Salivary glands, oesophagus, and Stomach micro anatomy Flashcards
Parasympathetic and Gut activity?
Activates and enhances gut activity
Sympathetic and Gut activity?
inhibits gut activity
What are the layers of the GI tract?
1) Mucosa - epithelium, lamina propria and muscularis mucosae
2) Submucosa
3) Muscularis Externa
4) adventitia/Serosa
Purpose of epithelium?
Protection (multiple layers)
Secretion
Absorbtion
Purpose of lamina propria
Support
1) Mechanical Support - collagen
2) functional support - BV, nerves, lymphatics
Purpose of Muscularis Mucosae
Movement independent of peristalsis
Purpose of Submucosa?
Same as lamina propria
Why is the lamina Propria loosely arranged?
to allow for the expansion of a bolus
How is the muscularis externa arranged? What is the exception of this?
Inner circular and outer longitudinal
exception stomach
What type of muscle is the muscularis externa? What is the exception of this?
Smooth muscle (involuntary).
Exception: Upper 1/3 oesophagus
internal anal sphincterWhats the difference between adventitia and serosa?
Adventitia: outermost CT covering any organ, vessel or other structure.
Serosa (visceral peritoneum) slippery outer covering for the gut tube; two layered, with the outer mesothelium sitting on a bed of CT
Intra peritoneal
Organs totally suspended. These are covered in serosa (simple squamous mesothelium)
Retroperitoneal
lined with serosa on anterior surface only (‘outside peritoneal cavity’)
Posterior surface is adventitia
how much Serous Fluid do we produce daily?
7L
Submucosal plexus is also called?
Meissner’s plexus
Sphincters. What layer are they formed by
gate keepers that control the volume/timing/flow if substances from one region to another.
Thickening of the IC
Ascites
Caused by cirrhosis/liver damage, heart failure
- accumulation of fluid in the peritoneum, abdominal swelling, distortion of visceral organs
- can be drained
Peritonitis
-inflammation of the peritoneum > impaired function
What determines the composition of the secretions
The proportion of Serous acinar (dark) and mucus acinar (light) whether it is serous/watery or mucous/sticky
% of contribution and types of acini in the salivary glands
Parotid (~25%) - serous acini (dark cells) > watery
Submandibular (~70%) - mixed (dark and light) > serous + mucus
Sublingual (~5%) - mixed (dark and light) > serous + mucus
Draw and describe a serous acinus
- central, darkly staining nuclei
- Mitochondria perpindicular to the basal surface
- Zymogen granules in the apical cytoplasm (predominate AMYLASE)
- myoepithelial cells surround the base of acini
Myoepithelial cell
modified contractile epithelia. Squeeze acital secretion into lumen.
-in BOTH serous and mucus acinus
Draw and describe a mucus acinus
- flattened, peripheral nucleus
- mucus granules in the apical cytoplasm (flatten nuclei)
- myoepithelial cells around base of acinus
Striated ducts are… How are they striated and whats this for?
Intralobular ducts.
- aligned mitochondria in the basal infoldings of the cell give striated appearance
- this is because they have increased METABOLIC ACTIVITY and ACTIVE TRANSPORT
Function is to exchange Na+ and Cl- for K+ and HCO3-
Composition of saliva
99% water
1% ions, buffers, enzymes etc
Lubrication function of saliva
Carb-rich glycoproteins (mucins): slippery molecules of mucus
also has a protective function as they prevent bacterial adhesions (hard to attach)
Protection Function of the saliva
PREVENT:
- Bacterial adhesions & secretions (usually acidic)
- vomit (acidic)
-Bicarbonate ions (counteract acid (gastric to an extent))
- Lysozyme (breakdown bacteria cell walls)
- Lactoferrin (fight iron dependent bacteria)
- Immunoglobulin A (fight genetic infection/virus)
Why do we get a huge saliva influx before vomiting?
Protective reflux reaction to ensure the alkaline saliva buffers the acidic vomit
Digestion Function of Saliva
AMYLASE: (pH 4-11), starts sugar/carb BD into monomers. (as sugars are good site of bacterial growth this decreases potential growing sites!)
LIPASE (pH 4): breakdown fats, more active in stomach as pH lower
Kallikrein: protease, cleaves another proenzyme > increased blood flow and bloody supply to sustain demand for metabolism whilst eating
PSNS
accelerates secretion > lots of watery saliva
myoepithelial cells contract
-increased blood flow
SNS
small amount of viscous saliva containing high enzyme concs
-less volume = dry mouth feeling
BVs constricted
Why do meth users have such bad teeth
destroy salivary gland > destroy protective function!
Function of Oesophagus
rapid transport (PS) of the food bolus. straight ~25cm tube, thick muscular wall, protective lining. Collapsed outline with folds of submucosa when empty (loosely packed)
Epithelium of oesophagus
thick sacrificial stratified squamous epithelium (6-8 layers). non-keritinised
as it approaches stomach»_space; cuboidal/columnar
Muscularis mucosae of oesophagus
absent/rare upper but developed near stomach, not defined, discontinuous in places.
Allows for mucosa movement independent of peristalsis
Are glands present in the oesophagus
yes
Muscularis externa
2 coats, not always circular and longitudinal, irregular areas.
upper 1/3: skeletal (striated)
middle 1/3: skeletal & smooth
lower 1/3: smooth (poorly preserved)
Covering of oesophagus
adventitia (except 1-2cm)
Chronic Oesophagitis
Often caused by GORD > inflammation
- stratified squamous only protective of mechanical abrasion
- chronic exposure can cause Barretts syndrome (precursor to oesophageal cancer)
In the body/Fundus
Parietal Glands
- HCl
- Intrinsic factor
- pepsinogen
- somatostatin
Rugae are
transient folds that come and go (less when full)
Four anatomical regions
cardia: mucus (bufferzone)
fundus
body: parietal glands
pylorus: mucus (bufferzone
Pyloric Glands
- Mucus**
- pepsinogen
- gastrin
- somatostatin
Muscularis externa layers of the stomach
Inner oblique
middle circular
outer longitudinal
