DIGESTIVE SYSTEMDIGESTIVE SYSTEM

Nutrition and digestionNutrition and digestion

All organisms need energy for their All organisms need energy for their metabolism. They get this energy by metabolism. They get this energy by nutrition. nutrition.

Digestion is the breaking down the food Digestion is the breaking down the food into monomers , making easy the diffusion into monomers , making easy the diffusion of molecules through the membrane. of molecules through the membrane.

Mechanical and chemical digestion. Mechanical and chemical digestion.

Mechanical or physical digestion: It is the Mechanical or physical digestion: It is the breaking down the polymers physically. In breaking down the polymers physically. In that way the surface area of the substrate that way the surface area of the substrate is increased. This enables the digestive is increased. This enables the digestive enzyme activity.enzyme activity.

Chemical digestion: It is the breaking Chemical digestion: It is the breaking down the polymers into monomers by the down the polymers into monomers by the help of the digestive enzymes. help of the digestive enzymes.

Intracellular digestion Intracellular digestion Intracellular digestion takes Intracellular digestion takes

part in cell. To do intracellular part in cell. To do intracellular digestion, food molecules digestion, food molecules should be taken from outside should be taken from outside by phagocytosis. Lysosome by phagocytosis. Lysosome takes part in this kind of takes part in this kind of digestion. Unicellular digestion. Unicellular organisms, some primitive organisms, some primitive multicellular animals or multicellular animals or specialized cells like liver and specialized cells like liver and white blood cells do white blood cells do intracellular digestion.intracellular digestion.

Extracellular digestionExtracellular digestion Extracellular digestion takes Extracellular digestion takes

part out of the cell. To do part out of the cell. To do extracellular digestion, extracellular digestion, digestive enzymes are digestive enzymes are secreted out of the cells. Then secreted out of the cells. Then digested monomers are taken digested monomers are taken to the cells by transport to the cells by transport mechanisms. Most of the mechanisms. Most of the multicellular animals , fungi, multicellular animals , fungi, both autotroph heterotroph both autotroph heterotroph plants do extracellular plants do extracellular digestion. In that way digestion. In that way organisms can use many kinds organisms can use many kinds of polymersof polymers

Digestion in unicellular organisms Digestion in unicellular organisms Digestion is intracellular in unicellular organisms. Digestion is intracellular in unicellular organisms.

Food is taken by phagocytosis. Food vacuole then Food is taken by phagocytosis. Food vacuole then unites with the primary lysosome to form secondary unites with the primary lysosome to form secondary lysososme. Food molecules are broken down by lysososme. Food molecules are broken down by hydrolytic enzymes. Undigested materials are hydrolytic enzymes. Undigested materials are thrown out of the cell by exocytosis.thrown out of the cell by exocytosis.

Digestion in InvertebratesDigestion in Invertebrates

Digestive systems of the invertebrates are Digestive systems of the invertebrates are adapted according to their nutritional types. adapted according to their nutritional types.

Sponges make intracellular digestion. Hydra can Sponges make intracellular digestion. Hydra can do both intra and extracellular digestion. do both intra and extracellular digestion.

Parasites like don’t have developed digestive Parasites like don’t have developed digestive systems because they their food readily. systems because they their food readily. Planaria has a primitive digestive system with Planaria has a primitive digestive system with one opening. one opening.

From the beginning of the From the beginning of the phylum Annelids 2 openings phylum Annelids 2 openings (mouth and anus) can be seen. (mouth and anus) can be seen. In the earthworm digestive In the earthworm digestive system consists of mouth, system consists of mouth, pharynx, esophagus, crop, pharynx, esophagus, crop, gizzard, intestine, anus. gizzard, intestine, anus.

Snail has a teeth-like structure Snail has a teeth-like structure called radula.called radula.

Arthropoda has a developed Arthropoda has a developed digestive system. digestive system.

Filter feedersFilter feeders, such as clams , such as clams and blue whales, prey on small and blue whales, prey on small organisms by filtering them organisms by filtering them from the aquatic environmentfrom the aquatic environment

Digestive system in VertebratesDigestive system in Vertebrates Herbivores, Carnivores and omnivores have Herbivores, Carnivores and omnivores have

different adaptations according to their nutrition. different adaptations according to their nutrition.

the teeth of herbivorous vertebrates have been shaped by the teeth of herbivorous vertebrates have been shaped by selection to process plantselection to process plant.. The digestive processes of The digestive processes of herbivores can also be quite specializedherbivores can also be quite specialized . .

Digestive system is very long in herbivores but short in Digestive system is very long in herbivores but short in carnivores. Nonruminant herbivores(rabbit) have carnivores. Nonruminant herbivores(rabbit) have developed cecum which has microorganisms to digest developed cecum which has microorganisms to digest cellulose in plant tissues.cellulose in plant tissues.

The digestive tracts of The digestive tracts of ruminants ruminants (cud chewers) such as (cud chewers) such as cattle, goats, and sheep are specialized to maximize the cattle, goats, and sheep are specialized to maximize the benefits of their endosymbiotic microorganismsbenefits of their endosymbiotic microorganisms. They . They have a have a large, four-chambered large, four-chambered stomach. stomach. The first two The first two chambers, the chambers, the rumen rumen and the and the reticulumreticulum, are packed with , are packed with anaerobic microorganisms that break down cellulose by anaerobic microorganisms that break down cellulose by fermentation. The ruminant periodically regurgitates the fermentation. The ruminant periodically regurgitates the contents of the rumen (the contents of the rumen (the cudcud) into the mouth for ) into the mouth for rechewing. When the more thor oughly ground-up rechewing. When the more thor oughly ground-up vegetable fibers are swallowed again, they present more vegetable fibers are swallowed again, they present more surface area to the microorganisms for their digestive surface area to the microorganisms for their digestive actions.actions.

(işkembe, börkenek, kırkbayır, şirden)(işkembe, börkenek, kırkbayır, şirden)

Birds don’t have teeth, instead their beaks(bill) help Birds don’t have teeth, instead their beaks(bill) help gathering food. gathering food.

esophagusesophagus - narrow tube that carries food to the crop - narrow tube that carries food to the crop cropcrop - a sack-like widening of the digestive tract where - a sack-like widening of the digestive tract where

food can be stored temporarily food can be stored temporarily proventriculusproventriculus - the first chamber of a bird's stomach - the first chamber of a bird's stomach

where food is broken down by digestive enzymes where food is broken down by digestive enzymes gizzardgizzard - the second chamber of a bird's stomach where - the second chamber of a bird's stomach where

food is ground up by muscular action and small stones food is ground up by muscular action and small stones or grit (ingested by the birds) or grit (ingested by the birds)

intestinesintestines - -

Human Digestive SystemHuman Digestive System The human digestive The human digestive

system is a coiled, muscular system is a coiled, muscular tube (6-9 meters long when tube (6-9 meters long when fully extended) stretching from fully extended) stretching from the mouth to the anus. Mouth, the mouth to the anus. Mouth, pharynx, esophagus, stomach, pharynx, esophagus, stomach, small intestine, large intestine, small intestine, large intestine, and anus. Accessory digestive and anus. Accessory digestive organs are connected to the organs are connected to the main system by a series of main system by a series of ducts: salivary glands, exocrine ducts: salivary glands, exocrine part of the pancreas, liver and part of the pancreas, liver and gall bladder gall bladder

There are 32 There are 32 permanent teeth permanent teeth

From the midline of From the midline of one side of each jaw one side of each jaw consists of 2 incisors, consists of 2 incisors, 1 canine, 2 premolars 1 canine, 2 premolars and 3 molars and 3 molars

Mechanical breakdown begins in the mouth by chewing (teeth) and Mechanical breakdown begins in the mouth by chewing (teeth) and actions of the tongue. Chemical breakdown of starch by production of actions of the tongue. Chemical breakdown of starch by production of salivary amylase from the salivary glands. This mixture of food and salivary amylase from the salivary glands. This mixture of food and saliva is then pushed into the pharynx and esophagus. The esophagus saliva is then pushed into the pharynx and esophagus. The esophagus is a muscular tube whose muscular contractions (peristalsis) propel is a muscular tube whose muscular contractions (peristalsis) propel food to the stomach. food to the stomach.

Muscles in the esophagus propel the bolus by waves of Muscles in the esophagus propel the bolus by waves of involuntary muscular contractions (peristalsis) of smooth involuntary muscular contractions (peristalsis) of smooth muscle lining the esophagus muscle lining the esophagus

Stomach is lined with epithelial layer which secrete Gastric Stomach is lined with epithelial layer which secrete Gastric juice. Gastric juice contains hydrochloric acid, pepsinogen, juice. Gastric juice contains hydrochloric acid, pepsinogen, lipase and mucus. Secretions are controlled by nervous lipase and mucus. Secretions are controlled by nervous (smells, thoughts, and caffeine) and endocrine signals. (smells, thoughts, and caffeine) and endocrine signals. Mucus covers the inner layer of stomach and prevents the Mucus covers the inner layer of stomach and prevents the damage of HCl. HCl activates inactive enzyme pepsinogen damage of HCl. HCl activates inactive enzyme pepsinogen and form pepsin which digests proteins. Small amount of and form pepsin which digests proteins. Small amount of lipase digests lipids. lipase digests lipids.

The small intestine is where final The small intestine is where final digestion and absorption occur. digestion and absorption occur. The small intestine is a coiled tube The small intestine is a coiled tube about 6 meters long. The surface about 6 meters long. The surface area of the small intestine is area of the small intestine is increased by villi(fingerlike increased by villi(fingerlike projections).projections).

The upper part, the duodenum, is The upper part, the duodenum, is the most active in digestion. the most active in digestion. Secretions from the liver and Secretions from the liver and pancreas are used for digestion in pancreas are used for digestion in the duodenum. Epithelial cells of the duodenum. Epithelial cells of the duodenum secrete a watery the duodenum secrete a watery mucus. The pancreas secretes mucus. The pancreas secretes digestive enzymes and stomach digestive enzymes and stomach acid-neutralizing bicarbonate. The acid-neutralizing bicarbonate. The liver produces bile, which is stored liver produces bile, which is stored in the gall bladder before entering in the gall bladder before entering the bile duct into the duodenum. the bile duct into the duodenum.

The liver produces and sends bile to the small The liver produces and sends bile to the small intestine via the hepatic duct and vater point . Bile contains intestine via the hepatic duct and vater point . Bile contains bile salts, which emulsify fats, making them susceptible to bile salts, which emulsify fats, making them susceptible to enzymatic breakdown.enzymatic breakdown.

In addition to digestive functions, the liver plays several other In addition to digestive functions, the liver plays several other roles: roles:

1)1) detoxification of blood; detoxification of blood; 2)2) synthesis of blood proteins;synthesis of blood proteins;3)3) destruction of old erythrocytes and conversion of destruction of old erythrocytes and conversion of

hemoglobin into a component of bile; hemoglobin into a component of bile; 4)4) production of bile;production of bile;5)5) storage of glucose as glycogen, and its release when storage of glucose as glycogen, and its release when

blood sugar levels drop; (stores ADEK vit.)blood sugar levels drop; (stores ADEK vit.)6)6) production of urea from amino groups and ammonia. production of urea from amino groups and ammonia.

Liver recieves blood from 2 Liver recieves blood from 2 different supplies. different supplies.

Blood rich in digested monomers Blood rich in digested monomers comes from the vein from the comes from the vein from the intestine. (hepatic portal vein)intestine. (hepatic portal vein)

Blood rich in oxygen comes from Blood rich in oxygen comes from the AORT(hepatic artery) the AORT(hepatic artery)

The pancreas contains exocrine The pancreas contains exocrine cells that secrete digestive cells that secrete digestive enzymes(trypsinogen, amylase, enzymes(trypsinogen, amylase, lipase) into the small intestine lipase) into the small intestine and clusters of endocrine cells. and clusters of endocrine cells. The Langerhans islets secrete The Langerhans islets secrete the hormones insulin and the hormones insulin and glucagon, which regulate blood glucagon, which regulate blood glucose. glucose.

Hepatic portal system , has capillary, vein capillary, vein structure

Mouth: mechanical and chemical digestionMouth: mechanical and chemical digestion

Stomach: mechanical and chemical digestionStomach: mechanical and chemical digestion

pepsinogen HCl pepsin pepsinogen HCl pepsin

Duodenum: Duodenum: mechanical and chemical digestionmechanical and chemical digestion

Gall bladder: Fat bile fat dropletGall bladder: Fat bile fat droplet

pancreas: fat droplet Lipase glycerol+fatty acid pancreas: fat droplet Lipase glycerol+fatty acid starch amylase maltosestarch amylase maltose

peptons Chymotrypsin peptides+ aapeptons Chymotrypsin peptides+ aa

trypsintrypsin

Intestine: Chemical digestion and absorption

dipeptid erepsin aa

Maltose maltase glucose sucrose sucrase glucose+fruc

Digestion of polymersDigestion of polymers

Don’t forget vitamins, minerals, water can’t be digested and can’t give energy. They are absorbed without any change

Digestion of carbohydratesDigestion of carbohydrates

mouth

duodenum

Small intestine

Digestion of proteinsDigestion of proteins

stomach

duodenum

Small intestine

Digestion of fatDigestion of fat

duodenum

AbsorptionAbsorption

Villi and micro villi Villi and micro villi increases increases absorption rate. absorption rate. Under the epithelial Under the epithelial layer there are layer there are blood and lymph blood and lymph vessels in mucosa. vessels in mucosa.

Monosaccharides, aminoacids, minerals, water soluble Monosaccharides, aminoacids, minerals, water soluble vitamins pass to the blood vessels. They are carried to vitamins pass to the blood vessels. They are carried to the liver by portal vein. the liver by portal vein.

But fatty acid, glycerol and fat soluble vitamins pass to the But fatty acid, glycerol and fat soluble vitamins pass to the lymphatic vessels from the epithelium. Lymphatic vessels lymphatic vessels from the epithelium. Lymphatic vessels mix with the circulatory system just before the heart.mix with the circulatory system just before the heart.

Water is absorbed all the way through the digestive system. Minerals Water is absorbed all the way through the digestive system. Minerals and vitamins are mainly absorbed from large intestine. and vitamins are mainly absorbed from large intestine.

Undigested matter is thrown out by feces. Undigested matter is thrown out by feces.

Pathway of the monomersPathway of the monomers glucose, fructose, galactose, glucose, fructose, galactose,

minerals, water soluble minerals, water soluble vitamins, aminoacidsvitamins, aminoacids

Mesenteric vein from Mesenteric vein from intestineintestine

Hepatic portal veinHepatic portal vein LiverLiver Hepatic veinHepatic vein İnferior vena cavaİnferior vena cava Right atriumRight atrium

Fatty acid, glycerol, fat Fatty acid, glycerol, fat soluble vitaminssoluble vitamins

Lymphatic vesselsLymphatic vessels Thoracic ductThoracic duct Left subclavian veinLeft subclavian vein Superior vena cavaSuperior vena cava Right atriumRight atrium

Salivation is stimulated by the sight or smell of food. That response is an autonomic reflex, as is the act of swallowing following tactile stimulation at the back of the mouth. Many such autonomic reflexes coordinate activity in different regions of the digestive tract. Stretching the stomach with food, for example, stimulates increased activity in the colon, which can lead to the expulsion of feces.

The stomach secretes a hormone called gastrin into the blood. Gastrin circulates in the blood until it reaches cells in the upper areas of the stomach wall, where it stimulates the secretions and movements of the stomach.

secretin is one of several hormones that con trol pancreatic secretion; specifically, secretin stimulates the pancreas to secrete a solution rich in bicarbonate ions.

In response to the presence of fats and proteins in the chyme, the mucosa of the small intestine secretes cholecystokinin, a hormone that stimulates the gallbladder to release bile and the pancreas to release digestive enzymes.