Chapter 39Digestive and Excretory systems

Your Body’s Need for Food- Your body needs energy, factors include, age, activity, your sex,

growth, etc…- You get this from foods and beverages

- Nutrient: substance required for energy, growth, repair, and maintenance- Examples: carbs, lipids, proteins, vitamins, and minerals

- Digestion: process of breaking down food, both physical and chemical.

- Calorie: amount of heat energy required to raise the temp of 1 g of water 1 degree Celsius.- Notice the capital C, nutritionists us the unit Calorie (equals

1000 calories) or Kcals.

Review: Carbs, lipids, and proteinsCarbs: sugars (single sugars called monosaccharides)

- glucose, fructose, and others found in foods like fruits and honey- starches (in cereal grains) and vegetables- cellulose (in plants) source of fiber, helps secrete mucus, increases

passage of food.Proteins: important building blocks of amino acids, which in turn make more Proteins.

- excess proteins typically converted to fat- 20 amino acids, 10 need to be consumed- no single plant has all, that is why it is recommended to eat a variety

Lipids: Fats- insoluble in water, used for making steroid hormones and cell

membranes- help store energy- saturated fats typically the bad ones.

Balancing Nutrients and Energy- No matter the source, excess calories are stored as glycogen or

body fat- Eat more calories than you burn, get fat, burn more calories than

you eat, get skinny - Obesity is being more than 20% heavier than your ideal weight.- Obesity significantly increases health risk (diabetes, heart disease,

etc…)

The Food PyramidUSDA food pyramid is the recommended daily servings for an average person.Top is bad, bottom is good.

Vitamins, minerals, and water- vitamins: organic substances that occur in many foods necessary for normal

metabolic functions- Fat soluble: A, D, E, and K (excess amounts can be toxic), can be stored in

body fat- See table 1 page 904. ( you should know vitamin and role)

- Minerals: naturally occurring inorganic substances used in making structures and substances in body- Minerals are soluble in water, must be replaced dailey- See table 2 page 905. (you should know mineral and role)

Water: transports everything, found everywhere, 2/3 of your body weight is water.

Home work Pg 905 section review #’s 1-6

Digestion- The breaking down of food both physically and chemically- Quiz is on figure 5 page 906 (no hand out) add appendix- Steps in digestion

- Starts in the mouth. Food is smashed and shredded (physical) tongue mixes, saliva moistens (contains amylase which is an enzyme that begins breaking down carb’s).

- Moves down pass the pharynx, epiglottis blocks off wind pipe, and food moves into the esophagus.

- Esophagus connects mouth to the stomach (about 25 cm’s long) food is pushed down via muscle contractions called peristalsis.

- Takes about 5-10 seconds for food to pass down into the stomach.- The stomach: Sphincter muscle (valve that allows food into, but prevents it from

going the wrong way…unless…gross….blowing chunks)- Stomach mechanically breaks down food, stores food, and breaks down proteins- Very acidic (called gastric juices) combo of hydrochloric acid and pepsin.

- Gastric juices, HCl and pepsin, break bonds and unfold large proteins.- Peristaltic waves are used to mix the contents- Food can spend from 2 to 6 hours in the stomach- About 2 L’s of HCl is secreted every day- Mucus in the lining of the stomach protects it from the 1.5 pH (or lower)The small intestine- Sphincter muscle also allows food out of stomach into the small intestine.- About 6 m long- Main function digestion and absorption of nutrients- Peristalsis mixes the food.- Takes 3 to 6 hours- First part called the duodenum, receives secretions from the pancreas, liver,

and gallbladder.

- Lipases (pancreatic enzymes) for digesting fats- Bile: greenish fluid produced by the liver, breaks up fat globules

called emulsification (big fat globs to little fat droplets)- Gallbladder stores bile until it is needed- Most absorption takes place in the S.I.- Villi: fingerlike projections, increase the surface area for better

absorption.The Large Intestine- The part of the food not for energy production are considered

waste and will now move into the L.I.- Also called the colon- Much shorter than the S.I. however it has a much larger diameter- Not coiled rather 3 relatively straight segments.- No digestion takes place in the colon

- Mostly water and mineral ions are absorbed in the L.I.- Loaded with a thriving colony of bacteria, they synthesize many

compounds that your body needs- Vitamin K and several of the B vitamins- Also aid in compacting and transforming undigested materials into

the feces (final waste product)- Last stage is the rectum- Solid feces is removed from the body via the anus- Typically 12 to 24 hours from start to finish- Diarrhea (waste move to quickly through the L.I.) watery feces- Constipation (food remains for to long in the L.I.) hard feces- Water balance is key in both of the above.

The livers role- In digestion

- Bile to aid in emulsification, also promotes absorption of fatty acids, and fat soluble vitamins

- Jaundice, excessive yellowing of the eyes, skin, and urine; due to increased bile pigments in the blood. Often a result of hepatitis or an inflammation of the liver. Other diseases as well

- Liver is about the size of a football, and weighs 3 lbs.- In metabolism

- Food is transported to the liver- Stabilizes blood sugar (converts extra sugar to glycogen for storage)- Also breaks down glycogen when needed for energy- Modifies amino acids.- Monitors the production of cholesterol- Detoxifies poisons- Heavy metals tend to get stored in the liver, since they can’t be broken

down

- Cirrhosis is the scaring of the liver cells, caused by damage via: viral infections, drug or alcohol use, or traumatic injury.

ExcretionThe body must remove waste to maintain osmotic balanceExcretion: is the process that rids the body of toxic chemicals, excess water, salts, and CO2Organs of excretion: Lungs, Kidneys, skinLungs: CO2Skin: excess water and salts (sweat)Kidneys: urine

The liver converts ammonia to Urea (less toxic nitrogen waste) which is carried to the kidneys which removes it from the blood stream

The Kidneys- A pair of bean shaped, reddish brown organs located in the lower back, about

the size of a small fist- Consists of millions of blood filtering units called nephrons. (pic on later

slide)- Three different phases occur in nephrons

- Phase 1: filtration: begins a the cup shaped capsule called “Bowmans” capsule- Enters Bowmans cap. Arterioles split into tiny network of capillaries

called a glomerulus (these act as the filtration device). Pressure forces fluid into the hollow interior of the BC, called filtrate.

- Mostly water, salt, glucose and AA’s; blood, cells, proteins, and others are to large and stay in the blood stream.

- Phase 2: Reabsorption: filtrate passes from the BC into renal tubules (which form a loop) where useful molecules like glucose, ions, and some water are extracted.

- Phase 3: secretion: some substances pas from the blood into the filtrate directly (secretion)- Urine formation: Urine: made up of water, urea, some salts, and others chemicals are left

over after reabsorption - Collecting ducts receive fluid from nephron segments and empty into areas that lead

to ureters (tubes that carry urine from the kidneys to the urinary bladder).- Urine can be very concentrated, so NO it is not a good source for drinking when

stranded.- Elimination of urin

- Ureters direct urine into the urinary bladder (stores urine)- UB can hold up to about .6 liters of urine (males tend to be larger) approx. 1.7-2.3

Liters per day- Urine is forced out via a tube called the urethra- Process is called urination- Stretch receptors on the bladder send signals to the spinal cord saying its time to go