Biology Topic 6: Human physiology

what are the two major groups of organs which compromise the human digestive system?

* alimentary canal consists of organs through which food actually passes (oesophagus, stomach, small and large intestine
* accessory organs aid in digestion but do not actually transfer food (pancreas, gall bladder, salivary glands, liver)

explain the path and functions of the alimentary canal

oesophagus

* hollow tube connecting the oral cavity to the stomach (separated from the trachea by the epiglottis)
* food is mixed with saliva and then is moved in a bolus via the action of peristalsis

stomach

* a temporary storage tank where food is mixed by churning and protein digestion begins (enzyme pepsin - works best at pH 2 with HCL in stomach)
* lined with gastric pits that release digestive juices, which create an acidic environment (pH 2)

small intestine

* long highly folded tube where usable food substances (nutrients) are absorbed
* consists of 3 sections:
* duodenum
* jjejunum
* ileum

large intestine

* final section of the alimentary canal
* where water and dissolved minerals (ions) are absorbed
* consists of the ascending/transverse/descending sigmoidal colon and the rectum

accessory organs

salivary glands

* release saliva to moisten food and it contains enzyme (amylase) to initiate starch breakdown
* salivary glands include parotid gland, submandibular gland and sublingual gland

pancreas

produces a broad spectrum of enzymes: amylase, protease and lipase for starch, proteins and glucose breakdown - released into the small intestine