Download Intracellular Digestion

ANIMAL
NUTRITION
Diverse Feeding Adaptations
Suspension Feeders – sift food particles from
water.
 Substrate Feeders – eat their way through their
food source.
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– Deposit Feeders – eating their way through partially
decayed matter.
Fluid Feeders – suck fluids out of a living host.
 Bulk Feeders – eat large pieces of their prey.
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Whale Eating a Seal
Four Main Stages of Food
Processing
Ingestion- act of eating.
 Digestion – process of breaking food

down into molecules that can be absorbed
by the body.
 Absorption – absorbing the nutrients into
the blood.
 Elimination – ridding the body of waste.
Digestion Occurs in Specialized
Compartments
Prevents enzymatic hydrolysis of the
organisms own tissues.
 Food vacuoles.
 Gastro vascular cavities.
 Alimentary cavities.
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Intracellular Digestion Verses Extra
Cellular Digestion.
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Intracellular Digestion
– Food vacuoles ingest food particles that fuse to a
lysosome containing hydrolytic enzymes.
– Heterotrophic protists and sponges do this.
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Extracellular Digestion
– Occurs outside of cells.
– Gastrovascular cavities – hydra, planaria
 Incomplete digestion – mouth and anus are the same
opening
 Digestive enzymes secreted by the gastrodermal cells digest
the prey into tiny bits.
Alimentary Cavities.
Digestive tube
 Complete digestive tract – mouth and
anus at opposite ends.
 Nematodes, Annelids, Mollusks,
Arthropods, Echinoderms and Chordates.
 Enzymes are secreted by the digestive
tube and nutrients are absorbed along the
way.
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Specialized Structures of the
Digestive Tube
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Mouth and pharnyx – where food is taken in.
Esophogus - passage
Crop – food moistened and stored (insects and
birds and annelids)
 Gizzard – food is pulverized (birds and annelids)
 Intestine – enzymes digest food and nutrients
absorbed.
 Anus – where undigested food and waste exits.
The Mammalian Digestive System
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Peristalsis is the rhythmic contractions of
smooth muscle along the digestive tract that
keep food moving along.
Sphintors close off various parts of the tube so
that regulating the passage of food between
chambers.
Salivary Glands secrete amylase to break
down starch and lubricate food.
Pancrease secretes digestive enzymes.
Liver produces bile.
Gallbladder stores bile.
The Oral Cavity

Chewing physically breaking the food
into smaller pieces and exposing more
surface area for enzymes to act on.
 Salivary amylase breaks down starch.
Aliva also contains mucin with makes food
slippery.
 Bolus is the ball of food that gets pushed
into the esophogus.
The Stomach
Can accommodate about 2 liters of food.
 Chyme is what the bolus becomes in the
stomach after digestive juices are added.
 Ridges in the stomach called ruggae help churn
food.
 Pepsin breaks down proteins.

– Pepsinogen is the inactive for of pepsin and is
activated by HCl.
– HCl also helps denature proteins in the chyme.
Digestion in the Stomach
A Closer Look

Gastric Pits in the stomach lining are
composed of specialized epithelial cells.
 Gastric pits create the gastric juices.
– Parietal Cells secrete HCl.
– Chief Cells secrete pepsinogen.
– Mucus Cells secrete mucus that protects the
stomach lining.
Feedback Systems
Pepsin activates more pepsinogen.
 The sight of food creates a nervous
response that causes gastric juices to be
secreted.
 A drop in pH and distention of the
stomach creates a negative feedback
response.
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Problems

Gastric ulcers are lesions in the stomach
lining.
 Can occur when the lining is eroded faster that it
is replaced.
 Helibacter pylori can cause ulcers but can be
treated with antibiotics.
 Heartburn occurs when acid chyme seeps back
through the cardiac sphintor which is the
opening between the esophogus and stomach.
Enter the Small Intestine!
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The pyloric sphinctor is the opening between
the small intestine and the stomach.
It takes 2 to 6 hours after a meal for the
stomach to empty.
The small intestine is known as the duodenum.
The small intestine secretes bicarbonate to
neutralize the acid chyme coming from the
stomach.
Bile is secreted by the gallbladder to emulsify
fats which are broken down by an enzyme called
lipase which is secreted by the small intestine.
Enzyme Digestion

Carbohydrates
– Pancreatic amylase secreted by the pancreas breaks
down starch.
– Maltase, Sucrase, Lactase break down disacharrides
and are built into the intestinal epithelium.
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Protein Disgestion
– Chymotrypsin, Trypsin,Carboxypeptidase,
Aminopeptidase, enteropeptidase.
Nucleic Acids – Nucleases
 Lipids - Lipases
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Absorption of Nutrients
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Villi and microvilli increase surface area(300m2) for
maximum absorption.
Intestinal epitheium absorb nutrients either by diffusion
or active transport.
Nutrients are carried away from the intestine by
capillaries at the core of the villi.
Lacteals are lymphatic vessels that are
surrounded by capillaries in the core oif the villie
that absorb fats which are combined with
proteins.
– These lipid proteins are called chylomicrons.
– They travel from through the lyphatic system and
eventually drain back into the blood and travel to the
heart.
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Capillaries and veins drain blood into the
hepatic portal vessel which carries
blood to the liver.
– Ensures that the liver has first access to the
nutrients in the blood.
– The nutrient balance of the blood leaving the
liver may be very different than it was when it
entered.
– One of the many functions the liver include
regulating glucose levels in the blood and
converting amino acids into carbohydrates.
– From the liver the blood travels to the heart
to be pumped to the rest of the body.
Hormonal Regulation of Digestion
Hormones released by the stomach and duodenal
wall ensure that digestive juices are only around
when they are needed.
The sight of food will stimulate the brain to tell the
stomach wall to release gastrin which in turn
stimulates gastric juices to be secreted.
Gastric juices cause more gastric juices to be
released.
A drop in pH inhibits gastrin.
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Enterogastrones are secreted by the
duodenal wall which causes the duodenal
wall to secrete secretin which signals the
pancreas to secrete bicarbonate to
nueteralize chyme as it enters the
duodenum.
 Cholecystokinin(CCK) siganls the
gallbladder to contract and secrete bile into
the duodenum when chyme is rich in fats.
 Other enterogasterones restrict peristalsis
when chyme is rich in fats.
CAT
Reabsorbing Water
Most of the water from waste is absorbed
in the colon.
 The junction between the duodenum and
the colon is called the Cecum.
 Humans have a small ceum compared to
other animals.
 A fingerlike projection that extends from
the cecum is called the appendix.
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Colon Bacteria
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Flora are bacteria that live within the
body that are beneficical.
 E.Coli live in the colon and produce
vitamins, K B, biotin and folic acid.
 Generate gases such as methane and
hydrogen sulfide as by products of
microbial metabolism.
Structual Adaptations of the
Digestive System

The type of teeth and the way that they are
arranged accommodate an animals’s diet.
– Herbivores like horses have flat molars fro grinding.
– Carnivores have pointed incissors for tearing and
catching prey.
– Carnivores have large expandable stomachs to allow
them to eat large a mounts of food at once because
there may be long periods of time where they go
without food.
– Snakes have hollow teeth to store venom.
– Snakes have a flexible ligament that allows them to
open their jaw to swallow prey whole.
Length of Digestive Tract
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Herbivores and Ominvores have a relatively long
alimentary cavity relative to their digestive tract
because they ingest cellulose.
– Hard to digest and low in energy content.
– Many herbivores have symbiotic bacteria living in
specialized organs that digest cellulose
 Ruminants
 Crop in the Hoatzin(South American Bird from the Rain
Forest) have bacteria that digest cellulose.
– Rabbits eat their feces and digest it again.
– Cows regurgitate and chew their food over again.
Large Intestine
Termite Triconym and Symbiont