Digestive System Flashcards
How is food digested?
Ingestion-eating food; Digestion-chemical and mechanical breakdown; Absorption- transport of nutrients into the circulatory system; Elimination- removal of undigested food.
What is the Digestive System?
The digestive tract is a series of hollow organs joined in a tube from the mouth to the anus. Food passes through it.
What are the Accessory Organs?
Liver, gall bladder, pancreas. Food doesn’t pass through these organs.
Mouth
Mechanical Digestion- Teeth bite off and chew food into a soft pulp easy to swallow.
Chemical Digestion- Chewing mixes food with saliva, from salivary glands around the mouth and face, to make it moist and easy to swallow.
Esophagus
The esophagus is a muscular tube. It takes food from the throat and pushes it down through the neck, and into the stomach. It moves food by waves of muscle contraction called peristalsis. The epiglottis prevents food from entering the trachea (windpipe) and getting into your lungs.
What is the esophageal sphincter?
Between the esophagus and the stomach, it is a
valve aka the cardiac sphincter. This prevents food from coming back into the esophagus from the stomach.
Stomach
Mechanical Digestion - The stomach has thick muscles in its wall. These ridges (called rugae) contract to mash the food into a watery soup called chyme.
Chemical Digestion - The stomach lining produces strong gastric juices (HCl, salts, enzymes, and mucus).
Why doesn’t the stomach digest itself?
The stomach does not digest itself because of mucus lining the stomach, and gastric juice is secreted only when food is present. The protein digesting enzyme (pepsin) is only active when HCl is present.
Where does the food go after the stomach?
The food passes out of the stomach through the pyloric sphincter (and into the small intestine).
Small Intestine
This part of the digestive tract is narrow, but very long - about 20 feet (7 metres)
Enzymes continue chemical reactions on the food.
It is made up of three sections: Duodenum, Jejunum, Ileum
What are Villi?
Small projections that increase the surface area for nutrient absorption. Microvilli, projections on the villi, increase the surface area even more.
The nutrients are broken down small enough to pass through the lining of the small intestine, and into the blood (diffusion).
Pancreas
Secretes 1L of pancreatic fluid each day into the small intestine. These are made up of enzymes that break down food and bicarbonate ions that maintain a healthy pH of about 8
Liver
The liver creates bile (a mixture of bile salts). The bile is a greenish yellow colour and is stored in the gallbladder until release into the small intestine.
Large Intestine
Useful substances that were not absorbed in the small intestine, such as water and body minerals, are absorbed through the walls of the large intestine, back into the blood.
What is done with the remains in the large intestine?
The remains are formed into brown, semi-solid feces, ready to be removed from the body. Stored in the rectum. Eliminated by the anus (through the anal sphincter). Peristalsis again helps with the removal of this waste through the intestines.
