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Animal nutrition
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The modes of nutrition
Nutrition refers to all the processes by which organisms obtain and use the nutrients required for maintaining life.
Nutrients are substances which organisms need for releasing energy, for growth and repair, and to sustain all life processes
The different ways that organisms obtain and use nutrients are called the modes of nutrition.
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Homeostasis - metabolism
All of these nutritional modes are found among prokaryotes!Eukaryotes are not as diverse in their nutritional modes.
Nutrition ModeEnergy Source
Carbon Source
Photoautotroph Light CO2
ChemoautotrophInorganic
chemCO2
Photoheterotroph LightOrganic chem
ChemoheterotrophOrganic chem
Organic chem
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Photoautotrophs - photosynthesis Ancient pathway, but not universal Cyanobacteria, Algae, Plants
light
CO2 + H2O O2 + CH2Ochlorophyll
Purple-sulfur bacterialight
CO2 + H2S Ss + CH2Ochlorophyll
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Chemoautotrophs 1. Nitrifying bacteria which derive energy
by oxidizing ammonia into nitrates. Eg: Nitrosomonas, Nitrobacter.
2. Sulphur bacteria which derive energy by oxidising hydrogen sulphide to sulphur. Eg: Thiobacillus, Beggiatoa.
3. Iron Bacteria which derive energy by oxidising ferrous ions into ferric form. Eg: Ferrobacillus, Gallionella.
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Nitrosomonas - internal membranes use NH4
+ electrons in an ETS to produce ATP ATP and protons used to reduce CO2 to CH2O
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Rhizobium needs anaerobic conditions to convert N2 into NH4+
Legumes produce heme based molecules and rapid respiration to eliminate oxygen from root nodules that house the bacterium“symbiosis”
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Photoheterotrophs - strange
Bacteria: Rhodospirillum, Rhodomicrobium Light
C2H4O2- 2 CH2O
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Chemoheterotrophs - common!
Escherichia coli and most eukaryotes…even plants!
CH2O + O2 CO2 + H2O + ATP
Carbohydrate, etc. provides boththe energy source
andthe carbon source
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Chemoheterotrophy Aerobic Respiration
Glycolysis carbohydrate to pyruvate (in cytosol!) Citric Acid Cycle pyruvate to carbon dioxide (in cytosol or
matrix) Electron Transport and Oxidative Phosphorylation (in
mesosomes or cristae)
CH2O + O2 CO2 + H2O Anaerobic Fermentation
Glycolysis to pyruvate (in cytosol) Fermentive step(s) to return NAD+ to glycolysis (in cytosol)
C6H12O6 C3H3O3- C2H5OH + CO2
C6H12O6 C3H3O3- H3CCHOHCOO-
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Autotrophic nutrition
Chemoheterotrophic nutrition
Holozoic nutrition
Parasitic nutrition
Saprophytic nutrition
Herbivores
Carnivores
Omnivores
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Heterotrophic nutrition consumes complex organic food material which originates from autotrophic organisms.
There are several forms of heterotrophic nutrition:
1. Holozoic nutrition 2. Saprophytic nutrition 3. Parasitic nutrition 4. Mutualism 5. Commensalism
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Intracellular Digestion Lysosomes fuse with food vacuoles Digestion occurs within the cell Sponges only digest food
intracellularly
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Extracellular Digestion Breakdown of food outside of cells Gastrovascular cavities serve as
digestive sacs Enzymes in cavity begin extracellular
digestion After absorption, digestion is completed
intracellularly Animals with alimentary canals organize
digestion in stepwise fashion
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Saprophytes
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Saprophytes saprophytes obtain food from dead
organic matter, e.g. bacteria and fungi
Mucor is a bread mould (fungus) which depends on bread for food; hyphae: filaments mycelium: colony of filaments
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Nutrition - hyphae (rhizoid) go into bread; produce digestive enzymes to break
down complex organic substances in bread into simple soluble compounds for absorption
Extracellular digestion: digestion outside the cell
Importance of saprophytism: dead organisms are broken down to
recycle materials
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rostellumhook
sucker
immature proglottis
Tapeworm1. Structure of a tapeworm flat, long, ribbon like, with many (1000)
segments head with hooks & suckers for attachment
onto the host’s intestinal wall each segment contains both male & female
reproductive organs (bisexual) for self-fertilization
2. Life cycle Primary host - man; Secondary host - pig, for dispersal & infection
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3. Adaptation of tapeworm to the parasitic mode of life in the ileum
hooks & suckers for attaching itself onto the intestinal wall of host
reproductive organs are well developed;
bisexual for self-fertilization numerous eggs are produced to increase the chances of survival of the species
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no digestive system is needed; absorption of digested food by
diffusion through the body surface which is long & flattened to increase the surface area for absorption of digested food
can undergo anaerobic (no O2) respiration in the intestine
body is covered by a thick cuticle and secretes anti-enzymes to protect itself against the digestive juice of host
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4. Effect on host host loses weight & becomes weak because
tapeworm absorbs his digested food hooks & suckers damage the intestinal wall of
host
5. Means to get rid of tapeworm take in drugs pork should be inspected by government
before selling; pork should be thoroughly cooked before
eating good sewage system so that pigs do not get
in contact with human faeces
2007 Paper II Q.5 (a)
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Mineral Nutrition in plants
Plants need certain nutrients. A deficiency in any one of them will cause the plant to be impaired in growth and other functions.
1. C, H, and O are the most abundant elements in plants. They are obtained from water from the soil and CO2 in the air (of course).
2. Other essential elements have historically been grouped as macronutrients and micronutrients. a. Macronutrients are needed in somewhat higher amounts, and make up at least 0.1% of the dry weight of most plants, although this can vary among plants and among tissues within plants.b. Elements needed in smaller amounts are known as micronutrients.
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Advantages in hydroponics
no weeds, no pests.
The necessary growth elements are readily available.
Use less space
Possible to automate
can grow crops in greenhouse
allow precise water and nutrient application
2007 Paper II Q.5 (a)
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3. Holozoic nutrition – involves the consumption of complex (solid) food which is broken down inside the organism into simple molecules which are then absorbed,
e.g. most animals
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20 primary teeth (deciduous (“falling off”) teeth) which appear during embryonic development Are the temporary teeth of primary dentition Are also known as primary teeth, milk teeth, baby
teeth 32 teeth of adult secondary dentition, or
permanent dentition
Eruption of teeth
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Teeth
Figure 24.8a, b
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Primary and Secondary Teeth
A). Primary teeth, with the age of eruption given in months. (B). The adult teeth, with the age of eruption given in years.
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Carnivorous adaptations of mammalsFood is chiefly meat which is a more
'nutritional' than plant food. Adaptations concern modifications to the jaw & its dentition:
1. Incisors are sharp and are used for nipping & biting
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2. Canines are long & pointed; used for killing prey and tearing flesh from body3. Carnassial teeth are particularly large for crushing
bones4. Teeth of upper jaw tend to overlap those of the
lower jaw for slicing meat like two blades of a pair of scissors
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5. Jaw muscles are well developed & powerful to grip prey firmly & crushing bones
6. No lateral jaw movement which might lead to dislocation of the jaw
7. Vertical movement of the jaw is large to allow a wide gap for capturing & killing prey
8. The alimentary canal is short, i.e. meat is relatively easy to be digested
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Adaptations to particular dietsHerbivorous adaptations of mammals, e.g.
deer1. A horny pad replaces the upper incisors
& canines 2. Diastema - a gap to separate newly
nibbled food from those chewing at the back
Skull of deer
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Dental formula of a sheep : 0033 31233. Cheek teeth with ridged surfaces
because of differential wearing of enamel and dentine
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4. Jaws can move vertically & laterally - for more efficient grinding by teeth5. Teeth have open roots - teeth grow continuously throughout life to
replace wearing by constant grinding activity
6. Stomach is divided into a number of chambers with micro-organisms to secreted cellulase for the digestion of cellulose (ruminants). Regurgitation of food from stomach to mouth before passing into the remaining stomach compartments
7. The alimentary canal is relatively long because the digestion of plant material is difficult
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Comparison of herbivorous and carnivorous adaptations in mammals
Herbivores Carnivores Incisors sharp, chisel-shaped for cutting or gnawing (bite until off)
Incisors sharp, sometimes pointed, for nipping (to hold) & biting
Upper incisors sometimes absent
…never absent
Canines, if present, small & incisor-like
Canines long & pointed for piercing & tearing
Diastema present …absent
Molars & premolars flattened with ridges of enamel for grinding food
…have pointed cusps for shearing food
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Comparison of herbivorous and carnivorous adaptations in mammals
Herbivores Carnivores
Carnassial teeth absent Carnassial teeth: last upper premolars & first molars
Open pulp cavity for continuous teeth growth to compensate for wearing
Closed cavity with no growth when grow to full size
Teeth of upper jaw meet those of lower jaw end on to allow grinding of food
Teeth of upper jaw slide past outside of lower jaw: shear food
Lateral movement of lower jaw aids grinding of food
No such movement to avoid dislocation of the lower jaw
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Comparison of herbivorous and carnivorous adaptations in mammals
Herbivores Carnivores
Jaw muscles relatively small
….relatively large
Less well developed processes for muscle attachment
Well developed ….
Specialized stomach/caecum & appendix to accommodate symbiotic cellulose digesting micro-organisms
No such adaptation;Caecum & appendix small
Relatively long alimentary canal
…short alimentary canal
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Five stages of Food Processing
1. Ingestion2. Digestion (enzymatic hydrolysis)3. Absorption4. Assimiation5. Elimination
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Principles of Digestion Mechanical breakdown of food has
the effect of giving the food a large surface area which aids later digestion.
The food must be made small enough to pass through cell membranes. Thus chemical digestion with the aid of enzymes occurs.
amylase - breaks down starch into maltose
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Mucosa lines digestive tract (mucous epithelium) Moistened by glandular secretions Lamina propria and epithelium form mucosa
Submucosa Layer of dense irregular connective tissue
Muscularis externa Smooth muscle arranged in circular and longitudinal layersSystem (ENS)
Serosa Along most portions of the digestive tract inside the peritoneal cavity, the
muscularis externa is covered by a serous membrane known as the serosa
Histological organization of the digestive tract
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The Structure of the Digestive Tract
http://visualhistology.net/products/atlas/VHA_Chpt13_The_Alimentary_Canal.html
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Mouth
Mechanical digestion: the act of chewing Carbohydrate digestion begins here Saliva moistens food and contains the
enzyme Salivary Amylase – breaks down complex carbs into simple sugars
Chemical Digestion: enzymes breaking down carbohydrates
Ball of moistened, partially digested food, known as the “BOLUS”, moves into the esophagus
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Swallowing and peristalsis- pharynx leads to both trachea &
oesophagus- when swallowing food, epiglottis closes
entrance to trachea to prevent food going into lungs
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Carries solids and liquids from the pharynx to the stomach Passes through esophageal hiatus in diaphragm
The wall of the esophagus contains mucosal, submucosal, and muscularis layers
The esophagus
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Distinctive features of the esophageal wall include Nonkeratinized, stratified squamous epithelium Folded mucosa and submucosa
• Mucous secretions by esophageal glands A muscularis with both smooth and skeletal
muscle portions Lacks serosa
• Anchored by an adventitia (superficial layer of connective tissue surrounding an internal organ; fibers are continuous with those of surrounding tissues, providing support and stabilization)
Histology of the esophagus
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The Esophagus
A). Transverse cross section through the esophagus. (B). The esophageal mucosa (C). A color enhanced SEM of the transition between the esophageal and gastric mucosae at the lower esophageal sphincter.
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Peristalsis - longitudinal & circular muscles contract & relax alternately to drive food down oesophagus, small intestine, large intestine & out of the anus as faeces
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Stomach contractions: blend food and propel forward
Stomach Contraction
Direction: from lower esophageal sphincter to pyloric sphincter
Chyme: result of mixing, affects hormone secretions regulating peristalsis and emptying of stomach
58Figure 14.7Slide 14.9ACopyright © 2001 Benjamin Cummings, an imprint of Addison Wesley Longman, Inc.
Structure of the Stomach Wall
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Lining of ileum
TS of ileum showing villi
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Duodenum Brunner's glands secrete mucus and
sodium hydrogen carbonate
Enzymes are produced by the breakdown of cells at the tips of the villi
1. Mucus – lubricate and prevent autolysis 2. Mineral salts (NaHCO3) - produced by the Brunner’s glands to
neutralize the acid chyme and provide a suitable pH for intestinal enzymes
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Bile juice A complex green fluid produced by the liver,
stored in the gall bladder, It contains no chemical enzymes but two
important substances for digestion: 1. Sodium hydrogen carbonate - help to neutralize the acid chyme from the
stomach and so create a more neutral pH for the enzymes of the small intestine
2. Bile salts - They emulsify fats into minute droplets - This is a physical digestion which increases
the surface area for pancreatic lipase to act on
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Large Intestine Unabsorbed material moves through large
intestine, where water and salt are absorbed
This removal of liquid forms solid-like feces
Feces is stored in the rectum Feces is removed from the body, via the
anus, by the process of ELIMINATION
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Cecum
Lies below junction with small intestine
Contains appendix
Colon
Includes ascending colon, transverse colon, descending colon
Rectum
Last 20 cm of the large intestine
Anus
Where defecation (expulsion of feces) occurs
Obligate anaerobic (die in presence of oxygen) bacteria inhabit colonBreak down indigestible material and produce vitamins & other molecules used by our bodies
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http://www.youtube.com/watch?v=IRiwXMeKoGk&feature=grec_index
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Chemistry of Digestion Digestion is defined as the
breakdown of nutrients We consume: Proteins Carbohydrates Fats These are broken down into their
simplest forms
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Overview
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Salivary amylase- digest starch into maltose Pancreatic amylase Carbohydrases in small intestine - consisting of maltase, lactase, and
sucrase, etc., to complete the digestion of sugars into simple sugars
Slide 14.9BCopyright © 2001 Benjamin Cummings, an imprint of Addison Wesley Longman, Inc.
Digestion of carbohydrates
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Gastric juice: specific cells secrete
Hydrochloric acid (from chief cells): produces a pH of about 2, breaks down large bits of food
Intrinsic factor; made by same cells making acid, needed to absorb Vitamin B12
Mucus: protects stomach lining from acid Pepsinogen (from Parietal Cells) : with
acid, begins protein breakdown Rennin: milk coagulation
Slide 14.9BCopyright © 2001 Benjamin Cummings, an imprint of Addison Wesley Longman, Inc.
Digestion of protein – stomach
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endopeptidases – break down peptide bonds in the middle of peptides
peptidases – break down peptides into amino acids
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Proteases (from pancreas)trypsinogen trypsin
enterokinase (from intestine)
Proteins peptides trypsin
Chemotrypsinogen chemotrypsintrypsin
Proteins peptideschemotrypsin
Small peptides amino acidscarboxypeptidase
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Endopeptidases (first) hydrolyse peptide bonds at points along the protein
Carboxypeptidase liberates terminal amino acids
COOH NH2
Exopeptidases acts on terminal amino acids
Aminopeptidase breaks terminal amino acids with –NH2 group
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From instestinal juice
exopeptidases – break down peptide bonds on terminal amino acids aminopeptidases – break down amino
acids with a free amino (-NH2) group
Carboxypeptidase liberates terminal amino acids with free COOH
2002 Paper II B Q.4 (b) maternal digestion: protease breaks down
proteins to amino acids (1) / peptides, in stomach and small intestine (1)
absorbed into the maternal blood stream at the ileum (1)
a.a. carried via veins to hearts, then along artery to uterine wall (1)
a.a. diffuse across the *placenta into foetal blood circulation (1)
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Digestion of lipid
Bile salts - They emulsify fats into minute
droplets - This is a physical digestion which
increases the surface area for pancreatic lipase to act on
Lipase -hydrolyses fats into fatty acids
and glycerol
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Digestion of nucleic acid
Nuclease -changes nucleic acids into
nucleotides
Other substances
Many substances in the diet are composed of small molecules that need little or no digestion. These include sugars, mineral ions, vitamins and water. These are absorbed by different transport mechanisms: • Cholesterol and the fat-soluble vitamins (A, D, E, K) are
absorbed into the epithelial cells of the ileum by lipid diffusion
• Mineral ions and water-soluble vitamins are absorbed by passive transport in the ileum
• Dietary monosaccharides are absorbed by active transport in the ileum Water is absorbed by osmosis in the ileum and colon.
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Regulation of Digestion
Regulation dependent on volume and content of food
Neural and hormonal mechanisms coordinate glands
Nervous system: stretch receptors in stomach
GI activity stimulated by parasympathetic innervation
Inhibited by sympathetic innervation
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Hormones:Stomach
• Gastrin: stimulates release of gastric juice
Duodenum• Secretin: stimulates pancreas to secrete water and bicarbonate• Cholecystokinin (CCK): signal the smooth muscle of the gall
bladder to contract• Pancreozymin : signals pancreas to secrete digestive enzymes
Coordination secretion and absorption
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stom ach
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pancreas
duodenum
stom ach
gall bladder
food (lip id )
pancreas
duodenum
stom ach
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food (lip id )ga str ic ju ice
pancreas
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Secretin
stom ach
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food (lip id )ga str ic ju icepa ncrea tic flu id (b ica rbon a te)
pancreas
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CCK
stom ach
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food (lip id )ga str ic ju icepa ncrea tic flu id (b ica rbon a te)pa ncrea tic enzym e (lipa se )
pancreas
duodenum
stom ach
gall bladder
food (lip id )ga str ic ju icepa ncrea tic flu id (b ica rbon a te)
b ile ju icepa ncrea tic enzym e (lipa se )
pancreas
duodenum
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The Activities of Major Digestive Tract Hormones
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Absorption Very little is absorbed from stomach and large
intestine Most absorption is from SI Large SA of microvilli enhance absorption cap
acity Capillaries from villi converge into hepatic
portal vein Cecum is an extension of LI E. coli live in LI and generate gas and vitamins Water is reabsorbed from SI and LI Diarrhea and constipation result from
abnormal water reabsorption
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Absorption of Proteins and Carbohydrates
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Absorption of Fats
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Absorption of Nutrients
Proteins and carbohydrates: active transport
Lipids: broken down and reassembled
Water: osmosis
Vitamins and minerals: assorted means
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The Intestinal Wall
D). Internal structures of a single villus, showing the capillary and lymphatic suppliesE). A villus in sectional view (LM X 252)
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The structure of the small intestine (ileum) in relation to its functions
The millions of finger-like villi cover the entire surface of the intestinal lining. The villi are greatly folded to increase the surface area for absorption. The wall of the villi are thin (with only one layer of epithelial cells) and this
permit the food to diffuse through easily. The epithelial cells lining the villi have cylindrical projections called brush
border micro-villi. These further increase the surface area of absorption. The villi contain blood capillaries to absorb glucose and amino acids through
the hepatic portal system to the liver. The villi contain lacteals to absorb fatty acids and glycerol. Glandular cells in epithelial lining which secrete digestive enzymes for
digestion of food molecules as they pass through. Circular and longitudinal muscles involved with peristalsis. They mix the
digestive juices with chyme so promoting hydrolysis of food by the enzymes. Mucus secretion which protects epithelium.
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The Intestinal Wall
Crypt of Lieberkuhn• Cells secrete proteins, fluids, electrolytes– Paneth cells – secrete proteins– Goblet cells – secrete mucus• These cells also serve as protectivebarrier against pathogens• Epithelial cells undergo mitosis and travelto tips of villi the sloghed off• Intestinal cell turnover is rapid ~ 3-5 days
Absorption in large intestine
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Nutrients:Utilized or Stored Until Needed
2006 Paper IIB Q.8
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2006 Paper IIB Q.8
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Liver Largest gland in the body
Has two lobes—large right and small left
Contains approximately 100,000 lobules that serve as structural and functional units
Triads, consisting of three structures, located between the lobules
Bile duct—takes bile away from liver
Hepatic artery—brings O2-rich blood to liver
Hepatic portal vein—transports nutrients from intestines
The central veins of lobules enter a hepatic vein
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The Liver - an organ for digestion and homeostasis
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Blood system associated with the liver
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The Structure of The Liver
- Blood is drained into the liver by 2 vessels: the hepatic artery and the hepatic portal vein- Blood is drained away from the liver by the hepatic vein
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- Branches of the hepatic artery & heptic portal vein combine within the liver to form common venules which lead into a series of channels called sinusoids.
Sinusoids are lined with liver cells (hepatocytes) and drains into a branch of the hepatic vein called the central vein.
- Between the hepatocytes are fine tubes called canaliculi in which bile is secreted.
The canaliculi combine to form bile ducts which drain into the gall bladder.
- The functional unit of the liver is the acinus. In the sinusoids materials are exchanged
between the hepatocytes and blood.
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Structures of hepatocytes for exchange of materials with high metabolic rate:
microvilli, large nucleus, many mitochondria, lysosomes and glycogen granules.The canaliculi are also lined with
microvilli to remove bile from the hepatocytes by active transport.
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- Sinusoids are lined with endothelial cells with specialized Kupffer cells of the reticulo-endothelial system for ingesting any foreign materials and damaged, worn out RBCs.
Bilirubin is produced as a by-product & excreted in the bile.
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Functions of The LiverThe liver has about 500 individual functions. They are grouped as below:1.Carbohydrate metabolism - action of insulin & glucagon by inlets of
Langerhans2.Lipid metabolism - lipids are broken down or transported to
storage areas - excess carbohydrates lipid - regulate cholesterol level; atherosclerosis
& gall stones
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3. Protein metabolism - deamination - transamination to synthesize non-
essential amino acids4. Synthesis of plasma proteins, e.g. clotting factors: prothrombin &
fibrinogen5.Production of bile:
bilirubin + bile salts + NaCl + HCO3-
6.Storage of vitamins, especially fat soluble vitamins A, D, E, K
7.Storage of minerals, e.g. Fe, K, Cu & Zn
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8. Formation & breakdown of RBCs
- foetal liver produces RBCs - adult liver breaks down aged RBCs9. Storage of blood - about 1500 cm3 of blood can be stored10.Hormone breakdown, e.g. testosterone, insulin etc11.Detoxification - Kupffer cells ingest foreign materials - hepatocytes convert toxic chemicals into harmless
forms12. Production of heat - when body temperature falls - triggered by the hypothalamus, is in response to
adrenaline, thyroxine & nervous stimulus