Lecture 2 Flashcards
What are the accessory organs to the GI tract?
Pancreas, gall bladder and liver
What are the 6 types of epithelium?
Simple squamous, columnar and cuboidal, stratified squamous, columnar and cuboidal. Pseudostraitifed also
What are the 2 main epithelia of the GI tract?
Stratified squamous and simple columnar
Which type of epithelia is present in the oral cavity, oesophagus and lower third of the anus? What is the function?
Stratified squamous. Protection from motility.
Which type of epithelia is present in the stomach, small and large intestine? What is the function?
Simple columnar. Absorption and secretion.
What are the three layers of the mucosa?
Epithelium, lamina propria and muscularis mucosa
What other types of cells are present within the epithelium layer?
Goblet cells and endocrine cells. These secrete mucus and hormones.
What are the features of the lamina propria?
The scaffold on which the epithelium is built upon. Has blood vessel endings for supplying oxygen and removing absorbed nutrients. Lymphatic system for removing absorbed fat. Packed with lymphocytes as the GI tracts first immunological defence.
What is the muscularis mucosa?
A thin layer of smooth muscle cells that provide local control of villi.
Which layer is below the mucosa?
The submucosa
What is the submucosa?
dense connective tissue that contains the submucosal plexus.
What does the submucosal plexus control?
Secretions.
What are the two layers of the muscularis externa?
Longitudinal and circular smooth muscle layers.
What do the muscularis externa do?
Control peristaltic movements.
What sits between the longitudinal and circular muscle layers?
The myenteric plexus.
What is the most external layer of the GI tract called?
The serosa/adventitia.
What does the adventitia contain?
Blood vessels, lymphatics, enzyme and fluid rich secretions.
What is the functional unit of the salivary gland?
The acinus.
What is the primary secretion of the salivary gland?
Isotonic solution of fluid and electrolytes into the acinus.
What occurs in the ducts of the salivary glands?
NaCl absorption and HCO3- secretion.
Is saliva NaCl or HCO3- rich?
Saliva is a bicarbonate rich secretion.
What glands does the parasympathetic nervous system stimulate?
Parotid- need for serous saliva.
What does the sympathetic nervous system do to salivary glands?
Inhibits stimulation of the parotids, and some stimulation of the sublingual for mucus saliva.
At what point does the oesophagus pass through the diagragm?
The lower oesophageal sphincter.
Which parts of the oesophagus is skeletal and smooth muscle?
Top 1/3 is skeletal, rest is smooth
What nerve innervates the oesophagus?
The vagus nerve
What are the different sections of the stomach top to bottom?
The fundus, body/corpus, antrum.
Parietal cells from which part of the stomach secrete HCl?
The body
Are goblet cells in the stomach?
No, the mucus secreting cells are mucus neck cells.
What factors protect the stomach from acid?
Mucus, bicarbonate, tight junctions between columnar epithelium.
What are the three parts of the small intestine?
Duodenum, jejunum, ileum
What separates the stomach from the duodenum?
The pyloric sphincter.
Where is the duodenojejunal junction?
To the left of the L2 vertebrae.
Where is the junction between the jejunum and ileum?
This is anatomically indistinct.
What anchors the jejunum and ileum to the posterior body wall?
The mesentery
Which parts of the SI are the main absorption sites?
The jejunum and ileum.
What are the folds of the small intestine called?
Plicae circulares.
What is the functional unit of absorption?
The villus.
The specialised cells of the villus arise from undifferentiated cells from the base of the ….
crypts
What are the 4 types of specialised cells in the small intestine villus?
Absorptive cells, Goblet cells, Granular cells, APUD cells
What do absorptive cells do?
Absorb nutrients. They are also called enterocytes.
What do goblet cells do?
Secrete mucus which lubricates the epithelium to protect against damage.
What do granular cells do?
Secrete enzymes to protect against bacteria
What do APUD cells do?
produce endocrine secretions
The capillaries that are present within each villi drain into what?
The portal vein.
What two veins join to form the portal vein?
The superior and inferior mesenteric veins.
Where does the portal vein go to?
The liver
What is a blind ended lymph vessel and what does it transport?
A lacteal- it transports absorbed fats
Where does the liver sit?
The right upper quadrant of the abdomen
Which lobe of the liver is bigger?
The right lobe
What occurs in the liver?
Filtering and detoxification of absorbed materials. Synthesis of proteins, glycogen storage and bile production.
What is the functional unit of the liver?
The lobule
Where is bile stored?
Gall bladder
What artery brings oxygenated blood to the periphery of the lobule?
The hepatic artery (this originates from the abdominal aorta)
What also enters the lobule at the periphery?
The portal vein.
How are hepatocytes arranged?
In a 3D lattice
What are the capillaries called that run between the layers of hepatocytes?
Sinusoids.
What removes substances excreted by hepatocytes?
Canaliculi which drains into bile ducts.
What 2 ducts join to make the common hepatic duct?
The left and right hepatic ducts.
What joins the common hepatic duct to form the common bile duct?
The cystic duct from the gall bladder.
What stimulates the gall bladder to secrete bile?
The presence of food in the duodenum
At what point does the common bile duct enter the duodenum?
The sphincter of Oddi
Where does the pancreas lie?
Horizontally across the posterior abdominal wall.
What are the two main components of pancreatic juice?
Digestive enzymes and bicarbonate rich fluid
Where does the pancreatic duct join the common bile duct?
Ampulla of Vater
What is the main function of the large intestine?
Water and ion absorption
What is the first section of the large intestine?
The caecum
Where is the caecum?
The right lower quadrant.
What is located at the left colic flexure?
The spleen
Do the epithelia of the large intestine have villi?
No
Does the small or large intestine have more goblet cells?
The large intestine has more goblet cells
How does the longitudinal muscle layer in the large intestine differ?
It is not continuous, it is separated into 3 bands called the taeniae coli.
At what level does the rectum begin?
S3 vertebrae
