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Human Biology > Digestive System > Flashcards

Digestive System Flashcards

1
Q

What does the GI tract do

A

Moves nutrients, water and electrolytes from the external environment to the internal environment

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2
Q

Function of the digestive system

A

Breaks down large molecules to small, soluble molecules that can be absorbed and used by body cells

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3
Q

7 activities of the digestive system

A
  1. Ingestion
  2. Mastication
  3. Deglutination
  4. Digestion
  5. Absorption
  6. Peristalsis
  7. Defecation
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4
Q

Ingestion

A

Intake of food into the mouth

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5
Q

Mastication

A

Chewing food which pulverises it and mixes it w saliva

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6
Q

Deglutination

A

Swallowing, moving food from mouth to pharynx and to the oesophagus

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7
Q

Digestion

A

Mechanical and chemical breakdown of food to prepare it for absorption

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8
Q

Absorption

A

Passage of food molecules through mucous membrane of the small inetstine and into blood and lymph for distribution to cells

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9
Q

Peristalsis

A

Wavelike contractions of the smooth muscle of the intestines that move food through GI tract

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10
Q

Defecation

A

Discharge of indigestible waste from GI tract

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11
Q

What does the food entering the digestive system pass through

A
  1. Mouth
  2. Pharynx
  3. Oesophagus
  4. Stomach
  5. Small Intestine
  6. Large Intestine
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12
Q

The 4 layers of the wall of the GI tract and what they are made of/ secrete

A
  1. Mucosa: mucous membrane, contains glandular cells that secrete digestive enzymes and goblet cells that secrete mucous
  2. Submucosa: contains blood vessels
  3. Muscularis: a layer of circular muscle and longitudinal muscle
  4. Serosa: secretes serous fluid that keeps outer surface moist
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13
Q

Mechanical digestion

A

In the oral cavity as teeth crush food and in the stomach as its muscular walls churn food

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14
Q

Chemical digestion (3)

A
  1. HCl denatures proteins
  2. Bile salts emulsify lipids
  3. Specific enzymes hydrolysis chemical bonds
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15
Q

What does saliva consist of (3)

A
  1. Water
  2. Mucous
  3. Digestive enzyme salivary amylase
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16
Q

What happens after the food is chewed and moistened

A

The tongue forms a ball like mass called a bolus and pushes it into the upper part of the throat, the pharynx

17
Q

Where does the food go after the pharynx

A

Food enters the oesophagus and moves down towards the stomach

18
Q

What regulates entry into the stomach

A

The lower oesophageal sphincter

19
Q

What is secreted by the stomach

A

Gastric juice is secreted by gastric glands in the stomach

20
Q

What type of digestion occurs in the stomach

A
  • Chemical (gastric juices)
  • Mechanical (churning of the stomach)
21
Q

What do the specialised epithelial cells in the stomach do

A

Secrete mucous to protect the stomach lining from being attacked by acid and pepsin

22
Q

4 regions of the stomach

A
  1. Cardia
  2. Fundus
  3. Body
  4. Pylorus
23
Q

4 layers of the stomach wall

A
  1. Mucosa
  2. Submucosa
  3. Muscularis
  4. Serosa
    (same as other 4 tunicas found in the other regions of GI tract)
24
Q

the 5 types of cells in the gastric glands and what they secrete

A
  1. Goblet cells: secrete protective mucous
  2. Parietal cells: secrete HCl
  3. Chief cells: secrete pepsinogen
  4. Argentaffin cells: secrete serotonin, histamine, autocrine regulators
  5. Endocrine cells (G cells): secrete the hormone gastrin into the blood
25
Q

How does the stomach control the production of gastric juice

A

A hormone, gastrin

26
Q

What happens when the chyme is ready to leave the stomach

A

The gate of the small intestine, the pyloric sphincter, opens and allows limited amounts of chyme to pass

27
Q

What does the pancreas secrete (2)

A
  • Pancreatic juice including enzymes
  • An alkaline solution that neutralises the acidic chyme to provide an environment where the enzymes can act
28
Q

How does the liver aid in digestion

A

Aids in the digestion of lipids by secreting bile. Bile contains bile salts which emulsify lipids.

29
Q

Where does most of the digestion take place

A

The small intestine

30
Q

What is the first 25cm of the S.I known as and what occurs here (3)

A

The duodenum:
1. Starches and glycogen are broken down to sugars
2. Proteins are broken down to amino acids
3. Triglycerides are broken down to fatty acids and glycerol

31
Q

How are nutrients absorbed in the S.I

A
  • Mucosa and submucosa of S.I thrown into folds, which are covered by projections called villi
  • The epithelial cells of the villi are covered in microvilli
  • Within each villus are a network of capillaries and a lymphatic vessel
  • Each amino acid and monosaccharide must use a carrier molecule to get into an epithelial cell of a villus
  • Once they are in the epithelial cells they eventually accumulate and move by facilitated diffusion through the base of the cell and into the blood
  • In bloodstream they are taken to the liver for processing and storage
32
Q

How are lipids absorbed

A
  • After triglycerides are broken down into fatty acids and glycerol they become surrounded by bile salts called micelles
  • The shell of the bile salt is discarded and they move easily across the membrane and into the cell
  • Short chained fatty acids are absorbed directly into bloodstream
  • Longer chained fatty acids are reasembled into triglycerides by the ER and encased in a protein (particle known as a chylomicron)
  • After processing they pass out of the epithelial cell and into the lymphatic fluid
  • The chylomicrons pass through the capillaries of the liver and adipose tissue and an enzyme breaks them down to fatty acids and glycerol
  • These products diffuse from blood stream into liver and adipose tissue where they are resynthesised into triglycerides and stored for later when energy is required
33
Q

Role of large intestine (colon) (3)

A
  1. Absorb sodium ions and water
  2. Eliminate wastes
  3. Provide a home for friendly bacteria

Human Biology (5 decks)

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