Unit 3.2
Food
1. What are the functions of the digestive system?
• Takes in food & water
- ingestion
• Mechanical
processing
• Digestion
• Secretion
• Absorption
• Excretion
2. How does the structure of each organ in the digestive system relate to
its function? 3. How does the digestive system assist in maintaining the
water balance in the body?
• Oral Cavity, teeth, tongue
• Mechanical processing, moistening, mixing with salivary
secretions
• Tongue assists with swallowing of bolus = mass of chewed or
partially digested food
• Hard palate & soft palate
• Form roof of the oral cavity
• With the uvula, the soft palate keeps food from going into nasal
cavity during swallowing
• Salivary Glands
• Exocrine glands that secrete lubricating fluid containing enzymes
that break down carbohydrates.
• Salivary amylase starts carbohydrate digestion
2. How does the structure of each organ in the digestive system relate to
its function? 3. How does the digestive system assist in maintaining the
water balance in the body? Cont.
• Pharynx
• A hollow tube shared by both the digestive &
respiratory system—allows the passage of food,
water & air.
• Epiglottis
• Elastic cartilage in the laryngophaprynx that
closes during swallowing to prevent food from
traveling into the trachea
2. How does the structure of each organ in the digestive system relate to
its function? 3. How does the digestive system assist in maintaining the
water balance in the body? Cont.
• Esophagus
• Hollow tube
• Pushes food & water to the stomach using
peristalsis = muscle contractions
• No enzymes are secreted into the esophagus
2. How does the structure of each organ in the digestive system relate to its
function? 3. How does the digestive system assist in maintaining the water balance
in the body? Cont.
• Stomach
• Chemical breakdown of materials by acid and
enzymes: protein digestion
• Mechanical processing through muscular
contractions
• pH (of 2) and enzymes will decontaminate incoming
food matter
• Forms chime
• Food mixed with water, HCl and other enzymes
• Parietal cells produce
• HCl
• Intrinsic factor required for vitamin B12 absorption
• Chief cells secrete pepsinogen which is going to be
converted into pepsin in the presence of HCl
• Goblet cells produce mucus to protect stomach lining
from being digested by the acid
2. How does the structure of each organ in the digestive system relate to its function? 3.
How does the digestive system assist in maintaining the water balance in the body? Cont.
• Liver
• Found in the upper right quadrant
• It weighs 3.5 lbs
• Secretes bile (important for lipid digestion)
which is carried to gall bladder by cystic duct
• Stores nutrients
• Produces plasma proteins
• Removes old RBC
• Detoxifies toxic substances
• Breaks down glycogen into glucose
2. How does the structure of each organ in the digestive system relate to its function? 3. How does
the digestive system assist in maintaining the water balance in the body? Cont.
• Gall bladder
• Stores and concentrates bile
• Passes bile into the small intestine to help
break down fats
• Bile is carried by the common bile duct
into the duodenum
• Formed by the union of the common
hepatic duct (from the liver) and the
cystic duct
2. How does the structure of each organ in the digestive system relate to
its function? 3. How does the digestive system assist in maintaining the
water balance in the body? Cont.
• Pancreas
• 6 inches long located behind the stomach
• Exocrine cells secrete buffers and digestive
enzymes:
• trypsin: breaks down proteins
• Chymotrypsin and carboxypeptidase: break down
proteins
• Pancreatic lipase: breaks down fats
• Pancreatic amylase: breaks down carbohydrates
• Secretes bicarbonates to deactivate the acid in the
chime exiting the stomach
• Endocrine cells secrete hormones
• Beta cells produce insulin – decreases sugar in
blood
• Alpha cells produce glucagon – increases sugar in
blood
2. How does the structure of each organ in the digestive system relate to
its function? 3. How does the digestive system assist in maintaining the
water balance in the body? Cont.
• Small intestine
• Food moves by peristalsis
• Long, narrow, has villi that absorb nutrients into
bloodstream
• Enzymatic digestion and absorption of water,
organic substrates, vitamins and ions
• Bulk of digestion occurs in the duodenum
• Bulk of absorption takes place in the jejunum and
ileum
• pH in duodenum is 6 and as it travels through the
small intestine it raises to 7.4 due to the
bicarbonate released by the pancreas
• Common bile duct and pancreatic duct enter the
duodenum at the hepatopancreatic sphincter
2. How does the structure of each organ in the digestive system relate to
its function? 3. How does the digestive system assist in maintaining the
water balance in the body?
• Large intestine
• Reabsorbs water and salts in the ascending colon and in
the cecum
• Dehydration and compaction of undigestible materials
in preparation for elimination
• Cecum
• Begins the process of compaction and absorbs water
• Colon
• Ascending, transverse, descending
• Bears pouches and longitudinal bands of smooth muscle
• Rectum
• Terminates in the anal canal
• Has internal and external sphincters
4. How do enzymes assist the process of digestion?
• Enzymes are proteins that help speed up or initiate chemical
reactions, including digestion.
•
•
•
•
•
Pepsin breaks down proteins
Carbohydrases break down carbohydrates
Lipases break down lipids
Proteases break down proteins
Nucleases break down nucleic acids
5. How do factors such as temperature, pH and concentration of enzyme
or substrate affect the rate of enzyme-catalyzed reactions?
• Enzymes work best within a particular
range of temperatures & pH values.
• For instance, salivary amylase works best at
37ºC (body temperature) and a pH of 6.8
(barely acidic).
• Pepsin works best at pH 2 and 37 C
• The higher the enzyme, substrate ratio,
the more effective the enzyme will be.
• Enzymes have a very narrow optimal
temperature and pH above and below
which it will cause the enzyme to not work
properly
6. What are BMI and BMR?
7. How can BMI and BMR help assess healthy diet and weight?
• Body mass index (BMI)
• Ratio of weight (kg) to
height (m)—used to
determine whether a
person is at a healthy
weight
6. What are BMI and BMR?
7. How can BMI and BMR help assess healthy diet and weight? Cont.
• Basal metabolic rate (BMR)
• Metabolism (total chemical reactions) while at complete rest. It is
combined with a person’s activity level to plan a healthy caloric
intake.
8. What are the health risks associated with being overweight or
underweight? 9. What body systems are affected when a person is
overweight or underweight?
Underweight (BMI of 19 for women, 20 for
men)
Overweight (BMI of 25 or more)
• Anemia & nutrient deficiencies
(CARDIO)
• Bone loss & osteoporosis (SKELETAL)
• Heart irregularities & blood vessels
disease (CARDIO)
• Amenorrhea (loss of periods for
women) (REPRODUCTIVE)
• Increased vulnerability to
infection/disease (IMMUNE)
• Delayed wound healing (IMMUNE)
•
•
•
•
Cancers (IMMUNE)
Depression (NERVOUS)
Type II Diabetes (ENDOCRINE)
Sleep Apnea
(RESPIRATORY/NERVOUS)
• Asthma (RESPIRATORY)
• Osteoarthritis (SKELETAL)
• Heart attack or stroke (CARDIO) due to:
High cholesterol, High blood pressure,
Arteriosclerosis
10. What is ATP?
• ATP is adenosine triphosphate, the energy molecule used by our
bodies to build up tissues (anabolism)
11. How is energy released from ATP and used to do work in the body?
• ATP releases energy by losing a phosphate group and turning into
ADP (adenosine diphosphate). The breaking of the bond gives off
energy.
• To strip off a phosphate group a molecule of water is added which
breaks the hydrogen bonds – Hydrolysis reaction
12. How do the air you breathe and the
food you eat relate directly to the
production of energy in the form of
ATP?
• The release of energy occurs in 3 steps:
• Glycolysis
• Kreb’s Cycle
• Electron Transport
• The process is cellular respiration.
• It occurs in the mitochondria of the cell
• You get glucose from the food you eat and the oxygen from the air you
breathe
• Together, these steps can make 38 ATP molecules from one glucose
molecule (taken in through food) that is in the presence of oxygen
(aerobic). If there’s no oxygen (anaerobic), the process is 15x less efficient!