The digestive system
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The Digestive System. Features of the Generalized Vertebrate Gut. Oral Cavity - Origin. 1. Origin Heterostomes - most of the invertebrate phyla Mouth originates from the blastopore

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Oral cavity origin
Oral Cavity - Origin

1. Origin Heterostomes - most of the invertebrate phyla

Mouth originates from the blastopore

2. Deuterostomes - not formed early, but breaks through later in development; anus originates from the blastopore


Teeth
Teeth

1. Origin - dermal denticles

2. Structure

  • Enamel - hardest substance in the body,

    occurs above the gum line

  • Cementum - continuation of enamel

    below the gum line

  • Dentin-matrix

  • Pulp-living portion of tooth

Enamel

Dentin

Pulp

Cementum

Blood vessels

and nerves


Glands of the mouth
Glands of the mouth

  • Salivary glands secrete saliva

    • mucin - lubricant

    • salivary amylase - converts starch to glucose


Esophagus
Esophagus

1. Length-short in fish, longer in tetrapods to bypass lungs

2. Muscles

Upper end- striated

Lower 2/3 - smooth

3. Modifications of the esophagus - crop in birds for storing food


Stomach
Stomach

1. 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 stomachs
Specialized stomachs

  • Muscular gizzard of ground birds

  • 4 chambers of grazing mammals - ruminants

    rumen is specialized for storing food to be chewed later


Small intestine
Small 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


Caecum
Caecum

  • large sac at junction of small and large intestines

  • contains symbiotic bacteria that digest cellulose

  • our appendix is a rudimentary caecum


Colon
Colon

  • no digestion

  • reabsorbs H20 and ions

  • contains bacteria that synthesize Vitamin K

  • Fermentation of gases by bacteria


Liver
Liver

A. 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



Pancreas
Pancreas

A. Origin - outpocket of the gut

B. Functions

1. Exocrine - produces digestive enzymes

2. Endocrine - produces insulin that regulates blood glucose levels



Nutrition
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
Nutrient Classes

  • Water (H2O)

  • Carbohydrate (CHO)

  • Protein (Pro)

  • Lipid (Fat)


Amount of energy
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



Phytochemicals plant
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
Water & Micronutrients

  • Functions

  • Intake Sources

  • Losses

  • Dehydration

  • Balance

  • Maintaining Hydration


Water functions
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
Body Water (45 liters)

INTERCELLULAR

BLOOD/LYMPH (3)

(12)

INTRACELLULAR (30)


Sources of water
Sources of Water

  • Fluids - 550 - 1500 ml

  • Foods - 700 - 1000 ml

  • Metabolic H2O - 200 - 300 ml

  • Total 1450 - 2800 ml


Carbohydrates
Carbohydrates

  • Introduction to CHO

  • Terminology

    • Simple/sugars

    • Complex/Starch

  • Digestion

  • Metabolism Overview


Carbohydrates1
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
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
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
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
Disaccharides

  • Sucrose = Glu + Fru

    • Table sugar

  • Maltose = Glu + Glu

    • product of amylase digestion; beer; sprouts

  • Lactose = Glu + Gal

    • Milk sugar


Polysaccharides
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
Major Hormones of Digestion

  • Insulin - made in pancreas; lowersblood glu; increasesallenergy stores

  • Glucagon- made in pancreas; raises blood glu; decreases adipose fat & liver glycogen stores

  • Epinephrine (adrenaline) - made in adrenal glands; raisesblood 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 diabetesResults 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 diabetesGestational diabetes affects about 4% of all pregnant women - about 135,000 cases in the United States each year.

        • Pre-diabetesPre-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.



  • Take 12 oz H2O

  • add 10 tsp sugar

  • drink

  • ~ 160 empty calories, i.e.,

  • A soda


Proteins
Proteins

  • Structure

  • Digestion

  • Absorption

  • Roles in Body

    • Tissue maintenance & Growth

    • Regulation & Control

    • Energy



Protein structure
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
Regulation & Control Functions

  • Enzymes

  • Hormones (some)

  • Antibodies; immune system

  • Transport

  • Acid-base balance (buffers in blood)

  • Fluid & electrolyte balance




Lipids
Lipids

  • Classes

    • Triglycerides (TG)

    • Phospholipids (PL)

    • Sterols

  • Class Functions

  • Terminology

  • Digestion

  • Transport - Lipoproteins


Lipid classes
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
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
Phospholipid Functions

  • Cell membranes

  • Help transport other fats in blood

  • Precursor for some neural transmitters

    • Lecithin ----> Acetyl Choline

  • emulsifier in foods


Cholesterol functions
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
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
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



Essential fatty acids
Essential Fatty Acids fats

  • 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
Lipoproteins fats

  • 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
Low Density LP (LDL) fats

  • 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
High Density LP (HDL) fats

  • 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
Levels of LP & CVD Risk fats

  • 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)



  • ~50% fat from animal sources fats

  • ~ 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
Excretory System fats

  • 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




Route of waste
Route of waste fats

  • 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
Functional Unit of Kidney - Nephron fats

  • Glomerulus

  • Bowman’s capsule

  • Proximal convoluted tubule

  • Loop of Henle

  • Distal convoluted tubule

  • Collecting duct

  • 2 types – Juxtamedullary and cortical


Nephron filtration
Nephron - Filtration fats

  • 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.



Reabsorption
Reabsorption fats

  • 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)


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