Digestive System

Why do we eat?

Why do we eat?

-food provides nutrients needed for building tissues and maintaining needed chemical reactions (food is a source of energy for every cell)

What does the digestive system do in general?

breaks food down into usable form = nutrients

What are the (5) specific functions of the digestive system?

1. ingestion

2. movement of food via peristalis (squeezing) using smooth muscle

3. digestion

4. absorption

5. defecation

Describe ingestion.

- mouth - entry to digestive system

Describe digestion.

breaking food down into nutrients

What are the two types of digestion?

mechanical and chemical

Describe mechanical digestion.

physical breakdown (example: teeth grinding up food)

Describe chemical digestion.

chemical breakdown (example: enzymes)

What are the main biomolecules being digested?

protein, carbohydrates, lipids

Describe absorption.

nutrients to tissues

Define defecation.

eliminating indigestible residues (pooping)

What us the gastro-intestinal tract?

- 10 m continuous tube from mouth to anus

-accessory structures along the way to help with digestion, but food doesn’t pass through them

What are the 4 main layers in the tube?

1. mucosa

2. submucosa

3. muscularis

4. serosa

Draw a diagram of the 4 layers of the gastro-intestinal tract.

yellow = mucosa

green = submucosa

blue = muscularis

purple = serosa

Describe mucosa.

-contains epithelial tissue

Where is mucosa simple?

-in areas of high diffusion like small intestine

Where is mucosa stratified?

-in areas of high wear and tear like mouth or anus

Describe muscularis.

-contains muscle

-mostly smooth

Where is muscularis skeletal (voluntary)?

-in areas where you need to choose like pharynx for swallowing or anus for pooping

Name all the structures food must pass through.

mouth, pharynx, esophagus, stomach, duodenum, jejunum, ileum, cecum, ascending colon, transverse colon, descending colon, sigmoid colon, rectum, anus

What is food called when it passes through the pharynx (swallowed)?

bolus

What is food called when it goes to the stomach?

bolus turns into chyme

What is food called when it passes through the large intestine?

chyme turned into feces

What are the parts of the mouth (oral cavity)?

-gingivae

-palate

-uvula

-tongue

-teeth

What are the gingivae?

gums

What is the palate?

hard and soft roof of mouth

What does the uvula do?

lifts when swallowing to keep food out of nose

What are the structures on the tongue? Describe their purpose.

-papillae

-bumps on tongue that contain taste buds

Draw a diagram of the tongue and label which parts of the tongue can taste sweet, salt, sour, bitter, and umami.

Draw a diagram of the side view of the tongue and label a papilla and a taste bud.

Name the different tooth types.

incisors, cuspids, bicuspids, molars

What is the function of the incisors?

cut

What is the function of the cuspids?

rip/tear

What is the function of the bicuspids?

rip/tear

What is the function of the molars?

grinding

Name the tooth parts.

crown, neck, root, layers

What are the layers made up of?

enamel (hardest substance in body), dentin, pulp cavity

Which tooth types do herbivores have?

only molars and incisors for grinding and cutting plants

Which tooth types do omnivores have?

all tooth types

Which tooth types do carnivores have?

all tooth types, but all are pointy

What is the pharynx?

common space for air and food

What is the esophagus?

-food tube

-muscular (peristalsis) and collapsable

What is the stomach?

-mixing area and reservoir

-4 parts

-has rugae

What are the 4 parts of the stomach?

cardia, fundus, body, pylorus

What is the rugae?

folds for stretching and to increase surface area for secretion

What is the small intestine?

-most absorption of nutrients occurs here via diffusion

-very long and has folds called villi to increase surface area

-3 parts

What are the 3 parts of the small intestine?

duodenum, jejunum, ileum

What are the parts of the large intestine?

cecum, ascending colon, transverse colon, descending colon, sigmoid colon, rectum, anus

What are the accessory structures to the digestive system?

pancreas, liver, gall bladder

What does it mean when something is an accessory structure?

food does not pass through it, but it aids in digestion

What is the function of the pancreas?

-secretes pancreatic juice

-has pancreatic islets

What does pancreatic juice consist of?

water + salts + sodium bicarbonate + digestive enzymes

What is the purpose of sodium bicarbonate in pancreatic juice?

for neutralizing stomach acids

What are pancreatic islets?

secrete glucagon and insulin to control blood sugars

What is the liver?

-heaviest gland in body

-functions in metabolism and the removal of toxin (sinusoids)

What are sinusoids?

blood pods in the liver, so can be detoxified

What is the gall bladder?

-stores bile that was secreted by liver

-releases bile into duodenum to emulsify fats when needed

What is a diet?

what you eat