Digestion and Excretion

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Digestion and Excretion

• 38-1 to 38-3

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By the end of this digestion lesson you should be
able to

1. Explain why your body needs food
2. Explain how the digestive system allows you to
   use your food
3. Describe the path that food takes through your
   digestive system
4. Explain the functions of the major structures in
   the digestive system

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Why is eating such a vital part of your day?

• Your body needs the fuel (energy) that is can
  extract from your food
• Your body cells convert the chemical energy
  stored in your food (calories) into ATP

So why not just eat these all day???
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Your balanced diet should include.
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Our body needs nutrients like

• Water
• Carbohydrates
• Fats
• Proteins
• Vitamins
• Minerals

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Vitamins

• Organic molecules that work with enzymes to
  regulate body processes
• Diets lacking certain vitamins can have serious
  consequences
• 2 Types
• Fat-soluble - A, D, E K can be stored for
  future use
• Water-soluble - B varieties, C, Niacin,
  Pantothenic acid cant be stored in the body

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Minerals

• Inorganic nutrients needed by the body in small
  amounts
• Ex Calcium, Iron, Magnesium, Sodium, Potassium
• What are they needed for?

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Digestion

• Breaks down food into small molecules that can be
  used by our cells
• Includes the mouth, pharynx, esophagus, stomach,
  small intestine, large intestine
• Other helpful structures are the salivary glands,
  pancreas, and the liver

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The Mouth

• Mechanical digestion - the teeth tear and crush
  food
• Chemical digestion - enzymes break down
  carbohydrates (amylase) and microorganisms
  (lysozyme)
• THINK ABOUT IT
• Where do the enzymes come from?

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The Esophagus

• The food tube that the bolus travels through to
  reach the stomach
• Peristalsis draws the food down
• The cardiac sphincter prevents food from leaving
  the stomach

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The Stomach

• Large muscular sac
• Mechanical Digestion - muscle contractions
  produce a fluid and food mixture called chyme
• Chemical Digestion - gastric glands release
  lubricating mucus, hydrochloric acid, and pepsin
• What does pepsin do?

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The Small Intestine

• Food enters through the pyloric valve
• Most chemical digestion and absorption occur here
• Enzymes from the pancreas, liver and intestine
  lining continue to break down food
• Divided into three parts Duodenum, jejunum, and
  the ileum

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The Small Intestine
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Digestion in the Small Intestine

1. Liver - produces bile to digest fats
2. Pancreas -
3. Produces enzymes that break down carbohydrates,
   proteins and nucleic acids
4. Produces the base, sodium bicarbonate that allows
   the other enzymes to be effective
5. What else does it do?

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Absorption in the Small Intestine

• Made of folded surfaces covered with villi that
  increase the surface area for absorption
• Capillaries line the villi in order to absorb
  small carbohydrates and proteins
• Lymph vessels absorb some fats
• Water, cellulose and undigestible substances
  leave the small intestine

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The Large Intestine

• Colon
• Removes the water by absorbing it from the
  remaining chyme
• Bacterial colonies produce compounds for the body
  like vitamin K
• Wastes are eliminated through the rectum

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Food for thought.

1. Write down on a scrap piece of paper the complete
   meal you ate for dinner last night. List out
   each part of your meal.
2. Did you consume a balanced diet? Show what
   nutrients, vitamins and minerals you ate by
   writing them next to the food they came from.
3. What enzymes were hard at work in your stomach???

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Tonights Assignment

• Read vocabulary on 38-3
• Complete the worksheets

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By the end of this lesson on excretion you should
be able to

1. Describe the organs that make up the excretory
   system
2. Explain how the kidneys work to maintain
   homeostasis in your body
3. Explain how the lungs and the skin participate in
   excretion

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Excretion

• Removes the wastes produced by our cells like
  excess nitrogenous wastes (urea), salts, and
  carbon dioxide
• Urea a toxic compound produced when amino acids
  are used for energy
• Major excretion organs are the skin, kidneys, and
  lungs
• What waste does each organ release???

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The Kidneys

• The size of a clenched fist
• Removes urea, excess water and other wastes from
  the blood in the renal artery
• Transports wastes to the urinary bladder

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What does a kidney do?

• Kidneys filter the blood!!!

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Parts of the Kidneys

• Inner part renal medulla
• Outer part renal cortex
• Basic functional units nephrons
• 1 million per kidney
• Filters and reabsorbs
• Empties wastes into the ureter

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Filtration

• Occurs in the capillary network called the
  glomerulus that is surround by the Bowmans
  capsule
• Pressure pushes out the filtrate made of water,
  urea, glucose, salts and amino acids

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Reabsorption

• Occurs in the renal tubules
• Materials are actively transported from the
  filtrate back into the blood leaving the urine -
  the bodys waste product
• The urine is stored in the bladder and then
  released through a tube called the urethra and
  removed from the body

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So how do the kidneys help to maintain
homeostasis???

• Regulate water content of the blood
• Maintain blood pH
• Removes wastes from the blood

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SELF QUIZ

1. What other systems work with the excretory
   system?
2. How does your liver perform a function similar to
   your kidneys?
3. COMPLETE THE 38-3 worksheet