The Digestive system in animals Flashcards
Information included in this deck: -Food and Digestion (steve parker) - 3.5 digestive system (powerpoint) - 3.5 The Digestive system (textbook chapter)
Name the main parts of the digestive system
- mouth
- salivary glands
- oesophagus (gullet)
- stomach
- small intestine
- rectum
- liver
- anus
- appendix
- pancreas
- large intestine (colon)
Before food is absorbed by the body, it must be broken down into tiny pieces called molecules. Why must they be small?
They must be small enough to dissolve in water so that they can pass through the wall of the digestive tube into the body
Glands along the length of the digestive system produce strong chemicals such as what?
acids, alkalis and enzymes which attack food chemically, breaking them into smaller and smaller pieces
There are several kinds of enzymes, and each one breaks down a certain kind of food, give examples
pepsin and trypsin attack protein foods such as meats - amylase and maltase work on carbohydrate food. fats do not dissolve into water, instead forming bob-lie droplets (emulsified) and then worked on enzymes called lipases
Some enzymes work in acidic conditions, while others need alkaline surrounding - explain further.
ass foods move through each region of the digestive system, they are flooded with mixtures of acid and enzymes, or alkali and enzymes. these corrosive liquids gradually break down the food substances
A typical part of the gut such as the intestine is made up of several layers - what are they?
mucosa (inner lining) submucosa inner muscle layer outer muscle layer serosa (outer coating)
Describe the mucosa
The inner lining is called the mucosa and may be wrinkled or folded to give a large surface area for the production of digestive chemicals and absorption of nutrients. this layer contains many microscopic glands which pour out, or secrete, the many digestive chemicals such as enzymes, acids and alkali.
Describe the submucosa
Around the submucosa which is tough and elastic and forms a strong “framework” for the gut. it contains blood vessels that nourish the other layers and nerves that control the muscles of the gut. The gut muscles are wrapped around the submucosa and form the next two layers and act to push food through the inside of the gut by the process of peristalsis
The gut is long and folded - most of it is tightly paced into the abdomen and internal body pressure squashes it flat - how does this impact food passing through it?
Foods cannot pass through it unaided and must be pushed. The process of peristalsis moves the food, its journey is lubricated by the slippery mucus in the gut wall.
Peristalsis involves what?
a muscular action involving both muscle layers working in a coordinated fashion - two nerve networks control the muscles. first the inner layer just behind the food contracts making the gut narrower at the this point and pushes the food forward a little. then the outer muscle layer contracts to shorten the length of that part of the gut and at the same time the narrowed portion moves along the gut, pushing the food in front of it.
The mouth is the first region of the gut and the ____ and _____ process of digestion
Physical and chemical
As we chew what is produced?
salvia is produced from the glands around the mouth and is mixed with the food. it helps to soften, moisten and lubricate the food ready for swallowing.
What enzyme does salvia contain?
amylase which begins the chemical attack on carbohydrates
Teeth do what?
The chewing and biting, cutting and mashing the food into pulpy lumps so it can be easily swallowed.
What is the second main region of the gut
the oesophagus
describe the oesophagus
it is a muscular tube, long, just behind the trachea connecting the throat to the stomach
what happens as you swallow?
the tongue pushes a lump of food towards the back of the mouth and into the pharynx. as this happens the top of the trachea rises upward and a small flap the epiglottis folds over to cover its entrance which prevents the food going down the wrong way.
What is at the base of the oesophagus?
A valve-like arrangement of muscle called the oesophageal sphincter which is normally tightly closed. as the food arrives from above the valve relaxes and allows the food to pass through into the stomach and closes again to seal off the passageway
Describe the stomach
A very tough, muscular, J-shaped bag.
How does the stomach squash the food
The muscles in the stomach will contract strongly in peristaltic waves to churn and squash foods that have already been chewed in the mouth
Where does the oesophagus join the stomach?
near its broad upper part, called the fundus. the lower part, the pylorus does most of the churning and this is where the main digestive processes occur
The stomach lining contains what?
millions of tiny glands, these make digestive liquid called gastric juice which contains the chemical hydrochloric acid. the acid attacks the food and softens it as a part of the process of chemical digestion.
What else do the glands in the stomach lining make?
an enzyme-like substance, pepsinogen. when this meets the stomach acid it is converted into the enzyme pepsin which begins to digest the proteins in the food.
What is the soupy sloppy food which leaves the stomach called?
chyme
where does the chyme go from the stomach?
through another valve- like ring of muscle, the pyloric (or duodenal) sphincter and into the first part of the small intestine which is known as the duodenum
The duodenum is shaped around what?
the broad end of the pancreas, one of the digestive systems glands
the chyme that enters the duodenum is what?
strongly acidic, and would corrode the intestine further on. so it is neutralised by alkali in the duodenum, also stopping the action of the enzyme pepsin which only works in acidic conditions
where is bile made?
in the liver and is stored in the gall bladder. when chyme starts to flow through the duodenum, the gall bladder contracts and squirts bile along the bile duct into the duodenum.
what does bile contain?
emulsifying chemicals which help to break up blobs of fat in the chyme
where is the pancreas located?
in the upper left abdomen, behind the stomach around the level of the lower ribs
The pancreas is what?
a dual-function gland
what is one of the jobs of the pancreas
to make an enzyme-containing juice for digestion. the pancreas produces the pancreatic juice, containing many strong enzymes that carry out digestion in the duodenum and small intestine
what is the other job of the pancreas
to make a hormone (body chemical) called insulin. insulin helps to control the amount of sugar in the blood stream and the way cells use energy. it is released straight into the blood, flowing through the pancreas rather than being channelled along ducts like the digestive pancreatic juice
Most absorption takes place where?
in the rest of the small intestine, directly after the duodenum
The inner lining of the small intestine has what?
an enormous surface are, in order to absorb as many nutrients as effectively as possible.
What are the three factors that make the absorption of nutrients possible?
- the lining is rigid instead and folded, rather than being smooth
- the ridges are covered in millions of tiny finger like projections called villi
- the villi bear their own microscopic finger like structures known as microvilli
the small intestine lining has what?
rich blood supply
Where is water absorbed
in the last part of the gut, the large intestine
name the first part of the large intestine
- first is short and wide and is known as the cecum, water unabsorbed materials flow into the cecum from the small intestine under control of a sphincter-like structure, the ileocecal valve
name the second part of the large intestine
- next the materials pass into the colon, a wide tube shaped lie an upside-down U and goes up the right side of the abdomen across the top and down the left side. water and salts are absorbed through the lining into the body, as this happens the materials become less fluid and change into the brownish, moist, semi solid faeces or stool
name the third part of the large intestine
the third part is rectum, it is long and can stretch to store some of the faeces as they are passed to the outside (defected) which happens through the final part of the gut, the anus, which is another muscular sphincter
What is digestion?
The digestive system is the system for processing food and drink in animals
What is the main function of digestion?
to turn food into energy and obtain nutrients to keep the body healthy by breaking down foods into smaller substances that the body can absorb
What are the three key parts the digestsive system?
ingestion - process of taking food in to the digestive system
digestion - the mechanical and chemical breakdown of the food
absorption - process where small molecules products enter the bloodstream
egestion - process of non-digested food being eliminated from the body
What happens in the mouth?
Salvia is simulated by the sight and smell of food from the salivary glands. The tongue manipulates the food around ready for chewing and swallowing - teeth shred the food into smaller pieces
salivary glands secrete what?
salvia (a fluid) into the mouth to
- moisten the food to help swallowing
- begin the chemical breakdown of starch as it contains digestive enzymes amylase
What happens in the oesophagus?
- the oesophagus is a tube of muscles which leads from the mouth to the stomach
- it is usually around 20-25 cm in length but this can vary
- it takes 5-10 seconds for the food to pass from the mouth to the stomach
- there is no breakdown of food
Food is moved through the oesophagus in a series of involuntary wave-like muscle contraction known as peristalsis
Food then reaches what?
the oesophageal sphincter which prevents acidic mixture from the stomach from splashing back up the mouth
