Digestion

Question 1

what is meant by the term essential nutrients

Answer 1

nutrients which cant be manufactured by the body and must be obtained through the body, different animals have different essential nutrients
Humans
9 amino acids
2 fatty acids
13 vitamins
15 different minerals

Question 2

what are the different types of essential nutrients obtained from diet and what are their uses

Answer 2

1) carbohydrates = energy production
2) proteins = enzymes, cellular components
3) lipids = cell membranes and other structures
4) vitamins= cofactors in enzymes such as copper and zinc

Question 3

what are the different types of feeding strategies

Answer 3

1) filter feeders such as whales and daphnia
= unselective filtering anything from the water column around them

2) detrivores such as earthworms whcih take in dead matter

3) fluid feeders such as humming birds and mosquitos which have specalised digestive systems

4) carnivores which eat meat

5) omnivores which eat meat and vegetation

6) herbivores which eat vegetation

Question 4

the main function of the digestive system is to take nutrients from the external environment into the bod, what are the four main processes of doing this

Answer 4

1) motility = propelling digestive material through the system using muscles, occurs at different rates in the body

2) secretion = large number of enzymes and molecules depending on animal and area of the body

3) digestion= the breakdown of complex molecules by hydrolysis into more simple molecules which can be absorbed

4) absorption= the uptake of simple units into the small intestine using specialised epithelial transporters

Question 5

outline the evolution of the diversity of digestive systems amongst different species

Answer 5

• the most simple system seen in jellyfish and corals is a simple gastrocavity with on enterancr and exit where digestion and absorption take place with specalsied cells lining the cavity
• majoirty of systems have a long tube running from mouth to anus with some differences e.g.
  chicken = crop for storage of mateiral and paired cecum
• has evolution continued cell specialsition become more complex e.g. development of accessory organs such as pancrease which secrete digestive enznymes compared to simpler individuals with no specalsied organs

Question 6

outline the digestive system of a generalised insect

Answer 6

divided into three sections
1) foregut which takes in food and grinds and stores it

2) midgut which is the stomach and intestine equivilant where digestion and absorption occur

3) hindgut which stores excreta and fluid reabsorption

Question 7

how is the vertebrate digestive system regulated

Answer 7

by the enteric nervous system which is regulated by a series of receptors on digestive systems such as stretch, PH or osmotic receptors, influced by three main factors

1) the intrinsic nerve plexus made up of the myenteric (muscular movements) and submucous (secretions) plexus

2) extrinsic nerves controlled by the automatic (parasympathetic) nervous system

3) gastrointestinal hormones e.g. grhelin, leptins and growth hormones

Question 8

outline the function of the mouth in digestion

Answer 8

differs and specialised depending on the species and type of food being eaten
FUNCTION= grind and mix food with saliva, starting the digestive process, lubricating the bolus to travel to stomach through the oesophagus

Question 9

outline the role of the oesophagus in digestion

Answer 9

goes from the mouth to the stomach via peristaltic muscle contractions known as swollowing
some species have a crop for the storage of food

Question 10

outline the role of the stomach or midgut in digestion

Answer 10

true stomach = an organ which secretes acids
differs depending on species e,g, ruminnats have four stomachs, birds have divided stomach into gizzard for grinding and glandular for secretions, humans have monogastric stomach broken down into three sections

Question 11

what are the three sections a human stomach is divided into

Answer 11

1) Fundus = storage of chime (name of food once out the oesophagus)
2) Body = where food is circulated and mixed with hydrochloric acid
3) Antrum= stores food before passing into small intestine

Question 12

what are the different gastric cells found in the stomach and their functions

Answer 12

1) parietal cells = secrete hydrochloric acid and intrinstic factor (allows absoptino of vitamins)

2) chief cells = secrete only digestive enzyme in stomach called pepsinogen in its inactive for to prevent self digestion

3) mucus cells which produce alkaline mucus for protection from acidic environment

4)endocrine/paracrine secretory cells which secrete histamine and gastrin promoting Hcl and somtaosin which has a negative influence on Hcl

Question 13

how do gastric gland cells protect themselves in the stomach

Answer 13

stomach has infoldings making pits where cells sit and mucus secreting cells secret alkaline mucus to surround them and counteract acidic conditions

Question 14

what are the two accessory organs and their functions in the digestive system

Answer 14

1) liver = apart of the biliary system which produces bile slats, cholesterol and lepithin which emulsify lipids for absorption
2) pancreas= endocrine portion which contains islets of Langerhans specialised to produce protleytic enzymes and exocrine portion made u of duct cells and acinar cells

Question 15

what is the role of actinar cells and duct cells in the pancreas accessory organ

Answer 15

A= secrete proteylitic enzymes trypisonogen, chymotryipsinogen and procarboxidase which are converted into their active form by HCL

D= secretes alkaline secretions which envelop different enzymes neutralsing acidic conditions in the small intestine

Question 16

what organs make up the biliary system and outline how it is involved in the emulsification of lipids

Answer 16

liver, gall bladder and ducts
forms bile which emulsifies fats by
1) fats are hydrophobic and bile salts have charges which repel each other
2) slats move into fats and break them apart into smaller droplets called micellars
3) micellars are a combination of fats, bile salts, cholesterol (makes up the core) and lepithin which is a phospholipid stabilising the micellar

Question 17

outline the role of the small intestine in digestion

Answer 17

receives chime from the stomach and secretions from the pancreases and liver so is main site for digestion and absorptions

Question 18

outline how the small intestine is structured to perform its job in digestion

Answer 18

1) highly muscularised which allow contarctio0ns to mix chime with digestive enzymes and bile
2) large surface area with many infolds called villi all of which have a brush border or microvilli for absoption

Question 19

outline how lipids are absorbed in the small intestine

Answer 19

micelles able to move freely into the cell through burshborder membranes

micellar breaks down forming a larger triglyceride which aggregates with other molecules before being coated with glycoprotein produced by the ER

this makes the molecule water soluble and is now known as a chylomicron which is taken up by the lymphatic system to the liver

Question 20

what occurs in the liver after absorption in the small intestine

Answer 20

all nutrients are taken from the intestine to the liver by the hepatic portal vien where they are detoxified by metabolic processing

Question 21

outline the role of the large intestine or hindgut in digestion

Answer 21

vaires in different animals and feeding stratergies
e.g.
rabbit = large cecum where fermentation occurs

humans = reduced ceum and fermentation occurs in appendix

main function= water reabsorption and faeces formation

Question 22

how does the large intestine differ between carnivores and herbivores

Answer 22

C= enlarged stomach to swallow prey items whole and simple, small intesine as meat is easier to digest

H = larger intestine to allow more time for fermentation, differs depending on type of herbivore
1) small hindgut fermenters = enlarged cecum

2) large hindgut fermenters = no enlarged cecum instead larger intestine as this is where fermentation occurs

3) foregut fermenters = ruminants which have a complex stomach were fermentation occurs

Question 23

outline digestion in ruminants

Answer 23

made up of four chambers
1) rumen = fermentation of cellulose material which circulates and returned to mouth as cud before rechewed

2) omasum which is were water absorption occurs

3) abomasum which is the true stomach

Question 24

outline digestion in nectar feeding birds

Answer 24

has the simplest structure of all animals with various other adaptations such as extended beaks and long tounges

reduced intestinal area but presence of specialised enzyme (sucrose hydrolysis enzyme) which allows rapid digestion and absorption of enzymes