6.1 DIGESTION Flashcards
exocrine gland
secretes liquid
endocrine gland
secretes hormones
Alimentary canal
organs through which food actually passes
- Mouth
- Oesophagus
- Stomach
- Small Intestine
- Large Intestine
Mouth
Ingestion
Chewing (mechanical)
Chemical digestion (salivary amylase) of starch into maltose
Oesophagus
A tube connecting the mouth 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
No enzymes in Oesophagus
Stomach
A temporary storage tank where food is mixed by churning (mechanical) by muscular actions
Mucus is released to protect the lining of the stomach
It is lined by gastric pits that release gastric juices (hydrochloric acid), which create an acidic
environment (pH 2) and kills any bacteria and denatures proteins
Gastric acid has pepsin, which begins digestion of large polypeptide into smaller proteins (chemical)
Small Intestine
Things move by peristalsis
a. Duodenum
Bile from the liver and gallbladder neutralises acid and emusifies fat (breaks down large fats to smaller ones to increase SA)
Pancreatic juice (amylase, lipase and protease-trypsin) digest starch, fats and peptides respectively
Maltase is an immobilised enzyme, part of the membrane of the small intestine, breaking down maltose into glucose
a. Illeum
Absorbs nutrients into the blood via the villi, and close association with blood capillaries
Large Intestine
where water and dissolved minerals (ions) are absorbed
Mucus is released to lubricate the movement of the faeces and peristalsis keeps it moving
Any undigested food (fibre-cellulose), dead cells and other cells are forced out of the anus
Accessory organs
aid in digestion but do not actually transfer food
- Salivary glands
- Pancreas
- Liver
- Gall Bladder
Salivary Glands
Release saliva to moisten food and contains enzymes (salivary amylase) to initiate starch breakdown to maltose
ph 7-8
Pancreas
Produces a broad spectrum of enzymes that are released into the small intestine via the duodenum
Liver
Takes raw materials absorbed by the small intestine and uses them to make key chemicals
- Detoxification
- Storage
- Metabolism
- Bile production
- Haemoglobin breakdown
Gall Bladder
Stores the bile produced by the liver
This is then released into the small intestine via the common bile duct
Peristalsis
Moves food through the alimentary canal
Mixes food with enzymes and forces the products of digesiton
into contact with the wall of the intestine.
Therefore in the intestines the food is moved very slowly to
allow time for digestion.
Enzymes
(globular proteins)
Released in the gut from glands and are used in catabolic reactions
Human Digestive Enzymes
- Starch amylase
- Maltase
- Proteases
- Lipases
Starch amylase
Breaks down starch into maltose. It is excreted from salivary glands and pacreas andworks at pH 7-8
Maltase
Breaks down maltose into glucose. It is found in the small intestine’s membrane as an immobilised enzyme and works at pH 7
Proteases
Break down polypeptides into peptides into amino acids.
Pepsin in stomach. Excreted from gastric glands and works at pH 2
Trypisn in small intestine. It is excreted from the pancreas and works at pH 7
Lipases
Breakdown tryglicerides into fatty acids and lipids. It is excreted from the pancreas and works at pH 7
Absorption
Monomers (amino acids, glucose, vitamins etc) are in the lumen of the illeum, and are absorbed by osmosis, diffusion, facilitated diffusion, & active transport to the blood.
Large intestine helping absorption
- Mucosa → inner lining, includes villi:
Microvilli: Ruffling of epithelial membrane further increases surface area
Rich blood supply → Dense capillary network rapidly transports absorbed products
Lacteals → Absorbs lipids from the intestine into the lymphatic system as hydrophobic
d. Intestinal glands → Exocrine pits (crypts of Lieberkuhn) release digestive juices
e. Membrane proteins → Facilitates transport of digested materials into epithelial cells
f. One cell thick epithelium → Minimises diffusion distance between lumen and blood - Submucosa → connective tissue between mucosa and mucle
- Muscular layer → inner circular and outer longitudinal muscles perform peristalsis
- Serosa → protective outer layer
