Urinary Flashcards
What is the position in the body of the Kidneys?
They are Retroperitoneal organs. Left Kidney runs from T11-L2, Right Kidney runs from T12-L3. Lower due to the presence of the Liver on the right side of the body.
What are the 4 layers of External protection the kidney has?
- Pararenal Fat (Posterior Kidney)
- Renal Fascia (Encloses Kidney + Adrenal Glands)
- Perirenal Fat
- Renal Capsule (Tough Fibrous layer)
Describe the Drainage of the kidney
Drains through the pyramids into the Calyx, a few of these merge to form Major Calyx, a few Major Calyx form the Renal Pelvis. It then drains to the bladder via the ureters through the renal hilum
Describe the Arterial Supply of the Kidneys
Renal arteries enter through the renal Hilum, divides into segmental arteries which divide further to interlobar which run along either side of each of the pyramids. Theses divide further into the Arcuate artery which divide further to form interlobular arteries. These divide finally to form Afferent arterioles
Whats the difference in the path of the Ureters in Males + Females?
- In females they pass under the uterine arteries
- In men they pass under the Vas Deferens
At what point are you most likely to get stones lodges in the Ureters?
In the Uteropelvic junction, Pelvic brim where it enters the pelvis, Entrance to the bladder
What is the blood supply of the Ureters?
Branches of common + internal iliac arteries and uterine arteries
What are the main structures of the Bladder?
- Apex - Located superiorly pointing towards the pubic symphysis, anchored by the median umbilical ligament
- Body - The main part of the bladder located between the apex + Fundus
- Fundus/Trigone - triangular shape between two ureters + Urethra
What is the main muscle of the Bladder?
Detrusor muscle
Whats the difference between Urinary Sphincters in males + females?
Both sexes have an External Urethral Sphincter under voluntary control. Males have an Internal Urethral Sphincter under autonomic control to prevent seminal regurgitation
Describe the male Urethra + the 4 parts its divided up into
Approximately 15-20cm long
- Pre-Prostatic - Begins at the internal urethral orifice at neck of the bladder + ends at the Prostate
- Prostatic - Passes through the Prostate gland, the ejaculatory ducts and prostatic ducts drain here
- Membranous - Passes through the pelvic floor + deep perineal pouch, its surrounded by the external urethral sphincter.
- Spongy - Passes through the bulb + corpus spongiosum of the penis ending at the external urethral orifice
What is the Cloaca?
The common cavity at the end of the digestive tract
Describe the development of the kidney with the 3 kidney systems
- Pronephros - Never functional in humans, Pronephric duct extends from cervicle region to the Cloaca. It drives development of Mesonephros
- Mesonephros - The Mesonephric tubules + Mesonephric duct make up the embryonic kidney. Mesonephric duct sprouts the Ureteric bud which induces the development of the definitive kidney.
- Metanephros - Ureteric bud induces development of definitive kidney within intermediate mesoderm. Ureteric bud contacts mesanephric blastema + expands and branches producing the minor + major calyx’s
Describe the ascent of the Kidney
It first appears in the pelvic region + undergoes a caudal to cranial shift crossing the arterial fork formed by vessels returning blood from the foetus to the placenta. As it ascends it creates new blood supplies + looses the lower ones, this is why you can have extra blood supplies to the kidney
What can go wrong with the ascension of the Kidney?
- Renal Agenesis - Ureteric bud fails to interact with the mesoderm intermediate and kidney fails to form
- Splitting of Ureteric bud - This can produce extra lobes in the kidney or extra urethral openings, if these are bencher the external sphincter of bladder can cause incontinence
- Multi-cystic Kidney disease - Atresia (narrowing) of ureter prevents it from functioning correctly causing spontaneous abortion due to lack of amniotic fluid
- Horseshoe Kidney - This happens if two kidneys become to close together during the ascent, they become fused and get stuck under the Inferior Mesenteric Artery
What are the two different types of Nephron and whats the difference between them?
- Cortical Nephrons - 90% of nephrons. Located in outer cortex with shorter Loop of Henle + small glomerulus
- Juxtamedullary Nephrons - Located on edge of cortex next to the Medulla. They have large Glomeruli + long Loop of Henle. Efferent arteriole leads to Vasa Recta which runs countercurrent along side of loop of Henle
What 3 layers makes up the Filtration Barrier?
- Capillary Endothelium - Permeable to Water, Salts + Glucose
- Basement Membrane - Acellular gelatinous layer of collagen + glycoproteins. It is permeable to small proteins however the glycoproteins are negatively charged which glee’s to repel the movement of proteins
- Podocyte layer - Pseudopodia interdigitate to form Filtration Slits (Slit Diaphragms), this layer is Permselective which means it filters on size
How does the body maintain a normal Glomerular filtration rate at different blood pressures?
Auto regulation using the contraction + relaxation of Afferent + Efferent arterioles
What is Tubular Glomerular Feedback? What chemicals are released to induce vasoconstriction + vasodilation?
The distal tubule lies between the Afferent + Efferent Arterioles. An increase in arterial pressure results in an increased glomerular capillary pressure and an increased GFR. Increased GFR leads to increase in Na + Cl ions conc. in the DT. Macula Densa cells in the DT detect the rise in Cl via conc. dependant salt uptake through the NaK2Cl co-transporter. This then stimulates the Juxtaglomerular apparatus to release chemicals.
- Adenosine is released to promote Vasoconstriction
- Prostaglandins are released to promote Vasodilation
What has been reabsorbed by the end of the Proximal Convoluted Tubule?
- 100% Filtered nutrients
- 67% Filtered Na+
- 65% Filtered Water, Cl, K
Describe the Co-transport of Glucose into the Proximal Convoluted Tubule
Na-K ATPase on basolateral membrane pumps Na into interstitial space to create Na gradient. 2 Na ions + 1 Glucose molecule are transported into tubular cell against the Glucose concentration gradient by the Sodium Glucose Transporter SGLUT. Glucose leaves the tubular cell on the basolateral side by facilitated diffusion
Describe the secretion of Organic Cations
Na/K ATPase pumps Na out of the basolateral membrane producing an electrochemical gradient which allows positive OC’s to diffuse in down their concentration gradient. Na/H anti porter on luminal membrane pumps H+ into the lumen driven by the low Na in the cell. OC’s are then secreted into the lumen by the H-OC exchanger.
Give some examples of important Cations + Anions
- Cations (Ach, Dopamine, Adrenaline, Histamine, Morphine, Atropine, Sulphonamides)
- Anions (Urate, Bile salts, Penicillin, NSAIDs)
What is Renal Clearance?
Renal clearance of a substance is the volume of plasma that is completely cleaned of a substance by the kidney per minute.
What sort of substance do you need to calculate GFR? What is the gold standard to measure GFR? What can be used as a replacement + why is it not as good?
- Freely filtered, Non Secreting, Non Reabsorbed
- Inulin is best to calculate accurately
- Creatinine can be used but is slightly secreted so produces an overestimate
What is Filtered Load? How is it calculated?
- Amount of a substance that is freely filtered that enters the renal tubule over a given amount of time
- Plasma concentration x GFR
What is Renal Threshold?
Plasma concentration where Transport maximum is reached and substance begins to spill into the urine
What 4 main things control medium + long term BP?
- Renin Angiotensin Aldosterone System - Renin is released from Granular cells of the Juxtaglomerular apparatus, the release is stimulated by; Reduced NaCl delivery to the DT, Reduced perfusion detected by baroreceptors in the afferent arteriole, Sympathetic stimulation to the juxtaglomerular apparatus.
- Sympathetic Nervous System - High levels of Sympathetic Innervation causes constriction of the arterioles reducing GFR. Activates Na/H exchanger on apical membrane of the PCT + increases activity of Na/K ATPase increasing Na reabsorption. Stimulates the release of Renin from Juxtaglomerular apparatus.
- Antidiuretic Hormone (ADH) - Increases presence of Aquaporin channels in the collecting duct to increase water absorption. Stimulates Na reabsorption by stimulating Na/K/Cl co-transporter. The release of ADH is stimulated by an increase in plasma osmolarity or in cases of severe Hypovolaemia.
- Atrial Natriuretic Peptides - Cause vasodilation of Afferent arteriole which increases GFR, also inhibits the reabsorption of Na along the nephron. They are synthesised + stored in atrial myocytes + released in response to stretch. Low pressure sensors means that with less stretch you have less released.
Describe the Activation of Angiotensinogen
Angiotensinogen –(Renin)–> Angiotensin I –(Angiotensin Converting Enzyme)–> Angiotensin II
What are the affects of Angiotensin II?
- Vasoconstriction of arterioles
- Stimulates Na reabsorption in the kidney (Stimulates Na/H exchanger in the apical membrane of PCT)
- Increased release of NA in the sympathetic nervous system
- Stimulates the release of Aldosterone
- Increases thirst sensation
What affect does Aldosterone have on the Kidney?
Acts on principal cells of the collecting duct. Activates Epithelial Na channels (ENaC), apical K+ channels + increases the basolateral Na extrusion via Na/K ATPase. This increases the reabsorption of Na + water
Other than the conversion of Angiotensin I to Angiotensin II how does ACE help to increase BP?
Breaks down Bradykinin which is a vasodilator so reduction of the presence of Bradykinin causes an increase in the Vasoconstriction effect
Why are Prostaglandins important in the kidney?
Act as vasodilators, important as they act as a buffer to excessive vasoconstriction caused by the sympathetic nervous system + RAAS. They enhance GFR and reduce reabsorption of Na
How can NSAID’s be dangerous to the Kidney?
Inhibit the production of prostaglandins. Administration of these drugs when renal perfusion is compromised can further reduce GFR which can lead to Acute Renal Failure
What is the difference between Primary + Secondary Hypertension?
- Primary is when there is no definable source of hypertension. This accounts for 95% of primary hypertension
- Secondary is when there is a clear cause for the hypertension that can be treated
Give 3 main causes of Secondary Hypertension
- Reno-vascular Disease - Occlusion of the renal artery causes a fall in renal perfusion. This leads to increased Renin production and activation of RAAS to increase Na retention
- Renal Parenchymal Disease - Damage to the parenchymal cells, at early stages of hypertension may be due to a loss of the vasodilator substances Dopamine + Prostaglandins. Later due to reduced GFR
- Adrenal causes
- Conn’s Syndrome (Aldosterone secreting Adenoma - causes hypertension + Hypokalaemia)
- Cushing’s Syndrome (Excess secretion of Glucocorticoid Cortisol acts on aldosterone receptors)
- Phaeochromocytoma (Tumour of adrenal medulla causing secretion of catecholamines Adrenalin + NA)
What are the 4 main pharmacological treatments for Hypertension?
- Targeting RAAS - ACE Inhibitors prevent production of Angiotensin II, Angiotensin II receptor antagonists
- Diuretics
- Vasodilators - L-type Ca Channel blockers - Reduce Ca entry to vascular smooth muscle cells causing relaxation, α1 receptor blockers - reduce sympathetic tone causing relaxation
- β Blockers - Blocking β1 receptors reduces effects of sympathetic output of the heart reducing HR + contractility
How is salt intake described?
Hedonistic Appetite (Regulatory appetite), a deficiency drives a need for it
Describe the affect of ADH
Causes vasoconstriction of arterioles. Increases Na, K + Cl absorption in the thick ascending limb, this produces a hypo-osmotic solution at the top of the ascending limb which increases absorption in the collecting tubule. In cortical collecting duct water reabsorption is increased as is K+ secreting. In medullary CD water + urea reabsorption increases
Describe how changes in blood pressure + volume effect how the body deals with changes in Osmolarity. Why is this?
- Reduced extra cellular volume - Set point for osmolarity is set to be lower, so even if you have a low osmolarity the body will continue to absorb H2O to prevent circulatory collapse.
- High BP - Set point is shifted to a higher osmolarity so less ADH is secreted even at high osmolarity.
The shifts in set point are because the blood volume is more important than osmolarity
What problems can there be with ADH secretion?
- Diabetes Insipidus - Where the pituitary gland doesn’t produce enough ADH or there is an acquired insensitivity of the kidney to ADH. Due to the low amount of ADH water isn’t adequately reabsorbed so large amounts of ruin is produced
- Syndrome of Inappropriate ADH Secretion (SIADH) - This is characterised by excessive release of ADH from the posterior pituitary gland or another source. This causes Hyponatremia (Low Na) due to increased secretion (ADH works on DCT + CD to retain water but not solute) + increase in total bodily fluid due to low secretion of water
What is an effective osmole?
Molecule that doesn’t diffuse across the membrane easily _ doesn’t have any transporters that easily transport it from one side of the membrane to the other
How is the Counter Current Gradient produced? How is it maintained? Describe the involvement of the Vasa Recta
- Ascending Limb is impermeable to water but permeable to NaCl + Urea. As urea is high conc. in interstitium it means Na + Cl can leave into medulla as urea enters (Urea then reabsorbed from the medullary collecting duct) Na is being pumped out of the ascending limb which raises the oncotic pressure outside + lowers it inside.
- Water flows out of the descending limb down the osmotic gradient raising oncotic pressure inside the tubule.
- Fresh fluid enters glomerulus pushing conc. fluid round into ascending limb where Na is pumped out into interstitium again.
- By the 3rd round the interstitial conc. is 700mOsm/L
- Its produced by the Loop of Henle but is maintained by the Vasa Recta which acts as a counter current multiplier.
- Descending limb of Vasa Recta - Blood is initially isosmotic. It runs past the Ascending limb where the interstitial conc. of Na, Cl + Urea is V. high. These diffuse into the Vasa Recta increasing the osmolarity.
- Ascending limb of Vasa Recta - Initially has a V. high osmolarity due to the high conc. of Na, Cl + urea. Due to the high osmolarity water flows in from the descending limb of the Loop of Henle.
Where is Calcium reabsorbed in the Kidney?
98% is reabsorbed
- 65% in proximal tubule coupled with Na + water
- 20% in ascending loop of Henle
- 15% in DCT
