"Microbial Marvels: Exploring the Intricate World of Gastrointestinal Flora" (Medical Bacteriology II)

Introduction

• Our digestive system is a network of organs that help us digest and absorb nutrition from your food.

• It includes your gastrointestinal (GI) tract and your biliary system.

• Our GI tract is a series of hollow organs that are all connected to each other,

leading from your mouth to your anus.

• Your biliary system is a network of three organs that deliver bile and enzymes through to your GI tract your bile ducts.

Function of GIT

      •      Ingestion
•      Mechanical Processing
•      Digestion
•      Secretion
•      Absorption
•      Excretion

v Ingestion

o Occurs when materials enter to digestive tract via mouth.

v Mechanical Processing

o Crushing and shearing makes material easier to propel along digestive tract.

v Digestion

o A chemical brake down of food into small fragments for absorption by digestive epithelium.

v Secretion

o The release of water, acids, enzymes, Buffers and salt, by epithelium of GIT Tract.

v Absorption

o Movement of organic substrate Vitamin, Electrolytes and Water across GIT tract.

v Excretion

o Removal of waste product from body in the form of feces and urine.

Stages of Digestion

Mechanical Digestion is the physical brake down of food into small particles by chewing with teeth and crushing with stomach and intestine.
Chemical Digestion is series of hydrolysis rection by acid in stomach and enzymes from saliva. Stomach pancreas intestine that brake down to macro molecules into monomers such as:

Polysaccharide’s monosaccharides

Proteins amino acids

Fats Glycerol and fatty acids

What organs make up the digestive system?

• The main organs that make up your digestive system are the organs known as your gastrointestinal tract. They are: your mouth, esophagus, stomach, small intestine, large intestine and anus. Assisting your GI organs along the way are your pancreas, gallbladder and liver.

• Here’s how these organs work together in your digestive system.

Mouth

• The mouth is the beginning of digestion

• Saliva glands activate when you see or smell food

• Chewing breaks food into smaller pieces

• Saliva helps break down food further

• Swallowing moves food to the throat and esophagus

Esophagus

• The esophagus, located near the trachea in the throat, receives food from the mouth during swallowing

• The epiglottis, a flap, folds over the windpipe during swallowing to prevent choking

• Peristalsis, muscular contractions in the esophagus, move food to the stomach

• The lower esophageal sphincter, a ring-like muscle, relaxes to allow food into the stomach

• The sphincter contracts afterward to prevent stomach contents from flowing back into the esophagus, preventing acid reflux or heartburn

Stomach

• The stomach is a hollow organ that holds food and mixes it with stomach enzymes

• Enzymes in the stomach break down food further

• Lining cells of the stomach secrete strong acid and enzymes for digestion

• Once processed, contents are released into the small intestine

Small intestine

• The small intestine consists of three segments: the duodenum, jejunum, and ileum

• It is a 22-foot long muscular tube

• Enzymes from the pancreas and bile from the liver break down food

• Peristalsis moves food through and mixes it with digestive juices

• The jejunum and ileum absorb nutrients into the bloodstream

• Contents start semi-solid and end as liquid after passing through

• Water, bile, enzymes, and mucus contribute to the change in consistency

• Once nutrients are absorbed, leftover residue moves to the large intestine

Pancreas

• The pancreas secretes digestive enzymes into the duodenum

• Enzymes break down protein, fats, and carbohydrates

• Pancreas produces insulin, which is released into the bloodstream

• Insulin is the main hormone for metabolizing sugar in the body

Liver

• The liver processes nutrients absorbed from the small intestine

• Bile from the liver aids in digesting fat and some vitamins in the small intestine

• Liver acts as the body's chemical "factory," producing various chemicals needed for function

• Liver detoxifies harmful chemicals, breaking down and secreting toxic drugs

Gallbladder

• The gallbladder stores and concentrates bile from the liver

• It releases bile into the duodenum in the small intestine

• Bile aids in the absorption and digestion of fats

Colon

• The colon processes waste for easy bowel movements.

• It connects the small intestine to the rectum.

• Components include cecum, ascending, transverse, descending, sigmoid colon.

• Stool starts as liquid, ends as solid.

• Water is removed as stool passes through.

• Stored in sigmoid colon, emptied into rectum.

• Takes about 36 hours for stool transit.

• Contains food debris and beneficial bacteria.

Rectum

• The rectum links colon to anus, about 8 inches.

• Receives stool, signals need for evacuation.

• Holds stool until evacuation is possible.

• Sensors in rectum send message to brain.

• Brain decides release of rectal contents.

• Sphincters relax, rectum contracts to dispose contents.

• If contents can't be disposed, sphincter contracts.

• Rectum accommodates until sensation temporarily fades away.

Anus

• The anus is the end of the digestive tract.

• Consists of pelvic floor muscles and anal sphincters.

• Detects rectal contents, signalling liquid, gas, or solid.

• Sphincter muscles control stool release.

• Pelvic floor muscle creates angle preventing stool passage.

• Internal sphincter stays tight, relaxes when stool enters.

• External sphincter holds stool until reaching toilet.

• Relaxes at toilet to release stool contents.

Normal flora of GIT

Normal Flora : The microbial population that inhibit at the internal and external surface of healthy normal human and animal normal flora are also called COMMENSALS.

i.e. organism that dine together.

• In s normal condition in a healthy human they are harmless and may even be beneficial.

Origin of Normal Flora

A fetus is sterile when born. The new borning starts the normal flora passes through virginal tract and then to environment such as air, foods etc.

Involve internal and external organ

Normal Flora depend on age, Diet , geographic habitats.

Factor Influencing the Normal Flora

• Local Environment

• Age

• Diet

• Sex

• Immune Condition

• Use of Antibiotics

Types of Normal Flora

• Resident Flora Members of the Flora that are constantly present in/on the body that cannot be removed permanently these prevent the permanent colonization of the body by other organism e.g. E.coli in intestine region.

• Transient Flora Population which varies from time to time and that can removed permanently e.g. Pneumococcus or meningococcus may be found in nasopharynx of Human from time to time.

Importance of Normal Flora

• Synthesized B-complex and vitamin-K.

• They protect our body by preventing the colonization of pathogenic microorganisms.

• It elevates the immune system.

• Produces the anti-biotic like substance, e.g. :Fatty acids, peroxidases Bacteriocins which inhabits the growth of pathogenic Microorganisms.

• Some produce endotoxins which activates the complement pathway, it augment the defense mechanism of the body.

Harmful Effect of Normal Flora

• When host immune system decreases they become opportunistic pathogens and cause diseases.

• Some may cause diagnose confusion.

• Some penicillinase producing Microorganisms can aggregate and develop antibiotic resistance (Drug resistant).

Nature of Normal Flora

• Commensal microflora: These microorganisms gets benefits from human host and give neither benefits nor harmful effects to host. Majority of normal flora are commensal types.

• Mutualistic microflora: These microorganisms gets benefits from host and at the same time give benefits to the host.

• Opportunistic microflora: These microorganisms, under normal condition live as commensal on host body but they causes diseases if opportunity is available. For example; Normal flora of Gl tract ie. E.coli causes urinary tract infection (UTI), if the site of habitat is changed.

Normal Flora of Oral Cavity

• The oral cavity or mouth is totally free of microorganisms at the time of birth, but it is colonized by microorganisms from the surrounding environment within hours after a human baby is born.

• In the beginning the microbial flora that establish in the mouth belong to the genera Streptococcus, Neisseria, Actinomyces, Villanella, Lactobacillus, and some yeasts.

• These initial microorganisms are aerobes and obligate anaerobes.

Normal Flora of Digestive Tract

• The stomach contains fewer bacteria due to its high acidity nature.

• However, there are some bacteria that survive there like the Helicobacter Pylori that is currently proving to be the cause of most cases of gastritis and peptic ulcers.

• Likewise, the small intestine contains small numbers of Streptococci, Lactobacilli, and yeasts, particularly Candida albicans.

• Nevertheless, bigger numbers of these bacteria are found in the lower parts of the ileum. The colon is the main site for bacteria in the body. Several bacteria like Bacteroides, Bifidobacterium, Eubacterium, Coliforms (e.g. E. coli), Streptococcus, Lactobacillus and Clostridium reside in the large intestine.

NORMAL FLORA OF GASTRO INTESTINAL TRACT STOMACH

• INTESTINE

• Small intestine:

• Duodenum gram + positive cocci and rods are more.

• Jejunum : gram positive, gram negative bacterium can be seen, Lactobacilli Diphtheroid, Enterococcus faecalis, yeast-candida, albicans.

• Ileum pH-alkaline, anaerobic gram negative bacteria are more mainly enteron bacterial, shigellosis, typhoid.

e.g. acid tolerant streptococci, staphylococci lactobacilli, candida albicans, Helicobacter.

NORMAL FLORA OF GASTRO INTESTINAL TRACT STOMACH

• Large Intestine: The large intestine or colon contains the largest number of bacterial community number of bacterial community in human body.

• In Large intestine or colon act as a fermentation vessel, and the microflora of it consists primarily of anaerobic, gram-negative, non-sporing bacteria and gram positive, spore forming, and nonsporting.

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