The Digestive System
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Transcript of The Digestive System
The Digestiv
e System
The Digestiv
e System
Features of the Generalized Vertebrate
Gut
Features of the Generalized Vertebrate
Gut
Oral Cavity - OriginOral Cavity - Origin1. Origin Heterostomes - most
of the invertebrate phyla Mouth originates from the
blastopore2. Deuterostomes - not
formed early, but breaks through later in development; anus originates from the blastopore
TeethTeeth1. Origin - dermal denticles2. Structure
� Enamel - hardest substance in the body,occurs above the gum line
� Cementum - continuation of enamelbelow the gum line
� Dentin-matrix � Pulp-living portion of tooth
EnamelDentinPulp
Cementum
Blood vesselsand nerves
Glands of the mouthGlands of the mouth Salivary glands secrete
saliva mucin - lubricant salivary amylase - converts starch to glucose
Esophagus1. Length-short in fish,
longer in tetrapods to bypass lungs
2. MusclesUpper end- striatedLower 2/3 - smooth
3. Modifications of the esophagus - crop in birds for storing food
StomachStomach1. Occurrence Present in
invertebrates with complete digestive tract
Absent in most lower chordates, even fish
2. Regions
Functions of the stomach
Functions of the stomach
Little absorbtion by stomach - water and alcohol
secretes HCl - very acid pH mucin - lubricant pepsin - digests proteins to
shorter peptides gastrin - hormone which
regulates HCl secretion
Specialized stomachsSpecialized stomachs Muscular gizzard of ground birds 4 chambers of grazing mammals
- ruminantsrumen is specialized for storing
food to be chewed later
Small IntestineSmall Intestine Primary site of digestion Digested food absorbed here -
absorbtion Enzymes
peptidases - peptides to amino acids lactase - lactose (milk sugar) to
simple sugars maltase - maltose to glucose sucrase - sucrose to simple sugars
Absorbtion in the Small Intestine
Absorbtion in the Small Intestine
Pancreas - enzymes for digestion
Pancreas - enzymes for digestion
lipase - fats to triglycerides trypsin - proteins to shorter
peptides nucleases - DNA & RNA secretin - hormone which
stimulates buffering of HCl
CaecumCaecum large sac at junction of small and
large intestines contains symbiotic bacteria that
digest cellulose our appendix is a rudimentary
caecum
ColonColon no digestion reabsorbs H20 and ions contains bacteria that
synthesize Vitamin K Fermentation of gases by
bacteria
LiverLiverA. Development - outpocket of
the gut - tube that remains is the common bile duct
B. Digestive function - produces bile that emulsifies fats
Bile is stored in the gall bladder for secretion into the small intestine
Other function of the liver
Other function of the liver
C. Other functions - stores glycogen stores fats - cholesterol filters and stores toxic materials
destroys red blood cells
Circulation and the Liver
Circulation and the Liver
PancreasPancreasA. Origin - outpocket of the gutB. Functions
1. Exocrine - produces digestive enzymes
2. Endocrine - produces insulin that regulates blood glucose levels
The fate of food
NUTRITION Nutrient - specific substance that
must be taken into the body in sufficient quantities to meet the body’s needs Essential Nutrient - required
preformed; body cannot make it or cannot make enough to meet needs
Nonessential nutrient - body can make IF raw materials are available
Body needs BOTH to function
Nutrient Classes Water (H2O) Carbohydrate (CHO) Protein (Pro) Lipid (Fat)
Amount of energy?? calorie - energy needed to raise 1 gm
of H2O 1 degree Centigrade Kilocalorie (kcal) - 1000 calories;
energy needed to raise 1 liter of H2O 1 deg. C
Direct Calorimetry - measuring the heat (energy)
Indirect Calorimetry - measuring the CO2 & O2 and “deriving” the energy
Energy from NutrientsN u t r i e n t C l a s s C a l o r i e s / g r a m
C H O 4
P r o 4
F a t 9
A l c o h o l 7
Phytochemicals (plant) Only few of 10,000’s studied associated with
decrease CVD & cancer risk decrease infections increase immune function
examples - flavonoids; carotenoids (> 600); isoflavones; plant sterols
Best to get from food NOT supplements
** soy; tomatoes, garlic, onions, legumes, green tea; cruciferous vegetables, red wine, grapes
I.e., EAT MORE AND WIDER VARIETY OF FRUITS & VEGETABLES
Water & Micronutrients
Functions Intake Sources Losses Dehydration Balance Maintaining Hydration
Water Functions
Regulates body temperature cools body temperature AND evens heat
throughout body Environment for cells & chemical
reactions Transport (blood)
blood pressure fxn of volume of H2O secondary lubrication of joints takes part in chemical reactions
Body Water (45 liters)
intracellularintercellularblood/lymph
BLOOD/LYMPH (3)
INTRACELLULAR (30)
INTERCELLULAR(12)
Sources of Water
Fluids - 550 - 1500 ml Foods - 700 - 1000 ml Metabolic H2O - 200 - 300 ml
Total 1450 - 2800 ml
Carbohydrates Introduction to CHO Terminology
Simple/sugars Complex/Starch
Digestion Metabolism Overview
Carbohydrates.... First link in the food chain Photosynthesis - plants store some of
sun’s energy (0.1%) in chemical bonds of CHO
CO2 + H2O -----> CHO ALL PLANT foods have CHO Only significant animal sources of CHO
are milk and some milk products Energy source for man - 8% Eskimos;
>70% some non-industrialized countries
CHO Functions Energy - all cells use Some cells (RBC, brain) can use
only CHO until starvation sets in Needed for effective burning of fat Spares protein from use for energy Fiber, alternative forms of CHO,
provides a number of benefits
CHO Terminology Saccharide = building block Simple CHO = “sugars”
(1-3 saccharides) mono (1), di (2), tri (3)
Complex CHO = Starch or Amylose (many saccharides) - poly
Complex CHO = Fiber Different bonding than starches
Monosaccharides Glucose (Glu) - most abundant
CHO; part of table sugar; “blood” sugar
Fructose (Fru) - found in fruit & honey; part of table sugar
Galactose (Gal) - part of milk sugar; generally not found free in nature
Disaccharides Sucrose = Glu + Fru
Table sugar Maltose = Glu + Glu
product of amylase digestion; beer; sprouts
Lactose = Glu + Gal Milk sugar
Polysaccharides multiple glucose (usually) units
bound together Starch/Amylose = many Glu
Storage form of energy in plants Fiber - # different kinds; some are
multiple Glu units but different chemical bonding from Amylose examples - cellulose; pectin
Fiber (cont.) - often the structural CHO in plants ONLY FOUND IN PLANTS
Glycogen = storage form of CHO in animals (many Glu units) very highly branched to aid release
Major Hormones of Digestion
Insulin - made in pancreas; lowers blood glu; increases all energy stores
Glucagon - made in pancreas; raises blood glu; decreases adipose fat & liver glycogen stores
Epinephrine (adrenaline) - made in adrenal glands; raises blood glu; decreases all energy stores
CHO Health Issues Fiber Abnormal CHO Metabolism
Lactose Intolerance Hypoglycemia Diabetes Mellitus
Type 1 diabetesResults from the body's failure to produce insulin, the hormone that "unlocks" the cells of the body, allowing glucose to enter and fuel them. It is estimated that 5-10% of Americans who are diagnosed with diabetes have type 1 diabetes.
Type 2 diabetes Results from insulin resistance (a condition in which the body fails to properly use insulin), combined with relative insulin deficiency. Most Americans who are diagnosed with diabetes have type 2 diabetes.
Gestational diabetes Gestational diabetes affects about 4% of all pregnant women - about 135,000 cases in the United States each year.
Pre-diabetes Pre-diabetes is a condition that occurs when a person's blood glucose levels are higher than normal but not high enough for a diagnosis of type 2 diabetes. There are 41 million Americans who have pre-diabetes, in addition to the 20.8 million with diabetes.
Syndrome X – insulin resistance (the inability to properly deal with dietary
carbohydrates and sugars), abnormal blood fats (such as elevated cholesterol and triglycerides), overweight, and high blood pressure.
Sources of Sugar
Beverages29%
Processed45%
Home Use26%
BeveragesHome UseProcessed
Take 12 oz H2O add 10 tsp sugar drink ~ 160 empty calories, i.e., A soda
Proteins Structure Digestion Absorption Roles in Body
Tissue maintenance & Growth Regulation & Control Energy
Distribution of Body Proteins
Muscle50%
Bone20%
Skin10%
Other20%
MuscleBoneSkinOther
Protein Structure Made up of carbon, oxygen,
hydrogen & nitrogen (C, O, H, N) Amino acids (aa) are building blocks 9 essential 11 nonessential (can be made from
other aa or carbon skelton (“glucose”) if N available
AA differ by side chain (R group)
Regulation & Control Functions
Enzymes Hormones (some) Antibodies; immune system Transport Acid-base balance (buffers in
blood) Fluid & electrolyte balance
Protein Sources (US)
Meats48%
Legumes5%
Dairy21%
Vegs7%
Grains19%
MeatsLegumesDairyVegsGrains
Protein in Foods
“Food” Serving gm Pro M Meat 3 oz 21 gm M Dairy 1cup or 1 oz 8 gm Vegetable 1/2 cup 2 gm Grain 1 sl or 1/2 cup 3 gm Legume 1/2 cup 7-8 gm
Lipids Classes
Triglycerides (TG) Phospholipids (PL) Sterols
Class Functions Terminology Digestion Transport - Lipoproteins
Lipid Classes Triglycerides
made of 3 fatty acids (fa) & 1 glycerol fa 4-22 Carbons long; mostly 16-20 95% of dietary lipids (fats & oils)
Phospholipids 1 fa replaced by a phosphate group
Sterols complex ringed structures; noncaloric ex. cholesterol & Vit D
TG Functions Concentrated energy (diet and main
storage form) Provides essential fatty acids (linoleic;
linolenic) Carrier of Fat Soluble Vits (A,D,E,K) Body Insulation & padding around organs Cell membranes Adds flavor & texture to foods Contributes to satiety
Phospholipid Functions Cell membranes Help transport other fats in blood Precursor for some neural
transmitters Lecithin ----> Acetyl Choline
emulsifier in foods
Cholesterol Functions Cell membranes Precursor for Vit D & some
hormones (estrogen, testosterone) Major component of bile ONLY FOUND IN ANIMALS; NEVER
FOUND IN PLANTS not an essential nutrient since man
makes
Saturated Fats maximum # of Hydrogen atoms usually solid at room temp. mostly from animal sources Exceptions - tropical oils (palm,
coconut) are very saturated raise blood cholesterol
Unsaturated Fats fewer H atoms; double bonds b/t Carbons usually liquid at room temp. mostly plant and fish sources more chemically active (turn rancid
faster) lower blood cholesterol Monounsaturated fat acid (MUFA) - 1
double bond (minus 2 H) Polyunsaturated fat acid (PUFA) - 2 or
more double bonds
Dietary fats (TG) really mix of saturated and unsaturated fats
Classified by predominate type
Fatty acids can differ by 1) degree of saturation or 2) length (# carbons) BUT NOT by calories (all 9 kcals/g)
Essential Fatty Acids Linoleic (Omega 6/n-6) - found mostly in
plant oils Linolenic – (n-3) found mostly in cold-
water fish and some plant oils (canola oil, nuts, seeds)
Deficiency leads to poor growth, liver problems, dermatitis
O-6 to O-3 ratio MUCH higher than in Hunter Gatherers - inc risk # diseases or adverse outcomes (CVD, pregnancy, learning, bone health)
Lipoproteins Transport lipids mixture of protein and lipids
Pro & phospholipids are water soluble packaged so water soluble cpds on
outside and insoluble cpds on inside like homogenized milk
LP have different forms, functions, & effects on CVD risk
Low Density LP (LDL) remnant of VLDL after most TG removed very HIGH in Cholesterol
major component of total blood cholesterol not always effectively cleared by liver so
other tissues remove including artery walls esp when cholesterol has been modified
risk of “high blood cholesterol” is from LDL, i.e., increases risk of CVD
High Density LP (HDL) made by liver & intestine & then
altered in blood carries cholesterol from tissues
(including arteries) & other LP to Liver Reduces risk of CVD Ratio of LDL/HDL may be better
predictor of CVD risk than any single LP or total blood cholesterol level
Levels of LP & CVD Risk HDL > 60mg/dl = Low risk HDL < 35 mg/dl = High risk LDL/HDL ratio < 4 = Low risk
men’s HDL run from high 30’s to high 40’s
women’s from low 50’s to low 60’s (estrogen effect)
Sources of Fat
Meats22%
Fats/ oils34%
Dairy18%
Grains10%
Sweets/ Frt10% Vegetables
6%
MeatsFats/ oilsDairyGrainsSweets/ FrtVegetables
~50% fat from animal sources ~ 75% Saturated fat from animal sources
6 foods foods provide 1/2 sat. fat cheese; beef (esp ground), milk, baked
goods, margarine, butter Trend towards less animal & more plant
fat lower % of fat 42% (60’s) -> 36% (80’s) -
> 34% now BUT > amount of fat
Excretory System
Among vertebrates the #1 Apparatus in the Excretory System is the KIDNEY
Filters 2000L of blood/day 3 Functions
Filtration – Blood Filter Reabsorption – Selective – take back the good stuff –
leave the waste Secretion and Excretion– secretion of foreign molecules
and waste across membranes of capillaries and kidney tubules – opposite of reabsorption Excretion of waste - Urine
Basic Structure of Kidney Units
The Mammalian Kidney
Route of waste In the nephron tubule,
filtration occurs from glomeruli into Bowman's capsule The filtrate passes from Bowman's capsule through the PCT (proximal convoluted tubule), the loop of the nephron (loop of Henle), the DCT (distal convoluted tubule), before reaching a collecting duct.
Now, just dumping out the filtrate would be a waste (literally) and would not address issues of osmoregulation.
Functional Unit of Kidney - Nephron
Glomerulus Bowman’s capsule Proximal convoluted
tubule Loop of Henle Distal convoluted
tubule Collecting duct
2 types – Juxtamedullary and cortical
Nephron - Filtration•Filter is non-selective except for size ( <70,000 MW; 7 nm in diameter).
•Blood cells and proteins do not pass through the filter.
•Fluid in Bowman's capsule much like plasma without the proteins.
Large amounts of water are necessary for filtration.
Most of this water is reabsorbed back into the circulation through the tubules - proximal & distal conv. tubules and Henle’s loop.
Reabsorption Need to reabsorb stuff (H20, ions,
nutrients) or animal literally urinate itself to death
180L of water leave the blood in filtrate Water, selected ions, glucose, and other
items must be reabsorbed This reabsorption most typically involves
the use of energy to reclaim sodium (and other items tagging along with it)