Digestive System The digestive - PowerPoint Presentation

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Digestive System

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The digestive system is responsible for the physical and chemical

breakdown

of food so it can be taken into the bloodstream and used by body

cells

and

tissues.

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The Alimentary Canal

:

Long

muscular tubeBegins at the mouth and includes the pharynx, esophagus, stomach, small intestines, large intestines, and the anus.The Accessory Organs:The salivary glands, tongue, teeth, liver, gallbladder, and pancreas

The Digestive System includes:

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Mouth,

buccal

, or oral cavity

A. Receives food as it enters the bodyB. Actions in the mouth1

.

Food is

tasted2. Broken down physically by the teeth3. Lubricated and partially digested by saliva4. Swallowed

Where does digestion start

?

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Special structures in the mouth

2. Break down food physically by chewing and grinding the food, a process called

mastication

Teeth

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Muscular organ

2. Contains special receptors called

taste

buds that allow person to taste sweet, salt, sour, and bitter sensations3. Also aids with chewing and swallowing of foodTongue

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Hard palate

1. Bony structure that forms the

roof

of the mouth2. Separates the mouth from the nasal cavitiesWithin the mouth:

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Soft palate

1. Located

behind

the hard palate2. Separates the mouth from the nasopharynx

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Uvula

(a) Cone-shaped muscular

structure

(b) Hangs from the middle of the soft palate(c) Prevents food from entering the

nasopharynx

during

swallowing

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1.

Three

pairs of glands

Parotid, sublingual, and submandibular 2. Produce a liquid called saliva(a) Lubricates the mouth during speech and chewing(b) Moistens food so it can be swallowed easily(c) Also contains an enzyme called salivary amylaseaa. Substance speeding up a chemical reaction

bb. Begins the

chemical

breakdown of carbohydrates or starches into sugars that can be taken into the body Salivary Glands

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A. After

the food is chewed and mixed with saliva, it is called a

bolus

and it enters the pharynx or throatB. Tube that carries both air and foodC. Carries the air to the trachea or windpipeD. Carries food to the esophagusPharynx or Throat

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When bolus is swallowed, muscle action causes the

epiglottis

to close over the larynx

2. Prevents bolus from entering respiratory tract3. In this way, the bolus enters the esophagusIn the esophagus:

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www.youtube.com/watch?v=1YfO11Pry6Y&feature=player_detailpage

Normal Swallow Animation - Thick and Easy Dysphagia - YouTube

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Muscular tube

dorsal

to the trachea

Receives bolus from the pharynx and carries it to the stomachRelies on a rhythmic, wavelike involuntary movement of its muscles, called peristalsis, to move the food in a forward directionEsophagus

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Enlarged

part of the alimentary canal

Receives the food from the

esophagusMucous membrane lining contains folds called rugae, which disappear as the stomach fills with food and expands Stomach

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Circular

muscle between the esophagus and stomach

Closes

after food enters the stomachPrevents food from going back up into the esophagusCardiac Sphincter

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Circular muscle between the stomach and small intestine

Keeps food in the

stomach

until it is ready to enter the small intestineFood usually remains in the stomach for about one to four hoursPyloric Sphincter

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Produced

by glands in the stomach

Converts food into a semi fluid material called chymeGastric Juices

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Juices

contain

hydrochloric acidKills bacteriaFacilitates the absorption of ironActivates the enzyme pepsinGastric Juices

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Contain enzymes:

Lipase

, which begins the chemical breakdown of fats

Pepsin, which starts protein digestionIn an infant, the enzyme rennin is secreted1) Aids in the digestion of milk2) Not present in an adultGastric Juices

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Coiled section of the alimentary canal about

20

feet long and 1 inch in

diameterReceives food, in form of chyme, from stomachSmall Intestine

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There are three sections:

Duodenum—

first 9-10 inches

Jejunum—next 8 feetIleum—final 12 feetSmall Intestines

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The first 9-10 inches

Bile

from the gallbladder and liver enter this section through ducts or tubes

Pancreatic juices from the pancreas also enter this section through ducts or tubes.Small Intestines--Duodenum

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Eight

feet long

Forms the

middle section of the small intestineSmall Intestines--Jejunum

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Final 12 feet

of the small intestine

Connects with the large intestine at the

cecumCircular muscle called the ileocecal valve separates the ileum and cecum and prevents food from returning to the ileum.Small Intestines--Ileum

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Completes the process of digestion

Absorbs the products of digestion into the bloodstream for use by

body cells

Functions of the Small Intestines:

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Produced by the small intestine

Contain the enzymes maltase,

sucrase

, and lactase, which break down sugars into simpler formsContain enzymes known as peptidases, which complete the digestion of proteinsContain the enzyme steapsin, which aids in the digestion of fatIntestinal Juices of the Small Intestines

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Liquid that enters small intestine from

liver

and gallbladder

2. Emulsifies or physically breaks down fatsBile

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1.Liquid that enters small intestine from

pancreas

2. Contains

enzymes that complete the process of digestion A) Pancreatic amylase or amylopsin, which acts on sugars B) Trypsin and chymotrypsin, which act on proteins C) Lipase or steapsin, which acts on fatsPancreatic Juice

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Fingerlike

projections that line wall of small intestine

Allow food to be absorbed or taken into

bloodstreamContain blood capillaries and lacteals Small Intestine--Villi

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Blood capillaries absorb the digested

nutrients

and carry them to the liver where they are stored or released into general circulation for use by body cells

Small Intestine—Blood Capillaries

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Lacteals

pick up most of the digested fats and carry them to the thoracic duct in the lymphatic system, which releases them into the circulatory system

Small Intestines--

Lacteals

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When food has completed its passage through the small intestine only wastes, indigestible materials, and excess water remain

Small Intestines

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Final

section of the alimentary canal

About

5 feet long and about 2 inches in diameterLarge Intestines

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Absorption

of water and any remaining nutrients

Storage of indigestible materials before they are eliminated from the body Synthesis (formation) and absorption of some B-complex vitamins and vitamin K by bacteria present in intestine Transportation of the waste products out of the alimentary canalLarge Intestines--Functions

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Cecum:

First

section

Connects with the ileum of the small intestineContains a small projection called the vermiform appendixLarge Intestines--Sections

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Ascending colon:

continues up on the right side of the body from the cecum to the lower part of the

liver

Large Intestines--Sections

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Transverse

colon:

extends across the abdomen, below the liver and stomach, but above the small intestineLarge Intestine--Sections

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Descending colon:

extends down the left side of the body

Large Intestines--Sections

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Sigmoid

colon:

Connects with

descending colonS-shaped section that joins with the rectumLarge Intestines--Sections

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Rectum:

Final 6 to 8inches

Storage area for the

indigestibles or wastesHas a narrow canal called the anal canal, which opens at a hole called the anusFecal material or stool, the final waste product of the digestive processLarge Intestines--Sections

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Liver:

Largest

gland in the body

Accessory organ for the digestive tractLocated under the diaphragm in the upper right quadrant of the abdomen Accessory Organs

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1. Secretes

bile

a. Used to emulsify or physically break up fats b. Also makes fats water soluble, which is necessary for absorption 2. Stores sugar in the form of glycogen a. Glycogen is converted to glucose

b. Released

into the bloodstream when additional blood sugar is needed

3. Stores iron and certain vitamins 4. Produces heparin, a substance that prevents clotting of the blood 5. Produces blood proteins such as fibrinogen and prothrombin, which aid in the clotting of blood

6. Produces

cholesterol

7.

Detoxifies

(renders less harmful) substances such as alcohol and pesticides, and destroys bacteria that have been taken into the blood from the intestine

 

Functions of the

Liver

:

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Gallbladder:

1. Small muscular

sac2. Located under the liver and attached to it by connective tissue 3. Stores and concentrates bile, which it receives from the liver4. When the bile is needed in the digestive tract to emulsify fats, it contracts and pushes the bile through the common bile duct into the duodenumAccessory Organs

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Pancreas:

1. Fish-shaped organ located behind the

stomach

 2. Produces pancreatic juices a. Juices enter duodenum through pancreatic duct b. Contain

enzymes

to digest food

(1) Pancreatic amylase or amylopsin to break down sugars (2) Trypsin and chymotrypsin to break down proteins (3) Lipase or steapsin to act on fats3. Produces insulin a. Secreted into the bloodstream b. Regulates the metabolism or burning

of

carbohydrates to

convert

glucose

(

blood sugar) to energy

Accessory Organs