Digestive system

Question 1

Role of the digestive system

Answer 1

The digestive system extracts nutrients from the food we eat and absorbs them into the body for use by the cells.

Question 2

6 activities that organs of the digestive system carry ouy

Answer 2

1. ingestion of food and water.
2. mechanical digestion of food and water.
3. chemical digestion of food and water.
4. movement along the alimentary canal.
5. absorption of digested food and water into the blood and lymph.
6. elimination of material that is not absorbed.

Question 3

Mechanical Digestion

Answer 3

• Physical process of breaking down of food particles into smaller pieces to increase the surface area.

Process occurs in the mouth, stomach and small intestine.

Process has 4 steps:
- Chewing
- Churning
- Segmentation
- Emulsification

Question 4

Chewing

Answer 4

• occurs in the mouth
• includes the teeth, tongue and cheek muscles.
• the teeth, incisors (bitting), canines (tearing), premolars and molars (crushing and grinding).
• The tongue and cheek muscles move the food bolus around ensuring that the food meets the teeth.

Question 5

Churning

Answer 5

• Occurs in the stomach
• The food bolus is exposed to stomach secretions
• Food can stay here for a number of hours being churned
• the stomach contains 3 layers of muscles, therefore it can contract in different directions
• the stomach is bounded by circular muscles, the lower oesophageal sphincter and the pyloric sphincter. these keep materials in the stomach until it is ready to be released via the pylorus into the small intestine.
• the resultant fluid is known as a thick, soupy consistency called chyme.

Question 6

Chemical digestion

Answer 6

Chemicals break down large, complex molecules into smaller, simpler molecules, small enough to be absorbed into the blood stream.

Carbohydrates get split up into monosaccharides, glucose, fructose and galactose.

proteins get split up into polypeptides and amino acids.

lipids get split up into fatty acids and glycerol.

nucleic acids are split into nucleotides.

Question 7

Alimentary canal

Answer 7

Continuous tube that runs from the mouth towards the anus.

The lining of the alimentary canal is the surface through which nutrients are absorbed.

With the help of organs and functions the alimentary canal makes up the digestive system.

Question 8

Orans throughout the alimentary canal

Answer 8

1. oral cavity
2. salivary glands
3. pharynx.
4. upper oesophageal sphincter
5. oesophagus
6. lower oesophageal sphincter
7. stomach
8. pylorus
9. pyloric sphincter
10. duodenum
11. jejunum (small intestine)
12. Ileum
13. appendix
14. caesium
15. ascending colon
16. transverse colon
17. descending colon
18. rectum
19. anus

Question 9

The mouth

Answer 9

Intake of food occurs here called ingestion.

Both chemical processes are occurred before food is swallowed.

Food is mechanically digested via the use of chewing, then the tongue shapes the food into a bolus. to swallow the tongue moves upwards and backwards pushing the food bolus towards the pharynx, where it meets the oesophagus.

Food is chemically digested via the mix with saliva ( a fluid secreted into the mouth by the three salivary glands), it contains mucus to lubricate the food and enzymes known as salivary amylase that being chemical digestion of carbohydrates (poly into di)

Question 10

The pharynx

Answer 10

Pharynx is used for the movement of the food bolus to the oesophagus, in has no contribution to digestion.

The tongue pushing food down voluntary.

The pharynx muscle movement in automatic due to reflexes.

If the pharynx contracts..
It block the nasopharynx
raises. the larynx allowing the epiglottis flap to cover the trachea.

the vocal chords are closed.

Question 11

The oesophagus layers

Answer 11

Outer layers of fibrous tissue
⬇️
Muscle layers (longitudinal)
⬇️
Muscle layers (circular)
⬇️
Submucosa
⬇️
Mucosa

Question 12

The oesophagus

Answer 12

Transports swallowed food from the mouth towards the stomach.

connects the pharynx to the stomach (approx. 25-30cm long)

Wall of the oesophagus has double layers of muscle like the alimentary canal.

Circular muscles have fibre arranged in a circle

longitudinal muscles have fibres arranged along the length of the canal

Question 13

Peristalsis (oesophagus)

Answer 13

Wave like muscle contraction that move food through a tube such as the oesophagus

In the oesophagus as food travels down the circular muscle behind it contracts to narrow the tube.

Question 14

Oesophageal sphincter.

Answer 14

A ring of smooth muscles that it located at the ends of the oesophagus.

This allows food to enter the stomach, as it is always contracted it prevents food from coming back from the stomach unless paristalisis is involved.

Question 15

The Stomach (Parts)

Answer 15

lower oesophageal sphincter
⬇️
body
⬇️
pylorus
⬇️
pyloric sphincter.

Question 16

The Stomach

Answer 16

The stomach is the part of the alimentary canal followed by the oesophagus.

Mechanical digestion occurs in the stomach through churning promoted by the movement of the oblique layer.

The stomach consists of 3 muscles layers, the circular, longitudinal and oblique. This allows the stomach to contract in different ways to churn the food inside, turning it into a thick, soupy liquid called chyme.

Question 17

Stomach lining

Answer 17

Also known as the gastric mucosa, is specialised for the secretion of gastric juices by gastric glands located in narrow tube like structures called gastric pits.

The lining of the stomach is protected from acid by a layer of mucus.

the acidic environment allows pepsinogen to convert to pepsin.

Pepsin is able to breakdown proteins into large polypeptides, nucleic acids, DNA and RNA.

Question 18

Gastric juices

Answer 18

digestive juice that contains HCL, mucus and digestive enzymes.

Each is secreted by a different cell in the gastric pit.

They are responsible for chemical digestion in the stomach, which mainly starts protein digestion.

Question 19

Gastric pit structure

Answer 19

TOP

gastric pit
⬇️
connective tissues in between
⬇️
cells the secrete mucus
⬇️
cells that secrete pepsinogen
⬇️
cells that secrete hydrochloric acid.

BOTTOM

Question 20

Stomach absorbance

Answer 20

Nutrients are not absorbed into the bloodstream through the stomach, because the internal surface is covered by a thick layer of mucus.

However, some alcohol and a few other drugs such as aspirin are absorbed.

Question 21

Pyloric sphincter

Answer 21

A thickening of circular muscle which connects the stomach and the small intestine.

The constriction is sufficient to prevent the stomach contents moving unless pushed along by peristalsis.

After 2-8 hours stomach contents are gradually pushed along into the small intestine.

Question 22

The small intestine parts

Answer 22

The duodenum
The jejunum
the Ileum

Question 23

Duodenum

Answer 23

:The first part of the small intestine

it is the shorted approx. 25cm.

Extends from the bottom end of he stomach in a curve around the pancreas.

Most chemical digestion occurs here

Question 24

Jejunum

Answer 24

The middle section of the small intestine.

The lining allows effective absorption of carbohydrates and proteins.

Question 25

Ileum

Answer 25

Final part of the small intestine. Vitamin B-12, bile salts, and remaining products of digestion are absorbed.

Question 26

Influences of digestion in the small intestine. (all the juices)

Answer 26

Pancreatic juice - secreted by the pancreas via the pancreatic duct. Bile - produced by the liver, stored in the gall bladder, via the hepatic duct. secreted into the small intestine via the common bile duct. Intestinal juice - secreted by glands in the lining of the small intestine.

Question 27

Pancreatic juice

Answer 27

Enters the duodenum through the common bile duct. It helps neutralise the acid that has come with the material from the stomach, and contains many enzymes required for digestion. pancreatic amylase- breaks down starch into maltose trypsin (pancreatic protease) - breaks down proteins into peptides. Pancreatic lipase - breaks down fats into fatty acid and glycerol ribonuclease and deoxyribonuclease - enzymes that digest RNA and DNA

Question 28

Bile

Answer 28

Secreted into the small intestine through the common bile duct. Doesn't contain digestive enzymes. They are important for the digestion of fats. they act like a detergent and emulsify the fat, breaking it into tiny droplets. Is mechanical digestion as it increases the surface area on which lipases can act to bring chemical digestion of fat.

Question 29

Intestinal juice

Answer 29

secretes from the wall of the small intestine. Contains enzymes that complete the digestion of carbohydrates, proteins and lipids. these include: - Peptidase - Sucrase, lactase and maltase - lipase.

Question 30

Absorbance of nutrients

Answer 30

After the process of digestion Nutrients are absorbed through the walls of the small intestine into the blood stream. They are absorbed efficiently, making them require a large surface area

Question 31

4 ways larger surface area is achieved for absorption

Answer 31

1. The small intestine is very long : 6-7 m long 2. The inner lining known as the mucosa has folds that extend into the interior of the small intestine 3. The mucosa has small finger line projections called villi that extend from the internal folded surface 4. The cells covering the outside of the villi have tiny projections from their external surfaces. These are called microvilli

Question 32

Villus (structure)

Answer 32

Top Microvilli ⬇️ Absorptive cell ⬇️ Secretory cell ⬇️ Veins ⬇️ Arteries ⬇️ Lacteal ⬇️ Lymph vessels Inside Each villus us covered by a single layer of cells Inside the villus is a lymph capillary known as a lacteal, which is surrounded by a network of blood capillaries.

Question 33

Villus (function)

Answer 33

Villi are small, finger-like projections that line the wall of the small intestine. Their primary function is to increase the surface area of the small intestine to maximise the absorption of nutrients from digested food into the bloodstream.

Question 34

Nutrient transport methods

Answer 34

Simple sugars such as glucose are absorbed by active transport. They pass through the cells on the outside of the villi and into the blood capillaries Amino acids are absorbed by active transport Into the blood capillaries Fatty acids and glycerol are absorbed by simple diffusion. In the cells of the villi fatty acids and glycerol recombine to form fat. The tiny droplets of fat enters the lacteals Water and water soluble vitamins are absorbed into the blood capillaries by diffusion (osmosis)

Question 35

The large intestine (parts)

Answer 35

Appendix ⬇️ Caecum ⬇️ Ascending colon ⬇️ Transverse colon ⬇️ Descending colon ⬇️ Rectum ⬇️ Anus

Question 36

Faeces

Answer 36

The semi solid material left after the water absorption and bacterial action makes up faeces. Faces contain water, indigested food (cellulose), bacteria, bile pigments (gives the colour), and the remains of cells that have been broken away from the alimentary canal They pass through the anus and rectum

Question 37

Diarrhoea

Answer 37

Diarrhoea is characterised by frequent defection of watery faeces. Caused by irritation of the small and large intestine, this increases peristalsis so that the contents of the intestine move before their is adequate water absorption. irritation - bacteria, virus, parasite, coeliac disease, lactose intolerant

Question 38

Constipation

Answer 38

- The movement of the large intestine are reduced and the contents remain there for a long period of time. - Water is absorbed, the faces become more dryer and harder. - may be caused by the lack of roughage (cellulose) in the diet. * roughage stimulates movement in the alimentary canal*

Question 39

Bowel cancer

Answer 39

Mass of cells that are able to divide uncontrollably, in the wall of the large intestine. caused by- high red meat consumptions and less fibre, also being overweight and physical inactivity.

Question 40

Lactose Intolerance

Answer 40

Where: Small intestine How: Body can’t digest lactose (sugar in milk) because it lacks the enzyme lactase. Cure: No full cure. Avoid milk or use lactose-free products and take lactase tablets.

Question 41

Coeliac Disease

Answer 41

Unable to tolerate protein called gluten, found in wheat and rye. immune system damages villi in the small intestine. nutrients cannot be absorbed without healthy villi. symptoms: muscle cramps, joint pain (nothing to do with nutrients), malnutrition. Is inherited. no cure, follow a low gluten free diet.

Question 42

How is absorption further enhanced from the villus

Answer 42

Absorption is further enhanced by the movement of the villi which is made by the muscular movement in the intestinal walls. This brings the villi in contact with different parts of the intestinal contents These contents are continuously changing as new material keeps entering the small intestine from the stomach The substances that are absorbed in the blood capillaries are carried by the hepatic portal vein to the liver. In the liver they may be removed or remain in the blood to he carried out to body cells The substances that are absorbed in the lacteals are transported to the lymph system, which empties into the blood through veins in the upper part of the chest.