layers of the earth

1. Digestive System

2. Food and Energy
• Energy available in food is measured by
burning food
• calorie = amount of heat needed to raise
the temperature of 1 gram of water by 1
degree Celsius
• Dietary calories are referred to as C
C = 1000 calories or 1 kilocalorie

3. Calories
• Average teen needs
2200 Calories/day for females
2800 Calories/day for males

4. Nutrients
1. Water
2. Carbohydrates
3. Fats
4. Proteins
5. Vitamins
6. Minerals

5. Water
• Water is most important nutrient
• Every cell in the human body needs
water
– Many body processes and chemical
reactions take place in water
• Makes up bulk of blood, lymph and
other bodily fluids
• Drink at least 1-2 liters of water each
day (6-8 cups)
– Not enough = dehydration  causes
problems in circulatory, respiratory, and
nervous systems

6. Caloric Nutrients
• Carbohydrates: Nutrients that are the main
source of energy for the body
• Protein: Nutrients that are the main source of
building blocks for the body
• Fats/Lipids: Used for cellular components, such
as cell membranes, also used for storage of
energy.

7. Fats/Lipids
Saturated or Unsaturated?
solids at room temp = saturated
(butter and animal fat)
liquids at room temp = unsaturated
(vegetable oils)
-Saturated fats are the “bad” fats, and
unsaturated are the “good” fats

8. Proteins
• 8 amino acids the body cannot make are
called “essential amino acids”
– Must be obtained from food that you eat
• meat, fish, eggs and milk, legumes
• Trytophan, Lysine, Methionine, Valine,
Leucine, Isoleucine, Threonine, and Phenylalanine

9. Vitamins
• Organic molecules
that help regulate
body processes (work
with enzymes)
• Most vitamins
obtained from food
– Bacteria in
digestive tract
synthesize vitamin
K
– Skin synthesizes
vitamin D when
exposed to sunlight

10. Vitamins
• 2 types of vitamins:
1. fat-soluble
A,D,E and K can be stored in fatty
tissues of body
-excessive amounts can be toxic
2. water-soluble
C and B vitamins dissolve in water
and can’t be stored

11. Minerals
• Inorganic nutrients that the body needs in
small amounts, also called micronutrients
ex: calcium  major component of bones and
teeth
iron  makes hemoglobin
magnesium, sodium and potassium

12. Process of Digestion

13. Digestive System
• Includes:
– Mouth
– Pharynx
– Esophagus
– Stomach
– Small intestine
– Large intestine
– Accessory structures: salivary glands,
pancreas, liver add secretions

14. Function
• Function of the digestive system is to help
convert large food molecules into
simpler molecules (monomers) that can
be absorbed and used by the cells of the
body

15. Mouth
• Teeth
– Mechanical work of digestion by cutting, tearing, and
crushing
– 1st step in digestion and increases surface area of food
• Saliva – salivary glands
– Helps to moisten food and make it easier to chew
– Begins chemical digestion  enzyme amylase breaks
down bonds in starches and releases sugars
– Also contains lysozyme  enzyme that fights infection by
breaking down cell walls of many bacteria

16. Esophagus
• Long tube of smooth
muscle that connects
the pharynx with the
stomach
• Chewed clump of food
= bolus
• Tongue and muscles
push bolus down
throat
• Epiglottis closes over
trachea to keep food
out

17. Esophagus
• Esophagus carries food to
stomach
• Contractions of smooth muscles
(peristalsis)
– Peristalsis-Squeeze food thru
esophagus into stomach
– Reverse peristalsis = vomiting
– Cardiac sphincter (thick ring of
muscle) closes and prevents
stomach contents from moving
back up esophagus

18. Stomach
• Large sac of smooth muscle
• Chemical digestion
– Gastric glands secrete substances
– Mucus lubricates and protects stomach wall
– Hydrochloric acid/pepsin (breaks down proteins)
• Mechanical digestion (smooth muscle
contractions)
– Mixture called chyme
– After an hour or two, pyloric valve opens and
chyme begins to flow into small intestine

19. Small Intestine
• Enters the duodenum (first of 3 parts of
small intestine)
– Almost all of digestive enzymes enter the
intestine
– Most of chemical digestion and absorption of
nutrients occurs in the small intestine
– Mixes with fluids and enzymes from pancreas
and liver

20. Small Intestine
• Pancreas:
1. Produces hormones that regulate blood
sugar levels
2. Produces enzymes that break down carbs,
proteins, lipids and nucleic acids
3. Produces sodium bicarbonate (base which
neutralizes stomach acid) so enzymes can
be effective

22. Liver
• Liver:
– Located above and to the right of the stomach
– Produces bile (fluid loaded with lipids and
salts)
– Bile acts as a detergent, dissolving droplets
of fats from food
– Bile is stored in gallbladder

24. Small Intestine
• Duodenum-First part of
the small intestine where
chemical digestion begins
to take place
• Jejunum and ileum are
remaining parts of small
intestine (average about
6 meters long)
• Villi are fingerlike
projections covering
surface of small intestine
– Absorption of nutrients
occurs here

25. Small Intestine Large Intestine
• By time it leaves
small intestine, food is
basically nutrient-free
water, cellulose and
other undigestible
substances
• Appendix: in humans
does little to promote
digestion, but in other
mammals it stores
cellulose and other
materials

26. Large Intestine
• Also known as the colon
• Primary function is to remove water from
the undigested material
• Water is quickly absorbed across the wall
of the large intestine
• Concentrated waste material that remains
passes through the rectum and is
eliminated from the body

28. Digestive System Disorders
• Peptic ulcer  powerful acids in stomach
damage stomach wall
– Doctors thought that ulcers were caused by
too much acid, but scientists have discovered
bacteria Helicobacter pylori is cause (now
cure rates are as high as 90%)

30. Digestive System Disorders
• Diarrhea  not enough water is absorbed
• Constipation  too much water is
absorbed
– Eat plenty of fiber and drink plenty of water!

31. Excretory System Function
• Function of the excretory system is to
maintain homeostasis in the body by
eliminating metabolic (cellular) wastes

32. Organs of Excretion
• skin  excretes water and salts, small
amount of urea (sweat)
• lungs  excretes carbon dioxide
• liver  converts nitrogenous wastes
from digestion into urea
• kidneys  excretes urea and other
metabolic wastes

33. Kidneys
• The kidneys are bean-shaped organs, each
about the size of a fist.
• They are located near the middle of the back,
just below the rib cage, one on each side of
the spine.
• Kidneys play important role in maintaining
homeostasis
-remove waste products from the blood
-maintain blood pH
-regulate the water content of the blood
(regulating blood volume)

35. How Do the Kidneys Work?
• Remove excess water from the blood
• Remove urea from the blood
– Urea is a form of ammonia, which is produced
by your cells during cellular metabolism

36. Kidney Structure
• Each kidney is made of
many smaller units
called nephrons
• Nephron
– Each nephron has its own
blood supply (arteriole,
venule, and capillaries)
– Each nephron releases
fluids to collecting duct
which leads to ureter

37. Parts of the Excretory System
• ureter- tube that carries
urine from the kidneys to
the urinary bladder
• urethra- tube that carries
urine from the bladder
and releases it from the
body
• urinary bladder- saclike
organ which stores urine
before it is excreted

38. Urine Formation
• In each nephron, urea
and water are filtered
out of the blood, and
some water is
reabsorbed.
• The remaining
material is conducted
to the urinary bladder
through the ureters,
where it becomes
urine.

39. Disorders of the Excretory
System
• Kidney failure- Can be caused by a number of
things; treatment is dialysis
– Dialysis is when the urine collection is done by a
machine, rather than by a kidney
• Kidney Stones- made of solidified calcium,
magnesium or salts
– cause is unknown, but drinking too few liquids could
be a cause.
– Can back up the urine flow in the kidney
– VERY painful