Digestion Flashcards
mechanical digestion
Mechanical digestion involves breaking up large pieces of food into smaller, usually insoluble pieces
mechanical digestion is important or teeth
- It gives the pieces of food a larger surface area for digestive enzymes to act on, making chemical digestion quicker and easier.
- It makes food easier to swallow.
incisor
Chisel-shaped with sharp, thin edges
At the front of the jaw.
To cut food.To bite off pieces of food.
canines
Next to the incisors.
Cone-shaped and pointed.
To grip food. To tear off pieces of food.
Pre molars
At the side of the jaw next
to the canines.
Havea fairly broad surface with two pointed cusps.
To crush and grind food.
Molars
At the back of the jaw next
to the premolars.
Have a broad surface with 4 or 5 pointed cusps.
To crush and grind food.
enamel
non-living. Covers the crown of the tooth. The hardest substance in the body. Resistant to chipping and relatively resistant to decay; however, it can be dissolved by acid produced by bacteria inthe mouth. Protects the tooth
dentine
bone-like. Contains channels of living cytoplasm from cells in the pulp cavity.
Forms the bulk of the tooth
pulp cavity
composed of living cells and blood vessels
blood vessels
supply the living cells with food and oxygen,and remove carbon dioxide and waste
gum
jawbone
nerves
senstive, in tooth decay, when the enamel and entine rot away, exposes nerves to the outisde
cement
covers the root of the tooth, bone-like
fibres
embedded in the cement at one end and the jawbone at the other end. Anchor the tooth in the jawbone and allows light movement for shock absorption
bolus
When chewing is complete, the food is rolled into a ball called a bolus. The bolus is pushed to theback of the mouth by the tongue and swallowed. It enters the stomach where contractions of the muscles in the stomach walls churn the food which continues the process of mechanical digestion.
Chemical digestion
Chemical digestion involves breaking down large, usually insoluble, food molecules into small, soluble food molecules by hydrolysis.
gall bladder –
stores bile
bile duct
provides the passage for bile from the gall bladder to enter into the duodenum
anal sphincter
– a muscle which relaxes
during egestion
pyloric sphincter –
–a muscle whichrelaxes periodically to release food from the stomach
salivary gland
produces saliva
mouth
digestion of starch
epiglottis
closes over the trachea during swallowing
oesophagus
transports food to the stomach, food moves down this muscular tube (of longitudinal and circular muscles) by a reflex/non-voluntary action called peristalsis
stomach
– produces gastric juice. Digestion of proteins begins
caecum and appendix
no function in humans
colon
absorbs water
rectum
stores faeces for egestion
small intestine
receives bile and pancreatic juice. Produces intestinal juice. Digestion of starch, maltose, sucrose, lactose,
lipids, proteins and peptides is completed. Products of digestion are absorbed
duodenum
ileum
Mouth
Saliva
Salivary glands.
*Water and mucus
* Salivary amylase
** Moisten and lubricate the food allowing tasting and easy swallowing.
* Begins to digest: starch TO maltose
Stomach
Gastric juice
Cells in the stomach wall.
* Hydrochloric acid*
Rennin*
* Pepsin*
- Maintains an optimum pH of 1–2 for pepsin and rennin, and kills bacteria.
- Produced in infants (renin) to clot soluble protein in milk so the protein is retained in thestomach.
- Begins to digest:protein TO peptides (shorter chains of amino acids)
Small
intestine
(duodenum
and ileum)
Bile
Cells in the liver.
It is stored in the gall bladder and enters the duodenum via
the bile duct.
* Bile pigments, e.g. bilirubin* Organic bile salts
- Bile pigments Excretory products from the breakdown of haemoglobin in the liver. Have no function indigestion.
- Organic bile slats Emulsify lipids, i.e. break large lipid droplets into smaller droplets increasing their surface area for digestion
Pancreatic
juice
Cells in the
pancreas. It
enters the
duodenum via
the pancreatic
duct.
- Pancreatic
amylase* - Trypsin*
- Pancreatic
lipase* - Continues to digest: starch TO maltose*
Continues to digest: protein TO peptides*
Digests: lipids TO fatty acids andglycerol
Intestinal juice
Cells in the walls
of the small
intestine.
* Maltase*
* Sucrase*
* Lactase*
* Peptidase* (erepsin)
Digests:
maltose TO glucose
Digests:
sucrose TO glucose and fructose*
Digests:
lactose glucose and galactose*
Digests:
peptides amino acids
PERISTALSIS
circular muscles – in the walls of the oesophagus and intestines
circular muscles contract behind the bolus, squeezing it along
bolus of food
circular muscles relax around and
in front of the bolus
Absorption of the products of digestion
occur in the small intestine and colon
ABSORPTION OF THE SMALL INTESTINE
The products of digestion are absorbed through the lining of the small intestine, mainly theileum, and into the blood vessels and lymphatic vessels in its walls. Substances absorbed includemonosaccharides, amino acids, fatty acids, glycerol, vitamins, minerals and water
The ileum is adapted to absorb food as efficiently as possible:
Absorption occurs by both diffusion and active transport.
- It is very long, about 5 m in an adult. This provides a large surface area for rapid absorption.
- Its inner surface has thousands of finger-like projections known asvilli (singular villus). These greatly increase the surface area for absorption.
- Each villus has a network of blood capillaries and a lacteal inside. These provide means of rapidly transporting the products of digestion away from the ileum.
- The wall of each villus, known as the epithelium, is onlyone cell thick. Digested food can passrapidly through this epithelium into the capillaries and lacteal. * ‘
- The epithelial cells have tiny projections called microvilli. These further increase thesurface area for absorption.
Absorption in the colon
Any food that is not digested in the small intestine passes into the colon where water and mineral salts are absorbed from it.
As this undigested waste moves along the colon to the rectum it becomesprogressively more solid as the water is absorbed.
Egestion
The almost solid material entering the rectum is called faeces and consists of undigested dietary fibre, dead bacteria and intestinal cells, mucus and bile pigments. Faeces is stored in the rectum and egested at intervals through the anus when the anal sphincter relaxes.
control of blood glucose levels (homeostasis)
Two hormones, secreted directly into the blood by the pancreas, are responsible for keeping blood glucose levels constant.
These are insulin and glucagon. Regulation of blood glucose levels is one aspect of homeostasis, i.e. the maintenance of a constant internal environment.
- If the blood glucose level rises, e.g. after a meal rich in carbohydrates, the pancreas secretes insulinwhich stimulates body cells to absorb glucose for respiration and the liver cells to convert excess glucose to glycogen.
- If the blood glucose level falls, e.g. between meals, or during exercise or sleep, the pancreas secretes glucagon which stimulates the liver cells to convert glycogen toglucose which enters the blood.
Vit A
Liver, cod liver oil,
yellow and orange
vegetables and
fruits
- Helps to keep the skin, cornea and mucous membranes healthy.
- Helps vision in dim light
(night vision). - Strengthens the immune system.
Dry, unhealthy skin and cornea.* Increased susceptibility toinfection. * Reduced vision at night orcomplete night blindness
Vit B1
Whole-grain cereals
and bread, brown
rice, peas, beans,
nuts, yeast extract,
lean pork.
Aids in respiration to produce energy. * Important for the proper functioning of thenervous system.
Beri-beri: weakness and pain in the limb muscles, difficulty walking, nervous system disorders, paralysis.
Vit C
citrus fruits, raw
green vegetables.
- Keeps tissues healthy, especially the skin andconnective tissue.
- Strengthens the immune system.
- Scurvy: swollen and bleeding gums, loose teeth or loss of teeth, red-blue spots on the skin, muscle and joint pain, wounds do not heal. * Increased susceptibility toinfection
VItamin D
Oily fish, eggs, cod
liver oil.
Made in the body by
the action of sunlight
on the skin.
- Promotes the absorptionof calcium and phosphorus in the ileum.
- Helps build and maintain strong bones and teeth.
- Strengthens the immune system.
- Rickets in children: soft, weak, painful, deformed bones, especially limb bones, bow legs.
- Osteomalacia in adults: soft, weak, painful bones that fracture easily, weakness of limb muscles.* Poorteeth
surplus of vitamin a
can occur when taking supplemnts
cause liver damage, jaundice, itchy skin, cracked fingernails, blurryvision, nausea, headaches and fatigue.
surplus of vit d
cause high levels of calcium in the blood, excessive thirst and urination, loss of appetite, nausea, vomiting, calcification of soft tissues, e.g. kidneys, lungs and inside blood vessels, and the development of kidney stones
minerals micronutrients bc they are inroganic and humans only require a samll amount for healthy growth and development
Calcium (Ca) Dairy products, e.g. milk, cheese
and yoghurt; green
vegetables, e.g.
broccoli.
* To build and maintain healthy bones and teeth.
* Helps blood to clot at cuts.
- Rickets in children.* Osteoporosis in adults: brittle, fragile bones.* Weak, brittle nails.* Tooth decay.
iron
Red meat, liver, eggs, beans, nuts,
dark green leafy
vegetables.
* To make haemoglobin, thered pigment in red bloodcells.
* Anaemia: reduced numbersof red blood cells in theblood, pale complexion, tiredness, lack of energy.
sodium
Sodium (Na),
Sodium: table salt, cheese, cured
meats.
- Needed for the transmissionof nerve impulses andmuscle contraction.
- Help maintain the correct
concentration of body
fluids. - Muscular cramps.
surplus of sodium
hypertension, high blood pressure
surplus of iron
liver damage
surplus of calcium
cause calcification of soft tissues, especially the kidneys and inside bloodvessels, and the development of kidney stones
reducing sugars
e.g. monosaccharides some disaccharides
Add an equal volume of Benedict’s
solution and shake. Heat the mixture.
An orange-red precipitate forms.
Non-reducing sugars – some disaccharides, e.g. sucrose
Add a few drops of dilute hydrochloric acid and heat for 1 minute.
Add sodium
hydrogencarbonate until effervescence
stops.
Add an equal volume of
Benedict’s solution and shake. Heat the
mixture.
An orange-red precipitate forms.
The acid hydrolyses the disaccharide molecules tomonosaccharide molecules. The sodium hydrogencarbonate neutralises the acid allowing theBenedict’s solution to react with the monosaccharides.
Starch
Add a few drops of iodine solution andshake.
Solution turns blue-black.
protein- buriet test
Add an equal volume of sodium
hydroxide solution and shake. Add drops of dilute copper sulfate solution and shake. Or add an equal volume of
biuret reagent and shake.
Solution turns purple. lilac
Lipid- emulsion test
Place 4 cm3
of ethanol in a dry test tube.
Add one drop of test substance and shake. Add an equal volume of waterand shake.
A milky-white emulsion forms.
lipid- grease spot test
Rub a drop of test substance onto absorbent paper. Leave for 10 minutes. A translucent mark remains.
