Digestive System Teacher

The Digestive The Digestive SystemSystem

The Digestive The Digestive SystemSystem

Bleecker-Style Bleecker-Style

Table of Contents Cells, Tissues, Organs, Organ Systems Introduction to the Digestive System What is Digestion? 2 Phases of Digestion 4 Components of Digestion The Organs of Digestion

How the Body is Organized

1. Cellular Level

- Individual cells are the basic building blocks of life

2. Tissue level

- Tissue is formed when groups of cells act together

3. Organ Level

- An organ is a system of tissues working together

4. System Level

- Many organs acting together form a system,

such as the DIGESTIVE

SYSTEM

Introduction to the Digestive System

• The digestive system is an organ system that ingests food, breaks it down into smaller chemical units, and absorbs the nutrient molecules.

What is Digestion?

• Digestion is the mechanical and chemical breakdown of food into molecules small enough for the body to absorb.

2 Phases of Digestion1. Mechanical Digestion – begins in the

mouth where the food is chewed. - Saliva = watery fluid making it easier to swallow. Also some enzymatic digestion of starch

2. Chemical Digestion – occurs in the mouth and the stomach. HCl produced by the stomach cells.

4 Components of Digestion

1. Ingestion – the intake of nutrients2. Digestion – the breakdown of organic

molecules3. Absorption – the transport of digested

nutrients to body tissues4. Egestion – the removal of materials

from food that the body cannot digest

The Organs ofThe Organs ofThe Organs ofThe Organs of

DigestionDigestion

Mouth

Physical digestion begins Food is chewed into a bolus and

mixed with saliva Initial carbohydrate digestion

Parts of the Mouth

20 Baby Teeth

32 Adult Teeth

Wisdom Teeth …

Salivary Glands in the Mouth

Swallowing and the Epiglottis

Air enters via pharynx

The epiglottis is a flap of tissue that has a very important job

It covers the trachea when swallowing to prevent food to lungs

It covers the esophagus when we breath, so air goes to lungs

Esophagus

• Peristaltic contractions move the food from the mouth to the stomach through the esophagus.

Stomach Food storage Initial protein

digestion Mechanical

digestion grinding by muscles

Chemical breakdown of food by HCl

Stomach Protection from Acid

What protects stomach from digesting itself?

HCl is nasty!

Answer: cells also secrete mucus that acts as a barrier!

Stomach UlcersOUCH!

Small Intestine Site of the majority

of digestion and absorption

Digestion of proteins, carbohydrates, and lipids

Folds of small intestine increase the SA for absorbing nutrients

Small Intestine in Cross Section

SA is increased by fingerlike projections called VILLI

These do the actual absorbing of fats, proteins and carbohydrates

Villi Close up

Small Intestine – 3 Sections

Stomach to1. Duodenum to 2. Jejenum to 3. Ileum

Focus on the Duodemum

Enzyme Action in Duodemum

1. Bile from Liver is received from the Gallbladder (green)

• The bile is used as an emulsifier to help the body absorb fats

2. Lipase from the Pancreas breaks down fats into fatty acids

3. Trypsin is activated by acid from the stomach, and digests the protein further into amino acids

4. Pancreatic Amylase – digests carbohydrates

Regulating Digestive Secretions

1. Gastrin• Produced by stomach when churns• Inhibited by duodenal response

2. Duodenum secretes GIP (gastro-inhibatory peptides) to turn off gastrin production in stomach (neg loop)

3. Duodenum also produces CCK (cholecystokinin) in response to partly digested fat and protein as well as secretin that increase the output of bile from liver and pancreatic juice.

Classic Feeback Loop

- CCK stimulates liver and pancreas

Note that in Stomach, HCl Activates an Enzyme

1. Acid activates Pepsin so that protein is digested.

2. Hormone GASTRIN is secreted and sent through blood to brain to suppress appetite!

Pancreas• Releases

enzymes such as1. Amylase2. Lipase

into the small intestine to aid in digestion

Liver Produces bile salts

which emulsify fats Storehouse for

glycogen(starch) and vitamins

Detoxifies many substances in the body (alcohol, poisons, etc)

Gall Bladder• Stores bile salts

Large Intestine1. Stores food wastes

long enough to reabsorb water

2. Forms the stool, aka POOP

3. Houses bacteria which use waste materials to synthesize vitamins

3 Regions of Large Intestine you must Know

AssiGnments• Ensure that The Breakdown Ensure that The Breakdown

Video Wkst. is done and handed Video Wkst. is done and handed in before you leave.in before you leave.

• Complete Chp Review on pg. Complete Chp Review on pg. 148 #C1,C2,C4,C6,C7.148 #C1,C2,C4,C6,C7.

• Readings: (relax, they’re like Readings: (relax, they’re like the notes we just did)the notes we just did)

• Chapter notes for 7.3 & 7.4 Chapter notes for 7.3 & 7.4 (pg’s 140-148)(pg’s 140-148)

• Color the rest of the digestive Color the rest of the digestive system handout! Know it, system handout! Know it, because you will be quizzed on because you will be quizzed on it it