ILA 9 - Renal Flashcards
What is in the renal tract?
Urinary tract = kidneys, ureters, bladder, urethra
Describe the anatomy of the kidneys
- Retroperitoneally from T12-L3
- Renal capsule, perirenal fat, renal fascia, pararenal fat
- Outer cortex and inner medulla
- Contains renal pyramids, at apex is called the renal papilla
- Each renal papilla has a minor calyx which collects urine from the pyramids, several merge to form a major calyx, urine passes through these to form a major calyx into the renal pelvis to the ureter and bladder
Describe the anatomy of the ureter
- 2 thick tubes, 25 cm long
- Smooth muscle, contracts to produce peristaltic waves = propels urine to the bladder
- continuation of renal pelvis, ureteropelvic junction is the narrowing
- drains into bladder
3 narrow sections = ureteropelvic junction, pelvic brim (where it crosses external iliac), and vesico ureteric junction (just before enters the bladder)
Describe the anatomy of the bladder
Apex, body, fundus, neck
- enters via ureters, exits via urethras
- Trigone = smooth walls
Muscles
- Detrusor - smooth, contracted during mituation
- Internal urethral sphincter - smooth, contracted during filling (closes during male ejaculation)
- External urethral sphincter - skeletal, contracted during filling
Describe the anatomy of the urethra
In women - 4cm long, has two para-urethral mucous glands (Skene’s)
In men - longer, 4 parts
1) Preprostatic part, 1cm contains internal urethral sphincter, smooth muscle
2) Prostatic part, 3-4cm, surounded by prostate gland, contains ridge called urethral crest,
3) Membranous part - contains external urethral sphincter (voluntary)
4) Spongy part - contain within corpus spongiosum (because pressure is lower), forms two bulbous widenings
Describe the anatomy of the prostate (in men)
Prostate lies immediately inferior to the bladder and posterior to the pubic symphysis, surrounding the urethra
-30-40 glands that all discharge into the urethra forming semen
Describe the structure of a nephron - what are the types and their differences
1) Cortical nephron.
Renal corpudcle is further into the cortex.
Henle’s loops do not extend deep into the medulla (sometime they do not have them)
2) Juxtamedullary - about 15% of all nephrons
Renal corpuscle sits near the medullally-cortical junction.
Henle’s loops extend deep into the medulla. (These are responsible for the reabsorption of water by generating an osmotic gradient)
Also have long capillaries that loop deeply into medulla
What are the causes of acute kidney injury?
a) pre-renal
b) post-renal
c) renal
a) pre-renal = severe blood loss and low bp due to major surgery, infection or injury, NSAIDS, ACE inhibitors, severe burns, pancreatitis
b) post-renal = kidney stones in urethras, enlarged prostate, bladder that doesn’t empty properly, blood clots in urethras or ureters, cancer of prostate/cervix/colon
c) renal = glomerulonephritis, acute tubular necrosis
What are the common causes of chronic renal failure?
-Diabetes (1 or 2)
-Obesity
-Hypertension
-Polycystic kidney (genetic)
NSAIDS
What are the major complications of chronic renal failure?
- Fluid retention, lead to swelling and edema (if albumin is lost from the blood)
- Hyperkalemia (K+ isn’t being excreted), can impair heart function
- CVD, increased renin = hypertension = damage heart muscle
- Weak bones (Levels of Ca and phosphorus are abnormal, low Ca = PTH = Ca taken from bones = weaker bones)
- Anemia (kidneys will secrete then erythropoietin if they are damaged, so less RBCs made)
- Damage to CNS (due to urea build up, and others)
Which organs lie retroperitoneally?
S- Suprarenal glands A- Aorta (& IVC) D - Duodenum 2/3 P - Pancreas U - urethra C - colon K - kidneys E - esophagus R - rectum
What is the renal hilum?
Deep fissure - Where the renal vessels and ureter enter/exit the kidney
What is the vasculature of the kidney
- Renal arteries (direct from aorta), distol to superior mesenteric artery
- Each enters via the renal hilum, dividing into segmental branches, they then undergo further divisions to supply the renal parenchyma
- R and L renal veins, empty into IVC
Describe the divisions of the vasculature of the kidneys
- Renal artery (from aorta)
- Segmental arteries
- Interlobar arteries (pass through cortex)
- Arcuate arteries
- Interlobar arteries
- Afferent arterioles = form glomerulus = filtration :)
- Glomerular capillaries
- Efferent arterioles
- Peritubular capillaries
- Interlobular veins
- Arcuate veins
- Interlobar veins
- Renal vein (directly into IVC)
What is the vasculature supply of the ureters
Abdominal = renal artery and testicular/ovarian artery Pelvic = superior and inferior vesical arteries
What is the nervous supply of the ureters
Via renal, testicular/ovarian and hypogastric plexuses
-Sensory via T11-l2 (this is where ureteric pain is referred to)
Describe the vasculature of the bladder
-Majority internal iliac vessels, delivered by superior vesical branch
In males - supplemented by inferior vesical artery
In females - supplemented by vagina lateries
in both sexes small amounts from inferior gluteal arteries
-Venous drainage = vesical venous plexus. empty into internal iliac vein
What is the nervous supply of the bladder
Symp = hypogastric nerve, T12-L2 (relaxation of detrusor muscle during filling)
Parasym = pelvic nerve, S2-S4 (cause contraction of detrusor = micturition)
Somatic = voluntary control, pudendal nerve (S2-S4) innervates external urethral sphincter, can cause constriction (filling) or relaxation (micturition)
Sensory = found in bladder wall and signal need to urinate
What is the bladder-stretch reflex?
Primitive spinal reflex
- stretch = micturition
- this is over ridden when toddlers are toilet trained (and spinal injuries)
Reflex arc = bladder fills with urine and stretches, stretch is transmitted to spinal cord, interneurons relay signal to parasym, efferents (pelvic nerve)
pelvic nerve contracts the detrusor muscle to stimulate micturition
Where does glomerular filtration take place?
Renal corpuscle = Bowman’s capsule and glomerulus
About 20% of blood is filtered as it flows from afferent to efferent arteriole
Bowman’s space contains the protein-free fluid filtered from the glomerulus
What 3 layers separate glomerulus and bowman’s space
- Capillary endothelium
- Basal lamina
- Single celled lining of Bowman’s capsule - podocytes
What forces oppose filtration and which favour it?
Favours - Glomerular capillary hydrostatic blood pressure
Opposes - Osmotic force due to proteins in the plasma (tends to pull water into system)
Opposes - Hydrostatic pressure due to proteins in Bowman’s capsule (very low)
=Glomerular capillary pressure is highest :)
How can afferent/efferent blood vessels increase GFR?
Afferent dilates, efferent constricts = higher hydrostatic pressure, higher rate
(for a lower rate (symp), the afferent constricts and the efferent dilates)
Average GFR?
180L/day
What is osmotic pressure?
minimum pressure which needs to be applied to a solution to prevent the inward flow of water
Oncotic pressure
Oncotic pressure, or colloid osmotic pressure, is a form of osmotic pressure exerted by proteins, notably albumin, in a blood vessel’s plasma (blood/liquid) that usually tends to pull water into the circulatory system.
RAAS
- Renin(enzyme) is secreted by juxtaglomerular apparatuses in afferent arterioles.
- Renin catalyses the conversion of angiotensinogen (from the liver) to angiotensin I. (10aa)
- ACE then catalyses the conversion of angiotensin I to angiotensin II. (8aa) ACE is found on the luminal surface of pulmonary capillary endothelial cells
- Angiotensin II stimulates the secretion of aldosterone from the adrenal cortex, and the constriction of arterioles
- Aldosterone means that Na+ (and therefore H20) is retained and not excreted leading to an increase in bp
- Aldosterone stimulates Na+ reabsorption by distal and cortical collecting ducts, it induces the synthesis of all channels and pumps in cortical collecting duct
no aldosterone = approx 2% of na+ is excreted
high aldosterone = all na+ reabsorbed - Vasoconstriction also leads to an increase in bp
What is the juxtaglomerular apparatus?
The juxtaglomerular apparatus consists of three cells:
the macula densa, a part of the distal convoluted tubule of the same nephron
juxtaglomerular cells, which secrete renin
extraglomerular mesangial cells
Describe the mechanism of vasopressin on the luminal membrane
- When vasopressin is released into the interstitial fluid it binds to its receptor on the basolateral membrane
- This increases the production of cAMP
- cAMP activates the protein KINASE (PKA)
- Kinase phosphorylates proteins that increase the rate of fusion of vesicles containing AQP2 with luminal membrane
- This leads to an increase in the number of AQP2s into the luminal membrane
- Therefore there is a greater diffusion of water along the conc grad through the aqua porins into the collecting duct cells
- Water then diffuses through the AQP3 and AQP4 channels into the interstitial fluid then into the blood
(Vasopressin has no affect on AQPs on basolateral membrane) - ACTS ON COLLECTING DUCTS
