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Year 11 2023 > Human Biology (Digestive System) > Flashcards

Human Biology (Digestive System) Flashcards

1
Q

What are the 4 functions of the digestive system?

A
  • Ingestion
  • Digestion
  • Absorption
  • Elimination
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2
Q

What is Ingestion?

A

The entrance of food into the body, via the mouth.

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3
Q

What is Digestion?

A

The breakdown of food into smaller pieces or molecules.

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4
Q

What are the two types of Digestion?

A
  • Mechanical Digestion
  • Chemical Digestion
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5
Q

What is Mechanical Digestion?

A

The physical breakdown of large ‘chunks’ of food into small pieces.

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6
Q

What is Chemical Digestion?

A

The chemical breakdown of small chunks of food into smaller molecules.

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7
Q

What is Absorption?

A

The movement of small molecules from the stomach/intestines into the blood.

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8
Q

What is Egestion?

A

The removal of undigested materials from the body.

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9
Q

Organs of the Alimentary Canal/GI Tract

A
  • Mouth/Teeth
  • Pharynx
  • Oesophagus
  • Stomach
  • Small Intestine
  • Large Intestine
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10
Q

What are the organs that food does not pass and are considered accessory organs?

A
  • Liver
  • Gall Bladder
  • Salivary Glands
  • Pancreas
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11
Q

How does the mouth perform mechanical digestion?

A

The chewing action of the jaw/teeth breaks large ‘chunks’ of food into small particles (mechanical digestion) that are mixed with saliva.

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12
Q

What are each of the types of teeth and their functions?

A

(4 per jaw) Incisors: biting and cutting i.e. biting an apple.
(2 per jaw) Canines: Grip and tear food i.e eating meat
(4 per jaw) Premolars: Crushing and grinding food
(6 per jaw) Molars: Crushing and grinding food

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13
Q

What enzyme is in the mouth that is used to perform mechanical digestion?

A

Saliva is a fluid that is secreted from the 3 salivary glands in the mouth. Saliva is used to lubricate food, and salivary amylase, an enzyme used to break down starch into disaccharides.

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14
Q

What is the oesophagus? What process is used to move food down the oesophagus?

A

It is a tube that connects the pharynx to the stomach. It has a double layer of muscle circular and longitudinal. As the bolus enters, there is a wavelike relaxation of the circular muscle behind and in front of the bolus which creates a continuous movement pushing the food. This movement of relaxation of the muscles is called peristalsis.

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15
Q

What is the lining of the stomach called and what is it made of?

A

The lining of the stomach is called the mucosa.
The mucosa is specialised for the secretion of gastric juice. Gastric glands are what secrete the gastric juice and are located in the mucosa’s narrow tube-like structures called gastric pits.

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16
Q

What is gastric juice and its function?

A

Gastric juice is a digestive juice containing hydrochloric acid, mucus and digestive enzymes. Each are secreted by different cells in the gastric pits. Gastric juice overall is responsible for the chemical digestion of food in the stomach.

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17
Q

What enzyme works in the stomach, and how is it formed?

A

Pepsin is an enzyme responsible for the chemical digestion of proteins, it breaks down proteins into peptides. Since the pH in the stomach is very low (~ 2 - 3), the acidic environment allows the enzyme pepsinogen to be converted into pepsin, an active form of the enzyme.

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18
Q

Why cannot food be absorbed straight into the blood from the stomach?

A

Because of the thick layer of mucus protecting the stomach from the acidic envrionment within.

19
Q

What substances can be absorbed into the stomach?

A

Alcohol and aspirin.

20
Q

What are the 3 layers of muscle found in the stomach and its benefit of having 3?

A
  • Longitudinal muscle
  • Circular muscle
  • Oblique muscle

This is good because the stomach can then contract in a variety of ways to churn the food and mix it with gastric juice.

21
Q

How does the stomach mechanically digest food?

A

Achieved by waves of muscular contractions that move along the stomach wall.

22
Q

What is the pyloric sphincter?

A

The sphincter prevents the stomach contents from falling into the small intestine unless pushed by peristalsis.

23
Q

What are the 3 parts of the small intestine?

A
  • Duodenum
  • Jejunum
  • Ileum
24
Q

What is the duodenum?

A

The duodenum is the top part of the small intestine and is connected to the stomach. The duodenum is where pancreatic juice and bile are ‘squirted into the chyme entering from the stomach.

25
Q

What is hydrogen carbonate good for in the pancreatic juice?

A

Hydrogen carbonate is an important component as it makes pancreatic juice alkaline. This is good so when the juice enters the chyme it neutralises the pH level preventing damage to the intestine lining and allowing enzymes to work at an optimal level.

26
Q

What 3 fluids partake in the digestion in the small intestine?

A
  • Pancreatic juice
  • Bile
  • Intestinal Juice
27
Q

What are the different enzymes in pancreatic juice and their functions?

A

Pancreatic juice is made up of:

  • Pancreatic Amylase: Breaks down starch into disaccharides.
  • Trypsin: Breaks proteins into peptides
  • Pancreatic Lipases: Lipids into fatty acids and glycerol
  • Ribonuclease and Deoxyribonuclease: Break DNA and RNA into nucleotides.
28
Q

What is the function of Bile and where does it come from?

A

Secreted into the small intestine from the liver, and is stored in the gall bladder. Bile salts are important for digesting and emulsifying fats, and breaking them into smaller droplets.

28
Q

What is the aim of mechanical digestion?

A

The aim is to break the food down into smaller pieces so that the total surface area increases, this allows for more effective chemical digestion as the chemicals can access more of the food.

29
Q

What enzymes are in intestinal juice?

A

Intestinal juice is made up of:

  • Peptidase: Breaking peptides into amino acids.
  • Intestinal amylase: Breaks down disaccharides into monosaccharides.
  • Intestinal Lipase: Breaks down lipids into fatty acids and glycerol.
30
Q

What is Segementation?

A

Process of mechanical digestion in the small intestine which has contraction of circular muscles to mix food with the digestive juices. To improve the mixing, the muscles relax and contract in a wave-like movement.

31
Q

What is the full chemical digestion of carbohydrates?

A

1st. Salivary glands contain enzymes that mix with the food to break starch into disaccharides.

2nd. After going through the stomach into the small intestine, the chyme mixes with pancreatic amylase which breaks more starch into disaccharides.

3rd. Then the intestinal amylase breaks the disaccharides into further monosaccharides.

32
Q

What is the full chemical digestion of proteins?

A

1st. The stomach contains pepsin which breaks proteins into polypeptides.

2nd. Then the pancreatic juice contains trypsin secreted into the small intestine which breaks polypeptides into peptides.

3rd. Then the intestinal peptides break the peptidase into amino acids.

33
Q

What is the full chemical digestion of lipids?

A

1st. The pancreatic lipase breaks the lipids into fatty acids and glycerol.

2nd. The intestinal lipase breaks the lipids into fatty acid and glycerol.

34
Q

What is the full chemical digestion of nucleic acid?

A

1st. The pancreatic juice contains ribonuclease and deoxyribonuclease which are both used to break DNA and RNA into nucleotides.

35
Q

Where does absorption take place and how does the small intestine achieve a large surface area?

A

In the wall of the small intestine requiring a large surface area.

The great surface area is achieved by:
- Having the small intestine be 6 meters long.
- Folds within the wall
- Villi
- Microvilli

36
Q

What are villi?

A

The villi is about 1 mm long, and are covered by a single layer of cells. Inside, there is a lymph capillary, called a lacteal, surrounded by a network of blood capillaries. The function is to absorb the nutrients into the bloodstream. Muscular movement of the intestinal wall further increases absorption as it moves the villi too, constantly bringing it into contact with intestinal contents.

37
Q

How do villi work?

A

Absorption occurs through active transport, involving energy, taking in nutrients against a concentration gradient. Some absorption occurs through simple diffusion, as there is a higher concentration of nutrient materials in the interior of the small intestine than in the cells in the villi.

38
Q

What nutrients are absorbed straight into the blood from villi?

A

Simple sugars
Amino acids
Water & water-soluble vitamins

These nutrients go from the blood to the liver.

39
Q

How are fatty acids and glycerol absorbed?

A

These recombine in cells of the villi to form fat and enter the lacteals.

These nutrients are carried into the lymph system and emptied into the blood through the veins.

40
Q

What is the large intestine?

A

The large intestine is about 1.5m long. It is made up of the caecum, colon, rectum, and anus.

41
Q

What occurs in the large intestine?

A
  • Most of the remaining water is absorbed
  • ## Bacteria in the large intestine breakdown the remaining compounds
42
Q

What is faeces?

A

The semi-solid material is left after water absorption and bacterial action.

Made up of:

  • Water
  • Undigested Food
  • Bacteria
  • Bile pigments which give the colour
  • Remaining intestinal cells
43
Q

How does faeces leave the body?

A

The faeces pass through the rectum and anus to the exterior.

Year 11 2023 (29 decks)

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