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MEDS1001 > digestive system > Flashcards

digestive system Flashcards

1
Q

The GI tract has

A

4 layers

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2
Q

Mucosa

A
  • Protective
  • Epithelium
  • Muscularis mucosae - thin layer of muscles, helps make folds in mucosa, more SA
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3
Q

Submucosa

A

houses blood vessels and nerves

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4
Q

Muscularis

A
  • Very muscular
  • Longitudinal and circular muscle
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5
Q

Serosa

A

Outside
- connective tissues, nerves, fat cells, blood vessels.
- Slippery layer so GI tract can move freely
- If it touches another organ - adventitia

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6
Q

Oral (buccal) cavity

A

accessory organs:
* Teeth
* Tongue salivary glands

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7
Q

Tongue salivary glands

A
  1. Parotid
    - Largest
    - Sits in front of ear
  2. Submandibular
    - Lower jaw
  3. Sublingual
    - Under tongue
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8
Q

Pharynx

A
  • Moves bolus to oesophagus
  • Made up of skeletal muscles
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9
Q

Bolus

A

chewed up food, in a ball

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10
Q

Oesophagus

A

Propel bolus to stomach
Anatomy
* Muscular tube - (~25cm long)
* Upper - skeletal muscles
* Middle - mixed
* Lower - smooth muscle

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11
Q

Anatomy of the stomach

A

j -shaped chamber
Very muscular
Rugae - ridges
4 main areas:
* Cardia, fundus, body, pylorus

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12
Q

Muscular valves (sphincter) of stomach

A

ensure movement is only one way
Top: gastro-oesophageal sphincter
Bottom: pyloric sphincter

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13
Q

Muscle layers of stomach

A

help with churning motion
1.Longitudinal layer
2.Circular layer
3.Oblique layer
Oriented diagonally

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14
Q

Chyme

A

what food is called after digestion in the stomach

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15
Q

function of the stomach

A
  • Holding reservoir
  • Mixing chamber (chyme)
  • Secretion of gastric juices
  • Secretion of gastrin
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16
Q

Anatomy of Small intestine

A

3 regions
1. Duodenum (shortests)
2. Jejunum (2-2.5m) - bulk of where chemical digestion and absorption occurs
3. Ileum (3m) - at the end ileocecal sphincter (ensures chyme travels one way)
Joins large intestine at ileocecal sphincter

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17
Q

At mucosa of small intestine

A

(at mucosa) Villi: finger-like projections of mucosa
Microvilli: hair-like projections of absorptive cells

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18
Q

function of small intestine

A
  • Receives pancreatic juice and bile
  • Secretes intestinal juice
  • Major site of digestion and absorption
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19
Q

Pancreas

A

Endocrine cells releases insulin and glucagon
Exocrine cells release pancreatic juice

20
Q

Liver

A

Largest gland
Secretes bile

21
Q

Gallbladder

A

Store and concentrate bile

22
Q

Anatomy of Large intestine

A

4 major regions:
* caecum, colon, rectum, anal canal

Sphincters:
* Internal anal sphincter (involuntary)
* External anal sphincter (voluntary)

23
Q

Functon of the large intestine

A
  • Absorption
  • Production of certain vitamins
  • Formation and elimination of faeces
  • Housing microbes
24
Q

Mechanical digestion

A

involves the physical breakdown of food into smaller particles

25
Q

Chemical digestion

A

assisted via enzymatic activity to form absorbable compounds

26
Q

If we consume carbohydrates (mostly starches)

A

we can absorb Monosaccharides (mostly glucose)

27
Q

If we consume proteins

A

we can absorb amino acids

28
Q

If we consume lipids (mostly triglycerides)

A

we can absorb fatty acids

29
Q

Oral cavity

A
  • Saliva (99.5% water, 0.5% solutes)
  • Mucus lubricates food
  • Immunoglobulin A (IgA) prevents microbes from attaching to epithelium
  • Mechanical digestion via mastication
  • Chemical digestion via action of two enzymes in saliva
    1. Salivary amylase digests starch to maltose
    2. Lingual lipase digests triglycerides
30
Q

Oesophagus: motility

A

Propulsion of bolus via peristalsis

31
Q

Peristalsis

A

continuous waves of contraction and relaxation of muscles down the tract

32
Q

Stomach: Mechanical digestion, motility

A

Peristaltic contractions ~3/min push bolus towards pylorus (propulsion)
1. Contractions strengthen towards the pylorus grinding contents
2. Pylorus allows 1/10 of chyme it holds to **pass through pyloric valve per contraction
3. Contractions also close pyloric value and remaining contents are propelled back (retropulsion**)

33
Q

Gastric Pits in the Stomach consist of:

A
  1. Pareital cell
  2. Chief cell
  3. Mucous cell
  4. G cell
34
Q

Parietal cell

A
  • secretes HCl - kills microbes, denatures proteins, converts pepsinogen to pepsin
  • Secretes intrinsic factor - needed for transportation & absorption of vitamin B12 in ileum
35
Q

Chief cell

A
  • release pepsinogen (inactive enzyme) and active form (pepsin) and breaks proteins into peptides
  • Secretes gastric lipase - breaks triglycerides into fatty acids and monoglycerides
36
Q

Mucous cell

A

release bicarbonate-rich mucus
* lubrication, protects stomach wall from protein digestion, corrosion

37
Q

G cell

A

releases gastrin (hormone) into bloodstream, stimulates parietal cells to secrete HCl and chief cells to secrete pepsinogen

38
Q

Bile secreted by liver

A
  • Bile salts: emulsifies fats, facilitate absorption of fat and cholesterol
  • Bilirubin: pigment that is a waste product from the breakdown of red blood cells.
  • Gallbladder stores and concentrates bile by absorbing water and ions
39
Q

intestinal juice

A
  • secretion stimulated by acidic chyme
  • 1-2 L/day
  • pH 7.4-7.8
  • Water, mucus, enzyme-poor
40
Q

Pancreatic juice

A
  • 1.2-1.5 L/day
  • Water
  • Bicarbonate ions: neutralizes HCl from stomach
  • Pancreatic proteases released in active form e.g. trypsinogen activated to trypsin
  • Pancreatic amylase, lipases, nucleases
41
Q

Small intestine: chemical digestion

A
  • Largely occurs in the duodenum
  • All forms of organic compounds are digested in the small intestine
  • Most enzymes are transported from pancreas
  • Brush border enzymes: on plasma membrane of microvilli
42
Q

Optimal digestive activity relies on…

A

slow delivery of chyme from stomach
* Regulate against hypertonicity of entering chyme
* Allows low pH of chyme to be neutralised

43
Q

Small intestine: motility & absorption

A

Peristalsis moves chyme through intestinal tract, ~16 contractions/min

Segmentation the most common motion in the jejunum
* Localised contractions and relaxations move chyme back and forth a few centimetres
* Promotes mixing, absorption of nutrients and water

44
Q

Small intestine: absorption

A

Water-insoluble products of lipid digestion, fat-soluble vitamins, cholesterol form micelles with bile salts
* Components transferred to absorptive cells
* Lipids would ‘float’ in chyme without micelles
* Normally occurs in ileum

45
Q

large intestine: motility

A

Haustral contractions in ascending and transverse colon
* Slow segmenting movements lasting ~1 min aids with mixing and water absorption
* Occurs every 30min

Peristalsis occurs 3-4 times/day
* Allows for mass movement of content towards rectum

46
Q

Large intestine: digestion, absorption

A

Some digestion of resident bacteria
- Insoluble carbohydrates broken down via fermentation -> short-chain fatty acids

Absorbs remaining water and electrolytes (Na+, Cl -)
Absorbs vitamins synthesised by resident bacteria (vitamin B complexes, vitamin K)

MEDS1001 (21 decks)

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