Urinary system Flashcards
What are the functions of the kidneys?
Urine formation - maintains PH Endocrine + metabolic: - Erythropoietin - renin - vitamin d - gluconeogenesis
Structure of the kidney?
kidney bean shape and colour Lateral border convex medial border concave
Structures entering the hill of the kidney?
renal vein renal artery renal pelvis (ureter)
What are the supporting tissues of the kidney?
renal fascia perinephric fat fibrous capsule
Location of the kidney?
Rt Kidney T3 Lt kidney T2
What is the peritoneum relation to the kidney?
retro-peritoneum
Label the kidney
Arterial supply to the kydney
- Renal arteries
- Arise from aorta at the level of L1/2 IVD
- Rt renal a. slightly longer than Lt
•
•Upon entering the renal sinus, each artery divides into smaller branches:
•
•Segmental aa àinterlobar aa àarcuate aa àcortical radiate aa àafferent arterioles àglomerular capillaries
What is the venous supply to the kidney
•Renal veins
•
- Each renal vein is formed by 5-6 interlobar veinsthat unite at the hilum
- Lt renal v. is longer than Rt
- Runs over ant. surface of aortato the IVC
•
•Lt renal v. is joined by the Lt suprarenal v. & Lt gonadal v.before draining into theIVC
What is the renal blood flow pathway?
What is the lymphatic drainage to the kidney ?
para aortic nodes near the origin of the renal arteries
What is the nerve supply to the Kidney
- Parasympathetic: CN X Vagus
- Sympathetic: T10 - 12 splanchnic nn
- Visceral afferents
What is the nephron
Basic functional unit.
a collection of tubes and blood vessels that help to concentrate urine
Function: Blood filtration and urine formation
List the key components of the nephron?
Renal corpuscle
- glomerulus
- glomerular (Bowman’s) capsule
renal tube and collecting ducts
- proximal convoluted tubule
- nephron loop (loop of Henle)
- distal convoluted tubule
- collecting tube
Label the Nephron key components
Describe the collecting ducts of the Kidney
- •Each collecting duct receives filtrate from many nephrons
- •Collecting ducts give the pyramids their striated appearance
- •Passage through the medulla allows for final adjustments to urine concentration & content
- The ducts fuse together and deliver urine to the minor calyces via the renal papilla
What are the types of nephrons and what are their 3 main differences?
Cortical nephrons (short loop of Henle)
- short nephron loop
- glomerulus further from the cortex
- peritubular network name: peritubular capillary
Juxtamedullary nephron
- Long nephron loop
- Location: glomerulus closer to cortex
- peritubular network name: Vasa recta
What is the Juxtaglomerular apparatus and its relevant cell to osteos?
•A region where the most distal portion of the loopofHenlelies against the afferent (and sometimes efferent) arteriole its glomerulus
LEARN:
Juxtaglumeral cells located in walls: contain granules of renin, BP low, cell releases granules and starts the renal system.
What is the urine composition?
95% water
5% solutes
What are abnormal findings in urine composition?
- blood proteins,
- WBCs (pus),
- bile pigments,
- glucose, ketone
What are the 3 steps of urine formation?
- Glomerular filtration
- Tubular reabsortion:
- Tubular secretion
What is glomerular filtration?
- Occurs in the renal corpuscle
- Produces a cell-free and protein-free filtrate
- Filtrate formation: a passive process that relies on net outwards pressure from the glomerular capillaries into the capsular space
WHat us the GFR and how is it calculated?
Glomerular filtration rate
•volume of filtrate formed each minute by the kidneys.
Normal GFR >90ml
Mid-loss 60-90ml
Kidney failure <15
What are the factors affecting filtration?
Net filtration pressure (BP) - only one we can affect.
Surface area available
FIltration membrane permeability
What is the myogenic Mechanism
Intrinsic regulation of GFR
vascular smooth muscle relaxes if it is stretched.
- •High systemic BP:afferent arterioles constrict to limit NFP and prevent glomerular damage
- •Low systemic BP: afferent arterioles dilate
what is the tubuloglomerular mechanism?
•Initiated by macula densa cells (chemoreceptors sensitive to NaCl concentration of filtrate)
- •High GFR:not enough time for reabsorption of NaCl from filtrate
- •MD cells detect the high NaCl and release adenosine (induces vasoconstriction of afferent arterioles)
- Intrinsic regulation
What is the Intrinsic regulator that involves prostaglandin?
- Produced by renal cells (tubules & medulla) and has a paracrinefunction
- Maintains GFR by inducing vasodilation of afferent arterioles
What is the hormonal mechanism ?
Extrinsic mechanism
•Activation of the RAAS occurs when systemic BP (and consequently GFR) is low
- •Juxtaglomerular cells releaserenin
- •Renin catalyses a cascade that increases systemic BP, renal perfusion and GFR
What are the neural controls for GFR?
extrinsic regulation
•Sympathetic nervous system acts upon kidneys when systemic BP is low (baroreceptor reflex)
- •Renal sympathetic nerves activate B1-adrenergic receptors on juxtaglomerular cells
- •Renin release catalyses a cascade that increases systemic BP, renal perfusion and GFR
What is the process of reabsorption?
•Selective reclaiming of filtrate components (return from tubule back to the blood)
- •Active processes: primary & secondary active transport
- •Passive processes: osmosis, diffusion, facilitated diffusion
What is the ANTIDIURETIC HORMONE?
- Released by the posterior pituitary in response to increased ECF osmolarity (dehydrated state)
- Increases the permeability of the DCT & CD to water, by inserting aquaporins (water channels) into the apical membrane of tubule cells
- ADH release is reduced in the overhydrated state
- Caffeine and alcohol inhibit the release of ADH
What is aldosterone used for?
- Released by the cortex of the adrenal gland as part of the RAAS (initial stimulus: low blood pressure)
- Aldosterone is also released in response to hyperkalaemia
- Aldosterone enhances the (active)reabsorption of Na+at the DCT & CD
- Reabsorption of Na+is coupled to K+secretion
What is the process of secretion and what substances are secreted?
- Movement of selected substances from the peritubular capillaries through the tubule cells into the filtrate
- Some substances (e.g. HCO3-) are synthesised by tubule cells and secreted directly.
- •Certain drugs
- •Undesirable metabolites reabsorbed by passive processes
- •Excess K+
- •Acids and bases (depending on blood pH)
What are the ureters?
Muscular tubes that convey urine from the kidney to the bladder.
Location: they run from the abdomen to the renal pelvis to the pelvis, and enter the posterolateral of the bladder. they follow the bifurcation of the iliac artery and in men cross the vast efferents.
Whats the nerve supply to the ureters?
NERVE SUPPLY
- Sympathetic: T10 – L2 via renal, coeliac and hypogastric plexuses
- Parasympathetic:Pelvic splanchnic nn, S2 - S4
- Visceral afferents
Introduce the bladder?
Location:
- When empty it is situated within the entire pelvic cavity
- As it distends it domes up into the abdominal cavity (a full bladder may even reach the level of the umbilicus)
- Lies in front of the rectum (M) or vagina (W)
Structure:•A hollow organ with strong muscular walls
Function:
- Serves as a temporary reservoir for urine:
- Moderately full bladder holds 500mL
- Max. capacity 800-1000 mL
Label the outside of the bladder
Label the inside of the bladder
What is the histology of the bladder?
MUCOSA
•Bladder is lined with transitional epithelium that is thrown into numerous folds (rugae) in the relaxed state
MUSCULARIS
- The smooth muscle of the bladder is referred to as detrusor muscle (L. ‘to thrust’)
- Three layers of smooth muscle
- •Inner and outer layers of longitudinally arranged mm fibres
- •Middle layer of circular arranged mm fibres
- •These layers may be difficult to identify in the cadaver
ADVENTITIA
•Variable amounts of perivesical fat
What is the nerve supply to the bladder?
- Nerves from the vesical plexus, which is continuous with the hypogastric plexus
- Parasympathetics: pelvicsplanchnicn (S2-S4)
- Motor supply to detruser mm and inhibitoryto the internal urethral sphincter
- Sympathetics (T10 - L2)
- Visceral afferents
What is the vascular supply of the bladder?
Artery
- •Branches of the internal iliac aa:
- •Superior vesical aa - supply the anterosuperior parts of the bladder
- •Supply to fundus & neck: inferior vesical aa(M) or vaginal aa (F)
Venous
- •The names of the veins correspond to the names of the arteries
- •They are tributaries of the internal iliac vein
What is the prostatic urethra?
Only exists in male
- Serves both urinary & reproductive function
- ~20 cm long (much longer than the female urethra)
- Extends from the bladder neck to the urethral orifice at the tip of the penis
- Passes through the prostate and the entire corpus spongiosum
- The urethra runs closer to the anterior surface of the prostate
- Receives the openings of the ejaculatory ducts (the union of the vas deferens and ducts of the seminal vesicles bilaterally)
Histology of the penile urethra?
Mucosa: transitional epithelium
Muscularis: urethral smooth muscle.
What is the female urethra?
- Serves a urinary function only
- Is relatively short ~4cm (greater incidence of urinary tract infections in females)
- A straight muscular tube which passes in an anteroinferior direction from the bladder neck to the external urethral orifice (EUO is anterior to the vaginal orifice and posterior to the clitoris)
- Most of the urethra is embedded within the anterior vaginal wall
- The walls of the urethra are in contact except during urination
Female urethra histology?
Mucossa: stratified squamous
Parautheral glands: Lubtication
What is micturition?
Urinating
has three steps
- •Contraction of the detrusor muscle
- •Relaxation of the IUS
- •Relaxation of the EUS
