alimentary canal Flashcards
what is the alimentary canal
continuous tube that runs from mouth to anus, together with associated organs, the alimentary canal makes up the digestive system
- mouth
ingestion occurs air mouth, food is chewed and both MD and CD commence before the food is swallowed
- teeth
action of jaws and teeth begin mechanical digestion
four types of teeth, a full set of adult teeth (lower jaw) consist of:
- four incisors: used for cutting and biting
- two canines: used for tearing
- four premolars: crushing and grinding
- six molars: crushing and grinding
after chewed, tongue shapes food not plus and moves it to the pharynx
- saliva
when food is chewed, its mixed with saliva
saliva is secreted into mouth by salivary glands
- contains mucus + SALIVARY AMYLASE to lubricate food and begin CD of starch into disaccharide MALTOSE
- oesophagous
23-25cm long tube that connects pharynx to stomach
- has double layer of muscle: circular and longitude
as food enters P and O, the circular muscle behind the food contracts to narrow the tube
- the contraction of these successive bands causes the O to move in a wave called PERISTALSIS
- this pushes food down (assisted by mucus)
- the stomach (mechanical)
j-shaped
MD achieved by waves of muscular contraction that move along the stomach wall (3 muscles, oblique, circular and longitude)
this churns the food and mixes it with stomach juices until food is converted into chyme
- the stomach (chemical)
the lining of the stomach has gastric glands that, secretes gastric juice.
gastric juice: contains hydrochloric acid, mucis and digestive enzyme - mainly starts protein digestion
pepsinogen converts to pepsin
pepsin > proteins > peptides
nucleic acids > DNA + RNA
- pyloric sphincter
after food has been in stomach for 2-8 hours, the stomach contents are pushed from pyloric sphincter into duodenum
- small intestine (3 regions + influences)
receives material through pyloric sphincter, 6-7m long
1. duodenum: 25cm long, most chemical digestion occurs here before chyme moves further
2. jejunum: lining of jejunum allows effective absorption of carbohydrates and proteins
3. ileum: vitamin B12, bile salts and remaining products of digestion are absorbed
digestion continues under influence of:
pancreatic juice, bile, intestinal juice
pancreatic juice
enters duodenum through bile duct, helps neutralise acid and contains enzymes:
pancreatic amylase: breaks down starch
pancreatic protease: proteins > amino acids
ribonuclease/deoxyrybonucelase: digest RNA/DNA
pancreatic lipase: fats > fatty acids + glycerol
bile
secreted into small intestine through CBD
bile salts: emulsify fats, breaking it into tiny droplets
intestinal juice
peptidase: peptides > amino acids
sucrase: sucrose > glucose+fructose
lactase: lactose > glucose+galactose
maltase: maltose > 2 glucose
lipase: fatty acids > glycerol
absorption of nutrients in small intestine
digested nutrients ae absorbed through internal surface of small intestine
- the inner lining (mucosa) has folds that extend into interior of the small intestine
- mucosa have small, finger like projections called villi
- cells covering villi have projections called microvilli
villi - structure and function
each villus is about 1mm long
inside villus is lymph capillary (lacteal) that’s surrounded by blood capillaries.
amino acids, simple sugars, water/watersolube vitamins, fatty acids and glycerol are absorbed
- the large intestine
1.5m long,
- made up of caecum, colon, rectum and anus
- no villi, no digestive juices are secreted but lots of mucus
- bacteria in large intestine break down most remainging organic compounds, some bacteria produce vitamins that are absorbed through walls of blood along w/ mineral nutrients
- water is absorbed
- the semi solid after water absorbed and bacterial action makes up faeces.
- faeces: water, undigested food material, bacteria, bile pigment
the faces pass through rectum and anus to the exterior of the body
