Digestive System part IIChemistry 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

• 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

Periodic Table

Bonding

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

Acai Berry

Free Radicals

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 – chemical reactions that break down complex organic compounds into simple ones, energy is released and captured to make ATP

• Anabolism –synthetic (not produced naturally) process where larger molecules are built from smaller ones

Chapter 19

Overview Of

Digestion

https://www.supertracker.usda.gov/

The Digestive System and Body MetabolismTakes in food, breaks it down into nutrient molecules and absorbs them into the bloodstream, then rids the body of

indigestible remains

Pill Cam

The cartoon

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,salivary glands, liver, gallbladder and pancreas

Mouth (Oral Cavity)

• Food enters– Mucus membrane-lined cavity– lips, cheeks, hard palate soft palate– uvula - fingerlike projection of soft palate

Mouth• Tongue – muscle covered with mucous membrane,

attached to hyoid bone and styloid processes of skull– papillae upper surface and sides of tongue

which contains your taste buds• 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

• Product of salivary glands, mixture of mucus and serous fluids (99.5% water)–Creates a Bolus: mucus bound mass of food –Enzymes of saliva:

• Amylase : for starch digestion• Lysozyme: kills bacteria

Polls Everywhere

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 removedEnamel:

Hardest substance of the body! (Calcium phosphate and calcium carbonate)

Dentin: 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

• Carbohydrate: fast energy–made of Carbon, Hydrogen, and

Oxygen. 1:2:1 proportion. Sacchar = sugar• Monosaccharides:C6H12O6,

glucose,fructose (plants) • Disaccharides: 2 sacchar’s:

Sucrose: table sugar, Lactose: milk• Polysaccharides: Many sacchar’s:

starch: Grains, Legumes (beans)

Carbohydrates

Carbohydrate Metabolism

• Carbs - preferred fuel to produce ATP from glucose (blood sugar)

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

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

Peristalsis

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– 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

Protein

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)

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 subdivisionsDJI

• 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 fat-soluble 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: Lard, and butter. –Unsaturated fats: C is double bonded

to itself. Oil. Currently considered healthier.

LipidsTrans fats

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 SystemReview

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, slow-moving, 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

A constipated body

Poll Everywhere

Poll Everywhere

Poll Everywhere

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