Lecture 22 Flashcards
What gets delivered into the SI?
Acidic chyme
What protects the SI from the acidic chyme?
Epithelium with goblet cells on surface, mucus-secreting glands in submucosa and neutralising pH (bicarbonate) from pancreas
What does the liver secrete for digestion?
Bile
What does the pancreas secrete for digestion?
Enzymes
What are the three regions of the small intestine?
Duodenum, jejunum, ileum
What is the shortest region of the SI?
Duodenum, ~25cm
What are the respective lengths of the jejunum and ileum?
~2.5m and ~3.5m
What is the total length of the SI?
~6m
What is the function of the duodenum?
To receive chyme from the stomach, enzymes & bicarbonate from the pancreas and bile from the liver
What is the function of the jejunum and ileum?
Digestion and absorption
What section of the SI lies retroperitoneal
Duodenum
What holds the jejunum and ileum in place?
The mesentery
What is the function of the mesentery?
To allow movement but prevent tangling
What does the mesentery contain?
Blood vessels, nerves, lymphatics and fat
What is the mesentery made up of?
Peritoneum which makes it slippery
What enters the mesenteric veins?
Nutrient-rich, deoxygenated blood
Where do the mesenteric veins drain?
To the hepatic portal vein
Where do the lymph lacteals of the mesentery drain?
Into the cisterna chyil -> thoracic duct -> left subclavian vein
What is a requirement of the SI in order to fully carry out digestion and absorption?
A very large surface area
How is a large surface area achieved in the SI?
Length, plicae circulares, villi, microvilli
What are plicae circulares?
Permanent large folds of the SI wall, a core of submucosa with overlying mucosa
How many muscularis layers does the SI contain?
2; inner circular and outer longitudinal
What are villi?
Part of the mucosa, found on the surface of the plicae circulares
What are villi made of?
A core of lamina propria that contains lymph lacteals for products fat digestion and a capillary network for products of protein and carbohydrate digestion
What allows villi movement?
Muscularis mucosae
What are microvilli?
Extensions off the simple columnar epithelial cells of the enterocytes on their apical surface
What does the microvilli form?
A brush boarder
What is the function of the microvilli brush boarder?
Contact digestion involving enzymes
What does the plasma membrane contain?
Proteins; channels and transporters for its semipermeable membrane
What do the tight junctions between the epithelial cells allow?
Allow small molecules to diffuse through
What are the five types of SI cells?
Enterocytes, goblet cells, paneth cells, endocrine cells, stem cells
What are the enterocytes?
Absorptive cells
What is the function of the goblet cells?
Secrete mucous for protection and lubrication
What are the paneth cells?
Granule containing cells with antibacterial enzymes
What is the function of the endocrine cells?
To secrete hormones
What is the function of the stem cells?
To make all cell types in order to replenish cells in tract
What is an intestinal crypt?
Part of the mucosa which projects downwards like a gland. Keeps cells safe and decreases damage
What is the function of the intestinal crypt?
To increase surface area
What separates the small and large intestines?
The ileocecal valve, which regulates the passage of material into the large intestine via a sphincter
