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BRS 8 G: GASTROENTEROLOGY > 8.w Small Bowel > Flashcards

8.w Small Bowel Flashcards

1
Q

Function of the small bowel

A

Absorb nutrients, salt and water

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2
Q

Measurements of small bowel

A

6m long

3.5 cm diameter

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3
Q

How long is the duodenum

A

25cm

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4
Q

How long is the jejunum

A

2.5 m

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5
Q

How long is the ileum

A

3.75m

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6
Q

Duodenum split to

A

D1-4(at the duodenojejunal flexure)

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7
Q

Mesentery

A

Membrane holding intestine in pkace

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8
Q

Functions of the mesentery

A

Suspends small and large bowel from posterior abdominal wall (holds them in place whilst still allowing some movement)

Provides a conduit for blood vessels, lympqthic vessels and nerves

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9
Q

Vessels in the mesenteru

A

Middle colic artery
Right colic artery
Ileocolic artery
Jejunum and ilea’s arteries
Superior mesenteric artery

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10
Q

Enterocytes

A

Absorptive cells (columnar)

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11
Q

How are digestive epithelium adapted to their function

A

Plicae circulares Inc sa (on them are villi)

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12
Q

Where is the only place villi are present

A

Small intestine

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13
Q

Which cells are in crypts of lieberkuhn

A

Paneth and stem cells

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14
Q

Cell types in villi

A

Simple columnar epithelium containing Enterocytes, goblet cells, enteroendocrine cels

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15
Q

Life span of Enterocytes

A

1-6 days

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16
Q

Enterocytes look

A

Tall columnar cells with micro villi and a basal nucleus

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17
Q

What make up the brush border

A

Microvilli

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18
Q

What covers the surface of microvilli

A

Glycocalyx

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19
Q

Glycocalyx

A

Rich carb layer on apical membrane

Protects from digestion at lumen but allows absorption

Traps the unstirred layer (water and mucous) to emulate the rate of absorption from interstitial lumen

20
Q

What causes goblet shape of goblet cells

A

Mucous containing granules accumulate at apical end

21
Q

Where is there a greater abundance of goblet cells

A

Colon

22
Q

Where is the lower abundance of goblet cells

A

Duodenum

23
Q

Abundance of goblet cells

A

Increase along length of bowel

24
Q

Mucous

A

Large glycoprotein facilitating passage of material through bowel

25
Q

Goblet cells function

A

Secrete mucous

26
Q

Enteroendocrine cells (chromaffin)

A

Hormone secreting to influence gut motility

Columnar seen between Enterocytes

27
Q

Paneth cells

A

Found in bases of crypts only

Contain large acidophillic granules (contain lysozyme glycoproteins and zinc)

Engulf some bacteria and Protozoa

28
Q

Stem cells

A

Undifferentiated cells which remain capable of cell division to replace cells which die

29
Q

Epithelial stem cells in gi tract

A

Essential to replenish surface epithelium

Continually divide by mitosis then migrate to tip of villus to replace cells which die by apoptosis

30
Q

Why is lifespan of Enterocytes and goblet cells shorter than other epithelial cell types

A

Entrocytes are first line of defence against gi pathogens and may be directly affected by toxic substances in diet

31
Q

What distinguishes the duodenum from the rest

A

Brunners glands in Submucosa

Secrete alkaline fluid to neutralise acid chyme and protect proximal small bowel
Optimise ph for action of pancreatic digestive enzymes

32
Q

Jejunum vs. Ileum

A

Jejunum thicker walls and has plicae circulares

Ileum thinner walls and has peters patches more arterial arcades

33
Q

Purpose of small bowel motility

A

Mix ingested food with digestive secretions and enzyme

Propel,contents along tract

Facilitate contact between contents and intestinal mucosa

34
Q

Segmentation in motility of small bowel

A

Mixes contents of lumen

Stationary contraction of circular muscles at intervals

Net movement of chyme toward colon

35
Q

Are contractions more frequent in duodenum or ileum

A

Duodenum

36
Q

Peristalsis in motility of the small bowel

A

Propels

Sequential contractiom of adjacent rings of smooth muscle

Propels chyme toward colon

37
Q

How far do waves of peristalsis tend to travel

A

10cm

38
Q

Migrating motor complex in motility of the small bowel

A

Cycles of smooth muscle contraction through gut to prevent migration or colonic bacteria into ileum

39
Q

What type of environment does digestion in the duodenum occur

A

Alkaline

40
Q

Where do pancreatic digestive enzymes and bile enter the duodenum from

A

Main pancreatic duct and central bile duct

41
Q

Digestion of carbohydrates

A

Mouth - salivary alpha amylase

Pancreatic alpha amylqse into duodenum, continues digestion of starch and glycogen (needs cl- and alkaline)

Absorbed

42
Q

Absorption of digested carbs

A

Glucose and galactose : Secondary active transporter (by carrier protein sglt-1 on apical membrane)

Fructose: facilitated diffusion by glut-5 on apical membrane

Glut-2 exit at basolateral

43
Q

Digestion of protein

A

Begins in stomach by pepsin

Small bowel enterokinase activates trypsin which activates other proteases which hydrolyse proteins to amino acids or oligo peptides

Peptidases at brush borders of Enterocytes hydrolyse oligopeprodes to amino acids

Enterocytes directly absorbs small oligopeprodes via PepT1 which are digested to amino acids by peptidases in Enterocytes

44
Q

Digestion of lipids

A

Secretion of bile salts and pancreatic lipases

Emulsification

Enzymatic hydrolysis of ester linkages

Solubilisation of lipolytic products in bile salt micelles

45
Q

Absorption of lipids

A

Enterocytes (fatty acids and monogylcerides leave micelles into)

Reshntnesizes into triglycerides by monoglyceride Acylation and phosphotidic acid pathway

Synthesised to chylomicrons in Golgi apparatus

Secreted across basement membrane by exocytosis and enter lacteals for lymph transport

46
Q

Ileocaecal valve

A

Separate ileum and colon

Relaxation and contraction controls passage of material into colon and prevents back flow of bacteria to ileum

BRS 8 G: GASTROENTEROLOGY (4 decks)

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