Module 9 Flashcards
Name the four main layers or tunics of the gut wall:
1) mucosa 2) submucosa 3) muscularis externa 4) serosa or adventitia
Name the individual components that comprise innermost Layer A:
Epithelium lamina propria muscularis mucosa
In the basic plan of the gut, muscularis externa has two components. Identify them:
Inner circular layer Outer longitudinal layer
Where in the digestive tract is muscularis externa composed of skeletal muscle i.e. under somatic control?
Pharynx, upper third of oesophagus, external anal sphincter
Where in the digestive tract does muscularis externa have an extra component? In which organ is it located and why is it required?
Stomach – for mixing and churning
For each of the following peritoneal folds state the specific organs that they are connected to or support. 1) greater omentum 2) lesser omentum 3) falciform ligmament 4) mesentery 5) mesocolon
1) Connects transverse colon and greater curvature of stomach 2)Connects stomach and duodenum to liver 3)Connects liver to anterior abdominal wall 4)Connects small intestine to posterior abdominal wall 5)Connects large intestine to posterior abdominal wall
What does retroperitoneal mean?
What does retroperitoneal mean?
What is peritonitis?
Inflammation of the peritoneum
What type of epithelium is found on the surface of the tongue? Why?
stratified squamous, keratinised in parts (on the filiform papillae) permits wear & tear
The tongue is a muscular structure; explain the difference between intrinsic and extrinsic muscles of the tongue?
Intrinsic lie entirely within tongue, extrinsic have attachments to bones of skull
The palate forms the roof of the oral cavity, identify the parts of the palate labelled:
Hard palate, Soft palate, Uvula
What is the function of structure 8?
Closes off nasopharynx during swallowing
The salivary glands contain serous secretory cells, mucous secretory cells or a combination of both. What is the difference in the composition of the secretions produced by these cells?
Serous: water and amylase Mucus: mucin, water
How may pairs of salivary glands are there?
Three
What type of muscle (skeletal, smooth or cardiac) is found in the posterior walls of the pharynx? Why is this?
Skeletal, for voluntary control of food bolus
What role does the epiglottis play in swallowing? What type of tissue is made from?
Prevents food entering the larynx; elastic cartilage
Does the oesophagus lie anterior or posterior to the trachea?
Posterior
Which muscular structure must the oesophagus pass through to enter the abdominal cavity?
diaphragm
What is the hole or opening in this muscle called?
oesophageal hiatus
What type of epithelium lines the oesophagus and what is its function?
Non-keratinised stratified squamous – allows wear and tear
There are numerous glands in the submucosa - they may not be visible. What are their secretions made of and what purpose do they serve?
Mucus, for lubricating passage of food
Can you think of a reason for this?
Upper 2/3s has skeletal muscle for voluntary control
The outermost layer of the thoracic oesophagus consists of connective tissue that anchors it to surrounding structures (there is no serous membrane present). What is this layer called?
adventitia
What role do the sphincters play?
Isolate acidic stomach environment from oesophagus and duodenum, regulate flow
Are rugae permanent structures?
No ; permit the stomach to distend
Name the two folds of peritoneum that are attached to the stomach:
To liver: lesser omentum greater omentum
What type of epithelium is found here (stomach)?
Simple columnar
Entero-endocrine cells (G cells) are also found in the glands but their secretions pass through the lamina propria into the blood, rather than going into the lumen of the stomach. What products do these cells secrete?
Gastrin
What role do the secretions from G cells play in the digestive process?
Stimulates gastric activity
Name the three layers of muscle that are found in the muscularis externa of the stomach.
Oblique, circular, longitudinal
What purpose does the extra layer serve in the stomach?
Mixing and churning
What MACROSCOPIC (visible to the naked eye) structures, found within the wall of the small intestine, increase its surface area?
Plicae circulares
What other function do these structures perform?
Help to spiral chyme along length of intestine
There are two more features of the epithelium that help to increase surface area, name them
Villi and microvilli
One of these gives the internal surface of the small intestine a velvety appearance. Which one?
Villi (0.5-1.5mm, just visible to naked eye)
Which structure/serous membrane attaches the small intestine to the posterior abdominal wall? (Hint: check your Prelab)
Mesentery
What type of epithelium is found in the duodenum?
Simple columnar
Are goblet cells present?
yes
The intestinal glands (crypts of Lieberkuhn) secrete intestinal juice; what does it contain?
Serous fluid + enzymes from the intestinal mucosal cells
Identify the duodenal (Brunner’s) glands in the submucosa. What is the function of these glands?
Secrete alkaline mucus to neutralise gastric acid in chyme
Why are these glands not found in the jejunum and ileum?
No longer an acidic environment
What types of gut motility are found in the small intestine?
Peristalsis and segmentation
What is the gastro-ileal reflex?
Food/activity in the stomach encourages material in the ileum to move on to the large intestine.
Three distinctive external, macroscopic features (identified above) are associated with the large intestine. Name these features
taenia coli, haustra, epiploic appendages
Name three main functions of the large intestine.
Absorption of remaining water and electrolytes, bacterial production of vitamins, formation and elimination of faeces
Regarding water absorption, does the small intestine or the large intestine absorb the greatest volume?
Small
Numerous bacteria are found within the large intestine. Identify 4 functions;
Breakdown amino acids, decompose bilirubin, produce vitamins B and K, indigestible CHOs (fibre, cellulose, resistant starch)
Refer to the Pre-lab (Figure 9.1) and identify which structure/serous membrane attaches the large intestine to the posterior abdominal wall:
Mesocolon
What type of epithelium is found in the large intestine?
Simple columnar
Are goblet cells present? What is their role in the colon?
Yes ,to ease the passage of faeces
How does the muscularis externa differ from the general histological plan?
Longitudinal layer reduced to three bands of muscle – taeniae coli
Explain the puckered (existence of haustral pouches) appearance of the colon.
Contractions of the taeniae coli
What types of motility do you find in the large intestine? Include reflexes in your answer
Mass movements (gastrocolic & duodenocolic reflexes); haustral churning; defaecation reflex.
What are the four lobes of the liver?
right, left, caudate, quadrate
Which lobe is the largest?
Right
Identify the two ligaments on the liver
ligamentum teres, falciform ligament
falciform ligament anchors the liver to which structure?
Anterior abdominal wall
What is the function of the gallbladder?
Store and concentrate bile
The liver receives blood from two sources. Name the two blood vessels that bring blood into the liver at the “porta hepatis”
Hepatic artery and hepatic portal vein;
What is the difference in the composition of the blood from these two sources?
Artery rich in oxygen, vein rich in nutrients
Blood leaves the liver through which blood vessel?
Hepatic vein
What are pancreatic digestive enzymes produced by the exocrine secretory units called?
Pancreatic acini
Are pancreatic acini and islets of langerhans exocrine or endocrine?
Acini- exo islets- endo
Which three vessels are known as the portal triad?
Hepatic artery Hepatic portal vein Bile duct
How would you distinguish between these vessels?
Shape of the cells in the wall: cuboidal for the duct, squamous for blood vessels and shape of lumen (round for artery, flattened for vein)
In which direction does blood flow through the sinusoids between the hepatocytes?
From portal triad to the central vein flowing past the hepatocytes
Through which structure do these two ducts enter the duodenum?
Duodenal papilla
Name the sphincter that controls this opening?
Hepatopancreatic sphincter or (sphincter of Oddi)
Small calculi known as gallstones, ranging from 6mm up to 5cm may form within the gallbladder; they usually contain cholesterol, calcium carbonate, bilirubin or other bile pigments. Name some other ducts or locations where you might expect gallstones to form.
Cystic duct, common bile duct, R & L hepatic ducts, common hepatic duct, HP ampulla, liver
What characteristic of these ducts might make them susceptible to gallstone lodgement.
quite narrow; usual internal diameter of cystic duct is 2-3mm & common bile duct is 3-8mm
A person with gallstones often experiences excruciating pain in the epigastric and right hypochondriac regions? Give an explanation for this.
location of gallbladder in these regions
Confirmation of a doctor’s diagnosis of gallstones is made using an ERCP (Endoscopic Retrograde Cholangio-pancreatography). Which structures might such a tube pass through in an ERCP on its way to these ducts?
mouth, pharynx, oesophagus, stomach, duodenum; major duodenal papilla, sphincter of Oddi
Current medical thinking is to remove the gallbladder; this is known as a cholecystectomy. How do you think people might cope without a gallbladder? Does bile still enter the duodenum?
The bile forms a continuous stream between liver and duodenal papilla, but not so concentrated
