LO3 Flashcards
what is the function of the digestive system?
to process the breakdown and absorption of food and the removal of waste food products from the body
order of the digestive system
eat food
buccal cavity
salivary glands
epiglottis
oesophagus
stomach
liver
gall bladder
pancreas
duodenum (small intestine)
ileum
large intestine
rectum
anus
function of buccal cavity
where we put food - opening into the body and the beginning of the digestive tract
where food is chewed to break it down
use our jaw and teeth to grind food up so it is easier to digest
Mechanical digestion
function of the salivary glands
produce and release saliva into the buccal cavity
helps to moisten food which makes it easier to swallow
contains amylase which is an enzyme that starts the chemical digestion of sugars
Chemical digestion
function of the epiglottis
a flap of cartilage behind the root of the tongue which covers the opening of the windpipe when swallowing food
this prevents food particles and liquids from entering the larynx and trachea and getting into the lungs - prevents choking
function of the oesophagus
a muscular tube that connects the buccal cavity to the stomach.
It is lined with muscles to push the bolus down to the stomach in a rhyming motion called peristalsis.
function of the stomach
receives chewed food from the oesophagus
tiny glands in the stomach lining secrete gastric juice, which contains acids, mucus and enzymes
mechanical digestion - muscular walls churn the food
chemical digestion - acid and enzymes work together to break down carbs, proteins, fats into smaller molecules
this results in a ‘soup’ called chyme
function of the liver
main function is to process the nutrients absorbed from the small intestine
Bile produced from the liver is stored in the gallbladder, before being secreted into the duodenum. Bile emulsifies fats and helps chemical digestion in the duodenum, jejunum and ileum.
function of the gall bladder and bile duct
the small sac shaped organ beneath the liver, in which bile is stored after secretion by the liver and before the release into the small intestine.
the bile duct releases bile into the duodenum
function of the pancreas and pancreatic duct
a large gland behind the stomach which secretes digestive enzymes into the duodenum to aid chemical digestion.
it secretes the hormone insulin and glucagon into the blood
function of the duodenum and ileum (SI)
runs between the stomach and large intestine
made up of 4 sections
- duodenum
-jejunum
-ileum
-caecum
chyme then enters the duodenum and is mixed with bile and enzymes from the pancreas, so chemical digestion continues.
the ileum is covered in finger like projections called villi that increase the surface area of the small intestine to increase the rate of absorption of nutrients into the blood
function of the large intestine
this is wider and shorter than the small intestine
typically divided into ceacum, colon and rectum
absorption of water and the formation of faeces happens here
function of the rectum
faeces are stored in the rectum until they are passed out of the body through the anus
function of the anus
the opening at the end of the digestive tract through which solid waste matter leaves the body
what is mechanical digestion?
- when food is physically broken down to make it smaller.
- chewing action = teeth break down large pieces of food into smaller ones that can be swallowed.
- the stomach churns food to break it down
- in the small intestine, the bile emulsifies lipids which helps with the mechanical digestion of fats.
what is chemical digestion?
- where nutrients are broken down by enzymes to smaller molecules that can be absorbed into the blood and used by cells.
- in the buccal cavity, food is dissolved with saliva, which contains an enzyme called amylase to break down carbs.
- the stomach mixes food with enzymes and hydrochloric acid while churning it. The hydrochloric acid helps to break down the food as well as killing the bacteria in the stomach to prevent illness.
Action of digestive enzymes in stomach
- proteins broken down into amino acids by proteases, such as pepsin.
- HCL creates an acidic environment which generates pepsin
- digestive juices released.
Action of digestive enzymes in small intestine
- proteins broken down by pepsin
- chyme that enters is acidic so it is neutralised by the bile as small intestine needs alkaline conditions for enzymes to work.
-fats broken down by lipase in fatty acids and glycerol for absorption. Bile also aids this by emulsifying fats. - starch broken down by amylase.
how do enzymes work?
enzymes are folded into complex 3D shapes that allow smaller molecules to fit into them. The place where these molecules fit is called the active site. In the lock and key hypothesis, the shape of the active site matches the shape of its substrate molecules. This makes the enzyme highly specific.
- enzymes have a specific shape.
- large food molecules bind to the active site on the enzyme.
- the enzymes break chemical bonds of the food molecules thereby breaking them into smaller molecules that can be absorbed from the small intestine into the blood stream.
-enzymes work best in alkaline conditions and at 37 degrees (body temp)
Digestive roles of pancreatic juice
-the pancreas produces digestive enzymes that are released into the small intestine in pancreatic juice
- the pancreatic juices that are released into the duodenum help the body to digest fats
- the pancreatic juices are released into a system of ducts that culminate in the main pancreatic duct
Digestive role of bile
- bile is a digestive juice produced by the liver and stored in the gallbladder. It is released into the duodenum by the bile duct. Bile is needed for the process of emulsification. Emulsification is the breakdown of fats into fatty acids and glycerol. Emulsification needs to happen because insoluble fat molecules need to be broken down into fatty acids and glycerol so they can be absorbed into the blood stream.
Bile emulsifies fats so that lipase produced by the pancreas can break down fats.
what are villi?
tiny finger-like projections that increase the surface area of the small intestine.
3 adaptations of villi for absorption of nutrients
- wall is only one cell thick because it ensures that there is only a short distance for absorption to happen by diffusion and active transport
- network of blood capillaries because it transports nutrients, glucose and amino acids away from the small intestine into the blood
- internal structure called a lacteal which transports fatty acids and glycerol from the small intestine into the lymph.
Absorption definition
- is the movement of nutrients, water and electrolytes from the lumen of the small intestine into the cell then into the blood
Assimilation definition
- is the movement of digested food molecules into the cells of the body where they are used.
e.g. glucose is used in respiration for energy
Role of the liver in assimilation
- excess glucose in the blood reaching the liver is converted into glycogen to be stored or broken down through respiration, producing energy
- where toxins, such as alcohol, are broken down
- distributes nutrients to cells when they are needed.
- involved in deamination - where part of an amino acid is removed to form urea, followed by the release of energy from the remainder of the amino acid.