Digestive Powerpoint

DIGESTIVE DIGESTIVE SYSTEMSYSTEM

ANATOMICAL OVERVIEWANATOMICAL OVERVIEW2 main groups of organs:2 main groups of organs:

1.1. Alimentary canal (Gastrointestinal or GI tract)Alimentary canal (Gastrointestinal or GI tract) Made up of the mouth, pharynx, esophagus, stomach, Made up of the mouth, pharynx, esophagus, stomach,

small intestines, and large intestines (anus)small intestines, and large intestines (anus) Responsible for ingestion, digestion, absorption, and Responsible for ingestion, digestion, absorption, and

defecationdefecation Hollow tube open at both endsHollow tube open at both ends

2.2. Accessory digestive organsAccessory digestive organs Made up of teeth, tongue, salivary glands, pancreas, Made up of teeth, tongue, salivary glands, pancreas,

liver, and gallbladderliver, and gallbladder Responsible for assisting in both mechanical and Responsible for assisting in both mechanical and

chemical breakdown of ingested foodchemical breakdown of ingested food

ANATOMICAL OVERVIEWANATOMICAL OVERVIEWGENERAL GENERAL

ANATOMICAL ANATOMICAL FEATURES OF FEATURES OF THE DIGESTIVE THE DIGESTIVE SYSTEMSYSTEM

Alimentary Canal – mouthAlimentary Canal – mouth Food enters Food enters

through the through the mucous-lined mucous-lined mouthmouth or or oral cavityoral cavity

Lips (labia)Lips (labia) – – protectionprotection

CheeksCheeks – lateral – lateral wallswalls

Hard & soft palateHard & soft palate – – anterior & posterior anterior & posterior roof respectively roof respectively

VestibuleVestibule – space – space between lips & between lips & cheeks as well as cheeks as well as teeth & gumsteeth & gums

Oral cavity properOral cavity proper – area contained by the teeth – area contained by the teeth TongueTongue – muscular tissue attached to hyoid bone and – muscular tissue attached to hyoid bone and

styloid processes; involved in speech & swallowing; styloid processes; involved in speech & swallowing; papillae contain taste budspapillae contain taste buds

Lingual frenulumLingual frenulum – small fold that anchors tongue; – small fold that anchors tongue; associated with some speech impedimentsassociated with some speech impediments

Palatine and lingual tonsilsPalatine and lingual tonsils - paired lymphatic tissue - paired lymphatic tissue masses in posterior of oral cavity; defend against masses in posterior of oral cavity; defend against pathogens; make swallowing difficult when infected or pathogens; make swallowing difficult when infected or inflamedinflamed

MasticationMastication - chewing - chewing

Mouth - continuedMouth - continued

Alimentary Canal – pharynxAlimentary Canal – pharynx Divided into 3 distinct sections:Divided into 3 distinct sections:

1.1. NasopharynxNasopharynx – not involved in the digestive – not involved in the digestive systemsystem

2.2. OropharynxOropharynx – found directly in the back of the oral – found directly in the back of the oral cavitycavity

3.3. LaryngopharynxLaryngopharynx – most inferior portion, leads into – most inferior portion, leads into the esophagus; also where pharynx splits into the esophagus; also where pharynx splits into esophagus and trachea (epiglottis)esophagus and trachea (epiglottis)

Contains two different skeletal muscle layers:Contains two different skeletal muscle layers:

1.1. Inner layer – longitudinalInner layer – longitudinal

2.2. Outer layer – circularOuter layer – circular Alternating contractions of these muscles propels Alternating contractions of these muscles propels

food down toward stomach (food down toward stomach (peristalsisperistalsis))

Alimentary Canal – esophagusAlimentary Canal – esophagus The esophagus (The esophagus (gulletgullet) is basically a connecting tube ) is basically a connecting tube

between the mouth and the stomach (about 10in.)between the mouth and the stomach (about 10in.) Lining of walls consists of 4 different layers:Lining of walls consists of 4 different layers:

1.1. MucosaMucosa – inner most layer; lines lumen (cavity) – inner most layer; lines lumen (cavity) Epithelium – stratified squamous (friction) & simple Epithelium – stratified squamous (friction) & simple

columnarcolumnar Connective tissueConnective tissue Smooth muscleSmooth muscle

2.2. SubmucosaSubmucosa – soft CT; contains blood & lymph vessels, – soft CT; contains blood & lymph vessels, lymph nodes, & nerve endingslymph nodes, & nerve endings

3.3. Muscularis externaMuscularis externa – smooth muscle layer (inner = – smooth muscle layer (inner = circular, outer = longitudinal….this is opposite of the circular, outer = longitudinal….this is opposite of the muscles found in the pharynx)muscles found in the pharynx)

4.4. SerosaSerosa – outermost layer, only a single layer of cells – outermost layer, only a single layer of cells thickthick

Cells secrete serous fluid and the layer is called Cells secrete serous fluid and the layer is called visceral peritoneumvisceral peritoneum

Connects to Connects to parietal peritoneumparietal peritoneum (part of (part of mesentarymesentary) ) that lines abdominopelvic cavitythat lines abdominopelvic cavity

Alimentary Canal – stomachAlimentary Canal – stomach StomachStomach – found on left side of abdominopelvic cavity – found on left side of abdominopelvic cavity Regions of the stomach:Regions of the stomach:

CardiacCardiac – surrounds – surrounds cardioesophageal sphinctercardioesophageal sphincter (valve through which food enters from the (valve through which food enters from the esophagusesophagus

FundusFundus – expanded part of the stomach – expanded part of the stomach BodyBody – midportion – midportion Pyloric antrumPyloric antrum – narrowing – narrowing

area inferior to bodyarea inferior to body PylorusPylorus – funnel-shaped – funnel-shaped

terminal part that leads to terminal part that leads to

small intestines via the small intestines via the

pyloric sphincterpyloric sphincter

Stomach - continuedStomach - continued The stomach is about 10in. In length, but its diameter The stomach is about 10in. In length, but its diameter

is dependent upon fullness (can hold is dependent upon fullness (can hold 4L4L or or 1 gallon1 gallon of of food)food)

When less full or empty, it collapses inward creating When less full or empty, it collapses inward creating folds called folds called rugaerugae

Greater curvatureGreater curvature – convex lateral side – convex lateral side Lesser curvatureLesser curvature – concave medial side – concave medial side Acts as a temporary “storage tank” & site for food Acts as a temporary “storage tank” & site for food

breakdownbreakdown Contains a 3Contains a 3rdrd set of muscles called the set of muscles called the muscularis muscularis

externaexterna that run obliquely and churn the food as it that run obliquely and churn the food as it moves along (physical or mechanical breakdown)moves along (physical or mechanical breakdown)

Chemical breakdown of proteins starts in the stomachChemical breakdown of proteins starts in the stomach Mucosa is Mucosa is simple columnar epitheliumsimple columnar epithelium lined with lined with

gastric pitsgastric pits that lead to gastric glands that lead to gastric glands Gastric glands secreteGastric glands secrete gastric juice gastric juice

Stomach - continuedStomach - continued Stomach cells also secrete or produce:Stomach cells also secrete or produce:

Intrinsic factorIntrinsic factor – needed for absorption of vitamin – needed for absorption of vitamin BB1212 by the small intestines by the small intestines

Chief cellsChief cells – protein-digesting enzymes – protein-digesting enzymes ((pepsinogenspepsinogens))

Parietal cellsParietal cells – hydrochloric acid (HCl) used for – hydrochloric acid (HCl) used for chemical digestion (activates other enzymes)chemical digestion (activates other enzymes)

Mucous neck cellsMucous neck cells – alkaline mucus to protect – alkaline mucus to protect stomach liningstomach lining

Enteroendocrine cellsEnteroendocrine cells – local hormones (not part of – local hormones (not part of endocrine system) like endocrine system) like gastringastrin

Pyloric region is most active for digestion – the Pyloric region is most active for digestion – the partially digested and broken down food that leaves partially digested and broken down food that leaves the stomach is called the stomach is called chymechyme

Pyloric sphincterPyloric sphincter – valve that opens to allow chyme to – valve that opens to allow chyme to pass into small intestinespass into small intestines

Stomach - continuedStomach - continued

Alimentary Canal - small Alimentary Canal - small intestinesintestines Small intestines are where most digestion and Small intestines are where most digestion and

absorption takes placeabsorption takes place Extend from the pyloric sphincter to the Extend from the pyloric sphincter to the ileocecal ileocecal

valvevalve Longest part of the GI tract; 8-18 ft. (absorption); Longest part of the GI tract; 8-18 ft. (absorption);

held together and supported in the abdominal cavity held together and supported in the abdominal cavity by mesentaryby mesentary

Small Intestine - continuedSmall Intestine - continued 3 subdivisions:3 subdivisions:

1.1. DuodenumDuodenum – shortest part; place where pancreatic – shortest part; place where pancreatic enzymes (pancreatic ducts) and bile (bile ducts) enter enzymes (pancreatic ducts) and bile (bile ducts) enter the intestinesthe intestines

2.2. JejunumJejunum – middle portion of intestines – middle portion of intestines

3.3. IleumIleum – makes up over half of the length of the small – makes up over half of the length of the small intestines; joins with the large intestines at the intestines; joins with the large intestines at the ileocecal valveileocecal valve

Small Intestine - continuedSmall Intestine - continued Nearly all food and nutrient absorption takes place Nearly all food and nutrient absorption takes place

in the small intestines. 3 main structures account in the small intestines. 3 main structures account for the increased absorptive abilities:for the increased absorptive abilities:

1.1. MicrovilliMicrovilli

2.2. VilliVilli

3.3. Circular Circular foldsfolds

Small Intestine - continuedSmall Intestine - continued MicrovilliMicrovilli – tiny projections of mucosa cells that create – tiny projections of mucosa cells that create

a fuzzy surface referred to as a “a fuzzy surface referred to as a “brush borderbrush border.” .” These projections cover the surface of the villi These projections cover the surface of the villi

VilliVilli – fingerlike projections of the mucosa that – fingerlike projections of the mucosa that contain:contain: Capillary bedsCapillary beds Lymphatic capillaries called Lymphatic capillaries called lactealslacteals Both of these structures receive digested foodstuff Both of these structures receive digested foodstuff

through diffusionthrough diffusion Circular folds (plicae circularis)Circular folds (plicae circularis) – folded parts of the – folded parts of the

mucosa and submucosa layers that creates more mucosa and submucosa layers that creates more surface area (=more absorption)surface area (=more absorption)

Peyer’s patches (from lymphatic unit) are found in Peyer’s patches (from lymphatic unit) are found in large numbers near the end of the small intestines – large numbers near the end of the small intestines – help rid leftover undigested foodstuff of bacteriahelp rid leftover undigested foodstuff of bacteria

Alimentary Canal – large Alimentary Canal – large intestinesintestines Begin at the ileocecal valve; Bigger in diameter than Begin at the ileocecal valve; Bigger in diameter than

the small intestines, but only about 5ft in length and the small intestines, but only about 5ft in length and therefore much shortertherefore much shorter

Shorter length due to function:Shorter length due to function: only things absorbed are water & some vitamins (B only things absorbed are water & some vitamins (B

& K)& K)SUBDIVISIONS:SUBDIVISIONS:

1.1. CecumCecum

2.2. AppendixAppendix

3.3. Colon (4 Colon (4 parts)parts)

4.4. RectumRectum

5.5. Anal canalAnal canal

Large Intestines - continuedLarge Intestines - continued CecumCecum – 1 – 1stst part of large intestines; has the appendix part of large intestines; has the appendix

attached to it via mesentaryattached to it via mesentary AppendixAppendix – believed at one time to help digest – believed at one time to help digest

cellulose; new evidence suggests is houses “good” cellulose; new evidence suggests is houses “good” bacteria that can replenish those lost due to diseases bacteria that can replenish those lost due to diseases such as cholera and amebic dysentarysuch as cholera and amebic dysentary Inflammation – appendicitis (“bad” bacteria take Inflammation – appendicitis (“bad” bacteria take

over); appendectomyover); appendectomy Colon:Colon:

Ascending – up the right sideAscending – up the right side Transverse – across the abdominal cavityTransverse – across the abdominal cavity Descending – down the left sideDescending – down the left side Sigmoid – s-shaped, found in pelvic regionSigmoid – s-shaped, found in pelvic region

RectumRectum and and anal canalanal canal – lead to the – lead to the anusanus and contain and contain 2 sphincters: 2 sphincters: internalinternal = smooth muscle (involuntary); = smooth muscle (involuntary); externalexternal skeletal muscle (voluntary) skeletal muscle (voluntary)

Large Intestines - continuedLarge Intestines - continued Contains many Contains many goblet cellsgoblet cells in the mucosa that in the mucosa that

produce an alkaline mucus to lubricate and raise the produce an alkaline mucus to lubricate and raise the pH of fecal matter passing through itpH of fecal matter passing through it

Longitudinal muscles of the muscularis external called Longitudinal muscles of the muscularis external called teniae coliteniae coli create small pocketlike sections called create small pocketlike sections called haustrahaustra

Accessory Digestive OrgansAccessory Digestive OrgansSALIVARY GLANDSSALIVARY GLANDS 3 sets:3 sets:

1.1. ParotidParotid – large, anterior – large, anterior to ears, inflammation to ears, inflammation causes mumpscauses mumps

2.2. SubmandibularSubmandibular3.3. SublingualSublingual

Make Make salivasaliva – mixture of – mixture of mucus and serous fluidsmucus and serous fluids

Moistens and binds food Moistens and binds food into a mass called a into a mass called a bolusbolus

Contains Contains salivary amylasesalivary amylase (enzymes) – breaks down (enzymes) – breaks down starch (carbohydrates)starch (carbohydrates)

Lysozyme and IgA Lysozyme and IgA antibodies – protect antibodies – protect against bacteriaagainst bacteria

Dissolves food so it can Dissolves food so it can be tastedbe tasted

Accessory Digestive OrgansAccessory Digestive OrgansTEETHTEETH Deciduous, baby, or milk teethDeciduous, baby, or milk teeth

Begin to erupt at 6 months, Begin to erupt at 6 months, full set of 20 by 2 yearsfull set of 20 by 2 years

Begin to fall out between 6-12 Begin to fall out between 6-12 yrs oldyrs old

Permanent teethPermanent teeth All but 3All but 3rdrd molars (wisdom molars (wisdom

teeth) are erupted by end of teeth) are erupted by end of adolescenceadolescence

IncisorsIncisors – chisel-shaped, cutting – chisel-shaped, cutting CaninesCanines – eyeteeth, fangs, – eyeteeth, fangs,

tearing or piercingtearing or piercing PremolarsPremolars (bicuspids) & (bicuspids) & molarsmolars - -

grindinggrinding

Accessory Digestive OrgansAccessory Digestive OrgansTEETH (CONTINUED)TEETH (CONTINUED) 2 regions – crown & root2 regions – crown & root CrownCrown is exposed part above the is exposed part above the gingivagingiva ( (gumsgums); );

covered by covered by enamelenamel (hard but brittle) (hard but brittle) RootRoot – embedded in the jawbone and connected to – embedded in the jawbone and connected to

crown by crown by neckneckCementum Cementum

Periodontal membrane Periodontal membrane

Dentin Dentin

Pulp cavityPulp cavity

PulpPulp

Root canalRoot canal

Accessory Digestive OrgansAccessory Digestive OrgansPANCREASPANCREAS Soft, pink, triangular gland, extends from spleen to Soft, pink, triangular gland, extends from spleen to

duodenum, duodenum, retroperitonealretroperitoneal Produces enzymes that break down all categories of Produces enzymes that break down all categories of

digestible foods; digestible foods; pancreatic enzymespancreatic enzymes are secreted are secreted into the into the duodenumduodenum in an in an alkaline fluidalkaline fluid , which , which neutralizes the acidic neutralizes the acidic chymechyme coming from the coming from the stomach; also involved in endocrine activity (insulin & stomach; also involved in endocrine activity (insulin & glucagon)glucagon)

Accessory Digestive OrgansAccessory Digestive OrgansLIVERLIVER Largest gland in the body, located under the Largest gland in the body, located under the

diaphragm and more toward the right side of the diaphragm and more toward the right side of the body, made up of 4 lobesbody, made up of 4 lobes

Major digestive function is to produce Major digestive function is to produce bilebile BileBile – yellow/green watery solution that contains – yellow/green watery solution that contains

bile salts, bile pigments such as bile salts, bile pigments such as bilirubinbilirubin (used to (used to breakdown hemoglobin), cholesterol, breakdown hemoglobin), cholesterol, phospholipids, and various electrolytesphospholipids, and various electrolytes

Bile salts Bile salts emuslifyemuslify fats by breaking down large fats by breaking down large fat globules into smaller ones (increases surface fat globules into smaller ones (increases surface area so enzymes can break it down more, faster)area so enzymes can break it down more, faster)

Bile is secreted out of the liver through the Bile is secreted out of the liver through the common hepatic ductcommon hepatic duct and into the duodenum and into the duodenum through the through the bile ductbile duct

Liver also plays a role in metabolic and regulatory Liver also plays a role in metabolic and regulatory bodily activitiesbodily activities

ANATOMICAL OVERVIEWANATOMICAL OVERVIEWGALLBLADDERGALLBLADDER Small, thin-walled green sac found on the inferior Small, thin-walled green sac found on the inferior

surface of the liver.surface of the liver. Cystic ductCystic duct – collects excess bile that builds up when – collects excess bile that builds up when

food digestion is not taking place. food digestion is not taking place. The backed-up bile empties into the gallbladder and The backed-up bile empties into the gallbladder and

water is removed to make the bile very concentrated.water is removed to make the bile very concentrated. When fatty foods enter into the duodenum, a hormonal When fatty foods enter into the duodenum, a hormonal

signal is sent to the gallbladder to release the bile to signal is sent to the gallbladder to release the bile to help break down the fat in the duodenumhelp break down the fat in the duodenum

PHYSIOLOGYPHYSIOLOGYOVERVIEW OF GI PROCESSES & CONTROLSOVERVIEW OF GI PROCESSES & CONTROLS IngestionIngestion PropulsionPropulsion Mechanical digestionMechanical digestion Chemical digestionChemical digestion AbsorptionAbsorption DefecationDefecation

PHYSIOLOGYPHYSIOLOGYACTIVITIES OF THE MOUTH, PHARYNX, & ACTIVITIES OF THE MOUTH, PHARYNX, &

ESOPHAGUSESOPHAGUS Food ingestion & breakdownFood ingestion & breakdown

Mechanical digestion – masticationMechanical digestion – mastication Chemical breakdown – salivary amylase Chemical breakdown – salivary amylase

(carbohydrates)(carbohydrates) Food propulsionFood propulsion

Swallowing (Swallowing (deglutitiondeglutition) consists of 2 phases) consists of 2 phases Buccal phaseBuccal phase - voluntary, - voluntary, bolusbolus is swallowed is swallowed Pharyngeal-esophageal phasePharyngeal-esophageal phase – involuntary – involuntary

(parasympathetic)(parasympathetic) Propulsion occurs by peristalsis of smooth Propulsion occurs by peristalsis of smooth

muscles of the pharynx & esophagusmuscles of the pharynx & esophagus Uvula blocks off nasopharynx, epiglottis blocks Uvula blocks off nasopharynx, epiglottis blocks

off larynx so food can only enter into esophagusoff larynx so food can only enter into esophagus

PHYSIOLOGYPHYSIOLOGYACTIVITIES OF THE STOMACHACTIVITIES OF THE STOMACH Food breakdownFood breakdown

Mechanical Digestion – the combination of different Mechanical Digestion – the combination of different muscle layers churn the food to mix & mash it muscle layers churn the food to mix & mash it (oblique layer)(oblique layer)

Chemical Digestion – secretion of gastric juices is Chemical Digestion – secretion of gastric juices is both neural & hormonal. both neural & hormonal.

Senses stimulate the parasympathetic nervous Senses stimulate the parasympathetic nervous system to secrete more gastric juicesystem to secrete more gastric juice

Presence of food in the stomach causes a drop in Presence of food in the stomach causes a drop in pH, stimulating more production of pesinogens & pH, stimulating more production of pesinogens & HCLHCL

AbsorptionAbsorption Aspirin & alcohol are some of the very few items Aspirin & alcohol are some of the very few items

absorbed in the stomachabsorbed in the stomach Food propulsionFood propulsion

Muscle action pushes the mixed up chyme toward Muscle action pushes the mixed up chyme toward the pylorus to enter into the small intestines the pylorus to enter into the small intestines through the pyloric sphincter.through the pyloric sphincter.

4-6 hours in the stomach4-6 hours in the stomach

PHYSIOLOGYPHYSIOLOGYACTIVITIES OF THE SMALL INTESTINESACTIVITIES OF THE SMALL INTESTINES Food breakdownFood breakdown

Mechanical digestion – continues by the process of Mechanical digestion – continues by the process of peristalsis, but otherwise is pretty much complete.peristalsis, but otherwise is pretty much complete.

Chemical digestion – acidic chyme that enters the Chemical digestion – acidic chyme that enters the duodenum is neutralized by bicarbonate enzymesduodenum is neutralized by bicarbonate enzymes

Bile released from the gallbladder also enters the small Bile released from the gallbladder also enters the small intestines at the duodenum. It initiates the breakdown of fat intestines at the duodenum. It initiates the breakdown of fat (lipid) molecules(lipid) molecules

AbsorptionAbsorption Main function of the small intestines (reason for its length)Main function of the small intestines (reason for its length) Absorption of water and most nutrients is done through Absorption of water and most nutrients is done through

active transport (requires energy) and enters the capillary active transport (requires energy) and enters the capillary beds to be carried to the liverbeds to be carried to the liver

Absorption of fats occurs by diffusion (no energy needed) Absorption of fats occurs by diffusion (no energy needed) enters both capillaries & lacteals to be transported to the enters both capillaries & lacteals to be transported to the liverliver

3-6 hours3-6 hours

PHYSIOLOGYPHYSIOLOGYACTIVITIES OF THE LARGE INTESTINESACTIVITIES OF THE LARGE INTESTINES Food BreakdownFood Breakdown

Mechanical digestion – none really, just removal of water Mechanical digestion – none really, just removal of water from the fecal matterfrom the fecal matter

Chemical breakdown – no digestive enzymes produced, Chemical breakdown – no digestive enzymes produced, but bacteria help breakdown some indigestible foods but bacteria help breakdown some indigestible foods such as cellulose.such as cellulose.

These bacteria are also responsible for fecal odor and These bacteria are also responsible for fecal odor and gas gas (flatulence)(flatulence) since they create methane as a waste since they create methane as a waste product of their metabolismproduct of their metabolism

The bacteria also produce some vitamins such as B & The bacteria also produce some vitamins such as B & K that can be absorbed by the large intestinesK that can be absorbed by the large intestines

PropulsionPropulsion SegmentationSegmentation & peristalsis (haustra) (3-4 powerful & peristalsis (haustra) (3-4 powerful

contractions/day)contractions/day) DefecationDefecation

Wall of sigmoid colon & anal canal stretches, sending Wall of sigmoid colon & anal canal stretches, sending message to brain & initiating the message to brain & initiating the defecation reflexdefecation reflex

PHYSIOLOGYPHYSIOLOGY

PHYSIOLOGYPHYSIOLOGY