Term
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Definition
-neutralization of chyme
-digestion of peptides and sugars to dipeptides and disaccharides
-absorption of nutrients (fatty acids, amino acids, sugars), vitamins and minerals
-immune surveillance |
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Term
| small intestine gross anatomy (3 segments) |
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Definition
-duodenum: 25 cm
-jejunum: 1 M
-ileum: 2 M |
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Term
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Definition
| permanent folds of the intestine. consisting of mucosa and submucosa layers. this increases surface area 3 fold |
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Term
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Definition
| 0.5 to 1.5 mm outgrowths of the mucosa. increases surface area 10 fold |
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Term
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Definition
| extensions of the plasma membrane on the surface of the major cell types of the small intestine. these increase surface area 20 fold |
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Term
| total increase in surface area of small intestine |
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Definition
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Term
| epithelium of small intestine |
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Definition
| The epithelium of the small intestine that is thrown into villi and has simple tubular glands at the base of these structures. These glands are called the crypts of Lieberkuhn |
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Term
| cells of epithelium of sm intestine |
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Definition
-enterocytes
-goblet cells
-stem cells
-paneth cells
-M cells
-neuroendocrine cells
-intraepithelial lymphocytes |
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Term
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Definition
| the most numerous cell type. Tall columnar cells topped with microvilli whose primary function is the absorption of nutrients |
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Term
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Definition
| secrete mucus made up of glycoprotein that protects and lubricates the surface of the small intestine. |
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Term
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Definition
| found deep but not at the base of the crypts of Lieberkuhn. These cells give rise to all cell types with the exception of the intraepithelial lymphocytes |
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Term
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Definition
| cells found at the base of the crypts of Lieberkuhn that contain large esosinophilic granules. These granules contain antimicrobial substances such as lysozyme that are secreted into the crypts and control growth of intestinal flora. |
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Term
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Definition
| micro fold cells specialized epithelial cells that cover lymphoid tissue (Peyers patches)in the small intestine. This is an antigen-presenting cell that uses endocytosis to sample the content of the small intestine and then presents antigens on the basalateral plasma membrane. The basement membrane underneath the cell is discontinuous and the cell is folded in such a way that there is a large hollow area within it. Lymphocytes cross the basement membrane and enter this hollowed out area and then come in contact with the presented antigen. |
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Term
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Definition
| generally found at near the base of the crypts. These are found as two cell types one that spans the epithelia and has microvilli at the apex and probably secretes hormones in response to luminal contents. The other cell that is not in contact with the lumen. These neuoendocrine cells secrete a wide variety of hormones |
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Term
| hormones secreted by neuroendocrine cells |
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Definition
| Secretin: that triggers release of bicarbonate from the pancreas and bile duct, Gastric inhibitory polypeptide: reduces gastrin release from chief cells of stomach, Cholecystokinin: stimulates contraction of the gall bladder and pancreatic enzyme secretion. Motilin: targets smooth muscle of the gut increases motility Neurotransmitters: Serotonin and substance P that target smooth muscle of the gut and increase motility |
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Term
| intraepithelial lymphocytes |
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Definition
| mostly T cells found between enterocytes. specific function unclear |
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Term
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Definition
| the loose underlying connective tissue that make up the core of the villi. This consists clusters of smooth muscle that actually permit the villi to move. Sort of stirring the contents. It is enriched with blood vessels and a unique lymphatic called the “lacteal” that are important in the transport of nutrients taken up by the gut to the rest of the body. |
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Term
| submucosa of small intestine |
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Definition
| both this layer and to some extent the Lamina propria are have aggregations of lymphoid tissue known as Peyer’s patches. |
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Term
| histological differences in regions of small intestine |
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Definition
The duodenum has a coiled tubular glands called Brunner’s glands. These secrete mucus of a very high pH (8-9) serves to neutralize chyme. This gets overall pH closer to 7.5 to that is needed for maximal activity of pancreatic enzymes.
The jejunum and ileum are very similar. Peyers patches are more numerous in the ileum. In general the number of goblet cells increase the further down the small intestine. |
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Term
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Definition
| pancreatic amylase and also salivary amylase has broken down starches to disaccharide sugars. Enterocyte membrane bound disaccharidases convert these to monosaccharides including glucose fructose and galactose. These are brought into the enterocyte by facilitated diffusion. These diffuse into the intestinal capillaries and pass in to the portal vein into the Liver. |
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Term
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Definition
| these are first denatured by acid then cleaved into peptides by pepsin in the stomach. The peptides are digested to smaller peptides by the action of the pancreatic enzymes such as trypsin and carboxypeptidase within the duodenum. Single amino acids are released by enterocyte plasma membrane bound peptide hydrolases. The aminoacids are actively transported by a unique carrier system into the enterocyte. These diffuse into the intestinal capillaries and pass in to the portal vein into the Liver. |
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Term
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Definition
| - these are converted into a course emulsion by mechanical action of the stomach. They are transformed into a fine emulsion by bile acids in the duodenum. The triglycerides are broken down into free fatty acids and monoglycerides by the action of pancreatic and stomach lipases. These components are absorbed by the enterocyte and then are transported to the SER where they are reassembled to triglycerides. These are coalesced into larger lipid droplets inside vesicles. These large droplets are exocytosed at the basolateral surface of the enterocyte. These diffuse between cells and though the basement membrane. These lipid drops cannot pass into capillaries, but the sinusoidal nature of lacteals (the lymphatics that run in the lamina propia of the villi) permit entry of these aggregations. Once in the lymphatics these lipid drops become coated with phospholipids and proteins and are called chylomicrons and these renter the general circulation via the thoracic duct thus bypassing the liver. |
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Term
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Definition
Folate is disassembled prior to absorption.
B12 or cobalamin requires formation of a complex with gastric intrinsic factor to be taken up by enterocytes through receptor-mediated endocytosis.
Ascorbic acid appears to be readily taken up
Vitamin A is taken up with lipids. |
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Term
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Definition
| Many such as K Na Cl etc pass through channels. Others such as iron require binding to an organic molecule such as heme for efficient uptake. Calcium requires the action of the hormone vitamin D to be taken up by the enterocyte. |
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Term
| function of large intestine |
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Definition
-elimination of waste products
-uptake of water
-immune surveillance |
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Term
| gross anatomy of lg intestine (3 segments) |
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Definition
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Term
| epithelium of mucosa of lg intestine |
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Definition
| simple columnar epithelia with goblet cells and has no villi, but it does have simple tubular glands. |
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Term
| cells of the epithelium of the colon |
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Definition
-absorptive cells
-goblet cells
-stem cells
-neuroendocrine cells |
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Term
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Definition
| simple columnar epithelial cells with short microvilli. Mainly specialized for the uptake of water. |
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Term
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Definition
| : very abundant and found in glands secrete mucus to facilitate the passage of feces. |
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Term
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Definition
| found in the glands give rise to all three epithelial cell types. |
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Term
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Definition
| much fewer in number than small intestine. No specific hormone found in colon that is not found in the small intestine |
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Term
| muscularis propria of large intestine |
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Definition
| this is not continuous divided into three sections called the Tenia coli. The muscle is quite prominent. |
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Term
| rectal anal junction, epithelium of mucosa |
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Definition
| transitions from simple columnar to stratified squamous to epidermis. At the junction are large branched tubular glands called the circumanal glands that provide (lubrication). The muscle that underlies the structure is skeletal muscle. |
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Term
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Definition
| Most colon cancers are thought to be the result of a multistage disease process. The disease has distinct histological stages. In may cases the cancers start as hyperplasia then develop into benign polyps and adenomas. Ultimately a carcinoma (a malignant tumor) arises from the cells of the adenoma and this ultimately will lead to death due to blockage of the colon, or metastasis to a distant site. Of particular importance to our understanding of cancers is that specific mutations in oncogenes or tumor suppressors are correlated with the histological changes observed in the disease. This concept is referred to as multistage carcinogenesis where separate mutagenic events lead progressively more cancers cells. |
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Term
| what causes multiple mutation |
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Definition
80% of colon cancer cases are found in individuals 60 to 70. There are 150,000 new cases of colon cancer every year in the US and ~58,000 deaths due to the disease. There is a 2-fold increase of the incidence of the disease in men. These numbers of cases are 60% higher than non-western nations.
These epidemiological findings suggest diet as the cause of increased colon cancer in the US.
It is believed that a diet low in content of unabsorbable vegetable fiber, high content of fat and low content of protective phytonutrients lead to stools with a high concentration of carcinogens. These carcinogens are responsible for the mutations that transform the stem cells of the colonic epithelium to cancer cells. |
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Term
| what are the functions of the colon? |
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Definition
| -elimination of waste products, uptake of water, immune surveillance |
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Term
| describe the normal colonic epithelium? |
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Definition
| simple columnar epithelial with abundant goblet cells and simple tubular glands |
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Term
| what cell types are found in the epithelia of the colon? |
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Definition
| -absorptive cells, goblet cells, neuroendocrine cells and stem cells |
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Term
| what cell types give rise to colon cancers? |
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Definition
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