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)