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Digestion and Nutrition - 2013 Overall Goal of Digestive Systems A. Obtain organic molecules from environment B. Reduce complex molecules such as proteins, polysaccharides, nucleic acids and lipids to absorbable sizes and

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slide1

Digestion and Nutrition - 2013

Overall Goal of Digestive Systems

A. Obtain organic molecules from environment

B. Reduce complex molecules such as proteins, polysaccharides, nucleic acids

and lipids to absorbable sizes and

C. Transport the molecules into the blood stream so that they may be assimilated into

cells.

General Strategies for obtaining nutrients

A. Filter feeders - microorganisms, marine and freshwater crustaceans,

baleen whales. (show whale video)

http://videos.howstuffworks.com/discovery/428-corwins-quest-whales-video.htm

http://videos.howstuffworks.com/discovery/28113-assignment-discovery-baleen-whales-plates-video.htm

slide2

B. Carnivores

C. Herbivores

1. the problem with cellulose - requires bacteria or protozoa that produce cellulase

2. pregastric fermentation

3. postgastric fermentation

D. Omnivores

E. Symbiotic nutrition

chloroplasts from algae in the bodies of sea slugs - photo synthetic products feed slugs

http://www.newscientist.com/article/dn16124-solarpowered-sea-slug-harnesses-stolen-plant-genes-.html

bacteria in digestive tracks of ruminants (cows)

http://www.teachersdomain.org/resource/nat08.living.str.living.digest

perspectives on digestion
Perspectives on Digestion
  • Overview
    • Mechanical - mastication, stomach, crop, and intestinal motility
    • Chemical (secretions) - enzymes from saliva, pancreas and intestines
    • Absorption - intestinal lumen o blood
    • Assimilation - blood into cells throughout the body.
  • Motility
    • Smooth muscle
    • Pace setter potential - specialized cells in digestive tract produce electric impulses(potentials) that stimulate the gut to contract
    • Enteric (intrinsic) nervous control (responds to stretch, pH, hormones)
    • Extrinsic = controlled by central nervous system (brain & spinal cord)
slide4

Intrinsic Nerves of the

Rat’s Stomach

Fig. 14-5, p.619

slide5

Ingestion

Mouth

Receiving

Pharynx

Foregut

Conducting

Storage

Digestion

Crop

Motility

Digestion (acidic)

Midgut (stomach)

Secretions

Absorption

Assimilation

Digestion (basic)

Hindgut

Storage of waste

Defecation

Fig. 14-1, p.613

slide6

The enzyme “cellulase” is required to hydrolyze cellulose. This enzyme is only produced by microorganisms. Animals must provide organs that support the growth of these symbionts.

Starch is hydrolyzed to maltose by the enzyme “amylase” which is produced by the salivary glands and the pancreas.

slide7

Hydrolysis of a disaccharide (maltose) to two monosaccharides (glucose)

Maltase is the enzyme that performs this action. It is produced primarily by the cells that line the intestinal lumen.

categories of digestive enzymes
Categories of Digestive Enzymes

Amylase: starch hydrolysis to maltose

Protease: proteins hydrolyzed to peptides

Lipase: triglycerides hydrolyzed to fatty acids and glycerol

Nucleotidases nucleic acids hydrolyzed to nucleotides

slide9

Gastrointestinal Tract

(alimentary canal)

mouth-anus

Accessory Organs

Liver

Gall Bladder

Pancreas

slide10

Nasal

passages

Hard palate

Soft palate

Uvula

Pharynx

Epiglottis

Esophagus

Bolus

Trachea

Tongue

Glottis at entrance of larynx

(a)

Fig. 14-7a, p.624

slide12

Esophagus

Fundus

Smooth

muscle

Gastroesophageal

sphincter

Body

Stomach

folds

Pyloric

sphincter

Oxyntic

mucosa

Pyloric

gland

area

Antrum

Duodenum

Fig. 14-8, p.627

slide13

Gastric

pit

Mucosa

Submucosa

Table 14-3b, p.632

slide14

In oxyntic mucosa

Surface epithelial cells

Gastric

pit

Mucous cells

Produce pepsinogen

Chief cells

Produce HCl and

Intrinsic Factor

Gastric

gland

Parietal cells

Enterochromaffin-

Like (ECL) cells

Table 14-3c, p.632

slide15

Peptic Ulcers

    • Heliobacter pylori - bacterial infection responsible for 90%
    • of all peptic ulcers
    • Treatment with antibiotics
slide18

HCl, fats, osmo

CCK

Secretin

slide19

Intestinal Cross Section

Layers of the alimentary canal

Serosa

Smooth muscle

cells

Muscularis

Submucosa

Mucosa

Microvilli

Villus (Villi)

Mucosal cells

slide21

Negatively charged H2O-soluble portion (a carboxyl group at the end of a glycine

or taurine chain)

Small lipid (fat) droplet with bile salt molecules

adsorbed on its surface

Lipid-soluble portion

(derived from cholesterol)

Large fat droplet

Through action of bile salts

Lipid emulsion

Fig. 14-17, p.644

slide22

Lipid Absorption

Fig. 14-24a, p.654

block diagram of lipid absorption
Block Diagram of Lipid Absorption

Lipids in Duodenum

HDL’s and LDL’s re-enter blood and are distributed to other cells throughout the body.

Liver takes up Chylomicra and converts them to HDL’s and LDL’s

Lipids combine with Bile and form Micelles

Lipase begins to convert triglycerides to fatty acids

Chylomicra move through lymphatic system and enter the blood at subclavian veins.

Micelles taken up by mucosal cells

Mucosal cells add proteins and extract fatty acids

Lipids enter lymph capillaries as

Chylomi ra

slide27

Transverse colon

Haustra

Taeniae coli

Descending colon

Ascending colon

Ileocecal valve

Appendix

Sigmoid colon

Cecum

Rectum

External anal sphincter

(skeletal muscle)

Internal anal sphincter

(smooth muscle)

Anal canal

Fig. 14-26, p.657

slide28

Rumen

Reticulum

Omasum

Abomasum

To small

intestine

(b)

Fig. 14-27b, p.661