Transcript Nutrition - TeacherWeb

Nutrition
The Digestive System
Nutrition in Protozoa
• Intracellular digestion
• Amoebae use pseudopods to engulf food
through phagocytosis.
• Lysosomes contain digestive enzymes to
break down macromolecules into building
blocks
• In paramecium, cilia sweep microscopic
food into the oral groove – solid wastes are
expelled at the anal pore
Nutrition in Cnidirians
• Hydra employ both intracellular and
extracellular digestion. Tenticles bring food
to the mouth, and bring the food into a
gastrovascular cavity. Once the particles
are broken down small enough
they are taken into
the cells to be
completely digested.
Undigested material
released through the
mouth
Nutrition in Annelida
• They have a complete one way, two
opening digestive tract.
• In order – mouth, pharynx, esophagus,
crop (to store food), gizzard (to grind
food), Intestings (digestion and aborption),
and anus (undigested food released)
Nutrition in Arthropod
• Similar to annelids except that they have
jaws for chewing and salivary glands for
better digestion.
Human Digestive System
• Consists of the alimentary canal and the
associated glands.
• The pathway of the food through the body
is: The oral cavity, pharynx, esophagus,
stomach, small intestine, large intesting,
and rectum. The accessory organs
consist of of the Liver and pancreas which
deliver secretions into the canal via ducts.
Types of digestion
• Mechanical digestion
– Food is crushed and liquified by the teeth,
toungue, and peristaltic contractions of the
stomach and small intestines
– This increases the surface area for the
digestive enzymes to work on
– Peristalsis is wavelike muscular action
conducted by smooth muscle that lines the
digestive system
Chemical Digestion
• Exocrine glands associated with the digestive
system produce secretions involved in breaking
moleucules into simple molecules that can be
absorbed
• REVIEW BUILDING BLOCKS OF ORGANIC
FAMILIES
• Chemical digestion of carbohydrates begins in
the mouth. Amylase breaks down
polysaccharides before food is swallowed
Chemical Digestion
• In the stomach, gastric glands produce
hydrochloric acid and the enzyme pepsin
(breaks down protein).
• Chyme (partially digested food in the
stomach) enters the duodenum through
the pyloric sphincter.
• The liver produces bile (used for fat
digestions) bile is stored in the gall bladder
before being released in the small
intestines.
Chemical Digestion
• The liver also helps regulate blood glucose
(excess glucose stored here as glycogen
so that in times of need can be released to
raise sugar levels) levels and produces
urea by breaking down red blood cells.
• The Pancreas releases pancreatic lipase
and makes amylase, trypsin, and
chymotrypsin (protein digestion)
Absorption
• All digestion is completed in the small intestines
• Small intestines are lined with villi (folds) to
increase surface area for more absorption of
nutrients
– Villi contain cappillaries and lacteals (projections of
the lymphatic system) and microvilli (little hairs)
– Nutrients move into blood stream through digestion
• The large intestines are for water and vitamin K
absorption.
Villi