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Digestive System. Brainstorm: Why do we have to eat in order to stay alive? P.S. Helpful textbook pages include 446-450 (FYI). It all starts in your mouth!. Teeth grind up your food into smaller pieces that are easier to digest.
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Digestive System Brainstorm: Why do we have to eat in order to stay alive? P.S. Helpful textbook pages include 446-450 (FYI)
It all starts in your mouth! • Teeth grind up your food into smaller pieces that are easier to digest. • Bonus: What simple machine are your teeth? (this is going way back to Unit 1 in 6th grade) • Different kinds of teeth have different jobs. • Molars grind food down • Canines tear food • Incisors grab food • Saliva starts to break food down as you chew. • Contains enzymes (what are these again?) • Comes from salivary glands canine incisor molar
Food is delicious…but why? • Taste buds (which have touched on briefly) are tiny modified hairs on your tongue that tell our bodies what something tastes like. • Smell helps to enhance taste, why do you think this is? • Different parts of your tongue taste differently • This is a general overview, everyone is slightly different and has some overlap of sections
Onward to the Esophagus! • Now that you have thoroughly chewed your food you swallow your bolus (chunk of chewed food) • Bolus enters the esophagus • Muscular tube (~25 cm long) • Secretes mucus to keep food moist and moving (don’t you just LOVE mucus?) • Pushed down by smooth muscle • Process called peristalsis • So why doesn’t food go down our windpipe when we swallow? • Bonus: What is our windpipe called? • Bonus: What body system is it involved in? • Fun Fact Question: What organ do the digestive system and respiratory system share?
And now for the Stomach! • A stretchy, expandable, muscular bag that can fold on itself when “empty” • Houses digestive enzymes (like pepsin) and HCl (hydrochloric acid) that help break food down even further • Four things happen when food is heading to/has reached the stomach: • 1) Your stomach releases mucus (seriously this stuff is everywhere) to coat itself and protect its lining from acid • 2) Mechanical digestion mixes food by peristalsis • 3) Chemical digestion breaks food down with acids and enzymes • 4) Food becomes chyme, a “thin, watery liquid”
Small intestine yay! • Measures 4-7 m in length • Chyme enters the beginning of your small intestine (duodenum) where most digestion takes place • Bile (greenish liquid) is added by the liver and digestive solutions are added by the pancreas as well • Your pancreas also makes insulin (a hormone that allows sugar to enter your cells) • Bonus: Why is sugar important to your cells? • Absorbs food through folds and finger-like structures called villi (increase surface area over which nutrients are absorbed)
And last, but not least the Large Intestine! • Any undigested chyme enters large intestine, which absorbs water • It becomes more solid and is pushed toward the end of the large intestine (rectum) and out of the anus as feces
On a side (but important) note, eat your yogurt! • Your digestive tract contains millions of symbiotic bacteria that help aid in your digestion of food. • Bonus: What does symbiotic mean? • You need these bacteria to help break down and absorb vitamins • Bonus: What other part of your body is important for this? • Some of these bacteria live there all the time, while others are found in the food you eat (yogurt is one of those foods).
So…put your notes away, let’s see what we remember. • Turn to a neighbor and see if the two of you can accurately and adequately describe the process a sandwich goes through to digest in your body. • You have 3 minutes! • And one last time for good measure…MUCUS!!!!!!