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Nutrition > Chapter 4 - Human Digestion and Absorption > Flashcards

Chapter 4 - Human Digestion and Absorption Flashcards

1
Q

Types of Tissues in the body

A
  • Epithelial: skin and linings of GI tract which absorb, secrete, cover and protect underlying tissues
    • Connective: supports, protects and holds the body
    • Muscle: contract and relax and permits movements
      • Nervous: transmit nerve impulses
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2
Q

Roles of GI tract

A
  • Digestion of food
    • Absorption of nutrients
    • Excretion of wastes
    • Aids with immunology
      • Houses bacteria
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3
Q

GI Tract/Alimentary Canal flow

A
  1. Mouth and salivary glands
    1. Esophagus
    2. Stomach
    3. Pancreas
    4. Liver
    5. Gall bladder
    6. Small Intestine
    7. Large intestine
    8. Rectum
      1. Anus
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4
Q

Layers of GI Tract

A
  • Mucosa: the innermost layer lined with epithelial cells and glands
    ○ Lined with lumen: tiny, fingerlike structures which increases the surface area of the mucosa
    • Submucosa: second deepest layer consisting of loose connective tissues, glands, blood vessels and nerves
      ○ Blood vessels carry nutrients and substances from GI tract
    • Muscle: a double layer with an inner layer of smooth circular muscles which encircle the tube and an outer layer of longitudinal muscle fibers
      ○ Both muscle layers help move food through the tube
      • Serosa: the outer layer which protects the tract, and secretes serous fluid to cushion and reduce friction as it moves
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5
Q

Sphincters of GI Tract

A
  • Lower esophageal sphincter: prevents backflow(reflux) of the stomach contents into the esophagus
    • Pyloric Sphincter: controls flow of stomach contents into the small intestine
    • Hepatopancreatic sphincter: controls flow of bile, pancreatic juices from common bile and pancreatic ducts into the small intestine
    • Ileocecal valve: prevents contents from large intestine reentering small intestine
      • Anal sphincters: prevents defecation until a person desires too
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6
Q

Peristalsis

A

moves food down the GI tract in a coordinated wave of muscular contractions of the two muscle layers of the GI tract wall
○ Most frequent peristalsis contractions occur in the small intestine(every 3-4 secs)
○ Large intestine only has peristalsis contracts 2-3 times per day normally after meals which lead to mass movements of fecal matter

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7
Q

Segmentation

A

occurs in the small intestine where contents are broken apart and mixed with digestive juices

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8
Q

Digestive Enzymes

A
  • Enzymes which break down macronutrients through hydrolysis reactions
    • Produced in the salivary gland, pancreases, stomach and small intestine
    • Pancreas adjusts its enzyme production to match the macronutrient content of the diet
      • Food not completely digested will be converted by bacteria in LI into gases and acids which can bloat the abdomen
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9
Q

Secretions alongside Digestive Enzymes within the GI tract

A
  • Saliva from salivary glands
    • Mucus produced along entire tract
    • HCI from stomach
    • Bicarbonate from pancreas
    • digestive enzymes from pancreas
    • Bile from liver
  • Hormones
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10
Q

Where Digestion Begins

A

as we cook
○ Dicing, pounding, marinating and heating
○ E.g. starch granules in food swell as they soak up water during cooking making it easier to digest

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11
Q

Bolus

A

mass of food that is swallowed

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12
Q

Stage of Digestion: Mouth

A
  • Teeth grind and tear solid food
    • The tongue presses morsels of food against hard palate and helps mix the food with saliva
      • Food bolus drops onto epiglottis, preventing it from going down the trachea and instead the esophagus relaxes and opens
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13
Q

Taste and Smell

A
  • We have taste buds on the papillae of our tongue and soft palate which detect compounds in food
    • 80% of taste is due to smell
    • Due to 6 million olfactory cells in the nose which are stimulated when we chew
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14
Q

5 basic tastes

A

5 basic tastes of the tongue:
- Sweet
- Salty
- Sour
- Bitter
- Umami: savory, brothy or meaty taste from amino acids
e.g. MSG, parmesan cheese

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15
Q

Stages of Digestion: Stomach

A
  • Entry of food is through the lower esophageal sphincter
    • 3 muscle layers mix the food in the stomach with the gastric juices
    • Mixing transforms food into chyme: a soupy acidic mixture
  • GDIP and pyloric sphincter then slowly releases chyme into the SI
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16
Q

Gastric Juices in Stomach

A

○ HCI
○ Gastric lipase
○ Pepsinogen
- Mucus(coats lining of the stomach which protects it from self-digestion)

17
Q

Stage in Digestion: Small Intestine

A
  • enters into duodenum, then jejunum and finally ileum
  • lined with microvilli and Vili which increase its surface area 600 times over which contributes to its efficiency in absorbing nutrients
    • The circular folds, which is the mucus membrane folding over and over again forces the chyme to flow slowly in a spiral motion, completely mixing the chyme with digestive juices and bringing it into contact with villi.
18
Q

What are Villi Lined with to increased absorption of Nutrients

A

○ Goblet cells: secrete mucus
○ Endocrine cells: produce hormones and hormone like substances
○ Cells which produce digestive enzymes
- Enterocytes: Cells which absorb nutrients

19
Q

Accessory Organs

A
  • Involves the Liver, Gallblader and Pancreas
  • they work to help SI digest but do not physically get involved
    • Secretions from these organs are delivered through the common bile duct and the pancreatic duct which come together at the hepatopancreatic sphincter and empty into the Duodenum
20
Q

Accessory Organs: Liver

A
  • Liver produces bile which contains cholesterol and aids in fat digestion and absorption
    Bile breaks the large fat globules into micelles; tiny fat droplets suspended in watery chyme
21
Q

Accessory Organs: Gallbladder

A
  • Bile is stored in the Gallbladder
    - Once released into the duodenum it is reabsorbed in the ileum and returned to the liver for recycling; Enterohepatic circulation
    - this process allows the release of cholesterol from the body as not all is released, and some is excreted
22
Q

Accessory Organs: pancreas

A

produces an alkalinic juice with a mix of sodium bicarbonate(NaHCO3) and enzymes
○ Neutralizes acidic chyme which protects the SI from damage
○ Digestive enzymes include:
§ Pancreatic amylase(starch)
§ Pancreatic lipase(fat)
§ Several proteases(protein)

23
Q

Hormones responsible for regulation of Digestive System: Ghrelin

A

Released by:
- Stomach before/during eating

Function:
- Increases appetite and food intake

24
Q

Hormones responsible for regulation of digestive system: Gastrin

A

released by:
- stomach and duodenum when food reaches stomach

Function:
- triggers the release of HCI and pepsinogen
- stimulates gastric and intestinal motility

25
Q

Hormones responsible for regulation of digestive system: CCK

A

released by:
- SI in response to presence of fat

function:
- Stimulates release of pancreatic enzymes and bile

26
Q

Hormones responsible for regulation of digestive system: Secretin

A

Released by:
- SI as digestion progresses or in response to acidic chyme

Function:
- Stimulates release of pancreatic bicarbonate

27
Q

Hormones responsible for regulation of digestive system: Somatostatin

A

Released by:
- Stomach, SI and Pancreas

Function:
- Inhibits release of GI hormones
- Slows Gastric emptying, GI motility and blood flow to the Intestine

28
Q

Method of Absorption for nutrients in the SI

A

○ Passive diffusion(fats, water and some minerals)
○ Facilitated diffusion(fructose)
○ Active absorption(amino acids, glucose)
- Phagocytosis/pinocytosis(large protein particles like immune substances in breast milk)

29
Q

Stage in Digestion: transport of Nutrients: cardiovascular system

A
  • Moves water soluble nutrients such as:
    ○ Proteins
    ○ Carbs
    ○ B-vitamins
    ○ Vitamin C
    ○ Short and medium fatty acids
  • are absorbed straight into the bloodstream in the capillary found in villi
    • This blood flows into the hepatic portal vein system: veins leaving the stomach, intestines, spleen and pancreas which flow into the liver
    • The liver metabolizes or stores a portion of the absorbed nutrients, and the ones not stored re-enter general circulation
30
Q

Stages in Digestion: Transport of Substances: Lymphatic System

A
  • Provides an alternative route into the bloodstream for large and fat soluble molecules:
    ○ Most fats
    ○ Vitamin A, D, E, K
    ○ Some proteins
    • Lacteals: special lympahtic vessels in the villi transport nutrients to larger lymphatic vessels connected to the thoracid duct
    • This extends from the abdomen to the neck and connects to the bloodstream at the left subclavian vein
    • Here they are now transported around as normal
31
Q

Stages of Digestion: Large Intestine

A
  • When chyme reaches the LI, only water, some minerals and undigested food fibers are remaining
  • Electrolytes such as sodium, potassium and teh rest of water are absorbed by the LI in the first half
  • housed gut microbiota metabolize complex carbs and synthesize vitamins
32
Q

Stages of Digestion: Elimination of Feces

A
  • After 12-24 hours of food travelling to get to the end of the LI, the food is in a semi solid mass
    • Peristaltic waves, normally the greatest following meals, push it into the rectum
    • This stimulates muscular reflexes in the sigmoid colon and rectum as well as relaxation of internal and external anal sphincters
      ○ External anal sphincter is under voluntary control
33
Q

Sections of Large Intestine

A

○ Colon
§ Cecum
§ Ascending Colon
§ Transverse Colon
§ Descending Colon
§ Sigmoid Colon
○ Rectum
Anus

34
Q

Dysbiosis

A

the disruption between levels of beneficial and pathogenic bacteria leading to GI infections such as vomiting, cramping, diarrhea and dehydration

35
Q

Probiotics

A

live microorganisms that colonize the LI and provide health benefits
Found in fermented foods

36
Q

Prebiotics

A

nondigestible food ingredients that promote growth of beneficial bacteria
- E.g. inulin, a carb known as fructan which is found in wheat, onions, garlic, asparagus and bananas
- E.g. resistant starch, isnt affected by digestive enzymes, meaning the bacteria in the LI can ferment it

37
Q
A

Nutrition (6 decks)

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