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Human Biology ATAR > Digestive System > Flashcards

Digestive System Flashcards

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1
Q

What are the six basic activities of the digestive system

A
  1. Ingestion of food and water
  2. Mechanical digestion of food
  3. Chemical digestion of food
  4. Movement of food along the alimentary canal
  5. Absorption of digested food and water in the blood and lymph
  6. Elimination of material that is not absorbed
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2
Q

The 2 types of digestion

A

Mechanical digestion

Chemical Digestion

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3
Q

What is mechanical digestion and what does it involve?

A

It is the physical breakdown of food particles.
This aim of mech digestion is to break down food into smaller pieces so that the total surface area increases, allowing more effective chemical digestion.
Involves:
- Teeth cutting, tearing and grinding the food.
- Churning action in the stomach to break down the food further.
- Gall bladder releases bile into the small intestine. Bile salts act as emulsifying agents, breaking fat down into smaller droplets.

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4
Q

What is Chemical digestion?

A

Use of chemical means to break down larger molecules into smaller molecules.
Enzymes are mainly used in this digestion as they are biological catalysts (chemicals that are able to increase the rate of a reaction without being consumed).

Enzymes throughout the digestive system:

  • Saliva (mouth
  • Stomach
  • Small intestine
  • Carbohydrates split into monosaccharides such as glucose, fructose and galactose.
  • Proteins are split into peptides and amino acids.
  • Lipids are split into fatty acids and glycerol.
  • Nucleic acids are split into nucleotides.
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5
Q

Functions of the digestive system

A
  • Ingest (receive) food
  • Digest food - mechanical and chemical
  • Moves the food along the gastrointestinal (GI) tract.
  • Absorb food (molecules) into blood and lymph
  • Egest (remove) material that are not absorbed
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6
Q

What is the alimentary canal?

A

It is a continuous tube that runs from the mouth to the anus.
The lining of this canal is the surface through which nutrients are absorbed.

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7
Q

What is mastication?

A

The process of food being chewed.

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8
Q

What is the chemical digestion in the mouth?

A

Contains mucus to lubricate the food and digestive enzyme (SALIVARY AMYLASE), this enzyme begins the chemical digestion of starch into the disaccharide maltose.

Buffers neutralise acids to prevent tooth decay.

Antibacterial chemicals kill bacteria that enter the mouth with food

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9
Q

What is the mechanical digestion in the mouth?

A

The teeth, of which there are four of.

  • Four incisors - used for biting and cutting
  • two canines - conical teeth used for tearing
  • Four premolars
  • Six molars - used for crushing and grinding food
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10
Q

What is a bolus?

A

A small rounded mass of a substance, in this case of chewed food at the moment of swallowing.

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11
Q

What is the Oesophagus

A

It is a tube that connects the pharynx to the stomach.

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12
Q

What muscles is the oesophagus made of?

A

It have a double layer of muscle consisting of:

  • Circular muscle: muscle fibres arranged in a circle.
  • Longitudinal Muscle: muscle fibres arranged along the length of the canal
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13
Q

What is an epiglottis?

A

It is a flap of cartilage that closes the trachea (windpipe) when swallowing.

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14
Q

How does the bolus move down the oesophagus?

A

The circular muscle contracts behind the food entering the pharynx & oesophagus.
With this contraction the constriction of the muscle move in a wave: Peristalsis.
With that movement, the food is pushed in front of it.
Throughout this adventure of the bolus, it is lubricated by the mucus in the inner lining.

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15
Q

What are the layers of the GI tract?

A

Inner layer (Mucosa)
Submucosal
Double layer of muscle ( Longitudinal and circular)
Serosa

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16
Q

What is the mechanical digestion of the stomach?

A

Waves of muscular contraction move along the stomach wall. Contracting in a variety of ways to churn the food and mix it with the stomach juices until the food converts into a thick, soupy liquid; known as chyme.

Digestion of lipids, proteins and carbohydrates

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17
Q

What layers does the stomach have?

A

1.serosa.
2.musclaris.
(An oblique muscle layer, circular and 3.longitudinal layer.)
4.submuscosa.
5.mucosa
(gastric glands, muscularis mucosa)

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18
Q

What is gastric juice and what is it responsible for?

A

It is a digestive juice that contains hydrochloric acid, mucus and digestive enzymes.
It is responsible for the chemical digestion (mainly protein digestion) in the stomach.

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19
Q

What is the pH of the stomach?

A

2-3

20
Q

What is pepsin?

A

It is the converted enzyme from pepsinogen, becoming an active form of the enzyme.
It is able to break proteins down into shorter peptides; polypeptides. Breaks down nucleic acids DNA and RNA

21
Q

Why is the internal surface of the stomach is cover by a thick layer of mucus?

A

This is so that nutrients are not able to be absorbed into the bloodstream, also so the stomach acids dont eat through the stomach lineing

22
Q

What is the pyloric sphincter?

A

It’s a circular muscle constriction. This prevents contents from moving through unless being pushed by peristalsis.
- 2-8 hours, stomach contents are gradually pushed to the next area of the alimentary canal - the small intestine.

23
Q

What are uclers?

A

Caused by bacterial infection of the stomach

  • H.pylori bacteria (a bacteria that infect your stomach (wOw))
  • Now cured with antibiotics

was once THOUGHT to be caused by stress
- Tried to control with antacids (corrects the acidity in the stomach)

24
Q

What does the pancreas do?

A

It produces and secretes pancreatic juice into the small intestine, containing enzymes:

  • Proteases: trypsin, chymotrypsin
  • Amylase
  • Lipase

Also produces buffers to neutralise the acid from the stomach.

25
Q

What does the liver do?

A
  1. Amino acids to glucose (gluconeogenesis)
  2. Metabolism of fat (production of lipid from excess glucose)
  3. Synthesis of triglycerides (from the breakdown of lipids)
  4. Synthesis and regulation of cholesterol
  5. Deamination (removal o amino group)/ Transamination (convert one amino acid to another) / urea formation (linked dot deamination)
  6. Production of bile (from breakdown of haemoglobin)
  7. Detoxification (eg. metabolising alcohol)
  8. Heat production
26
Q

What are the 3 regions of the small intestine?

A
  1. Duodenum
  2. Jejunum
  3. Ileum
27
Q

What is the duodenum?

A

It is the 1st part of the intestine. Extends from the bottom end of the stomach, curving around the pancreas. Most of the chemical digestion occurs here before the chyme moves along.

28
Q

What is the Jejunum?

A

Middle section. The lining of the walls allows for the effective absorption of carbohydrates and proteins.

29
Q

What is the Ileum?

A

Final area. Vitamin B12, bile salts and the remaining products of digestion are absorbed.

30
Q

What is the mechanical digestion of the small intestine?

A
  • Mixes by segmentation (peristalsis)

- Bile emulsifies fats

31
Q

Why does digestion occur in the small intestine?

A
  • Pancreatic Juice is secreted by the pancreas via the pancreatic duct.
  • Bile: produced by the liver, but stored in the gall bladder and secreted into the SI via the bile duct.
  • Intestinal Juice: secreted by glands in the lining of the small intestine.
32
Q

Why is villi and microvilli shaped the way they are?

A

Increases surface area for absorption.

33
Q

What is pancreatic juice and where does it come from?

A

Enters the duodenum through the common bile duct.
Helps to neutralise the acid that came with the material from the stomach.
Contains many enzymes involved in digestion of food.

34
Q

What enzymes does pancreatic juice contain?

A

Pancreatic Amylase - Breaks down starch into disaccharide maltose.
Trypsin (pancreatic protease) - Splits proteins into peptides.
Pancreatic Lipases - Break down fats into fatty acids and glycerol.
Ribnuclease & deoxyribonuclease - Digests RNA & DNA

35
Q

What is bile, where is it stored and released, how much of it is made each day?

A

It’s the secretion of the liver, stored in the gall bladder and released into the small intestine.
600-1000mL is produced by the liver each day.

36
Q

What do bile salts do?

A

(Important to mechanical digestion)

Acts like a detergent and emulsifiers the fat, breaking it into tiny droplets.

37
Q

What is the mechanical digestion of bile?

A

It increase the surface area on which the lipases can act to bring about the chemical digestion of fat.

38
Q

What enzymes does the intestinal juice contain and why?

A

To complete the digestion of carbohydrates, proteins and lipids.

  • Peptidase - breaks down peptides into amino acids.
  • Sucrase, lactase & maltase - breaks down sucrose, lactose & maltose into monosaccharides; glucose, fructose and galactose.
  • Lipases - breaks down lipids into fatty acids and glycerol.
39
Q

What is segmentation?

A

It is a process that occurs in the small intestine using the contractions of circular muscles to push the chyme into segments, mixing it with digestive juices.

40
Q

How long is the small intestine and why is it that long?

A

6-7m
The absorption of nutrients requires a large internal surface area.
Cells covering the outside of the villi have microscopic projections from their external surfaces known as microvilli.

41
Q

What are the functions of the large intestine?

A
  • Water absorption
  • Bacteria break down remaining organic molecules, which produce gases.
  • Food may stay in there for 18-24 hours.
42
Q

What is the structure of the large intestine?

A
  • 1.5m long
  • Wider than the small intestine
  • Contains caecum
43
Q

What are the functions of the colon?

A

Re-absorbs water

  • Uses 9 litres of water in everyday digestive juices.
    • Must reabsorb water or you’d die of dehydration.
  • > 90% of water reabsorbed.
  • Water is reabsorbed by osmosis
44
Q

What happens is there is not enough water reabsorbed by the colon?

A

Diarrhoea

Can be fatal

45
Q

What happens if too much water is reabsorbed by the colon?

A

Constipation

46
Q

What bacteria lives in the large intestine?

A

Escherichia coli (E. coli)

  • Digests cellulose
    • Digests fruits and vegetables
  • Produce vitamins
    • Vitamin K and B vitamins
  • BUT generates gases
    • By-product of bacterial metabolism
    • Methane, hydrogen sulfide.
47
Q

What is left after digestion?

A

Faeces consist of:

  • Water
  • Undigested food materials
  • Bacteria
  • Bile pigments
  • Cell remains from intestinal walls

Human Biology ATAR (25 decks)

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