
Plasma membrane contains
receptors that bind selectively with chemicals in a solution – a tastant.
a tastant causes…
… ion-channels to open (depolarisation) leading to entry of Ca2+ and neurotransmitter release.
Signals are conveyed to
cortical gustatory area and the brain stem projects fibres to the hypothalamus and limbic system to add affective dimensions (pleasant/unpleasant taste).
The thousands of different taste sensations we can discriminate all come from…
… varying combinations of the five primary tastes:
Receptor cells use different
pathways to bring about a receptor potential in response to each taste category.
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saliva produced by…
three major pairs of salivary glands
Exocrine glands - Acini secretory cells that
lie outside of the oral cavity
Discharge via
short ducts into the mouth
what is saliva made up of?
Made up of 99.5% H2O and 0.5% electrolytes (salts) and protein.
Salivary NaCl concentration is…
…one seventh that of blood plasma – important in perceiving salty tastes.
Similarly, glucose is absent from
saliva
Similarly, glucose is absent from saliva – important in
perceiving sweet tastes
important salivary proteins are…
- amylase
- mucus
- lysozyme
- salivary kallikrein (no important role in food digestiion)
saliva begins…
digestion of carbohydrates and lipids
salica begins digestion of carbohydrates and lipids using whch enzymes?
salivary amylase
lingual lipase
salivary amylase function
breaks polysaccharides into maltose (disaccharide)
lingual lipase function
breaks down triglycerides into diglycerides and free fatty acids
salica facillitates…
…. swallowing
saliva facilitates swallowing by
moistening food, lubrication provided by mucus secretion
saliva also has
antibacterial activity
enzymes involved in saliva antibacterial activity
lysozyme
globulin A
lactoferrin
rinsing
lysozyme function
enzyme that destroys bacteria by breaking down their cell walls.
globulin A function
a glycoprotein that binds IgA antibodies.
lactoferrin function
a protein that tightly binds the iron needed by bacteria to multiply.
rinsing away function
Rinsing away material that may serve as a food source for bacteria
saliva is a solvent for…
Rinsing away material that may serve as a food source for bacteria
- Only molecules in solution can react with taste bud receptors
saliva aids
speech by facilitating movement of lips and tongue
what type of hygeine does saliva help with?
oral hygeine
describe oral hygeine by saliva?
- Help keeps the mouth and teeth clean.
- Consistent flow helps flush away food residues, foreign particles and old epithelial cells shed from oral mucosa.
saliva is rich in…
bicarbonate buffers (HCO3-):
saliva is rich
