PHYSIO B Kidney And Cardiovascular Flashcards
How much of the human body is composed of water? How is it divided?
About 60% of the human body weight is water. Intracellular volume constitutes about 40%, extra cellular volume about 20% considering that 4% is plasma volume, and interstitial volume about 14%.
What is the Gibbs Donnan equilibrium?
It describes the unequal distribution of permeant charged particles on epithet side of a semipermeable membrane and this occurs when we have non permeant charged elements such as proteins. Proteins attract anions and consequently attract cations.
What are other main functions of the kidneys apart from producing urine?
- The excretion of metabolic products that arrive from the liver, muscles and other cells such as hormone metabolites, creatinine, drugs and other chemicals.
- homeostatic control and the balance of bodily fluids, such as the regulation of electrolyte balance, working with the lungs to maintain acid base balance.
- Production and secretion of some hormones, such as Renin important in blood pressure regulation, production of prostaglandins and kinins.
- Ability to perform gluconeogenesis, during fasting it accounts for 20/30% of glucose.
At what level are the kidneys located?
More or less at level T12 vertebra.
What is the anatomical structure of the medulla of the kidney?
It consists of renal pyramids alternating with renal columns which are inward extensions of the cortex. The end part of the renal pyramid is called Renal papilla which empties the urine in tubes. All these tubes will then join and form the Renal pelvis which once it exits the kidney is called ureter.
How does the blood supply to the kidney work?
The renal artery entering the renal hilus branches off the abdominal aorta. It then splits into interlobar artery which runs in between lobes. Moving up towards the cortex in branches off into the arcuate arteries which branches off the cortical radiated arteries. These small arteries in the cortex give off Afferent arterioles which feeds into the renal corpuscle therefore in the glomerulus. The afferent arterioles also give off the peritubular capillaries which then drain into the cortical radiated vein.
What is, anatomically speaking, the vasa recta in the kidney?
It is a peritubular capillary network but in the medulla.
What is the anatomical structure of the nephron and where does the filtrate later go?
The capsule around the glomerulus is called Bowmans capsule, then we have the PCT in the medulla and moving downward in the medulla we have the descending limb of the loop of Henle. Then we have the actual loop of Henle, followed by the ascending limb of the loop of Henle. Back in the medulla we have the DCT. The DCT dumps the filtrate in the Collecting duct. Once it gets to the renal papilla, specifically to the papillary duct the filtrate, now urine, dumps into tubes.
What is the anatomical structure of the renal corpuscle?
Feeding it is the afferent arteriole and draining it is the efferent arteriole. In afferent arterioles you have Juxtaglomerular cells which are pressure receptors and sense blood pressure changes. In close proximity we have a portion of the DCT called Macula densa. This apparatus and the JG cells are called the Juxtaglomerular Apparatus. The visceral layer of the bowmans capsul is in contact with the capillaries and it is made of Podocytes. The outer layer is made of simple squamous epithelium.
Why is the basement membrane in the renal corpuscle important?
It contains a middle layer called Lamina Densa made of type 4 collagen and laminins. Towards the epithelium above the lamina dense we have a layer of proteoglycans particularly Heparin sulfate, found also on the other side. Heparin sulfate is very negatively charged. This is relevant bc protein in the blood are also negatively charged so they repel each other. While positive molecules like electrolytes are attracted and can pass through easily.
Why are podocytes important in the renal corpuscle?
They make up the visceral layer of the bowman capsule. In between them there is a protein called Nephrin. The space between the podocytes is called the filtration slit. Nephrin only allow only molecules smaller that 9 nm to pass. The molecules that are able to pass are then going to go through the PCT.
What are mesangial cells?
They are phagocytose any unwanted molecule that passes through in the glomerulus. They also have contractile function that can modulate the amount of blood coming through. They have gap junction which connect them to JG cells.
How much fluid is filtrated in the glomerulus?
Every min about 1200 ml of plasma flowing through the glomerulus, only 625 ml per min are actually being filtrated. Only about 20% passes though the various barriers.
What composes the Net Filtration Pressure in the glomerulus?
It is composed of pressure forcing out minus the pressure fo forcing in. The first pressure is called GHP and pushes this out of the artery and into the bowman space, it si about 55 mmHg. Albumin tries to keep molecules in the blood and the pressure is called Colloy Osmotic P, an av 30 mmHg. The Capsular Hydrostatic P is exerted by the pressure buildup in the bowman space and tries to push back fluid out, 15 mmHg. NFP is about 10 mmHg and is proportional to the glomerular filtration rate.
What other factors, other than the NFR, are important for the GFR? What is the final formula of GFR?
- The surface area of the capsule. The more SA the higher GFR is and viceversa. Clinical ex. Diabetic nephropathy
- The permeability of the glomerulus. The more permeability the higher the GFR and viceversa. Clinical ex. Glomerulonephritis.
These two factors make up KF, which is filtration coefficient.
So GFR= NFP x KF
What is Osmolality?
It is the volume of particles per kg of solvent.
What is the name of the process that involves moving substances from the blood to the kidney tubule and viceversa ?
It is called Tubular secretion, active process requiring ATP.
The second is called Tubular reabsorption and can be active or passive.
What are sodium potassium ATPases?
They pump 3 Na out of the cell and bring in 2 K, this process requires ATP. Thus this means that inside the cells the concentration of K is high.
What is 2nd active transport and why is it relevant in the PCT?
A channel brings Na form the PCT inside the cell where na is low therefore it is passive. But the same channels also brings glucose in against the gradient but the entering Na aids this process.
Another example: Na goes in passively and helps to bring A.A inside.
This can also happen with lactate.
What happens after glucose, A.As or lactate go inside the cells from the PCT?
A transporter on the other side of the cells transports it out of the cell to the artery. The glucose, A.As or lactate are now back in the blood.
What is the mechanism of reabsorption of bicarbonate?
A transporter uses carbonic acid, formed by Carbonic anhydrase catalyzing H20 and CO2, which disassociates in protons so H+ and bicarbonate. Na enters the cell and helps to push the proton out, the proton and the bicarb and forms carbonic acid. The carbonic acid reacts with Carbonic anhydrase and produces CO2 and H2O which leaves. The bicarb made earlier is then pushed into the blood.
How is glucose reabsorbed in the PCT and how does it affect water?
Glucose is reabsorbed with Na+ and water follows by osmosi. It follows the sodium ions.
How are potassium, calcium and magnesium reabsorbed in the PCT?
They move in between the PCT cells, the process is called paracellular transport.
How are lipids reabsorbed in the PCT?
Ex.urea a Lipid soluble substance, can pass through the membrane and go in the blood stream.
How are small proteins reabsorbed in the PCT?
On the membrane of the cells they can get caught on receptors, they get pulled in by endocytosis. The proteins are then broken down by lysosomes. The constituent AA are moved to the blood stream.
Why are there 300 m OSM in the descending loop of H after all the ion reabsorption in the PCT?
Bc the same amount of water is also reabsorbed there for the proportion doesn’t actually change.
