Show Menu
Cheatography

6.1 Digestion and absorption Cheat Sheet (DRAFT) by

Cheat sheet for IB Biology HL Chapter 6.1 (2016 syllabus)

This is a draft cheat sheet. It is a work in progress and is not finished yet.

Organs in the digestive system

There are two main groups of organs which comprise the human digestive system, the alimentary canal and the accessory organs.
The alimentary canal consists of organs through which food actually passes.
The accessory organs aid in digestion but do not actually transfer food.
Alimentary canal organs
Oesophagus
A hollow tube connecting the oral cavity to the stomach when're the food is mixed with saliva and then is moved in a bolus via the action of perist­alsis. It is separated from the trachea by the epiglo­ttis.
Stomach
A temporart storage tank where food is mixed by churning and protein digestion begins. It is lined by gastric pits that release digestive juices, which create an acidic enviro­nment (pH~2).
Small intestine
A long, highly folded tube where nutrients are absorbed. It consists of the duodenum, jejunum and ileum.
Large intestine
The final section of the alimentary canal, where water and ions are absorbed. It consists of of the ascending, transv­erse, descending and sigmoidal colon, as well as the rectum.
Accessory organs
Salivary glands
Release saliva to moisten food, and contains enzymes to initiate starch breakdown. Salivary glands include the parotid gland, subman­dibular gland and sublingual gland.
Pancreas
Produces a broad spectrum of enzymes that are released into the small intestine via the duodenum. It also secretes certain hormones (insulin and glucagon), which regulate blood sugar concen­tra­tions.
Liver
Takes raw materials absorbed by the small intestine and uses them to make key chemicals. Its role includes detoxi­fic­ation, storage, metabo­lism, bile production and haemog­lobin breakdown.
Gall bladder
The gall bladder stores the bile produced by the liver (bile salts are used to emulsify fats). It is released into the small intestine via the common bile duct.

Mechanical digestion

The contra­ction of circular and longit­udinal muscle of the small intestine mixes food with enzymes and moves it along the gut.
**Mech­anical digestion involves breaking down food into physically smaller via the acts of chewing, churning and segmen­tation.
Chewing
Chewing/mastication involves the grinding of teeth in order to break food down into smaller chunks, while the tongue pushes these small chunks towards the back of the throat, where it travels down the oesophagus as a bolus.
Churning
Churning occurs in the stomach, where muscles in the stomach lining physically squeeze and mis the food with digestive juices.
Food is digested in the stomach for many hours, and the creamy paste that is formed is known as chyme.
Perist­alsis
Peristalsis is the principal mechanism of moment in the oesoph­agus, and involves continuous segments of longit­udinal smooth muscle rhythm­ically contra­cting and relaxing.
Food is moved unidir­ect­ionally allong the alimentary canary from the mouth to the anus.
Segmen­tation
Segmentation involves the contra­ction and relaxation of non-ad­jacent segments of circular smooth muscle in the intestines.
Segmentation contra­ctions move chyme in both direct­ions, allowing for a greater mixing of food with digestive juices.
 

Features of the digestive system diagram

Production of an annotated diagram of the digestive system.
Stomach should look like a ‘J’-shaped bag and be connected to the oesophagus and small intestine
Liver should look like a right-­angled triangle and be superi­mposed to the left of the stomach (right side of the human)
Bile duct (connected to gall bladder) and pancreatic duct should both feed into a U-shaped bend of the small intestine
Small intestine should be thinner in width than the large intestine

Digestive system diagram