Download L18 - The Digestive System

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Good morning everyone!
Welcome to SNC2D, which is a fancy way of saying Science for Grade 10 students in the Academic
stream. We will be getting started shortly, so please find your seat, take out your notebook / binder,
and get ready for a day of learning… hopefully. I am your teacher, Mr. Dobson!
As a quick reminder, please ensure that you are double checking Google Classroom every day for
updates about class work, ongoing assignments, and / or upcoming dates that are important in the
course. I highly recommend bringing a device that can access Google Classroom every day.
We respectfully acknowledge that we are on the treaty and traditional territory of the Mississauga of Scugog
Islands. We offer gratitude to the First Peoples for their care for, and teachings about, our earth, and our relations.
May we honor those teachings and continue to learn from those around us with an active, growth mindset.
The Digestive System – An Overview
Similarities Throughout Organisms
Digestive Tissue
The digestive tract is lined with epithelial tissue:
Goblet Cells: Secrete mucus, which protects
organs from enzymes / acid and helps move
materials throughout the tract.
Muscle Tissue: Contract without you thinking
about them. These contractions move food
through the tract to various components.
Villi: Small, finger-like projections that help in
the absorption of nutrients that pass over the
digestive tract’s tissue.
Spoiled Food and Toxins
Vomiting is one of our body’s natural defenses.
We “throw up” because the body has detected a
harmful substance or something annoying. The
body deems this as a threat and must expel it.
Nerve signals are sent to the brain. You become
pale, your heart rate increases, and you produce
extra mucus to protect your teeth from acid.
The diaphragm, chest wall, and abdominal
muscles contract at the same time, forcing the
contents up and out of the stomach.
The Mouth
The mouth is the beginning site of digestion. Digestion occurs both mechanically and chemically.
The mouth adds saliva (water and enzymes) to the bolus of food to break it down and soften it.
The mouth is directly connected to the esophagus for the next stage of digestion.
The Esophagus
The esophagus is a muscular tube that connects the mouth and the stomach.Why muscular though…?
Smooth muscle tissue contracts and relaxes without you even realizing it, pushing your food down.
The larynx protects foreign objects from entering the lungs.We cough when food becomes lodged.
The Stomach
The stomach holds food and churns it with hydrochloric acid to continue the process of digestion.
The lining of the stomach contains cells that release enzymes and acids to aid in food digestion.
Smooth muscle tissue contracts to “mix” the elements of the stomach thoroughly before it moves on.
The Intestines (Small and Large)
The lining of the intestines contains
cells that produce mucus and is
composed of smooth muscle tissue.
The small intestine is roughly 6m
long where nutrients diffuse through
the wall and enter into the blood.
The large intestine is roughly 1m
long where the lining absorbs water
from any indigestible food.
Accessory Organs
▪ The liver produces bile, a green fluid-like substance which helps break down fat in food located in the s. intestine.
▪ The pancreas produces insulin which helps to balance sugar levels in the blood and is necessary for diabetics.
▪ The gall bladder is located under the liver, which stores the bile that the liver produces; delivers to the s. intestine.