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Gastro Intestinal System

Mouth (Oral cavity) (Buccal Cavity)

  1. Chewing (Masticate)
  2. Morcellation of Food
  3. Hydrolysis – Enzyme assisted breakdown of Food
    1. Enzyme comes from couple of glands
    2. Contributes to certain percent of saliva
  4. Make Bolus
  5. Swallow
  6. PhLeval – 7.0

Teeth

  1. Central Incisors – 4 – Used for cutting
  2. Lateral Incisors – 4 – Used for cutting
  3. canine – 4 – Used for Gripping
  4. Premolar – 8 – Mola in latin means grindstone – Used for Grinding
  5. Molar – 12 – Used for Grinding

3rd Molar are called wisdom teeths

Upper Jaw – Maxilla

Lower Jaw – MandibleGums – Gingiva

Glands involved in Mouth

  1. Parotid – Largest Gland – Located on the side of your mouth right above the Jawbone – Releases 25 % of saliva – Serous – contains enzymes – Alpha Amylase
  2. Submandibular – Releases 75 % of saliva – Below the mandibule(Lower Jaw Bone) – mainly serous but contains mucinous – Alpha Amylase
  3. Sublingual Gland – release 5 % of saliva – mainly releases mucin and less enzym – Alpha Amylase

Von Ebner’s Gland  releases less than 5% of saliva – Located at the tip of the tongue – Releases an enzym called lingual lipase – As the name suggests it breaks down lipids(specifically Triglycerides). Triglycerides are broken down into free fatty acids as well as DG(dIGlycerides, MG(MonoGlycerides))

Alpha Amylase

Enzyme that will take carbohydrates and break it down to smaller carbs

Glands Function in Mouth

  1. Releases Serous Content – Rich in enzymes, salts

Mucinous Content – contains mucin to wet the food

Tongue(Lingula)

Hydrolysis

Enzyme assisted breakdown of Food.

Made up of 2 type of muscles

  1. Extrinsic Muscles
    1. Elevate
    2. Lower
    3. Protrude
    4. Retract
  2. Intrinsic Muscles
    1. Shorten and Widen (Anterior/Posterior)

Lenthen and Narrow (Right Side to Left Side, Side to Side)

Esophagus

  1. Upper Esophageal Sphincter is a skeletal Muscle. It is under voluntary control.
  2. Lower Esophageal Sphincter – Peristalsis
  3. Propel Bolus

Esophages has 3 parts

  1. Skeletal Muscle – 1/3
  2. (Skeletal + Smooth Muscle )- 1/3

Smooth Muscle – 1/3

Peristalsis

Wave like propulsion of food

Stomach

Three types of cells are involved here

  1. Parietal Cells – Releases HydroChloric Acid
  2. Chief Cells – Secrets an enzyme called Pepsinogen
  3. Mucous Cells – Releases Mucin – Helps stomach by not letting pepsin or hydrochloric acid degrades stomach

Pepsin

  1. Pepsin degrades one type of nutrient – Protein – Breaks Peptide Bonds – This is the bond that connects amino acids.

Hydrochloric acid interacts with Pepsinogen and produce Pepsin which is used in Hydrolysis

Can store upto 4 litres of Food Anytime

  1. Churning
  2. Hydrolysis – Enzyme assisted breakdown of Food
  3. Store Food
  4. Take Bolus and make Chyme

DuoDenum

Small Intestine

  1. Hydrolysis – Enzyme assisted breakdown of Food
  2. Absorption of Nutrients

Structure

  1. Duodenum – Most Disgestion occurs at this part
  2. Jejunum – Most absorption occurs
  3. Ileum – Vitamin B12, A, D, E, K absorbed here

Duodenum

  1. Stomach provides Chyme, HCL
  2. Liver, Gallbladder provides Byle
  3. Pancreas provides Enzymes – Trypsinogen, Chymotrypsinogen
  4. Brush Border Enzymes

Enzyme

If a enzym name ends with gen then it is not ready to work yet. it still needs one more cut. Ex. Trypsinogen, ChymotrypsinogenIf a enzym name ends with ase then it is a result of broken bond. Ex. Peptidase – Peptide bond is broken to produce Peptidase

Brush Border

  1. Projections in the Duodenum is called Villi. One such projection is called Villus
  2. Each villus contains some projections called microvilli and each such projection is called microvillus
  3. These villus produces enzymes for digestion
  4. Contains an enzym named enteropeptidase. This enzym breaks trypsinogen and produces trypsin. Chymotrypsinogen into Chymotrypsin

Digestions

Involves 4 macro molecules in our body

  1. Proteins – Are just chains of amino acids – Peptidase – is an enzyme. Peptid bond is broken by Trypsinogen, Chymotrypsinogen produced by pancreas to break petidase.
  2. Carbs – Repeated units of simple sugar – Glucose + Galactose = Disaccharide = Lactose. Pancreas release an enzym called amylase. which breaksup the sugar bond i.e, Glycosidic Bond. Brush Border enzym called lactase can only be used to break apart lactose
  3. Nucleotides – Make up Nuceic acid, our DNA – breaks by brush border enzym nucleosidases
    1. Phosphate Group that sits on a ribose sugar and have a base(coating part of our DNA. i.e, adenine, guanine)
  4. Fat has two parts – Liver/Gallbladder Byle emulsify opr organise fats. Pancreas release lipase
    1. Triglycerol  Head
    2. 3 Fatty acid tails

Monosaccharide – Single Sugar

Disaccharide – Two SugarsPolysaccharide – Whole bunch of sugars

Small Intestine Absorption

  1. Amino Acids – Primary(ATP) Active Transport – ElectroCyte – Blood Capillary
  2. Monosaccharide – Secondary(Na+) Active Transport – ElectroCyte – Blood Capillary
  3. Nucleotides – Primary Active Transport – Blood Capillary

Fat – Diffuse in to electrocytes and produce Chylomicrons – Lymphatic capillary(Lacteal) – veins – hearts – artery

ATP – Adenosine Tri Phosphate

Electrocyte – Intestinal Cell

Large Intestine (Colon)

  1. Absorbs water, ions, vitamin k
  2. Colon, Rectum, Anus
  3. end of small intestine is the ileocecal valve
  4. Fist part of Large Intestine is called cecum
  5. Appendix
  6. Right Colon – Ascending Colon
  7. Transverse Colon
  8. Descending Colon
  9. Last part is called sigmoid colon
  10. Rich source of microorganisms like bacteria
  11. Batceria in the large intestine assist the digestion.

Microorganisms in the large intestine actually do most of the digestions.Ex. Carbohydates in beans. Beans Beans good for the heart. The more you eat the more you produce methane(CH4) and hydrogen sulfide(H2S)(Farting)

Large Intestine Absorbs

  1. WATER
    1. Too little water – Diarrhea
    2. Too much water – Constipation
  2. Inorganic ions(Na+, K+)
  3. Large intestine absorbs the same set of components as that of kidney. Removing large intestine will still make the patient survive with the help of kidney
  4. Rich source of micororganisms

Cholera

Bacteria attacks certain receptors and proteins in the lining of the intestine leading to the death by dehydration.

Solution : Hydrate the patient and let the large intestine move the bacteria out.

Rectum

Is not responsible for any absorptionMain thins rectum accomplishes is Storage

Anus

  1. Composed of 2 sphincters
    1. Internal Anal Sphincter – Composed of Smooth Muscle – Involuntary Control
    2. External Anal Sphincter – Composed of Skeletal Muscle – Our Control
  2. Expulsion

Sphinters are muscles that just close off a hole

Control of the GI Tract

Other than brain Intestines are the smartest part of the body.

  1. Digestive System has its own nervous system(Enteric Nervous System). Its got its own brain
  2. Digestive System can act on its own without sending neuronal information or signlas to the brain or the spinal cord to regulate its action

Gastrocolic Reflex

Involves stomach and signals Large Intestine to make space for the new food.Hormones are substances that are released by the tissues in our body and then go through blood vessels and go to some target organ or target tissue to cause an effect.

Hormones that regulate GI tract

  1. Gastrin – is a hormone that is released when we notice that there is a food in our stomach. Release out of the stomach to the blood stream and come back again to stomach to simulate the digestive juices. Gastrin is released by mucosal cells.
  2. Gastrin causes secretion of couple of things
    1. Triggers stomache to release HCL by parietal cells in the stomach
    2. Triggers pepsinogen(inactive form of pepsin) to be released by the chief cells of the stomach
  3. Increases Stomach Motility and produce chyme and send to duodenum
  4. Observed Ph level and if it reaches 3 will decrease Gastrin release(Low Ph decreases our gastrin release)

Stomach Chyme to Duodeum causes

  1. Secretin is released to the blood stream and it goes to 2 places(acid content of the chyme)
    1. Pancreas – produces Bicarbonite(to neutralise the acid) rich solution
    2. Stomach
  2. Cholecystokynin is released from our intestinal muscosa to the blood stream and it goes to 2 places.(Fat in our chyme causes this hormone to release)
    1. Pancreas to stimulate the release of our pancreatic enzymes(lipase – is used to break down lipids)
    2. Gallbladder – will cause the gallbladder to contract to release bile to emulsify fat

Liver

  1. Is responsible for Metabolism
  2. Responsible for bile production
  3. Responsible for detoxification – Achieved mainly by  cytochrome p450 enzymes
  4. Catabolism, Anabolism are achieved in Liver
  5. Responsible for Storage of Nutrients
    1. Carbs – Carbohydrates
    2. Fats
    3. Proteinds – but not stored in Liver – Processed into molecules like albumin and then cast off into the blood stream. They will float around and carry out other functions until they need to retreived by the liver to be broken or used for other molecules
  6. Carbs, Fats can be stored in 3 different ways
    1. Glycogen – Polysaccharide – Linkage of a whole bunch of monosaccharides
    2. Lipproteins – Lipo means Fat.
    3. Triglycerides – one form of fat that we ingest in our food

Blood Supply to the Liver

It has two separate blood supplies

  1. First comes from the intestinal tract from the portal vein. Portal Venous System supplies liver with nutrient rich blood. Nutrients consumed from the intestinal tract are absorbed and go through the circulation and endup in the portal vein to be delivered to the liver for metabolism
  2. Proper Hepatic Artery – Oxygen Rich Red Blood Cell

HepatIc Vein

  1. takes blood out of the liver
  2. Nutrient and Oxygen poor

Bile

Bile is composed of 2 things

  1. Bile Pigments – Provides the color
  2. Bile Salts – Emulsify(organise) fats – Allow us to turn fats into micells which can then be absorbed in ileum
  1. Bile is needed for absorption of fat from food.
  2. Bile leaves the liver through Common Hepatic Duct

Biles produced in liver and goes through common hepatic duct and flows to cystic duct and goes to gall bladder.

Gall Bladder Stores Biles

Hormone that triggers Gall Bladder to release bile is Cholecystokinin(CCK). Cholecyst – Gall Bladder.Cholesystokinin makes the gallbladder to contract and makes the gallbladder to release the bile to the common bile duct and finally the bile salts reaches the Duodenum part of the GI tract. Ileum is where the bile salts and fats are absorbed. Then bile salts heads back to the liver to be reused.

Peritoneum

Another word for Abdomen

Pancreas

  1. Located at the RetroPeritoneum. Retro – Back.
  2. Pancreas releases powerful enzymes
  3. Pancreas is uncapsulated
  4. Eat when you can, sleep when you can and dont mess with the pancreas

Exocrine Pancreas

  1. It takes salts and enzymes and releases them in duodenum
  2. Releases Bicarbonite HCO3 – will neutralize our gastric acid(HCL)

Enzymes Produced by Pancreas

  1. Amylase –  is responsible for breakdown of starch(just a whole bunch of carbohydrates stakced upon one another) into smaller carbohydrates(Glucose, monomers, Disaccharides)
  2. Lipase – It break down lipids (triglycerides) into free fatty acids + Monoglycerides + Diglycerides + Glycerol
  3. Proteolytic – Trypsinogen, Chymotrypsinogen. Trypsinogen is an inactive form of trypsin. Chymotrypsinogen is an inactive form Chrymotrypsin
  4. Trypsinogen  + Enteropeptidases -> Trypsin
  5. Chymotrypsinogen + trypsin -> chymotrypsin

ZymogenAn inactive enzyme because it has an extra bond, Usually a peptide bond that needs to be broken in order for it to start doing its thing

Endocrine Pancreas

  1. Release Hormones into the blood stream

Alpha Islet Cells

  1. Releases a hormone called Glucagon.
  2. Function of Glucagon is take Glycogen(Bunch of Glucose Molecules) and breaks them into smaller Glucose Molecules. Responsible for breakdown of whole bunch of macro molecules.

Beta Islet Cells

  1. House and release Insulin

Delta Islet cells

  1. Releases a hormone called somatostatin.
  2. Stops the effects of all active hormones like Glucagon, Insulin, Cholecystokynin

Insulin

  1. Insulin helps to build glycogen from glucose
  2. Build up or storage of macro molecules
  3. Insulin – diabetes – let too much glucose floating around our body. Diabetes – Eye, Nerve, Kidney Disease

Diabetes Type 1

  1. We have no insulin production. We are not able to store sugar and glycogen

Diabetes Type 2We have insulin receptors. But they are broken

Portal Triad

  1. Portal Vein – Sinusoids comes from the portal vein
  2. Proper Hepatic Artery
  3. Common Hepatic Duct

Hepatic LobulesHas Hepatocytes (single liver cell)

Catabolism

Breakdown of nutrients

Enzymes Produced by Pancreas

  1. Amylase –  is responsible for breakdown of starch(just a whole bunch of carbohydrates stacked upon one another) into smaller carbohydrates(Glucose, monomers, Disaccharides)

Lipase – It breaks down lipids (triglycerides) into free fatty acids + Mono glycerides + Diglycerides + Glycerol

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