digestive system powerpoint lecture

7/30/2019 Digestive System Powerpoint Lecture

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Biology II

DIGESTIVE SYSTEM


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FUNCTIONS OF THE DIGESTIVE SYSTEM

Ingestion The taking in of food.

Digestion Physical and chemical breakdown of

food into smaller molecules.

Absorption Movement of nutrients into the

bloodstream.

Defecation Removal of indigestible waste.


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MOUTH ANATOMY

Three pairs of salivary glands empty secretions intothe mouth

1. Parotid glands

2. Submandibular glands

3. Sublingual glands

Functions of saliva:

Dissolves chemicals in food so they

can be detected by the taste buds.

Moistens food so that it can be swallowed.

Contains salivary amylase, a digestive enzyme.


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DIGESTION IN THE MOUTH

There are two types of digestion:

Mechanical digestion, which is the physical process

of breaking food into smaller pieces.

Chemical digestion, when enzymes catalyze

chemical reactions that lead to the breakdown of

food molecules.


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DIGESTION IN THE MOUTH

Mechanical digestion in the mouth occurs throughmastication, or the chewing and grinding of food by

the teeth.

Chemical digestion occurs when salivary amylase

catalyzes the breakdown of starch (polysaccharide)into maltose (disaccharide).


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Teeth

(Incisors)

Hard Palate

Soft Palate

Uvula

Tongue

Frenulum

Palatine

Tonsils

Palatal

Arches

Vestibule (betweenlower lip and gingiva)


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TEETH

The outermost layer of the tooth is enamel. Made of calcium phosphate, the hardest biologically-made

substance.

Most of the inner tooth is dentin, which is similar to

bone except without any living cells.

The living cells of the tooth are located in the pulp

cavity.

All blood vessels and nerves into this cavity come through

the root canals at the base of the tooth.


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Crown

(Enamel)

Pulp Cavity

Gingiva

Bone Tissue

(Mandible)

Root

Canal

Dentin


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TOOTH DISORDERS

Cavities orcaries occur when

naturally-occuring bacteria withinthe mouth overgrow due to thepresence of food particles.

The bacteria produce acid as a wasteproduct, which dissolves the calciumphosphate enamel.

If cavities are allowed to becometoo deep, a root canal will cleanout and dissolve all the tissue in the

pulp cavity, leaving an antibioticpaste behind.

The tooth no longer has any living cellsat this point.


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TYPES OF TEETH

Incisors are blade-shaped teeth at the front of themouth.

Clipping or cutting.

Cuspids (canines) are cone-shaped with a pointed

tip.

Tearing or slashing.

Bicuspids and molars have flattened tops.

Crushing, mashing, or grinding.

Wisdom teeth are an additional set of molars that

often develop in locations where they cannot erupt.

Vestigial structures.


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Incisors

Cuspid

Bicuspids

Incisors

Cuspid

Bicuspids


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PHARYNX

Food is formed into achewed,moistened ball called a bolus.

The bolus is pushed back toward

the pharynx with the tongue.

While swallowing, all

passageways except to the

esophagus are blocked.

The uvula moves backwards,

blocking the nasal cavity.

The epiglottis folds down, blocking

the trachea.


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ESOPHAGUS

The bolus movesthrough the

esophagus by a

series of smooth

muscle contractionscalled peristalsis.

The bolus

eventually enters

the stomachthrough the cardiac

sphincter.


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Esophagus

Fundus

CardiacSphincter

Lesser

Curvature

Greater

Curvature

Body (Rugae)

Pyloric

RegionPyloricSphincter

Duodenum


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STOMACH

The stomach is a muscular organ made of foursections:

Cardiac Region closest to the esophagus and heart.

Fundus Superior bulge in stomach.

Body Middle section Pyloric Inferior region, closest to the small intestines.

The stomach has internal folds called rugae, thatincrease the surface area for digestion.

The innermost lining of the stomach is simplecolumnar epithelium.


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STOMACH

The cardiac sphincteris a ring of smooth

muscle intended to allow

food into the stomach,

but not out. Exceptions include

vomiting, heartburn, acid

reflux.


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STOMACH

Presence of food in the stomach stimulates the releaseof the hormone gastrin.

Gastrin causes the stomach glands to produce:

Pepsinogen, an inactive enzyme produced by chief cells.This converts to pepsin, an active enzyme that breaks downproteins into amino acids.

A layer ofmucus to protect the stomach from being dissolvedor digested.

Hydrochloric acid lowers the pH of the stomach contents,

which activates pepsin. This is produced by parietal cells. No absorption occurs in the stomach, except for aspirin

and alcohol.


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Mucus

Cells

RugaeChief

Cells

Parietal

Cells


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STOMACH-INTESTINES

The partially digested food is now referred to aschyme.

The stomach will release small amounts (30mL) of

chyme into the small intestine at a time through the

pyloric sphincter.


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SMALL INTESTINES

The first section ofthe small intestines

is the duodenum.

This is where most

of the actual

digestion occurs.

Digestive secretions

from the pancreas

and liver (gallbladder) are both

sent here.


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Falciform Ligament

Liver

Duodenum

Gall Bladder

Pancreas


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DUODENUM

The pancreas releases bicarbonate and enzymes

into the duodenum:

Bicarbonate neutralizes the stomach acid, stopping the

action of pepsin..

Pancreatic amylase (starch maltose)

Lipase (Lipids Fatty acids)

Nuclease(DNA / RNA Nucleotides)

Trypsin(Protein Amino acids)

The liver releases bile, which separates fats intosmaller droplets to increase the rate of digestion by

lipase.


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JEJUNUM-ILEUM

Food is moved throughthe small intestine by

peristalsis, just like in

the esophagus.

Absorption of the end-products of digestion

occurs all along the

jejunum and ileum.

Villi are present in all cells

along the intestines to

increase the surface area

for absorption.


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JEJUNUM-ILEUM

Active transport movesthe substances

(monosaccharides,

amino acids, fatty acids,

etc) across the cells of

the intestines into theblood.

Substances are then

transported to the liver

by the hepatic portal

vein.


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LARGE INTESTINE

The beginning of the large intestine is the cecum. The appendix is attached here.

Three segments of the large intestine:

Ascending colon

Transverse colon

Descending colon

Ends with the rectum.


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Oral Cavity

Sublingual GlandSubmandibular

Gland

Esophagus

Parotid Gland

UvulaTongue

Pharynx

Trachea

Diaphragm

SpleenLiver

Stomach

Pancreas Transverse ColonDescending Colon

Jejunum

Sigmoid Colon

Rectum

Anus

Ascending Colon

ileum

Appendix


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LARGE INTESTINE

No digestive enzymes are present here. Bacteria that reside in the large intestine digest some

of the remaining nutrients, producing vitamins K, B,

and some gases.

Water and vitamins are absorbed, while theremaining material is eliminated as feces.

Undigested food residue

Mucus

Bacteria

Water


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LARGE INTESTINE

Movement through the largeintestine is slow, but powerful.

Peristalsis occurs 3-4 times per day.

A buildup of feces in the rectum

causes the defecation reflex. The internal anal sphincter (involuntary

smooth muscle) is relaxed.

The external anal sphincter (voluntary

muscle) must be relaxed beforedefecation can actually occur.


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ACCESSORY ORGANS

The pancreas, in addition to producing digestiveenzymes, also controls blood sugar.

Islets of Langerhans contain the cells that actually

produce these hormones.

Insulin Stimulates the absorption of glucose from bloodand production of glycogen for storage.

Glucagon Stimulates the breakdown of glycogen into

glucose, raising blood sugar.

The liver, in addition to making bile, detoxifies anypoisons absorbed by the digestive tract.


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APPENDIX

The appendix is a small dead-end tube connected tothe beginning of the ascending colon.

The appendix is believed to be a vestigial structure. It used

to be a larger cecum an organ that herbivores use to

ferment and digest cellulose.


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CONNECTIVE TISSUE

The stomach is held in place with the otherabdominal organs by the greater and lesser

omentum

The intestines are held together by mesentary.


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MUMPS

A viral infection that causespainful swelling of the salivary

glands, especially the parotid

gland.

Airborne and highlycontagious.

Can be vaccinated against.


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HEARTBURN

Influx of stomach acid into the esophagus. Can be the result of excessive acid production in the

stomach, or a faulty cardiac sphincter.


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PEPTIC ULCERS

An erosion of the innerstomach or duodenum lining.

Causes include:

Inflammation from bacterial

infection.

Certain painkillers (aspirin,

ibuprofen) can inhibit the

production of stomach mucus.

Stress (not fully understood why)


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VOMITING

There are multiple sources ofstimulation that can lead to

vomiting.

Irritation of the gastrointestinal

tract.

Irritation of the pharynx (gag

reflex)

Multiple trigger zones in the brain.

The actual process of vomitinghas several physiologic steps.


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VOMITING

Salivary glands increase production of saliva toprotect teeth from acid erosion.

A deep breath is taken to prevent aspiration.

Inhalation of foreign substances, such as vomit, can lead to

serious respiratory infections like pneumonia.

Retroperistalsis (reverse peristalsis) sweeps the

digestive tract contents through a relaxed pyloric

sphincter, into the stomach.

Abdominal muscles contract, cardiac sphincter

relaxes, and contents exit through the esophagus.


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DIARRHEA

Diarrhea is the presence of abnormally loose orliquid feces.

There are multiple types of diarrhea, all of which are

caused by an excess of water inside the intestines.

Some bacteria (Cholera, E. coli O157:H7) produce a toxinthat creates an ion imbalance in the intestines. This results

in an osmotic flow of water into the intestines.

Laxatives often contain an ion (like magnesium) that will

intentionally create an osmotic imbalance.


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LACTOSE INTOLERANCE

People that are lactose intolerant donot produce the lactase enzyme.

The gene that produces this enzyme shuts

off after infancy, when breastfeeding ends.

Undigested lactose eventually reachesthe large intestine, causing an osmotic

imbalance (diarrhea).

Bacteria are able to ferment the

lactose, producing excessive amountsof gas.


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DIABETES

The pancreas stops producing or does not produceenough insulin, resulting in high blood sugar levels.

Type I Diabetes is the result of the immune system

destroying the insulin-producing cells of the pancreas.

No insulin is produced. The patient is dependent on insulininjections.

Type II Diabetes occurs when there is an insulin

deficiency in the body, or the cells do not respond

properly to insulin. Most common cause is obesity.

digestive system powerpoint lecture

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