Module 9 - Urinary

Question 1

Components

Answer 1

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

Question 2

Functions

Answer 2

Functions
Regulation of blood ionic composition
Maintains blood osmolarity
Regulates blood volume and pressure
Regulates pH
Endocrine secretion
Excretes waste and foreign substances

Question 3

Kidneys

Answer 3

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

Question 4

Kidney - External Anatomy

Answer 4

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

Question 5

Internal Kidney Anatomy

Answer 5

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

Question 6

Kidneys - blood supply

Answer 6

Kidney Blood Supply
Blood enters – Renal Artery
Blood Exits – Renal Vein

Question 7

Blood Flow of Filtration

Answer 7

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

Question 8

Nephron

Answer 8

Functional unit in cortex of kidneys
Cleanse blood and balance constituents of circulation
Renal Corpuscle
Renal Tubule
Collecting duct

Question 9

Renal Corpuscle

Answer 9

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

Question 10

Renal Tubule

Answer 10

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)

Question 11

Proximal convoluted tubule (PTC)

Answer 11

Proximal convoluted tubule (PTC) – first section of renal tubule – most reabsorption from filtrate – Water, electrolytes, and nutrients

Question 12

Loop of Henle

Answer 12

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

Question 13

Distal convoluted tubule (DCT)

Answer 13

Distal convoluted tubule (DCT) – final section – fine-tuning of urine composition – sodium and potassium balance

Question 14

Collecting Duct

Answer 14

Collecting duct – large duct – receives filtrate from multiple nephrons – regulates water reabsorption to produce concentrated urine – drains into pelvis of kidney

Question 15

Main Functions of Urine Production

Answer 15

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

Question 16

Glomerular Filtration

Answer 16

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))

Question 17

NFP - breakdown

Answer 17

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

Question 18

Glomerular filtration rate

Answer 18

Glomerular filtration rate (GFR) – amount of filtrate formed by both kidneys per minute – 125ml/m – 180L/day

Question 19

Filtration Membrane

Answer 19

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

Question 20

Filtration Membrane - Fenestrated glomerular endothelium

Answer 20

Fenestrated glomerular endothelium – inner most layer
Endothelial cells with tiny pores (fenestrae) – allow small molecules to pass

Question 21

Filtration Membrane - Basement membrane

Answer 21

Basement membrane – middle – thick acellular layer – selective barrier – connective tissue

Question 22

Filtration Membrane - Podocytes

Answer 22

Podocytes – specialized epithelial cells – help together by pedicels – filtration slits
Pedicels – finger-like projections – extending from cell body – interdigitate with podocytes

Question 23

Renal Autoregulation

Answer 23

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

Question 24

Renal Autoreg - Myogenic Mechanism

Answer 24

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

Question 25

Renal Autoreg - Tubuloglomerular feedback

Answer 25

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

Question 26

Neural Regulation

Answer 26

Neural regulation – Sympathetic Nervous System triggers norepinephrine – reduces filtrate formation to shunt blood to vital organs

Question 27

Hormones Decreasing Renal Blood Flow

Answer 27

Hormonal regulation Decreasing renal blood flow Epinephrine Angiotensin II

Question 28

Hormonal regulation - Decreasing renal blood flow - Epinephrine

Answer 28

Epinephrine – constricts afferents and efferent – blood flow is taken away from kidneys during fight of flight response

Question 29

Hormonal regulation - Decreasing renal blood flow - Angiotensin II

Answer 29

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

Question 30

Hormones Increasing Renal Blood Flow

Answer 30

Increase renal blood flow Atrial natriuretic peptide (ANP) Prostaglandins

Question 31

Hormonal Regulation - Increasing Renal blood flow - ANP

Answer 31

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

Question 32

Hormonal Regulation - Increasing Renal blood flow - Prostaglandins

Answer 32

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

Question 33

Reabsorption

Answer 33

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

Question 34

Reabsorption - cells or transport

Answer 34

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

Question 35

Reabsorption - Proximal

Answer 35

Proximal convoluted tubule – 65% reabsorb – Na+ transporter proteins Ions – Na+, K+, Cl-, Ca+, Mg+, Bicarbonate Water Amino acids Glucose – only place Urea

Question 36

Reabsorption - Loop

Answer 36

Loop further adjusted – 15% Thin descending – H2O reabsorbed – H2O concentrates urine Thick ascending – Ions, bicarbonate

Question 37

Reabsorption - Distal

Answer 37

Distal convoluted tubule – 15% - depending on body’s needs Ions, bicarbonate, and H20

Question 38

Reabsorption - Collecting Duct

Answer 38

Collecting duct – 5% Na+, Cl-, Bicarbonate, water, and urea

Question 39

Secretion

Answer 39

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

Question 40

Urine Concentration - Loop of Henle

Answer 40

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

Question 41

Urine Concentration - Collecting Duct

Answer 41

Collecting duct – collects left over Water Urea – kidneys like to hold on to increase osmolarity to drive more water reabsorption in loop of Henle

Question 42

Urine Concentration - ADH

Answer 42

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

Question 43

Urine Concentration - Diluting

Answer 43

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

Question 44

Urine Concentration - Concentrated

Answer 44

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

Question 45

Nephron Control - RAAS

Answer 45

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

Question 46

Nephron Control - Angiotensin II

Answer 46

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

Question 47

Nephron Control - Aldosterone

Answer 47

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

Question 48

Nephron Control - ADH

Answer 48

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

Question 49

Nephron Control - ANP

Answer 49

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

Question 50

Urine Drainage

Answer 50

Urine drainage Papillary ducts Minor calyx Major calyx Unite to form renal pelvis Ureters Bladder Urethra Toilet

Question 51

Ureters

Answer 51

30cm long – from kidneys to bladder Retroperitoneal Urine drains from calyces to pelvis to become ureters – thru hilum of kidneys

Question 52

Ureters - Inner Mucosa

Answer 52

Inner mucosa transitional epithelium – stretchy tissue – expands with urine scattered goblet cells that secret mucus

Question 53

Ureters - Muscularis

Answer 53

Muscularis layer longitudinal & circular smooth muscle – Peristaltic contractions Moves urine down – help of hydrostatic pressure and gravity

Question 54

Ureters - Serosa

Answer 54

Serosa – Fibrous coat Anchors b/w parietal peritoneum & posterior ab wall Loose adventitial layer – collagen and fat

Question 55

Bladder

Answer 55

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

Question 56

Bladder - Mucosa

Answer 56

Mucosa – Transitional epithelium – stretching – rugae Rugae – folds and wrinkles – bladder collapse Rugae – flat – expend and store

Question 57

Bladder - Muscularis

Answer 57

Muscularis – Detrusor muscle – contacts to expel urine – relaxes to store Reduces size of organ when emptying Fibres run in all directions

Question 58

Urethra

Answer 58

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