7a digsys ia- organs and structure

8/13/2019 7a DigSys Ia- Organs and Structure

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Digestive System I: Organs and StructureGeneral functions

Organs of the AlimentaryCanal

Mouth and Teeth

Swallowing

Pharynx, Esophagus

o Propulsion

Stomach

Linings and Mesentaries

Small Intestine

Large Intestine


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Organs of the Digestive SystemOrgans of the Alimentary Canal

Mouth

Pharynx

Esophagus

Stomach

Small intestine

Large intestine

Anus

Accessory Digestive Organs

Salivary glandsTeeth

Pancreas

Liver

Gall bladder


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Mouth (Oral Cavity) Anatomy


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Processes of the MouthMechanical Processes

Mastication (chewing)of food using temporaland masseter musclesand teeth

Wetting masticated food

with saliva Initiation of swallowing

by the tongue

Chemical Processes

Allowing for the senseof taste

Digestion of some starch by salivary amylase insaliva


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TeethThe role is to masticate (chew) food

Humans have two sets of teeth

Deciduous (baby or milk) teeth

20 teeth are fully formed by age two

Permanent teeth

Replace deciduous teeth beginning between the ages of 6 to 12

A full set is 32 teeth, but some peopledo not have wisdom teeth

Classification of Teeth Incisors (clipping, nibbling)

Canines (siezing)

Premolars (grinding)

Molars (grinding)


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Regions of a ToothCrown exposed part

Outer enamel

Dentin

Pulp cavity

Neck

Region in contact with thegum

Connects crown to root

Root

Periodontal membraneattached to the bone

Root canal carrying bloodvessels and nerves


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Pharynx Anatomy and Function


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Organs of the Alimentary Canal

Mouth and Teeth

Swallowing

Pharynx, Esophagus

o Propulsion Stomach


Small Intestine

Large Intestine


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Tongue

Trachea

Pharynx

EpiglottisGlottis

Bolus of food

Upper esophageal sphincter is contracted. Duringthe buccal phase, the tongue presses against the hardpalate, forcing the food bolus into the oropharynx

where the involuntary phase begins.

1

Deglutition



Epiglottis

Esophagus

Uvula

Bolus

The uvula and larynx rise to prevent food fromentering respiratory passageways. The tongue blocksoff the mouth. The upper esophageal sphincter

relaxes, allowing food to enter the esophagus.

2

Deglutition



Bolus

The constrictor muscles of the pharynx contract,forcing food into the esophagus inferiorly. The upper

esophageal sphincter contracts (closes) after entry.

3

Deglutition


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Mouth and Teeth

Swallowing

Pharynx, Esophagus



Small Intestine

Large Intestine


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EsophagusRuns from pharynx to stomachthrough the diaphragm

Conducts food by peristalsis(slow rhythmic squeezing)

Passageway for food only(respiratory system branches off

after the pharynx)Esophageal mucosa containsstratified squamous epithelium

Changes to simple columnarat the stomach

Esophageal glands in submucosasecrete mucus to aid in bolusmovement


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PropulsionPeristalsis alternatingwaves of contraction

Segmentation movingmaterials back and forth toaid in mixing

Peristalsis Movie Online

Peristalsis X-ray movie
http://health.howstuffworks.com/adam-200088.htmhttp://health.howstuffworks.com/adam-200088.htmhttp://www.gerd.com/intro/noframe/gena_shk.htmhttp://www.gerd.com/intro/noframe/gena_shk.htmhttp://www.gerd.com/intro/noframe/gena_shk.htmhttp://www.gerd.com/intro/noframe/gena_shk.htmhttp://health.howstuffworks.com/adam-200088.htmhttp://health.howstuffworks.com/adam-200088.htm


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Mouth and Teeth

Swallowing

Pharynx, Esophagus



Small Intestine

Large Intestine


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Stomach Anatomy and Function

Muscularisexterna

cardiac sphincterserosa

rugae ofmucosa

Functions of the StomachActs as a storage tank for food

Site of initial food breakdown

Chemical breakdown of protein begins

Delivers chyme (processed food) to the

small intestine

cardiac region

fundus region

pylorus region

body region


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Propulsion in the StomachFood must first be well mixed

Rippling peristalsis occurs in the lower stomach

The pylorus meters out chyme into the small intestine (30 mlat a time)

The stomach empties in four to six hours

Figure 14.15Stomach peristalsis interactive animation online
http://www.bbc.co.uk/science/humanbody/body/factfiles/stomach/stomach_peristalsis.shtmlhttp://www.bbc.co.uk/science/humanbody/body/factfiles/stomach/stomach_peristalsis.shtml


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Specialized Mucosa of the Stomach

Simple columnar epithelium

Mucous neck cells produce a sticky alkalinemucus

Gastric glands secretegastric juice

Chief cells produce protein-digestingenzymes (pepsinogens)

Parietal cells produce

hydrochloric acid Endocrine cells

produce gastrin


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Figure 23.18

St om ach l um en Chief cel l

Parietal cel l

Inter-s t i t i a l f lu id

Carbonicanhydrase

Alkalinetide

HCO 3

Bl oodcapi l l a ry

CO 2

Cl

CO 2 + H 2O

H2CO 3

HCO 3 - Cl antiporter

HCO 3

H+

Cl Cl l

K+ K+

H+

H+-K+ATPase

HCI

Chief Cells Utilize Blood CO 2 and Interstitial Cl to Produce HCl


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Serous Membranes- Thin linings of organs and body wall

Parietal serosae lineinternal body walls Visceral serosae cover internal organs

Mesenteries are double layers of peritoneum

Routes for blood vessels, lymphatics, and

nerves; holds organs in place and stores fat Retroperitoneal organs lie posterior to the

peritoneum (e.g. the liver); intraperitoneal (peritoneal) organs are surrounded by the peritoneum


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Mesenteries of the StomachLayers of peritoneum (serosa) attached

to the stomach = mesentaries

Lesser omentum attaches the liver to thelesser curvature

Greater omentum attaches the greatercurvature to the

posterior body wall

Contains fat to insulate,cushion, and protectabdominal organs

Lesseromentum

Greateromentum


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Mouth and Teeth

Swallowing

Pharynx, Esophagus



Small Intestine

Large Intestine


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Small Intestine The bodys major digestive organ

Site of nutrient absorption into the blood

Muscular tube extending form the pyloricsphincter to the ileocecal valve

Suspended from the posterior abdominal wall by the mesentery (omenta)

Regions of the Small Intestine

Duodenum

o Attached to the stomach

o Curves around the head of the pancreas

Jejunum

o Attaches anteriorly to the duodenum

Ileum

o Extends from jejunum to large intestine


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Four Tunics of the Alimentary Canal

1.

2.

3.

4.


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Absorption in the Small Intestine

Absorptive Structures

Absorptive cells

Blood capillaries

Lacteals (specialized lymphatic capillaries)

Folds in the Small Intestine

Called circular folds or plicae circulares

Deep folds of the mucosa and submucosa

Do not disappear when filled with foodPeyers patches in submucosa (collections of lymphatic tissue)

Intestinal crypt epithelium Secretory cells that produce intestinal juice Cells that make antimicrobial chemicals Stem cells


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Mouth and Teeth

Swallowing

Pharynx, Esophagus



Small Intestine

Large Intestine


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Functions of the Large IntestineStructures

Cecum saclike first part of the large intestine

Appendix Accumulation of lymphatic tissue that sometimes

becomes inflamed (appendicitis)

Hangs from the cecum

Colon

Ascending

Transverse

Descending

S-shaped sigmoidal

Rectum

Anus external body openingFunctions

Absorption of water

Elimination of indigestible food from the body as feces

Does not participate in digestion of food

Goblet cells produce mucus to act as a lubricant


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M difi i h M l i E i


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Modifications to the Muscularis Externa inthe Large IntestineLongitudinal smoothmuscle is reduced tothree bands (teniae coli);circular muscles still

present

Muscle bands have somedegree of tone

Walls are formed into

pocketlike sacs calledhaustra

Di i S I O d S


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Mouth and Teeth

Swallowing

Pharynx, Esophagus



Small Intestine

Large Intestine

7a digsys ia- organs and structure

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