Bio Project (1)

8/7/2019 Bio Project (1)

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By:

Khizar Hayat

& Ade Bhai

10-A


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ContentsNutrition - Introduction

The Mammalian Digestive System

Working Of The Digestive SystemAbsorption OfNutrients

Transport Of Digested Foods And Its Utilization

Liver And Its Functions


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Nutritiony It is the process by which a living organism assimilates

food and uses it for various functions.

y

Holozoic Nutrition Is the mode of feeding by whic

hanimal takes in complex organic matter .

y Nutrition Consists Of :1) Feeding or Ingestion2)Digestion

3)Absorption4)Assimilation


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The Mammalian Digestive SystemIt is a well-developedSystem

which consists of theAlimentarycanal orGut ,And their associated

Glands


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The Mouth And The Buccal Cavity

Food enters the body throughthe mouth , which then leadsinto the buccal cavity.

y Teeth Large pieces of food are

broken down into smaller pieces bythe chewing and grinding action of

the teeth. This helps the enzymes towork efficiently as the surface area isincreased.

y Salivary Glands Saliva is secretedinto the mouth by these glands which

flows via tu

bescalled d

ucts into thebuccal cavity.

y Tongue It rolls the food , mixes itwith saliva. A bolus is formed which ispushed backwards through pharynxinto the oesophagus.

Larynx

Epiglottis


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Dentitiony Incisors: cutting (2)

y Canines: tearing (1)

y

Premolars: chewing,crushing (2)

y Molars: grinding,chewing, crushing (3)

y 2 + 1 + 2 + 3 = 8

y 8 x 4 = 32

y improper cleaning: toothdecay


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The Pharynx and Larynx

y Pharynx connects the buccal cavity to the oesophagus and theLarynx.

y It also leads to the trachea.

y Larynx has a slit-like opening called the glottis.y Both Food and air must past through the pharynx when they enter the

body. Usually, air passes into the trachea while food into theoesophagus .

y But sometimes the food can get into the trachea. Therefore a flap-like

structure epiglottis is at the opening of trachea which stops food fromentering. If a person tries to breathe and swallow at the same time , thefood might enter the trachea resulting in persistent coughing.


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The Oesophagus and Gut

y Oesophagus is a narrow muscular tube which passes through the chestcavityor the thorax and the Diaphragm to join the Stomach.

y Diaphragm is a sheet of muscle separating the thorax from the

abdomen.y The Wall of oesophagus is made of two layers of muscles:

1) The Longitudinal Muscles On the outside of the gut2)The Circular Muscles On the inside of the gut

y These two layers of muscles cause rhythmic, wave-like contractions of

the gut walls. This movement is known as Peristalsis. It enables foodto be mixed with the digestive juices or enzymes and it also moves thefood along the gut.


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The Stomachy The stomach is a stretchable

muscular bag with thick andwell-developed muscular walls.

y Numerous pits on the stomachlead to Gastric glands thatsecrete gastric juice.

y A ring of muscle called thePyloric Sphincter is located atthe joint of stomach and small

intestine. It controls theentrance of food into the smallintestine bycontracting andrelaxing.


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y The circular muscles constricts the lumen,whereas the longitudinal muscles shorten the

lumen.

y Their movement isAntagonistic

.


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The Small Intestine

y Itconsists of the U-shaped Duodenum, theJejunum, and the coiledIleum.

y It is about six meters long. Its walls contain glands which secrete

Intestinal enzymes.y Its walls are adapted to absorb digested food products and water.


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The Liver and Gall Bladder

y Bile is secreted by liver cells. It is an alkaline greenish-yellow liquidcontaining bile salts and bile pigments.

y Bile salts helps in the emulsification of fats.

y Bile pigments are waste products which are removed with faeces.y Gall Bladder temporarily stores bile. It is a greenish-yellow bag

attached to the liver.

y Contraction of gall bladder results in flow of bile into the duodenumviaBile duct.


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The Pancreas

y The pancreaticduct connects the duodenum with pancreas.

y In the pancreas, Pancreatic juice is produced which contains digestiveenzymes.

y Hormones such as Insulin and Glucagon are secreted throughpancreas.

y Insulin and glucagon helps in controlling the concentration of glucosein the blood.

y diagram


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The Large Intestine

y It is broader yet smaller than the small intestine. It is about 1.5 meterslong.

y Itconsists of:

1)Colon2)Rectum

y The faeces are temporarily stored in the rectum. The contraction ofrectum results in expulsion of faeces throughAnus.

y Colon mainly absorbs water and mineral salts from undigested food

materials, therefore, no digestion occurs in the large intestine.


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Mouth Processes

y Salivary glands are stimulated to secrete saliva by the food.

y Saliva is then mixed with food and Mucin in it helps to soften the food.

y Salivary Amylase is present in saliva which digests starch to maltose.

y The pH Of saliva is neutral, at which salivary amylase is active.

y Food is broken down into smaller pieces bychewing , so the surfacearea to volume ratio increases for salivary amylase to work on.

y Bolus is formed by the tongue which is swallowed passes down to theoesophagus via Pharynx.

Diagram


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Stomach Processes

y The presence of food in the stomach stimulates the gastric glands tosecrete gastric juices.

y The stomach wall churns and breaks up the food through peristalsis.

This movement mixes the food with the gastric juices very well.y Gastric juice is a dilute solution of hydrochloric acid(pH 2) and two

enzymes, Pepsin and Renin. This dilute hydrochloricacid:1)Denatures salivary amylase, so its action stops;2)Converts the inactive forms of enzymes, pepsinogen and

prorennin, in the gastric

ju

ic

e, to the ac

tive forms:P

epsin and Reninrespectively;3)Provides a slightly acidicmedium, which is suitable for the action ofthese enzymes;


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4)Kills certain potentially harmful micro-organisms in food.

y Proteins are actedupon byproteases pepsin and rennin.1)Pepsin digests proteins to polypeptides or peptones.2)Rennin curdles milk protein byconverting the soluble protein

caseinogen into insoluble casein.y This partly digested food becomes liquefied, forming Chyme.

y Chyme passes into the duodenum in small amounts when the pyloricsphincter relaxes.

y diagram


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Processes Of Small Intestine

Chyme entering the small intestine stimulates:

y the intestinal glands to secrete intestinal juice,which containenzymes enterokinase, erepsin(a peptidase), maltase, sucrase(or

invertase), lactase and intestinal lipase.y the pancreas to secrete pancreatic juicewhich contains enzymes

pancreatic amylase, pancreatic lipase, and trypsinogen(an inactiveform of protease).All these enzymes passes through the pancreaticduct into the duodenum.

y

the gall bladder to release bile. It passes into the duodenum via bileduct.


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Now, the food comes in contact with the pancreatic juice, bile andintestinal juice. All these fluids are alkaline. The alkalis:

y Neutralize the chyme, which is acidic; and

y Provides an alkaline medium which is suitable for the pancreatic and

intestinal enzymes ac

tion.


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Digestion OF Different Foods

Carbohydrate digestion:Starch is digested byamylases

y Starch digestion begins in mouth, but only a little starch is digested bysalivary amylase to maltose.

y there is no digestion ofcarbohydrates in the stomach.

y As the food enters the small intestine, starch is digested by pancreaticamylase into maltose, which is then digested by maltase into glucose.Lactose is converted to glucose and galactose by lactase. And sucrose is

digested by sucrase into glucose and fructose.y So,theend-products of the digestion ofcarbohydrates are simple sugars

which can easily be absorbed.


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Protein digestion:

They are digested byproteases.y Their digestion begins in stomach, where pepsin digests proteins to

polypeptides.

y Theundigested proteins enter the small intestine, where they aredigested bytrypsin to polypeptides. Trypsin is produced as inactive

trypsinogen in the pancreatic juice. In the intestine, trypsinogen isconverted into active trypsin by intestinal enterokinase.

y The produced polypeptides are then further digested to amino acids bythe enzyme erepsin in the intestinal juice.

y Thus, the end-products of protein digestion are amino acids which can

be absorbed.


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Fat digestion:

y Bile salts emulsify fats in the small intestine.y The lower the surface tension of the fats, that is, they reduce the

attractive forces between the fat molecules, causing them to break intotiny fat droplets, forming an emulsion.

y This is just a physical break-up. There has been no chemical digestion

of fats.y This emulsification only increases the surface area to volume ratio of

the fats, therefore, speeding up their digestion by lipase.

y These emulsified fats are digested by lipases(pancreatic andintestinal) to fatty acids and glycerol. The end-products of fat digestion

are thus fatty acids and glycerol, which can absorb easily.


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Absorption OfNutrientsSmall Intestines Role InAbsorption

Adaptation to absorptiony

Surface area is increased1)Inner walls of small intestines have numerous folds2)Villi on lower side lined with minute finger like projections3)Microvilli on villi

y Thin walls/One-cell thick Membranes

y Long Intestine-6 Meters- Provides sufficient time for absorption.

y Many Cappilaries present in the villi.


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How does intestines absorb?y Glucose + Amino acids absorbed by diffusion into blood capillaries of

the villi. It is sometimes absorbed by active transport when there is a

lower concentration of digested food substances in small intestineslumen than in blood capillaries.

y Glycerol and fatty acids diffuse into the epithelium where theycombinewith each other to form fat globules and then enter the lacteals.

y Water and mineral salts absorbed in colon and small intestine. Most

water is absorbed by ileum.


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Transport Of Digested Foods And

Its UtilizationSugars1)Transport : Tiny blood capillaries unite to form larger capillaries whichfurther join to form the hepatic portal veinwhich transports sugar to

the liver. In liver most of the sugar is converted to glycogen and storedwhile some is transported to the other body parts for use.2)Utilization : Oxidized and used bycells and tissues for energy. Theexcess glucoese is later transported back to liver for storing as glycogen.

y Diagram of structure of sugars


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Amino Acids1)Transport : Tiny blood capillaries unite to form larger capillaries whichfurther join to form the hepatic portal veinwhich transports amino

acids to the liver and passes through liver to the whole body.2) Utilization : Amino acids in cells are convertedto newprotoplasm for

growth andrepairof body. Amino acids are also usedto form enzymes andhormones. Excess are deaminated in liverandsecretedas urea.

y Diagram of structure of amino acids


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Liver And Its FunctionsRegulation ofblood glucose

concentrationy The normal conc. Is 10-90mg in 100cm(cube).y When the conc. Is higher than average. Islets of Langerhans in

pancreas secrete a hormone called insulin which is transportedthrough blood to liver. It stimulates the liver to convert excess glucoseinto glycogen and store it. Thus the glucose level decreases and

becomes normal.y When conc. Is lower than average. Islets of Langerhans secrete a

hormone glucagon which stimulates the liver to convert glycogen intoglucose thus the glucose level increases and becomes normal.


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Production of Bile

y The bile is produced by the liver.

y It is temporarily stored in gall bladder.

y It is an alkaline greenish-yellow liquid containing bile salts and bile

pigmentsy It helps in digesting fats by emulsifying them.

y They are waste products thus are excreted with feaces.

y Diagram of gall bladder


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Iron Storage

y It is an important mineral which is neede to help the RBCs To deliveroxygen to the body.

y It acts as an aid in energy production and cell diffusion.

y It Helps the immune and central nervous systems.y It is formed when the hemoglobin from destruction of RBCs is brought

into the liver and is broken down.


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Protein Synthesis

y Liver synthesizes proteins in plasma from amino acids inthe diet.

y These Proteins include Albumins, Globulins.

y The Proteins also include Fibrinogen which is essential forclotting of blood.

y Diagram


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Deamination Of Amino Acids

y Excess aminoacids are transported to liver.

y They are De-Grouped and converted toUrea. This is called theDeamination Of protiens.

y The Urea is then Excreted in Urine.y The remains of deaminated amino acids are converted to glucose in

liver. If excess glucose is produced, It is converted to glycogen.

y Diagram of structure of amino acids


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Detoxification

y The process ofconverting harmful substances into harmlesssubstances.

y For example alcohol is broken down in liver by the enzyme alcohol

dehydrogenase and becomes acetaldehyde. This is further brokendown so that it can be used in respiration.


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