Download Chapter 16 – Digestive System

Chapter 16 – Digestive System
GENERAL
 In your body the food is converted to nutrients.
 The body needs nutrients in the form of carbohydrates, proteins, fats,
vitamins, minerals, and water for growth, repair of tissues, and energy
– to maintain homeostasis
 The energy in the food is measured in units called Calories.
Depending on your level of physical activity, age, sex, and growth
rate you need a certain number of Calories daily to meet the body’s
energy needs.
 We need to eat more complex carbohydrates (starch) than sugars because
complex ones give you more and long-term energy source as well as other
nutrients. Fiber is a complex carbohydrate of plant origin that is not
broken down in the body but is needed to move the food down the
digestive system more efficiently. Eat a variety of vegetables and fruits to
get all the essential amino acids, vitamins, and minerals. Limit salt. Limit
saturated fats from animal origins since they contain cholesterol and lead
to heart disease.
 The Food Guide Pyramid was developed by nutritionists to help
people eat a healthy diet. It includes 6 food groups (bread, vegetables,
fruits, meat, dairy, and the oil/sweet) and indicates the number of
servings from each group that should be eaten every day.
 Food labels allow you to evaluate a single food as well as compare the
nutritional value of two foods. They list the serving size, fat calories,
ingredients, and Percent Daily Values (how the nutritional content of
one serving fits into the diet of a person who consumes a total of
2,000 Calories/day).
THE DIGESTIVE SYSTEM
 Functions:
- digestion- breaking down of food into molecules the body can
use; this is done in two ways, mechanical (physically breaking
the food through biting, cutting, chewing) and chemical
(breaking down the food by the help of chemicals like enzymes
which are proteins that speed up the chemical reaction)
- absorption of molecules into the blood
- elimination of wastes and undigested material like fiber from
the body
 Mouth
- The teeth (cut, tear), tongue (move the food around and back),
and saliva (moisten the food) take part in mechanical digestion.
- The enzyme Amylase in saliva chemically breaks down
carbohydrates into sugar (a cracker tastes sweet after being in
your mouth for few seconds).
 Esophagus
- A muscular tube connecting your mouth to the stomach
- is lined with a slippery thick substance called mucus that helps
the food be swallowed easier
- moves the food down by peristalsis (involuntary waves of
muscle contractions).
The epiglottis – flap of tissue which seals off the windpipe to prevent
food entering it while swallowing.
 Stomach
- J-shaped muscular pouch for food storage
- Most mechanical digestion happens here by churning motion
(squeezing food and mixing with fluids)
- Chemical digestion is done by the help of the enzyme Pepsin
which breaks down proteins with the help of hydrochloric acid.
The acid also kills bacteria in the food. The acid does not burn
the lining of the stomach since it also contains mucus and the
cells of the lining of the stomach are quickly replaced if
damaged. The food now is a thick liquid.
 Small Intestine (small in diameter)
- Most chemical digestion and absorption happens here with the
help of enzymes and secretions of the small intestine, pancreas,
and liver (the largest and heaviest organ inside the body that
makes bile to break up fats; bile is stored in the gall bladder
before it empties into the small intestine)
- The inner lining of the small intestine is lined with villi that
increase its surface area for easy absorption of nutrients through
the blood vessels.
 Large Intestine (colon)
Has good bacteria (make vitamins) that feed on the material passing
through it, namely water that gets absorbed back into the blood and
undigested food like fiber that will be compressed into solid in the end
part of the large intestine, the rectum and then eliminated through the
anus, the end part of the rectum.
Chapter 17 – Cardiovascular (Circulatory) System
(heart, blood vessels, and blood)
 Carries needed substances like oxygen and glucose to cells
 Carries wastes like carbon dioxide away from cells
 The blood also contains cells to fight disease.
HEART
 muscular organ containing all types of tissues
 pumps blood by pushing it into blood vessels with each beat
 size of a fist
 2 upper, receiving chambers – atria/auricles (A)
2 lower, pumping chambers – ventricles (V)
In between the atria and ventricles and ventricles and arteries, there
are valves which are flaps of tissue to prevent blood from flowing
backwards.
 the heart works in the following way:
- the heart muscle relaxes, atria fill with blood
atria contract, blood goes to ventricles through valve
ventricles contract, valve between aria and ventricles close,
“lub” sound is heard
blood goes to blood vessels; valve between ventricles and blood
vessels snap shut, “dup” sound is heard
this whole process takes less than a second
- the blood moves in 2 loops (the heart is made of 2 pumps); in
one loop the blood goes from RA to RV to lungs to LA; in the
second loop the blood goes from LA to LV to aorta (largest
artery) which branches into arteries to take blood to upper body,
lower body, and heart itself, and then returns to RA again. The
whole process takes less than a minute.
 pacemaker – group of cells in RA that receive messages about the
body’s oxygen needs and send signals to make the heart muscle
contract. This way the heart rate is adjusted. In some people, the
pacemaker gets damaged as a result of accident/disease. This causes
irregular/slow heartbeat. An artificial battery-operated pacemaker
will be inserted in the heart to regulate the beats.
BLOOD VESSELS
 Arteries: carry blood away from the heart; thicker, strong, flexible
 Capillaries: take blood from the arteries and exchange materials
between the blood and cells by diffusion; tiniest
 Veins: carry blood back to the heart after receiving it from the
capillaries
Pulse – caused by alternating expansion (as blood moves in) and
relaxation of the artery wall. The pulse rate determines how fast your
heart is beating.
Blood Pressure – force with which ventricles contract; it is lower as
blood moves away from the heart; highest in the arteries; measured by
sphygmomanometer; normal value for adult is 120/80 (the first number is
obtained when the ventricles contract and send blood to the arteries and
the second number is obtained when the ventricles relax between
heartbeats).
BLOOD
 Plasma: clear, yellow liquid part of the blood; carries materials like
digested food molecules, vitamins & minerals, chemical messengers,
and wastes; 90% water
 45% of the blood are the blood cells which are denser and dark red in
color
- red blood cells are made in the red marrow, are flexible, donutshaped, and thin; its hemoglobin (iron-containing protein) binds
with oxygen to make the blood bright red and able to carry
oxygen
- white blood cells are also made in the red marrow; fight
disease; fewer than the red blood cells but bigger; live for
months; have nuclei
- platelets are cell fragments that help in clotting by releasing
chemicals which produce a protein (fibrin) to trap blood cells
and form a clot. Dried clot on the skin is called a scab.
LYMPHATIC SYSTEM
As blood travels in the capillaries, some leak out into the surrounding
tissues. It carries materials that the cells in the tissues need. Afterwards,
this fluid (now called lymph) moves into the lymphatic system (vein-like
vessels that return the fluid into the blood). The lymph moves slowly
because the lymphatic system does not have a pump.
Lymph nodes – as lymph flows through the lymphatic system, it passes
through small knobs of tissue called lymph nodes which filter the lymph
trapping bacteria and other germs. That’s why they enlarge.
CARDIOVASCULAR HEALTH
Cardiovascular disease is the leading cause of death in US:
 atherosclerosis – artery wall thickens because of fat build up; blood
flow is decreased; leads to heart attack when blood flow to part of the
heart muscle is blocked; heart is damaged
 hypertension – high blood pressure; heart works harder and blood
vessel walls are damaged; “silent killer” because it does not have
symptoms usually
To keep your cardiovascular system healthy:
 exercise regularly
 eat a balanced diet low in fat, cholesterol, and salt
 avoid smoking