Transcript The Digestive System - Anoka-Hennepin School District 11

Hungry???
Homeostasis
&
The Digestive System
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Nutritional requirements
Animals are heterotrophs
need to take in food
Why? fulfills 3 needs…
fuel = chemical energy for production of ATP
raw materials = carbon sources for biosynthesis
essential nutrients = substances animals cannot make
themselves
• elements (N, P, K, Fe, Na, K, Ca, etc.), NAD, FAD, etc.
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Energy budget
food
intake
ATP
production
biosynthesis
storage
{
{
{
• basal (resting)
metabolism
• activity
• temperature
regulation
• growth
• reproduction
• glycogen
• fat
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 A body functions properly only when the needs
of the organisms (water, food, heat, oxygen
and pressure) remain within the narrowly
required limits.
 Homeostasis: The tendency to maintain a
stable internal environment.
Ex: Furnace and air conditioner unit to maintain
constant temperature
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 Negative feedback mechanism:
Negative feedback occurs when an increase in some
factor is sensed and is lowered
A response the body has to an occurrence that
disturbs the homeostasis of the body. As the body
reacts to that occurrence and moves closer to
homeostasis, the receptors are shut down, thus
causing fewer effectors to produce a product that’s
needed to bring the body back to homeostasis, in the
end having a “negative” effect on the production. The
purpose of this is to stop overproduction or
overreaction.
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 Homeostatic mechanism in regulating body
temperature:
 Shivering – in a cold environment muscles will
contract involuntarily producing heat
 Sweating - in an overheated environment the
brain triggers a changes that promotes the
increased loss of body heat
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Managing glucose levels
 Human body regulates the use & storage of
glucose, a major cellular fuel
insulin reduces blood glucose levels
 when glucose levels rise above set point,
pancreas secretes insulin
 promotes transport of glucose into cells &
storage of glucose as glycogen in liver & muscle cells
 dropping blood glucose levels
glucagon increases blood glucose levels
 when glucose levels drop below set point,
pancreas secretes glucagon
 promotes breakdown of glycogen &
release of glucose into the blood
 increasing blood glucose levels Show PDF of insulin
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• Regulation: Maintaining Homeostasis
 Balancing glucose levels in blood
depress
appetite
pancreas
insulin
glucose
uptake
glucose
storage
glucose
release
glucagon
pancreas
stimulate
hunger
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Essential Nutrients
What happens if an animal’s diet is
missing an essential nutrient?
deficiency diseases
scurvy — vitamin C (collagen production)
rickets — vitamin D (calcium absorption)
blindness — vitamin A (retinol production)
anemia — vitamin B12 (coenzyme function)
kwashiorkor — protein deficiency
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Digestion
The reduction of large food molecules into
smaller absorbable units and conversion
of insoluble units into soluble ones.
This is accomplished by mechanical
action, chemical and enzymatic action.
Enzymes are synthesized by cells in the
mouth, stomach, pancreas and small
intestine
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Normally 9295% of a diet is
digested and
absorbed, but
the process
varied for each
nutrient
http://www.amaassn.org/ama/pub/category/7155.ht
ml
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Types of digestive action
Mechanical
Movement of the teeth grinding the food in the
mouth
Chemical
Changing the food molecules into new and
different molecules
Lipase
Lipids
Fatty acids + glycerol
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Alimentary Tract
Alimentary canal
A muscular tube about 9 meters long
Appendage organs include:
Liver, biliary tree and pancreas
Extends from the mouth to the anus
Receives food . . . Digestion/absorption
occurs . . .transport to cells . . .excretion of
waste
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Diagram of Alimentary canal
 Peristalsis – propelling
movements which are a
forward motion that is wavelike
 Peristalsis pushes tubular
contents ahead of it through
the alimentary canal
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Mouth
Teeth mechanically grind and crush food
Saliva moistens and binds food mass
Salivary amylase begins digestion of
starch
Chewed food mass
bolus
Passes from mouth into esophagus
Movement is controlled by peristalsis
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 Approximately 1.5 liters of saliva are produced
daily by salivary glands (~ 6 cups) Figure 12.1
 Amylase is a digestive enzyme
It splits starch and glycogen (both carbohydrates) into
disaccharides via hydrolysis
 Mucus binds food particles and acts as a
lubricant in swallowing
 Esophagus – straight tube that provides a
passageway between the pharynx and
stomach
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Stomach
Chemical digestion begins in the middle of
the stomach mixing food with gastric juices
Gastric juices contain HCl, intrinsic factor,
pepsinogen, gastric lipase & mucus
Food becomes semi-liquid chyme (50% water)
Stomach is emptied in 1 – 4 hours
Sphincter–valves at either end of stomach
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 The lining of the
stomach is covered
with numerous small
holes. These are the
openings of gastric
pits which extend into
the mucosa forming
gastric glands.
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Stomach helps to initiate the digestion of
proteins, but also helps speed up the
digestion of carbohydrates and fats
Pepsin is the most important digestive enzyme
in the stomach
Pepsin is a protein-splitting enzyme
It carries on a limited amount of absorption
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 The pyloric sphincter
(pylorus) is a muscle that
acts as a valve to
prevent regurgitation of
food from intestines back
into the stomach
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Rugae: thick folds in
stomach wall
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Pancreas
Functions as an endocrine gland
Releases hormones
Functions as an exocrine gland
Secretes digestive juices
Pancreatic juices move into the intestine
(duodenum)
Contains enzymes that digest
carbohydrates, fats, proteins and nucleic
acids
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 Viewing the digestive system
in the anatomical position, the
pancreas is found in under the
stomach in the left
hypochondriac & epigastric
regions
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Liver
 Located below the
diaphragm in the right
hypochondriac and
epigastric regions of
the abdominal area.
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The liver metabolizes carbohydrates lipids
and proteins
Stores glycogen, vitamins A, D, B12 and
iron
Filters blood
Detoxifies blood
Secretes bile
An Introduction to the Liver – PDF File
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Other functions of the liver
 Producing quick energy when it is needed;
 Manufacturing new body proteins;
 Preventing shortages in body fuel by storing certain vitamins, minerals, and
sugars;
 Regulating transport of fat stores;
 Regulating blood clotting;
 Aiding in the digestive process by producing bile;
 Controlling the production and excretion of cholesterol;
 Neutralizing and destroying poisonous substances;
 Metabolizing alcohol;
 Monitoring and maintaining the proper level of many chemicals and drugs in
the blood;
 Cleansing the blood and discharging waste products into the bile;
 Maintaining hormone balance;
 Serving as the main organ of blood formation before birth;
 Helping the body resist infection by producing immune factors and by
removing bacteria from the bloodstream;
 Regenerating its own damaged tissue; and
 Storing iron.
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Bile Yellowish, green liquid made of bile salts, bile
pigments, water, cholesterol and electrolytes
Bile salts aid the digestive enzymes and
enhance the absorption of fatty acids and
fat-soluble vitamins
Bile salts act as emulsifiers, breaking up
fat into droplets, allowing lipases to digest
state source of one lipase – substate,
them better 5.1.3
source and optimum pH
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Bile is stored in
the gall bladder
until a hormone
stimulates its
release into the
small intestines
http://www.foxriverwatch.c
om/liver_hepatic_damage
_pcbs_1a.html
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Small Intestine
 Approx. 20 -25 feet long with villi and microvilli
for a total surface area of 25 sq meters
 3 areas:
Duodenum
Jejunum
Ileum
 Most digestion occurs in the duodenum
 Most absorption occurs in the jejunum and ileum
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 The intestines are lined with villi
Increase the surface area of the intestinal lining
Increase the absorption of digestive products
Capillaries carry away absorbed products from villi
 Nutrients are absorbed by several means
Simple diffusion (higher to lower concentration area)
Facilitated diffusion (Against the gradient using channel or
carrier proteins)
Active transport (diffusion with ATP)
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 Microvilli on intestinal epithelial cells
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As chyme enters duodenum it stimulates
the release of pancreatic juices and mixes
with enzymes from the pancreas and small
intestine as well as with bile, fluid and
bicarbonates
All the gastric, small intestinal secretions
and pancreatic secretions are controlled
by the nervous system and by hormones
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Digestive enzymes in sm. intestine
Enzymes are specific to a particular
substrate
Proteins
Peptidases break peptides into amino acids
Lipids
Lipases break lipids into glycerol and fatty acids
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Carbohydrate Digestion
Begins in mouth with salivary amylase
Halted by hydrochloric acid
Digestion mostly occurs in small intestine
by pancreatic amylase
Passes through intestinal wall in
monosaccharide form (ex: glucose)
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They quickly move through the digestive
system
Some carbohydrates cannot be digested
by humans and are excreted
They provide short term energy
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Protein Digestion
Begins in stomach by proteolytic enzymes
Most of digestion takes place in the
duodenum by pancreatic and intestinal
enzymes: Protein hydrolysis
Final phase occurs in the “brush border” of
the microvilli
Absorbed in the amino acid form
Allergic reactions can occur when intact
proteins pass through intestinal wall
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Proteins move through digestive system
2nd fastest after carbohydrates
Once protein is broken down into amino
acids, these are reassembled into 1º,2º,3º
and 4º proteins the body needs:
Hemoglobin – blood protein
Albumin – in plasma; aids in blood clotting
Fibrinogen – blood clotting agent
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Lipid Digestion
Begins in stomach with gastric lipase
Major digestion occurs in small intestine
Bile and action of stomach/small intestine
break down large globules into smaller
pieces
Lipase breaks down particles into fatty
acids.
Cholesterol and fat soluble vitamins follow
similar process
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 Lipids move slowly
through the digestive
system
 They are stored as
long term storage in
the form of adipose
tissue
http://www.sunyniagara.cc.ny.us/val/adipos
e2.html
http://www.gen.umn.edu/courses/113
5/lab/kidneylab/kidneylab.html
Vitamins, Minerals and Fluids
Absorbed in the intestine
Eight liters of fluid are passed back and
forth across the membrane of small
intestine to keep nutrients in solution
Vitamins and water pass unchanged from
small intestinal wall into the blood stream
Absorption of mineral occurs in stages in
small intestine
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Large Intestine
Includes:
Ascending colon
transverse colon
descending colon
sigmoid colon
rectum
http://www.fruit-eze.com/education/colon/
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 Large intestine primarily absorbs water, electrolytes
and some vitamins
 Bacteria break down undigested material
 Formation and absorption of vitamin K
 Formation and excretion of waste products
http://www.fujinon.com/
product/medical/ed011
4.htm
Little digestion now occurs as it is mostly
completed by this time.
Large intestine are about 5 feet long
Mixing movement and peristalsis occur but
are much slower here.
Peristalsis occurs only 2 to 3 times/day.
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Contain E. Coli (good form not 0157) that
break down remaining food and aid in the
formation of vitamin K
Newborns and vitamin K
The solid waste consists of dead bacteria,
undigested fiber and other products of
digestion.
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