Download Chapter 21

Chapter 21
Digestion
Most animals ingest their food usually through ----------- or --------------- for digestion.
___________: animals that eat both plants and animals
Herbivores:
______________: animals that only eat other animals.
There are several different mechanisms for ingestion of food:
- Suspension feeders:
Ex: hump back
whales
- ____________: live in or on food source. Ex: caterpillars
- _________________: suck food from a living host Ex: ticks
- Bulk feeders: most animals use this method where they ingest large pieces of
food.
There are four stages in processing food.
1. Ingestion: __________________
2. _______________: changing the food into a form that can be absorbed by the
animal. Transforming macromolecules (proteins, fats, carbohydrates) into
monomers that can be used as building blocks for the animals. Digestion goes
through mechanical and chemical breakdown.
3. Absorption: nutrients are absorbed by the _________or ____________and are
distributed in the body for nutrition and energy.
4. Elimination: __________________ exists the body as feces.
DIGESTION:
-
-
Occurs in ------------------------ that allow digestive enzymes to act on the food.
Some unicellular organisms digest food inside special cells; other larger animals will
have ______________________________ outside cells for digestion to occur.
Some simple animals have a ______________________________ with only one
opening, a mouth.
A second type of digestive compartment is an___________________, which is a tube
with two openings, a mouth and an anus. Food can pass into regions such as the
______________and the esophagus. From there the food can go into -----------------------------------------------------------------------------------------------------------------------A crop is like a pouch in which food is -----------------------------------------------------Stomachs and gizzards are similar but they -------------------------------------------------Most of the food absorption occurs in the_______________, and the
______________removes the undigested material.
Alimentary tracts of animals differ according to their diets.
Human Digestive System:
1. Consists of an alimentary canal and digestive glands.________, oral cavity,
tongue, __________, esophagus, -----------, small intestine, large intestine, -------and anus.
2. Digestive glands include -----------------------------------------------------------------3. Food is swallowed and goes to the alimentary tract by ------------------4. In a few seconds, food passes from the -------------------- to the ----------------------- and then the -----------------------------. The -------------------------------------allows the passage of the food from the stomach to the small intestine. Most of the
digestion occurs in the stomach and small intestine.
5. Undigested food goes to the ------------------------------------- where water is
absorbed and the rest exists as feces from the anus.
Oral Cavity:
- -------------- is produced and lubricates the food.
- -----------------------------contains many proteins, buffers, and enzymes such as ----------------------- that help in digestion of starch.
- Mechanical and chemical digestion begins in --------------------------------. Chewing
and cutting the food makes it easier to swallow and digest.
- ------------------------------ is a muscle that contains taste buds. Allows the food to be
changed into a ball called a ----------------------------- for easier swallowing into the
pharynx.
Food Passage:
- pharynx opens into ---------------------- and the -------------------------------------- most of the time the esophagus opening is closed by an ----------------------------------------- and the trachea is open for breathing.
- When food is swallowed, the sphincter relaxes and the bolus -----------------------------------. At the same time the larynx moves the ------------------to block the tracheal
opening.
- ---------------- pushes the food to the stomach. It is lined by two kinds of ---------------circular and longitudinal.
Stomach:
- it is very elastic and can accommodate up to 2 liters of food.
- Has many ----------------------- and secretes gastric juice made of-------------------------,
enzymes, and ---------------------------- There are 3 types of gastric glands, mucous cells secrete mucus, ------------------------secrete HCl acid, and ----------------------------------- secrete pepsinogen.
- HCl converts pepsinogen to pepsin, and the digestion of proteins begins.
- --------------------------- from the brain and hormones work on secreting gastric juice. ----------------------------a hormone is turned on or off depending on the need for
digestion.
- Food along with gastric juices is called--------------------------. The acid chyme enters
the small intestine gradually through the-----------------------------. It takes 2 – 6 hrs to
empty the stomach.
Small Intestine:
- Most ------------------------ occurs in the small intestine. Starch digestion starts in the -------------------------- and protein digestion starts -------------------------------------. All
other macromolecules and soft drinks occur here.
- It s about 6m long. The -------------- and ---------- aid the small intestine in digestion.
Pancreas secretes digestive enzymes, and the liver secretes bile, which has no
enzymes, but it mixes with -------- for easier digestion. Bile is stored in the -----------until it is needed.
- In the------------------, the first 25 cm o f the small intestine, the mixing of enzymes,
bile and acid chyme occurs.
- Many enzymes are involved in the breakdown of carbohydrates, proteins, lipids, and
nucleic acids.
- The rest of the small intestine is involved in the --------------of nutrients from the
digested food.
- The small intestine is made of many ------------------------ that have small projections
called --------------------------These villi absorb the nutrients into blood capillaries that
drain into a vessel, which takes them to the liver.
Large Intestine:
- colon is about -------------------------- It is joined to the small intestine at a junction called the-----------------------. Attached
to the cecum is the------------------------- , which contains WBC.
- The main function of the colon is to absorb--------------.
- The remaining undigested particles form feces, which go to the --------------------------------------(end part of the colon) and are excreted by the anus.
-
-
Herbivores and -------------------------------have longer alimentary tracts than
carnivores to their size. This is needed to digest---------------------, which has a cell
wall made of --------------------------- and takes longer to break down.
Many herbivores have bacteria and enzymes that can digest cellulose.
----------------------- such as cows, sheep contain chambers that help in digestion of
cellulose. Rumen, reticulum, omasum, abomsum.
NUTRITION:
- a healthy diet is needed for energy, raw materials to make macromolecules, and to
obtain nutrients that cannot be made by the animal.
- Chemical energy ----------------, is needed for all activities. It is gained by cellular
respiration and the breakdown of-------------, lipids, -------------, and nucleic acids.
- Calories that are not burned by activity, are stored by the body in the form of--------------- or -----------------.
- Fat is needed for insulation, -------------------, and certain vitamins.
- Excess fat(more than 20% of needed amount) can increase the chance of diseases.
- ----------------------- is metabolized easier than fats. Increased fat consumption allows
these molecules to be stored in our cells and is v. difficult to burn.
-
-
A healthy diet must include several vitamins. Vitamins are nutrients that are required
in small quantities by the body.
Most vitamins function as ---------------- and in metabolic activity.
There are ---------------- vitamins needed by the body. These can be acquired from a
variety of foods.
Vegetarians have to make sure that they obtain the appropriate nutrition from their
diets. There are -------------------- acids that we get from meat and eggs. Vegetarians
have to get them from different plants and beans.
Minerals are chemical nutrients that are essential in nutrition. Ex: Ca, K, Na, S, P, Fe,
Mg, Zn.