Digestion, Absorptionand Transport

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ATOMS (IONS)MOLECULES (FUNCTIONAL GROUPS)

MACROMOLECULES (i.e. LARGE COMPLEX MOLECULES)e.g. DNA, RNA, Carbohydrates, Proteins, Lipids

CELLS (e.g. epithelial cells)

TISSUES (e.g. Epithelial tissue, Nerve tissue, Muscle tissue)

ORGANS (e.g. Heart, Lungs, Stomach, Kidney, Liver)

ORGAN SYSTEMS (e.g. Digestive System, Circulatory System, Reproductive System)

BODY (INTERACTING ORGAN SYSTEMS)

Animal Cell Features

• Plasma membrane• Nucleus• Ribosomes• Endoplasmic

reticulum• Golgi body• Vesicles• Mitochondria• Cytoskeleton

Figure 4.10bPage 61

Obstacles in Digestion

• Avoid food and drink going into the lungs• Food must pass through the diaphragm to reach

stomach• The materials in the alimentary canal must be constantly

moving forward at a slow but steady pace• The materials must be lubricated at appropriate levels• The materials must be broken down to right size and

suspended in enough liquid for digestion to occur• The cells in the digestive system are made of same

material as the food. Protect cells from digestion• Excrete waste matter but only when it is convenient

(voluntary)

Catalysis/Digestion Protection

Protection of body against invaders (e.g.

bacteria)

Protection of cells of the digestive system

Digestion

Physical/Mechanical Chemical/Secretions

Regulation and

Signaling

Hormones

Regulation and Signaling

CNS ENS

Enzymes

Regulation of Digestion

1. Extrinsic (from central nervous system)

2. Intrinsic or enteric nervous system aka “gut brain” or “little brain”

-- has as many neurons as spinal cord

3. Neurotransmitters 4. Hormones 1. and 2. are by electrical signals

Digestion• Basic anatomy of the GI tract

– mouth esophagus stomach small intestine large intestine rectum anus

– lumen

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GI Tract Anatomy

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Long (almost 25-foot) tube Indicates plant eating heritage Herbivores have long digestive tracts since plant materials are harder to digest One way passage (Some primitive organisms e.g. starfish have incomplete digestive system and “spit back” non-digested substances)

Sphincter Locations

Modified from http://depts.washington.edu/pbio40

Upper esophageal sphincter

Pyloric sphincter

Sphincter of Oddi

Ileocecal sphincter

Internal and external anal sphincters

Lower esophageal sphincterCardiac sphincter

Sphincter

• (From Wikipedia, the free Encyclopedia)• From late Latin sphincter, from Greek sphinkter,

band, contractile muscle, from sphingein, to bind tight.

• A sphincter is a ring-like muscle that normally maintains constriction of a natural body passage or orifice and that relaxes as required by normal physiological functioning.

History/Trivia

Sphincter of OddiNamed after Ruggero Oddi - Italian anatomist and surgeon He was still a young medical student when he identified the sphincter and in addition characterized its physiological properties in the 1800s.

Also called Glisson's sphincter After Francis Glisson - British physician, anatomist, physiologist, and pathologist, He described liver function and discussed this sphincter in the 1600s

Sphincters of GI Tract

• Consider as traffic control devices

• Total of seven– Upper and lower esophageal sphincters– Pyloric sphincter– Sphincter of Oddi - common bile duct entry

into duodenum– Ileocecal– Internal and external anal sphincters - think

how much you appreciate these!http://depts.washington.edu/pbio40

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Digestion - Mouth

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• Mouth– Tongue– Teeth

• Mastication

Swallowing

Figure 21-13

PharynxEpiglottis Esophagus

Esophageal sphinctersBolus

Muscular Action of Digestion: Stomach Muscles

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Stomach

Chyme

Pyloric sphincter

Digestion• Small intestine

– Duodenum– Jejunum– Ileum

• Liver• Gallbladder• Pancreas

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DUODENUM

JEJUNUM

ILEUM

STOMACH

LIVER

Muscular Action of Digestion: Peristalsis

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Muscular Action of Digestion: Segmentation

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Muscular Action of Digestion

• Sphincter contractions– Reflux

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Digestion• Large

intestine = colon– Ileocecal

valve– Appendix

• Rectum– Anus

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The Final Stage• Stools

• Colon– Fermentation of undigested

residues

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