Biology - Digestive System
What is the pancreas' role? List all of the substances it produces and their functions.
It has 3 main roles Produce hormones that regulate blood sugar levels Produces enzymes that break down carbs, proteins, lipids, and nucleic acids It lastly produces bicarbonate-- a base that neutralizes the stomach acid so that enzymes can work. Acids in the stomach can change the shape and function of these enzymes and proteins. If the enzyme's shape changes, it won't be able to fit on the active site of the substrate, and won't function correctly.
What is the role of the liver in digestion?
Main function: process nutrients absorbed from small intestine Creates bile to be secreted into small intestine (to digest fat)
How does the gallbladder aid in digestion?
Main function: stores and concentrates bile before releasing it into the duodenum to help absorb and digest fats
What gets digested here and how?
Mainly proteins are digested by gastric juice The presence of pepsin (enzyme) in the gastric juice helps it digest proteins EX: Hamburger and Bun Bun, can easily be broken down w/o excessive gastric juice BUT the hamburger needs GREATER supplies of Gastric juice and pepsin to be broken down
Chemical Digestion
breaking down food into more simple nutrients, begins in mouth when saliva uses an enzyme (amylase) to break down carbs In STOMACH, chemicals made to break down food Occurs in the mouth and stomach
Mechanical Digestion
physical digestion, occurs in the mouth using teeth.
Elimination
process of expelling undigested food and waste from the body Ex: urination, defecation, and clearance
Pepsinogen
-HCl activates it and make Pepsin for the stomach
What enzymes are present in the small intestine and what do they digest?
-maltase - maltose -sucrase - sugar (sucrose) -lactase - lactose
What does the pancreas produce?
1. Digestive enzymes break down food 2. Insulin to lower glucose levels 3. Glucagon releases energy to raise glucose levels 4. Pancreatic polypeptide and somatostatin regulate cells that produce insulin and glucagon
What is the pharynx?
A cavity between the nose and the mouth that uses muscles to carry food from the mouth to the esophagus (helps you swallow).
What is the pH of the stomach?
1.5 - 3.5 pH (very acidic)
What is the pH of the stomach?
1.5-3.5 pH (very acidic)
3 functions of Large intestines & main function
3 functions of the large intestine - Mouth Esophogus Stomach Small intestine Large intestine - last part of digestive tract connected to rectum, probably not digesting because it is the end of the system Main function- Reabsorption of water, pulling water back to the front of the digestive system Formation and storage of fecies Has bacteria that gives us vitamin k for blood clotting NOT digesting (b/c by the time you get to the end you don't need to digest) Main function= reabsorption of water (water reabsorbed into blood vessel, to prevent it all from coming out of body) Bacterial infection is obvious cause as to why it won't reabsorb Polyps Celliac disease Lactose intolerance If you don't absorb enough water= diarrhea 2nd formation and storage of feces 3rd good bacteria lives in large intestine (SO important- break down stuff in their, provide vitamin K for bloodclotting) If bacteria isn't working (could be destroyed by taking too many antibiotics)--> vitamin K cant be utilized→ bloodclotting issues NOTE: water pouring into your digestive system in order to move things along!
pH of small intestine
8-11 basic
What is an ulcer? How do you get one?
A sore/hole that develops on the lining of the stomach, small intestine or esophagus (we will focus mainly on stomach ulcers) How do you get one? Ulcers are created when the protective mucus around the stomach becomes ineffective, and the stomach lining is directly exposed to strong digestive acid. (basically, the stomach begins to digest its own cells + damages the tissue)
What happens if mucus breaks?
Acid and pepsin will begin to eat away walls of stomach= peptic ulcer caused by a bacterial infection
Describe the processes of digestion in the stomach:
Churning action of stomach physically breaks down food (mechanical digestion) Stomach releases acids and enzymes (ex: pepsin) to break down food further (chemical digestion)
Describe the processes of digestion in the stomach:
Churning action of stomach physically breaks down food (mechanical digestion) Stomach releases acids and enzymes (ex: pepsin) to break down food further (chemical digestion) What happens next? The stomach releases food into small intestine ("in a controlled and regulated manner")
What is acid reflux?
Digestive disease in which the stomach acid (aka bile) harms the food pipe lining (place where stomach and esophagus meet)
What are the causes?
Digestive disease in which the stomach acid (aka bile) harms the food pipe lining (place where stomach and esophagus meet) What are the causes? Uncontrollable causes- hiatus hernia! hole in diaphragm allows the upper part of the stomach to enter the chest cavity Pregnancy! b/c extra pressure placed on internal organs (the 2 often lead to GERD- Gastroesophageal reflux disease) Lifestyle causes- Obesity Smoking (active or 2nd hand) Excessive dietary salt intake Lack of dietary fiber Lack of physical activity Meds- (for asthma, painkillers, sedatives, antidepressants etc.) alcohol/caffeine
What are the three parts to the small intestine and what are their functions?
Duodenum- breaks down food- chemical digestion w/ enzymes!! (connects to the stomach) Jejunum- absorb nutrients, using special cells called enterocytes, and sends them into the bloodstream (middle part) Ileum- absorb any nutrients not previously absorbed and sends them into the bloodstream
Why are the liver/gall bladder connected?
Gall bladder is a "closet"- holds bile! Emulsifier (breaks down fats) into smaller molecules MECHANICAL DIGESTION b/c it simply breaks it into smaller fats, not diff forms NOTE: (chemical digestion would be breaking starch into glucose→ diff form!!) Ex: soap emulsifies, gets grease off hands Liver makes bile!! So, liver hands bile to gallbladder
What is in gastric juice?
Gastric Juice consists of hydrochloric acid, pepsin, and mucus NOTE: function= partially digest food (primarily) + also get rid of "pathogenic microbes" (pathogens) that have entered through the mouth
What is chyme?
Highly acidic fluid made of gastric juices + partially digested food that passes from the stomach to the small intestine. Product of mechanical and chemical digestion Ex: throw up
Differences between mechanical and chemical digestion
Mechanical digestion is physically breaking down food into smaller pieces. Starts in the mouth as food is chewed. Continues in the stomach when the stomach churns and contracts to break down the food. Chemical digestion breaks down the food into simpler nutrients that the body needs. Chemical digestion also starts in the mouth when the saliva begins to break down food ingested. Chemical digestion continues in the stomach when the chemicals break down the food (into nutrients the cells need). Mechanical digestion breaks food down into small pieces, while chemical digestion chemically changes the food into a form that can be used by cells.
What are the 3 specific cells that line the stomach? What is their function?
Mucous Cells- secrete mucous to protect the stomach from its own digestive secretions. Chief Cells- release pepsinogen which is converted into the enzyme pepsin by the gastric acid. Parietal Cells- secrete hydrochloric acid.
Why doesn't pepsin destroy the stomach?
Mucus lining protects it!!! Mucus is made of lipids !! (Not proteins, so won't be broken down by pepsin)
Cells in stomach
Mucus- mucus Parietal- HCl (pH 1-3) Chief cells- pepsinogen
Autotroph
Organism that can capture energy from sunlight or chemicals and use it to produce its own food or chemicals and use it to produce its own food from inorganic compounds; also called a producer
Heterotroph
Organism that obtains energy from the foods it consumes and relies on consumption of other organisms for nutrition. Also called a consumer. Life started with heterotrophs.
Why and when would you take TUMS? What do they do?
People take TUMS to treat heartburn (aka acid reflux), an upset stomach and acid indigestion. (Used when digestive system isn't working properly and acid gets backed up from stomach into esophagus→ esophagus doesn't know what to do→ sets off nerve→ pain) TUMS are bases that neutralize the excess gastric acid in the esophagus and stomach.
Why do we have to activate pepsin?
Pepsin breaks down proteins. Most cells are made of proteins. If pepsin were active in cell, it would break down cell---> if we put in stomach-- doesn't break down cells
Absorption
Process by which one thing is absorbed by another; when a food's nutrients are taken into cells or tissues Ex: Soaking up milk with a paper towel Ex: Food after being broken down turns into nutrients and is absorbed by small intestine
Extracellular Digestion
Process in which food is broken down outside of cells
What enzyme is present in the mouth and where does it come from? What does it do?
Salivary amylase is the enzyme present in the mouth. It comes from the salivary glands in the mouth. The salivary amylase breaks the chemical bonds between sugar monomers and starches, making the food easier to chew and swallow.
What food gets digested in the mouth?
Starches
What food is digested in the mouth?
Starches and fats get digested
Three parts of the Small Intestine and Functions?
The Duodenum - First part and takes in chyme to help digest it The Jejunum - Middle part and helps absorb the bulk of the nutrients before going to the ileum The Ileum - Last part and absorbs mainly vitamin B12, other water soluble vitamins, bile salts, and nutrients that were not absorbed in the jejunum
What body parts does the digestive system use?
The digestive system includes the mouth, pharynx, stomach, small intestine and large intestine. Salivary glands, the pancreas and the liver help digestion to occur.
How does the small intestine increase absorption? Describe these structures. How do fats get absorbed?
The small intestine contains 2 structures to increase absorption: microvilli and villi Microvilli: tiny "hair-like projections" that line the epithelium cells of the small intestine and increase surface area for absorption Microscopic (can only be seen w/ a microscope) Give off a fuzzy appearance b/c there are SO many Called a "brush border" b/c looks like a paint brush Villi: little "finger-like projections" that stick out from the mucosal (mucus) lining in order to increase surface area and therefore increase nutrient absorption Each villus contains microvilli (it's almost as if the villi are the fingers, and the microvilli are hairs on those fingers) Both work to increase surface area in order to increase nutrient absorption!! (b/c w/ bigger surface area, more nutrients can be absorbed at once!!!!)
Why is the stomach so acidic?
The stomach is very acidic in order to kill HARMFUL bacteria during food ingestion The acid secreted by the gastric glands activates the enzyme called PEPSIN Pepsin is needed to digest proteins The acidity tells the pancreas to create various enzymes (and juices) to further digest and break down the food that is coming through the stomach and the rest of the body
What happens next?
The stomach releases food into small intestine ("in a controlled and regulated manner")
What is the environment of the stomach like?
The stomachs environment is VERY acidic Hydrochloric acid is the responsible for the acidity
What is the function of intestinal juice?
To enable lipase function Also contains hormones Digestive enzymes Mucus Helps to complete protein digestion
What is the pH of the mouth?
Usually, a healthy pH in the mouth is between 5.6 and 7.9.
What are the 3 main functions of the large intestine?
What are the 3 main functions? NOT digesting (b/c by the time you get to the end you don't need to digest) Main function= reabsorption of water (water reabsorbed into blood vessel, to prevent it all from coming out of body) Bacterial infection is obvious cause as to why it won't reabsorb Polyps Celiac disease Lactose intolerance 2nd function: formation and storage of feces 3rd function: good bacteria lives in large intestine (SO important- break down stuff in their, provide vitamin K for blood clotting)
What type of digestion occurs here?
no digestion occurs in the esophagus
What is an ulcer?
A sore that develops on the lining of the stomach, small intestine or esophagus (we will focus mainly on stomach ulcers) How do you get one? Ulcers are created when the protective mucus around the stomach becomes ineffective, and the stomach lining is directly exposed to strong digestive acid. (basically, the stomach begins to digest its own cells + damages the tissue)
Can intracellular digestion occur in organisms that HAVE digestive tracts?
Can intracellular digestion occur in organisms that HAVE digestive tracts? Intracellular digestion- when stuff is broken down IN a cell, done by lysosomes! Extracellular digestion- any time you digest something in a cavity (mouth, stomach), b/c NOT IN A CELL → then we absorb all of that stuff→ goes to blood! NOTE: entire digestive tract is lined w/ blood vessels... bleeding in feces is BAD!! (something disrupted blood vessels that line digestive system-- something wrong w/ whole system) Next, blood takes nutrients throughout body to every cell→ cells digest nutrients (intracellular)! So, complex organisms always do BOTH! First, we must break down extracellular-ly and then intracellularly... HOWEVER, single-celled creatures just do intracellular. NOTE: water pouring into your digestive system in order to move things along!
What happens in the small intestine?
Chyme gets pushed into the pyloric valve, it enters the duodenum = the first three parts of the small intestine. Where almost all digestive enzymes enter the intestine Chyme going into the duodenum, mixes with enzymes and digestive fluids from the pancreas, the liver, and the lining of the duodenum Small intestine is made of duodenum, the jejunum and the ileum = 6 meters long After chyme enters small intestine, it is a mixture of medium and small nutrient molecules Small intestine is specially adapted for the absorption of nutrients The small intestine is coated by fingerlike projections called villi which are covered by microvilli These help with the absorption of nutrients and once nutrients are absorbed the food is basically nutrient-free and ready to move on
What is the function of bile? Where does it come from?
Comes from the liver Important part of the absorption of fats in the digestive system (increases absorption) Mainly used to break down fats into small particles and help absorb fats inside of our guts critical for digestion and absorption of fats and fat-soluble vitamins in the small intestine
Why are these two connected?
Connected b/c liver creates the bile and then gives it to the gallbladder to store Gall bladder is a "closet"- holds bile! Emulsifier (breaks down fats) into smaller molecules MECHANICAL DIGESTION b/c it simply breaks it into smaller fats, not diff forms NOTE: (chemical digestion would be breaking starch into glucose→ diff form!!) Ex: soap emulsifies, gets grease off hands Liver makes bile!! So, liver hands bile to gallbladder
What is acid reflux? What are the causes?
Digestive disease in which the stomach acid (aka bile) harms the food pipe lining (place where stomach and esophagus meet) What are the causes? Uncontrollable causes- hiatus hernia! hole in diaphragm allows the upper part of the stomach to enter the chest cavity Pregnancy! b/c extra pressure placed on internal organs (the 2 often lead to GERD- Gastroesophageal reflux disease) Lifestyle causes- Obesity Smoking (active or 2nd hand) Excessive dietary salt intake Lack of dietary fiber Lack of physical activity Meds- (for asthma, painkillers, sedatives, antidepressants etc.) alcohol/caffiene
What cells line the stomach? What is their function?
EPITHELIAL CELLS Aka Surface Mucus Cells** AND.. The cells that line the stomach are called gastric glands The gastric glands are VERY important because they produce gastric juices They produce **protective mucus, Function: coat the stomach and help dilute enzymes
What cells line the stomach? What is their function?
EPITHELIAL CELLS Aka Surface Mucus Cells** OR....? The cells that line the stomach are called gastric glands The gastric glands are VERY important because they produce gastric juices They produce **protective mucus, Function: coat the stomach and help dilute enzymes
How do fats get absorbed?
Each villus has capillary beds (system of capillaries), including lacteals! Lacteals- lymphatic capillaries that absorb dietary fats!! Bile and digestive enzymes break down fats at first (lipase→ chemical digestion) Lacteals are the UNIQUE way fats are absorbed **although most nutrients pass directly through the small intestine walls and into the blood capillary beds, digested fats must first be "recombined" into the lining of the intestine and then absorbed into the lacteals!!
How does this affect the enzymes that end up their?
Enzymes exist at an "optimum pH" (aka their most favorable pH) Low pH of stomach can make enzymes less effective HOWEVER, this pH is necessary b/c the enzymes that digest food (like pepsin) have an optimal pH of 2, making the stomach's acidic environment well-suited for them Other effects: Low pH of stomach juices can cause ulcers→ b/c can eat through walls of small intestine/stomach (mucus cells prevent this) Low pH also kills bad microorganisms on foods consumed→ prevents illness
How does the pH affect the enzymes that end up there?
Enzymes exist at an "optimum pH" (aka their most favorable pH) Low pH of stomach can make enzymes less effective HOWEVER, this pH is necessary b/c the enzymes that digest food (like pepsin) have an optimal pH of 2, making the stomach's acidic environment well-suited for them MORE IMPORTANTLY: pH is very acidic and the HCl (acid made by perital cells) activates pepsinogen to create pepsin Other effects: Low pH of stomach juices can cause ulcers→ b/c can eat through walls of small intestine/stomach (mucus cells prevent this) Low pH also kills bad microorganisms on foods consumed→ prevents illness
Process of Digestion in the Mouth
Food is chewed into smaller pieces (mechanical digestion) Teeth tear and crush the moistened food into a fine paste until its ready to be swallowed Chewing begins the process of mechanical digestion As you chew, salivary glands produce digestive enzymes in your saliva (amylase) break down the food molecules into smaller ones In chemical digestion, large molecules are broken down into smaller food molecules Tongue has muscles that move food around to aid mechanical digestion Teeth: Teeth are in the bones of the jaw in the mouth. Teeth help cut, tear, and crush food into smaller fragments
What is in gastric juice?
Gastric Juice consists of hydrochloric acid, pepsin, rennin, and mucin Breaks down mainly proteins Made in the glands in the stomach NOTE: function= partially digest food (primarily) + also get rid of "pathogenic microbes" (pathogens) that have entered through the mouth
What would happen if the villi becomes damaged?
IF THE VILLI BECOME DAMAGED (CELIAC DISEASE) You can become VERY sick if the villi becomes damaged
What happens if these functions don't work correctly? (large intestine)
If #1 doesn't work→ diarrhea If fecal matter moves too slow (#2 failing)→ constipation If #3 doesn't work→ (bacteria could be destroyed by taking too many antibiotics)--> vitamin K can't be utilized→ blood clotting issues
Differences between intracellular and extacellular digestion
Intracellular digestion takes place INSIDE the cell, extracellular digestion takes place OUTSIDE the cell
Can intracellular digestion occur in organisms that HAVE digestive tracts?
Intracellular digestion- when stuff is broken down IN a cell, done by lysosomes! Extracellular digestion- any time you digest something in a cavity (mouth, stomach), b/c NOT IN A CELL → then we absorb all of that stuff→ goes to blood! NOTE: entire digestive tract is lined w/ blood vessels... bleeding in feces is BAD!! (something disrupted blood vessels that line digestive system-- something wrong w/ whole system) Next, blood takes nutrients throughout body to every cell→ cells digest nutrients (intracellular)! So, complex organisms always do BOTH! First, we must break down extracellular-ly and then intracellular-ly... HOWEVER, single-celled creatures just do intracellular.
What happens if you don't have a gall bladder?
Liver still makes bile, but gall bladder doesn't store it!! It takes liver longer to make it---> fats don't get broken down→ too large to get absorbed!! → fat stays in large intestine... slides out, anal leakage!!
Can you survive without a liver? A gallbladder?
Liver- NO, b/c produces bile, filters harmful toxins, helps blood clot (prevents fatal internal bleeding), makes essential proteins Gallbladder- yes, harder to digest fats due to inability to store bile (bile will trickle slowly into intestines, not fast enough to digest a fatty meal) Increased risk of developing: fatty liver, indigestion, fatty acid and fat soluble nutrient deficiency
What is the function of peristalsis in the small intestine?
Peristalsis propels food through small intestine b/c food must keep moving through to avoid a "traffic jam" (for info on how peristalsis works, refer to esophagus above)
Explain peristalsis.
Peristalsis- the process by which the muscles in the esophagus contract and relax, squeezing food into the stomach. The constriction and relaxation of certain muscles in the intestine (or another canal) that creates a wavelike movement pushing all the contents in the canal.
Intracellular Digestion
Process in which food is digested inside of the cells. Lysosomes (contain digestive enzymes) used to break down in cytoplasm Takes place in animals that do not have a digestive tract, so food items go directly to the cell for digestion.
The Mouth and Pharynx
Process of Digestion in the mouth Food is chewed into smaller pieces (mechanical digestion) Teeth tear and crush the moistened food into a fine paste until it's ready to be swallowed Chewing begins the process of mechanical digestion As you chew, salivary glands produce digestive enzymes in your saliva (amylase) break down the food molecules into smaller ones In chemical digestion, large molecules are broken down into smaller food molecules The tongue has muscles that move food around to aid mechanical digestion Teeth: Teeth are in the bones of the jaw in the mouth. Teeth help cut, tear, and crush food into smaller fragments Saliva: Liquid made in the mouth by salivary glands, contains enzyme used to aid chemical digestion
Ingestion
Process of consuming or taking in food or other substances by swallowing or absorbing it. Ex: eating food / taking something into your body
Process of Mechanical Digestion
Process: -during digestion stomach muscles contract to churn and mix stomach fluids and food, and makes chyme. -After 1-2 hours, the pyloric valve (in stomach and small intestine), opens and chymes flows into small intestine. Ex: Chewing food
What is the role of saliva?
Saliva allows consumed foods to pass through to the digestive system. It also contains enzymes that help break down food in chemical digestion.
What enzyme is present in the mouth and where does it come from? What does it do?
The enzyme present in the mouth is amylase Amylase: converts starch and glycogen into simple sugars Found in saliva Converts starch and glycogen into other simple sugars Comes from salivary glands
What is the role of the epiglottis?
The epiglottis is the part of the throat that covers the windpipe during the swallowing of food in order to protect the windpipe.
What is in pancreatic juice?
The pancreatic juice contains a bunch of different enzymes Including... trypsin, lipase, and amylase Helps neutralize the acidic gastric juice inside our stomachs
What is the environment of the stomach like? Why is it that way?
The stomachs environment is VERY acidic Hydrochloric acid is the responsible for the acidity Why is it that way? The stomach is very acidic in order to kill HARMFUL bacteria during food ingestion The acid in the stomach activates an enzyme called PEPSIN Pepsin is needed to digest proteins The acidity tells the pancreas to create various enzymes (and juices) to further digest and break down the food that is coming through the stomach and the rest of the body
Explain peristalsis? WHAT IS THE MAIN GOAL?
To get food into your stomach. Peristalsis is the reason that you can actually swallow things upside down. Smooth muscle tissue contracts creating a peristaltic wave, that produces a bolus Bolus- ball like structure of chewed food and saliva Peristaltic movement makes smooth muscles (circular?) relax Then.. the contraction behind the chewed material forces it to NOT move backward (BUT not FORWARD) Then longitudinal contraction pushes it forward (the role of the longitudinal muscle has not be certain yet) Longitudinal muscle layer - The esophagus is composed of an inner circular muscle and an outer longitudinal layer (going lengthwise not across)
can you swallow food upside down?
Yes, as long as you have a healthy esophagus Esophagus moves things into our stomachs Stuff will still move toward stomach even if you are upside down NOTE: swallowing is a voluntary action, while peristalsis is NOT
Can you swallow upside down?
Yes, the smooth muscles in the esophagus will push the food down independent of gravity. Through contractions of the muscles in the esophagus, this is called peristalsis.
