Digestive System
extracellular digestion happens....
extracellular digestion happens outside of cells.
The small intestine uses two ways to protect itself from the highly acidic chyme....
1. Goblet Cells Secretes mucus to protect the epithelial lining. 2. Neutralization -The small intestine produces secretin (a hormone) in response to the entry of chyme from stomach. -Secretin stimulates the pancreas to secrete bicarbonate ions (HCO₃⁻) into the duodenum via the pancreatic duct. -Bicarbonate is basic, and it neutralizes the acidic gastric juice that just entered the small intestine
Large Intestine Function 1...
1. Water absorption - The large intestine completes the water absorption process that began in the small intestine Note: the small intestine absorbs about 95% of the water we ingest -If too much water is absorbed → constipation -If too little water is absorbed → diarrhea
Large Intestine Function 2...
2. Mineral absorption -Some salts are absorbed together with the water e.g. sodium chloride
Large Intestine Function 3...
3. Vitamin production and absorption -The large intestine contains a rich bacteria community that live in harmony -The bacteria produce Vitamin B and Vitamin K which are then absorbed into our body. -Some of them are also responsible for metabolizing bile acid, and fermenting fiber To metabolize something means to turn food, minerals, etc. in the body into new cells, energy and waste products by means of chemical processes This is a mutualistic relationship - the bacteria receive nutrients from our digestive system to consume, and they produce vitamins for our benefit
A "vestigial structure" or "vestigial organ" is....
A "vestigial structure" or "vestigial organ" is an anatomical feature or behavior that no longer seems to have a purpose in the current form of an organism of the given species. Often, these vestigial structures were organs that performed some important function in the organism at one point in the past.
A glycoprotein called _________is also present that protects the lining of the mouth from abrasions, and lubricates the food so we can swallow it easy.
A glycoprotein called mucin is also present that protects the lining of the mouth from abrasions, and lubricates the food so we can swallow it easy.
A homodont's....
A homodont's teeth in contrast are all the same. Most reptiles, fish, and amiphibians are homodonts.
A layer of connective tissue called ____________ surrounds the liver.
A layer of connective tissue called Glisson's capsule surrounds the liver.
A portal triad is....
A portal triad includes.. 1- Portal Vein 2- Hepatic Artery 3- Bile Duct
About 2 liters of Pancreatic juice is made per day. Pancreatic juice contains....
About 2 liters of Pancreatic juice is made per day. Pancreatic juice contains.... 1. HCO3- 2. Proteases (trypsin, chymotrypsin, procarboxypeptidase) 3. Amylase 4. Lipase 5. Nuceases (digests DNA and RNA) 6. Elastase
___________ released by the parasympathetic fibers from the vagis nerve stimulates _______________ contraction
Acetycholine released by the parasympathetic fibers from the vagus nerve which stimulates gall bladder contraction.
After the cecum, digested food passes through the _________ where water absorption is completed. This gradually hardens the feces until it is stored in the __________and eventually expelled through the ___________.
After the cecum, digested food passes through the colon where water absorption is completed. This gradually hardens the feces until it is stored in the rectum and eventually expelled through the anus.
An ulcer is.....
An ulcer is an open sore on an extrnal or internal surface of the body, caused by a break in the skin or mucous membrane that fails to heal. It is a damage to the epithelial layer. Substances such as asprin, and even micro-organisms like Helicobacter Pylori can lead to ulceration. Helicobacter Pylori is a Gram-negative bacterium usually found in the stomach.
As food enters the mouth, both mechanical and chemical digestion take place.....
As food enters the mouth, both mechanical and chemical digestion take place. Chewing food physically breaks it down. This is mechanical digestion, as we are mechanically breaking down large food particles into smaller ones. Saliva contains an enzyme, salivary amylase, which will begin chemical digestion of carbohydrates in the mouth
At the bottom of the crypts of Lieberkuhn are _________ cells which.....
At the bottom of the crypts of Lieberkuhn are Paneth Cells. Paneth cells make lysozyme, contributing to maintenance of the GI bacteria by helping destroy micro-organisms.
Bile is...
Bile is a digestive juice that is secreted by the liver and stored in the gallbladder; it aids in the digestion of fats. Bile is a emulsifier of lipids Bile is not a enzyme Bile contains cholesterol, bile salts, bilirubin (pigment), phospholipids, water and even IgA.
Liver Function 1. Bile Production
Bile is produced by the liver and stored in the gallbladder Production of bile → stored in gallbladder → secreted into duodenum CCK Stimulates the gallbladder to release bile into the duodenum. -Bile is a digestive juice that is secreted by the liver and stored in the gallbladder; it aids in the digestion of fats.
Blood Capillaries and Lymphatic Capillaries Abosrb Difference Nutrients....
Blood Capillaries and Lymphatic Capillaries Abosrb Difference Nutrients Within the structure of a villus, there are blood capillaries and a lymphatic capillary known as lacteal. They are both responsible for absorption of different nutrients. Glucose + amino acid → absorbed into capillaries Fatty acid + glycerol → absorbed into lacteal
Peptic Ulcers...
But even with ample protection, the stomach can still get peptic ulcers, which is an open sore created on the stomach epithelium by acid corrosion.
Carboxypeptidase .....
Carboxypeptidase is an enzyme synthesized in the pancreas and secreted into the small intestine. This enzyme hydrolyzes the first peptide or amide bond at the carboxyl or C-terminal end of proteins and peptides.
Cleavage is one of the main ways to "activate" an enzyme....
Cleavage Cleavage is one of the main ways to "activate" an enzyme. Removal of these 44 amino acids allows for the needed conformational change to "activate" the enzyme. Both HCI and pepsin therefore are involved in this postive feedback.
Ligaments
Connect bone to bone BBL
Crypts also known as "Crypts of Lieberkuhn" are....
Crypts are like reverse villi - rather than projections, they are invaginations in the wall of the small intestine. The crypts contain cells that secrete enzymes and cells that produces epithelial cells. The crypts are actually glands. These crypts, "crypts of Lieberkuhn" contain goblet cells (mucus producing), enteroendocrine cells (hormone making), and regenerative cells.
Digestion can be divided into...
Digestion can be divided into intracellular and extracellular digestion.
Cholecystokinin (CCK) is...
Digestion in the small intestine not only involves enzymes from the small intestine itself, but also other accessory organs like the pancreas, liver, and gallbladder. As the small intestine detects proteins and fats coming in, cells in the lining of the duodenum release a hormone cholecystokinin (CCK), the signal calling out for help. This hormone lets the accessory glands know it's time to act.
Enterokinase/Enteropeptidase is made by ____________ of the duodenum....
Enterkinase/enteropeptidase is made by the Brunner glands of the duodenum.
Enterocytes are....
Enterocytes are the absorptive cells that make up the villi, and are lined with microvilli.
Large Intestine...
Finally, the digested food reaches the large intestine. Let's first take a look at the structure of the large intestine: Large Intestine has 3 main functions: 1. Water Absorption 2. Mineral Absorption 3. Vitamin Production and Absorption
Bolus...
Food is shaped into a ball called a bolus and pushed to the back of the throat called the pharynx.
Food is then moved by_________ from.....
Food is then moved by peristalsis, from the duodenum to the jejunum and ileum where nutrients are absorbed.
Jejunum is...
From the duodenum, we move the chyme to the jejunum. Villi are also found here. Absorption of nutrients continue. The villi of the jejunum are longer than these found in the duodenum. Similar to the duodenum, Paneth cells are found within the crypts of Lieberkuhn. The enzymes that were released into the duodenum (pancreatic lipase, pancreatic amylase, pancreatic protease) are still active in the jejunum. From the jejunum we move to the ileum...
Hepatic artery...
Hepatic artery carries deoxygenated blood to the liver
Hepatic portal Vein...
Hepatic portal vein or just poral vein for short brings blood to the liver from the villi
Hepatic vein...
Hepatic vein transports deoxygenated bloo away from the liver to the interior vena cava
Humans are heterodonts....
Humans are heterodonts, in that they have specialized teeth for different actions. Heterodonts have more than a single tooth morphology.
Peristaltic rush is....
If the intestinal mucosa becomes irritated by toxic substances, swift peristaltic contraction called the peristaltic rush can occur. Normal peristaltic time and mechanism is disturbed, and strong contractions can propel the chyme within minutes for elimination as diarrhea.
If you vomit.....
If you vomit, the cardiac sphincter valve relaxes itself enough to cause a backwards flow of vomitus. Stomach acid can cause damage to the esophagus and even lead to cancer.
The colon is...
Is the start of the large intestine It stores wastes Absorbs water Produces mucus that lubricatrs the intestinal surface The colon is divided into six regions: 1) cecum 2) Ascending colon 3) Transverse Colon 4) Descending colon 5) Sigmoid colon 6) Rectum No villi are present!!
The role of the common bile duct is.....
Its physiological role is to carry bile from the gallbladder and empty it into the upper part of the small intestine (the duodenum). The liver produces bile and sends it to the gallbladder for storage and concentration Bile is secreted from the gallbladder into the small intestine to emulsify fats — breaking down fats into smaller fat droplets that are easier to digest Remember: bile is NOT an enzyme, emulsification is a type of mechanical digestion - not enzymatic breakdown
Mucous cells in the stomach....
Mucous Cells Since the stomach is always under an acidic environment, there is a type of cell that functions to protect the stomach lining from the corrosive acid: mucous cells, which secrete mucus to lubricate and protect the stomach lining.
The ________ is the sphincter that controls food entering the stomach, the __________ is the sphincter that controls foods exiting the stomach.
Note, the cardiac sphincter is the sphincter that controls food entering the stomach, pyloric sphincter is the sphincter that controls foods exiting the stomach.
One or more roots are embedded in a .........
One or more roots are embedded in a gum socket.
Pseudopods is....
Pseudopods is a temporary outgrowth used by some microorganisms as an organ of feeding or locomotion.
Pyloric Sphincter....
Pyloric Sphincter — Controls Food Exiting the Stomach Eventually, the acidic, semi-digested food mixture, also known as chyme, leaves the stomach through the pyloric sphincter and enters the small intestine
Role of the gallbladder....
Role of the gallbladder The liver produces bile and sends it to the gallbladder for storage and concentration Bile is secreted from the gallbladder into the small intestine to emulsify fats — breaking down fats into smaller fat droplets that are easier to digest Remember: bile is NOT an enzyme, emulsification is a type of mechanical digestion - not enzymatic breakdown
Some effects of Cholecystokinin (CCK) include:
Some effects of Cholecystokinin (CCK) include: a. Slows down gastric emptying (inhibits the transfer of stomach contents to the small intestine) -It tells the stomach: "hey stomach, give me a sec!" -This gives the small intestine more time to digest and absorb what has entered. b. Stimulates the pancreas to release its digestive enzymes into the duodenum through the pancreatic duct. c. Stimulates the gallbladder to release bile into the duodenum through the Common Bile Duct. -Bile is a digestive juice that is secreted by the liver and stored in the gallbladder; it aids in the digestion of fats.
When we swallow, there is a structure called the epiglottis that.....
Swallowing is tricky business, because we don't want food to enter the airways. The epiglottis is a flap of cartilage that prevents food from entering the trachea. When we swallow, there is a structure called the epiglottis that blocks the opening to the trachea, this is to ensure that solids and liquids can only enter the esophagus. However, sometimes the epiglottis doesn't close quick enough while we eat and talk at the same time, and this leads to choking as our body tries to expel the foreign material that just enetered the trachea.
The Liver...
The Liver can regenerate. This is fundamental response to injruy. Hepatocytes (liver cells) begin to divide in response to toxic substances. This is called compensatory hyperplasia. The hepatocytes live about 150 days. New cells are made until the original tissue size is restored to normal.
Kuppfer cells in the liver...
The blood from the villi entered the hepatic poral vein. Blood from this area may harbour pathogenic organisms. The Kupffer cells phagocytize 99% of the pathogens, along with destroying defunct red blood cells.
Esophageal Mucosa is....
The esophagus is a muscular tube that will transport food from the mouth to the stomach. Glands in the esophagus secrete mucus which facilitate the transport of food. The esophageal mucosa is composed of stratified squamous epithelium.
The small intestine connects into a pouch called the....
The small intestine connects into a pouch called the cecum — an important structure for water and mineral absorption. The cecum has a small finger-like projection called the appendix, which has negligible immune functions in human adults. The appendix likely used to have a function, though that is no longer the case. For most people, it is a silent vestigial structure (borrowing terms from our evolution chapter). But when it gets inflamed (appendicitis), it becomes a painful problem, and is removed surgically.
The small intestine is divided into....
The small intestine is divided into the duodenum (first part), jejunum (second part) and ileum (last part). Mnemonic: I think of a music DJ named Eye (I) to remember the order of duodenum, jejunum, ileum.
The tongue has........
The tongue has touch and pressure receptors, in addition to taste buds along its surface.
Vasoactive Intestinal Peptide (VIP) is a hormone made by the duodenum which......
Vasoactive Intestinal Peptide (VIP) increases peristalsis, which are recurring waves of contraction and relaxation in the smooth muscles lining the GI tract that push food along. VIP is also involved with stimulating the elimination of ions and water by the GI tract.
The pancreatic duct functions to....
When food enters the stomach, these pancreatic juices are released into a system of ducts that culminate in the main pancreatic duct. The pancreatic duct joins the common bile duct to form the ampulla of Vater which is located at the first portion of the small intestine, called the duodenum.
When we swallow, food is moved to the back of the oral cavity, where we reach an area called the ___________
When we swallow, food is moved to the back of the oral cavity, where we reach an area called the pharynx.
Pepsinogen is a zymogen which means it will be activated into pepsin (the active form) when immersed in the acid of the stomach. Why do we need this extra step of activation?
You may ask, why do we need the extra step of activation? Why can't the active enzyme be secreted directly? This extra little step is actually extremely crucial because pepsin is a digestive enzyme that digests proteins, and proteins are found everywhere inside a cell. It is important for the enzyme-producing cell not to digest itself. Therefore, it is important for enzymes which digest proteins (like pepsin, trypsin, and chymotrypsin) to be inactive while in the cell that produces them. Hence, they are produced and stored in the cell as zymogens, and only activated when they enter the extracellular gastrointestinal lumen where they are meant to function, and begin digesting.
procarboxypeptidase
becomes carboxypeptidase which hydrolyzes the terminal amino acid from the carboxyl end of small peptides
intracellular digestion happens...
intracellular digestion happens within the cells,
When does absorption occur?
no absorption of nutrients has occurred up until the small intestine. The mouth, pharynx, esophagus, and stomach were all used for digestion and movement of food - no absorption occurs here. Absorption first occurs in the small intestine, specifically the Jejunum and ileum
pH of stomach is....
pH of Stomach is 1.5 The pH of the stomach is 1.5. This is a very low pH that will do two main things: 1. Destroy pathogens (like bacteria) 2. Break down proteins - protease called pepsin is present The inactive form of pepsin is called pepsinogen. It is a proenzyme or zymogen that needs to be activated. Pepsinogen is released by the chief cells. Gastric juice made of HCL is made by parietal cells. Once made, pepsin can also convert inactive pepsinogen to more pepsin.
saliva is also known as....
saliva is also known as ptyalin
After Trypsinogen is converted to its' activated form called trypsin by enteropeptidase, Trypsin can now activate other zymogens by___________...
After Trypsinogen is converted to its' activated form called trypsin by enteropeptidase, Trypsin can now activate other zymogens by proteolytic cleavages. This is a cascade, as is seen often when enzymes are activated by what is called covalent modification.
Liver Function 3: Glucose Metabolism
Another important function of the liver is maintenance of the blood glucose level. It achieves this through: a. Glycogenesis: -Words ending in -genesis means to create, hence glycogenesis = create glycogen. -After eating, excess glucose we've consumed that isn't immediately needed is converted into glycogen that is stored in the liver. b. Glycogenolysis: -Words ending in -lysis means to break, hence glycogenolysis = break down glycogen. -Between meals, when our body needs energy, the liver breaks down storage glycogen back into glucose. c. Gluconeogenesis: -Words containing -neo- means new, hence gluconeogenesis = create new glucose. -When the glycogen storage is depleted and our body requires even more energy: liver converts glycerol and amino acids into glucose.
_________ is along with G cells is almost made by the glands in the stomach pylorus.
Believe it or not but lysozyme is also made by glands in the stomach pylorus.
Chymotrypsin ....
Chymotrypsin is an enzyme that is used in the small intestine to break down proteins into individual amino acids.
cirrhosis of the liver is...
Cirrhosis is a consequnce of a sustained injruy to hepatocytes. Drugs, alcohol, even the hepatitis virus cause injury fibrous tissue replaces the normal hepatic archetecture. this is very common, but not restricted to alcholics.
What is digestion?
Digestion refers to the process of breaking down large food (like fries) into smaller substances (fries → glucose + fat) that can be absorbed and used by the body.
Elastase functions too...
Elastase is an enzyme made by special tissue in the pancreas, an organ in your upper abdomen. Elastase helps break down fats, proteins, and carbohydrates after you eat. It's a key part of your digestive process. In a healthy pancreas, elastase will be passed in the stool.
All thanks to the Stomach Acid...
Even though the stomach acid can cause troubles at times, it is thanks to the acid that we are able to kill bacteria from food, denature proteins (recall extreme pH can denature proteins!), and create a favorable environment for pepsin to function. The optimal pH for pepsin to demonstrate maximum activity is about 2.
Gastric Intrinsic Factor is......
Gastric Intrinsic Factor: It is a glycoprotein produced by the parietal cells of the stomach. It is necessary for the absorption of vitamin B-12.
Gastrin is made by.....
Gastrin is made by G cells of the Duodenum in the small intestine and the cells in the Stomach Pylorus
Hepatocyte is...
Hepatocyte are liver cells. They hepatocyte is responsible for converting lipids and amino acids into glucose. This process, is known as gluconeogenesis. Gluconeogenesis nd deamination will occur in the hepatocyte,
In adults the permanent teeth number is .......
In adults the permanent teeth number is 32
Ileum...
In the ileum, amino acids, bile salts, B-12 absorption occurs. Peyer's patches are here! Ther eis no clear demarcation between jejunum and ileum; they merge gradually. The ileum is seperated from the first part of the large intestine by the ileocecal valve.
Chyme...
In the stomach, ingested food gets processed and formed into a thick acidic fluid called chyme. Chyme is a combination of digestive juice and ingested food!
Key liver functions...
Key liver functions 1. Digestive Production of bile → stored in gallbladder → secreted into duodenum 2. Blood Blood storage Blood filtration Blood detoxification Removal of old RBCs → bilirubin from hemoglobin → bile 3. Glucose Metabolism Glycogenesis Glycogenolysis Gluconeogenesis 4. Protein Metabolism -Synthesizing plasma proteins e.g. albumin, clotting factors -Ammonia → urea -Synthesizing non-essential amino acids
Peyer's Patches are....
Peyer's Patches: an aggregation of lymphoid tissue is noted in the ileum wall Peyer's Patches monitor intestinal bacteria and prevents the growth of pathogenic bacteria. They look like round balls of lymphatic tissue. Peyer's Patches contain the usual crew: a) Macrophages b) Dendritic cells c) B-Lymphocytes and T-Lymphocytes
Liver Function 4: Protein Metabolism
Protein metabolism denotes the various biochemical processes responsible for the synthesis of proteins and amino acids. The liver plays a key role in protein metabolism and detoxification. This is why patients who suffer from liver problems (e.g. liver cirrhosis- which is a chronic disease interfering with the normal functioning of the liver; the major cause is chronic alcoholism) cannot eat a protein-rich diet, otherwise conditions such as ammonia poisoning may arise. Here is how the liver metabolizes proteins: a. Synthesizing plasma proteins from absorbed amino acids -Blood proteins, also termed plasma proteins, are proteins present in blood plasma. They serve many different functions, including transport of lipids, hormones, vitamins and minerals in activity and functioning of the immune system. -Albumin is a major plasma protein that is made almost exclusively by the liver. -Albumin is a protein made by your liver. Albumin helps keep fluid in your bloodstream so it doesn't leak into other tissues. It is also carries various substances throughout your body, including hormones, vitamins, and enzymes. Low albumin levels can indicate a problem with your liver or kidneys. -Blood clotting factors are also produced by the liver b. Synthesizing non-essential amino acids -It's important to note that non-essential amino acids does not mean that we don't need them. They are called non-essential because our body can make them, hence they are not essential from the diet. c. Converts dangerous ammonia to a safer urea for excretion -Protein metabolism tends to lead to a build-up of ammonia in the body. -A healthy liver will convert ammonia to urea (much less toxic) to be excreted from the kidneys.
Pathway through large intestine...
Structure of large intestine Cecum → Colon → Rectum → Anus Cecum: a Little pouch that is important for water and mineral absorption Appendix: The cecum has a small finger-like projection called the apendix. The appendix has very neglible immune functions in human adults. The appendix likely used to have a function, through that is no longer the case. For most people it is a silent vestigal structure. A vestigal structure is an anatomical feature or behavior that no longer seems to have a purpose in the current form of a given species. Often these vestigal structures were organs that performed some important function in the organism at one point in the past. When the appendix gets inflammed, called appendicities, it becomes a painful problem that gets surgically removed. Colon: After the cecum, digested food is passed into the colon where water absorption is completed. The colon generally hardens the feces. Rectum: The hardened feces is stored in the rectum Anus: Eventually the hardened veces stored from the rectum is expelled through the anus as waste
The hepatic Portal Vein...
The hepatic portal vein is a blood vessel that carries blood from the gastrointestinal tract, gallbladder, pancreas and spleen to the liver. This blood contains nutrients and toxins extracted from digested contents. 'Hepatic' means of or relating to the liver, therefore the hepatic portal vein is a blood vessel that sends nutrient-rich blood from the gastrointestinal tract and spleen to the liver, but also delivers toxins to the liver that will be chemically modified in the proces of detoxication.
ileocecal valve is.....
The ileum is seperated from the first part of the large intestine by the ileocecal valve. Valve at the junction of the small intestine, specifically the last segment of the small intestine which is ileum and the beginning of the large intestines which is the cecum and where the intestinal contents flow.
The liver has many function including...
The liver has many functions including... a. make bile and cholesterol b. Drug Detoxification c. Produces plasma proteins (albumin, fibrinogen, for example) d. vitamin storage e. Deamination of proteins (Removal of NH2 group) f. Chylomicrons are broken down into glycerol and fatty acids g. Makes 90% of blood proteins h. Stores glycogen (glycogenolysis) and gives glucose to be transported to the body. Iron storage too! I. Urea production, it converts NH3 into urea. NH3 comes from two sources: amino acid deamination and bacterial action in the GI tract J. Along with the spleen it is involved in disposing off red blood cells
___________ is the largest INTERNAL organ and __________ is the largest organ
The liver is the largest internal organ while the skin in the largest external organ.
Liver Function 2: Blood Maintenance
The liver plays an important role in cleaning, detoxifying, and maintaining a healthy bloodstream. Let's see how it does this. a. Stores blood b. Filters and detoxifies blood coming from the digestive system -The small intestine is connected to the liver through a hepatic portal system -A portal system is when a capillary bed is connected to another capillary bed through a portal vein. That a portal system is advantageous because it allow fast diffusion of substances. -The liver then removes toxic substances from the absorbed food. c. Erythrocyte destruction -Erythrocytes are red blood cells (RBC) -There is a specific type of cells: Kupffer cells in the liver that destroy old or useless RBCs. *Note: Most of RBC destruction is done in the spleen -RBCs contain hemoglobin (red pigment), hemoglobin is broken down by Kupffer cells into bilirubin (yellowish pigment). -Bilirubin is secreted into bile (that's why bile has a yellowish-green color!) -This is also why patients who have liver disorders usually have jaundice — yellowish skin appearance due to the high levels of bilirubin in the blood that is not properly metabolized. In hepatitis (inflammation of the liver) this can occur. Increased hemolysis of red blood cells also can cause jaundice. The bilirubin cannot be removed rapidly enough. d. Bacteria destruction -Kupffer cells are phagocytes that also eat up bacteria.
The periodontal ligament is......
The periodontal ligament is a connective tissue rich in collagen that connects the cementum (a specialized bony substance covering the root of a tooth) and alveolar bone of the tooth socket.
The pharynx is ....
The pharynx is a special region common to the respiratory system and digestive system merge, which then separates into the trachea and esophagus. This is why we can breathe through our mouth, as well as eat! When we inhale air through our oral cavity, air travels through the pharynx and into the trachea.
The trachea (or windpipe) is.....
The trachea (or windpipe) is a wide, hallow tube that connects the larynx (or voice box) to the bronchi of the lungs. It is an integral part of the body's airway and has the vital function of providing air flow to and from the lungs for respiration.
The visible part of the tooth is called the.....
The visible part of the tooth is called the crown.
There is a chain of events that happens after the stomach senses food's entrance. It involves the collaboration between different.........
There is a chain of events that happens after the stomach senses food's entrance. It involves the collaboration between different cells, hormones, and enzymes.
Villi and Microvilli of the Small Intestine
Villi and Microvilli of the Small Intestine When we talk about absorption, we have to mention a hallmark of the small intestine — villi, which are finger-like projections on the walls of the small intestine. Villi are important because they increase the surface area of the small intestine to increase the efficiency of absorption. To put it in perspectives, villi actually increase the surface area of the small intestine to about the size of a tennis court! On top of each villus, there are tiny projections known as microvilli. These further expands the surface area to help in nutrient absorption.
The exocrine glands in the tongue are....
Von Ebner's glands are exocrine glands (they have ducts), in the tongue that secrete salivary lipase, beginning the process of lipid hydrolysis in the mouth.
When a food bolus enters the stomach, the stomach is distended (stretched). This stretching is a signal for G cells aka Gastrin Cells of the stomach to release gastrin............
When a food bolus enters the stomach, the stomach is distended (stretched). This stretching is a signal for G cells aka Gastrin Cells of the stomach to release gastrin............ Gastrin is a hormone with two main functions: 1. Stimulates parietal cells of the gastric gland to release gastric juice into the stomach. Parietal cells are acid-secreting cells of the stomach wall. Parietal cells also produce the Gastric Intrinsic Factor which help to absorb vitamin B-12. Gastric juice is extremely acidic with a pH of 2 due to high concenration of HCl 2. Stimulates chief cells of the gastric glands to secrete: a. Gastric Lipase Lipase is an enzyme that functions to break fats → fatty acids + glycerol b. Pepsinogen Pepsinogen is a zymogen Pepsinogen will be activated into pepsin (active form) when immersed in the acid of the stomach Pepsin is a protease that cleaves peptide bonds: proteins → amino acids
When chyme enters the small intestine specifically _______ then ______.......
When chyme enters the duodenum, carbohydrates, proteins, and fats are all still not totally digested. Ducts carryings bike and pancreatic juice enter the duodenum about midway along its length.
Cardiac Sphincter is....
Between the esophagus and stomach is the cardiac sphincter. This prevents the backflow of the stomach contents into the esophagus. Food is emptied from the esophagus into the stomach via the cardiac sphincter. A sphincter is a ring of muscles that constricts and relaxes to control openings (i.e. between the esophagus and stomach). The sphincter also prevents the backflow of the stomach contents into the esophagus. You can think of the opening between the esophagus and stomach close to the heart, hence controlled by the cardiac sphincter.
Chemotherapy Drugs kill the cells in the stomach lining
Cells in the stomach lining replace themselves every 3 or 4 days. Chemotherapy drugs are designed to kill cancer cells which are actively dividing. Unfortunately, the drugs also kill these rapidly dividing cells. The cells do grow back but many of the side effects of cancer drugs include diarrhea, and nausea. Stomach and intestinal cells suffer.
Cementum is.....
Cementum is a specialized calcified substance covering the root of a tooth. The cementum is the part of the periodontium (specialized tissue that both surround and support the teeth, maintaining them in the maxillary and mandibular bones) that attaches the teeth to the alveolar bone by anchoring the periodontal ligament
Chemical digestion....
Chemical digestion is the chemical breakdown of the mechanically digested particle into even smaller particles. This is usually accomplished with the help of key enzymes .
Enteroendocrine Cells are....
Enteroendocrine cells that are specialized cells of the GI tract In biology and medicine, the prefix entero- refers to the intestine. Enteroendocrine cells are cells found in the wall of the gut that secrete hormones that regulate numerous processes in the body, including controlling glucose levels, food intake, and stomach emptying For example, the stomach makes hormones, (although not exclusively) such as: 1. Glucagon (enteroglucagon) — Glucagon is a hormone secreted by the pancreas; it stimulates increases in blood sugar levels in the blood (thus opposing the action of insulin.) 2. Somatostatin 3. Serotonin 4. Substance P 5. Histamine 6. Gastrine
The stomach's lining is filled with....
Gastric Pits → Gastric Glands The stomach's lining is filled with gastric pits that leads to the gastric glands. Gastric glands are formed by multiple types of cells that altogether contribute to a healthy-working stomach. The lining is also made of lamina propia (connective tissue) and muscles.
Heartburn occurs when...
Heartburn typically occurs if the stomach contents back up into the esophagus. This occurs when the cardiac sphincter valve does not close tightly enough. Some foods may "relax" the valve too much and it fails to close tight enough. You might have also experience d heartburn before. This is generally caused by acid reflux, meaning that the acidic food mixture from the stomach backflows through the cardiac sphincter to the esophagus, which is not protected by mucous cells. This creates the burning sensation in the chest area.
Humans have a digestive tract with two openings....
Humans have a digestive tract with two openings: the mouth and the anus Digestion is a complex process that requires good teamwork between many organs and auxiliary glands. Below is an image with all the important "employees" of the Digestion Corp. LTD.
Humans mainly use extracellular digestion because....
Humans mainly use extracellular digestion. This is because macromolecules are mainly broken down within our digestive tract, outside of the cell. It is only after most digestion has taken place that our cells absorb the nutrients inside (which then can be further digested within the cell.) Whereas if we look at an amoeba, it actually grabs the entire chunk of food inside itself through pseudopods (extension/protrusion of the amoeba used for moving and feeding). Afterwards, the digestion process begins within its cells.
__________ is mostly responsible for digestion... whereas ______ is mostly responsible for absorption...
In fact, duodenum is mostly responsible for digestion (alliteration, duodenum main area of digestion), whereas the jejunum and ileum are responsible for absorption.
Internally each villus contains....
Internally each villus contains a lacteal. Triglyceries are made into water-soluble globules called Chylomicrons. Chylomicrons are fats coated with proteins, cholesterol, and phospholipids Chylomicrons are transported to the lacteal and to the lymphatic system. From the villi, the nutrient rich blood enters the hepatic portal vein that goes directly into the liver. Villi -> Heptatic Portal Vein -> Liver -> Organs The liver gets first "crack" and what is coming in. Toxic substances can be removed, and much of the nutritive food stuff can be converted into glycogen. Glucose is released when required.
Langergan Cells are....
Langergan Cells: Recent studies have identified cells called Langerhans cells in the esophageal mucosa. These cells are involved with phagocytosis.
Mechanical digestion....
Mechanical digestion is the physical breakdown of food. Examples of mechanical digestion include chewing food with the teeth in the mouth , and churring or mixing of food in the stomach.
_______ are acid-secreting cells of the stomach wall which also produce __________ which helps absorb_______
Parietal Cells are acid-secreting cells of the stomach wall which also Produce the Gastric Intrinsic Factor Which Helps Absorb Vitamin B-12:
Peyer's Patches are part of ______ which is...
Peyer's patches are part of GALT, if you recall stands for Gut Associated Lymphoid Tissue
trypsin and chymotrypsin, zymogen concept....
Remember how pepsin from the stomach is first secreted as a zymogen, pepsinogen, as a form of protection? The same concept applies to trypsin and chymotrypsin, which are also proteases. Protease is any enzyme that catalyzes the splitting of proteins into smaller peptide fractions and amino acids by a process known as proteolysis. The proteases such as trypsin and chymotrypsin are stored as zymogens. They are cleaved and activated by enterokinase in the intestine. This is important because it prevents the pancrease from digesting itself. Trypsin is secreted as trypsinogen Chymotrypsin is secreted as chymotrypsinogen See the similar pattern in their names compared to pepsinogen? :) When food enters the duodenum, glands in the duodenum release enteropeptidase.
Roles of the pancreas:
Roles of the pancreas: a. Secretes bicarbonate ions to neutralize stomach acid b. Secretes pancreatic amylase -Similar to salivary amylase, pancreatic amylase breaks starch → maltose c. Secretes pancreatic lipase -Works together with bile to breakdown and digest fats -It digests the emulsified fats → glycerol and fatty acids d. Secretes Trypsin and Chymotrypsin -Digests proteins → amino acids
Saliva contains the antibacterial agents...
Saliva contains the antibacterial agents: 1. IgA: a large protein that works with the immune system (IgA functions to bind and stop pathogens externally before they enter circulation, they are the most abundant in body secretions like breastmilk, tears, saliva) 2. Lysozyme: attacks the cell wall of many gram-positive bacteria (tears also contain lysozyme) 3. Lactoferrin: part of the innate defense system-has antibacterial, antiviral, and anti-parasitic properties Hopefully, you see that saliva is truly a complex fluid!! No wonder small animals like dogs and cats lick their wounds!
Saliva is...
Saliva is secreted within the oral cavity by salivary glands. Saliva contains an enzyme, salivary amylase, which will begin chemical digestion of carbohydrates in the mouth. In addition, saliva functions to lubricate the partially digested food and forms it into a bolus (small round mass) so it can be passed down the pharynx and esophagus. Saliva contains an amylase (salivary amylase or ptyalin) that breaks down starch into maltose or glucose depending on the carbohydrate. Salivary amylase, like most enzymes is a protein! Salivary amylase: Starch → Maltose Recall: maltose = glucose + gluose in a chain Therefore, the mouth doesn't fully break down starch into glucose (simplest monomer of carbohydrates), the chemical digestion process begins in the mouth and is completed further down the digestive tract. The pH of saliva is usually just over 7, namely about 7.2 I have seen a study that showed that the more alkaline the pH (the more basic the pH), the more patients had generalized chronic gum inflammation (gingivitis), whereas those that had an acidic pH had generalized chronic periodontitis ( disease that attacks the gum and bone around the teeth), a condition that involves progressive loss of alveolar bone around the teeth.
Similar to the mouth, both mechanical and chemical digestion take place in the stomach.....
Similar to the mouth, both mechanical and chemical digestion take place in the stomach: Mechanical Digestion in stomach: Churning of stomach by muscles to mix and break down the food Chemical Digestion in stomach: Enzymatic digestion of proteins and fats
The esophagus is.....
The esophagus is a tube that connects the throat and the stomach. If the mouth is the gateway to the body, then the esophagus is a highway for food and drink to travel along to make it to the stomach. Now that food passes through the mouth and the pharynx, it enters the esophagus — tubular structure that guides the food into the stomach.
The esophagus is made up of ....
The esophagus is made up of: Skeletal (striated) muscle in its upper third Smooth muscle in its lower third And a mixture of the two muscle types in its middle third. It pushes the bolus of food via peristalsis (a rhythmic wave-like contraction) down to the stomach.
The role of the pancreases is...
The pancrease is a dual organ. It has endocrine and exocrine functions. This organ is about 5 inches and lies behind the stomach and extends across (transversely) the upper abdomen. The digestive enzymes are produced by the exocrine portion, while the hormones are produced by the "islets of Langerhans" The pancreas is an organ located in the abdomen. It plays an essential role in converting the food we eat into fuel for the body's cells. The pancreas has two main functions: an exocrine function that helps in digestion and an endocrine function that regulates blood sugar A healthy pancreas produces the correct chemicals in the proper quantities, at the right times, to digest the foods we eat. Exocrine Function: The pancreas contains exocrine glands that produce enzymes important to digestion. These enzymes include trypsin and chymotrypsin to digest proteins; amylase for the digestion of carbohydrates; and lipase to break down fats. When food enters the stomach, these pancreatic juices are released into a system of ducts that culminate in the main pancreatic duct. The pancreatic duct joins the common bile duct to form the ampulla of Vater which is located at the first portion of the small intestine, called the duodenum. The common bile duct originates in the liver and the gallbladder and produces another important digestive juice called bile. The pancreatic juices and bile that are released into the duodenum, help the body to digest fats, carbohydrates, and proteins. Endocrine Function: As an endocrine gland it makes: a. insulin b. glucagon c. somatostatin (inhibits insulin and glucagon secretion) The endocrine component of the pancreas consists of islet cells (islets of Langerhans) that create and release important hormones directly into the bloodstream. Two of the main pancreatic hormones are insulin, which acts to lower blood sugar, and glucagon, which acts to raise blood sugar. Maintaining proper blood sugar levels is crucial to the functioning of key organs including the brain, liver, and kidneys.
The proteases such as trypsin and chymotrypsin are stored as zymogens. They are cleaved and activated by ________________/_____________ in the intestine.
The proteases such as trypsin and chymotrypsin are stored as zymogens. They are cleaved and activated by enterokinase/ enteropeptidase in the intestine.
The pyloric sphincter....
The pyloric sphincter is a band of smooth muscle at the junction between the pylorus of the stomach and the duodenum of the small intestine. It plays an important role in digestion, where it acts as a valve to controls the flow of partially digested food from the stomach to the small intestine.
Stomach Pylorus is....
The pylorus is simply the furthest part of the stomach that connects to the small intestine (duodenum).
Hard Vs. Soft Palate....
The roof of the mouth is known as the palate. The hard palate is the front part of the roof of the mouth, and the soft palate is the back part.
The salivary glands include....
The salivary glands include: 1. Parotid: largest of the glands (mumps is a viral infection that is caused due to infection of this gland) 2. Submandibular: produces 70% of saliva 3. Sublingual: produces mainly mucous Many minor salivary glands are found scattered in areas such as the floor of the mouth, hard and and soft palate.
The small intestine...
The small intestine is where the digestive party is taken to a climax — 90% of digestion and nutrient absorption occur here! Fun fact: the small intestine is actually about 6m long when it is fully unfolded, imagine all of that tucked in the abdomen of an average 1.7m adult!
The two ducts in the duodenum are....
When chyme enters the duodenum, carbohydrates, proteins, and fats are still not totally digested. Ducts carrying bile and pancreatic juice enter the duodenum about midway along its length. The two ducts are: 1- The Common Bike Duct 2- pancreatic Duct
