Unit 11 Digestive Systems

What is food made of?

• made of macromolecules (prots, lipids, carbs, + essential nutrients)

Why do animals eat?

• to get raw materials to make more cells

• to get molecules for making atp (energy)

• obtaining essential nutrients → body cant prod these on their own

Stages of the digestive system

breaks ‘stuff’ down into smaller useable pieces

1. ingestion → eating/feeding

2. digestion → breaking down food (chem + mech)

3. absorption → uptake of nutrients by cells

4. elimination → passage of undigested material

What are the two types of digestion?

intra + extra cellular

Intracellular dig

digests food inside of cells

• many protists + some simple animals

• limited in eating things that are smaller than the size of the indv cells

Extracellular dig

dig done in an open cavity

• most animals + fungi

• involves mouth

• can eat bigger orgs

• gastrovascular cavity

Importance of a gastrovascular cavity?

involved in both dig + gas exchange (not in cells)

Steps of extracellular dig

1. dig enzymes released

2. food particles broken down

3. food particles engulfed + digested by cells

What is a complete dig system?

• 1 directional tube

• separates mouth + anus

• many specialized parts

• varies in complexity + length → herbivore cecum > carnivore cecum (size)

What are the 4 major tissue types?

1. nervous

2. connective

3. epithelial

4. muscle

Layers of the dig organ tissues

1. mucosa layer= epithelial

2. submucosa= nervous

3. muscularis= muscle

Dig tract order

mouth → pharynx → esophagus → stomach → small int → large int → rectum → anus

What are dig system accessory organs?

liver, pancreas, + gall bladder

Dig tract characteristics

• hollow tube

• 30 in long

• complete gut

The mouth

• involved in chem + mech dig

• saliva contains amylase that breaks down starch

• 1st defense against bacteria

• tonsils= immune sys cells

The esophagus

• pharynx= throat

• long, musc tube that connects to stomach

• where peristalsis takes place

What is peristalsis?

waves of musc contractions that propels food forward → helps move food through the dig tract

Purpose of sphincters

• thick musc rings separate orgs

• prevs backflow of food + release of waste

The stomach

• has extra musc layers for mech dig

• rugae= expandable folds of mucosa that prod mucus

• many form of chem dig → gastric juice, HCl, pepsin breaks down prots, mucus cells protect lining

When is the stomach finished?

when chyme is passed onto the small int

What is a stomach ulcer?

occurs if mucus layer becomes damaged

• exposed tiss underneath is now vulnerable to damage by stom acid

The small int

• completes dig ( duodenum) + performs absorption

• lined w microvilli → fingerlike projections that increase surf area to max nutrient absorption