Digestion Flashcards
What is the alimentary canal?
The alimentary canal is the journey your food takes from the mouth to the anus, as one long tube, except the liver and pancreas.
What happens in the mouth?
In the mouth, the food (or bolus) is mechanically chewed by the teeth, mechanically digesting it. Additionally, saliva, containing amylase, is secreted from the salivary glands, partially chemically digesting starch into maltose.
What happens in the oesophagus?
In the oesophagus, the bolus is transported from the mouth to the stomach due to peristalsis, the rhythmic contracting of the antagonistically-working muscle pair in the muscle lining of the oesophagus, squeezing food through it.
What happens in the salivary glands?
The salivary glands produce key enzymes (amylase) required for the chemical digestion of carbohydrates.
What happens in the liver?
The liver produces bile
What is another word for the oesophagus?
The gullet
What happens in the stomach?
The stomach contains hydrochloric acid, with a low acidic pH, to kill bacteria and create an optimum pH for enzyme action, such as the protease pepsin. It produces key enzymes.
What happens in the pancreas?
The pancreas produces the vast majority of digestive enzymes located in the body, such as amylase, lipase, trypsin, maltase and more.
What happens in the gall bladder?
Bile is stored from the liver until needed by the body. It send the needed bile to the small intestine and removes infected bile.
What happens in the small intestine?
In the small intestine, peristalsis takes place, as well as the secretion of bile, the chemical digestion of many large molecules, and the absorption of the small units of molecules.
What happens in the duodenum?
Enzymes, such as protease, lipase and amylase, do a lot of chemical digestion, as lipase breaks down lipids into fatty acids and glycerol. First part of small intestine
What happens in the ileum?
Digested food small molecules are absorbed into the bloodstream. Final part of small intestine
What happens in the large intestine?
Peristalsis
What happens in the colon?
First part of the large intestine. Faeces is formed here
What happens in the rectum?
Final part of the large intestine. Faeces is stored here.
What happens in the anus?
Faeces is egested.
What is the bolus?
It is the ball of food made in the mouth.
Bile description
Bile is a key part of the digestive system, but is NOT an enzyme - the liver does not produce digestive enzymes, the pancreas does. Bile is produced in the liver.
Bile function
Bile breaks down large fat droplets into smaller fat droplets for the enzymes to digest them (chemical digestion). It does not alter the fat droplets chemically, that is the role of the enzymes. The fat molecule STAYS THE SAME, it is the droplet size that CHANGES. This process is known as EMULSIFICATION. It also neutralises the low pH in the small intestine (due to hydrochloric acid) in order to create an environment of optimum pH for enzymes.
Ingestion
The intake of substances (food/drink) into the body through the mouth
Digestion
The breakdown of large, insoluble food molecules into small water-soluble molecules using mechanical or chemical processes
Absorption
Movement of digested food molecules across the wall of the intestine in the blood or lymph
Assimilation
Movement of digested food molecules into the cells where they are used, becoming art of the cells (includes uptake and use of food molecules by cells).
Egestion
Passing out of undigested food as faeces, through the anus. Undigested food is the food that cannot be digested.
Excretion
Disposal of waste products made by the body (ie. sweat, urine)
Flowchart of starch chemical digestion
Starch -(Amylase)-> Maltose -(Maltase)-> Glucose
Peristalsis
In the small intestine or oesophagus, the lining is covered in tiny hairs, known as cilia, that help push the bolus down. Additionally, the antagonistic pairs of muscles, known as the circular and longitudinal muscles, push down the bolus through the peristaltic squeeze. When the longitudinal muscles contract, the length of the tube shortens, while the circular muscles relax. When the circular muscles contract, the diameter or width of the tube decreases, and the longitudinal muscles relax. They work together by doing opposite things.
Absorption in the ileum
In the ileum, small food molecules are transported by peristalsis. Then, enzymes break down the remaining bonds between the molecules, leaving the food molecules. These are then small enough to move from the ileum to the blood capillaries, through the ileum lining, through diffusion.
Efficient Absorption in the Vili
- The vili, located on the ileum lining, are covered with microvilli, increase surface area for diffusion.
- The thin walls of the vili, being 1 cell thick, decrease the diffusion distance of the food molecules.
- The network of capillaries, with flowing blood, maintains the concentration gradient.
- The lacteal absorb fat instead of letting it go to the blood.
Sodium Mineral
- Found in bodily fluids (eg. blood)
- Sourced from common salt, rice, pasta, olives, tomato juice, celery, cheese
Chlorine mineral
- Found in bodily fluids (eg. blood)
- Sourced from common salt, cheese, cured meat, pasta, celery, seaweed
Calcium mineral
- Makes teeth and bones
- Sourced from milk, cheese, nuts, tofu, broccoli, soya beans, salmon
Phosphorus mineral
- Makes teeth and needed for function of the cells
- Sourced from meat, poultry, fish, nuts, beans, dairy, soy, lentils
Iron mineral
- Part of haemoglobin in red blood cells, helping in the carrying of oxygen
- Sourced from liver, red meat, beans, nuts, dried fruit, eggs
Rickets
This is a condition affecting bone development in children. This leads to bone pain, poor growth, and soft, weak bones that can lead to bone deformities. This is caused by a lack of Vitamin D, calcium and phosphorus.
Anaemia
This is caused by iron deficiency. It is the condition of having not enough red blood cells or haemoglobin for transportation of oxygen. This can cause fatigue, headache, yellow skin, irregular heart beat, chest pain, leg cramps or insomnia.
Carbohydrate source and use
Body’s main fuel
Source of bread, pasta, or rice
Starch
This is a very large, insoluble molecule. It becomes water-soluble and small after digestion. Examples include potato or rice. It is how plants store glucose not needed immediately after respiration. It is a chain of glucose molecules bonded together, as a polymer.
Cellulose
This is found in cell walls of plants. It is a type of fibre, preventing constipation, and diseases such as bowel cancer. However, it cannot be digested, as we do not have the right enzymes.
Glycogen
This is a polymer of glucose, and is how animals store glucose not needed immediately after respiration, stored in the liver and muscles.
Monosaccharides or monomers
The simplest carbohydrate molecule. This can be glucose or fructose (found in fruits).
Disaccharides
These are two monosaccharides bonded together. These include lactose (found in dairy products), and sucrose (table sugar, made of glucose and fructose).
What are animal fats?
They are fats that are solid at room temperature (eg. cheese)
What are plant fats?
These are fats that are liquid at room temperature (eg. oil).
Lipids
Lipids are a long-term store of energy, and are used as insulators or shock absorbers for vital organs. They are made up of a carboxyl group and a hydrocarbon chain (1 glycerol molecule and 3 fatty acid chains).
What is a saturated fat?
A saturated has no double bond in its fatty acid chain, meaning it is less healthy. Examples include cholesterol.
What is an unsaturated fat?
This is a fat with a double bond in its fatty acid chain, making it healthier. Examples include avocado, olive or nuts.
Lipid Vs Carbs
- Both are made up of carbon, oxygen and hydrogen
- Carbohydrates have polymers, while lipids are non-polymeric
- Lipids are chains, while carbs have a ring shape
What makes up the majority of the body?
Water, then protein
What is the role of proteins?
Proteins are needed for growth and repair of damaged or old tissues.
What is a protein?
A protein is a polymer made up of chains of animo acids, held together by bonds, and, when broken down, these can be absorbed into the bloodstream. There are 20 types of animo acids.
Sources of protein
Meat, fish, cheese, egg, peas, nuts, beans
Examples of protein
Haemoglobin, hair, nails, enzymes, collagen, keratin
Importance of protein shape
- determined by what amino acids are in the chain
- determines its function
Kwashiorkor
This is malnutrition due to severe protein deficiency. This causes fluid detention and a swollen or distended abdomen.
Vitamin A
- Makes a chemical in the retina, and protects the surface of the eye, treating eye disorders or skin infection
- Fish liver oils, liver, butter, margarine, carrots
Vitamin B9
- Reduces risk of neural tube defects during pregnancy
- Eggs, nuts, edamame, lentils, mango, orange
Vitamin B12
- Provides relief from symptoms of anaemia, kidney and liver disorders
- Oyster, yoghurt, salmon, milk, liver, chicken, mussels
Vitamin C
- Sticks together cell lining surfaces such as the mouth, helps treat scurvy and common colds
- Bell pepper, kale, broccoli, kiwi, orange, potato
Vitamin D
- Helps bones absorb calcium and phosphate, aiding in treating arthritis, tooth decay, diabetes, and rickets
- Fish liver oils, sunlight, egg yolk, mushroom, tuna, spinach
Body mass percentages
Water - 60%
Protein - 18%
Lipids - 10%
Carbohydrate - 1%
Role of vitamins:
- boost immune system
- support normal growth and development
- helps cells and organs
Fibre
- keeps digestive system healthy, bulking agent, removes waste, improves metabolism pr heart
- fruits, vegetables, grains, beans, peas, lentils, oats, cereals
Water role
- maintain body temperature
- cucumber, tomato, apple, watermelon, celery, lettuce
Coeliac disease
- causes small intestine to become inflamed and unable to absorb nutrients, due to an adverse reaction to gluten
- symtoms are diarrhoea, abdominal pain, bloating, and these disappear when gluten is removed from the diet
Constipation
- the stools remains too long in the colon, too much water is absorbed from it, and it becomes hard and dry
- symptoms are dry, hard or lumpy stool, bloated or nausea, stomachache or cramps, hard to pass stool
Crohn’s Disease
- inflammation of the lining of the digestive system, acute kidney failure
- abdominal pain or cramps, chronic diarrhoea, rectal bleeding, mouth ulcers or gum pain, fever and fatigue
Lactose intolerance
- low levels of lactase made, lactose malabsorption
- symptoms include nausea or vomiting, diarrhoea, intestinal gas, and stomach bloating
