Digestive System

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Digestive System - Objectives

Describe the function of the digestive system Starting with the mouth describe the process

of swallowing Explain the whole process of digestion from

chewing to excretion Discuss the age-related changes that happen

to this system

Function of the Digestive System

Take in food Through the mouth

Break down the food from complex molecules to simple Mechanical Digestion

Chewing and mixing Chemical Digestion

Enzymes mix to breakdown food further

Absorb nutrients Simple molecules that

were broken down now are absorbed through the walls of the small intestine and used throughout the body

Eliminate waste We do not use all of the

food taken in, just what is needed. What is not used is waste and is excreted out of the body

The Digestive System and the Nervous System

The ENS or enteric nervous system is made up of enteric plexus which are sensory neurons which connect the digestive system to the CNS and ANS It helps in moving food through the digestive tract

by stimulating smooth muscle Detects chemical changes and causes secretions

of enzymes to aid in the digestive process Connects motor neurons to sensory neurons in

the digestive system

How do we swallow?

Three phases Voluntary phase: the ball of food we chew (bolus)

is pushed to the back of the mouth by our tongue Pharyngeal phase: when it gets to the back of the

mouth receptors receive the food and push it further down and the pharyngeal constrictor muscles take over the food down the pharynx

Esophageal phase: the swallowing phase takes about 5 -8 seconds and is responsible for getting the food from the pharynx to the stomach

Structure/Anatomy

Digestive Tract Tube extended from the mouth to the anus with

other organs attached to secrete fluids that aid in the digestion process

Gastrointestinal tract (GI tract) is often a synonym, but should only refer to the stomach and intestine

Structure/Anatomy

Oral Cavity Contain teeth for manual

breakdown of food

Pharynx Salivary Glands

Secrete enzymes for breakdown of food

Esophagus

Structure/Anatomy

Stomach Fundus: top part Body: main part Pyloric: joins to small

intestine Gastric Juice

Chyme

Structure/Anatomy

Small Intestine (6m long) Duodenum Jejunum Ileum

Peristaltic Contractions and Segmental Contractions move the food through the small intestine

Liver Largest internal organ Produces and stores bile in

the gallbladder Stores glycogen Nutrient interconversion Detoxification Phagocytosis Synthesis

Structure/Anatomy

Pancreas Part of endocrine system

as well Secretes enzymes that

aid in the breakdown of all food and proteins in particular

Large Intestine Cecum Colon Rectum Anal canal

While here, chyme turns into feces

Digestion, Absorption, and Transport

Digestion: breakdown of foodAbsorption: uptake of digestive tract contents by the lining of the tractTransport: the distribution of nutrients throughout the body

Food is broken down into…

Carbohydrates Lipids a.k.a. Fat Proteins Water

We will talk more about these in the nutrition portion.

Aging and the Digestive System

As you age, like the skin, the digestive structures become thin

and do not secrete as much enzymes.