mechanical and chemical digestion, absorption and assimilation Flashcards
(30 cards)
what is mechanical digestion?
a physical process that aids the process of digestion
in what parts of the body does mechanical digestion take place?
the mouth (buccal cavity), stomach
in what parts of the body does chemical digestion take place?
salivary glands - produces saliva
gastric glands (stomach wall) produce gastric juice
liver makes bile
pancreas produces pancreatic juice (digestive enzyme)
intestinal glands (small intestine wall) produces intestinal juice (enzymatic digestion)
What digestive processes take place in the buccal cavity?
mechanical digestion by food being chewed means that the digestive process that takes place is much easier, due to the larger surface area that is created for chemical digestion
the salivary glands release salivary amylase which breaks down starch into maltose
what digestive processes take place in the oesophagus?
food travels down the oesophagus which is made up of thick muscular wall, and when these muscles contract and relax, it creates a wave like motion, which allows the food to move down.
This process is called peristalsis
what digestive processes take place in the stomach?
a layer of thick muscles with the inner layer producing enzymes
the stomach can store and digest food including proteins
the enzyme pepsin digests these proteins
another gland in the stomach produces mucus which prevents the stomach being digested by it’s own enzymes
HCL released to destroy harmful bacteria and microorganisms. This provides an optimum working condition for pepsin (PH)
what digestive processes take place in the small intestine?
gastric juice is passed into the small intestine to be further digested by enzymes
the inner wall in folded into villi, which provides a larger surface area for the absorption of products from digestion into the blood stream
digestion of fat by lipase
digestion of protein by trypsin
digestion of starch by amylase
what digestive processes take place in the pancreas?
pancreatic juice contains the enzyme lipase, trypsin, and amylase
what digestive processes take place in the liver?
liver stores excess glucose as glycogen and is also the site of deamination (amino groups removed from excess proteins) and produces bile
what does bile do?
converts large molecules of fats into tiny droplets and this process is called emulsification which increases surface area, therefore aiding digestion
what digestive processes take place in the large intestine?
water absorbed from chyme (fluid from stomach) which leaves faeces
most of the water that is reabsorbed comes from the secretions of many digestive glands
faeces stored in rectum, and removal via the anus is called egestion
what does chemical digestion do?
breaks down large, insoluble molecules into smaller soluble ones
it uses enzymes that function by hydrolysis- called hydrolases
they are called carbohydrates- monosaccharides, lipases- glycerol/ fatty acids and proteases- amino acids
once hydrolysed, they are absorbed via different mechanisms into the blood stream to either be incorporated into the body tissues or help with different processes, this is called assimilation
how are carbohydrates broken down and where? what is the product?
salivary amylase- salivary glands- maltose
pancreatic amylase- pancreas and small intestine-maltose
maltase-small intestine- maltose
how are proteins broken down and where? what is the product?
pepsin-stomach mucosa-peptides
trypsin-pancreas-peptides
peptidases-intestinal mucosa-amino acids
how are fats broken down and where? what is the product?
lipase-pancreas-fatty acids and monoglyerides
what are enzymes?
little ‘machines’ that increase the speed of a chemical reaction without themselves undergoing chemical change
how do enzymes work?
the substrate sucrose consists of glucose and fructose bonded together
the substrate binds to the enzyme, forming an enzyme-substrate complex
the binding of this place stress on the glucose fructose bond and the bond breaks
the products are released and the enzyme is free to bond to other substances
what are the main enzyme producing structures of the human digestive system?
salivary glands stomach pancreas liver small intestine
what is the first major region of the small intestine, where digestive action is carried out?
the duodenum
pancreas enzymes are secreted into the duodenum (pancreatic juice contains protease, amylase, lipase, sodium hydrogen carbonate) it travels through the pancreatic duct to mix with food in the duodenum
it connects the pyloric sphincter of the stomach
it is the shortest region (10 inches)
partially digested food or chyme from the stomach is mixed with bile from the liver and pancreatic juice to complete it’s digestion in the duodenum
what is the second major region of the small intestine, where digestive action is carried out?
the jejunum
middle section that serves as the primary site of nutrient absorption
3 feet in length
what is the third major region of the small intestine, where digestive action is carried out?
the ileum- empties into the large intestine
6 feet long
completes the absorption of nutrients that were missed in the jejunum
lined with villi which help to increase surface area
this helps to increase the rate of absorption and digestion
each villus is covered with a one cell thick layer called the epithelium
there is a network of blood capillaries that help to absorb glucose and amino acids
a blind-ended lacteal absorbed the products of digestion of fat
it contains muscles to move around, mixing food with enzymes
what is sodium hydrogen carbonate?
an alkaline solution that neutralises the acidity from the stomach- in pancreatic juice which is passed into small intestine
what does bile contain?
bile salts
bile pigments
sodium hydrogen carbonate
what do bile salts do?
help to emulsify fats which means to change large droplets of fat into smaller ones
called emulsification
