Digestive system
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Digestive System. A closer look. Digestive Processes. In order for our bodies to use the food we eat to grow, energize, and repair our cells, 5 digestive processes have to occur. These include: Ingestion Movement Digestion Absorption Egestion (excretion). Digestive Processes.

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Digestive System

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Digestive system

Digestive System

A closer look


Digestive processes

Digestive Processes

  • In order for our bodies to use the food we eat to grow, energize, and repair our cells, 5 digestive processes have to occur.

  • These include:

    • Ingestion

    • Movement

    • Digestion

    • Absorption

    • Egestion (excretion)


Digestive processes1

Digestive Processes

  • These processes occur at different locations along the digestive tract, which is a continuous tube from mouth to anus.

  • We are going to discuss what happens at each site as we go through the stages.

  • It will be useful to copy the following concept map and to keep adding to it as we add more details to help you stay organized.


Digestive system 3800313

NOTE: This should be a straight line in your notes

Small

Intestine

Stomach

Large

Intestine

Esophagus

Tongue

Rectum/

Anus

Mouth/

Throat

Teeth

Salivary Glands


Digestive system1

Digestive System

  • Includes organs which perform digestion tasks:

    • Digestive Tract (Gastrointestinal Tract, G. I. Tract) includes: mouth, esophagus, stomach, small intestine, large intestine or colon, and anus.

    • Accessory Structures include:, tongue, salivary glands, liver, gall bladder and pancreas.


Digestion

Digestion

  • The process in our bodies that breaks down food for use by our cells. This is done in two ways:

    • Mechanical: our teeth chewing through the food

    • Chemical: enzymes breakdown food into absorbable molecules.


Mouth where it all begins

Mouth (where it all begins)

Hard Palate

  • Four main parts of the mouth

    • Teeth

    • Tongue

    • Salivary Glands

    • Hard and Soft Palates

Uvula


Mouth

Mouth

  • Teeth (Chewing)

    • Mechanical Digestion

    • Are covered by enamel, the hardest structure of the body

    • Their movements slice, tear, grind and mix food

    • Incisors: snap off pieces of food

    • Canine: tearing pieces apart

    • Premolars & molars: grind food to a paste

How many teeth in adult humans?


Tongue

Tongue

  • Floor of oral cavity

  • Composed of voluntarily controlled muscle tissue

  • Role: Guides food during chewing and swallowing

  • Major taste buds are embedded here.

    • Salty, sweet, sour, bitter


Salivary glands

Salivary Glands

  • Release saliva in response to the smell, taste, and thought of food

  • First example of chemical digestion:

    • Contains Amylase: an enzyme that begins breakdown of starch into simple sugars, like glucose or table sugar.

    • Interesting Fact: We secrete about 1-2L of saliva per day!


Hard soft palates

Hard & Soft Palates

  • Separate mouth from nasal

    cavity, so food doesn’t go up your nose!

  • Located at the roof of your mouth.

    Uvula (dangles)

  • Just beneath the soft palate

  • Prevents food from entering nasal passages by raising up.


Digestive system 3800313

Soft Palate

Hard Palate

Tongue

Uvula

Epiglottis

Trachea


Recap mouth

Recap (Mouth)

  • Food enters

  • Teeth rip, tear, and chew into smaller pieces to swallow

  • At the same time, Salivary Glands are stimulated to release saliva which contains amylase.

  • Tongue pushes bolus to back of pharynx (throat) and the uvula elevates, closing off the nasal passage. The bolus now pushes the epiglottis which closes the opening of the larynx, preventing the food from entering the wrong tube, which results in choking


Esophagus

Esophagus

  • Muscular tube which extends from pharynx (throat) to the stomach

  • Swallowing initiates peristalsis, a wave of contraction which initiates just above the “bolus” (substance) and moves it towards the stomach.

  • This movement also occurs in the stomach and in the intestines.

http://pennhealth.com/health_info/animationplayer/


Esophagus1

Esophagus

  • Secretes mucus (along with the rest of the digestive tract)

  • This lubricant decreases the likelihood of the esophagus getting damaged by any sharp edges from the food entering.

    • Mucus also protects esophagus from acid and enzymes in gastric juice if reflux were to occur.

http://digestive.niddk.nih.gov/ddiseases/pubs/gerd/


Digestive system 3800313

NOTE: This should be a straight line in your notes

Small

Intestine

Stomach

Mechanical: Peristalsis

Large

Intestine

Esophagus

Tongue

Rectum/

Anus

Mouth/

Throat

Mechanical: Chewing

Chemical: Starch/Amylase

Teeth

Salivary Glands


Stomach

Stomach

  • Separated from esophagus by the Gastro esophageal sphincter

  • Expandable muscular J-shaped sac that can hold up to 2-4 liters of food and liquid

  • Secretes mucous to protect lining cells

  • Contents are held in the stomach by the pyloric sphincter, ring of circular muscle, which separates the stomach from upper small intestine


Stomach1

Stomach

  • 3 Functions

    • Stores food and releases it gradually into the small intestine

    • Assist in mechanical breakdown of food by peristalsis and contractions of muscular walls

    • Chemical breakdown of food by enzymes and other substances.


Stomach2

Stomach

  • Secretions (continued)

    • Gastrin: hormone that stimulates secretion of Hydrochloric acid (HCl)

    • Pepsinogen: inactive form of enzyme is activated by HCl and transformed into pepsin which helps breakdown proteins into amino acids (smaller units).


Stomach3

Stomach

  • Food is gradually converted into a thick liquid called chyme which consists of partially digested food and digestive secretions.

  • Chyme is propelled towards small intestine

  • The Pyloric sphincter lets a teaspoon of chyme into the small intestine during each contraction

  • Takes around 2-6 hours to empty stomach


Digestive system 3800313

NOTE: This should be a straight line in your notes

Mechanical: Muscle Contractions

Mechanical: Peristalsis

Small

Intestine

Stomach

Mechanical: Peristalsis

Chemical: Pepsin (Proteins), HCl

Large

Intestine

Esophagus

Tongue

Rectum/

Anus

Mouth/

Throat

Mechanical: Chewing

Chemical: Starch

Teeth

Salivary Glands


Small intestine s i

Small Intestine (S. I.)

  • Narrow tube (1-2 inches in diameter)

  • Longest part of digestive tract

  • Split into three parts: duodenum, jejunum, and the ileum

  • Function: to digest food into small molecules and absorb into blood stream and lymph vessels.


Small intestine s i1

Small Intestine (S. I)

  • Helped by three other sources:

    1. Liver: Has many functions in our bodies. In digestion, it produces bile which is stored in the gall bladder, then released in the S. I.

    • Bile is made up of bile salts, water, and other salts and assist in the breakdown of lipids.

http://zap.intergate.ca/images/liver%20image.jpg


Small intestine s i2

Small Intestine (S. I.)

  • 2. Gall Bladder stores bile until it’s needed for digestion

http://www.nlm.nih.gov/medlineplus/ency/imagepages/19260.htm


Small intestine s i3

Small Intestine (S. I.)

  • 3. Pancreas

    • Located between stomach and S. I.

    • Cells produce pancreatic juice which neutralizes the acidic chyme it receives from the stomach

    • Digests carbohydrates, proteins, and lipids

    • Contains water, sodium bicarbonate, and many enzymes

    • YouTube - Pancreas - "Weird Al" Yankovic

http://www.nlm.nih.gov/medlineplus/ency/imagepages/17194.htm


Small intestine s i4

Small Intestine (S. I)

  • Pancreas (cont’d)

    • Enzymes include:

      • Amylase Carbohydrates

      • Lipase Lipids

      • Proteases Proteins and peptides


Small intestine s i5

Small Intestine (S. I.)

  • Specialized cells within the wall complete the process. At the same time, nutrients are absorbed into the blood stream.

  • The numerous folds and projections, called villi, give the internal surface area a much larger surface for absorption.

http://www.udel.edu/biology/Wags/histopage/wagnerart/anaglyphpage/anaglyph.html


Small intestine s i6

Small Intestine (S. I.)

  • The area of absorption is also increased by the millions of microvilli.


Digestive system 3800313

NOTE: This should be a straight line in your notes

Mechanical: Peristalsis

Bile emulsifies lipids

Alcohol absorbed

Chemical: Amylase-CH2O

Lipase-Lipids

Proteases-Proteins

Mechanical: Muscle Contractions

Peristalsis (3 layers)

Small

Intestine

Stomach

Macro & micronutrients absorbed

Mechanical: Peristalsis

Chemical: Pepsin-Proteins

HCl: pH-2

(gastric juices)

Large

Intestine

Esophagus

Tongue

Rectum/

Anus

Mouth/

Throat

Mechanical: Chewing

Chemical: Amylase-Starch

Teeth

Salivary Glands


Are we there yet

Are We There Yet?

  • Almost…

  • While the nutrients are being absorbed by these cells, chyme is being mixed back and forth by segmentation movements within the small intestine.

  • When absorption is complete, undigested material moves into the large intestine.


Large intestine l i

Large Intestine (L. I.)

  • Is about 5 feet long and 3

    inches in diameter in adults

  • Two parts:

    • Colon

      • (for most of its length)

    • Rectum: the final 6”

  • Receives leftovers of digestion: water mixture, undigested fat and proteins, indigestible fibers

http://www.nlm.nih.gov/medlineplus/ency/imagepages/19220.htm


Large intestine l i1

Large Intestine (L. I.)

  • Contains large populations of bacteria that thrive on the unabsorbed nutrients and are also responsible for synthesizing important vitamins for the body (B12, riboflavin, K).

  • Remaining water, salts, and vitamins are reabsorbed by cells in the L. I.


Digestive system 3800313

NOTE: This should be a straight line in your notes

Mechanical: Peristalsis

Bile emulsifies lipids

Mechanical: Muscle Contractions

Peristalsis (3 layers)

Chemical: Amylase-CH2O

Lipase-Lipids

Proteases-Proteins

Small

Intestine

Stomach

Macronutrients absorbed

Mechanical: Peristalsis

Chemical: Pepsin-Proteins

HCl: pH-2

(gastric juices)

Large

Intestine

Esophagus

Tongue

Remaining water, salts and vitamins absorbed

Rectum/

Anus

Mouth/

Throat

Mechanical: Chewing

Chemical: Amylase-Starch

Teeth

Salivary Glands


Large intestine l i2

Large Intestine (L. I.)

  • Leftover material is condensed into semisolid feces which are transported to the rectum by peristaltic movements.

  • Expansion of the rectum stimulates the urge to defecate which is initiated voluntarily after age 2.


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