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ESA 1 Body Logistics (BG) > The Digestive System > Flashcards

The Digestive System Flashcards

1
Q

What are the four layers of the gut wall?

A
  • Mucosa (innermost)
  • Submucosa
  • Muscularis externae (external muscle layers)
  • Serosa (outermost)
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2
Q

What is the submucosa?

A

A layer of connective tissue bearing glands, arteries, veins and nerves.

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3
Q

What is the muscularis externa?

A

Two layers of smooth muscle

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4
Q

How does the muscularis externa help move luminal contents along the gut?

A

By creating peristaltic waves

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5
Q

What is in the serosa?

A

A simple squamous epithelium (mesothelium) and connective tissue

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6
Q

What are the differences between the inner and outer layer of smooth muscle in the muscularis externa?

A

Inner layer = circular with nuclei in the centre of the cell.

Outer layer = longer and flattened with cigar shaped nuclei.

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7
Q

What’s are the major functions of the GI tract?

A
  • To provide a port of entry for food into the body
  • To mechanically disrupt the food
  • To temporarily store the food
  • To chemically digest the food
  • To kill pathogens in the food
  • To move food along the tract
  • To absorb nutrients from the resultant solution
  • To eliminate residual waste material
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8
Q

Characteristics of Saliva:

A
  • Starts digestion (amylase and lipase)
  • Bacteriostatic (contains IgA)
  • High calcium
  • Alkaline
  • Assists swallowing
  • Protects the mouth
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9
Q

Upper end Oesophagus

A

Voluntary control (some striated skeletal muscle)

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9
Q

Lower end Oesophagus

A

Involuntary control (solely smooth muscle)

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10
Q

How does the Oesophagus work?

A

Rapid peristaltic transport transports bolus to stomach (8-9s)

(Fastest GI transport is on entry and exit)

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11
Q

Innervation in the Oesophagus

A

Myenteric plexus

Submucosal plexus

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12
Q

What is in the mucosa?

A

Epithelium

Lamina propria - loose connective tissue bearing blood is and lymph vessels, some smooth muscle cells and immune cells

Muscularis mucosae - thin layer of smooth muscle cells

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13
Q

Stomach storage:

A

Acts as a necessary food store (we eat faster than we digest)

Wall relaxes so pressure doesn’t rise (receptive relaxation)

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14
Q

Stomach initial disruption:

A

Contracts rhythmically to mix and disrupt

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15
Q

Stomach disinfection

A

Stomach secretes acid and proteolytic enzymes to break down tissues and disinfect

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16
Q

Stomach final action

A

Produces hypertonic chyme by combined action of acid, enzymes and agitation

Delivers incompletely digested chyme slowly, and in a controlled way to the duodenum

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17
Q

What is the name of the folds of gastric mucosa in the stomach?

A

Rugae (pronounced roojie)

18
Q

Describe the gastric glands of the mucosa:

A

Long, straight tubular gastric glands extending from the gastric pits to the muscularis mucosa

19
Q

Describe the gastric pits of the mucosa of the stomach

A

Shallow, lined by mucous cells

20
Q

How does the mucus secreted by surface mucous cells protect the stomach lining?

A

The mucus contains HCO3- which neutralises the H+ ions.

It is also resistant to pepsin degradation

21
Q

Constituents of the gastric gland:

A
  • Gastric pit - lined by mucus secreting cells
  • Isthmus - where stem cells divide to populate the gland by up/downward migration
  • Parietal cells - secrete H ions into the lumen and HCO3 ions into capillaries
  • Chief cells - secrete pepsinogens
  • Enteroendocrine cells - include G cells which secrete gastric
22
Q

Shape of duodenum:

A

20-25cm long, C shaped, proximal portion of small intestine

Curves around head of pancreas

23
Q

Steps of dilution in the duodenum:

A
  • Water drawn in from the ECF
  • Liver releases bile (water, alkali, bike salts)
  • Pancreas and liver secrete alkalis
  • Pancreas, liver and intestine secrete enzymes which with bile complete digestion
24
Q

Completion of digestion with enzymes from pancreas and intestine steps:

A
  • Cleave peptides to amino acids
  • Cleave polysaccharides to monosaccharides
  • Break down and re-form lipids
  • Break down nucleic acids
25
Q

Requirements for absorption

A
  • Requires a lot of energy
  • Requires a large surface area (gut is folded, villi, micro-villi)
  • Adequate contact time
  • Good blood supply/drainage (liver/hepatic portal vein)
26
Q

Dimensions of Small Intestine

A

22 feet/7 meters
2.5 cm in diameter
SA of 25 (meters squared)

27
Q

What is the name of the folds of the Jejunum?

A

Plicae circulares

28
Q

What does the Duodenum absorb?

A

Iron

29
Q

What does the Jejunum absorb?

A

Most of the sugars, AA’s and fatty acids

30
Q

What does the Ileum absorb?

A

Vitamin B12, bile acids and remaining nutrients

31
Q

What are the areas of the Large Intestine?

A
  • Caecum
  • Ascending colon
  • Transverse colon
  • Descending colon
  • Sigmoid colon
32
Q

Dimensions of the Large Intestine:

A

1.2 m long and 6-9cm wide

33
Q

What does the epithelium of the crypts of Lieberkuhn produce?

A

Mucus and supplies cells to the surface

Surface epithelial cells absorb water and electrolytes

34
Q

Bacteria of the Large Intestine are involved in:

A
  • Synthesis of vitamins K, B12, thiamine and riboflavine
  • Breakdown of 1’ to 2’ bile acids
  • Conversion of bilirubin to non-pigmented metabolites
35
Q

Decreased absorption or increased secretion of the gut can result in:

A

Life threatening dehydration

Life threatening electrolyte imbalance

36
Q

Somatic neural control is involved in:

A

Ingestion (mouth and first third of Oesophagus)

Excretion

37
Q

Autonomic nervous system controls what parts of the digestion:

A

All apart from ingestion and excretion

38
Q

Paracrine control of the gut

A

Histamine (production of acid in stomach)

Vasoactive substances (affect blood flow in gut)

39
Q

Endocrine control of the gut hormones control:

A
  • Secretion of stomach acid
  • Alkali secretion from liver and pancreas
  • Enzyme secretion
40
Q

What does Secretin do?

A

Promotes bicarbonate secretion from duct cells of pancreas

Promotes bike production by the liver

Inhibits secretion of acid by parietal cells of stomach

41
Q

What does Cholecystokinin (CCK) do?

A

Made and secreted by enteroendocrine cells of the duodenum

Promotes release of digestive enzymes from the pancreas

Promotes release of bike from the gall bladder

Is a hunger suppressant

42
Q

What does Gastrin do?

A

Promotes HCl production (gastric acid) by the parietal cells of the stomach.

Released by G cells of pyloric antrum of stomach, pancreas and duodenum.

ESA 1 Body Logistics (BG) (11 decks)

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