Flashcards in Lecture 2 Deck (31):
Where will you find the renal corpuscles?
In the cortex. This is where blood filtration occurs.
What does the cortex contain?
Proximal convoluted tubules, and a bit of the distal tubules as well.
What does the medulla contain?
Collecting ducts and the loops of henle.
What do the collecting ducts do at the renal papillae?
The collecting ducts will fuse to form large ducts that open at the renal papillae.
What is the medullary ray?
These are straight bundles of nephron tubules (down from cortex to the medulla). In the middle of the bundle is the collecting duct (the collecting duct receives info from nephrons around it).
What does a lobule contain?
In the centre there is the medullary ray (straight bundle of collecting duct, proximal and distal tubules). Around the medullary ray are renal corpuscles with nephrons all in between them (the nephrons drain into the collecting ducts). Defining the parameters of the lobule are blood vessels (interlobular arteries and veins).
Describe the arterial blood supply to the kidney?
The renal artery comes in and branches into the interlobular vessels (in-between the lobes). Then they curve over the base of the medullary pyramid becoming the arcuate arteries. The arcuate artery then sends shoots up towards the outer part of the kidney, called interlobular arteries (in-between the lobules). The interlobular arteries then send an afferent arteriole up to the capillary tuft.
What happens after blood flow leaves the renal corpuscle?
Depending on where you are different things happen.
1. Outer renal corpuscles: after exiting the capillary tuft, pertiubular capillary beds form (wrap around proximal tubules - take around 2/3 of filtrate). These drain into a capillary venous bed, which drains into an interlobular vein, arcuate vein and interlobular vein.
2. Deep renal corpuscles:
after leaving the renal corpuscle they dive straight down into the medulla where they form straight vessels known as arterial vasa recta. It drains into parallel venous vasa recta. They then fuse with the arcuate vein.
Where does the nephron sit in terms of the blood supply?
The nephrons sit in and around the blood vessels.
Describe the salt osmotic gradient?
The gradient is strongest at the medullary end and weaker near the cortex end. This means as filtrate goes down the nephrons salt will be sucked out of it into the blood vessels (that surround the nephrons). As it comes up again it gains salt again. Thus keeping salt a constant level.
Describe the histology of the ureter and the bladder?
There is transitional epithelium (it is folded which permits expansion and contraction). The epithelium is a mucous membrane (provides lubrication and protection from urine and pathogens). Beneath the epithelium is sub epithelial connective tissue/lamina propria (elastic). Outside the lamina propria are smooth muscle layers (inner longitudinal and outer circular). There is an outside layer of adventitia (elastic and harbors blood supply).
Describe the histology of the urethra?
Closer to the bladder the epithelium is transitional epithelium. Then it becomes stratified columnar then as it gets closer to the outside of the body it becomes stratified squamous.
How much water are people comprised of?
50-70%. Varies with sex, age, body fat. If you are a women you will have less water (50%) - as women carry more fat (fat doesn't carry as much water). Babies have 70%. Obese and older people carry less water as well.
Where is water held in the body?
1. Inside cells (intracellular fluid; ICF). 2/3 of water (28L).
2. Outside cells (extracellular fluid; ECF) 1/3 of water (14L):
-intersitital fluid (ISF). 80% of ECF water (11L)
-plasma. 20% of ECF water (3L).
How does water move between each compartment?
Water can go wherever it wants with the exception of the kidneys, ureters and bladder. However, water follows very clear rules. It will flow from high to low concentration of osmotically active molecules (i.e. high salty solutions water will want to move into that).
What happens if you were to add more sodium to one side of the membrane?
Sodium will be trapped on one side, water will want to move to that side of the membrane, this will increase the volume on that side.
What is osmolality?
The numbers of osmotically active particles per weight of water. This will determine the osmotic pressure exerted across a membrane. It is expressed as 13 solute particles per 1kg of water.
What is osmolarity?
The number os osmotically chive particles per litre of total solution.
What is tonicity?
The pressure that a solute exerts across a membrane, thereby causing movement of water. It is only useful when the particles are impermeable to the membrane.
Why is tonicity important?
Water flows down salt concentrations. The plasma membrane of cells is a semi-permeable membrane: permeable tow water but not permeable to charged molecules.
What is hypotonic?
This is where the cell is salty so the water moves into the cell, so the cell size swells and can burst.
What is isotonic?
The cells stay the same size (water moves in at same rate it moves out).
What is hypertonic?
The water move out of the cell into the salty ECF, thus the cells shrink.
What is the Gibbs-Donnan Equilibrium?
When there is protein present on one side of the membraned (they are negatively charged). The negative ions want to move down their concentration gradient to the other side, however, the positive ions want to follow negative ions (to balance the charge). Competing electrical and concentration gradients mean that at equilibrium the side with the protein is more negatively charged = voltage gradient. The more osmotically active particles are on the protein side (greater osmolality), therefore water flows into the protein side (oncotic pressure).
What do cells do to balance the osmotic pressure across their membrane?
They pump out osmotically active ions (sodium) using the Sodium/Potassium ATPase Transporter. It exchanges sodium for potassium. It sets up two competing gradients. The water wants to move towards high sodium (outside the cell) yet also to high potassium (inside the cell), therefore the water doesn't move at all. However if the water does move it moves equally.
Describe ECF osmolality - normal?
ECF osmolality is dominated by sodium.
Describe ECF osmolality when they're hypotonic?
Hypotonic ECF will cause cells to sweep by osmosis (moe osmotically active molecules inside the cell than outside).
Describe ECF osmolality when they're hypertonic?
Will cause cells to shrink any osmosis.
What does ECF volume depend on?
It is dependent on how much sodium is in our body.
How do we maintain ECF volume?
The kidney is the main regulator of water and salt homeostasis (i.e. ECF osmolality and volume). The movement of fluid across compartments is also regulated by starling forces.