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Biology > Chapter 12 - Alimentary Canal, Digestion and Absorbtion. > Flashcards

Chapter 12 - Alimentary Canal, Digestion and Absorbtion. Flashcards

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0
Q

Why is digestion important?

A
  • Nutrients in food to large to absorb into blood.
  • These nutrients must be hydrolised ( digested ) into smaller molecules. ( amino acids, fatty acids, glycerol )
  • Then it can absorb it into the blood stream.
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1
Q

What is digestion?

A
  • is the breakdown of large, complex insoluble molecules
  • into very small, simple soluble molecules
  • so it can be absorbed into the blood stream.
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2
Q

Define the alimentary canal.

A
  • it is a muscular tube leading from the mouth to the anus.

- food is conveyed, digested and absorbed in it.

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3
Q

Name the different parts of the alimentary channel in chronological order.

A
  • oesophagus.
  • stomach
  • duodenum
  • ilium
  • colon
  • caecum
  • rectum
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4
Q

Define the digestive system. Include the different organs associated with it.

A
  • it is the alimentary canal plus its associated organs.
  • namely:
  1. teeth
  2. salivary glands
  3. liver
  4. gall bladder
  5. pancreas
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5
Q

Know the sketches on page 219. must be able to label. if uncertain what to do, read below.

A
  • you are uncertain. please follow the guidelines above.
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6
Q

Define ingestion.

A
  • the process of taking food nutrients into the alimentary canal
  • through the mouth cavity.
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7
Q

Define digestion.

A
  • the hydrolysis of large, complex insoluble nutrients
  • into very small, simple soluble molecules.
  • so it can be absorbed.
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8
Q

Define absorbtion.

A
  • the process whereby hydrolised molecules passes through the walls of the alimentary canal.
  • into the blood stream.
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9
Q

Define the transport process.

A
  • The process whereby the bloodstream transports the absorbed, digested molecules to liver and body cells.
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10
Q

Define assimilation.

A
  • the process of taking soluble molecules from capillaries into the body cells.
  • for usage.
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11
Q

Define egestion.

A
  • the process of discharging undigested food materials as waste.
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12
Q

know table on page 221 perfectly.

A
  • please follow the instructions above.
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13
Q

Describe the mouth and mouth cavity.

A
  • the mouth is the opening ( anterior ) of the alimentary canal.
  • bounded by two lips
  • mouth cavity contains the tongue, teeth and duct openings of the salivary glands.
  • chewing of food occurs here.
  • this makes it easier to swallow, and for enzymes to break down the food.
  • it is a mechanical action.
  • salivary glands produce saliva ( six glands )
  • little digestion occurs here.
  • masticated food is rolled into a bolus by tongue.
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14
Q

Why is flouride added to drinking water?

A
  • it reduces tooth decay

- it is a safe, simple and effective way to improve the dental health.

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15
Q

Name the four types of teeth.

A
  • incisors
  • canines
  • premolars
  • molars
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16
Q

What is the function of teeth?

A
  • they play a role in biting, chewing and grinding of food.
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17
Q

study the picture on page 222

A
  • if uncertain, read above

- if still uncertain, read above.

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18
Q

Know the scetch of the human tooth on page 223. NB

A
  • it came to my attention that you do not have the intention of paying attention to my intention in the line above.
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19
Q

Describe the incisors.

A
  • front teeth
  • chisel sharp
  • Function: for biting and cutting
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20
Q

describe the canines.

A
  • Found between incisors and premolars.
  • pointed teeth
  • for grasping and tearing of food.
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21
Q

Describe premolars.

A
  • found between canines and molars.
  • have cusps and surface.
  • function: crushing, grinding and chewing.
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22
Q

Describe the molars.

A
  • Found at back of the mouth.
  • have four cusps and three roots.
  • function: crushing, chewing and grinding.
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23
Q

What causes tooth decay?

A
  • A combination of food and bacteria causes tooth decay.
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24
Q

Describe the process of food decay.

A
  • clear, sticky substance called plague that contains bacteria always forming on your teeth and gums.
  • bacteria digest food that is stuck between teeth.
  • bacteria feeds on sugars in the food.
  • from this feeding they created acids.
  • these acids dissolve the enamel and dentine.
  • causes cavities.
  • toothache is caused when the cavities reaches the pulp cavity.
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25
Q

How can you reduce the process of tooth decay?

A
  • regular visits to dentist.
  • use detal floss
  • use anti-bacterial mouth wash.
  • eat crisp foods.
  • rinse mouth with water after eating.
  • avoid sugary food.
  • eat teeth protecting bubble gum
  • use toothpaste that contains fluoride.
26
Q

How does toothpaste work?

A
  • it contains either fluoride or a neutrilising chemical.
  • the fluoride strengthens the enamel.
  • the neutralising chemical neutralisis the acids.
27
Q

Describe the action of amylase in the mouth.

A
  • saliva contains amylase.
  • amylase hydrolyses insoluble starch into soluble maltose.
  • the hydrolysis is the first stage in starch digestion.
28
Q

Describe the pharynx.

A
  • Region at the back of the mouth cavity.
  • the part between the mouth cavity and the oesophagus.
  • the pharynx contrancts and pushes the bolus down the oesophagus
29
Q

Descibe the oesophagus.

A
  • muscular pipe that starts at the pharynx and ends at the stomach.
  • uses perestalsis to force food to stomach.
  • shincter muscle ( cardiac sphincter ) between stomach and oesophagus.
  • no digestion.
30
Q

What is the epiglottis?

A
  • It is a flap which closes the trachea during swallowing.

- ensures no food enters the windpipe.

31
Q

Know the figure on page 226 and you must be able to lable it.

A
  • please read above.
32
Q

What is peristalsis?

A
  • it is waves of rhythmical contractions which takes place in the alimentary canal to push food along.
  • the circular muscles behind bolus contracts, and the longitudinal muscles relax.
  • them the circular muscles infront of the food relaxes and the longitudinal muscles contracts.
  • this is antagonistic muscle action.
  • this action forces food along the alimentary canal.
33
Q

Describe the stomach.

A
  • lies just below the diaphragm.
  • it is an enlarged bag like part of the alimentary canal.
  • where the oesophagus and the stomach join, there is the cardiac sphincter.
  • at the exit it is the pyloric sphincter.
  • when food enters the stomach will expand untill 1L volume.
  • it holds and stores food for a while.
  • once food in stomach, wave like contractions will be cause by the circular stomach muscles.
  • the stomach will release gastric juice and it will be mixed with the food.
  • secreted by gastric glands.
  • gastric juice contains HCl
  • the semi-liquid that results is called chyme.
  • some absorbtion takes place.
  • eg glucose, menirals and alchohol.
  • HCl antiseptic to kill pathogens.
34
Q

Describe the role of sphincter muscles in the alimentary canal.

A
  • as you swallow, the upper esophageal sphincter opens in the pharynx for passage of food into the oesophagus.
  • the food then passe through the lower esopageal sphincter to the stomach.
  • at the entry point into the stomach the food passes through the cardiac sphincter.
  • between the stomach and deodenum the pyloric sphicter is found.
  • faeces removed from body at anus by the relaxing of the anal sphicter.
35
Q

Describe the role of gastric juice in the stomach.

A
  • it contains HCl to give stomach a very low ph.
  • contains inactive pepsinogen.
  • HCl activates pepsinogen.
  • forms into active pepsin.
  • it begins to digest protein into polypeptides.
  • pepsin requires acid conditions.
36
Q

Describe the gross structure and function of the deodenum.

A
  • it is the part between the stomach and the small intestine.
  • chyme passes from the stomach to the deodenum.
  • digestion is completed in the deodenum.
  • the intestinal glands in the deodenum secretes succus entericus.
  • succes entericus contains maltase, lipase and sucrase.
  • Brunner’s glands in deodenum produces mucus rich alkaline substance to protect the deodenum lining from the acid of the stomach.
  • it provides an alkaline condition for the intestinal enzymes to be active.
37
Q

Describe the ileum and its function.

A
  • it is the part between the deodenum and caecum.
  • end products of digestion ends up here.
  • it is called chyle.
  • chyle is a mixture of mant small soluble molecules.
  • these molecules ( maltose, fatty acids, etc. ) are absorbed by the villi into the blood stream. ( villi on surface of ileum )
  • the inner surface has folds to increase surface area.
38
Q

Name three features that increases the surface area of the ileum.

A
  • it is very long ( 6m ) convolted organ.
  • the inner lining has numerous folds and ridges.
  • small finger like projections called villi in the intestine.
39
Q

Explain the role of pancreatic juice in digestion.

A
  • it is connected to the duodenum be the pancreatic duct.
  • it release the enzymes trypsin, lipase and amylase.
  • it secretes sodium bicarbonate to neutralise the stomach acids.
  • this will render pepsin inactive and the pancretic enzymes will work in the alkaline conditions.
40
Q

Explain the role of bile in the digestion process

A
  • the gall bladder releases bile ( which is produces in the liver )
  • by means of the bile duct into the duodenum.
  • bile contains no enzymes.

Bile cause emulsification of fats.

  • emulsification is the breakdown of large fat globules into smaller fat droplets.
  • so the surface area increases to make it easier for lipase to act apon it.
41
Q

What is emulsification?

A
  • it is the breakdown of large fat globules into smaller fat droplets cause by bile.
  • it is to increase the surface area of fat.
  • makes it easier for lipase to act upon it.
42
Q

Describe the structure of a villus

A
  • Fingerlike projections about 1mm long
  • Surrounded by a single layer of epithelial cells
  • Single, central lacteal present in each villus
  • Dense network of capillaries inside
  • Epithelial cells have micro-villi
  • Goblet cells between epithelial cells which secretes mucus
  • The crypts of Lieberkuhn are inviginations of the epithelium between responsible for secreting succus entericus (intestinal juice)
43
Q

Describe how villi are adapted to speed up the rate of absorbtion in the illeum.

A
  • Finger-like shape to increase surface area
  • Micro-villi on the epithelial cells increase surface area
  • One layer of epithelial cells to minimise the distance of diffusion
  • Dense network of capillaries for the absorbtion of glucose, amino acids, vitamins and minerals
  • Single central lacteal for the absorbtion of fatty acids & glycerol
  • Epithelial cells contain many mitochondria for active transport
  • Goblet cells secrete mucus to keep the gut moist
  • Villi are constantly moving to bring nutrients in contact therewith
44
Q

Describe the absorbtion of nutrients into the blood into the blood

A
  • Glucose and amino acids are passively absorbed by diffusion and facilitated diffusion from a high concentration in the illeum to a low concentration in the blood
  • Glucose and oxygen (amino acids also) are also actively absorbed by active transport from a low concentration in the illeum to a high concentration in the blood
  • Fatty acids and glycerol are absorbed into the lacteal of the villus. From here it is transported in the lymphetic system, until it is then “dumped” into the bloodstream
45
Q

State the function of the hepatic portal vein

A
  • Major blood vessel in the abdomen acting as a collective point for blood from the digestive tract and routing this blood to the liver
  • All capillaries and venules from the digestive tract combine to form te hepatic portal vein
  • All nutrients taken up by capillaries in the stomach and villi are first taken to the liver by the hepatic portal vein. Therefore, no nutrient taken up into the bloodstream enters the body before going through the liver
  • The liver will decide what to do with nutrients
46
Q

Describe the role of the liver in the metabolism of glucose when the glucose level is HIGH

A
  • Blood sugar levels need to be kept within fairly narrow limits
  • The beta cells of the Islets of Langerhans in the pancreas secrete the hormone insulin into the bloodstream
  • The bloodstream transports the insulin to the liver
  • The insulin intstructs the liver cells to convert excess glucose into glycogen or fat
  • Glycogen can be stored in the liver and muscles, and fat as adipose tissue under the skin or around organs
47
Q

Describe the role of the liver in the metabolism of glucose when glucose levels are LOW

A
  • The alpha cells in the Islets of Langerhans in the pancreas secrete the hormone glucagon into the bloodstream
  • The bloodstream transports glucagon to the liver
  • Glucagon instructs the liver to convert glycogen and fats into glucose
  • This glucose can then be used by the body
48
Q

Explain the role of the liver in the maintainance of an amino acid pool

A
  • Proteins are hydrolised into amino acids in the digestive tract, absorbed by capillaries, and transported to the liver via the hepatic portal vein
  • The liver allows about 60g of amino acids to enter the body
  • Excess amino acids can not be stored
  • The liver removes the amino group (NH2) from the amino acid. This is known as deamination
  • Poisonous ammonia is formed (NH3)
  • The liver converts ammonia into a harmless substance known as urea by combining ammonia with carbon dioxide CO(NH2)2
  • The rest of the amino acid is converted into fats or carbohydrates for energy and storage
49
Q

Name the main function of the colon

A

Absorption of water

50
Q

Describe what happens to indigestible materials in the digestive system

A
  • Received by the colon
  • Colon absorbs most of the water, minerals and vitamins
  • Colon compacts indigestible materials into semi-solid faeces
  • Faeces sent to rectum, and released through the anus, controlled by a sphincter muscle
51
Q

Name the function of the caecum

A

NO function in humans, only connects illeum to colon. The presence of the caecum indicates that early human beings were able to digest cellulose from a vegetable diet. The enzyme cellulose was then present in the caecum.

52
Q

Describe the functions of the liver

A
  • Produces bile
  • Converts excess glucose into glycogen
  • Converts glycogen to glucose if necessary
  • Converts glucose to fat
  • Stores minerals like iron
  • Stores vitamins A, D, B
  • Deamination
  • Detoxification (Alcohol)
53
Q

Name the function of the gall bladder

A

Stores bile

54
Q

Name the functions of bile

A
  • Emulsification of fats
  • Absorption of fats
  • Absorption of vitamins A, D, E, K
  • Promotes peristalsis
  • Reduces fluidity of chyme
  • Antiseptic which kills pathogens which cause decomposition of food in intestines
  • Neutrilise stomach acids
55
Q

Describe the structure of a villus

A
  • Fingerlike projections (1mm)
  • Surrounded by a single layer of epithelial cells
  • Has a lymph vessel called a lacteal inside
  • Dense network of blood capillaries inside
  • Each epithelial cell has micro-villi
  • Goblet cells present between epithelial cells
  • Spaces called crypts of Lieberkuhn between villi which secretes succus entericus
56
Q

Explain how villi are adapted to speed up the rate of absorption

A
  • Shaped like fingers (longer than wide) to increase surface area
  • Brush border of micro-villi to further increase surface area
  • Single layer of epithelial cells to minimise travelling distance of nutrients
  • Dense network of capillaries to absorb glucose, amino acids, vitamins, minerals,
  • Single central lacteal to absorb fatty acids & glycerol
  • Epithelial cells have many mitochondria for active transport
  • Goblet cells keep the gut moist
  • Villi are constantly moving to bring nutriants in contact therewith
57
Q

Describe the absorption of substances into the blood

A
  • Glucose and amino acids are passively absorbed by diffusion and facilitated diffusion
  • Glucose and oxygen are also actively absorbed by active transport
  • Fatty acids & glycerol are absorbed into the lacteal
58
Q

Describe the role of the hepatic portal vein

A
  • Major blood vessel in the abdomen
  • Collection point for blood from the digestive tract
  • Routes blood into the liver
  • All capillaries from the digestive system join to form the hepatic portal vein
  • All nutrients except fats absorbed in the digestive tract is taken directly to the liver
59
Q

Why does the liver need to perform glucose metabolism?

A

Blood sugar levels need to be kept in fairly narrow limits

60
Q

Describe the role of the liver in the metabolism of glucose when glucose levels are high

A
  • Beta cells in the Islets of Langerhans in the pancreas release a hormone called insulin into the bloodstream
  • Insulin is transported to the lver
  • Insulin instructs liver to convert excess glucose into fats or glycogen
  • Glycogen can be stored in the liver and muscles
  • Fats are stored as adipose tissue under the skin and around organs
61
Q

Describe the role of the liver in the maintainance of an amino acid pool

A

Enzymes hydrolise proteins into amino acids. Amino acids are absorbed and transported to the liver. The liver allows amino acids to the rest of the body, but has to deal with excess amino acids which cannot be stored. Amino acids will be converted to other usefull molecules through a process known as deamination

62
Q

Describe the process of deamination

A
  • Excess amino acids cannot be stored
  • In the liver, the amino group (NH2) is removed from the amino acid
  • Ammonia is formed (NH3)
  • By combining the ammonia with carbon dioxide, the liver converts poisonous ammonia to urea CO(NH2)2
  • The rest of the amino acid is converted into usefull fats and carbohydrates
63
Q

Describe the role of fats as a storage substance

A
  • Storage
  • Insulation
  • Release of energy
  • Store vitamins like vitamin A,D,E,K
  • Protects vital organs

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