Digestive System Flashcards
Why do we need a digestive system?
Our bodies can’t use the nutrients we eat as they are but must transform them to allow them to do their job.
The role of the digestive system
Break down the food into molecules so that they are small enough to be absorbed by the body and to eliminate the undigested food from the body
What two parts make up the digestive system?
The digestive tract and the digestive glands
Digestive tract
The physical route that the food takes from the beginning to the end of its journey through the human body
Digestive glands
Produce chemical secretions that are needed to digest food as it travels along the digestive tract
Components of the digestive tract
Mouth Pharynx Esophagus Stomach Small intestine Large intestine
Components of the digestive glands
Sal vary glands Gastric glands Liver Pancreas Intestinal glands
What are the functions of the digestive system
Ingestion of food
Digestion of food
Absorption of food
Elimination of fecal matter
What is ingestion?
The action of introducing food or liquid into the digestive system
What 2 mechanism allow the progression of the food in the digestive system?
Deglutition and peristalsis
What is deglutition?
Swallowing the food
Peristalsis
Series of involuntary wave like muscle contacterions which move along the digestive tract
What happens when we swallow?
The epiglottis closes the trachea and the uvula moves backwards to close off the nasal cavity. Food can then travel to the esophagus without getting into the respiratory tract.
What is digestion?
The transformation of complex molecules into simpler molecules called nutrients that can be used by the body
What are the two types of transformations?
Mechanical and chemical
Mechanical transformation
Consists of physically breaking down food into smaller substances in preparation for subsequent chemical transformation
Involves chewing and churning
Chewing
Process of crushing and grinding food
Churning
Produced by muscle contractions, which mix food from secretions from the digestive glands. Takes place primarily in the stomach and small intestine
Chemical transformation
Break down complex molecules of food into simpler molecules. The facilitate absorption and subsequent use by the body
Protein molecule
Amino acids
Starch molecules
Glucose
Fat molecule
Fatty acids
Digestion ends at….
It ends at the small intestine when nutrients have been broken down to their molecular components and now pass through the lining of digestive tract and can be used by the body
What is absorption?
The passage of nutrients from the digestive tract to the blood or lymph
Where does most food absorption take place?
Small intestine
What are villi
Folds in the small intestine. They increase the surface are through which nutrients can be absorbed. They have blood and lymphatic vessels that the nutrients use to get into the rest of the body
What nutrients are absorbed in the small intestine?
Glucose Amino acid Fatty avid Glycerol and water (minute amounts) Vitamins (minute amounts) Minerals (minute amounts)
Elimination
Digestive residue then enters the large intestine contains very little nutrients
Arrives in the large intestine in liquid form
Water is slowly absorbed
Residue that reaches the rectum is usually solid has a little water left
From the rectum the feces is expelled through the anus
The oral cavity
Where mechanical and chemical digestion foods begin. Breaks down starch with saliva
Stomach
Primary role of the stomach is food storage. Allows to store large amounts of food because it stretches
Small intestine
Most of the digestion and absorption takes place there.
Large intestine
Divided into several section (cecum, colon, appendix, and rectum terminating in the anus)
Salivary glands
Secrete between 1 and 1.5L of saliva a day. Proteins and enzymes are found in saliva.
Saliva
Acts as a lubricant for mouth and food bolus. It limits the scratches in the oral cavity. It also contains antibacterial agents which limit the introduction of bacteria into the digestive tract
Gastric glands
Scattered throughout the internal surface of the stomach
Intestinal glands
Located at the bottom of the villi. There are about 50 million of these glands and they can secrete up to 2 L of intestinal juice in the small intestine
Liver
Role is mainly secretion of bile. Stored in the gallbladder
Pancreas
Secretes between 1.2 L in 1.5 L of pancreatic juice. Is mainly responsible for the secretion of two hormones: insulin and glucagon. These hormones are responsible for regulating the level of glucose in the blood
