Chapter 31 (Kidney) Flashcards
What does the urinary system consist of
- 2 Kidneys (blood is supplied to kidney via renal artery + leaves via renal vein)
- Bladder
- Ureter
- Urethra
Function of the kidneys
Responsible for filtering the blood to remove waste and toxic materials (excretory organ) , maintaining water potential of the blood. (osmoregulatory organ)
Function of urethra
passes urine from the bladder to the exterior of the body
Function of ureter
Passes urine from the kidney (pelvis) to the bladder
Sections of the kidney
Cortex
Medulla
Renal Pelvis
Structure & function of cortex
- Outer Region (contains many Bowman’s capsule + glomeruli)
- Site of ultrafiltration.
- EPO (cytokine) is made here
Structure & function of Medulla
- Inner Region
- Consists of renal pyramids
Structure & function of Renal Pelvis
- Central region
- collects urine from collecting ducts that converge into ureter
Causes of acute kidney failure
- Bacterial infections
- Kidney stones (or blockage within kidney)
- Medication side effects
Definition of acute kidney failure
Sudden onset, short duration.
Can usually be reversed once treated
Definition of chronic kidney failure
Slow onset, long duration.
Usually results in permanent damage if not diagnosed at early stage. (often Irreversible)
Causes of chronic kidney failure
- Hypertension - Damages epithelial cells of endothelium + basement membrane of Bowman’s capsule.
- Uncontrolled diabetes
- Genetic conditions eg, polycystic kidney disease
Warning signs of kidney disease
Blood in urine
Reduction in urine volume
Cloudy urine
Oedema ( swelling due to accumulation of tissue fluid) in hands, feet + areas around eyes.
Diagnosis of kidney failure
- Proteins in urine
- Erythrocytes in urine
- Leucocytes in urine
- High creatine levels in blood. ( a waste substance normally filtered from blood ). Higher levels = worse kidney damage
- Structural abnormalities identifies using CT/ ultrasound scans.
Consequences of kidney failure
–> Raised ion conc in plasma.
–> Build up of toxic urea in blood - Cell death
–> Hypertension, as water balance of blood is not regulated. Higher production of renin as response to low blood pressure in glomerulus.
–> Anaemia due to reduced EPO production (can be treated with RhEPO)
–> Loss of electrolyte balance ( accumulation of K+, Na +, Cl- ions alters osmotic balance of plasma, resulting in tissue and organ death.
–> weakened bones as calcium and phosphorus balance in blood is lost.
Transplants in the future
Use of patient’s own Pluripotent Stem Cells to ‘grow’ a kidney by Inducing them to produce kidney cells (iPSCs)
- Can produce organs with no antigens, so remove need for immunosuppressants
- embryonic stem cells also used to clone organs
Advantages of haemodialysis
- Medical professionals are present so lower risk of infection.
- daily dialysis not required
Disadvantages of haemodialysis
- Diet restrictions
- long periods of hospitalisation ( 3 times a week for several hours)
- Patients must travel to interrupts daily life.
Advantages of peritoneal dialysis
- Carried out at home
- Diet is less restricted
- No specialist equipment needed
- Patient remains mobile during treatment so daily life is less interrupted
Disadvantages of peritoneal dialysis
- Self-administered procedure -> higher risk of infection
- Requires daily dialysis
Advantages of dialysis
- No waiting list or time delay
- keeps patient alive until donor organ found
Disadvantages of dialysis
- not long term
- requires hospital visits
- Dietary restrictions required
Advantages of transplants
- Can prolong life significantly
- No dietary restrictions
- Over life duration, its has lower cost
- Free from lifestyle restrictions imposed by regular dialysis.
Disadvantages of transplants
- Risks with surgery
- High risk of post- surgical infection
- Immunosuppressants taken for life
- Shortage of donors
- Usually repeated after 10 years
Kidney Transplants Procedure
- Donated kidney from living or dead….. inserted into patient’s body
- Donor organ assessed for compatibility based on antigens CONTINUE
- Patient’s original kidney left in unless cancerous/risk of causing infection.
- Blood vessels + ureter joined into patient’s circulatory system + bladder.
- patient given immunosuppressants to prevent rejection
Haemodialysis process
- Blood leaves patient’s body from artery + flows through machine between partially permeable dialysis membrane
- Dialysis fluid flows on other side of dialysis membranes in opposite direction to maximise conc gradient between plasma + dialysis fluid
(Counter current exchange system) - Heparin added to prevent clotting
- All Urea + excess ions removed from plasma to dialysis fluid via diffusion down concentration gradient.
- Glucose + ions needed are added to dialysis fluid at conc that patient needs, to ensure no glucose / necessary ions diffuses out of plasma
- Filtered blood returned to patient’s body via a vein.
Function of dialysis
Remove excess molecules that would normally be removed by kidneys + add needed molecules
Definition of nephrons
The functional units of the kidney made from a collection of many specialised cells. (responsible for formation of urine)
Definition of selective reabsorption
Reabsorption of useful substances along the kidney nephron back into the blood
How to reduce rejections after transplants using therapeutic cloning
- Techniques can now more accurately match the tissue to antigens on RBC.
- Patient’s own stem cells can be used to form desired cells
- They wont be rejected as are seen as self
Definition of Excretion
The removal of unwanted products of metabolism from the body
Function of renal artery
Carries oxygenated blood to kidneys
Function of renal vein
Carries deoxygenated blood away from kidneys
Key Steps in urine production
- Ultrafiltration in Bowman’s capsule
- Selective reabsoprtion in proximal convoluted tubule
- Reabsorption in Loop of Henle
- Reabsorption in distal convoluted tubule
- Reabsoprtion of water in collecting duct.
Definition of ultrafiltration
Filtering of plasma at a molecular level (urea, water, glucose, ions, amino acids)
They are filtered out of blood capillaries into Bowman’s capsule
Afferent arteriole info
Blood flows into glomerulus (ARRIVES)
Efferent arteriole info
Blood flows away from glomerulus (EXITS)
What does the barrier between the blood in the capillary and the lumen of the Bowman’s capsule consist of?
- Endothelial cells in the capillaries separated by fenestrations –> PREVENT BLOOD CELLS ESCAPING
- Basement membrane of capillaries composed of mesh of collagen + glycoprotein –> PREVENTS LARGE PROTEINS BEING FILTERED OUT OF PLASMA
- Epithelial cells of Bowman’s capsule (podocytes) have finger-shaped projections to create small gaps (filtration slits)
4 sections of a nephron
Proximal convoluted tubule
Loop of Henle
Distal convoluted tubule
Collecting duct
What things are needed for ultrafiltration to occur
- Barrier to retain molecules over a certain size
- Pressure to force fluid out
What is the rate of ultrafiltration determined by
- Blood pressure generated in LV
- Constriction of the efferent arteriole. ( leads to build up of pressure in glomerulus)
Definition of selective reabsorption
Reabsorption of useful substances along the kidney nephron back into the blood
- Most occurs in proximal convoluted tubule
What is reabsorbed in the PCT
Lots of water, all glucose, some amino acids, some ions, vitamins.
How are the cells lining the PCT adapted
- Microvilli, on luminal edge of PCT, inc SA for reabsorption
- Co-transporter proteins enable facilitated diffusion of glucose + amino acids with sodium ions
- High conc of mitochondria to produce ATP to release energy for active transport
- Basal membrane contains sodium-potassium pumps to pump sodium ions out of PCT cells into tissue fluid.
Definition of osmoregulation
The regulation of the water potential of body fluids
What are aquaporins
membrane-spanning channel proteins that inc permeability of collecting duct wall. They allow more water to diffuse through but prevent passage of ions.
What is ADH
Anti-diuretic hormone
- small protein
- responsible for osmoregulation
- made in hypothalamus but stored + released from post-pituitary gland
- occurs via negative feedback
Endocrine function of kidney
- Production of erythropoietin ( EPO)
- Production of angioteniogenase (renin)
Production of erythropoietin info
- EPO is secreted from kidney when oxygen levels in blood are low.
- Stimulates production of erythrocytes from bone marrow
Production of angioteniogenase (renin) info
- Renin is secreted by kidney in response to low blood volume + pressure
- It catalyses conversion of angiotensinogen to hormone angiotensin
- Angiotensin inc blood pressure by vasoconstriction, stimulating more ADH to be produced, activating thirst reflex in hypothalamus
How does body gain water eg.
Drinking
Eating
Respiration
How does body lose water eg.
Urinating
Sweating
Breathing
Function of LoH
-Create high conc of salts (Na+ & Cl-) in tissue fluid of Medulla to act as a counter current multiplier
-This maximises conc gradient to maximise exchange + efficiency of hairpin.
_ reabsorption of water occurs in medulla region
- allow production of conc urine
Does the size of the LoH matter
The longer the LoH , the more conc the urine becomes, which allows a greater conc of ions to be built up in medulla.
Why can blood pressure fall in the glomerulus
Due to: dehydration High blood loss Heart attack Obstruction of the afferent arteriole or renal artery
Peritoneal dialysis info
The patient’s own abdominal membrane acts as the dialysis
Blood returning to the patient after passing through the dialysis machine will have….
Decrease in urea concentration
Decrease in ions
Unchanged glucose
Unchanged protein composition and concentration
How does kidney disease cause anaemia
- Kidney no longer produces sufficient EPO
- Fewer RBC produced
- Blood can be lost during haemodialysis
- RBC may also be filtered into the urine.
How does kidney disease cause cardiovascular disease
Caused by increased production of renin.
Renin catalyses the conversion of angiotensinogen to angiotensin.
Which increases blood pressure resulting in hypertension
This then causes damage to the endothelium in the arteries causing atherosclerosis.
Peritoneal Dialysis steps
Dialysis fluid introduced to abdomen using a catheter. . Dialysis fluid pumped into peritoneal cavity.
Fluid remains in abdomen for several hours to allow exchange of urea, excess ions and water to take place across peritoneal membrane.
Urea and excess ions diffuse out of capillaries into tissue fluid into dialysis fluid.
Dialysis fluid removed from abdomen and discarded.
What are podocytes?
specialized epithelial cells that cover the outer surfaces of glomerular capillaries.
