Session 3 - Anatomy Of The Gastrointestinal System Flashcards
What are the four layers of the gut wall?
Mucosa (innermost)
Submucosa
External muscle layers
Serosa (outermost)
What layers make up the mucosa of the gut wall?
Epithelial layer
Lamina propria
Muscularis mucosae
What does the lamina propria contain?
Lots of lymphoid nodules and macrophages. Produce antibodies to protect against bacterial/viral invasion.
What does the submucosa of the gut wall contain?
Dense connective tissue, blood vessels, glands, lymphoid tissue, submucosal plexus (Meissner’s)
What is a enterocyte?
A simple columnar cell that absorbs. Predominant cell of small and large intestines. Has microvilli.
What do goblet cells secrete?
Mucus
Is there a greater number of goblet cells in the duodenum or colon?
Colon. Increasing number as you move from the duodenum to the colon.
What does mucus protect epithelium from?
Friction (mucus acts as a lubricant) Chemical damage (acidic environment) Bacterial inflammation (forms physical barrier)
What do gastric surface mucous cells (foveolar cells) secrete?
Mucus/HCO3 that forms barrier to stomach acid
What is the difference between plicae circulares and rugae?
Plicae circulares are permanent folds found in the small intestine. Rugae are temporary folds found in the stomach (allow stomach to expand easily).
What specialised cells are found in the crypts of lieberkuhn and what are their functions?
Stem cells -constantly divide to replace epithelia
Paneth cells - secrete antibacterial proteins to protect stem cells
Enteroendocrine cells - secrete hormones that control the function of the gut
Where are crypts of lieberkuhn found?
Small and large intestine
Where are Brunners glands found?
Duodenum
Give examples of exocrine tissues in the gut.
Salivary glands
Pancreas
Brunners glands
What causes ulceration of the GI tract?
Erosion through the muscularis mucosae due to failure of protective mechanisms. E.g. loss of mucus production
What is coeliac disease?
An abnormal immune response to gliadin (protein found in gluten). Mucosa of intestine becomes inflamed and damaged, villi can’t absorb. Results in malabsorption and diarrhoea.
The term inflammatory bowel disease is mainly used to describe what two conditions?
Ulcerative colitis
Crohn’s disease
What are the layers of the abdominal wall?
Skin Fascia (+ fat) - superficial - deep 4 muscles (3 anterolateral muscles) - external oblique - internal oblique - transverse abdominis - rectus abdominis Transversalis fascia Peritoneum
Which abdominal muscles have an aponeurosis?
External oblique
Internal oblique
Transverse abdominins
These lateral muscles have aponeuroses that envelope the midline rectus abdominus muscles.
What is the rectus sheath?
The aponeurosis of the lateral abdominal muscles surrounding the rectus abdominins
What is the arcuate line?
Horizontal line that marks the lower limit of the posterior layer of the rectus sheath. It is also where the inferior epigastric vessels perforate the rectus abdominis.
Found roughly half way between the umbilicus and pubic crest.
What is a mesentery?
A double fold of peritoneum that attaches certain viscera to the posterior abdominal wall.
Which viscera are attached to the posterior abdominal wall by mesenteries?
Jejunum Ileum Appendix Transverse colon Sigmoid colon Rectum
What do mesenteries contain?
Blood vessels
Lymph vessels
Nerves
Fat
What is a peritoneal ligament? Give examples.
A double fold of peritoneum that connects two viscera together.
E.g.
Gastrocolic ligament - stomach to transverse colon
Gastrosplenic ligament - stomach to spleen
OR
A double fold of peritoneum that connects a viscera to the abdominal wall.
E.g.
Falciform ligament - liver to anterior abdominal wall
Triangular ligaments - liver to diaphragm
What is the falciform ligament?
Double fold of peritoneum connecting the liver to the anterior abdominal wall.
What are the greater and lesser omenta?
Double folds of peritoneum:
Greater omentum - hangs down off the greater curve of the stomach
Lesser omentum - connects lesser curve of the stomach to the liver
What is the purpose of sphincters in the GI tract?
Divide gut into sections
Control movement along the gut
Prevent reflux of material
Name all the sphincters of the GI tract in order.
Upper oesophageal Lower oesophageal Pyloric Sphincter of Oddi Ileo-caecal valve Internal anal External anal
Is the external anal sphincter under somatic or autonomic control?
Somatic (voluntary)
Which branches of the aorta supply the foregut, midgut and hindgut respectively?
Coeliac trunk - supplies foregut
Superior mesenteric artery - supplies midgut
Inferior mesenteric artery - supplies hindgut
Which viscera make up the foregut?
Lower oesophagus Stomach Spleen Liver Gallbladder Pancreas Proximal duodenum
Which viscera make up the midgut?
Distal duodenum Jejunum Ileum Appendix Ascending colon Caecum Proximal 2/3 of transverse colon
Which viscera make up the hindgut?
Distal 1/3 of the transverse colon Descending colon Sigmoid colon Rectum Upper anal canal
All venous drainage from the intestines and stomach will drain to what organ via what vein?
Liver via the hepatic portal vein
What is pyloric stenosis?
Hypertrophy of the pyloric sphincter. Causes gastric obstruction which can lead to projectile vomiting.
What is a volvulus?
A volvulus is when a loop of intestine twists around itself and the mesentery that supports it, resulting in a bowel obstruction. Symptoms include abdominal pain, abdominal bloating, vomiting, constipation, and bloody stool.
Why is a section of bowel involved in a volovulus at risk of ischaemia?
Mesentery contains blood vessels supplying the viscera, twisting of the mesentery can cut off these blood vessels leading to ischaemia.
Explain why liver cirrhosis leads to ascites.
Liver cirrhosis leads to narrowing of blood vessels in the liver, this increases hydrostatic pressure in the hepatic portal vein. Increased hydrostatic pressure means that more fluid moves out of blood vessels into the interstitium and peritoneal cavity.
Also, reduced liver function means less albumin is produced so there is a lower oncotic pressure in blood so more fluid moves out of the blood.
What is ascites?
The accumulation of fluid in the abdomen/peritoneal cavity. Most commonly caused by portal hypertension due to liver cirrhosis.
