The Digestive System

?
Processing food: Organic molecules
Too large to be absorbed and must be broken down by digestion and absorbed in the gut
1 of 53
Processing food: The gut
Digestion and absorption take place here in a long, hollow, muscular tube
2 of 53
Processing food: Food passing through the gut
Food is processed as it passes along the regions of the gut
3 of 53
Processing food: How food moves along the gut
Food is propelled along by peristalsis
4 of 53
Peristalsis
Wave like contractions that happen in the oesophagus, stomach and intestines that act to propel food along
5 of 53
Functions of the gut: ingestion
Taking in of food in through the mouth
6 of 53
Functions of the gut: digestion - mechanical
Cutting or crushing action of the teeth, also rhythmical contractions of the gut wall. Increases surface are for enzymes to act on
7 of 53
Functions of the gut: digestion - chemical
Achieved through the secretion of digestive enzymes
8 of 53
Functions of the gut: absorption
Passage of digested food through the gut wall into the blood
9 of 53
Functions of the gut: egestion
Elimination from the body of food that cannot be digested
10 of 53
Mouth
Mechanical digestion through action of teeth. Salivary glands release enzymes to start chemical digestion
11 of 53
Oesophagus
Moves bolus of food from mouth to stomach by a series of rhythmic contractions called peristalsis
Several cells thick and protects the underlying tissues from damage when swallowing
12 of 53
Stomach
Mechanical digestion of food - rugae help (ridges). Gastric glands secrete hydrochloric acid and enzymes (chemical digestion)
Muscle layer is thick (3 different layers) to provide power to contract and relax
Lots of mucus produced
13 of 53
Pancreas
Produces pancreatic juice containing enzymes
14 of 53
Liver
Produces bile which helps emulsify fats and neutralise stomach acid
15 of 53
Duodenum
First part of the small intestine receiving food from the stomach and secretions from liver and pancreas
Villi (microscopic infolds) - increasing surface area
16 of 53
Ileum
Part of the small intestine which is responsible for the absorption of digested food
Villi (microscopic infolds) - increasing surface area
17 of 53
Large intestine - 4 parts
Divided into caecum, appendix, colon and rectum
18 of 53
Colon
Absorbs water, mineral, salts and vitamins (vitamin K and folic acid secreted by microbes in the gut)
Large number of mucous crypts to secrete mucus
19 of 53
Tissue layers of the gut wall: outer serosa
Layer of tough connective tissue, protects the wall of the gut, reduces friction from the other organs in the abdomen as the gut moves during the digestive process
20 of 53
Tissue layers of the gut wall: thick muscle layers
Muscle layer consists of 2 layers of muscle running in opposite directions (inner circular muscle and outer longitudinal muscle), these muscles cause peristalsis
21 of 53
Tissue layers of the gut wall: submucosa
Consists of connective tissue containing blood and lymph vessels to take away absorbed food products, as well as nerves that coordinate the muscular contractions in peristalsis
22 of 53
Tissue layers of the gut wall: mucosa
Innermost layer and lines the walls of the gut. Secretes mucus which lubricates and protects the mucosa. In some regions of the gut, this secretes digestive juices, in others it absorbs digested food
23 of 53
Endopeptidase
Catalyses the hydrolysis of some interior peptide bonds of a protein molecule
E.g. pepsin, trypsin & chymotrypsin
24 of 53
Exopeptidase
Catalyses the hydrolysis of a peptide bond linking the end amino acid in a peptide chain
E.g. carboxypeptidases & aminopeptidases
25 of 53
Carbohydrate --> enzymes, pH, substrate & products: mouth
Amylase, pH 7, Starch & Maltose
26 of 53
Carbohydrate --> enzymes, pH, substrate & products: duodenum
Amylase, pH 7, Starch & Maltose
27 of 53
Carbohydrate --> enzymes, pH, substrate & products: ileum
Lactase/Maltase/Sucrase, pH 8.5, Lactose/Maltose/Sucrose, Galactose/Glucose/Fructose
28 of 53
Protein --> enzymes, pH, substrate & products: stomach
Pepsin/Protease/Endopeptidase, pH 2, Proteins & Gastric juice/Polypeptides
29 of 53
Protein --> enzymes, pH, substrate & products: duodenum
Trypsin/Protease/Endopeptidase, pH 7, Proteins & Peptides/Polypeptides
30 of 53
Protein --> enzymes, pH, substrate & products: ileum
Endopeptidase/Exopeptidase/ Protease, pH 8.5, Proteins/ Polypeptides & Amino acids/Polypeptides
31 of 53
Lipid --> enzymes, pH, substrate & products: duodenum
Bile salts/Lipase, pH 7, Lipids & Fatty acids/Glycerol
32 of 53
Lipid --> enzymes, pH, substrate & products: ileum
Lipase, pH 8.5, Lipids & Fatty acids/Glycerol
33 of 53
Small intestine adaptations
Very long (about 6 m in length). Lining is folded/on the surface of the folds are villi/epithelial cells have microvilli - all increase surface area. Absorption occurs by diffusion, facilitated diffusion & active transport. Active transport requires ATP s
34 of 53
Small intestine - amino acid absorption & process
Amino acids are absorbed into epithelial cells by active transport. They move into the capillaries by facilitated diffusion.
The amino acids are water soluble so dissolve in the blood plasma
35 of 53
Small intestine - glucose & process
Glucose passes into the epithelial cells with sodium by co-transport. Sodium moves to the capillaries by facilitated diffusion. Both diffusion and facilitated diffusion are slow so not all glucose can be absorbed by this method, some is absorbed by active
36 of 53
Small intestine - fatty acid and glycerol absorption & process
Fatty acids and glycerol diffuse into the epithelial cells and then into lacteals.
Lacteals are part of the lymphatic system. The lymph system transports fat soluble molecules to the left subclavian vein near the heart
37 of 53
What is the function of bile?
Emulsifies lipids, neutralises the stomach and maintains a pH. It also increases the surface area
38 of 53
Why does each organ have a different pH in the digestive system?
Each enzyme has an optimum pH so each organ needs to have the correct pH for the enzyme
39 of 53
In which part of the digestive system is digested food absorbed into the circulation?
ileum
40 of 53
What are the 4 main functions of the gut?
ingestion, digestion, absorption, egestion
41 of 53
What is the pH of the stomach?
pH 2
42 of 53
What is contained with pancreatic fluid?
amylase, lipase, endopeptidase - trypsin
43 of 53
Where is protein digested?
stomach, duodenum, ileum
44 of 53
Where is starch digested?
mouth, duodenum, ileum
45 of 53
How is the wall of the ileum adapted for aborption?
very long, large surface area, villi, the lining is folded, microvilli, mitochondria - ATP
46 of 53
Small intestine - mineral and vitamin absorption
Minerals diffuse into the blood using diffusion, facilitated diffusion and active transport to dissolve into the plasma
Vitamins B and C are water soluble and are absorbed into the blood
Vitamins A, D and E are fat soluble and are absorbed into the lactea
47 of 53
Secretion of inactive precursors
Pepsin and trypsin are secreted in their inactive forms to prevent them from digesting tissues of the body
E.g. pancreas and stomach
48 of 53
Importance of emulsification of lipids
Increases surface area of lipids so increases rate at which they are digested by enzymes
49 of 53
The large intestine: length
About 1.5 m long
50 of 53
The large intestine: micro-organisms living in the colon - purpose
These bacteria are responsible for making vitamin K and folic acid
51 of 53
The large intestine: food state & contents
By the time it reaches the rectum, the food is in a semi solid state (containing undigested cellulose, bacteria and sloughed off cells)
52 of 53
Faecus (poo)
Semi solid material is expelled through the anus
53 of 53

Other cards in this set

Card 2

Front

Digestion and absorption take place here in a long, hollow, muscular tube

Back

Processing food: The gut

Card 3

Front

Food is processed as it passes along the regions of the gut

Back

Preview of the back of card 3

Card 4

Front

Food is propelled along by peristalsis

Back

Preview of the back of card 4

Card 5

Front

Wave like contractions that happen in the oesophagus, stomach and intestines that act to propel food along

Back

Preview of the back of card 5
View more cards

Comments

No comments have yet been made

Similar Science resources:

organs
See all Science resources »See all Key notes, definitions and processes of the digestive system resources »