Lecture 29 Flashcards
Parts of the tongue (anatomy)
Epiglottis
- back of tongue
- cartilage
Lingual tonsil region
- under epiglottis region
- involved in immune defense
- ridges of surface indentations where a lot of diffuse lymphatic tissue is located
Palatine tonsil
- ring-like structure around pharynx
- needed to detect invading antigens and invading things
Circumvallate papillae
- largest, at back on tongue
- 12 elevated structures in V-shaped arrangement
Foliate papillae
- at edges
- are ridges or grooves
Fungiform papillae
- all over tongue surface, smaller protrusions - mushroom shape
Filiform papillae
- everywhere, specifically at near the tip
- are tiny protrusions
- hard to see with naked eye
Median sulcus
- depression at centre of tongue
Lingual papillae
- general term for all protrusions on tongue
Tongue epithelium
Surface epithelium is stratified squamous epithelium.
- under tongue is non keratinized
- on tongue surface is keratinized
What kind of tissue does the tongue contain?
Right under the tongue’s surface epithelium, the body of tongue is mostly connective tissue
Lots of skeletal muscle and adipose tissue. Lots of fibers and glands too.
Skeletal muscle is under the CT. Skeletal muscle runs in various diff orientations: longitudinal muscle fibres and oblique muscle fibers
Filiform Papillae
•smallest
•Conical, highly keratinized
- sharpened pencil shape, sometimes the tip can be divided, the tip is highly keratinized
•Mechanical grip
- to lick material off the surface (i.e. in cat that has tons of these, raspy
•No taste buds
Fungiform Papillae
•Mushroom shaped
- dome-shaped protrusion
•Dorsal taste buds
- some taste buds at dorsal surface, function is to sense taste
Foliate papillae
•Parallel ridges or grooves
•Lateral edge towards back of tongue
•Many lateral taste buds
•a bit larger than fungiform papillae
•some epithelium have lighter regions, which are lateral taste buds that point towards the
groove side by side.
•Most specialized to detect bitter tastes.
Circumvallate papillae
• 8-12 in humans
• Large, dome-shaped
- largest papillae making V-shaped arrangement at back of tongue
• Surrounded by moat-like invagination
- indentation is constantly lubricated or filled with a secretion from lingual salivary glands located right underneath the indentations. These are serous glands that make watery protein-rich secretions. They are called Von Ebner’s Glands (Lingual salivary Gland) and empty their contents into those indentations.
• Numerous lateral taste buds
- the stratified squamous non keratinized epithelium in the indentation are filled with circular, lighter structures, which are taste buds, and face the moat
Taste bud
Looks like onion with several layers, but made up of diff cells
Order of taste bud sections:
- taste pore
- opening to the surface
- sometimes can see taste pore, but sometimes cannot see it - sensory receptor cell and supporting cell
- forms microvilli that extend into taste pores
- supporting cells give metabolic and structural support to the receptor cell
- supporting cells also tend to give rise to receptor cells, so they are pre cursor of receptor cells - basal stem cell
- sit at base of the taste bud
- makes the cells
- they first differentiate to supporting cell, then to sensory receptor cell - afferent nerve terminals
- Afferent nerve connects to taste receptor cells in the taste bud
- makes synapses with sensory taste receptor cells
Taste bud activation
- A tastant binds to a taste receptor molecule
- apical part of receptor cell has microvilli, that increase SA and contain taste receptor molecules in their plasma membrane
- taste receptor molecule is a g-protein associated receptor that binds to a food molecule
- after bound to food, the taste receptor molecule changes conformation. Then the 3-part G complex dissociates from receptor molecule and the alpha subunit binds GTP - G-complex is activated and binds GTP
- The GTP-bound alpha-subunit opens and closes ion channels resulting in depolarization
- alpha subunit associates with sodium
and calcium channels that open so the ions enter the cell, resulting in depolarization of the plasma membrane
- causes change in membrane potential - Calcium triggers the release of neurotransmitters from the taste cell at synapse
- membrane potential travels to basal end of cell
- there is change in polarization of PM, resulting in release of nt from the cell, which can bind to synapse at afferent nerve terminal and trigger depolarization
- the signal is then propagated
Taste qualities and natural stimuli detected by taste receptors - general
Each taste quality has its own type of receptors. We perceive many flavours due to combo and binding affinity of diff
molecules to diff receptors
Taste qualities:
- fat
- umami
- salty
- bitter
- sweet
- sour
Sweet and umami have similar receptors
Fat - taste receptors
GPR120
GPR40
CD36
K ch
Umami - taste receptors
T1R1
T1R3
mGluRs
Salty - taste receptors
ENaC
Others
Bitter - taste receptors
T2Rs
Sweet - taste receptors
T1R1
T1R3
Others
Sour - taste receptors
Intracellular acidification
The 3 diff salivary glands
Parotid gland
Sublingual gland
Submandibular gland
Parotid gland
- large
- named b/c part otid (next to ear)
- childhood disease called mumps, where parotid gland is infected and gets large, but there are vaccinations for this now
- parotid gland has duct that opens up at roof of mouth
- only has serous acinus
- Long intercalated ducts
- Viral infection: Mumps
H and E:
- striated ducts are a little bigger than the acini
- striated duct has cuboidal or low columnar ep
- intercalated duct has cuboidal epithelium and large lumen, and are smaller than acini
Sublingual gland
- right under the tongue and opens up several ducts at the bottom of the duct
- if you want to make lots of saliva, press
tongue to bottom of tongue, can fill up oral cavity with saliva - this is used by people doing spitting contest: forming of lots of saliva from sublingual gland is called gleeking
- mostly mucous acinus
H and E:
- mixed, mostly mucous acinus
- short ducts
- some serous demilunes
- lumen is tiny
- nuclei hug basement membrane
Submandibular gland
- under our mandible
- as we chew and masticate food, the saliva is released towards the bottom surface underneath the tongue through this 1 gland
- mixed acinus (both mucous and serous acini) with serous demilune (half moon-
shaped arrangement of cells sitting on top of the mucous-secreting cells)
H and E:
- mixed, largely serous
- prominent striated ducts
- serous demilunes
- often there is serous demilune on top of the mucous secretory units
Saliva - Major components
Water
Lysozyme: digestive enzyme
- breaks down walls of bacteria
- controls bacterial growth
Amylase: digestive enzyme
- digests starch
- breaks down food
IgA: immunoglobulin
- made by plasma cells
- controls bacterial growth
Calcium/potassium
- for tooth mineralization
- provides teeth with minerals via saliva
Bicarbonate
- important for enzymes to function
- buffers the oral cavity for the correct pH for enzyme activity
Lipase: digestive enzyme
- digests fat
- breakdown of food
Lactoferrin: iron chelator
- compound that chelates iron
- bacteria often needs iron for growth, so if you remove iron, you control bacterial growth
Proteins
- protective proteins produce protective film on teeth, which protects from acidity
Saliva - major functions
Buffering of oral cavity
Breakdown of food
Control of bacterial growth
Moistening of food
Tooth mineralization
Protective film on teeth
How much saliva is produced per day?
1200 mL
Saliva secretion
Salivary gland acinus connected to intercalated duct connected to striated duct
Salivary gland acinus
- salivary glands are compound tubulo-acinar glands
- made up of cells that take material out of
capillaries (there are lots of capillaries surrounding the acini)
- Secretion of mucins, proteins, enzymes (acini needs to be activated via nerve endings to stimulate production of these components)
- Transport of sodium, chloride, water transported into lumen
- IgA is made my plasma cells in connective tissue surrounding the acini and transported across the epithelium into lumen to become part of saliva
Components listed above then travel through duct system. Then the duct gets bigger and the epithelial cells making up the duct modify the saliva
Striated duct
- Production of Bicarbonate
- Reabsorption of sodium, chloride
- Actively resorbs electrolytes
Types of glands (shapes)
Simple tubular
- intestinal glands of Lieberkuhn
Simple coiled tubular
- Sweat glands
Simple branched tubular
- gastric, uterine glands
Simple acinar
- sebaceous gland
Compound tubulo-acinar/ Compound tubular
- Salivary glands, prostate gland
- gastric cardia, pyloric gland
Compound acinar
- exocrine pancreas
Lobe
Glands are divided up into larger substructures called lobes, and into lobules. A lobe consists of many lobules. Lobules are surrounded by CT
Each lobule contains an intralobular duct that branches into striated ducts to intercalated ducts to acinus. These 4 are part of lobule
But before the intralobular duct, there is lobar duct that branches into interlobular duct to intralobular duct
Entire pathway from big to small: Lobar duct to interlobular duct to intralobular duct to striated duct to intercalated duct to acinus
Types of secretions - general
Serous, mucous, mixed
Serous secretions
Proteinaceous secretions, watery consistency: Parotid Gland
Mucous secretions
Glycoproteinaceous secretions, complex polysaccharides called mucus, viscous, gel-like consistency: Sublingual Gland
Mixed secretions
Serous & mucous secretory cells: Submandibular Gland
Serous acinus
Nuclei are round and towards base of cell, secretory
products are towards lumen, lumen is in middle, acinus is pizza shape,
stains dark due to proteins and enzymes
Mucous acinus
Lightly stained, nuclei are flat and at location at base
of cell, flat due to thick mucus inside cell cytoplasm
Striated duct
simple cuboidal epithelium where nuclei are in centre and cytoplasm stains lighter than the serous secretory units
Large lumen.
Striated duct epithelial cells have prominent basal plasma membrane infoldings and parallel mitochondria seen as striations in LM. There are lines or striations in the basal cytoplasm. This increase in SA of basal PM allows lots of transport molecules to
be inserted to PM for transport. Important in transport. Energy for transport comes from mitochondria. The cells constantly transport material from lumen to capillaries
Intralobular ducts
Has cuboidal cells surrounding large lumen.
Lots of CT around the duct
Myoepithelial Cells
Secretory acini are surrounded by Stellate Myoepithelial Cells. They contract upon hormonal and nervous stimulation and move secretory products into the duct system.
Myoepithelial cells contain a lot of contractile elements
Excretory duct
Has stratified cuboidal ep
Is the Serous Demilune an artifact?
Preparation techniques affect the histological appearance of mixed acini
Yes, this is an artifact of fixation and dehydration
Standard formaldehyde fixation. If you fix the tissue and dehydrate it to prepare histological section, the serous cells will be pushed outward of the acinus and the
mucous secreting cells will remain close to the lumen. The dehydration pushes serous cells outward and appearance of serous
demilune is prominent as artifact
If you use Rapid Freezing Technique without chemicals, the mucous cells and serous cells sit side by side in the acinus.
