Objectives: 1.Label the gross structure of the digestive system 2.List the basic units produced by the digestion of the three macromolecules 3. State.

Objectives:1.Label the gross structure of the

digestive system2.List the basic units produced by the

digestion of the three macromolecules 3. State the four stages of digestion. 4.Describe in detail the digestion of one

macromolecule including the specific enzymes involved

http://science.nationalgeographic.com/science/health-and-human-body/human-body/digestive-system-article.html

Stages of digestion

IngestionDigestionAbsorptionEgestion

Digestion: breaking down large molecules

Physical ChemicalChewingPeristalsisChurning

Hydrolysis reactionsEnzymesSubstances

Digestive juices:

Saliva GastricPancreaticIntestinal

All contain enzymes

Carbohydrate DigestionTwo StagesStarch to MaltoseMaltose to Glucose

Carbohydrate : Starch

Digestion starts in the mouthPhysical:Teeth / chewingTongue

ChemicalSalivary AmylaseStarch Amylase MaltoseMucus

Carbohydrate : Starch 2OesophagusPhysicalPeristalsis

ChemicalMucus

Figure 14.3ASlide 14.4Copyright © 2001 Benjamin Cummings, an imprint of Addison Wesley Longman, Inc.

Peristalsis

Carbohydrate : Starch 3StomachPhysicalChurning

Carbohydrate : Starch 4Small intestine

Physical Peristalsis

Carbohydrate : Starch 5Small intestine

ChemicalPancreatic juicePancreatic amylaseStarch AmylaseMaltose

Enzymes in cell wallMaltaseMaltose Maltase Glucose

Objectives:1.Label the gross structure of the

digestive system2.List the basic units produced by the

digestion of the three macromolecules 3. State the four stages of digestion. 4.Describe in detail the digestion of one

macromolecule including the specific enzymes involved

Structure of digestive systemBasic structure alimentary canalSpecific Structure OrgansAccessory glands

Figure 14.2Slide 14.2ACopyright © 2001 Benjamin Cummings, an imprint of Addison Wesley Longman, Inc.

Gastrointestinal (GI) Tract Wall

Alimentary canal Four common layers throughout the system:Mucosa: innermost layer : secretion/

absorption, (folded, glands)Submucosa: connective tissue, lymph,

blood vessels, glands and nervesMuscularis: two layers of smooth

muscle, responsible for peristalsisSerosa: outermost layer, connective

tissue connects to abdomen

Slide 14.2B

General Structure of the Alimentary Canal

StomachMuscular sac (4 litres)Sphincter musclesMucosa:Walls contain many foldsGastric glandsMuscularis:Extra muscle layer (3)

Figure 14.7Slide 14.9ACopyright © 2001 Benjamin Cummings, an imprint of Addison Wesley Longman, Inc.

Structure of the Stomach Wall

Small Intestine (Duodenum)Small intestine = 6.5 meters long (approx)Duodenum (first 25cm)Includes bile and pancreatic ductMost digestion is completed in duodenumMucosa: Few villiEnzymes in the plasma membraneSubmucosaBlood / lymph vessels, glands, nerves

Small Intestines (ileum) Jejunum (2m) and ileum (4m)95% nutrient absorption

How would you would expect the structure of the ileum to be?

MucosaGreatly foldedVilli (large structures in mucosa)Microvilli (brush borders) GlandsEnzymes in the plasma membrane

Small Intestines (ileum) SubmucosaGood blood supplyLymph vessel supply (lacteals)GlandsNerves

villi

microvilli

AbsorptionSmall soluble molecules are

absorbed through the microvilli lining by:

DiffusionFacilitated diffusionActive transport

GlucoseActive transport (gut to epithelial cell)

Linked to sodium ionsActively pumped out

Facilitated diffusion (epithelial cell to capillaries)

Amino AcidsFacilitated diffusion (gutto epithelial cell)AA = different carrierLinked to sodium ionActively pumped outFacilitated diffusion(epithelial cell to

capillaries)

Lipid digestion

Lipid AbsorptionMucosal cell Lacteal

Monoglycerides

Fatty Acids

Diffusion

Bile salts

What’s left?Large Intestine (colon)Undigested foodBacteria (mutual benefit)Water and vitamins reabsorbedLarge, folded walls.RectumAnus

Name the small soluble food molecule resulting from protein, lipid and carbohydrate digestion.

Amino acids, fatty acids + glycerol and Amino acids, fatty acids + glycerol and glucose .glucose .

Name 3 other molecules which the body needs in a balanced diet.

Vitamins, minerals and water.Vitamins, minerals and water.Where in the alimentary canal are these 3

absorbed?The large intestine.The large intestine.

Which blood vessel takes small food molecules away from the small intestine. Where are they taken to first?

Hepatic portal vein. The liver.Hepatic portal vein. The liver.What happens to excess glucose? I.e. glucose not

needed immediately for respiration.It’s converted into glycogen and stored in the liver It’s converted into glycogen and stored in the liver

or muscle cellsor muscle cellsWhat happens to excess amino acids taken into the

liver?Amino acids can’t be stored so they are Amino acids can’t be stored so they are

deaminated by the liver cells producing glucose deaminated by the liver cells producing glucose and a waste product calledand a waste product called ureaurea

Villi

How do cells assimilate the big nutrients? a) a) Glucose Glucose provides energy by cell respiration provides energy by cell respiration

resultion in A.T.P to enable the cell to do resultion in A.T.P to enable the cell to do work eg muscle cell contraction.work eg muscle cell contraction.

b) b) Amino acidsAmino acids build into new human protein build into new human protein eg enzymes, plasma proteins, hormones and eg enzymes, plasma proteins, hormones and are used in growth and repair.are used in growth and repair.

c) c) Fatty acidsFatty acids and glycerol are used to build and glycerol are used to build cell membranes and for cell respiration. cell membranes and for cell respiration.

Ficks lawLarge SAConcentration gradientThickness of membrane

LipidsCombine with bile saltsMonoglycerides, fatty acids = glycerolMicelles travel to epithelial cell membraneMG,FA and G dissolve in phospholid bilayer

(Diffusion)Bile salts left behindTriglycerides combine with proteins form

chymomicronsDiffuse into lacteals

ProteinsDipeptidesFacilitated diffusion (gut to epithelial

cell)Cytoplasmic enzymes

ProteinsPinocytosis (maternal antibodies)