Unit 7 - Digestion Flashcards
What four molecules do we consume?
Proteins, carbohydrates, fats, and nucleic acids
What is digestion defined as?
The breakdown of nutrients
What are the 7 components of our gastro-intestinal tract?
- Mouth
- Pharynx
- Esophagus
- Stomach
- Small Intestine
- Large Intestine
- Anus
What is the mouths main function?
Mechanical digestion (chewing)
What are the four kinds of teeth
Incisors, canines, premolars, and molars
What are the 3 layers that make up the teeth?
Outer layer of enamel, middle layer of dentin, and inner pulp containing nerves + blood vessels
What’s the only part of our body that decays while we are alive?
Our teeth
Saliva is produced by what three pairs of salivary glands?
- Parotid
- Sublingual
- Mandibular
What are the three components that make up saliva?
Water, mucus, and salivary amylase
What do the water and mucus in the saliva do?
Moisten the food
What is the role of salivary amylase in the saliva?
Breaks down carbohydrates into maltose
Differentiate between the soft and hard palates
Hard palate is the hard part right behind the teeth (roof of the mouth), everything from there to the uvula is the soft palate
What is the role of the uvula?
To keep food from entering the nasal cavity during swallowing
What is the pharynx?
The open space at the back of your mouth where oral cavity and esophagus meet
What is the role of the pharynx?
It’s the site of the swallowing reflex and also a passage for air between the nasal cavity and trachea
Where is the epiglottis and what is its role?
It’s found in the pharynx. It covers the entrance to the trachea during swallowing to prevent food from entering.
What is the ball of food that goes through our body referred to as?
A “bolus”
What is the esophagus?
The long tube through which the bolus moves down into the stomach
What is peristalsis?
The wave-like contractions of muscles pushing food through the digestive system
What is the lumen?
Inner surface of the esophagus, lined with a mucus membrane for lubrication
What is the opening from the esophagus into the stomach called?
The cardiac sphincter
Give 4 characteristics/functions of the stomach
- J-shaped organ
- Composed of 3 layers of smooth muscle
- Site of mechanical and chemical digestion
- Main function is storage
What is the mechanical digestion in the stomach called (the action of it)
Churning
What glands are in the inner mucosal lining of the stomach? What do they produce?
Gastric glands, they produce gastric juice
What are the two kinds of cells in gastric glands? What are their functions?
Parietal cells = release hydrochloride acid
Chief cells = release inactive enzyme Pepsinogen
What is Pepsinogen later converted into? What is its role? Why is it secreted as an inactive enzyme and not at active one?
Converted into pepsin when exposed to HCl, pepsin is a hydrolytic enzyme that breaks proteins into peptides. It’s secreted as an inactive enzyme because if it was active when created in the cell it would break down the cells own proteins
What are HCl’s functions in the stomach?
- Convert Pepsinogen to pepsin
- Lower stomach pH to 2.5-3.0
(this weakens food bonds and kills most bacteria)
What do mucosal glands do? Where are they found?
They produce mucus to protect the stomach from its own gastric juice. Found in the mucosal lining of the stomach
What are the secondary functions of the stomach?
- Partial digestion of protein
- Weakening of food bonds
- Destroying bacteria
Also plays a role in the absorption of water, alcohol, some drugs, and caffeine.
What is the mixture of food and gastric juice called?
Acid Chyme
What comes first, the small intestine or the large intestine?
The small intestine (the really long one)
What are the three sections of the small intestine?
Duodenum (first 25cm)
Jejunum
Ileum
Where does carbohydrate and protein duration start?
In the stomach (carbs in the mouth because of salivary amylase)
Where does fat and nucleic acid digestion start?
In the small intestine
How are simple nutrients absorbed in the small intestine?
Through the villi
What is the primary site of digestion?
The duodenum
What three things come into the duodenum (liquids/juices) and from where?
Bile from the gall bladder
Pancreatic Juice from the pancreas
Acid Chyme from the stomach
What is the liver’s role in digestion?
Produces bile which is stored in the gall bladder
What is bile made of?
Bile salts, and bile pigments (such as bilirubin and biliverdin produced from the breakdown of hemoglobin)
What is the function of bile? Is bile an enzyme?
To emulsify fats into fat micelles (NOT break them down)
No, bile is not an enzyme
What is the role of the pancreas in digestion?
Releases pancreatic juice into the duodenum
What 4 things is pancreatic juice made up of?
Sodium bicarbonate
Pancreatic amylase
Trypsin
Lipase
What is the role of the sodium bicarbonate in pancreatic juice?
Neutralizes acid chyme
What is the role of the pancreatic amylase in pancreatic juice?
Turns carbohydrates to maltose
What is the role of the trypsin in pancreatic juice?
Breaks down proteins into peptides
What is the role of the lipase in pancreatic juice?
Breaks fat micelles to fatty acids and glycerol
Where are the intestinal glands located and what is their role?
In the walls of the small intestine, they produce enzymes to complete the digestion of proteins, carbs, and nucleic acids
What three enzymes (among many others) are produced by the intestinal glands and what do they break down?
- Peptidases (peptides to amino acids)
- Maltase (maltose to glucose)
- Nuclease (nucleic acids to nucleotides)
Why does the small intestine have such a great surface area? What does greater surface area allow?
Because of the villi and microvilli
Allows for greater absorption of nutrient molecules
Why do enzymes produced by the intestinal glands remain attached to the microvilli of the intestinal wall?
So that upon contact the nutrient that is broken down can be immediately absorbed
Absorption is by ____ transport into the crypt of the villi
Active
Which nutrients enter the bloodstream and which enter the lymph system?
Blood stream = sugars, amino acids, and nucleotides
Lymph system = fatty acids and glycerol
What things form the hepatic portal vein?
The blood vessels leaving the villi of the intestines and stomach
What is the role of the hepatic portal vein?
To transport the products of digestion to the liver + connects 2 organ systems
Where does the small intestine meet the large intestine? What is in this spot?
Connects at a blind sac called the cecum which holds the appendix
What is the role of the large intestine?
Absorption of water and salt (creates solid feces)
Where is feces stored prior to expulsion via the anus?
The rectum
What lives (literally) in the large intestine? What is their role?
Symbiotic bacteria (mostly E. coli) which produce vitamins, amino acids, and gas, which are also absorbed
What three hormones are released upon presence of food in the mouth, stomach, and duodenum
Gastrin, Secretin, and Cholecystokinin (CCK)
Which glands release Gastrin and what does it cause the release of?
GASTRIN = released by glands on the stomach wall
when protein is present. Causes release of gastric juice.
Which glands release Secretin and what does it cause the release of?
SECRETIN = released by glands on the duodenum wall when acid is present. Causes the release of pancreatic juice.
Which glands release Cholecystokinin (CCK) and what does it cause the release of?
CCK = released by glands on the duodenum wall when fat is present. Causes the release of bile and pancreatic juice.
Is the secretion of bile, gastric and pancreatic juice controlled psychologically or hormonally?
Both
What are the 7 functions of the liver?
- Controls Blood Glucose
- Removes Toxins from blood
- Metabolizes alcohol
- Destroys old Red Blood Cells
• produces bile pigments in the process - Makes Blood Proteins
- Produces Bile
- Produces Urea
How does the liver maintain glucose levels? (details)
- maintains blood glucose levels at 0.01%
- stores glucose as glycogen after meals
- hydrolyzes glycogen to glucose between meals
- once glycogen reservoir is full, excess glucose is converted to fat and stored in adipose tissue
- glycogen reservoir can last up to 10 hours
What else can the liver convert into glucose? What is this process called? What happens in this process?
- liver can also convert amino acids to glucose through a process of deamination and gluconeogenesis
- in this process the amine is removed and converted to ammonia and subsequently urea
What is Jaundice?
- yellowish skin and eyes due to large amounts of bile pigments in the blood
- caused by gall stones, hepatitis
What is Cirrhosis?
liver becomes fatty and eventually covered by scar tissue
• caused by processing large amounts of alcohol
Where does most energy come from?
Glucose in the blood
Where is insulin produced? By what? What is its function?
Insulin is produced in the pancreas by the islets of langerhans . It causes cells to take in glucose.
When is insulin usually secreted?
After meals in response to large amounts of glucose in the bloodstream
What do the liver and pancreas convert glucose into?
Glycogen
What has the opposite effect of insulin and where is it produced? By what?
Glucagon has the opposite effect, drawing glucose out of the cell and increasing blood glucose levels (causes the liver and muscles to convert glycogen back to glucose)
Produced in the pancreas by the islets of langerhans
What are the two types of diabetes?
Type 1- juvenile onset
Type 2- maturity onset
What happens during type 1 diabetes?
- body unable to produce insulin
- unable to use glucose for energy, therefore uses protein and fat instead
- results in build-up of acids in the blood (acidosis) and respiratory distress
- can lead to coma and death
What happens during type 2 diabetes?
- body cells unable to detect insulin
- usually occurs in obese people of any age
