The digestive system Flashcards
What are the purposes of the gut?
To break food down physically and chemically
Absorb water
Excrete cholesterol
Synthesise some vitamins
What are the functions of the mouth?
Physically/mechanical breakdown of food
Initial digestive enzymes released
infection control
What is the function of the oesophagus?
Rapid transport of bolus to stomach through thorax
What are the 3 main salivary glands?
Parotid
Submandibular
Sub-lingual
What is the role of saliva?
Release digestive enzymes
Oral hygiene
Lubricate food bolus
What are the functions of the stomach?
Storage facility
To produce chyme - physical and chemical breakdown, digestion started
Produces acid - unravels proteins, activates enzymes, disinfects stomach contents
What are the properties of chyme?
Partially digested
Acidic
Very concentrated
What is the duodenum and what are its functions?
Start of the small intestine
Pancreas and liver join the gut here
Acidic chyme is neutralised here
Water enters duodenum through gut walls - dilutes chyme
Digestive enzymes enter here
What are the functions of the liver?
Produces bile
Synthesises proteins like albumin/clotting factors
Detoxifies blood
Energy storage (glycogen)
Mainly composed of cells called hepatocytes
What is the gall bladder and what are its functions?
Connected to liver above and duodenum below
Stores and concentrates bile (which comes from liver)
Connects to GI tract through a system of tubes (biliary)
Contracts when fat is detected in the duodenum - releases bile into the duodenum
What does bile contain?
Bile salts - help emulsify fats into smaller droplets
Cholesterol - helps excrete cholesterol from the body
Bilirubin - when red blood cells die this is released and needs to be excreted from the body otherwise can lead to jaundice (bilirubin gives stool its colour)
What is the endocrine function of the pancreas?
Produces insulin/glucagon
(Very small part of pancreas)
What is the exocrine function of the pancreas?
Produces enzymes for digestion
(Most of pancreas)
What are the functions of the jejunum and the ileum?
Final digestion
Nutrient absorption (mainly jejunum)
Water/electrolyte absorption (mainly ileum)
What are the functions of the large intestine?
Final water absorption
Temporary storage
What is the function of the rectum and anus?
Defaecation
What is the gut microbiota/microbiome?
Refers to the bacteria/fungi/viruses that live in our gut (produce some vitamins, prevent other bacteria from causing disease)
How are carbohydrates digested to sugars?
Long chains of sugars (starch) or shorter chains of sugars
Broken down by enzymes into single sugar units (monosaccharides) to be absorbed
How are proteins digested into amino acids?
Long chains of amino acids (polypeptides)
Broken down by protease enzymes like pepsin
What is the problem with digesting ingested proteins?
The gut is also made of proteins so need to make sure we don’t digest the gut
Proteases are stored as inactive form and activated only when in a safe environment
How are lipids digested into monoglycerides?
Bile - breaks fat down into smaller droplets (emulsify)
Lipases - break the fat molecules into smaller units
How does the small intestine increase its surface area for absorption?
Folding the gut (permanent folds)
Having finger like projections (villi)
Having further tiny projections into gut lumen (micro villi)
How does the gut absorb substances?
Through cells called enterocytes from the lumen (apical side) to the blood/lymph (basolateral side)
Where to sugars and amino acids get absorbed into?
Into the blood and taken to the liver directly
