Digestive System part II
Chemistry and Cells
Atoms
• Three major parts.
– Protons: Positive Charge. Inside Nucleus
– Neutrons: Neutral Charge. Inside Nucleus:
– Electrons: Negative Charge. Outside Nucleus
• 2 electrons in first shell
• 8 electrons in the second shell
• Eight is Great! Will not React with other
atoms.
• If the outer shell is not full it will react.
Combining Chemicals
Periodic
Table
Bonding
• Compound: When two or more different elements
combine.
• Hydrogen Bond: H2O - H2O
– When hydrogen bonds with another atom or molecule.
Bonds are like Velcro. Make and break easily.
• Covalent bond: CO2
– When atoms on the same side of the chart (same size)
bond. Share electrons.
• Both Hydrogen and Covalent bonds form molecules,
ionic bonds do not.
Ionic/
Covalent
Bonds
Combining Chemicals continued
• Ionic Bonds: When atoms on different sides
of the chart (different size) bond. Steal
electrons. Create Ions. Make teeth and bones.
– Ion: Charged particle either negative or positive.
NaCl = table salt
– Electrolytes: Ionic compounds that break into
cations and anions when dissolved. (Salt)
• Free Radical: Electrically charged ion with an
unpaired electron in its outer shell.
Antioxidants, What are they?
• Substances that inactivate oxygen derived
free-radicals
• Slows damage from free-radicals
• Examples: Selenium, Zinc Beta-carotene,
Vitamins C & E
Free Radicals
Acai Berry
Ph Scale
• Measured on grams of Hydrogen (H+)
– pH of 0= 1g of H+, pH of 1= .1g of H+
• Acid: form hydronium ions (H+)
– pH of less than 7 ( 1 to 6.9)
• Base: form hydroxide ions (OH-)
– pH of more than 7 (7.1 to 14)
• Acid + Base: salt & water, the solution is
neutral with a pH of 7.
– NaOH + HCL = H2O + NaCl with a pH of 7
What is a Buffer?
• Chemical substances that neutralizes small
amounts of an acid or base added to a solution.
• Why are these important to your body?
• three main buffers in the body:
– bicarbonate buffer system: in the blood and stomach
to neutralize acids
– protein buffer system: inter and extra cellular
buffering used with hemoglobin and blood
– phosphate buffer system: used in the urinary system
to remove H+ ions and make urine acidic
Metabolism: All chemical reactions
necessary to maintain life
• Catabolism - substances broken down, energy
released and captured to make ATP
• Anabolism - larger molecules built from smaller
ones
• Question: Why are they called anabolic steroids?
Chapter 19
Overview
Of
Digestion
The Digestive System and Body
Metabolism
Takes in food, breaks it down into nutrient molecules
and absorbs them into the bloodstream, then rids
the body of indigestible remains
https://www.supertracker.usda.gov/
The cartoon
Pill Cam
Metabolism & What We Eat
• Carbohydrates (glucose) - broken down to make
ATP, stored as glycogen. 1g= 4KCal
• Lipids- build cell membranes, myelin sheaths,
insulate, ATP. 1g= 9 KCal
• Proteins - structural materials hoarded by body
cells, ATP. 1g= 4KCal
• What is a calorie? Energy value measured in
kilocalories (Kcal) : amount of energy needed to
raise the temp. of 1 kg of H2O 1 deg C.
Anatomy of Digestive System
• Alimentary canal –
– or GI Tract - continuous hollow tube:
mouth, pharynx, esophagus, stomach, small
and large intestine
• Accessory digestive organs - assist: teeth,
tongue, glands
Mouth (Oral Cavity)
• Food enters
– Mucus membrane-lined cavity
– lips, cheeks, hard palate soft palate
– uvula - fingerlike projection of soft palate
Mouth
• Tongue - attached to hyoid bone and styloid
processes of skull
– papillae containing taste buds on surface
• Frenulum - secures tongue and limits its posterior
movements
Taste
Salivary Glands - 3 pair
• Parotid glands - anterior to ears
– mumps is inflammation of parotid
glands
• Submandibular and sublingual glands empty secretions into mouth through
ducts
Saliva
Polls
Everywhere
• Product of salivary glands, mixture of
mucus and serous fluids
–Creates a Bolus: mucus bound mass of food
–Enzymes of saliva:
• Amylase : for starch digestion
• Lysozyme: kills bacteria
Teeth
• Masticate (chew)
• Deciduous (baby or milk) teeth - first set (20);
formed from 6 months to 2 years
• Permanent teeth - cause baby teeth to fall out b/t
6 and 12
• 32 permanent teeth
• 3rd molars (wisdom teeth) form b/t 17 and 25;
sometimes absent or impacted in jawbone and
must be surgically removed
Enamel:
Dentin:
Hardest
substance of
the body!
(Calcium
phosphate
and calcium
carbonate)
Calcified
connective
tissue.
Cavities
Teeth by shape/function: omnivores
•
•
•
•
Incisors - chisel-shaped, cutting
Canines - fanglike, tearing/piercing
Premolars (bicuspids)
Molars - broad crowns w/ rounded tips, grinding
Organic Compounds:
contain C-H bonds
Carbohydrates
• Carbohydrate: fast energy
– made of Carbon, Hydrogen, and
Oxygen. 1:2:1 proportion. Sacchar =
sugar
• Monosaccharides:C6H12O6,
glucose,fructose (plants) glactose
(milk)
• Disaccharides: 2 sacchar’s: Sucrose:
table sugar, Lactose: milk
• Polysaccharides: Many sacchar’s:
starch: Grains, Legumes (beans)
Carbohydrate Metabolism
• Carbs - preferred fuel to produce ATP from glucose
(blood sugar): energy from bonds broken binds
phosphate to ADP to make ATP
– Carbon atoms leave as CO2 and hydrogen combines w/
oxygen to make water
• Question: Why do we breathe out CO2?
Carbohydrate Metabolism Homeostasis of blood glucose
• Hyperglycemia - high levels; excess stored as
glycogen and converted to fats
• Hypoglycemia - low levels; liver breaks down
stored glycogen and releases glucose to blood
Pharynx
– Nasopharynx (respiratory)
– oropharynx (potesterior to oral cavity)
– laryngopharynx (continuous w/
esophagus)
• Peristalsis: Alternating contraction
of muscles propel food into
esophagus
Peristalsis
Esophagus
• Conducts food from pharynx through diaphragm to
stomach
• 25 cm long
Walls of Alimentary Canal
• Mucosa - innermost layer; moist membrane
• Submucosa - blood vessels, nerve endings, lymph
• Muscularis externa - inner circular, outer
longitudinal smooth muscle
• Serosa - outermost layer
Peristalsis
Stomach
• C-shaped, left side, nearly hidden by liver and
diaphragm
– cardioesophageal sphincter - food enters from esophagus
– Pyloric sphincter - goes to small intestine
• 25 cm long
• when full, holds 4 L of food
• empty - collapses into folds (rugae)
• 3rd oblique layer in muscularis externa to move,
churn, mix, and pummel food
– chemically breakdown proteins
Food entering the stomach
Stomach: Physiology
• Mucosa has gastric pits which lead into gastric glands
that secrete gastric juice
– chief cells - produce protein-digesting enzymes
(pepsionogen)
– parietal cells - produce HCl
• Chyme is produced
• contractions squirt 3 ml of chyme into small intestine
• takes 4 hrs for stomach to empty
How stomach acid is
Made!
Organic Compounds:
All organic compounds contain Carbon.
• Protein: the working molecule
– 50 or more Amino Acids make a protein
– Food: Beans, meat, nuts
Protein
– Types of Proteins
• Muscle
• Enzymes: Control chemical reactions and can
be re-used like a key in a lock
• Hair
• When used for food: amine groups are
removed as ammonia which is toxic so it
combines w/ CO2 to form urea
General Metabolic Function
• Albumin - most abundant protein; holds fluids in
bloodstream
– insufficient albumin causes fluid to go from blood to
tissues (edema)
– Synthesize amino acids and detoxify ammonia
Small Intestine
• Major digestive organ
• Muscular tube extending from pyloric
sphincter to ileocecal valve
• average length: 2 m (6 feet)
• Hangs from coils suspended by mesentery
encircled by and frames it
Small Intestine - 3 structures that
increase absorption
• Microvilli - tiny projections that give fuzzy look
(brush border)
• Villi - fingerlike projections that give velvety
appearance
• Circular folds - deep folds of both mucosa and
submucosa
Small Intestine - 3 subdivisions
DJI
• Duodenum - curves around head of pancreas
• Jejunum - extends from duodenum to ileum
• ileum - terminal part that joins large intestine at
ileocecal valve
Small Intestine: Food Breakdown and
Absorption
• Takes 3-6 hours
• By end, digestion is complete and most absorption
has occurred
• Microvilli have brush border enzymes to break
down sugars and complete protein digestion
• Pancreatic enzymes from pancreatic duct and bile
from bile duct enter duodenum
Food Breakdown and Absorption
• Pancreatic juice digests starch, proteins, fats, and
nucleic acids; contains bicarbonate to neutralize
chyme
• When chyme enters, it stimulates hormones
secretin and cholecystokinin to release bile
Food Breakdown and Absorption
• Bile is necessary for absorption of fats and fatsoluble vitamins K,D,A
• At end, all that remains is water, indigestible food
and bacteria which enters large intestine
• Food propulsion - peristalsis
Organic Compounds: C-H bonds
• Lipids: long term energy, very few oxygen
atoms
– Cholesterol: LDL & HDL
• (HDL is heart healthy)
– Saturated fats: All C bonded to H. Lard,
and butter. Don’t eat Transfats (they have
been hydrogenated)
– Unsaturated fats: C is double bonded to
itself. Oil. Currently considered healthier.
Trans fats
Lipids
Lipids
• Neutral fats: saturated in animal products,
unsaturated in seeds, nuts, vegetable oils
• Cholesterol - egg yolk, meats, and milk
• Phospholipids: the plasma membrane
• PS What organelle in the cell makes lipids?
• Answer: Smooth ER
Lipid Metabolism
• Liver - make ATP, synthesize lipoproteins, clotting
protein and cholesterol for membranes or steroid
hormones
• Form myelin sheaths and fatty cushions around
organs
• Liver makes Bile ships it to the Gallbladder. Bile
emulsifies fats. The bilirubin in bile turns feces
brown.
Lipid Metabolism
• To be used for ATP synthesis, it must be broken
down into acetic acid; when not enough glucose,
acetone accumulates in blood making it acidic
(acidosis/ketosis)
– no carb diets, diabetes, and starvation
– People smell of keytones when they get diabetes, why?
Central Role of Liver
• Manufactures bile, detoxifies drugs and alcohol,
degrades hormones, makes substances vital to
body, metabolism
– This process uses many enzymes: Speed up
chemical reactions and reduce activation energy.
– Most enzymes are Proteins some are RNA
• We have more liver tissue than needed, so if
damaged, it regenerates rapidly and easily
General Metabolic Functions
• Liver maintains blood glucose levels
• After high carb meal, glucose is removed from
blood and converted to glycogen (glycogenesis) and
stored in liver
General Metabolic Functions
• As body cells remove glucose from blood, liver
breaks down stored glycogen (glycogenolysis)
• gluconeogenesis - make glucose from fat and
protein
Organic Compounds:
All organic compounds contain Carbon.
• Nucleic Acids: pg. 37 DNA and RNA
–Made of nucleotides: Sugar,
Phosphate, and X
• ATP: energy cells run on.
DNA
What is a calorie?
• Energy value measured in kilocalories (kcal) or
Calories (C
Vitamins: the last of the Organics
• Organic nutrients, small amounts
• No one food contains all required vitamins, need
balanced diet
• Most function as coenzymes: act w/ enzymes for
task
Vitamins: the last of the Organics
• Organic nutrients, small amounts
• No one food contains all required vitamins, need
balanced diet
• Most function as coenzymes: act w/ enzymes for
task
Minerals
• Requires adequate supplies of 7: Ca, P, K, S, Na, Cl,
and Mg; trace amounts of others
• Fats/sugars have none, cereals and grains poor
sources
• In veggies, legumes, milk, meats
Basal Metabolic Rate
• Carbs & proteins yield 4 kcal/g, fats yield 9 kcal/g
• Basal metabolic rate (BMR) - amount of heat
produced by body per unit time at rest; energy
supply for breathing, heartbeat, and kidney
function
Basal Metabolic Rate
• Avg. adult has BMR of 60-72 kcal/hr; influenced by
surface area, gender, age, and thyroxin production
(more thyroxin produced by thyroid gland, higher
O2 consumption and ATP use and metabolic rate)
Basal Metabolic Rate
• Hyperthyroidism - excessive rate, lose weight
despite increased hunger and food intake, bones
and muscles weaken
• Hypothyroidism - slow rate, obesity, diminished
thought process
Total Metabolic Rate
• When active, more glucose must be oxidized to
provide more energy for activities
• Total Metabolic Rate (TMR) - total amount of
kcal body must consume to fuel all activities
Total Metabolic Rate
• When total calories = TMR, weight is constant
• If eat more, excess calories appear as fat deposits
• If active w/o enough food, break down fat
reserves and even tissues to satisfy TMR
Large Intestine
• Larger in diameter, shorter in
length (1.5 m)
• Extends from ileocecal valve
to anus
• Dries out indigestible food by
absorbing water, eliminates
residue as feces
Large Intestine Subdivisions
• Cecum - saclike, first part
• Appendix - wormlike structure
hanging from cecum; ideal bacteria
location - appendicitis
• Colon - ascending, transverse,
descending, and sigmoid
• Rectum
• Anal canal - ends in anus which opens
to exterior; has external voluntary
sphincter and internal involuntary
sphincter
Large Intestine
• Lots of goblet cells to produce mucus to act as
lubricant to ease passage of feces
Large Intestine: Food Breakdown and
Absorption
• Residue is there 12-24 hours
• Bacteria metabolize nutrients and release
gases (methane, hydrogen sulfide)
• 500 ml of gas produced each day
Gallbladder
• Small, thin-walled green sac in the inferior surface of liver
• When digestion is not occurring, bile is stored and
concentrated by removal of water
– bile stored too long, it crystallizes forming gallstones
– Yellow-green, watery solution of bile salts, bile pigments
(bilirubin), cholesterol, phospholipids, and electrolytes
– bile salts emulsify fats to provide more surface area
Digestive System
Review
Disease: Jaundice
• Bile pigments enter bloodstream
• Can result from hepatitis (inflammation of
liver from viral infection of contaminated
water or blood transfusion) or cirrhosis
(severe damage from drinking excess alcoholic
beverages)
Nutrition and Metabolism
• Most foods used as metabolic fuels (transformed
into ATP); some nutrients build cellular molecules
• Energy value measured in kilocalories (kcal) or
Calories (C)
Nutrition
• Nutrient - substance in food used to promote
normal growth, maintenance and repair
• Carbohydrates, lipids, proteins - bulk of food;
vitamins, and minerals in minute amounts
.
• Water - 60% of volume of food
• Most foods are combination of nutrients from 5
food groups (grains, fruits, vegetables, meats,
and milk products)
Obesity Rates
in the US.
Dietary Sources of Major Nutrients Carbohydrates
• From plants except lactose and glycogen in
meats
• sugar - fruit, sugar cane, milk
• starch - grains, legumes, root vegetables
• cellulose - most vegetables
Food Breakdown and Absorption
• Absorption limited to vitamins, some ions, and most
of remaining water
• Feces - solid product delivered to rectum;
undigested food residue, mucus, bacteria, and
some water
Large Intestine: Propulsion and
Defecation
• Peristalsis and mass movements (long, slowmoving, powerful contractile waves that move over
colon 3-4 times daily to push contents toward
rectum)
– occur after eating; fiber increases strength of
contraction
Propulsion and Defecation
• When feces in rectum, defecation reflex causes
rectum to contract and anal sphincters to relax
• Diarrhea - food rushes through before water is
absorbed, can result in dehydration and electrolyte
imbalance
Propulsion and Defecation
• Constipation - food residue remains too long
and too much water is absorbed; due to lack
of fiber, poor bowel habits, or laxative abuse
Poll
Everywhere
Poll
Everywhere
Poll
Everywhere
A constipated body
Other Accessory Digestive Organs –
Pancreas
• Soft, pink, triangular gland extending from spleen to
duodenum
• produces enzymes that break down food and
neutralize acidic chyme from stomach, produces
hormones insulin, glucagon
Liver
• Liver - largest gland in body; under
diaphragm on right
– 4 lobes
– produces bile which leaves liver through
common hepatic duct
Developmental Aspects
• 5th week - alimentary canal forms
• cleft palate/lip - child unable to suck properly
• tracheoesophageal fistula - connection b/t
esophagus and trachea - causes drool, cyanosis
during feedings
Development Aspect
• Cystic fibrosis - blockage of pancreatic ducts so that
fats and fat-soluble vitamins are not digested or
absorbed
• PKU - inability of tissue cells to use phenylalanine
(amino acid) causes brain damage
Developmental Aspects
• Newborn: rooting & sucking reflex
• Appetite decreases in elementary age and increases
in adolescence
• Gastroenteritis - inflammation of GI tract due to
contaminated food
• Appendicitis - common in teens
Developmental Aspects
• Middle age - metabolic rate decreases 5-8% every
10 yrs
– ulcers & gallbladder problems
• Old age - activity of GI tract declines, taste and
smell decrease
– cancer of stomach and colon