The Human Digestive System Why do we have a digestive system? When you eat foods such as bread, meat, and vegetables, they are not in a form that the body can use Food and drink consumed must be broken down into smaller molecules so that they can be absorbed into the body Why do we need a Digestive System? Components of the Digestive System? Oral Cavity (mouth) Small Intestine Esophagus The Digestive Tract is a series of hollow organs joined in a long, twisted tube from the mouth to the anus Organs involved: Mouth Esophagus Stomach Liver Pancreas Small Intestine Large Intestine Rectum Components of the Digestive System? The entire length of the digestive tract is lined with epithelial tissue Contains lots of goblet cells which secrete mucus. The mucus does two things 1.Protects tract from digestive enzymes 2.Moves materials along the tube Digestive Enzymes Digestive Enzymes help to break food into smaller pieces so that it is easier to digest The Mouth Digestion begins in the oral cavity (mouth) where 2 types of digestion take place: 1)Mechanical Digestion 2)Chemical Digestion Mechanical Digestion Chewing breaks up large pieces of food into smaller ones Chemical Digestion The Human Body releases 1 1.5L of saliva per day from glands in your cheeks (salivary glands) Saliva converts Carbohydrates into simple sugars like Glucose Glucose Chemical Digestion Saliva also contains mucus and water which makes food easier to swallow Grab a ruler and have a look Esophagus Food enters the esophagus which is a narrow, muscular tube about 25 centimeters long Food is swallowed by voluntary action (you control) of the tongue Trachea Esophagus The Trachea (Wind Pipe) and Esophagus are connected Why does food not go into lungs? There is a small flap consisting of connective tissue which prevents food from entering the trachea when swallowing (Epiglottis) Esophagus The wall of the esophagus is made up of two layers of smooth muscles which push the food down into the stomach If a person were to swallow while being upside down you could see the muscles in action Demonstration 1)Gently place your hand over your throat and swallow -What do you feel? 2) Turn to someone next to you -Have your partner tilt their head up -Watch their neck as they swallow reverse roles Stomach The stomach acts as a storage place for food as well as a place of digestion It is also described as an elastic bag made of muscle which expands It can hold up to 4 L of food!! Stomach Chemical Digestion: -Stomach cells produce acid (HCl) which helps break down proteins -The stomach cells also secrete mucus to protect its lining from the acid - Sometimes this acid exits the stomach and enter the esophagus Stomach Mechanical Digestion: The muscles of the stomach wall contract and expand to churn food and move it towards the small intestine The growling sound you sometimes here is your stomach moving This is smooth muscle Bread in bag experiment: 1)Take 1 piece of bread per two students. Rip in half so each student has of a slice 2)Obtain a small sandwich bag from the front of the room 3)Tear your slice of bread into smaller pieces and place it into your sandwich bag (What does this represent?) 4)Your teacher will come around now and pour a small amount of juice into the bag 5)Close your bag and squish the bread with your fingers until all of the pieces are really small (What does this represent?) 6)Put all of the contents of the bag into the garbage (What does this represent?) Blood Small Intestine The small intestine further splits food into smaller pieces. Most of the nutrients we take in are absorbed in the small intestine Small Intestine Receives many digestive enzymes from the pancreas and liver to help break down food Moves food using smooth muscle cell contraction The lining of the intestine secretes protective mucus to protect it from the enzymes Is about 7 m (22 feet 6 inches) long, 2.5 cm (1 inch) in diameter and has a surface area of 250 square meters (2,700 square feet) the size of a tennis court! Called the large intestine because it has a much larger diameter than the small intestine Large Intestine Sometimes called the Colon Its function is to absorb water and vitamins from the remaining food Also stores the remains of the food that cannot be absorbed (wastes) before they are flushed from the body About 1.5 m (5 feet) long and 6.5 cm (2.5 inches) in Uranus Rectum The rectum acts as a temporary storage facility for feces before it is excreted from the body Accessory Organs The Liver, Pancreas, and Gall Bladder all help with the digestion by supplying digestive enzymes The Liver also produces bile which helps digest fats These substances are delivered into the Small Intestine Gall Bladder Liver Produces bile which is stored in the gall bladder Bile is then sent to the small intestine to break down fats Pancreas 1)Is involved in supplying enzymes required for digestion directly into the small intestine 2)Secretes a hormone called insulin directly into the blood stream Insulin causes most of the body's cells to _________ _________ Review and Revisit Name that Digestive System Organ 1) Liver 2) Esophagus 3) Stomach 4) Pancreas 5) Small Intestine 6) Large Intestine 7) Rectum The Human Digestive System Handout Revisited Complete the Digestive System Handout to the best of your ability without looking in any text or your notes Complete the bottom section using information from this PowerPoint Excellent Digestive System Interactive Activity In slideshow mode, please Click to visit