Unit 2- Chapter 3 Flashcards
Digestion system
What are the various stimulants that cause eating?
The Hypothalamus is responsible for prompting us to seek food due to various signals from nerve cells and chemicals in our bodies. The hypothalamus has feeding and satiety centers that help regulate our intake of food.
Hunger which is a nonspecific psychologic drive for food occurs due to various signals in our bodies.
Appetite is a specific psychological drive for food that occurs due to social and cultural desires. Such as wanting to have popcorn at the movies or cake at a birthday party.
What are the organs in the GI tract?
The mouth, esophagus, stomach, small intestine, large intestine, and anus.
What are the accessory organs in the GI tract?
Salivary glands in the mouth
Pancreas
Gallbladder
Liver
What digestion takes place in the mouth?
Mechanical breakdown of food also known as mastication.
Chemical digestion where the salivary glands produce salvia and mixes with the food to form bolus.
Saliva contains enzymes amylase to break down starch and lingual lipase to break down lipids.
What takes place before digestion even starts?
Cephalic phase, which helps prepare the GI tract for digestion. It is started due to our senses such as smelling food, thinking about food, or tasting food.
Where does the bolus go after it gets swallowed?
The bolus is moved into the esophagus due to peristalsis and reaches the lower esophageal sphincter which connects to the stomach.
What can happen if the lower esophageal sphincter does not work properly?
If the LES fails to close after the food reaches the stomach, then the person can develop GERD or acid reflex. This can cause the feeling of heartburn or feeling like the food is going to come back up.
Digestion in the stomach
Once food reaches the stomach, the organ will start churning the food and producing gastric juices.
The mixing of the churned food with the gastric juices produces what is called CHYME.
The job of the stomach is to store chyme until it is ready to reach the small intestine.
Partial digestion and absorption takes place here.
What are the two types of cells that the gastric glands are lined with?
parietal cells and chief cells
What does the parietal cells secrete?
hydrochloric acid
this acid helps kill any harmful bacteria that may be present from the food as well as denature and break down proteins for digestion.
intrinsic factor which helps in the absorption of vitamin b12
What does the chief cells secrete?
Pepsinogen
hydrochloric acid turns pepsinogen into the active form pepsin which will start the digestion of proteins.
Gastric Lipase
an enzyme active in lipid digestion
only partial digestion of lipids until they reach the small intestine.
What protects the stomach from the acidity of the gastric juice?
Mucous cells line the stomach to help protect from gastritis or an ulcer due to acidic nature. Other cells also secrete bicarbonate which helps neutralize the acids in the stomach.
What is absorbed in the stomach?
Most absorption occurs in the small intestine, but the stomach can absorb some substances through the stomach lining and into the blood. These can include water, fluoride, some lipids, some lipid soluble drugs like aspirin and alcohol.
What is the capacity of the stomach and how long does chyme remain in there before being released into the small intestine?
The capacity of the stomach is about 1 gallon.
Chyme will still in the stomach for about 2 hours before being periodically released into the duodenum.
What sphincter connects the stomach to the small intestine which allows the chyme to pass through?
pyloric sphincter
Where does most digestion and absorption take place?
The small intestine
The longest portion of the GI tract.
What are the three sections of the small intestine?
- Duodenum
- Jejunum
- Ileum (last portion)
What are the accessory organs of the small intestine?
Gallbladder
Pancreas
Liver
What is the accessory organ of the mouth?
Salivary gland
What is the gallbladder’s main purpose in digestion?
The gallbladder is responsible for storing bile made by the liver. Bile emulsifies lipids in the small intestine. The gallbladder helps aid in the digestion of fats.
What does the pancreas do in digestion?
- Manufactures, stores, and secretes digestive enzymes to catalyze the digestion of carbohydrates, lipids, and proteins.
- Manufactures insulin and glucagon. Which are responsible for regulating hunger and satiety. As well as regulating the amount of glucose in the blood.
- Secretes bicarbonate into the duodenum. Neutralizes acidic chyme in the small intestine.
What does the liver do in digestion?
The liver is the largest digestive organ in the body and also is considered a gland.
Cleans toxins (harmful substances) out of the blood.
Gets rid of old red blood cells.
Makes bile, a fluid that helps the body digest (break down) food.
Metabolizes proteins, carbohydrates and fats so your body can use them.
Produces substances to help blood clot.
Regulates the amount of blood in the body.
Stores glycogen (an energy source) and vitamins to be used by the body later.
Three structural features of the small intestine?
1.) circular folds
2.) villi
3.) microvilli
Circular folds
heavy folds within the small intestine that result in increased surface area therefore allowing for better absorption.
Villi
small fingerlike projections within the circular folds.
the constant movement of the villi allow them to encounter and trap nutrient molecules.
Enterocytes
Specialized absorptive cells in the villi of the small intestine.
What is inside each Villus?
Capillaries and Lacteal.
The capillaries absorb water soluble nutrients into the bloodstream. Whereas the lacteal absorbs fat-soluble nutrients into lymph.
Lacteal
A small lymphatic vessel located inside the villi of the small intestine.
What does each enterocyte of each villus have?
Microvilli also known as brush border. Which is tiny brush like projections that help increase absorption.
what is brush border?
The microvilli of the small intestinal mucosa, which tremendously increase its absorptive capacity.
What are the four types of absorption in the small intestine?
Passive diffusion
Facilitated diffusion.
Active diffusion
Endocytosis
Passive diffusion
Nutrients cross into the enterocytes without the use of a carrier protein or requirement of energy. Moves from a high to low concentration gradient.
Ex: lipids, water, vitamin c
Facilitated diffusion.
Nutrients cross into the enterocytes with the help of a carrier protein but do not need energy. Moves from a high to low concentration gradient. Will not move without the carrier protein.
Ex: Fructose
Active Transport
Energy and a carrier protein are required to move nutrients against the concentration gradient. Moves from a low to high concentration gradient.
Requires the use of ATP (adenosine triphosphate)
Ex: Glucose, amino acids, certain minerals, and vitamin c).
Endocytosis
A transport process in which nutrients are engulfed by the cell membrane and are released into the cell interior (also called pinocytosis).
Ex: some proteins including the antibodies in breast milk are absorbed this way.
What are the two nutrients that transport nutrients and wastes
The blood and the lymphatic system
What are blood and the lymphatic system responsible for?
Blood travels through the cardiovascular system to transport nutrients and fluids and to pick up waste products.
Lymph travels through the lymphatic system and transports most lipids and fat-soluble vitamins.
How Does the Neuromuscular System Support the Gastrointestinal System?
Its two components, nerves and muscles, partner to coordinate and regulate the digestion and absorption of food and the elimination of waste products.
segmentation
Rhythmic contraction of the circular muscles of the small intestine, which squeezes chyme, mixes it, and enhances the digestion and absorption of nutrients from the chyme.