Human Physiology - 6.1 Digestion and Absorption

Question 1

the two groups of organs which comprise the human digestive system

Answer 1

1. Alimentary canal
2. Accessory organs

Question 2

alimentary canal

Answer 2

consists of organs through which food actually passes

(oesophagus, stomach, small and large intestine)

Question 3

Accessory organs

Answer 3

aid in digestion but do not actually transfer food

(salivary glands, pancreas, liver, gall bladder)

Question 4

The role of the: mouth

Answer 4

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

Question 5

The role of the: oespohagus

Answer 5

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

Question 6

The role of the: stomach

Answer 6

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

Question 7

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

Answer 7

sphincter muscles

Question 8

The role of the: small intestine

Answer 8

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

Question 9

the 3 regions of the small intestine

Answer 9

1) duodenum
2) jejunum
3) longer ileum

Question 10

The role of the: Pancreas

Answer 10

secretes the enzymes amylase, lipase and an endopeptidase

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

Question 11

The role of the: liver

Answer 11

produces bile

Question 12

role of bile (liver)

Answer 12

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)

Question 13

The role of the: Gall Bladder

Answer 13

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

Question 14

The role of the: large intestine

Answer 14

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

Question 15

what is included in the large intestine

Answer 15

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

Question 16

Mechanical Digestion - understanding

Answer 16

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

Question 17

stats about the digestive system:

Answer 17

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

Question 18

Mechanical digestion - chewing

Answer 18

• 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

Question 19

what is a bolus?

Answer 19

it is a lump of food

Question 20

epiglottis’ interaction with the bolus

+

uvula’s interaction with the bolus

Answer 20

• epiglottis prevents the bolus from entering the trachea
• uvula prevents the bolus from entering the nasal cavity

Question 21

Mechanical Digestion: Peristalsis

Answer 21

= 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

Question 22

choaking =

Answer 22

when you eat something too big and peristalsis can not occour

Question 23

Mechanical Digestion: Segmentation

Answer 23

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

Question 24

segmentation contractions in the stomach =

Answer 24

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

Question 25

Chemical digestion - understandings

Answer 25

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

Question 26

the breakdown of large molecules in the human body = digestion

Answer 26

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

Question 27

protein goes through proteases/peptidases to form:

Answer 27

amino acids

Question 28

polysaccharides and disaccharides goes through amylases to form:

Answer 28

monosaccharides

Question 29

nucleic acid goes through nucleases to form:

Answer 29

nucleotides

Question 30

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

Answer 30

glycerol fatty acids

Question 31

cellulose/fibre - and NOT being broken down

Answer 31

cellulose remains undigested and is passed from the body in faeces

Question 32

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

Answer 32

4 and 5

Question 33

What is the: villi in the small intestine

Answer 33

they help in the absorption of nutrients by increasing the surface area for absorption so that the max amount of substance can be absorbed

Question 34

consequences of celiac disease for absorption of digested nutrients

Answer 34

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

Question 35

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

Answer 35

1) enzymes 2) acids 3) bile

Question 36

digestion of carbohydrates

Answer 36

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

Question 37

digestion of proteins

Answer 37

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

Question 38

digestion of lipids

Answer 38

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

Question 39

digestion of nucleic acids

Answer 39

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

Question 40

simplified difference between the small and large intestine

Answer 40

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

Question 41

Features of Villi - MR SLIM

Answer 41

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

Question 42

benifits because of the structure of villus epithelium

Answer 42

1) tight junctions 2) microvilli 3) mitochondria 4) pinocytotic vesicles DETAILS ON BIONINJA

Question 43

structure of the small intestine

Answer 43

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

Question 44

Methods of Membrane Transport Mechanisms

Answer 44

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

Question 45

Methods of bulk transport mechanisms

Answer 45

Endocytosis

Question 46

Endocytosis overview

Answer 46

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

Question 47

two key functions performed by digestion

Answer 47

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

Question 48

starch digestion - role of pancreas

Answer 48

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

Question 49

role of villi (2) -> line the ileum (are "projections")

Answer 49

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

Question 50

microvilli

Answer 50

- cells of the villi - increases surface area for absorption

Question 51

Liquids that pass along ileum...

Answer 51

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

Question 52

movement of "stuff" into the liver

Answer 52

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

Question 53

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

Answer 53

in each villi carries away much of the fatty acids and glycerol absorbs liquids/lipids from the intestine into the lymphatic system

Question 54

Rich blood supply =

Answer 54

dense capillary network rapidly transports absorbed products

Question 55

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

Answer 55

minimises diffusion distance between lumen and blood

Question 56

intestial glads =

Answer 56

exocrine pits releases digestive juices

Question 57

membrane proteins =

Answer 57

facilitates transport of digestied materials into epithelial cells

Question 58

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

Answer 58

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

Question 59

Methods of membrane transport are required to absorb different nutrients details + examples on pages 8+9

Answer 59

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

Question 60

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

Answer 60

new substances, cells and tissues

Question 61

Starch digestion in the small intestine ==>

Answer 61

1. amylase 2. Dextrinase 3. Maltase

Question 62

amylase =

Answer 62

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

Question 63

Dextrinase =

Answer 63

breaks the bonds that amylase cannot deal with forming glucose monomers

Question 64

maltase =

Answer 64

digests maltose into glucose monomers

Question 65

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

Answer 65

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

Question 66

peristalsis

Answer 66

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.

Question 67

surfactants

Answer 67

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)

Question 68

lipase

Answer 68

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

Question 69

endopeptidase

Answer 69

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

Question 70

Mucosa

Answer 70

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.

Question 71

lacteal

Answer 71

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

Question 72

dialysis tubing

Answer 72

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

Question 73

cellulose

Answer 73

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

Question 74

macromolecule

Answer 74

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

Question 75

epithelium

Answer 75

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

Question 76

lumen

Answer 76

central part of the tube (surrounded by villi) the central cavity of a tubular or other hollow structure in an organism or cell.

Question 77

Pancreas

Answer 77

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

Question 78

stomach

Answer 78

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

Question 79

colon

Answer 79

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

Question 80

small intestine

Answer 80

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

Question 81

liver

Answer 81

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

Question 82

gall bladder

Answer 82

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

Question 83

chyme

Answer 83

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