Digestive SystemPART 2PAGE 412-417PRACTICE PROBLEMS PAGE 420, #1,2,3,4A,5,7,8

Human digestive system

The StomachMuscular sac of acid

Performs mechanical and chemical digestion

Starts the breakdown of proteins

The StomachSphincter:

Know the sphincters of the stomach!

The StomachLayer to know:

Muscularis

Chyme

The StomachMucosa: another layer to know

What is the function of the mucosa

Gastric juice: what is it and how does the mucosa protect itself from it?

PepsinCatalyzes the breakdown of proteins into

their amino acid subunits

Originally produced as pepsinogenPage 411, #5

MucosaDue to proximity to strong acid, must be

constantly regenerated

Ulcer:

Heliobacter pylori: What role does this bacteri play in the production of ulcers?

Human digestive system

Small IntestineLong (up to 7m), thin (2.5cm) tube

Site of the majority of digestion and absorption

Small Intestine

Small IntestineKnow these and what goes on at each!

Duodenum

Jejunum

Ileum

Small IntestinePyloric sphincter:

PancreasBicarbonate ions (HCO3

-)

Amylase:

Trypsinogen:Trypsin: Compare and contrast pepsin/pepsinogen

with trypsin/trypsinogen.

PancreasCarboxypeptidase and erepsin:

Lipases:What difficulty do lipases encounter when

digesting food?

LiverProduces bile

Stores it in the gall bladder

Bile emulsifies fatsWhat is this and why?

AbsorptionOnce food is broken down into the

smallest subunits, it is absorbed by the cells lining the small intestine and passed into the bloodstream

Occurs in the villi and microvilli

Absorption – Surface area

Absorption – Surface areaRidges

Villi

Epithelial cellsMicrovilli

Absorption – Surface area

Absorption - TransportHow do nutrients get absorbed?

Passive transport:DiffusionOsmosisFacilitated diffusion

Know examples of molecules that get transported by these mechanisms!

Absorption – Passive Transport

Absorption – Active transportActive transport:

Involves movement of molecules against a concentration gradient

Absorption – Passive Transport