7.2, 7.3, 7.4, 7.5 Flashcards
What 6 stages does the food go through in the alimentary canal?
Ingestion
Mechanical digestion
Chemical digestion
Absorption
Assimilation
Egestion
Ingestion definition
the taking of substances, e.g. food and drink, into the body through the mouth
Mechanical digestion definition
the breakdown of food into smaller pieces without chemical change to the food molecules
Chemical digestion definition
the breakdown of large, insoluble molecules into small, soluble molecules
Absorption definition
the movement of nutrients from the intestines into the blood
Assimilation definition
uptake and use of nutrients by cells
Egestion definition
the removal of undigested food from the body as faeces
Function of mouth
the mouth is where mechanical digestion takes place - teeth chew food to break it into smaller pieces and increase it’s surface area to volume ratio
Function of salivary glands
- amylase enzymes in saliva start digesting starch into maltose
- the food is shaped into a bolus (ball) by the tongue and lubricated in saliva so it can be swallowed easily
Function of the oesophagus
- tube that connects the mouth to the stomach where the food bolus goes after being swallowed
- wave - like contractions called peristalsis will take place to push the food bolus down without relying on gravity
Function of stomach
food is mechanically digested by churning actions while protease enzymes start to chemically digest proteins
What is present in the stomach and what does it help?
hydrochloric acid is present to
1. kill bacteria in food and
2. provide the optimum ph for protease enzymes to work
What is the first section of the small intestine called and what is its function?
first section is called the duodenum and is where the food coming out of the stomach finishes being digested by enzymes produced here and also secreted from the pancreas
What is the pH of the small intestine
ph of the small intestine is slightly alkaline - around ph 8 - 9
What is the second section of the small intestine called and what is its function?
second section is called the ileum and is where absorption of digested food molecules takes place
What are some of the adaptations of the ileum?
Thin – digested food doesn’t have to travel far to reach the blood.
Large surface area – due to being long and folded aids in faser absorption
What is the function of the large intestine?
water is absorbed from remaining material in the colon to produce faeces
faeces is stored in the rectum and removed through the anus
What is the function of the pancreas?
produces all three types of digestive enzyme: amylase, protease and lipase
secretes enzymes in an alkaline fluid into the duodenum for digestion to raise ph of fluid coming out of the stomach
What is the function of the liver?
produces bile to emulsify fats (break large droplets into smaller droplets) -
What is the function of the gall bladder?
stores bile to release into the duodenum as required
What are the main examples of mechanical digestion? (3)
It is mainly carried out by the chewing action of the teeth,
the churning action of the stomach and
the emulsification of fats by bile in the duodenum
Where are teeth held?
Teeth are held firmly in the bone of the jaw
What are teeth used for?
used for chewing to increase the surface area of the food so that it can be exposed to saliva and other digestive juices and broken down more quickly
What do the different sizes of teeth allow them to do?
The differing shapes and sizes of teeth enable them to perform slightly different functions
What are the 4 main types of teeth?
incisors
canines
premolars
molars
Function of incisors
chisel-shaped for biting and cutting
Function of canines
pointed for tearing, holding and biting
Function of premolars and molars
larger, flat surfaces with ridges at the edges for chewing and grinding up food
What is the purpose of digestion?
The purpose of digestion is to break down large, insoluble molecules (carbohydrates, proteins and lipids) into small, soluble molecules that can be absorbed into the bloodstream
Why is food partially digested mechanically?
Food is partially digested mechanically (by chewing, churning and emulsification) in order to break large pieces of food into smaller pieces of food which increases the surface area for enzymes to work on
In what way does digestion take place mainly? How does this work?
Digestion mainly takes place chemically, where bonds holding the large molecules together are broken to make smaller and smaller molecules
What are the main types of digestive enzymes?
carbohydrases, proteases and lipases
Where is amylase produced?
Amylases are produced in the mouth (salivary gland) and the pancreas
Where are amylases secreted into
The mouth and the duodenum
What does amylase digest?
digests starch to maltose
What is maltose digested by? What is it converted to?
Maltose is digested by the enzyme maltase into glucose
Where is maltose digested?
on the membranes of the epithelium lining the small intestine
What are proteases?
Proteases are a group of enzymes that break down proteins into amino acids in the stomach and small intestine
Where does protein digestion take place?
Protein digestion takes place in the stomach and duodenum
What are the two types of proteases?
Pepsin and trypsin
Where is pepsin produced?
in the stomach
Where is trypsin produced and where is it secreted into?
Trypsin is produced in the pancreas and secreted into the duodenum
Where are lipase enzymes produced and where are they secreted into?
Lipase enzymes are produced in the pancreas and secreted into the duodenum
What do lipases digest?
They digest lipids into fatty acids and glycerol
What is the gastric juice?
The stomach produces several fluids which together are known as gastric juice
How does HCl in the stomach kill bacteria?
The low pH kills bacteria in food that we have ingested as it denatures the enzymes in their cells,
What is pepsin’s optimum ph?
around pH 2
What does the HCl ensure in relation to pepsin?
The hydrochloric acid produced in the stomach ensures that conditions in the stomach remain within the optimum range for pepsin to work at its fastest rate
What are the 2 main roles of bile?
It is alkaline to neutralise the hydrochloric acid which comes from the stomach
It breaks down large drops of fat into smaller ones. This is known as emulsification.
What is the difference between the enzymes in the stomach and in the small intestine?
The enzymes in the small intestine have a higher (more alkaline) optimum pH than those in the stomach
How is emulsification beneficial?
The larger surface area allows lipase to chemically break down the lipid into glycerol and fatty acids faster
Is emulsification a chemical or physical process?
This is an example of MECHANICAL DIGESTION, not chemical digestion – breaking something into smaller pieces does not break bonds or change the chemical structure of the molecules which make it up, which is the definition of chemical digestion.
Where is water absorbed?
Water is absorbed in both the small intestine and the colon, but most absorption of water also happens in the small intestine
Where does absorption take place?
Absorption takes place in the second section of the small intestine, the ileum
What adaptations does the ileum have?
The ileum is adapted for absorption as it is very long and has a highly folded surface with millions of villi (tiny, finger like projections)
How do the ileum’s adaptations help with absorption?
These adaptations massively increase the surface area of the ileum, allowing absorption to take place faster and more efficiently
What are (briefly) the 4 adaptations that a villus has?
have microvilli
thin wall of villus
connected to a network of blood capillaries
How do microvilli help the villus with its function?
Microvilli on the surface of the villus further increase surface area for faster absorption of nutrients
How does the wall being thin help the villus with its function?
Wall of villus is one cell thick meaning that there is only a short distance for absorption to happen by diffusion and active transport
How does the villus being connected to a network of blood vessels help the villus with its function?
Well supplied with a network of blood capillaries that transport glucose and amino acids away from the small intestine in the blood
(creates a conc. gradient)
structure of teeth contain
enamel, dentine, pulp, nerves, blood vessels and cement,
