Top Banner

of 41

How to Eat Green Stuff

Apr 05, 2018

Download

Documents

Shanai Graham
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
  • 8/2/2019 How to Eat Green Stuff

    1/41

    Animal Physiology

    Or how things happen

  • 8/2/2019 How to Eat Green Stuff

    2/41

    Class schedule ZOOL2402DATE WEEK LAB LECTURES05/03/2012 1 a) Lab test ZOOL 2401 How to eat green stuff

    b) Gut Histology and gut length12/03/2012 2

    a) Length:Weight, Proportions and energyMetabolic rate and size

    b) Lung volume, gill area How to get oxygen

    19/03/2012 3 a) Heart rate, BP and exercise. BMI How to move

    b) Metabolic rate and heat. How to be cool.25/03/2012 4 a) Data Interpretation Getting rid of stuff

    b) Urinalysis

    02/04/2012 5 a) Endocrine structures Sugar sex and nerves

    b) NIL Easter

    09/04/2012 6 a) NIL Easter Seeing it

    b) Lab test

  • 8/2/2019 How to Eat Green Stuff

    3/41

    What is Physiology?

    Physiology is the analysis of function inliving organisms

  • 8/2/2019 How to Eat Green Stuff

    4/41

    How to eat Green stuff

    Or The problems of Herbivory

  • 8/2/2019 How to Eat Green Stuff

    5/41

  • 8/2/2019 How to Eat Green Stuff

    6/41

    For the organism the balance of energy isimportant. It must minimize energy expenditurewhile maximizing energy generation.

    Ultimately energy generation occurs throughbreakdown of glucose in respiration but prior tothis process the glucose molecules must begenerated to enter into the Krebs cycle or

    glycolysis. Thus the function of digestion is to produce

    simple molecules which can be broken down toyield energy.

    This process however REQUIRES energy, so forthe organism, the energy gain must exceed theenergy lost through instigating the breakdownprocess

  • 8/2/2019 How to Eat Green Stuff

    7/41

    This is the basis of energetics-the study of energybalance in an organism.

    Basic energetics equation:

    E(In) = E(Out) +E(P). Where E(P)=Energy retainedfor production or growth.

    The equation can be expanded to:

    R=F+U+M+P

    Where :

    R = Ingested energy

    F and U = Energy losses in faeces and excretoryproducts respectively

    M = Energy lost in metabolism.

  • 8/2/2019 How to Eat Green Stuff

    8/41

    M can be further subdivided into:

    1) Energy for bodily functions

    2) Energy used for movement

    3) Energy used for digestion absorption and processingof food.

    P can be further subdivided into:

    1) Energy used in production of gametes.2) Energy used for somatic growth

    The partitioning of energy into the various

    components can be determined experimentallyand constitutes determination of the energy budget

    for the organism

  • 8/2/2019 How to Eat Green Stuff

    9/41

    Digestive difficulties with Plant

    material

    Plant cells characteristically have cell walls. These are composed of a variety of substances

    celluloses ,hemicelluloses, lignin etc.

    These structural polysaccharides are large

    molecules composed of sugar units joined byglycosidic links.

    Number one problem is that most macro-organisms (herbivores) lack the appropriate

    enzymes to break the bonds in themacromolecule and thus the cell contents arelargely resistant to digestion.

  • 8/2/2019 How to Eat Green Stuff

    10/41

    Plant Structural Compounds

  • 8/2/2019 How to Eat Green Stuff

    11/41

    Plant structural Carbohydrates

    Main compound in plant cell walls is Cellulose.

    Insoluble

    Most abundant organic chemical on Earth

    Linear

    Consists of glucopyranose units linked by 1-4 glycosidic linkages.

    Each molecule has about 3000units Cellulose molecules are aligned in parallel fashion to form microfibrils

    which are several m in diameter and between 10-20 nm in length. Highlyordered arrangement of molecules is maintained by hydrogen bondingbetween the chains.

    This ordered arrangement gives the molecule its property of insolubility

    and its great strength. Microrganisms secrete cellulases which can break the linkages but the

    released glucose is fermented in the gut of herbivorous mammals to giveshort chain fatty acids such as butyric acid which can be absorbed by theanimal in the intestine

  • 8/2/2019 How to Eat Green Stuff

    12/41

    Hemicelluloses

    Three types.

    Xylans,mannans and glucomannans

    Many have same 1-4 glycosidic backbone ascellulose but have side chains which prevents

    close packing.

    This allows some solubility

    Xylans found in seed coats

  • 8/2/2019 How to Eat Green Stuff

    13/41

    Possible solutionsPlant material decomposes once it dies.

    Decomposition is carried out by micro-

    organisms which DO possess cellulose

    digesting enzymes: cellulases.

    These micro-organisms are mainly fungi and

    bacteria.

    Possible Solution 1. Allow material to die and

    decomposition to begin and then consume

    decomposing material and decomposers.

    This solution is seen in detritivores. Very common

    in fishes.

    Possible Solution 2. Incorporate decomposers within thedigestive system to allow breakdown process to occur within digestive

    System. Symbiosis. This occurs in most terrestrial herbivores but has

    evolved in a number of different ways

  • 8/2/2019 How to Eat Green Stuff

    14/41

    Possible solution 2:Variants

    1)Many chambered stomach-Ruminants and ruminant-like animals.

    2)Digestive chamber (caecum) and enlarged gut eg Perissodactlys, Fishes.

    3) Digestive chamber (caecum) and refection eg Lagomorphs and rodents.

    Detail

    The following are organisms which possess a multichambered stomach which

    houses microorganisms:Ruminants; cows, sheep, deer, goats etc.

    Ruminant like organisms; camels, llamas, hippopotamuses

    pigs, sloths, some marsupials, langur monkey

    Importance of Ruminants

    1) Main herbivores in a number of ecosystems eg antelope in the Africansavannah.

    2)Major domestic animals in agricultural setting eg cows, sheep, goats.Source of wool milk ,meat.

  • 8/2/2019 How to Eat Green Stuff

    15/41

    Ruminant digestion

    Digestive tract greatly enlarged. Microbial digestion slow process .Fermentation. Needs ability to store large amounts of food. Feedingcontinuous. Typical capacity of cow 91 litres.

    Requires large amounts of saliva. Saliva high in bicarbonate contentnecessary to neutralise acidic pHs generated in the stomach by microbialdigestion. Main digestion products organic acids lowers pH.

    Structure of the rumen 4 chambers: rumen ,reticulum and omasum linedwith keratinised squamous epithelium. None of them produces digestiveenzymes. Abomasum normal mammalian stomach.

    house the microbial flora.

    Microbial flora consists of a wide variety of microorganisms thusequipping the animal with the ability to break down a range of structuralcompounds. Not Lignin.

    Chief fermentation end product: organic acids : acetic, proprionic, butyricetc.

    Little glucose from digestion of cellulose as this is used by microorganisms

  • 8/2/2019 How to Eat Green Stuff

    16/41

  • 8/2/2019 How to Eat Green Stuff

    17/41

    Certain microorganisms responsible for splitting proteins into amino

    acids. Mainly theses are taken up by the microorganismsthemselves. BUT microorganisms are ultimately digested as asource of protein by the ruminant.

    Ruminant microorganisms are able to utilize urea and ammonia tosynthesise protein thus increasing protein content using wasteproducts.

    Urea produced in the liver is returned to the rumen in the salivaand in the blood by diffusion from the blood. Some is converted toammonia.

    Both components are used in protein synthesis by themicroorganisms.

    Microorganisms are also responsible for the synthesis of B vitamins(particularly B12) and vitamin C.

    Microorganisms synthesise all essential amino acids. Ruminants

    able to survive irrespective of protein quality Both these abilities allow ruminants to survive on poor quality plant

    material or during times of drought.

  • 8/2/2019 How to Eat Green Stuff

    18/41

  • 8/2/2019 How to Eat Green Stuff

    19/41

    Summary of processes in ruminant

    stomach

  • 8/2/2019 How to Eat Green Stuff

    20/41

    Description of digestive process

    1. Food passes into rumen/reticulum where it is churnedto a fine consistency. Food is fermented here.

    2. Food returned to mouth via contractions of rumen .

    3. Chewed again

    4. Compression in omasum. Removal of water (up to70%).

    5. Digestion with enzymes and gastric juice inabomasum

    6. Food may be returned to mouth for further chewingprior to passing directly to the intestine whereabsorption occurs.

  • 8/2/2019 How to Eat Green Stuff

    21/41

    Energy Budget

    Energy Budget :

    Percentage of original intake

    Free fatty acids 20

    Digested by normal processes 25

    Bacteria digested by normal processes 15Subtotal of utilizable energy 60

    Faeces 25

    Gas and Heat 15Subtotal of energy lost 40

  • 8/2/2019 How to Eat Green Stuff

    22/41

    Fermentation products major source of

    energy.

    Approximately 70% of energy needs of a cow

    met from organic acids.

    Large quantity of energy lost as methane

    gas(>10% of daily digested food energy)

    eg Cow fed 5kg hay produces 191litres of

    methane

  • 8/2/2019 How to Eat Green Stuff

    23/41

    Caecum

    Can be defined as a blind ending diverticulum in the digestive tractwhere microbial digestion/fermentation takes place. Usually foundat the junction of the small and large intestines

    Found in a number of groups: perissodactyls (horses, zebras,rhinoceroses), elephants and hyraxes, lagomorphs and rodents and

    dugongs are the mammal groups. Also Green turtles, Iguanas, and some birds eg willow ptarmigan

    feeds on leaves and twigs. Derives 30% of energy fromfermentation.

    Green turtles feed on sea grasses. 90% of cellulose digested byfermentation.

    Common iguana -fermentation in hind gut. Captive rearedindividuals need to acquire correct flora from feeding on the faecesof wild individuals

  • 8/2/2019 How to Eat Green Stuff

    24/41

    Advantages of ruminants

    Location of fermentation chamber at anterior of gutallows digested products to pass through smallintestine and be subjected to further digestion.

    Regurgitation is possible. Finer breakdown of plantmaterial. Compare cow and horse faeces.

    Recycling of urea allows nitrogen that would be lost tobe utilised. Allows ruminants to survive on low-gradefood Also seen in macropode marsupials eg kangeroos.

    Saftey. Anmal is able to continue processing food whichis stored in the digestive tract in safety. Less exposureto predators

  • 8/2/2019 How to Eat Green Stuff

    25/41

    Sloth Stomach (Bradypus)

  • 8/2/2019 How to Eat Green Stuff

    26/41

    Caecum plus refection

    With a caecum alone much of the material which is digested by themicroorganisms is lost as it is poorly absorbed or is not subject to furtherdigestion.

    Solution pass material through the digestive system twice. This is effectedby lagomorphs and rodents and is known as corophagy or refection.

    If prevented from this rats develop vitamin deficiency and a 15-25%growth rate deficiency.

    Similarly in rabbits-poor protein utilization and nitrogen retention.

    In rabbits reingested faeces not masticated but pass to fundus of stomachand are stored there covered by a membrane . Fermentation maycontinue.

    Rodents possibly masticate reingested faeces.

    Other mammals which practice corophagy: prosimians, shrews, somemarsupials.

    Shrews are insectivorous and use the process to assist in breakdown ofchitin which is a nitrogen containing polysaccharide

  • 8/2/2019 How to Eat Green Stuff

    27/41

    Rabbit Stomach

  • 8/2/2019 How to Eat Green Stuff

    28/41

    Herbivory in Fishes. Many fishes eat plant material.

    There are a number of strategies employed:

    Detritivory. This is particularly common in freshwater fishes

    which rely on bacteria in the environment to digest the

    structural carbohydrates. Many such fishes have pyloric caeca

    which are a site of absorption in detritivorous fishes

    Long intestine. Generally fishes which digest plant material

    have a much longer intestine relative to body length than

    fishes which feed on animal material. Many of these fishes

    lack a stomach, e.g. Scaridae, (parrot fishes), Cyprinidae(carps).

    Ratio of intestine length to body length:

    Carnivores:033-075. Herbivores:2-20. Detritivores > 5.

  • 8/2/2019 How to Eat Green Stuff

    29/41

    Pyloric Caeca in Teleost fishes

  • 8/2/2019 How to Eat Green Stuff

    30/41

    Gizzard-like stomach. Some fishes employ a grinding

    mechanism to mechanically rupture the cell walls of plant

    material e.g. Mugilidae (grey mullets) which have a muscular

    gizzard like stomach Caecum The family Kyphosidae which is found in Australia

    have a caecum like structure with microflora: ciliates and

    bacteria, which is used for fermentation and produces short-

    chain fatty acids as a digestion product. Teeth Many fishes have grinding molariform teeth in the

    mouth but the most common mechanism is the presence of

    pharyngeal teeth. These are located in the pharynx

    (surprisingly!) and give a very efficient grinding mechanism to

    rupture the cell walls of plant material. Seen in Cyprinidae and

    Cichlidae. This process is known as Trituration

  • 8/2/2019 How to Eat Green Stuff

    31/41

    Pharyngeal Teeth of Teleost fish

    Low pH in stomach Plant cells walls can also

  • 8/2/2019 How to Eat Green Stuff

    32/41

    Low pH in stomach. Plant cells walls can also

    be ruptured by exposing them to low pH

    (approximately 1 or 1.5). This is seen in a

    variety of plant eating fishes e.g. Cichlidae.This process is known as Lysis.

    Most herbivorous fishes use a combination of

    strategies

  • 8/2/2019 How to Eat Green Stuff

    33/41

    Humans

    Humans are defined as omnivores they however havethe ability to digest plant material.

    This takes place in the caecum by means offermentation.

    The constraints in terms of energy yield are the sameas for other animals with a caecum.

    Dietary fibre is the edible parts of plants which areresistant to digestion and absorption in the humanintestine with complete or partial fermentation in thelarge intestine.

    Physiological benefits: 1) laxation, 2) attenuation of blood glucose and/or cholesterol.

  • 8/2/2019 How to Eat Green Stuff

    34/41

    Fibre in the human diet 1

    1) Significantly lower incidence of constipation,diverticulosis and digestive cancer associated withhigh fibre diets. Mechanism. Bulk due to fibre improves the

    musculature of the intestinal wall and lessens thetime that potential carcinogens are held in theintestine

    Butyric acid derived from fermentation ofcellulose is toxic to tumor cells, inducingapoptosis.

    Short chain fatty acids promote the growth ofbifidobacteria which prevent the establishment ofnondesirable intestinal flora

  • 8/2/2019 How to Eat Green Stuff

    35/41

    Fibre in the human diet 2

    2) glucans are another type of structural polysaccharide which aresoluble due to the presence of a 1-4 glycosidic backbone alongwith 1-3 side chains which confer solubility. Oat porridge.

    Beneficial as they lower the level of blood cholesterol and reducethe incidence of heart disease. Mechanism. Viscous nature impedes the resorption of cholesterol and bile

    acids in the intestine thereby placing a drain on the bodys cholesterolsynthesis.

    In general structural carbohydrates help

    decrease the glycaemic index of food thus slowing

    down the uptake of glucose. This has particular benefits

    for controlling blood glucose levels.Gums (soluble structural carbohydrates)probably bind to bile acids resulting

    in more of them being passed out in the faeces and thus placing a drain on

    the synthesis and metabolism of cholesterol

  • 8/2/2019 How to Eat Green Stuff

    36/41

    Bile acids and Cholesterol

    Absorption of lipids occurs in the small intestine. The process is aided by bile salts.

    Examples of bile salts are sodium glycholate and taurocholate. These are derived from cholesterol in the liver

    Bile salts are produced by the liver and pass along the bileduct where they are retained at the sphincter of Oddi. Thebile is also concentrated at this point by active transport ofNa+ ions

    Release is stimulated by a variety of factors: presence of fattyacids in the intestine and the gastric hormone CCK

    Bile salts combine with digested food products to form watersoluble micelles which enter the epithelial cells.

    .

  • 8/2/2019 How to Eat Green Stuff

    37/41

    Recycling of bile salts

    The micelles which enter the epithelial cells areresynthesised into triacylglcerols at the ER and thesebecome part of droplets called chylomicrons.

    The chylomicrons enter the lacteals and eventually the

    veins. Most are stored as adipose tissue with only smallamounts being oxidized for energy at this time

    Bile salts are resorbed from the intestine and returnedto the liver.

    This occurs by means of the Enterohepatic circulation.

    Any process that slows resorbtion of bile salts isthought to be beneficial in lowering the levels ofcholesterol

  • 8/2/2019 How to Eat Green Stuff

    38/41

  • 8/2/2019 How to Eat Green Stuff

    39/41

    Invertebrate digestion of plant

    structural compounds

    Plant material is digested by a number ofinvertebrates.

    Obvious examples are : snails and silverfish.

    Termites live exclusively on wood and rely onTrichomonas in the hind gut to provide cellulases.

    Trichomonas is a flagellate which exists only inthe anaerobic conditions of the hind gut. If the

    symbiont is removed the termite is unable tosurvive .Nitrogen fixing bacteria are also presentin the hind gut of termites

  • 8/2/2019 How to Eat Green Stuff

    40/41

    Plant defences and their physiological

    effects

    Many plants have chemical defence mechanisms

    to prevent them from being eaten by herbivores.

    Some examples follow:

    Alkaloids-affect CNS, opium, morphine, nicotine

    Glycosides. Breakdown leads to toxic compounds

    eg cyanide from cassava.

    Enzyme inhibitors e.g. trypsin inhibitors in soyabeans. Low protein utilization of nuts, beans.

    Heat sensitive.

  • 8/2/2019 How to Eat Green Stuff

    41/41

    Plant defences and their physiological

    effects

    Cruciferae eg cabbage. Compounds which

    suppress thyroid function. May lead to goitre if

    excess in diet in combination with poor nutrition.

    Compounds affecting reproduction. Mimics ofjuvenile hormone in insects-certain trees.

    Oestrogen mimics particularly abundant in plants

    of the pea family during arid years thus reducingreproductive success of herbivores. Also soya.