Module 9 - Urinary Flashcards
Components
Components
Two kidneys - filters
Two ureters – transport urine from kidneys to bladder
Urinary Bladder – collection point from ureters
Urethra – transport urine from bladder to outside – disposal
Functions
Functions
Regulation of blood ionic composition
Maintains blood osmolarity
Regulates blood volume and pressure
Regulates pH
Endocrine secretion
Excretes waste and foreign substances
Kidneys
Paired kidneys – retroperitoneal organs
Hilum – vertical fissure – centre of concave medial border – ureter leaves – nerves, blood & lymph vessels enter and exit
External Covering - 3 layers
Internal structure
Kidney - External Anatomy
External – 3 layers of tissue
Innermost renal capsule – covering – fibrous, dense, irregular connective tissue – maintains shaped – protection
Adipose capsule – renal fat pad – cushion – shock-absorbing – separates kidneys from abdominal wall muscles
Outer renal fascia – tough tissue – firmly anchors kidney to abdominal wall
Internal Kidney Anatomy
Internal
Cortex – functional – outer region – below renal capsule - Contain blood vessels and tubes – light red colour
Medulla – inner region – deep to cortex - Contains renal pyramids
Pyramids – functional – inside medulla - Tissues that create urine
Papillae – protections of pyramids that drains into minor calyx
Columns – extensions of the cortex – separates pyramids
Calyces
Minor Calyx – collecting pool that receives urine from papilla
Major Calyx – collecting of minor calyx – connect to pelvis
Pelvis – funnel – hollow area in center – urine collects - Urine flows from pelvis to ureters – out of kidneys
Kidneys - blood supply
Kidney Blood Supply
Blood enters – Renal Artery
Blood Exits – Renal Vein
Blood Flow of Filtration
Flow for filtration
Descending abdominal aorta – Renal Artery – branching
Segmental arteries – come in and start branching towards lobes
Lobar arteries – b/w lobes
Arcuate arteries (curved vessels) – Turn corner – around pyramid
Branches off into cortex – lobular arteries
Branches no longer arteries – afferent arterioles – become nephrons
Nephron
Functional unit in cortex of kidneys
Cleanse blood and balance constituents of circulation
Renal Corpuscle
Renal Tubule
Collecting duct
Renal Corpuscle
Renal corpuscle – initial filter – blood filtration
Glomerulus – cluster of tiny blood vessels – blood filtered – fluid and small molecules pass into Bowman’s capsule
Afferent arterioles – blood in
Efferent arterioles – carry blood away – forming peritubular capillaries
Bowman’s capsule – surrounds glomerulus – cup-shaped – collects filtered fluid
Renal Tubule
Peritubular capillaries – surrounds renal tubule – reabsorption of substances back to blood– constantly exchanging fluid and substances
Renal Tubule – reabsorption and secretion of substances to form urine – filtered fluid passes
Proximal convoluted tubule (PTC)
Loop of Henle
Distal convoluted tubule (DCT)
Proximal convoluted tubule (PTC)
Proximal convoluted tubule (PTC) – first section of renal tubule – most reabsorption from filtrate – Water, electrolytes, and nutrients
Loop of Henle
Loop of Henle – hairpin-shaped – extends into medulla – maintains concentration necessary for urine concentration
Descending limb of loop – highly permeable to water – water move out of filtrate
Ascending limb of loop – reabsorbs sodium and chloride ions – diluting filtrate
Thin – passive reabsorbs sodium & chloride
Thick – actively pumps Na, K, and Cl out – transport proteins
Distal convoluted tubule (DCT)
Distal convoluted tubule (DCT) – final section – fine-tuning of urine composition – sodium and potassium balance
Collecting Duct
Collecting duct – large duct – receives filtrate from multiple nephrons – regulates water reabsorption to produce concentrated urine – drains into pelvis of kidney
Main Functions of Urine Production
Urine Production
Filtration – into nephron circulation
Blood passes through glomerulus – glomerular filtrate
Reabsorption – reabsorb 99% of fluid – sent back into blood
Renal tubule constantly pushing out fluid as it passes through
Distal convoluted tubule reabsorbs water, Na+, Cl, and Ca+
Aldosterone can tell DCT to reabsorb more sodium
Secretion – to be sent out of body – back into tubule
Tubules dispose of drugs and metabolites
Eliminate undesirable substances that were passively reabsorbed – urea and uric acids
Glomerular Filtration
Net filtration pressure – 10mm Hg – sum of osmotic and hydrostatic pressure – overall pressure that drives fluid out of a capillary – net force causing fluid to filter through the capillary wall into Bowman’s capsule
a positive NFP – fluid will be filtered out of the glomerular capillaries and into Bowman’s capsule – forming urine
NFP = Glomerular Blood hydrostatic pressure (GBHP) – (Capsular hydrostatic pressure (CHP) + Blood colloid osmotic pressure (BCOP))
NFP - breakdown
NFP = Glomerular Blood hydrostatic pressure (GBHP) – (Capsular hydrostatic pressure (CHP) + Blood colloid osmotic pressure (BCOP))
GBHP – pressure exerted by blood w/in glomerular capillaries – pushing fluid out
CHP – pressure exerted by fluid already in Bowman’s capsule – opposing filtration
BCOP – pressure exerted by plasma proteins in the blood – pulling fluid back into capillary
Glomerular filtration rate
Glomerular filtration rate (GFR) – amount of filtrate formed by both kidneys per minute – 125ml/m – 180L/day
Filtration Membrane
Filtration Membrane – acts as a filter – separated small molecules from blood plasma to form urine - prevents cells, large proteins, and negatively charged ions to pass
Fenestrated glomerular endothelium
Basement membrane
Podocytes
Filtration Membrane - Fenestrated glomerular endothelium
Fenestrated glomerular endothelium – inner most layer
Endothelial cells with tiny pores (fenestrae) – allow small molecules to pass
Filtration Membrane - Basement membrane
Basement membrane – middle – thick acellular layer – selective barrier – connective tissue
Filtration Membrane - Podocytes
Podocytes – specialized epithelial cells – help together by pedicels – filtration slits
Pedicels – finger-like projections – extending from cell body – interdigitate with podocytes
Renal Autoregulation
Renal Autoregulation – maintain
constant GFR
Protects kidneys from
High blood pressure injury
Allows kidneys to clean metabolic waste and recover
nutrients & electrolytes
Myogenic Mechanism
Tubuloglomerular feedback
Renal Autoreg - Myogenic Mechanism
Myogenic mechanism – smooth muscle contract – reducing GFR
High blood pressure will stim – too much stretching of walls in will result in contraction of afferent & efferent arterioles – reducing blood flow through glomerulus – reducing GFR
Renal Autoreg - Tubuloglomerular feedback
Tubuloglomerular feedback – macula densa cells in distal convoluted tubule watching sodium concentration –
Macula densa cells – chemoreceptors – monitor sodium and chloride – distal tubule at juxtaglomerular apparatus – release adenosine
Apparatus – where distal loops around near glomerulus
Decreases osmolarity of filtrate – low Na+ & Cl – stim macula densa cells – vasodilation of afferent arterioles – increase blood flow into glomerulus – GFR++
Increase osmolarity – macula densa cells stim contraction of afferent arterioles – GFR lowers
Neural Regulation
Neural regulation – Sympathetic Nervous System
triggers norepinephrine – reduces filtrate formation to shunt blood to vital organs
Hormones Decreasing Renal Blood Flow
Hormonal regulation
Decreasing renal blood flow
Epinephrine
Angiotensin II
Hormonal regulation - Decreasing renal blood flow - Epinephrine
Epinephrine – constricts afferents and efferent – blood flow is taken away from kidneys during fight of flight response
Hormonal regulation - Decreasing renal blood flow - Angiotensin II
Angiotensin II – response to low blood pressure – final product of renin-angotensin-aldosterone – low blood pressure stims renin – converted into angio I by ACE (angiotensin converting enzyme) – angiotensin II travels to blood – binds to receptors on afferent and efferent vessels – constrict – increase resistance
Hormones Increasing Renal Blood Flow
Increase renal blood flow
Atrial natriuretic peptide (ANP)
Prostaglandins
Hormonal Regulation - Increasing Renal blood flow - ANP
Increase renal blood flow
Atrial natriuretic peptide (ANP) – blood volume increases, atria releases ANP – cause kidneys to lose Na+ and H20 – lowering blood pressure – b/c of increase cardiac workload – pressure on atrial walls – result in dilation of afferent = more blood in – constriction of efferent = less blood leaves
Hormonal Regulation - Increasing Renal blood flow - Prostaglandins
Prostaglandins – produced by kidneys – stim by
sympathetic - result in dilation of afferent = more
blood in – constriction of efferent = less blood leaves
– maintains some flow during fight or flight response
Reabsorption
Reabsorption
View what’s in the nephron as “outside the body”
Exchange with surrounding capillaries
Renal tubule is to slow down filtration process and to constant
double check concentration of substances and water
GFR is so high that fluid entering proximal tubule is greater
than total plasma volume
Reabsorption – taken back to bloodstream – reabsorbing from
urine – maintain fluid and electrolyte balance
Reabsorption - cells or transport
Reabsorption – taken back to bloodstream – reabsorbing from
urine – maintain fluid and electrolyte balance
Thru epithelial cells lining in tubules
Active transport
Passive – Diffusion and osmosis
Reclaims essential substances – water, glucose, aminos, and
electrolytes from filtrate
Reabsorption - Proximal
Proximal convoluted tubule – 65% reabsorb – Na+ transporter proteins
Ions – Na+, K+, Cl-, Ca+, Mg+,
Bicarbonate
Water
Amino acids
Glucose – only place
Urea
Reabsorption - Loop
Loop further adjusted – 15%
Thin descending – H2O reabsorbed – H2O concentrates urine
Thick ascending – Ions, bicarbonate
Reabsorption - Distal
Distal convoluted tubule – 15% - depending on body’s needs
Ions, bicarbonate, and H20
Reabsorption - Collecting Duct
Collecting duct – 5%
Na+, Cl-, Bicarbonate, water, and urea
Secretion
Secretion
Helps control blood pH
Things in the blood back into tubule
Waste products and excess substances sent away for elimination
Proximal – Urea, uric acid, creatinine, H+, drugs, ammonia (result of deamination of aminos – review metabolism notes)
Loop – Urea
Distal – H+, drugs, ammonia
Removed substances excess in blood – Na+, K+, H+, & Ca+
Active transport and passive diffusion
Waste – creatinine, ammonia, and uric acid
Urine Concentration - Loop of Henle
Loop – solute and water reabsorption
Descending – water - passive
Ascending – ions – active transport – pumping
ions into medulla
Countercurrent multiplication – descending
and ascending go in opposite direction
When we reabsorb ions – make
medulla salty – drives water to be reabsorb passively
Urine Concentration - Collecting Duct
Collecting duct – collects left over
Water
Urea – kidneys like to hold on to increase osmolarity to drive more water reabsorption in loop of Henle
Urine Concentration - ADH
ADH – signals kidneys to reabsorb more water from urine
Insertion of aquaporin water channels into cell membrane – increases water reabsorption back to blood
High levels of ADH = more concentrated urine – b/c of increase water reabsorption
Low levels of ADH = diluted urine and increased output
Urine Concentration - Diluting
Diluting Urine – eliminating water
ADH not present
Collecting duct is less permeable to water – most of filtrate to remain in tubule and excreted – volume of dilute urine increases
Loop – thick ascending limb – active pumps Na+, K+, and Cl- out of filtrate – concentration rises in medulla – drawing water out
Urine Concentration - Concentrated
Concentrated Urine – conserve water
ADH is present – binds to receptors in collecting duct
Aquaporin channels are inserted – increasing water reabsorption from filtrate
Loop – Countercurrent multiplication – establishes osmotic gradient in medulla
Actively pumps Na+ and Cl- ions out of ascending limb
Hypertonic environment in medulla – draws water out of the descending limb – concentrating filtrate
Urea recycling – inner medulla
Urea actively transported into collecting duct – high osmolality of interstitial fluid – facilitating water reabsorption
Nephron Control - RAAS
RAAS – renin-angiotensin-aldosterone system – stimulate drop in blood volume and pressure
Macula densa sense low fluid or low Na+ - chemoreceptors – measure concentration
Macula cells tell Juxtaglomerular cells secrete renin – baroreceptors – b/c pressure drop
Kidney releases enzyme renin into blood
Liver releases angiotensinogen into blood
Renin activates – angiotensin I – gets to lungs
ACE – angiotensin-converting enzyme contacts pulmonary blood
Converts to Angiotensin II – widespread vasoconstriction – blood backs up & increase BP
Nephron Control - Angiotensin II
Angiotensin II – constricts blood flow – increase blood pressure w/ sodium retention
Result from renin-angiotensin-aldosterone system chain (RAAS)
Increased filtration rate – constricts efferent arterioles – increases GFR and sodium
Stims adrenal cortex to release aldosterone
Travels to hypothalamus – Triggers ADH
Nephron Control - Aldosterone
Aldosterone – sodium reabsorption – increase blood pressure with sodium retention
Steroid hormone
Acts on distal convoluted tubule and collecting duct – bring sodium back to body
Promoting sodium reabsorption and potassium secretion – sodium goes, water follows
Increases blood volume and pressure
Binds to receptors in distal tubule – epithelial cells – increases sodium channels in lumen membrane – facilitating sodium reabsorption in membrane
Nephron Control - ADH
ADH – water reabsorption
Synthesized in hypothalamus
Released by posterior pituitary gland
Stim – body detects low blood volume or high solute concentration (dehydration)
Binds to receptors in collecting ducts
Promotes recovery of water
Decreases urine volume
Maintains plasma osmolarity and blood pressure
Alcohol – inhibits – increase urine flow
Nephron Control - ANP
ANP – Atrial Natriuretic Peptide – promotes sodium and water excretion
promotes urine production (diuresis) – inhibiting sodium reabsorption
Antagonist to RAAS – Inhibits release of renin and aldosterone
Inhibits sodium reabsorption in collecting duct
Dilates the afferent arterioles – increasing GFR
Stimed by atrial walls being stretched b/c increase blood volume
Released causing vasodilation
Urine Drainage
Urine drainage
Papillary ducts
Minor calyx
Major calyx
Unite to form renal pelvis
Ureters
Bladder
Urethra
Toilet
Ureters
30cm long – from kidneys to bladder
Retroperitoneal
Urine drains from calyces to pelvis to become ureters – thru hilum of kidneys
Ureters - Inner Mucosa
Inner mucosa
transitional epithelium – stretchy tissue – expands with urine
scattered goblet cells that secret mucus
Ureters - Muscularis
Muscularis
layer longitudinal & circular smooth muscle – Peristaltic contractions
Moves urine down – help of hydrostatic pressure and gravity
Ureters - Serosa
Serosa – Fibrous coat
Anchors b/w parietal peritoneum & posterior ab wall
Loose adventitial layer – collagen and fat
Bladder
Bladder
Hollow organ in pelvic cavity
Stores and expels urine
Urine drains from ureters to bladder
Expels from urethra to exit body
Internal urethral sphincter – opening to urethra – circular fibers of muscularis
Sensory and motor input from ANS
3 tissue layer
Mucosa - Rugae
Muscularis
Serous Coat - peritoneum
Bladder - Mucosa
Mucosa – Transitional epithelium – stretching – rugae
Rugae – folds and wrinkles – bladder collapse
Rugae – flat – expend and store
Bladder - Muscularis
Muscularis – Detrusor muscle – contacts to expel urine – relaxes to store
Reduces size of organ when emptying
Fibres run in all directions
Urethra
Urethra
Tube leading from bladder to outside of body
Discharges urine
Males – ejaculation of semen as well
Micturition – voiding – urination
Increasing volume triggers stretch receptors of bladder
Transmits impulse for spinal micturition reflex
Ages affects – old or very young
Males
Longer – 16-22cm
Pass prostate gland
Exit thru penis
Females
Short
Exits thru vaginal region
