Lectures 17, 18 Flashcards
What are the problems of the terrestrial environment when the animals evolved to come on land?
. There is hardly any salt
. You are at risk of drying out
. It is not way to get rid of waste if Thrace to conserve water
What animals excrete waste in the form of ammonia?
Fish- ammonotelic animals (aquatic invertebrates and most bony fish)
not a prob because it diffuses into the water
The excrete 1g of nitrogen in the form of ammonia how much water would you need?
0.5l
How much water in needed to excrete 1g of nitrogen in the form of urea?
0.05l
How much water is needed to excrete 1g of nitrogen in the form of uric acid?
0.001
What animals excrete nitrogen in the form of urea?
Ureotelic animals- mammals, most amphibians and cartilaginous fish
What animals excrete water in the form of uric acid?
Uricotelic animals- birds, insects, non-avian reptiles
In the glomerulus what percentage of blood is filtered into the Bowen’s capsule?
20%
What is the podocytes?
are part of Bowman’s capsule and wrap around the capillaries
Where does most of the reabsorption in the tubule takes place?
Proximal convoluted tubule
What percent of Chlorine, sodium, potassium, amino acids, HCO3-and glucose do you reabsorb?
Chlorine: 67 Sodium: 67 Potassium: 65 Amino acids: 100 Glucose: 100 HCO3-: 90
What do the epithelial cells building the proximal tubule contain?
Microvilli to exchange the absorptive SA
What does Na+/K+ ATPase do?
Generates a chemical gradient for sodium ions. Will constantly pump sodium out of the cell in exchange for potassium- this requires energy
The gradient for sodium ions causes by the sodium/potassium ATPase is used for what?
To co-transport other substances into the cells at the luminal membrane
What happens to drugs in the body?
They are imported into the proximal tubule cells through suites of transporters in the interstitial membrane (so drugs are taken into the tubule system/ the filtrate
What does the descending limb of the loop of henle contain?
Water channels (aquaporins) but it is impermeable to salts
What does the ascending limb of the loop of henle contain?
Salt transporters (NKCC)but it is impermeable to water
What are the principal cells in the collecting duct responsible for?
Water absorption
What are intercalated cells on the collecting duct responsible for?
Urinary acidification
Why do animals eat?
To obtain energy
Maintain cellular metabolism
Allow growth and reproduction
All animals are heterotrophs (do not produce their own food)
What does animals extract from food?
. Proteins . Carbohydrates . fat . Ions, grace elements, water . Essential compounds which cannot be synthesised by the body (human): vitamins or essential amino acids (lysine, leucin)
What are all digestive enzymes?
Hydrolases
What teeth do carnivores have?
Canine teeth
What teeth do herbivores have?
Incisors and canines (large molars and premolars are used to bring the plant matter)
How do birds grind their food without teeth?
Have gastroliths (=stomach stones) are ingested and used to grind the food
What are chief cells in the stomach?
Enzyme secreting cells
What type of food starts being digested in the mouth?
Carbohydrates
What type of food is digested in the stomach?
Proteins (proteases in the stomach) (pepsinogen)
What are parietal cells?
Acid secreting cells (HCL)
What does the HCl in the stomach do?
Helps break down proteins
Also will transform pepsinogen into pepsin
Pepsin and HCl do not distinguish between own cells and food so why do we not digest our stomachs?
- Acid and enzymes are only secreted when you eat
- Enzymes are secretes as inactive precursor enzymes which are then activated by acid (HCl)
- The inner surface of the stomach is covered by a layer of mucus (secretes by the epithelial cells) with neutral pH, which protects the epithelial cells from being digested
What does the duodenum have connections to?
The pancreas
What does the pancreas do?
Produces digestive enzymes and bicarbonate solution
What does the liver do?
Produces and secretes bile
What does the gallbladder do?
Stores bile, which aids in digesting lipids
What does bile help you digest?
Lipids (fats)
What happens in the duodenum?
This is where most of the enzymatic digestion takes place
What happens in the jejunum and the Ileum?
This is where digestion stops and absorption takes place
What is the length and the approx surface of the human small intestine?
3-5m long
250m2 SA
Why is the SA of the small intestine so large?
T is due to the intestinal folds, the villi and the microvilli
Dietary fats are emulsified into tiny droplets called what?
Micelles
What does pancreatic lipase do?
Hydrolysed fats in the micelles to produce fatty acids and monoglycerides
What are most absorbed nutrients in the small one stone transported by and to where?
What is the exception and what are they transported by?
Transported by the portal vein to the liver (detoxification before distribution in the body)
Fats are absorbed via the lymphatic system and bypass the liver
Why do fats bypass the liver?
Because the liver is so metabolically active it would just consume all of the fats so the rest of the body would not have chance to get those lipids
What does the appendix do?
Is a reservoir for beneficial microorganisms
How does the large intestine (colon) carry out digestion?
There are no digestive enzymes but chemical digestion is done by bacteria (produce e.g. vitamins m, fatty acids, break down fibre and carbohydrates)
