Presentation on theme: "The Digestive System Also Known As… You gotta know how this show is going to end...it’s awesome!!!"— Presentation transcript:
The Digestive System Also Known As… You gotta know how this show is going to end...it’s awesome!!!
Eaters Digest The job of the digestive system is to break down the food we eat into nutrients – the small molecules that our cells need to survive. Food is digested – cut up into smaller pieces – through both chemical and mechanical process. Mechanical digestion refers to the muscular action that we use to break down the food. Chemical digestion involves the use of chemicals, such as enzymes, to chemical breakdown the food.
What Goes In… Your digestive system is actually a muscular tube that has an opening at two different ends. One end is at the mouth or oral cavity. Do you know where the other end of this digestive tube is? If you guessed the anus, you’re right! This muscle in this tube can being longitudinal or circular. Longitudinal muscle travels down the length of the organ while circular muscle wraps itself around the organ. This tube forms the digestive tract or alimentary canal.
The Four Step Program The process of digestion has four steps: 1.Ingestion – The actual acquiring of food and the placement of it in your mouth. 2.Digestion – The breakdown of the food into nutrients. 3.Absorption – The absorbing of the nutrients into the bloodstream so they can be taken to the cells. 4.Elimination – The unused parts of food have to removed from the body.
Digestion – Step-By-Step! So you want to eat eh?...Lets see what really happens to your food. Oral Cavity Food enters the oral cavity or mouth and undergoes mechanical digestion thanks to the teeth and tongue. The teeth cut, tear and crush food into pieces that form a ball-like mass called the bolus. Your tongue works to re-position the food being chewed back onto the teeth so they can continue to physically grind it down. Chemicals such as saliva and mucous lubricate the food so that it does not get stuck in your throat.
The Teeth – Structure & Function The teeth are used for mechanical digestion. There are four types of teeth in your mouth. 1.Incisors – Sharp cutters at the front. 2.Canines – Pointed tearing teeth at side of front. 3.Premolars – Grinding teeth a little further back. 4.Molars – Large grinders found the furthest back.
Pharynx & Epiglottis Pharynx When food has been chewed well and is ready to be swallowed, it is pushed back into the pharynx. The pharynx is a tube found at the back of the throat that acts like a traffic intersection. The pharynx joins the nasal cavity, oral cavity, esophagus and trachea. A small flap of tissue called the epiglottis is found at the base of the pharynx near the tops of the trachea and esophagus and its job is to direct food into the esophagus and prevent choking. The epiglottis folds over the top of the trachea (wind pipe) when food or beverage is being consumed so they do not attempt to go down to the lungs.
Esophagus – Gateway to the Gut! So, the food has been successfully directed down the food pipe instead of the wind pipe – giddy up! The food pipe that extends from the pharynx down to the top of the stomach is called the esophagus. The esophagus is a tube of smooth muscle that is about one foot in length. Smooth muscle acts on its own and once you swallow – it pushes the food through the system automatically. This pushing of food through the digestive tract by rhythmic contraction of smooth muscle is know as peristalsis. (Part of Mechanical Digestion)
The Stomach – Acid Hot Tub The stomach is a “J”-shaped organ that can stretch to hold the food you eat. The stomach contains hydrochloric acid (HCl) and digestive enzymes that break food down via chemical digestion. The acid in the stomach is very strong. The stomach protects itself from its own acid using a thick mucous lining that is continually secreted from the cells that line the inner wall of the stomach. The acid and stomach contents are kept in the stomach by a pair of sphincters – muscular drawstrings. The top of the stomach has the lower esophageal sphincter (aka cardiac sphincter) and the bottom of the stomach has the pyloric sphincter. These sphincters keep the acid from damaging the esophagus at the top and the small intestine at the bottom. The muscular wall of the stomach also causes it to churn and move food about so it gets thoroughly soaked in the acid/enzyme mixture. This is mechanical digestion - peristalsis.
The Small Intestine The small intestine is a thin, muscular tube about 2.5cm in diameter but measures anywhere from 6-7m in length. It’s found in the abdominal cavity below the stomach. The small intestine has three sections – the duodenum, the jejunum and the ileum. Digestion is completed in the duodenum as additional enzymes are added to the food. After this, the process of absorption begins as the nutrients are absorbed through the wall of the small intestine.
The Villi The villi are small finger- like projections that line the inner wall of the small intestine. They greatly increase the surface area of the small intestine to maximize nutrient absorption. The villi have blood vessels in them that take in the nutrients and deliver them to the rest of the cells of the body.
Large Intestine, Rectum & Anus The large intestine is also known as the colon and it has the extra special job of reabsorbing water and mixing it with the unabsorbed material from food to make feces. The first section of the large intestine is the caecum – it connects to the ileum via the ileocecal valve. The large intestine has different sections – the caecum, ascending colon, transverse colon, descending colon and sigmoid colon. Feces are produced in the colon and stored in the rectum until it can be released. The anus is another sphincter that controls the movement of feces out of the body. The anal sphincter keeps you from pooping in your pants 24/7!