Week 8 Flashcards by Becky Mladenovic

Properties of chyme leaving the duodenum

Isotonic
Neutral
Partly digested

How well did you know this?

Not at all

Perfectly

Functions and adaptations of the Jejunum and ileum

Digestion
Absorbs nutrients, electrolytes and water

Villi, microvilli and plicae circulares increase surface area
Plicae circulares also slow transit time

How well did you know this?

Not at all

Perfectly

What are contained in intestinal crypts

Enterocytes
Enteroendocrine cells
Goblet cells
Stem cells
Paneth cells

How well did you know this?

Not at all

Perfectly

What carbohydrates can be absorbed in the small intestine

Monosaccharides only:
Glucose
Fructose
Galactose

How well did you know this?

Not at all

Perfectly

Common dietary carbohydrates

Starch (glucose polysaccharide)
Sucrose (glucose-fructose)
Lactose (glucose-galactose)

How well did you know this?

Not at all

Perfectly

Describe starch

20% amylose - has alpha 1,4 glycosidic bonds

80% amylopectin - has alpha 1,4 and 1,6 glycosidic bonds

How well did you know this?

Not at all

Perfectly

Describe starch digestion

Amylase breaks alpha 1,4 bonds to form glucose
Isomaltase breaks alpha 1,6 bonds to break down alpha dextrins
Maltase breaks down maltose (glucose-glucose)

How well did you know this?

Not at all

Perfectly

How are monosaccharides absorbed

Na-K-ATPase on basolateral membrane maintains Na gradient for Na and glucose/galactose cotransport via SGLUT1 on the apical membrane. Fructose moves through the apical membrane via GLUT5.
All monosaccharides cross the basolateral membrane through GLUT2 into the blood

How well did you know this?

Not at all

Perfectly

How does oral rehydration therapy work

Mixture of
Water
Glucose - to stimulate Na uptake
Na - to stimulate water uptake

How well did you know this?

Not at all

Perfectly

What proteins can be absorbed in the small intestine

Amino acids
Dipeptides
Tripeptides

How well did you know this?

Not at all

Perfectly

How does protein absorption differ in babies

Can absorb immunoglobulins from breast milk

How well did you know this?

Not at all

Perfectly

What activates trypsinogen

Enters peptides on the brush border

How well did you know this?

Not at all

Perfectly

What are exopeptidases and give examples

Break peptide bonds at the ends of the polypeptide to produce amino acids or dipeptides
E.g carboxypeptidase

How well did you know this?

Not at all

Perfectly

What are endopeptidases and give examples

Break peptide bonds in the middle of the polypeptide to produce shorter polypeptides
E.g trypsin, chymotrypsin and elastase

How well did you know this?

Not at all

Perfectly

How are amino acids absorbed in the small intestine

Enter enterocytes via Na-AA cotransporters

How well did you know this?

Not at all

Perfectly

How are dipeptides and tripeptides absorbed in the small intestine

Enter enterocytes via H+ transporters such as peptide transporter 1 (PepT1)
Cytosolic peptidases convert them to amino acids

How well did you know this?

Not at all

Perfectly

Describe Ca uptake when there is low Ca intake

Enter enterocytes via Ca channels
Cross basolateral membrane via Ca2+-ATPase which requires calcitriol (activates calbindin which shuttles calcium to the basolateral membrane)

How well did you know this?

Not at all

Perfectly

Describe calcium uptake when there is a high or normal calcium intake

Passive paracellular absorption

How well did you know this?

Not at all

Perfectly

How does iron enter enterocytes and what is the stomachs role

Iron crosses apical membrane via H+ cotransporters in its ferrous form
Stomach produces:
Gastric acid - makes iron ferrous
Gastroferrin - binds iron and keeps it in ferrous form

How well did you know this?

Not at all

Perfectly

What happens to absorbed iron if iron levels are low

Binds to transferrin (secreted by intestinal mucosa) and is transported to stores such as spleen, liver, bone marrow and Hb

How well did you know this?

Not at all

Perfectly

What happens to absorbed iron if iron levels are high

Contained in ferritin complexes so it is lost when the enterocyte dies

How are water soluble vitamins absorbed in the small intestine

Na cotransport

What vitamins does the large intestine absorb

Vitamins synthesised by colonic bacteria

How is vitamin B12 absorbed

Bound to intrinsic factor (secreted by parietal cells) to make it soluble
In the terminal ileum

Causes of B12 deficiency

Autoimmune destruction of parietal cells (also causes chronic gastritis) Terminal ileum removal e.g Chron's disease

Describe motility of the small intestine

1. Intestinal gradient BETWEEN meals - pacemakers have a higher frequency proximally which drives distal progression of contents 2. Segmentation FOLLOWING meals - contents move back and forth to control transit 3. Peristalsis

Describe motility of the large intestine

1. Haustral shuttling - segmentation in proximal colon allows remaining water to be absorbed 2. Mass movement (gastrocolic reflex) - contents move rapidly from transverse colon to rectum following meals

What stretch level in the rectum gives urge to defaecate

25%

Describe defaecation

``` Parasympathetic stimulation (pelvic) relaxes internal anal sphincter Somatic stimulation (pudendal) relaxes external anal sphincter Intra abdominal pressure increases leading to expulsion of faeces ```

What is tenesmus

Mass in rectum stretches the rectum and so causes continuous a urge to defaecate but with little or no stool passed I.e feeling of incomplete defaecation

What is IBD

Inflammatory bowel disease - idiopathic inflammation of GI tract

Causes of IBD

Genetic Environment - NSAIDs, early appendectomy, colonic bacteria, smoking (Chron's only) Triggers - antibiotics, acute infections, smoking, diet, NSAIDs

What are some extra intestinal symptoms of IBD

``` MSK problems e.g arthritis Erythema nodusum - mostly affects knees and shins Psoriasis Primary sclerosing cholangitis Eye problems ```

Typical presentation of Chron's disease

Upper GI - nausea, loose stools, weight loss Terminal ileum - anaemia, glossitis, anorexia Colon - diarrhoea and blood in stool Extra intestinal symptoms

Typical presentation of UC

Rectal bleeding Diarrhoea Abdominal pain Extra intestinal symptoms

What is lead pipe colon

Featureless colon die to loss of haustra in distal colon

Compare location of Chron's and UC

Chron's - anywhere form mouth to anus, but less rectal involvement than UC UC - rectum and extends proximally with no breaks

Compare demographics of Chron's and UC

Chron's - peaks at 15-30 and 60+ | UC - Young adults, usually female

Compare inflammatory cell involvement of Chron's and UC

Chron's - TH1 cells produce interferon gamma and IL2 | UC - TH2 cells produce transforming growth factor and IL5

Compare depth of inflammation of Chron's and UC

Chron's - transmural | UC - mucosal

Compare pattern of inflammation of Chron's and UC

Chron's - skip lesions | UC - continuous

Compare macroscopic appearance of Chron's and UC

Chron's - cobblestone | UC - pseudopolyps

What features are more common in Chron's

Fistulae - to bowel, bladder, vagina or skin Perianal disease Granulomas Fibrosis (string sign of Kantor) Gross bleeding Ileal involvement (although 15-20% ileitis in UC)

What features are more common in UC

Crypt abscess Friable mucosa - bleeds on contact Ulceration (although a common feature in Chron's) Depletion of goblet cells

Investigation for Chron's

Colonoscopy - cobblestone appearance, get biopsy to find granulomas CT with contrast - string sign of Kantor, obstruction, extra intestinal issues Barium enema/follow through - detect strictures or fistulae Bloods - anaemia

Investigations for UC

Colonoscopy - biopsy Abdominal X-ray - exclude colonic dilation Bloods - anaemia and serum markers Stool culture - rectal bleeding

Diagnosis if investigations cant distinguish between Chron's and UC

Indeterminate colitis

Pharmacological treatment of IBD

Aminosalicylates e.g sulfasalazine - flares and remission Corticosteroids e.g prednisolone - flares Immunomodulators - maintain remission

Examples of immunomodulators and how they work

Azathioprine | Infliximab - induce TNF alpha bound cells to undergo apoptosis

Surgery options for Chron's

Not curative: Resolve complications such as strictures or fistulae Colectomy (remove as little as possible)

Surgery options for UC

Curative: | Subtotal colectomy