Digestive System Notes

Digestive System Function: Help change foods into simpler molecules that can be absorbed into the body and then used by the cells Write what’s in blue Do NOT write what's in black

Ingestion – to take in food into the body Digestion – to break down and absorb food

Mouth Salivary glands Stomach Pancreas Large intestine Small intestine Pharynx Esophagus Liver Gallbladder Rectum The Digestive System Write in all the following Labels:

Digestive System Mouth & Teeth do mechanical digestion by chopping up food

Digestive System –Saliva moistens food and begins the process of chemical digestion by adding the enzyme Amylase – enzyme that breaks down starch into sugar

Enzymes are chemicals made by cells that allow chemical reactions to happen faster

You have three pairs of salivary glands

The secretory cells of the salivary gland are connected to the mouth by small tubes called ducts.

Salivary Gland

Tongue & Taste Buds

What is the tube leaving the mouth called that is a passageway for both food and air? Pharynx Uvula: unique to humans, it secretes a lot of saliva & may help with keeping your throat moistened during speech but we still have more to learn about what it does

The pharynx splits into two tubes: the esophagus and the trachea (at the front of your throat) The epiglottis controls the opening of these two tubes

Digestive System Esophagus: –Muscular tube that takes food to the stomach by the process of peristalsis

Digestive System –Peristalsis: takes clump of food (bolus) down esophagus by contractions of the throat muscles

Digestive System Stomach: Mechanical and Chemical digestion –Mechanical digestion: stomach muscles churn food bolus to help break them down & to mix with digesting chemicals (acids & pepsin)

Chemical digestion: Stomach makes Hydrochloric acid (HCl) that activates the enzyme Pepsin, which starts the process of protein breakdown which will continue through the intestines

Pepsin that is activated by stomach acids is able to break down proteins

Ulcers happen when stomach acid gets through the protective mucus covering of the stomach and begins to dissolve stomach cells

Until the 1990’s it was thought that ulcers were caused by excess production of stomach acid by the parietal cells. The acid was thought to “eat” through the mucus and begin dissolving the cells.

It was discovered the real culprit was a bacteria that could get through the mucus lining and kill cells.

Most ulcers are caused by the bacteria H. pylori

Digestive System –Chyme: Mixture of stomach fluids and food produced by contracting stomach muscles

Chyme passes out of the stomach through the pyloric sphincter into the small intestines to complete digestion.

Small Intestine: where most chemical digestion occurs –Chyme (moist, partly digested food) enters the duodenum (first part of small intestine) & is mixed with digestive enzymes from the pancreas, liver & cells lining the small intestine

Digested nutrient molecules are absorbed into the blood stream in the small intestines

Digestive System –Villi: fingerlike projections that cover the folded surfaces of the small intestine Increase surface area so nutrients are absorbed faster

Your liver is just under your diaphragm which divides the heart and lungs from the abdomen.

Liver: Secretes bile to dissolve fats and breaks down toxic substances like alcohol, drugs etc.

Bile is stored in the gall bladder until it is needed for fat digestion

The bile is carried into the small intestines by the bile duct

Bile surrounds fat to make small droplets, which can easily be digested by enzymes

–Pancreas: Has three important functions 1) Make and release two hormones important in blood sugar level regulation: Insulin & Glucagon Pancreas

Insulin & Glucagon Insulin & Glucagon work together to maintain normal blood glucose levels They use negative feedback to maintain homeostasis Insulin: tells cells to take up more glucose Glucagon: tells liver & other cells to breakdown glycogen (short term glucose storage molecule) so glucose is released into blood when blood levels are low

2) Produces digestion enzymes that break down carbohydrates, proteins, and nucleic acids. 3) Produces sodium bicarbonate, a base that neutralizes stomach acid to make it less acidic so these enzymes can be effective. Why does the stomach acid need to be neutralized in the intestines? Stomach acid can change the shape of proteins & enzymes are proteins. If the shape of the active site is changed, the intestinal enzymes won’t work correctly

Large Intestine: –Its main function is to reabsorb water from undigested material (it takes H 2 O out of CaCa)