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IB Biology > Human Physiology - 6.1 Digestion and Absorption > Flashcards

Human Physiology - 6.1 Digestion and Absorption Flashcards

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1
Q

the two groups of organs which comprise the human digestive system

A
  1. Alimentary canal
  2. Accessory organs
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2
Q

alimentary canal

A

consists of organs through which food actually passes

(oesophagus, stomach, small and large intestine)

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3
Q

Accessory organs

A

aid in digestion but do not actually transfer food

(salivary glands, pancreas, liver, gall bladder)

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4
Q

The role of the: mouth

A

food is chewed (masticated) and mixed with saliva and swallowed

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5
Q

The role of the: oespohagus

A

A hollow tube connecting the oral cavity to the stomach (separated from the trachea by the epiglottis),

food is moved in a bolus via the action of peristalsis

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6
Q

The role of the: stomach

A

both stores food and begins the process of digestion.

churning and digestion of proteins into polypeptides occour

food remains int he stomach for 3-10 hours

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7
Q

muscles that control the entry and exit of materials in the stomach

A

sphincter muscles

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8
Q

The role of the: small intestine

A

is long and divided into 3 regions

it is lined with smooth muscles to allow for the mixing and moving of digested food productions

when acidic chyme enters the duodenum it is mixed with pancreatic juice, intestinal juice and bile which digest large molecules

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9
Q

the 3 regions of the small intestine

A

1) duodenum
2) jejunum
3) longer ileum

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10
Q

The role of the: Pancreas

A

secretes the enzymes amylase, lipase and an endopeptidase

also secrets certain hormones (insulin, glucagon) which regulate blood sugar concentrations

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11
Q

The role of the: liver

A

produces bile

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12
Q

role of bile (liver)

A

bile contains no digestive enzymes but contains salts which acts as a emulsifier and helps in the absorption of fates

bile also contains some wastes of the liver (red blood cell destruction)

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13
Q

The role of the: Gall Bladder

A

the gall bladder stores the bile produced by the liver (bile salts are used to emulsify fats)

bile stored in the gall bladder is released into the small intestine via the common bile duct

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14
Q

The role of the: large intestine

A

the indigestible parts of the food, such as cellulose fibre, as well as a large volume of water is passed to the large intestine (colon) water and ions are re-absorved here, leaving solid faeces which passes down the rectum and is ectum and is egested through the anus

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15
Q

what is included in the large intestine

A

1) ascending/transverse/descending/sigmoidal colon
2) rectum

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16
Q

Mechanical Digestion - understanding

A

= the contraction of circular and longitudinal muscle of the small intestine mixes the food with enzymes and movies it along the gut

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17
Q

stats about the digestive system:

A

= it is about 5 metres long
= takes about 24-72 hours for food to pass through it

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18
Q

Mechanical digestion - chewing

A
  • food is initially broken down in the mouth by the grinding action of teeth (chewing or mastication)
  • the tongue pushes the food towards the back of the throat where it then travels down the esophagus as a bolus
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19
Q

what is a bolus?

A

it is a lump of food

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20
Q

epiglottis’ interaction with the bolus

+

uvula’s interaction with the bolus

A
  • epiglottis prevents the bolus from entering the trachea
  • uvula prevents the bolus from entering the nasal cavity
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21
Q

Mechanical Digestion: Peristalsis

A

= the method of movement in the oesophagus, stomach and small intestine

  • smooth muscle rhythmically contract and relax
  • food is moved along the alimentary canal from mouth to anus
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22
Q

choaking =

A

when you eat something too big and peristalsis can not occour

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23
Q

Mechanical Digestion: Segmentation

A

= involves the contration and relaxation of non-adjacent segments of circular smooth muscle in the intestines

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24
Q

segmentation contractions in the stomach =

A

move chyme in both directions (ie food can go up and down (eg cows)) = allowing for a greater mixing of food with digestive juices

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25
Q

Chemical digestion - understandings

A

1) the pancreas secretes enzymes into the lumen of the small intestine
2) enzymes digest most macromolecules in food into monomers in the small intestine

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26
Q

the breakdown of large molecules in the human body

= digestion

A

some food that humans eat contain substances that are made by other organisms - they must be broken down into their parts (eg amino acids) so that the human body can rebuild them into useful substances

most food molecules are too large to be absorbed through the small intestine into our blood

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27
Q

protein goes through proteases/peptidases to form:

A

amino acids

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28
Q

polysaccharides and disaccharides goes through amylases to form:

A

monosaccharides

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29
Q

nucleic acid goes through nucleases to form:

A

nucleotides

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30
Q

fat goes through fat-digesting enzymes (ie lipides/lipases) to form:

A

glycerol fatty acids

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31
Q

cellulose/fibre - and NOT being broken down

A

cellulose remains undigested and is passed from the body in faeces

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32
Q

for details on where chemical digestion can occur in the body (the enzymes, substrates, products and pH)s can be found on PAGES =

A

4 and 5

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33
Q

What is the: villi in the small intestine

A

they help in the absorption of nutrients by increasing the surface area for absorption

so that the max amount of substance can be absorbed

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34
Q

consequences of celiac disease for absorption of digested nutrients

A

celiac disease flattens villi resulting in a lower amount of substances being absorbed and nutrients digested

35
Q

In chemical digestion, food is broken down by the action of chemical agents, these include

A

1) enzymes
2) acids
3) bile

36
Q

digestion of carbohydrates

A

Carbohydrate digestion begins in the mouth with the release of amylase from the salivary glands (amylase = starch digestion)

Amylase is also secreted by the pancreas in order to continue carbohydrate digestion within the small intestine

Enzymes for disaccharide hydrolysis are often
immobilised on the epithelial lining of the small intestine, near channel proteins

Humans do not possess an enzyme capable of digesting cellulose (cellulase) and hence it passes through the body undigested

37
Q

digestion of proteins

A

Protein digestion begins in the stomach with the release of proteases that function optimally in an acidic pH (e.g. pepsin = pH 2)

Smaller polypeptide chains enter the small intestine where they are broken down by endopeptidases released by the pancreas

These endopeptidases work optimally in neutral environments (pH ~ 7) as the pancreas neutralises the acids in the intestine

38
Q

digestion of lipids

A

Lipid breakdown occurs in the intestines, beginning with emulsification of fat globules by bile released from the gall bladder

The smaller fat droplets are then digested by lipases released from the pancreas

39
Q

digestion of nucleic acids

A

The pancreas also releases nucleases which digest nucleic acids (DNA, RNA) into smaller nucleosides

40
Q

simplified difference between the small and large intestine

A

The small intestine absorbs usable food substances (i.e. nutrients – monosaccharides, amino acids, fatty acids, vitamins, etc.)

The large intestine absorbs water and dissolved minerals (i.e. ions) from the indigestible food residues

41
Q

Features of Villi - MR SLIM

A

Microvilli – Ruffling of epithelial membrane further increases surface area

Rich blood supply – Dense capillary network rapidly transports absorbed products

Single layer epithelium – Minimises diffusion distance between lumen and blood

Lacteals – Absorbs lipids from the intestine into the lymphatic system

Intestinal glands – Exocrine pits (crypts of Lieberkuhn) release digestive juices

Membrane proteins – Facilitates transport of digested materials into epithelial cells

42
Q

benifits because of the structure of villus epithelium

A

1) tight junctions
2) microvilli
3) mitochondria
4) pinocytotic vesicles

DETAILS ON BIONINJA

43
Q

structure of the small intestine

A

Serosa – a protective outer covering composed of a layer of cells reinforced by fibrous connective tissue

Muscle layer – outer layer of longitudinal muscle (peristalsis) and inner layer of circular muscle (segmentation)

Submucosa – composed of connective tissue separating the muscle layer from the innermost mucosa

Mucosa – a highly folded inner layer which absorbs material through its surface epithelium from the intestinal lumen

44
Q

Methods of Membrane Transport Mechanisms

A

1) Secondary Active Transport
2) Facilitated Diffusion
3) Osmosis
4) Simple Diffusion

45
Q

Methods of bulk transport mechanisms

A

Endocytosis

46
Q

Endocytosis overview

A

Endocytosis involves the invagination of the plasma membrane to create an internal vesicle containing extracellular material

Vesicle formation requires the breaking and reforming of the phospholipid bilayer and hence is an energy-dependent process

In the intestines, vesicles commonly form around fluid containing dissolved materials (pinocytosis – cell ‘drinking’)

Pinocytosis allows materials to be ingested en masse and hence takes less time than shuttling via membrane proteins

47
Q

two key functions performed by digestion

A

It breaks down insoluble molecules into smaller subunits which can be readily absorbed into body tissues

It breaks down inert molecules into usable subunits which can be assimilated by cells and reassembled into new products

48
Q

starch digestion - role of pancreas

A

The pancreas serves two functions in the breakdown of starch:

It produces the enzyme amylase which is released from exocrine glands (acinar cells) into the intestinal tract
It produces the hormones insulin and glucagon which are released from endocrine glands (islets of Langerhans) into the blood

The hormones insulin and glucagon regulate the concentration of glucose in the bloodstream (controls availability to cells)

Insulin lowers blood glucose levels by increasing glycogen synthesis and storage in the liver and adipose tissues
Glucagon increases blood glucose levels by limiting the synthesis and storage of glycogen by the liver and adipose tissues

49
Q

role of villi (2)

-> line the ileum (are “projections”)

A

1) villi increase the surface area of epithelium over which absorption is carried out

2) villi absobs monomers formed by digestion as well as mineral ions and vitamins

50
Q

microvilli

A
  • cells of the villi
  • increases surface area for absorption
51
Q

Liquids that pass along ileum…

A

contain the products OF digestion, minerals and vitamins
==> these are absorbed through the wall of the ileum by the villis into the blood

52
Q

movement of “stuff” into the liver

A

the amino acids, glucose, some fatty acids, glycerol, minerals and most vitamins are ABSORBED into the CAPILLARIES and carried via the HEPATIC PORTAL VEIN to the LIVER

53
Q

lacteal (branch of the lymphatic system) (in the villis)–>

A

in each villi carries away much of the fatty acids and glycerol

absorbs liquids/lipids from the intestine into the lymphatic system

54
Q

Rich blood supply =

A

dense capillary network rapidly transports absorbed products

55
Q

Single layer epithelium = minimises diffusion distance between lumen and blood =

A

minimises diffusion distance between lumen and blood

56
Q

intestial glads =

A

exocrine pits releases digestive juices

57
Q

membrane proteins =

A

facilitates transport of digestied materials into epithelial cells

58
Q

how is the structure of the villus is related to its role in absorption of the end products of digestion

A

1) high surface area = rapid absorption of nutrients
2) good blood flow
3) linked to transport lymph vessels -> transport

59
Q

Methods of membrane transport are required to absorb different nutrients

details + examples on pages 8+9

A

1) simple diffusion
2) facilitated diffusion
3) active transport
4) endocytosis
5) osmosis

60
Q

molecules are then distributed and assimilated = it is used by the body to make…

A

new substances, cells and tissues

61
Q

Starch digestion in the small intestine ==>

A
  1. amylase
  2. Dextrinase
  3. Maltase
62
Q

amylase =

A

enzyme breaks bonds in chains of 4 or more monomers producing maltose

63
Q

Dextrinase =

A

breaks the bonds that amylase cannot deal with forming glucose monomers

64
Q

maltase =

A

digests maltose into glucose monomers

65
Q

Digested glucose is absorbed and then transported to various body tissues by (5) =

A

1) glucose is co-transported with sodium ions into the epithelial cells (of the villus)
2) glucose moves by facilitated diffusion into the lumen of the villus
3) glose then diffuses a short distance into the adjacent capillaries where it dissolves into the blood plasma
4) blood in the capillaries move to the venules then to the hepatic portal vein which transports the glucose to the liver
5) the liver absorbs excess glucose which it converts to glycogen for storage

66
Q

peristalsis

A

the involuntary constriction and relaxation of the muscles of the intestine or another canal, creating wave-like movements that push the contents of the canal forward.

67
Q

surfactants

A

a substance which tends to reduce the surface tension of a liquid in which it is dissolved.

that allow for fats/oil to immensafy (mix)

68
Q

lipase

A

a pancreatic enzyme that catalyses the breakdown of fats to fatty acids and glycerol or other alcohols + lipids

69
Q

endopeptidase

A

an enzyme which breaks peptide bonds other than terminal ones in a peptide chain (breaks down polypeptides)

70
Q

Mucosa

A

The moist, inner lining of some organs and body cavities (such as the nose, mouth, lungs, and stomach). Glands in the mucosa make mucus (a thick, slippery fluid). Also called mucous membrane.

71
Q

lacteal

A

the lymphatic vessels of the small intestine which absorb digested fats.

72
Q

dialysis tubing

A

artificial semi-permeable membrane tubing[1] used in separation techniques, that facilitates the flow of tiny molecules in solution based on differential diffusion

membrane that control the size movement of materials used in osmosis experiments

73
Q

cellulose

A

plant sugar used for storage - that cant be broken down

an insoluble substance which is the main constituent of plant cell walls and of vegetable fibres such as cotton. It is a polysaccharide consisting of chains of glucose monomers

74
Q

macromolecule

A

a molecule containing a very large number of atoms, such as a protein, nucleic acid, or synthetic polymer.

75
Q

epithelium

A

outside layer of cells

the thin tissue forming the outer layer of a body’s surface and lining the alimentary canal and other hollow structures.

the part of the epithelium derived from embryonic ectoderm and endoderm, as distinct from endothelium and mesothelium

76
Q

lumen

A

central part of the tube (surrounded by villi)

the central cavity of a tubular or other hollow structure in an organism or cell.

77
Q

Pancreas

A

A glandular organ located in the abdomen. It makes pancreatic juices, which contain enzymes that aid in digestion, and it produces several hormones, including insulin. The pancreas is surrounded by the stomach, intestines, and other organs

78
Q

stomach

A

the internal organ in which the major part of the digestion of food occurs, being (in humans and many mammals) a pear-shaped enlargement of the alimentary canal linking the oesophagus to the small intestine

79
Q

colon

A

the main part of the large intestine, which passes from the caecum to the rectum and absorbs water and electrolytes from food which has remained undigested.

last section of the large intestine

80
Q

small intestine

A

the part of the intestine that runs between the stomach and the large intestine; the duodenum, jejunum, and ileum collectively.

81
Q

liver

A

for processing food

a large lobed glandular organ in the abdomen of vertebrates, involved in many metabolic processes

82
Q

gall bladder

A

a small sac-shaped organ beneath the liver in which bile is stored after secretion by the liver and before release into the intestine.

83
Q

chyme

A

the pulpy acidic fluid which passes from the stomach to the small intestine, consisting of gastric juices and partly digested food.

IB Biology (36 decks)

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