URINARY* CH 23 Flashcards
Identify 4 (/8) functions of the kidneys
- Filter blood and excrete wastes
- Regulate blood volume and pressure
- Regulate electrolytes and pH
- Clear hormones from the blood
- Detoxify free radicals
- Secrete Erythopoietin to synthesize RBCs
- Secrete Calcium to regulate calcium levels
- Synthesize glucose from amino acids in starvation
What is BUN? What is the medical term for an elevated BUN and what could it indicate?
Blood Urea Nitrogen (the amount of urea nitrogen in the blood)
- Azotemia is a high urea nitrogen concentration; our kidney’s function is to lower these levels and these high concentrations indicate renal damage
Define excretion and identify the four systems that carry this out
Excretion is the process by which we eliminate wastes outisde of our body
- Urinary
- Respiratory
- Integumentary
- Digestive
What are the structural and functional units of the kidney?
Nephrons
List the pathway of fluid through the urinary system
Glomerular Capsule
PCT
Nephron Loop
DCT
Collecting Duct
Papillary Duct
Minor Calyx
Major Calyx
Renal Pelvis
Ureter
Urinary Bladder
Urethra
A - Afferent Arteriole
B - Efferent Arteriole
C - Glomerulus
D - Glomerular Capsule
E - PCT
F - Nephron Loop (descending and ascending limbs)
G - DCT
H - Collecting Duct
Juxtamedullary vs Cortical Nephrons
Which is more numerous?
Which one maintains the osmotic gradient?
Juxtamedullary - VERY long nephron loops get close into the renal medulla (~15% of nephrons); maintains osmotic gradient
Cortical - Short nepphron loops dip slightly into the renal medulla (~85% of nephrons)
What is the name of the capillary network associated with juxtamedullary nephrons? What is the function?
Vasa Recta; this allows us to have more concentrated urine because we reabsorb some of the water from the nephron loop though this capillary network. This leave our urine more concentrated because it has less water but is letting out lots of waste
Is the pressure in the glomerulus high or low? Why?
HIGH;
This allows waste products to leave down their concentration/pressure gradient into the glomerular space
Identify and describe the stages of urine development
Glomerular Filtration - The high pressure in the glomerulus allows waste products to leave and create a plasmalike filtrate of the blood
Tubular Reabsorption - Removes useful solute from the filtrate and returns them into the blood
Tubular Secretion - Removes harmful or waste solute from the blood and takes them into the nephron
Water Conservation - Removes excess water from urine to return to the blood (works to ensure that we are keeping enough water in our body)
Is glomerular filtration active or passive? What is this pressure called?
Passive; hydrostatic pressure forces fluids through the filtration membrane
What type of tissue lines the capillaries of the glomerulus? What is the function or purpose of this specific tissue?
Fenestrated Endothelium is highly permeable but products have to be small enough to pass through the little spaces
What type of molecules can freely pass through the filtration membrane in glomerular filtration?
Identify four examples
Any molecule smaller than 3nm;
ex: water, electrolytes, amino acids, glucose, vitamins
Proteinuria and Hematuria; why does this happen and why is it dangerous?
Proteinuria - Albumin in urine
Hematuria - Blood in urine
This is caused by damage to the filtration membrane (which in a healthy person albumin and RBCs are normally too large to pass through the membrane) (this is dangerous because we lost important substances from our blood )
Define and describe Net Filtration Pressure (NFP)
We have an outward filtration pressure in the glomerulus that causes waste products to exit into the glomerular space (BLOOD HYDROSTATIC PRESSURE). However, as we pump these out we build a concentration that wants to go in and follow its concentration/pressure gradient (HYDROSTATIC PRESSURE IN CAPSULAR SPACE and COLLOID OSMOTIC PRESSURE).
The combination of these forces is described as the Net Filtration Pressure. It has a slight outward pressure that is monitored and kept to make sure thing get pushed out but not so much that they want to enter back in
Define Glomerular Filtration Rate (GFR); What factors is this directly proportional to?
The amount of filtrate formed per minute by the two kidneys combined
- NFP: The slight outward pressure that draws solutes out of the glomerulous and into the glomerular space
- Surface area available for filtration
- Filtration membrane permeability
What are the mechanisms of high and low GFR (how does it occur) and how does the body respond to these levels?
High GFR: Fluid flows through renal tubes too rapidly for reabsorption and causes us to lose more electrolytes and can lead to dehydration
Low GFR: Wastes are reabsorbed and can lead to azotemia (high levels of urea nitrogen)
Our bodies can respond to these levels by regulating glomerular blood pressure (through three different levels described in another flashcard)
How does GFR affect blood pressure?
High GFR leads to increased urine output which lowers blood pressure
Low GFR leads to urine retention whihc increases blood pressure
We can adjust GFR through chnaging the glomerular blood pressure which is affected by which three mechanisms (DO NOT DESCRIBE THEM)
Sympathetic Control
Hormonal Control
Renal Autoregulation
SHR (Sure)
Describe renal autoregulation and identify the two mechansims that allow this
The ability of the nephrons to adjust their own blood flow and GFR without external control
- Myogenic Mechanism
- Tubuloglomerular Feedback
Briefly describe the Myogenic Mechanism and describe the role of the afferent arteriole in this renal autoregulation
Regulating blood flow based on the stretching and contraction of smooth muscle
When arteriole blood pressure increases the afferent arteriole is stretched. The muscle recognizes this response and reacts by consticting and regulating blood flow to the glomerulus
When arteriole blood pressure falls the afferent arteriole relaxes. The muscle recognizes this response and reacts by dilating and regulating blood flow to the glomerulus
What cells are involved in the juxtaglomerular apparatus? What do they do and how do they respond to chnaging GFR?
Macula Densa - When we have high GFR, we have more NaCl. They absorb excess NaCl and secrete ATP to stimulate nearby granular cells
Granular Cells - When triggered by the ATP, they constrict afferent arterioles, lower blood flow, and thus lowering and correcting GFR
What molecule is found in the granules and granular cells?
Renin
How does the sympathetic system impact GFR?
The sympathetic nervous system works through epinephrine to constrict afferent arterioles. This allows our body to redirect blood from the kidneys to the heart, brain, and skeletal muscle
(fight or flight)
