Ch 23: The Digestive System - PowerPoint Presentation

Slide1

Ch 23: The Digestive System

Section 1: Overview of the Digestive System (pp. 852-854)Slide2

Two groups of organs: 1) Alimentary canal

- also known as gastrointestinal or GI tract - digests & absorbs food Major organs: - mouth, pharynx, esophagus, stomach, small intestine, & large intestine

Digestive System OverviewSlide3

Two groups of organs: 2) Accessory digestive organs

- teeth, tongue, & gallbladder Major digestive glands: - salivary glands, liver, & pancreasDigestive System OverviewSlide4

Digestion - the physical grinding & chemical

breakdown

of food ALL digestive systems must accomplish the following:Ingestion - placing food into digestive tractMechanical breakdown - food physically broken down into smaller pieces - allows digestive enzymes to work more efficientlyDigestive ProcessesSlide5

Chemical breakdown - particles exposed to digestive enzymes - breaks

large

molecules into smaller subunitsAbsorption - subunits transported out of digestive system…into cellsElimination - indigestible material expelled from bodyDigestionSlide6

Four basic layers of tissue: 1) Mucosa

-

inner lining of canal - secretes mucus, digestive enzymes, & hormones - absorbs nutrients - protects against infectious diseasesHistology of Alimentary CanalSlide7

Four basic layers of tissue: 2) Submucosa

- dense connective tissue under mucosal layer - rich in blood supply, lymph tissue, & nerves - elastic fibers allow stomach to regain normal shape after large mealHistology of Alimentary CanalSlide8

Four basic layers of tissue: 3) Muscularis

externa

- responsible for peristalsis (rhythmic muscular contractions that move food through the canal) Composed of two layers: a) Inner circular layer opens/closes

canal b) Outer longitudinal layer lengthens

/

shortens

canal

Histology of Alimentary CanalSlide9

Four basic layers of tissue: 4) Serosa - protective,

outermost

layer - known as the visceral peritoneumHistology of Alimentary CanalSlide10

Ch 23: The Digestive System

Section 2: Functional Anatomy of the Digestive System (pp. 858-895)Slide11

Mechanical & chemical breakdown of food: - begins in the mouth

- mouth lined with thick

stratified squamous epithelium to withstand considerable friction - breakdown of food carried out mostly by the teethMouthSlide12

Function of teeth: - to break food down into smaller

fragments

- vastly improves rate & efficiency of chemical breakdown of food in stomachTeethSlide13

Tooth “Timeline”: 1) Deciduous teeth (“

baby

teeth”) - begin appearing at 6 months; complete by age 2 - 20 total - between age 6-12, roots are reabsorbed; teeth fall out 2) Permanent teeth - 32 total - All except

wisdom teeth appear by end of adolescence - Wisdom teeth appear by age

25

(sometimes never)

TeethSlide14

Teeth 1) Incisors - front of mouth; snip off pieces

of food

2) Canines - pointed; useful for tearing 3) Premolars & Molars - back of mouth; flattened surfaces used to grind food into a pasteMouthSlide15

Functions of the tongue:- reposition & mix food

during chewing- initiates swallowing response- provides ability to manipulate sounds to form words- provides sense of tasteTongueSlide16

Features of the tongue: 1) Filiform

papillae

- cone-shaped; provide friction for manipulating foods - smallest & most numerous - contain keratin; gives them a whitish appearance 2) Fungiform papillae

- scattered across surface of tongue - contain blood

vessels

; gives them a

reddish

appearance

TongueSlide17

Features of the tongue: 3) Circumvalate

papillae

- form V-shaped row on back of tongue 4) Foliate papillae - located on the sides of the tongue; near the back**Fungiform, Circumvalate, & Foliate papillae together form the taste buds**Note:

Foliate taste buds only function during infancy & early

childhood

Tongue

Super TastersSlide18

Salivary Glands - provide first stage of chemical

digestion

- pour out saliva in response smell, feel, & taste - can even be activated by the THOUGHT of foodSalivaCancerous salivary glandSlide19

Saliva - mixture of mucus & water

- contains

Amylase (digestive enzyme that begins breaking down starches into sugars) - kills bacteria & lubricates food - taste is a direct result of food dissolving in saliva

Saliva

Donuts….Slide20

After chewing… - tongue (a muscle) presses food backward into pharynx

Pharynx

- muscular cavity connecting mouth w/ esophagus & larynx - separates food/liquids from air that is being inhaledSwallowingSlide21

Epiglottis - flap of cartilage that closes off the larynx when you swallow…prevents

food

from going into lungsSwallowingSlide22

Once past the epiglottis… - Food travels into the esophagus

- Esophagus is

collapsed when emptyEsophagusSlide23

Stomach - Expandable bag…capable of holding

2-4 liters

of food/liquid - Located on left side of abdominal cavity - Food enters at cardioesophageal sphincter & exits at pyloric sphincter (both act as “clamps” on either end of stomach)Rugae - Internal folds of stomach…allow for

expansionGastric pits - Line inner

wall…release

HCl

& various other enzymes

StomachSlide24

StomachSlide25

StomachSlide26

Stomach Functions:Stores food gradually releasing it into small intestine

Continues mechanical breakdown of food

- 3 groups of muscles “churn” foodMajor chemical breakdown of food begins*Food gradually converted into thick, acidic liquid called chymeTakes 2-6 hrs to empty stomach depending on size of meal…

StomachSlide27

Stomach functions: - “Churning” action mixes food w/ digestive enzymes -

Peristalsis

occurs in lower stomachStomachSlide28

Stomach functions: - Pyloric sphincter releases food 20-30mL

at a time

StomachSlide29

Protection:- lined with a layer of bicarbonate-rich mucus

- bicarbonate is a

base…helps to neutralize acid- damaged epithelial cells are replaced quickly StomachSlide30

Vomiting: - body’s attempt to rid itself

of substances that are

unsettling to the stomach Most commonly caused by: - extreme stretching (due to over-eating) of the stomach &/or small intestine - bacterial toxins - excessive

alcohol - spicy foods

- certain

drugs

StomachSlide31

Small intestine - Body’s major digestive organ

-

Longest part of digestive tract…approximately 20ft2 Major Functions 1) Use enzymes from liver & pancreas to break food particles into small molecules 2) Absorb molecules into the bloodstream

Small IntestineSlide32

3 Major Segments of Small IntestineDuodenum - Directly attached to stomachJejunum

Ileum

- Directly attaches to large intestineSmall IntestineInflamed Small IntestineSlide33

Duodenum - Mixes chyme from stomach with liver & pancreatic enzymes

Small IntestineSlide34

Remember: *In addition to being the major site for digestion, the small intestine is the main location for food absorption.Key structures

:

1) Numerous folds - increase the total surface area by over 600 times that of a smooth tube that is same length 2) Villi - Minute, fingerlike projections that line entire folded surface…further increase SA of intestinal wallSmall IntestineSlide35

Key structures: 3) Microvilli

- Further divisions of

villi…even more increased SA*Together, these 3 structures give the intestinal wall the surface area of a tennis court! **Without these structures, absorption would be VERY inefficient!Small IntestineSlide36

Small IntestineSlide37

Key structures: 4) Circular folds

- permanent folds; about

1cm deep - forces chyme to slowly spiral as it moves through canalSmall IntestineSlide38

Liver - Perhaps the most versatile organ - Largest gland

in the body

FunctionsStoring fats & carbohydrates for energyRegulating blood glucose levelsSynthesizing blood proteinsStoring iron & some vitamins

Detoxifying harmful substances we ingestLiverSlide39

Bile - Complex mixture of bile salts, water, & cholesterol - Acts as a detergent or

emulsifying

agent that causes fat particles to be dissolved into microscopic particles that can be broken down by other enzymes - Stored in gall bladder & released into small intestine through tube called the bile ductLiverNormal Liver

Fatty LiverCirrhosis of the LiverSlide40

Pancreas - Small organ sitting between stomach & small intestine - Produces a “soup” of

enzymes

that can break down the 3 major types of nutrients:CarbohydratesLipidsProteins - Insulin is produced herePancreasSlide41

Large Intestine - Wider diameter, but only half as long as small intestine

- Does not participate in

digestion - Absorbs majority of water in food - Eliminates indigestible food in form of feces - Not essential for lifeComposed of 2 Main Sections:ColonRectum

Large IntestineSlide42

Divisions of the Colon: 1) Cecum - Connection between sm. & lg. intestine

-

Appendix (collection of lymph tissue) attached here 2) Ascending 3) Transverse 4) Descending 5) S-shaped sigmoid**Goblet cells…part of lining of lg. intestine…produces mucous that acts as a lubricantLarge IntestineSlide43

Large IntestineSlide44

Bacterial Flora: - various bacteria colonize

the large intestine

- ferment & break down indigestible carbohydrates - help to synthesize Vitamins B and KLarge IntestineSlide45

Ch 23: The Digestive System

Section 3: Physiology of Chemical Digestion/Absorption (pp. 895-901)Slide46

Digestion is controlled by: 1) the parasympathetic nervous system 2)

hormones

Stimuli include: 1) stretch of the organ 2) pH of the stomach contents 3) presence of broken down food particlesDigestive System - ControlSlide47

Digestive Structures & SecretionsSite

Source

SecretionResultsMouthSalivary glandsAmylase

Breaks down starch into disaccharides

Mucus,

water

Lubricates,

dissolves food

Stomach

Cells lining stomach

Small Intestine

Liver

Pancreas

Intestine

Overview of DigestionSlide48

Digestive Structures & SecretionsSite

Source

SecretionResultsMouthSalivary glandsAmylase

Breaks down starch into disaccharides

Mucus,

water

Lubricates,

dissolves food

Stomach

Cells lining stomach

Hydrochlori

c acid

Kills bacteria,

dissolves minerals

Pepsin

Breaks

down proteins into peptides

Mucus

Protects stomach

lining

Small Intestine

Liver

Pancreas

Intestine

Overview of DigestionSlide49

Digestive Structures & SecretionsSite

Source

SecretionResultsMouthSalivary glandsAmylase

Breaks down starch into disaccharides

Mucus,

water

Lubricates,

dissolves food

Stomach

Cells lining stomach

Hydrochlori

c acid

Kills bacteria,

dissolves minerals

Pepsin

Breaks

down proteins into peptides

Mucus

Protects stomach

lining

Small Intestine

Liver

Bile

Emulsifies lipids

Pancreas

Sodium

bicarbonate

Neutralizes

acidic chyme from stomach

Amylase

Breaks down starch into disaccharides

Protease

Breaks down

proteins into peptides

Lipase

Breaks down lipids

Intestine

Peptidase

Breaks

down peptides into amino acids

Disaccharidase

Converts disaccharides

into

monosaccharides

Overview of DigestionSlide50

Overview of DigestionSlide51

Ch 23: The Digestive System

Section 3: Homeostatic ImbalancesSlide52

Dental cavities: - gradual demineralization

of tooth

enamel - caused by dental plaque (sugar, bacteria, & other debris) that sticks to teeth - bacteria secrete acid that dissolves calcium in teethHomeostatic ImbalancesSlide53

Gingivitis: - caused when plaque begins to calcify & harden

- calcified plaque separates teeth from gums - bacteria enter separation site & infect gumsHomeostatic ImbalancesSlide54

Periodontitis: - autoimmune disorder that destroys ligament holding tooth in

socket

- accounts for 80-90% of tooth loss in adultsHomeostatic ImbalancesSlide55

Gastritis: - inflammation that is caused by anything that interferes with the mucus

layer on the inside of the

alimentary canalGastric ulcers: - erosion of the stomach wall - usually caused by bacterial infection or hypersecretion of digestive enzymes

Homeostatic ImbalancesSlide56

Heartburn: - burning sensation caused when digestive chemicals escape the stomach & move up into the esophagus

- usually the result of eating or drinking too much - causes frequent problems in people who have a weak cardioesophageal sphincterHomeostatic ImbalancesSlide57

Gall stones: - crystals that develop in the gallbladder

- often the result of too much cholesterol or too little bile - stones can possibly be dissolved by using ultrasound - often requires surgical removalHomeostatic ImbalancesSlide58

8) Hepatitis: - inflammation of the liver caused by

viral

infectionCirrhosis: - chronic inflammation of the liver often caused by excessive alcohol consumption - liver transplant is the only effective treatment for patients with severe cirrhosis

Homeostatic ImbalancesSlide59

Bruxism: - grinding or clenching

of teeth; especially when

sleeping - can wear down or crack teeth over time - usually a sign of stressDysphagia: - difficulty in swallowing - usually due to obstruction or physical

trauma to esophagus

Homeostatic Imbalances