You are what you eat Block 3 Week 2 Flashcards
Know the position of the organs in the abdomen ?
- We have the stomach and Infront of it we have the pancreas.
- Wrapped around the pancreas we have the small intestine
- We have the liver and right kidney on the right
- We have the spleen and left kidney on the left
What is the function of the liver ?
- Produces bile - which a compound needed to digest fat and to absorb vitamin A, D, E and K
- Detoxification - Clearing the blood of drugs and other poisonous substances
- Regulation of glycogen storage - Conversion of excess glucose into glycogen for storage (glycogen can later be converted back to glucose for energy) and to balance and make glucose as needed.
- Processing of hemoglobin for use of its iron content (the liver stores iron)
- Production of cholesterol and special proteins to help carry fats through the body
- Clearance of bilirubin, also from red blood cells. If there is an accumulation of bilirubin, the skin and eyes turn yellow.
- Conversion of poisonous ammonia to urea (urea is an end product of protein metabolism and is excreted in the urine)
Where is the liver found ?
- Right upper quadrant then projecting into the left upper quadrant
- Gallbladder in the right upper quadrant
Liver in a cadaver
In between the 2 big lobes of the liver we have the falciform ligament
Describe the liver surfaces ?
- Diaphragmatic surface (red)
- Visceral surface (blue)
Extra info:
- kidney is retroperitoneal
Describe the peritoneum ?
- The peritoneum is a continuous membrane which lines the abdominal cavity and covers the abdominal organs and and provides pathways for blood vessels and lymph to travel to and from the viscera.
- The peritoneum consists of two layers the parietal and visceral peritoneum.
- Both layers of the peritoneum are made up of simple squamous epithelial cells called mesothelium.
- Parietal perineum: lines the internal surface of the abdominopelvic wall
- Visceral peritoneum cover the abdominal viscera ( organs)
Where is parietal peritoneum derived from ?
Somatic mesoderm in the embryo
Where is the visceral peritoneum derived from ?
Splanchnic mesoderm in the embryo
What is intraperitoneal (aka peritoneal) ?
- Are organs involved by visceral peritoneum, which covers the organ both anteriorly and posteriorly.
Examples:
- Stomach
- Liver
- Spleen
What are retroperitoneal organs ?
- Retroperitoneal organs are not associated with visceral peritoneum
- they are only covered in PARIETAL peritoneum, and that peritoneum only covers their ANTERIOR surface.
Where is bile made and stored ?
Bile is a fluid that is made and released by the liver and stored in the gallbladder
Why does blood go from the stomach and small intestine to the liver ?
All the blood leaving the stomach and intestines passes through the liver. The liver processes this blood and breaks down, balances, and creates the nutrients
and also metabolizes drugs into forms that are easier to use for the rest of the body or that are nontoxic.
Describe the livers dual blood supply ?
There are 2 distinct sources that supply blood to the liver, including the following:
- Oxygenated blood flows in from the hepatic artery
- Nutrient-rich blood flows in from the hepatic portal vein
Describe the structure of the liver ?
Structure: 4 anatomical lobes (right, left, caudate, quadrate) 8 functional segments
How much fat do we take in the western diet ?
100-150g daily. This contributes to about 40% of out total dietary energy intake.
Fat and water do not mix.
Fat always has to be in solution
- If we put oil and water into a bottle it will separate into 2 different spaces. So oil at the top and water at the bottom.
- If we shake the bottle the oil and water will mix which is called emulsification. The fat is broken down into smaller droplets.
- TAG has to be digested in an aqueous environment which is the intestine.
- Bile and enzymes are released into the small intestine which help with the breakdown of fats.
What prevents the small TAG particles from re-aggregating
into a bulk fat phase in the duodenum where mixing is not
so active?
Bile is produced in the liver
Stored in the gallbladder
Released into the small intestine
The bile covers the fats in a polar surface which prevents small emulsion droplets from reaggregating
Where does fat wee ingest come from ?
Triacylglycerol’s from:
- cooking oils
- butter
- margarine
- meat fat
- cereal
- nut oil
Phospholipids from cell membranes
Cholesterol esters from animal cell fat stores
Cholesterol from animal cell membranes
What are also taken in when we take in fats ?
- Vitamins
- essential fatty acids
What are the basics of fat digestion ?
Lipids are digested mainly in the small intestine by bile salts through the process of emulsification.
Bile salts help break down big lipid droplets into smaller droplets
This makes it easier for lipase enzymes to digest the Triacyglycerides.
Another factor that helps is colipase and amphipathic protein that binds and anchors lipase at the surface of the emulsion droplet
Bile salts solubilize the products of lipase digestion into micelles to facilitate the uptake into enterocytes in the jejunum region
What are the basics of fat digestion ?
Lipids are digested mainly in the small intestine by bile salts through the process of emulsification.
Bile salts help break down big lipid droplets into smaller droplets
This makes it easier for lipase enzymes to digest the Triacyglycerides
Bile salts solubilize the products of lipase digestion into micelles to facilitate the uptake into enterocytes in the jejunum region
How are fats absorbed ?
- After digestion, monoglycerides and fatty acids associate with bile salts and phospholipids to form micelles. Micelles are about 200 times smaller than emulsion droplets. Micelles are necessary because they transport the poorly soluble monoglycerides and fatty acids to the surface of the enterocyte where they can be absorbed. As well, micelles contain fat soluble vitamins (A, D, E and K) and cholesterol.
- Micelles are constantly breaking down and reforming, feeding a small pool of monoglycerides and fatty acids that are in solution. The hydrophilic outer region of the micelles enables it to enter the aqueous layer surrounding the microvilli that form the brush border of the enterocytes. Only freely dissolved monoglycerides and fatty acids can be absorbed, not the micelles. Because of their nonpolar nature, monoglycerides and fatty acids can just passively diffuse across the plasma membrane of the enterocyte. The bile salt portion of the micelle remains within the lumen of the gut until the terminal ileum. Some absorption may be facilitated by specific transport proteins.
- Once inside the enterocyte, in the smooth endoplasmic reticulum monoglycerides and fatty acids are resynthesized into TAG. The TAG is packaged, along with cholesterol and fat soluble vitamins, into chylomicrons. Chylomicrons are lipoproteins, special particles that are designed for the transport of lipids in the circulation.
- Chylomicrons are released by exocytosis at the basolateral surface of the enterocytes. Because they are particles, they are too large to enter typical capillaries. Instead they enter lacteals of the lymph and leave the intestine in the lymph.
- Chylomicrons are then released into venous circulation via the thoracic duct.
- Lipids thus avoid the hepatic portal vein and bypass the liver in the short term.
What are the sources of lipid - degrading enzymes ?
3 types:
- Lingual lipase from Ebner’s glands on the dorsal surface of the tongue
- Gastric lipase
- Pancreatic lipase: which include pancreatic lipase, phospholipase and cholesterol esterase’s
In which part of the small intestine are fats absorbed the most ?
Jejunum