The Digestive System

SBI 3UJanuary 10th, 2013

Cells with similar functions come together to form tissues Ex: stomach includes muscle tissue 4 types of tissue: connective tissue, epithelial tissue, nervous tissue and

muscle tissue Several types of tissues that come together to perform one overall

function organs

From a Cell to a System

Organ system several organs working together to perform an important function

Maintenance of homeostasis All cell require nutrients and oxygen respiratory and

digestive systems provide these and the circulatory system ensures that all cells get these essentials

Building a Digestive System

Digestive tract = Gastrointestinal tract = Alimentary canal Digestive tract series of hollow organs joined in a long,

twisted tube from mouth to exit of body Structure allows for food to enter through mouth, nutrients to

be absorbed and wastes to be excreted

Structures, Functions, and Processes of the Digestive System

Major organs: mouth, pharynx, esophagus, stomach, small intestine, large intestine (colon), and anus

Accessory organs: salivary glands, pancreas, liver, and galbladder

Organs in Digestive Tract

Lumen: central space 5 layers of tissue

surrounding lumen1. Mucosa2. Submucosa3. A circular layer of

smooth muscle4. Longitudinal layer of

smooth muscle5. Serosa

Structure of the Wall of the Digestive Tract

Depending upon the section of the digestive tract:

-mucosa protects digestive tract wall -secretes substances and; -absorbs the end products of digestion

Structure of the Wall of the Digestive Tract - Mucosa

Lies outside the mucosa Connective tissue consisting of blood

vessels, lymphatic vessels, and nerve fibers

Structure of the Wall of the Digestive Tract - Submucosa

Layer of muscle Mouth and pharynx: consists of skeletal

muscle Rest of the digestive tract: consists of

smooth muscle and nerve fibers

Structure of the Wall of the Digestive Tract – Circular Smooth Muscle

Composed of connective tissue Forms the covering of the digestive tract

Structure of the Wall of the Digestive Tract – Serosa

Function of digestive system: change the foods you eat into chemical forms your body can use

Ingestion: food is acquired Food useful once it has been converted into

diffusible substances Prep of food for absorption is termed

digestion

Steps in Digestion

Carbs monosaccharides Proteins amino acids Fats fatty acids and glycerol 2 types of digestion: mechanical digestion &

chemical digestion

Steps in Digestion

Mechanical: in mouth and stomach Chemical: the breakdown of food into

smaller and simpler compounds

Mechanical vs. Chemical Digestion

Shredding, tearing and grinding food teeth incisors, canines and pre-molars/molars

Herbivore teeth vs. Carnivore Human teeth resemble both herbivore and

carnivore

Mechanical Digestion

Can occur once food has been broken down Food mixed with various juices from

digestive glands Enzymes act upon broken-down food Absorption: primarily in small intestine.

Large intestine only for water and some vitamins

Elimination: occurs through rectum and anus

Chemical Digestion

Begins at the oral cavity where food is manipulated by the mouth

Lips, tongue, teeth and jaw muscles used Incisors, canines, molars Salivary amylase beginning of chemical

digestion Bolus created

Steps through the Digestive Tract

Bolus passes through pharynx Epiglottis and trachea Bolus drops into esophagus

Steps through the Digestive Tract