Renal System and Nephron Processes Flashcards
Alimentary canal
Also known as the digestive tract, is a long tube of organs that food and liquids pass through as they are digested and leave the body - from the mouth to the anus.
Overall estimates on and water absorption through the intestines
2kg of food and 2L of water is ingested over 24 hours. With the secretions of saliva, bile, gastric juice, pancreatic and intestinal secretions, a total of 9L enters the lumen of the intestines over 24 hours. 7.5L is absorbed into the small intestine, and 1.4L into the large intestine. 0.1L is lost through feces, containing 100ml water. So, nearly the same amount input into the digestive system is input into the blood stream.
Why is consuming 2L of water every 24 hrs needed?
To loosen up feces and properly digest food. But also, to remove cardiovascular waste.
Jejunum
The middle part of the small intestine and the most active site for water absorption.
Ileum
Second site for water absorption in intestines and the end of the small intestine
Colon
Part of the large intestine, which is connected to the small intestine at one end and the anus at the other. It absorbs water against osmotic gradient.
Na+ Absorption
Occurs throughout the intestine, especially colon.
K+ Absorption
Net absorption primarily in jejunum and ileum.
Diarrhea
Causes excessive potassium loss/not ingesting enough potassium. Both effect eachother.
Kidneys
Remove bodily waste via constant filtration. Requires an extra 2L of water every day since the filtration is constant
Filtration Rate
Approximately 180 L of blood filtered daily.
Cardiovascular System relation to kidney function
Transports oxygen, nutrients, and wastes that enter kidneys. Alo transports hormones that control idney function.
The cardiovascular capilliaries also run next to kidney nephrons to provide them with this.
What goes inside the nephron and what remains in the capillaries?
In capilliaries:
* Solid material like red and white blood cells
Into Kidney nephrons:
* Water
* Ions
* Organic molecules - eg Amino acids, vitamins, gluecose
* CO2 and 02 gas
Bowman’s Capsule
First nephron structure receiving filtered plasma.
What type of molecules flow into the Bowman’s capsule?
Plama components:
* Water
* Ions
* Organic molecules
* Trace elements and vitamins
* Gases
Examples of organic materials entering the Bowman’s capsule from the plasma
- Amino acids
- Glucose
- Nitrogenouse watse
- CO2 and O2
Label the parts of the kindey
Control of urination
The bladder has a sphincter surrounded by muscle cells regulated by the nervous system.
Nephron Processes
Includes filtration, reabsorption, secretion, excretion.
Where is the nephron
In the renal cortex
What is the nephron made of?
A single layer of cells
Label this image of the nephron. Label the parts that also are not mentioned
What is the glomerelus made of?
A globular network of renal arteries = golemerular capillaries
4 main processes of the kidneys
Filtration, Reabsorption, Secretion (hormones) and Excretion (of urine)
Where is the loop of henle concentrated?
Due to its length it is mostly in the medulla of the kidneys.
What part of the nephron is thicker?
The distal tube and collecting duct
Gomelular filtration
The plasma filtration here is said to be 100%
Proximal Tubule
Reabsorbs 70% of blood filtrate volume into the renal vein (back into cardiovascular system) = 126L out of 180L
Loop of Henle
Reabsorbs 20% of filtrate volume into renal vein.
Na+, K+, Cl- and Ca2+ ions are also reabsorbed into the lumen from the nephron (green arrow)
Distal Tubule
Reabsorbs 9% of remaining filtrate.
Na+, K+, Cl- and Ca2+ ions are also reabsorbed into the lumen from the nephron (green arrow)
Overall change in reabsorption % through different sections of the nephron
70% ( proximal tube)
20% (loop of henle)
9% (distal tubule)
Excretion
1% of total filtrate is excreted = 1.8L
This is why 2L of water is needed per day, for the kidney to function and filter the blood.
Homeostatic Control
Regulates final 10% of filtrate reabsorption.
Covered more in next deck
Hormonal Secretion
Regulates water and ion balance in kidneys.
Proximal tube secretions
H+ are secreted to acidify urine. Drugs and ureic acid are also secreted. This enables control of water and ions returning into the CVS
Distal tubule and collecting duct secretions
Urea and hormones are secreted into the urine. This enables control of water and ions returning into the CVS
Glomerular Filtration Rate (GFR)
Constantly maintained at 180 L/day as we constantly need to filter the blood to stay alive. Renal auto regulation maintains this.
Why does amount of urine change?
The reabsorpion changes depending on temperature, exercise, water and salt intake
Myogenic Autoregulation
Regulates GFR via arteriole pressure adjustments.
Does Mean Arteriole Pressure impact GFR
Mean Arterial Pressure changes due to things like exercise demands. However flow into glomeralus is constant when blood pressure is constant at 120/80mmHg
Renal Auto Regulation
Maintains constant GFR despite blood pressure changes.
The afferent arteriole has smooth muscle cells surrounding it which contract as part of an autonomic response when theur diameter increases. Maintenance of the diameter of the afferent and efferent arteriole keeps the GFR constant by maintaining MAP inside glomerulus.
Tubuloglomerular Feedback
Regulatory mechanism for glomerular filtration rate.
Vasoconstriction at Afferent arteriole
Arteriole carrying blood into the glomerulus
Efferent arteriole
Arteriole leaving the glomerelus - carries filtered blood from the glomerulus to the rest of the kidney and back into the body’s general circulation
Fluid Reabsorption
Water follows solutes by osmosis in nephron.
What 3 molecules does the proximal tubule reabsorb? (NOT A FILTRATE VOLUME Q)
Water (70% of the volume will be reabsorbed here)
Sodium ions
100% of glucose - proximal tubule is the only tissue with glucose transporters
Collecting Duct
Final site for urine concentration and secretion.
Interstitial Fluid
Fluid surrounding cells, important for reabsorption. It is similar to plasma and its ion concentration helps transfer ions from the nephron cells into the peritibular capillary cells.
Movement of filtrate from nephron lumen into peritubular capillary (membrane)
Contiued chemical gradient between all the plasma membranes help with reabsorption of ions and water.
Electrochemical gradient of ions (Na+, Cl- etc)
Inside the nephron lumen, there is a high concentration of ions as fluid has been pushed out into the bowman’s capsule compared to indide the proximal tubule cell. There is an electrochemical gradient across the tubular lumen side (apical) of the proximal tubule clel membrane.
Hydrostatic Pressure (PH)
Pressure exerted by fluids in the nephron.
Glomerular Filtration
Process of plasma filtration in kidneys.
Reabsorption of ions - step 1 of reabsoption
Ions enter the proximal tubule cell via epithelia channel protein (ENaC), moving down the electrochemical gradient (pasisve diffusion)
Reabsorption of H20 - step 1 (step 2 of reabsoption)
Water follows after ions into the proximal tubule cells down the osmotic gradient as the concentration of ions is higher inside the proximal tubule cell than the tubule lumen
Reabsoption of ions via active transport - step 2 of ion reabsoptio (step 3 of reabsoption)
Ions are actively pumped out to the inerstitial fluid via Na+/K+ ATPase pump i the membrane of the proximal tubule cells facing towards the peritibular capillary. Na+ is pumped out and K+ is brought in
Reabsorption of H20 - step 2 (step 4 of reabsorption)
H2O in the proximal tubule cell enters interstitial fluid via aquaporin channels in proximal tubule cell membrane as concentration of Na+ (any ion) is higher there due to it being actively transported.
Glucose Transporters
Proteins facilitating glucose reabsorption in kidneys - only in proximal tubule.
Aquaporin
Channel protein for water reabsorption - passive transport.
Electrochemical Gradient
Difference in ion concentration across membranes.
Na+/K+ ATPase Pump
Active transport mechanism for sodium and potassium.
Passive Transport
Movement of substances without energy use.
Osmotic Gradient
Difference in solute concentration driving water movement.
Reabsorption of glucose at the proximal tubule - step 1
Step 1 = glucose reabsorption with Na+
Na+ moving down its electrochemical gradient into proximal tubule cell from the tubule lumen via sodium-glucose transporter protein. This pulls glucose agaisnt its concentration gradient
This is a form of secondary active transport
Reabsorption of glucose at the proximal tubule - step 2
Glucose diffuses out of the basolateral side of the cell into the interstitial fluid using the glucose transporter protein = passive transport
Reabsorption of glucose at the proximal tubule - step 3
Na+ is pumped out by Na+/K+ ATPase pump
Reabsorption of glucose at the proximal tubule - step 4
K+ is let out by potassium leak channel
Renal Blood Flow (RBF)
Volume of blood flowing to kidneys.
Na+ Channel (ENaC)
Epithelial channel for sodium entry into cells.= passive transport
Potassium Ions (K+)
Ion exchanged with sodium during active transport.
Leak Channel
Channel allowing potassium to exit cells after being pumped in by ATPase
Glucose Reabsorption
Process of glucose retrieval from nephron lumen.
Sodium-Glucose Transporter (SGLT)
Protein that co-transports Na+ and glucose into cells = secondary active transport
Secondary Active Transport
Transport mechanism using energy from Na+ electrochemical gradient.
Glucose Transporter (GLUT)
Facilitates glucose diffusion out of cells.
Na+-K+-ATPase Pump
Active transport pump moving Na+ out, K+ in.
Basolateral Membrane
Membrane facing interstitial fluid in nephron cells.
Apical Membrane
Membrane facing nephron lumen in proximal tubule.
Active Transport
Energy-requiring movement against concentration gradient.
Secondary Active Transport
Uses an electrochemical gradient created by primary active transport to move other substances against their own gradients.
Epithelial Na+ Channel (ENaC)
Channel allowing Na+ entry via passive transport.
Filtration
Process of blood plasma entering Bowman’s capsule.
Secretion
Process of substances moving from blood to nephron.
Renal Autoregulation
Mechanisms maintaining stable GFR despite blood pressure changes.
Hydrostatic Pressure
Pressure exerted by fluid in glomerulus.
Organic Molecules
Includes glucose, amino acids, and waste products.
Vitamins and Trace Elements
Essential nutrients filtered into Bowman’s capsule.
Gas Exchange
Movement of O2 and CO2 in nephron filtration.
Potassium Leak Channel
Channel allowing K+ to exit nephron cells passively.
