Term
| What are the major functions of the large intestine? |
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Definition
- Reabsorption of water, compaction of feces
- Absorption of vitamins made by local bacteria: Vit K
- Storage of fecal material
**Little to no digestion, 10% of nutrient absorption |
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Term
| What is the anatomy of the large intestines? |
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Definition
- Secum - receiving chamber from small intestines. Appendix offshoot
- Ascending colon
- Transverse colon
- Descending colon
- Sigmoid colon
- Rectum - only contraction moves fecal material here.
**Sections = huestra. Undergo contraction and segmentation |
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Term
| What controls the valve between the small and large intestines? |
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Definition
The ileocecal valve - Pressure in the small intestine relaxes sphincter.
Under PSNS/SNS control, reacts to gastroileal and gastrocolic reflexes |
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Term
| What is the anatomy of the anal canal? |
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Definition
- Rectal valve - prevents passage of feces when passing gas. Gas comes from microorganisms eating undigested food.
- Pectinate line - separates rectum from anus. Pain is felt below the line.
- Hemorrhoidal veins are more oxygenated then normal, blood is bright red. |
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Term
| What is secreted in the colon? |
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Definition
| Mucus from goblet cells, no enzymes |
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Term
| What bacteria exist in the colon? |
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Definition
Lactobacillus, Bifidobacterium, Streptococcus are good bacterium.
Production of Vit K, B5, B7. Compete for attachment sites, preventing bad microorganisms AND antagonize bad bacteria.
Production of lymphatic tissue and antibodies that cross-react w/ negative bacteria. |
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Term
| What are the steps of the defecation reflex? |
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Definition
- Distention of the rectum stimulates stretch receptors --> activation of PNS long reflexes and increased perstalsis
- Stretch reflexes also can promote short reflexes through the ENS --> myenteric plexus.
**Contraction of external sphincter, relaxation of internal. |
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Term
| What are the different types of hemorrhoids? |
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Definition
- Internal hemorrhoids - above the pectinate line, less painful
- External hemorrhoids - outside of the anus
- Prolapsed hemorrhoid - Internal gets so large it falls out |
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Term
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Definition
| Increased pressure results in pockets. Material and bacteria can get trapped, resulting in infection. |
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Term
| What are the symptoms of IBS? |
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Definition
- Abdominal pain/discomfort
- Altered bowels: constipation or diarrhea, urgency
- Bloating
- Mucorrhea
- Stress related |
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Term
| What are the different types of IBS? |
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Definition
- IBS-A - alternating diarrhea and constipation
- IBS-C - constipation
- IBS-D - diarrhea
- IBS-M - both |
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Term
| What is the pathophys behind IBS? |
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Definition
- Altered motility - in small and large intestines. May be due to serotonin.
- Visceral hyperalgesia - enhanced perception of motility and pain
- Psychology - increased depression, anxiety.
- Mucosal inflammation - increased T cells in lamina propria -- diarrhea. Mast cells in both types
- bacterial overgrowth/large intestinal flora changes - bloating |
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Term
| How does motility affect IBS? |
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Definition
- Increase motility = diarrhea. Increased serotonin due to reduced reuptake. Incr CRF in response to stress.
- Decreased motility = constipation. Decreased serotonin activity. |
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Term
| What test involves visceral hyperalgesia? |
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Definition
Administration of methacholine has an effect where it normally would not.
Methacholine is a cholinergic stimulant |
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Term
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Definition
Inflammatory bowel disease:
- Ulcerative colitis - colon only. Humoral immunity - Th2 cells
- Crohn's disease - can affect any part of GI, but usually ileum or colon. Cellular immunity - Th1 or Th17 cells
**Thought to be a defect in mucosal immune system, in the epithelial barrier, or caused by a microorganism |
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Term
| What parts of immunity contribute to IBD? |
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Definition
- Innate immunity - the acute response. Releases cytokines, NK cells --> Presentation of antigen
- Adaptive immunity - Recognition of antigen --> cytokine release, adhesion molecules, Th1/Th2/Th17 |
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Term
| What are the steps to the immune response in IBD? |
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Definition
A macrophage engulfs foreign material, presenting it to a naive T-cell. Release of IL-12 begins activation of the T-cell, IL-2 finishes activation.
Activated T-cell releases:
- Il-12 --> Th1 cells - release Il-6. In Crohn's, Cellular immunity
- Il-4 --> Th2 cells - release IL's. In UC, humoral immunity
- Il-21/23 --> Th17 cells - release IL-6. In Crohn's, cellular immunity |
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