1. The urinary system – an overview
2. Embryonic development – kidney systems
3. The kidneys:
� topography and macroscopic anatomy
� microscopic anatomy – the nephron
� blood supply and innervation
4. Renal anomalies
Urinary system 1
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
The urinary system
2
� The urinary system, systema urinaria
� excretion of the end products
of the metabolic activities – urine
� The urinary organs, organa urinaria:
� kidney, ren:
� renal calyces – minor and major
� renal pelvis
� ureter, ureter
� urinary bladder, vesica urinaria
� urethra, urethra:
�male urethra, urethra masculina
� female urethra, urethra feminina
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Prof. Dr. Nikolai Lazarov 3
Embryonic development
� Embryonic origin – from common mesodermal ridge (intermediate mesoderm): � urogenital ridge
� mesonephric ridge – lateral part
� Kidney system:
� pronephros, Gr. pro-, earlier + nephros, kidney
� the earliest nephric stage in humans
� in the cervical region of the embryo
� nephrotomes – begin 4 we.
� induction by the intermediate mesoderm �
via transcription factors Lim-1 and Pax-2
� disappear by the end of the 4th we.
� mesonephros, Gr. “middle kidney” (Wolffian body)
� begin – 4 we., caudally to the pronephros
� mesonephric (Wolffian) duct
� metanephros, definitive (permanent) kidney
� appears in the 5th we. in the pelvis –metanephric diverticulum (ureteric bud)
� metanephric mesoderm – blastemao growth factors FGF-2, BMP-7 and LIF
� ureteric bud � collecting system (ducts)
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov 4
Embryonic development
� Embryonic origin – from common mesodermal ridge (intermediate mesoderm): � urogenital ridge
� mesonephric ridge – lateral part
� Kidney system:
� pronephros, Gr. pro-, earlier + nephros, kidney
� the earliest nephric stage in humans
� in the cervical region of the embryo
� nephrotomes – begin 4 we.
� induction by the intermediate mesoderm �
via transcription factors Lim-1 and Pax-2
� disappear by the end of the 4th we.
� mesonephros, Gr. “middle kidney” (Wolffian body)
� begin – 4 we., caudally to the pronephros
� mesonephric (Wolffian) duct
� metanephros, definitive (permanent) kidney
� appears in the 5th we. in the pelvis –metanephric diverticulum (ureteric bud)
� metanephric mesoderm – blastemao growth factors FGF-2, BMP-7 and LIF
� ureteric bud � collecting system (ducts)
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov 5
Embryonic development� Embryogenesis of the urinary bladder and urethra:
� anorectal canal – posterior part of the cloacal membrane
� urogenital sinus, sinus urogenitalis:
� the upper part � urinary bladder
o the allantois � urachus
� the middle portion
o the prostatic and membranous
parts of the male urethra
o the whole female urethra
� the lower (phallic) part
o the spongy part of the male urethra
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
Kidney, ren
6
� Kidney, ren (Gr. nephros):
� a paired organ
� excretory function:
� end metabolites
� excess water
� endocrine function:
� erythropoietin - red blood cell formation
� renin – control of blood pressure and volume
� 1,2,5-hydroxycholecalciferol –control of the calcium metabolism
� Kidneys in situ:
� in the lumbar region
� in the posterior abdominal cavity,
on the posterior abdominal wall
� in the retroperitoneal tissue
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
Macroscopic anatomy
7
� Kidney overview:
� shape – bean-shaped
� two extremities:
o superior and inferior extremity
� two surfaces and two margins:
o anterior and posterior surface
o lateral and medial margin
� renal hilum � renal sinus � renal calyces
� size:
� 10-13 (~12) cm long
� ~6 cm wide
� ~3 cm thick
� weight – 150 g (♂); 135 g (♀);
1/240 of the body mass
� color – reddish
� renal consistency – a parenchymal organ
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Prof. Dr. Nikolai Lazarov 8
Topography of the kidney
� Renal surface projections:
� the posterior abdominal wall
� 12th thoracic vertebra
� 1st and 2nd lumbar vertebrae
� right kidney –1-2 cm inferior to the left
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
Kidney attachments
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� Renal capsules:� renal capsule, capsula fibrosa
� adipose capsule �
pararenal fat
� renal fascia (of Gerota), fascia renalis – two layers
� prerenal fascia
� retrorenal fascia
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Prof. Dr. Nikolai Lazarov 10
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
Imaging anatomy
CT and MRI at the level of renal hilum
� conventional radiography
� echography (ultrasonography)
� computed tomography (CT)
� magnetic resonance imaging (MRI)
11
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Prof. Dr. Nikolai Lazarov 12
Renal relations
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Prof. Dr. Nikolai Lazarov 13
� Kidney structure:
� the renal cortex, cortex renalis – 5-10 mm:
� outer reddish brown-colored part
� granular appearance:
o pars convoluta
o pars radiata (cortex juxtamedullaris)
o lobulus corticalis
� the renal medulla, medulla renalis:
� much lighter-colored inner part
� renal pyramids,
pyramides renales – 7-20 (12):
o basis pyramidis
o papilla renalis � sinus renalis
o foramina papillaria � area cribrosa
� renal columns, columnae renales (Bertini)
� renal lobes, lobi renales
General renal structure
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Prof. Dr. Nikolai Lazarov 14
� The nephron, nephronum – 1-2 million:
� renal corpuscle (of Malpighi), corpusculum renale (Malpighi)
� the renal tubules:� proximal (first) convoluted tubule,
tubulus contortus proximalis� U-shaped thin segment (loop of Henle),
tubulus atenuatus (ansa nephroni)o descending limb, pars descendenso ascending limb, pars ascendens
� distal (second) convoluted tubule, tubulus contortus distalis
� collecting tubule, tubulus renalis colligens:
o straight tubule (pars recta) and convoluted tubule (pars convoluta)
� Types of neuphrons:� cortical or subcapsular nephrons,
nephronum breve (corticale)
� intermediate, nephronum intermedium� juxtamedullary nephrons,
nephronum longum (juxtamedullare)
Microscopic anatomy
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Prof. Dr. Nikolai Lazarov 15
� Renal corpuscle (of Malpighi), corpusculum renale (Malpighi) –number – 2 million, diameter 200 µm:
� cortical glomerulus (80%) andjuxtamedullary (20%)
� a tuft of capillaries, glomerulus– rete capillare glomerulare (mirabile)
� vascular pole, polus vascularis
� urinary pole, polus tubularis
� afferent arteriole, vas afferens
� efferent arteriole, vas efferens
�mesangium
� renal or Bowman’s capsule, capsula glomeruli (Bowman)
� visceral lamina, paries interna
� parietal lamina, paries externa
� capsular (urinary) space, lumen capsulae
Microscopic anatomy
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
Blood-urine barrier
16
� The kidney filtration apparatus –semipermeable barrier – glomerular filtrate = 170 l. primary urine:
� fenestrated capillary endothelium, lamina fenestrata
� endothelial cells, endotelocyti fenestrati
o 0.04-0.1 µm pores (fenestrations) with an absent diaphragm
� glomerular basement membrane, membrana basalis – 30 µm
� lamina rara interna
� lamina densa
� lamina rara externa
� visceral layer ofBowman’s capsule
� podocytes, podocyti – 20-30 µm
o pedicels (foot processes), cytotrabecules and cytopodia
o filtration slits – 20-30 nm
o filtration slit membrane
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
Blood-urine barrier
17
� The kidney filtration apparatus –semipermeable barrier – glomerular filtrate = 170 l. primary urine:
� fenestrated capillary endothelium, lamina fenestrata
� endothelial cells, endotelocyti fenestrati
o 0.04-0.1 µm pores (fenestrations) with an absent diaphragm
� glomerular basement membrane, membrana basalis – 30 µm
� lamina rara interna
� lamina densa
� lamina rara externa
� visceral layer ofBowman’s capsule
� podocytes, podocyti – 20-30 µm
o pedicels (foot processes), cytotrabecules and cytopodia
o filtration slits – 20-30 nm
o filtration slit membrane
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
The mesangium
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� Mesangium (Gr. mesos, middle, + angeion, vessel):� mesangial cells, mesangiocyti
� in islets, insulae perivasculares masangii� supporting role – produce the glomerular matrix� contractile and phagocytic function� contain receptors for angiotensin ІІ, ANF� synthesize IL-1 and PDGF
� extraglomerular mesangial (‘lacis’) cells – ‘polar cushion’; the juxtaglomerular apparatus
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
The renal tubules
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� proximal convoluted tubule, tubulus contortus proximalis:
� length 15 µm; width 50-60 nm
� parts:� initial part, neck
� convoluted tubule, pars convoluta
� straight tubule, pars recta
� simple columnar epithelium� brush border � microvilli
� basal striations
� reabsorption of water and electrolytes, amino acids, sugarsand polypeptides
� distal convoluted tubule, tubulus contortus distalis:� shorter and wider
� parts:� straight segment, pars recta
� convoluted, pars convoluta
� simple cuboidal epithelium� striations � short microvilli
� reabsorption of Na, K and water
� juxtaglomerular apparatus
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
The renal tubules
20
� proximal convoluted tubule, tubulus contortus proximalis:
� length 15 µm; width 50-60 nm
� parts:� initial part, neck
� convoluted tubule, pars convoluta
� straight tubule, pars recta
� simple columnar epithelium� brush border � microvilli
� basal striations
� reabsorption of water and electrolytes, amino acids, sugarsand polypeptides
� distal convoluted tubule, tubulus contortus distalis:� shorter and wider
� parts:� straight segment, pars recta
� convoluted, pars convoluta
� simple cuboidal epithelium� striations � short microvilli
� reabsorption of Na, K and water
� juxtaglomerular apparatus
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Prof. Dr. Nikolai Lazarov 21
� attenuated tubule (renal loop, loop of Henle), tubulus atenuatus (ansa nephroni):� in the medulla (pyramids)
� parts – U-shaped turn� pars descendens – 30 nm, simple squamous epithelium
� pars ascendens – 60 nm, simple cuboidal tocolumnar epithelium in the thick segment
� single microvilli
� reabsorption of Cl-
� collecting tubule, tubulus renalis colligens:� parts:
� arched collecting tubules,tubulus colligens arcuatus
� straight collecting tubules,tubulus colligens rectus
� simple cuboidal epithelium� light (CD) cells – aquaporin-1, 2 and 3
� dark (intercalated or IC) cells
� simple � bilayered (calyces) columnar epithelium
� basement membrane
� water reabsorption (ADH)
� small volume of hypertonic urine
The renal tubules
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
Kidney as an endocrine organ
22
� The juxtaglomerular apparatus:
� juxtaglomerular cells:
�modified smooth muscle cells in
the media of the afferent arteriole
� secretory granules (10-40 nm) – renin
� absent internal elastic membrane
� macula densa:
� taller columnar cells
o crowded nuclei
o signaling molecules � renin
� absent basement membrane
� extraglomerular mesangial (lacis) cells(Goormaghtigh cells) – erythropoietin
� interstitial cells – prostaglandins
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
Blood supply of the kidney
23
� Renal blood vessels:
� renal artery – 70% of the arterial blood:
� aa. interlobares, aa. arcuatae et aa. interlobulares � vas afferens
� accessory renal arteries – 30%
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Prof. Dr. Nikolai Lazarov 24
Kidney segmentation� Renal segments:
� segmentum superius� segmentum inferius� segmentum anterius superius� segmentum anterius inferius� segmentum posterius
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
Lymphatic drainage of the kidney
25
� Periarterial
lymphatic network
� Perivenous
lymphatic network
� Lymphatic network
in the renal capsule
� left kidney –
lymphatic vessels
around aorta
� right kidney –
lymphatic vessels
around
inferior vena cava
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Prof. Dr. Nikolai Lazarov 26
Nerve supply to the kidney
� Renal plexus:� parasynpathetic –
vagus nerve� sympathetic
� celiac and mesenteric ganglia
� somatosensory� thoracic and lumbar
spinal nerves
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Prof. Dr. Nikolai Lazarov
Renal anomalies
27
� Ectopic kidney:� renal hilum
� below L3 – lumbar, iliac and pelvic kidney
� above Th12 – thoracic
� unilateral andbilateral renal ectopia –horseshoe kidneyren atcuatus (1:600)
� cross fused renal ectopia
� congenital (inherited)
� acquired –movable kidney
� Absence of kidney
� Accessory kidney
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Prof. Dr. Nikolai Lazarov 28
Thank you ....