In-Depth Exploration of the Urinary System and Its Functionality

This PowerPoint presentation delves into the urinary system, detailing its anatomy, physiology, and the critical role it plays in maintaining homeostasis. Topics covered include the structure and function of the kidneys, ureters, bladder, and urethra, as well as the processes of urine formation and excretion. The presentation also addresses common urinary disorders and their pharmacological treatments, making it a valuable resource for students, healthcare professionals, and anyone interested in understanding the complexities of the urinary system

1. BY: Tewodros y. ( MSc in Human Anatomy) Dire Dawa University Collage of Medicine & Health science Anatomy Unit 6/9/2023 Tewodros Y.( Anatomist) 1

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3. Excre t ion Exc r e t ion — s e p a r a ti o n of wa s tes fr o m b o dy a n d t he e l imi n at i on of th e m F o ur b o dy s y st e ms c a rry o u t exc r et i on • fl u i d s • – R e spiratory s y stem • C O 2 , sma l l a mounts of o th e r ga s e s , a n d wa t er – In t eg u mentary s y stem • Wa t er, i n or g an i c s a lt s , l a c t ic a c i d , u r ea in sw e at Dige s t i ve s y stem • Wa t er, s a lt s , C O 2 , l i p i d s , b i le p i gment s , c h o l e s ter o l, m etab o l i c wa s te, and f ood r e s i due Urinary s y stem – other – • Many metab o l i c wa s te s , t o xin s , dr u g s , h o rmone s , s a lt s , H + , and water 6/9/2023 Tewodros Y.( Anatomist) 3

4. Di a p h ra g m 11 th a nd 12 th ribs A dr e n a l g la nd Re na l a rtery Re na l v e in Kid ne y V e rte b ra L2 A orta I n f e rior v e na ca v a U r e t e r U r i na ry b la d de r U r e thra (b) P os t e rior v i e w ( a ) A nt e rior v i e w • Urinary s y s t em c o n s ists of six organ s : u r ina r y blad d e r , and u r ethra two ki d neys, two urete r s, 6/9/2023 Tewodros Y.( Anatomist) 4

5. Fu n ctio n s of t h e Kidneys • Filt e rs u s ef u l bl o od, b l o o d p l a s ma, s e p a r a tes wa s te fr o m c h e mic a l s , ret u r n s u s ef u l s u b s t a n c e s elimina t es wast e s to • Reg u l a te blo o d volume and pre s sure by e l imi n at i ng or c o n s e r v i n g w a ter • Reg u l a te the osmolar i ty of the c o nt r o l li n g t he r e l a ti v e a mo u nts s o l u tes e l imi n at e d Secr e tes en z yme, renin, which b o dy f l u i ds by of wat e r a n d • a c ti v at e s h o rm o n a l me c h a n i sms th a t co n tr o l b l o od pressur e an d elec t rolyt e balance 6/9/2023 Tewodros Y.( Anatomist) 5

6. Fu n ctions of the Kidneys • Sec r et e s the h o rm o n e , e r y thropoi e tin, whi c h st i mula t es the pr o du c ti o n of red b l ood c e lls Col l a b o r ate with the l u n g s to r e g u l a te the C O 2 an d a c id – base bal a nce of b o dy f l u i ds Fin a l s t ep in s y n th e s i z i ng h o rm o n e , c a lc i t r iol, whi c h c o n tr i b u tes to c a l c i u m h o me o s t a s is Gluconeo g ene s is fr o m am i no a c i d s in e x t r e me s t a r v a ti o n • • • 6/9/2023 Tewodros Y.( Anatomist) 6

7. Mnemonic for kidney functions Just remember '  A W E T B E D', which stands for: Maintaining  ACID-base balance Maintaining  WATER balance ELECTROLYTE balance TOXIN removal BLOOD Pressure control Making ERYTHROPOIETIN Vitamin D metabolism 6/9/2023 Tewodros Y.( Anatomist) 7

8. Retroper i tone a l Pos i tion of the Kidney Copyr ig h t © The M c G ra w -H ill Co m pan ie s , I n c . P er m i s s ion requ ir e d f o r reprodu ct ion o r d i s p la y . A n t e r ior S mall in t e s t ine S t omach C o lon P anc r e a s In f e r ior v ena c a v a A o r t a L1 Ur e t er Renal a r t e r y a nd v e in P e r itoneum S ple e n Kidney Hilum Fibro u s c apsule P e r i r enal f a t ca psule Renal fa s cia Lum b ar m u s c les P oster i or 6/9/2023 Tewodros Y.( Anatomist) 8

9. LOCATION The kidneys lie on the posterior abdominal wall O ne on each side of the vertebral column , behind the peritoneum, O pposite 12th thoracic and upper three lumbar (T12–L3) vertebrae The right is slightly lower than the left 6/9/2023 Tewodros Y.( Anatomist) 9

10. Shape and Measurements Shape : Bean shaped . Measurements: Length: 11 cm. ( left kidney is slightly longer and narrower ). Width: 6 cm. Thickness: (anteroposterior) 3 cm. Weight: 150 g in males; 135 g in females. 6/9/2023 Tewodros Y.( Anatomist) 10

11. HILUM The medial border (central part) of the kidney presents a deep vertical slit called hilum. It transmits, from before backward, the following structures 1. Renal vein. 2. Renal artery. 3. Renal pelvis. 4. Subsidiary branch of renal artery. In addition to the above structures the hilum also transmits lymphatics and nerves, the latter being sympathetic and mainly vasomotor in nature. 6/9/2023 Tewodros Y.( Anatomist) 11

12. Relationship of structures passing through the hilum of kidney 6/9/2023 Tewodros Y.( Anatomist) 12

13. CAPSULES (COVERINGS) OF KIDNEY From within outwards, the kidney is surrounded by four capsules/coverings as follows 1. Fibrous capsule ( true capsule): a thin membrane which closely invests the kidney 2. Perirenal (perinephric) fat: a layer of adipose tissue, surrounding the fibrous capsule 3. Renal fascia (false capsule): It is a fibroareolar sheath, which surrounds the kidney and perirenal fat. Outside the fascia is the most superficial layer – a layer of fat tissue called the Paranephric fat . This layer sits posteriorly and posterolaterally to each kidney and separates it from the muscles of the abdominal wall. 6/9/2023 Tewodros Y.( Anatomist) 13

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15. MACROSCOPIC STRUCTURE kidney presents the kidney proper and the renal sinus . Kidney Proper: outer cortex and an inner medulla. The cortex is located just below the renal capsule and extends between the renal pyramids as renal columns (columns of Bertini). The medulla is composed of 5–11 dark conical masses called renal pyramids (pyramids of Malpighi). The apices of renal pyramids form nipple-like projections—the renal papillae which invaginate the minor calyces . 6/9/2023 Tewodros Y.( Anatomist) 15

16. Renal Sinus It is a cavity of considerable size present within the kidney. It takes up a large part of the interior of the kidney and opens at the medial border of the kidney as hilus. It contains: 1. Greater part of the renal pelvis, major and minor calyces. 2. Renal vessels, lymphatics, and nerves. 3. Fat. 6/9/2023 Tewodros Y.( Anatomist) 16

17. MICROSCOPIC STRUCTURE Histologically, each kidney consists of 1 to 3 millions of uriniferous tubules. Each uriniferous tubule consists of two components: N ephron and collecting tubule The nephron is the structural and functional unit of kidney. The number of nephrons in each kidney is about 1–3 million. Each nephron consists of renal corpuscle ( a glomerulus) and a tubule system. The glomerulus is a tuft of capillaries surrounded by Bowman’s capsule . The tubular system consists of the proximal convolute tubule, loop of Henle , and distal convoluted tubule. 6/9/2023 Tewodros Y.( Anatomist) 17

18. Cont… 2. Each collecting tubule begins as a junctional (connecting ) tubule from the distal convoluted tubule. Many collecting tubules unite together to form collecting duct (duct of Bellini) which opens on the apex of renal papilla. The collecting tubules radiate from the renal pyramid into the cortical region to form radial striations called medullary rays. 6/9/2023 Tewodros Y.( Anatomist) 18

19. Glomerulus A specialized capillary bed fed and drained by arterioles. Glomerular capillaries filter fluid from the blood into the renal tubule GC is attached to arterioles on both sides in order to maintain high pressure Large afferent arteriole arises from interlobular artery (feeder vessel); large in diameter, high resistance vessels that force fluid & solutes (filtrate) out of the blood into the glomerular capsule. 99% of the filtrate will be reclaimed by the renal tubule cells and returned to the blood in the peritubular capillary beds (blood vessels surrounding renal tubule) . Narrow efferent arteriole -merges to become the interlobular vein; draining vessel. 6/9/2023 Tewodros Y.( Anatomist) 19

20. The Ren a l Corpus c le Copyr ig h t © The M c G ra w -H ill Co m pan ie s , I n c . P er m i s s ion requ ir e d f o r reprodu ct ion o r d i s p la y . Glom er ul a r ca psu le : P ar i e t a l l a y e r Cap s u l a r s p ac e Podo c y t e s o f v i scera l l a y e r Glo m e rulus Key F low o f b lo o d F low o f f i l tra te A f fe r e n t ar t e r iole Bl oo d f l o w P r o x im a l c on v o lut e d tu b u le Gl o m er u l a r ca p i l l a r i e s (p odo c y t e s a n d ca p i l l a r y w a l l re m o v e d ) E f f ere n t ar t e r iole Bl oo d f l o w ( a ) • Glom e ru l ar filtrate c o l l ects in ca p su l ar sp a ce, f l o w s i n to pr o x im a l co n vo l ut e d tu b u l e. N o te t he vasc u l a r a n d ur i n a ry p o l e s. N o te t he a f fer e nt arter i o l e is l a rg e r th a n the e f fer e n t a rter io l e . 6/9/2023 Tewodros Y.( Anatomist) 20

21. The Nephron • Vas c ular p o l e the af f er e nt art e ri a l e nt e rs the c o rp u s c le and the ef f e r e n t art e ri o le l e a v es • Urina r y p o l e - the o p p o s i te s i de of t h e co r p u s c le whe r e the r e n a l t u b u l e b e g i n s 6/9/2023 Tewodros Y.( Anatomist) 21

22. The Renal Tu b ule • R e nal ( urin i ferous) tubul e — a duct that l ea d s aw a y f r om the gl o me r ul a r caps u le and en d s at the t ip o f the m ed u l l ary pyramid Divided in t o four re g ions – Prox i mal con v oluted tubu l e, nephron l oop, distal con v oluted tubule: pa r ts of one nep h r o n – Collecting duct r e c e i v es fluid from many nep h r o ns • • Pro x i m al c on v oluted tub u le (PC T ) — arises f r om gl o me r ul a r caps u le – Longe s t and most coiled region – Si m ple cu b oidal epithelium with prom i nent m i cro v i l li for ab s o r ption majority 6/9/2023 Tewodros Y.( Anatomist) 22

23. The Renal Tu b ule N e phron l oop ( l oop of H enle ) — l o ng U - sha p ed portion of renal tubu l e • – – D e s c e n ding li m b a n d as c e n ding li m b Thick s e gmen t s h a v e simple cub o id a l e p itheli u m • Ini t ial part of de s c e nding limb and pa r t or all of a s c e nding limb • H e avily eng a ged in t he a c ti v e tran s port of s a lts and have many mi t o c hon d ria Thin s e gment h a s si m ple squamo u s e p ithelium • Forms low e r pa r t of de s c e nding limb • C e lls v e r y pe r meable to w a ter – • Distal co n voluted tubule (DCT ) — be g i n s asc e n d i n g l i mb reenters the cortex shortly af t er the – – – Sho r ter and less coiled tha n P CT C u b o idal e p ithelium witho u t mi c r o villi D C T i s the e n d of the ne p h r on 6/9/2023 Tewodros Y.( Anatomist) 23

24. The Renal Tu b ule Collect i ng du c t — receives flu i d f r om the D C Ts ne p hrons as it passes back into t he medul l a • of s e veral – N u mer o us collec t ing d u c t s con v e r ge t o w a r d the t i p med u llary p y r a mid of t he – Papi l lary duct: formed by mer g er of sev e r a l c ollec t ing d u c t s • • 30 papilla r y du c ts end in t he tip of ea c h papilla C o llecting and papilla r y du c ts lined with simple c u boid a l epithelium • Fl o w of fl u id f r om the po i nt w h ere the gl o me r ul a r filtra t e is for m ed to the po i nt w h ere urine l e aves the body: glomerular caps u le → proximal c onvolut e d tubule → ne p hron loop → di s tal co n vo l uted tub u le → c o lle c ting du c t → p a pil l ary du c t → mi n or c a l y x → m a jor c a l y x → renal pe l vis → uret e r → urin a ry bl a dd e r → uret h ra 6/9/2023 Tewodros Y.( Anatomist) 24

25. M i cro s c o pic Anat o my of the Cop yr i gh t © T h e Mc G r a w - H il l Co m pan i e s , I n c. P e r mi ss i o n r equ i r e d f o r r ep r odu c t i o n o r d i s p l a y. Nep h ron Re na l capsu le Re na l co r te x Ne ph r o n C o l lect i n g duc t Re na l m edu l l a M i no r ca l y x Re na l pap i l la (a) Re na l co r pusc l e : G lo m e r u l a r capsu le G lo m e r u l u s C o r t i ca l neph r o n E ffe r en t a r te r i o le C on v o l ute d tubu l e s ( P CT an d DC T ) A ffe r en t a r te r i o le Juxta m edu l la r y neph r o n Pr ox i m a l Di sta l con v o l ute d tubu le ( DC T ) con v o l ute d tubu le ( P C T ) C o r te x M edu l l a Ne ph r o n l oop : De scend i n g l i m b A scend i n g l i m b C o l lect i n g duc t ( CD) Th i c k seg m en t Th in seg m en t Ne ph r o n l oop s Key F l o w o f b l oo d F l o w o f t u b u l a r f l u id (b ) C o l lect i n g duc t P ap i l l a r y duc t (c) 6/9/2023 Tewodros Y.( Anatomist) 25

26. Nephrons type • Cortical ne p hrons – – – 85% of all neph r ons Short nep h r o n loops E f f erent arterioles bran c h into peritubular capi l lar i es a r ound PCT and D C T Cop yr i gh t © T h e Mc G r a w - H il l Co m pan i e s , I n c. P e r mi ss i o n r equ i r e d f o r r ep r odu c t i o n o r d i s p l a y. C o r t i c al n e p hr o n A ff e r e n t a r t e r i o le Gl o m e ru l u s E ff e r e n t a r t e r i o le J u x t a m e d u lla r y n e p hr o n C o r t e x P CT I n t e r l ob u l a r a r t e r y DCT • Ju x tamedul l ary n e p h rons I n t e r l ob u l a r v ein P e r i t u b u l a r ca p ill a r i e s – – 15% of all neph r ons Very long nep h r o n loop s , maintain s a linity gradie n t in the medulla and helps c o n s e r ve w a ter E f ferent a r terioles b r an c h into v asa rec t a a r ound long nep h r o n loop C o r t i co m e d u lla r y j un c t i o n A r c u a t e a r t e r y A r c u a t e v ein V asa r ec t a M e d u l l a C o llec t i n g d u ct Ne p hr o n l oo p – 6/9/2023 Tewodros Y.( Anatomist) 26

27. Cont… Glomerular capillaries are covered with podocytes from the inner (visceral) layer of the glomerular capsule. Podocytes have long, branching processes called pedicels that intertwine with one another and cling to the glomerular capillaries. Filtration slits between the pedicels form a porous membrane around the glomerular capillaries . 6/9/2023 Tewodros Y.( Anatomist) 27

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29. The kidneys are supplied by the renal arteries . Usually there is one renal artery for each kidney, but in about 30% individuals accessory renal arteries are also found. They commonly arise from the aorta and enter the kidney at the hilus or at one of its poles, usually the lower pole. The renal arteries arise directly from the abdominal aorta just below the origin of the superior mesenteric artery ( i.e.,at the level of intervertebral disc between L1 and L2). The renal arteries have a blood flow in excess of 1 L/minute . Renal Circulation 6/9/2023 Tewodros Y.( Anatomist) 29

30. Renal Circulation • Kid n e y s a c c o u n t for o n ly 0. 4 % of b o dy we i g h t, t h e y r e c e i v e a b o ut 2 1 % of the c a r d i ac o u tp u t ( r enal fr a ct i o n ) Renal a r t e ry d i v i d e s into s e gmental a r t e ri e s th a t g i ve r i se to: • - - - - In t erlobar arter i es: up renal co l umns, betwe e n Arc u ate ar t eries: over py r amids In t erlobu l ar arter i es: up i n to cor t ex Bra n ch i n to afferent arterioles: e a ch su p p l yi n g ne p hron • Le a ds to a b a l l o f c ap i l l ar i e s — glo m erul u s pyramids one 6/9/2023 Tewodros Y.( Anatomist) 30

31. Renal C i rculati o n C o nt. - B l ood is drain e d f r om the gl o me r ul u s by ef f erent arterioles Le a d to e ither peritubular ca p i l lar i es or va s a recta around portion of the renal tubu l e In t erlobular veins or d irectly i n to arcuate veins— - - interlobar v e ins • Renal v e in em p ti e s i n to inf e rior v e na c a va 6/9/2023 Tewodros Y.( Anatomist) 31

32. Ren a l Circ u l a tion Copyr ig h t © The M c G ra w -H ill Co m pan ie s , I n c . P er m i s s ion requ ir e d f o r reprodu ct ion o r d i s p la y . In t e r lo b ular a r t e r y and v ein In t e r lo b ar a r t e r y and v ein S eg m en t al a r t e r y A orta In f e r ior v ena c a v a Renal a. Renal v . Renal me d ulla S eg m en t al a. Renal a r t e r y and v ein In t e r lo b ar a. In t e r lo b ar v . Renal cortex A r cua t e a. A r cua t e v . In t e r lo b ular v . In t e r lo b ular a. A r cua t e a r t e r y and v ein P e r itubular c a pill ar ies A ff e r ent a r t e r iole V a s a r e c t a E ff ere nt ar t er iole G lo m e r ulus ( a) (b) K i d n eys rece i ve 2 1 % of c a rdi a c o u tput 6/9/2023 Tewodros Y.( Anatomist) 32

33. Renal I n nervation • Renal ple x u s —n e r v es a n d g a n g l ia wra p p e d ar o und ea c h r en a l a rt e ry – F o llows bra n c h es of the ren a l ar t ery into the p a ren c h y ma of the ki d n e y – Is s u e s n e rve fibers to of the the blo o d v e s s els ne p hron a n d c o n v oluted tub u les 6/9/2023 Tewodros Y.( Anatomist) 33

34. Renal I n nervation Co n t. – Carries s y mpathetic innerv a tion f r om a o rt i c pl e x u s the a bd o minal • Stimul a tion reduces gl o me r ul a r bl o od flow and rate of urine producti o n R e spo n d to fa l l i ng bl o od pressure by stimulati n g the ki d neys to s e cre t e renin, an enzyme t hat activates hormonal mechan i sms to restore b l ood pressure • – C a rr i es p a ras y mp a thetic inn e rvation from the v a g u s n e rve; in c rea s es rate of u rine pro d u c tion 6/9/2023 Tewodros Y.( Anatomist) 34

35. Structure of Glo m eru l ar Fi l trati o n M e mbr a ne Copyr ig h t © The M c G ra w -H ill Co m pan ie s , I n c . P er m i s s ion requ ir e d f o r reprodu ct ion o r d i s p la y . End o the l i al ce l l of glome r ular capi ll ary B asement me m brane T urned back: B l oo d c e ll s P l a s ma p roteins L ar g e a n i on s P rotei n- bound m i nerals and h o r m o n es Most mo l ec u l es > 8 nm i n dia m eter Fi l t r at i on s li t Fi l t r at i on p o re F o ot process of p o d o c y te Pas s ed t hro u gh f i l te r : W ater Elect r ol y tes Gl uc o se A m i no acids Fat t y ac i ds V i ta mi ns U rea U r i c acid Crea ti nine B l o o dstream C aps u l ar space 6/9/2023 Tewodros Y.( Anatomist) 35

36. The Fi l tration Me m brane Filt r a t ion membran e — th r ee b a r r i e rs t h r o u g h fl u id p a s s es • whi c h – Fe n es t rated en d oth e lium of glo m erul a r ca p ill a ries • 70 to 90 nm fi l tration po r es exclude blood cells • Hig h ly permea b le Bas e m e nt m e mbr a ne – • Proteoglycan gel , neg a ti v e c h a r ge, exclud e s mole c ules g r eater than 8 nm Albumin r e pelled by neg a ti v e c h a r ge Blood plasma is 7% p r otein, the fi l trate is only 0.03% p r otein • • – Filtr a tion sli t s • Podoc y te c e ll ex t en s ions (pedicels) w r ap a r ound the to form a bar r ier layer with 30 nm fi l tration slits • N e gati v ely c h a r ged w h ich is an additional ob s tacle for anio n s c a pillari e s lar g e 6/9/2023 Tewodros Y.( Anatomist) 36

37. Renal Autoregulat i on – Ju x taglomeru l ar (JG) c el l s: en l arged smooth musc l e ce l ls in af f erent arte r i o le directly across f rom macula de n sa • • • When st i m ul a ted by the macu l a Th e y d i l a te o r c o n s tr i ct the ar t er i o l es Th e y a l so c on t a i n g ra n u l es of re n i n , wh i ch th e y s e c r ete in re s po n se to dr o p in b l ood pr e s s ure – Mesangial c el l s: in cleft b etween af f erent a n d ef f erent arte r i o l e s and among cap i l l aries of the gl o me r ul u s • Conne c ted to macu l a de n sa and JG ce l ls by gap j un c tio n s and c om m un i c a te by means of p ar a c r i n es • Bu i ld s u pp o rt i ve matrix for g l omeru l u s , c o n s tr i ct or re l ax c a p i l l ar i es to r eg u l a te f l o w 6/9/2023 Tewodros Y.( Anatomist) 37

38. The Ju x tagl o m e rular • Copyr ig h t © The M c G ra w -H ill Co m pan ie s , I n c . P er m i s s ion requ ir e d f o r reprodu ct ion o r d i s p la y . Appar a tus If GFR rises – Flow of tubular fluid in c r e a s es and more N a Cl is r e ab s o r b e d Ma c ula den s a stimulates JG c e lls with a par a crine JG c e lls c o ntract w h ich c o n s tricts af f e r ent a r teriole, r e du c ing GFR to normal OR Me s angi a l c e lls may c o ntra c t, c o n s tricting the c a pillari e s and r e du c ing fi l tration – – S y mp a t h e tic ne r v e fib e r Podoc y tes – M esa ngi a l ce l l s J uxt a glom e rul a r c e lls Ef f e r e nt a rter i ole • If GFR fal l s – Ma c ula r e laxes af f e r ent a r terioles and me s angi a l c e lls – Blood f low in c r e a s es and GFR ri s es ba c k to normal A f f e r e nt a rter i ole Smoo t h mu sc le ce l l s M ac ula den s a Nephron loop 6/9/2023 Tewodros Y.( Anatomist) 38

39. Reni n– Angio t en s i n – Al d os t ero n e M e ch a ni s m Co p y r ig h t © T h e M cG ra w - Hill Co m pan ies, I n c. P er m issi o n requ ir e d f o r reprodu cti o n o r d ispl a y . • Renin s e c r et e d by j u xtagl o merul a r c e l l s if BP dr o ps dramati c al l y Ren i n c onverts an g iot e ns i no g en, a b l o od pr o te i n, i n to an g iot e ns i n I In the lungs and kidne y s, an g iot e ns i n -co n vert i ng en z y me (ACE) c o nverts D r o p in b l oo d p r essu r e L i v e r A ng i otens i n o g e n (45 3 a m i n o ac i d s l ong ) • Re n in Ki dne y A ng i otens in I (1 a m i n o ac i d s l ong ) A ng i otens i n - con v e r t i n g en z y m e ( A C E ) • A ng i otens in II ( 8 a m i n o ac i d s l ong ) Lungs H y potha l a m u s Ca r d i o v ascu l a r s y ste m A d r ena l co r te x an g i o te n s i n I to an g iot e ns i n the a ct i v e hormone – Wo r ks in several w a ys to r e sto r e fluid volume and BP II, A l doste r on e Ki dne y V asoconst r i ct i o n Th i r s t an d d r i nk i n g S od i u m an d w ate r r etent i o n E l e v ate d b l oo d p r essu r e 6/9/2023 Tewodros Y.( Anatomist) 39

40. 6/9/2023 Tewodros Y.( Anatomist) 40 Ureter

41. I n t r od u c t i o n • The ureter is a narrow, thick• walled, expansile muscular tub e . Conveys urine from the kidney to the urinary bladder. The urine is propelled from the • • kidney to the urinary bladder by the peristaltic contractions of the smooth muscle of the wall of the ureter.

42. M ea s ur e m e n t s • Length: 25 cm (10 inches). • Diameter: 3 mm.

43. COU R S E IN ABDO M I N AL The ureter begins as a downward PART • continuation of a funnel shaped renal pelvis at the medial margin of the lower end of the kidney. The ureter passes downward and slight • medially separates on the psoas major , which it from the transverse processes of the l umbar vertebrae. Enters the pelvic cavity by crossing in front of the bifurcation of the common iliac artery at the pelvic brim in front of the sacroiliac joint. •

44. ~=iil ::_4--- _ >- - - ..._,... . • C O U R S E I N P E L V I S In the pelvis, the ureter first runs downward, backward, an d l a terally along the anterior margin of the greater sciatic notch. • • Opposite t o the ischial spine, i t tu rns forward and medially to reach the base of the urinary bladder. • • Where Within t akes a it enters the bladder wall obliquely . ,. the bladder wall, it narrows down, sinuous course , and opens into th e cavity of the b l adder a t the l ateral ang l e of i t s trigone as u r e t eric orifice.

45. PAR T S AND R E L A TI O N S • The ureter is generally divided and pelvic. in t o t wo part s : abdominal • • Each part is about the same length, i. e . , 12.5 cm (5 inches ) . The abdominal part of ureter e x tends from the renal pelvis to the bifurcation of the common iliac artery. • The pelvic part of the ureter ex t ends from the pelvic brim (at the level of bifurcation of the common iliac a r tery) to the base of the urinary bladde r .

46. R E L A TIO N S OF PE L V I C P A R T • The pelvic part of ureter crosses in front of all the nerves and vessels on the lateral pelvic wall except vas deferens, which crosses in front of it. Near the uterine cervix, the uterine artery lies above and • in front of it, a highly important surgical relationshi p .

47. SITES OF A N ATOMICAL NA RROWING CONSTRICTI O NS • The lumen of t h e ure t er is not uniform throughout and presents three constrictions at the following At the pelv i ureteric junction end of ure t er . It is the u pper sites. where the renal pelvis j oins the u pper mos t constriction, found approximately 1. 5 cm away from th e h i l um of kid n ey . At th e pelvic brim w h ere it crosses th e co m mon iliac ar t ery. At t h e uretero-vesical junction (i. e . , w h ere ureter enters into the bl a dd e r ) . 2 . 3 .

48. The U r eters – T h ree l a yers of ureter • Adv e ntit i a —c o nn e c t ive ti s s u e l a yer s u rro u nd i ng s t ru c tur e s th a t c on n e c ts ur e ter to • Muscu l ari s —two l a yers of s mooth mus c le with th i rd l a yer in l ower uret e r – U r ine enter s , it str e tches and c o ntra c ts in peri s tal t ic w a ve Mucos a — tra n s i ti o nal ep i th e l i um – Begins at minor c a l y c e s and ex t ends throu g h the blad d er • – L u men very n a r r o w , e a si l y o b structed ki d n e y ston e s 6/9/2023 Tewodros Y.( Anatomist) 50

49. Arterial supply 6/9/2023 Tewodros Y.( Anatomist) 51

50. • • VEN O US DR A INAGE Th e ve n o u s blo o d fro m th e- ureter i s drained corresponding to the art e ries. LYMPHATIC DRAINAGE T h e l y mph fr o m th e u re t er is d r a i ne d i n to lateral aortic and il i ac nodes . NERVE SUPPLY Th e sy mp a th e tic s upp ly of th e ur eter i s der i v ed fro m T 12- Ll s pinal • • • 1. segm e nt s thro u g h renal, aort i c, and hypogastr i c plexuses . 2. T h e p arasy m p a th etic s up p l y of ur e t e r i s d e ri ve d fro m S2-S4 spinal seg m e nt s throu g h pelvic sp l anchnic nerves. Th e a ff e r e nt fibr es tr av e l w ith both sy mpat h e t i c and par a sy m p at h e t i c n e r ves .

51. C l in i cal co r r e l at i o n • Ureteric calculus is likely to lodge-at one of the sites.of narrowings of the ureter particularly: (a) A t the pe l v i c ureteric junction, (b) Where it crosses the pelvic brim. (c) In the intramural par t - the narrowest part. • Injury to ureter s : the ureter injured at one of the following four dangerous sites: (a) Point where the ureter crosses the iliac vessels. (b) In the ovarian fossa. an a t cmic a l m ay be (c) Where the ureter is crossed by the uterine artery (most damage is likely a t this site during hys t erectomy. (d) At the base of the b l adder. dangerous site) as

52. Urinary Bladder and Urethra URINARY BLADDER Is a muscular reservoir of urine. Located in anterior part of the lesser pelvis behind the pubic symphysis and in front of rectum in male and uterus in the female. The location of the urinary bladder varies with the amount of urine it contains and with age. When the bladder is empty it lies entirely within the lesser pelvis but when it becomes distended with urine, it expands upward and forward into the abdominal cavity. In children, the bladder is an abdominopelvic organ even when it is empty because the pelvic cavity is small and the neck of bladder lies at the level of the upper border of pubic symphysis. It begins to enter the enlarging pelvis at the age of six years but does not become a pelvic organ entirely until after puberty. 6/9/2023 Tewodros Y.( Anatomist) 54

53. Cont.. It plays two main roles: Temporary storage of urine  – the bladder is a hollow organ with distensible walls. It has a folded internal lining (known as rugae ), which allows it to accommodate up to 400-600ml of urine in healthy adults. Assists in the expulsion of urine  – the musculature of the bladder contracts during micturition, with concomitant relaxation of the sphincters. 6/9/2023 Tewodros Y.( Anatomist) 55

54. E xternal features Apex  – located superiorly, pointing towards the pubic symphysis. It is connected to the umbilicus by the median umbilical ligament (a remnant of the urachus ). Body  – main part of the bladder, located between the apex and the fundus Fundus (or   base)  – located posteriorly. It is triangular-shaped , with the tip of the triangle pointing backwards. Neck  – formed by the convergence of the fundus and the two inferolateral surfaces. It is continuous with the urethra. 6/9/2023 Tewodros Y.( Anatomist) 56

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56. Musculature The   musculature  of the bladder plays a key role in the storage and emptying of urine. T he bladder wall contains specialised smooth muscle – known as  detrusor muscle . Its fibres are orientated in multiple directions, thus retaining structural integrity when stretched. It receives innervation from both the sympathetic and parasympathetic nervous systems. The fibers of the detrusor muscle often become  hypertrophic  (presenting as prominent trabeculae) in order to compensate for increased workload of the bladder emptying. This is very common in conditions that obstruct the urine outflow such as benign prostatic hyperplasia. 6/9/2023 Tewodros Y.( Anatomist) 58

57. Cont… There are also two muscular sphincters located in the urethra: Internal urethral sphincter: Male – consists of circular smooth fibres , which are under autonomic control. It is thought to prevent seminal regurgitation during ejaculation . Females – thought to be a functional sphincter (i.e. no sphincteric muscle present). It is formed by the anatomy of the bladder neck and proximal urethra. External urethral sphincter  – has the same structure in both sexes. It is skeletal muscle , and under voluntary control . 6/9/2023 Tewodros Y.( Anatomist) 59

58. Vasculature The principal arteries supplying blood to the bladder are: superior and inferior vesical arteries which are the branches of anterior division of internal iliac arteries. 2. The other arteries which make small contribution in supplying the lower part of the bladder are: (a) Obturator and inferior gluteal arteries. (b) Uterine and vaginal arteries in the female. 6/9/2023 Tewodros Y.( Anatomist) 60

59. NERVE SUPPLY Motor Innervation It is provided by the parasympathetic, sympathetic, and somatic fibres. Parasympathetic fibres (nervi erigentes ) are derived from S2, S3, S4 ( spinal micturition centre ) segments of the spinal cord. They are motor to the detrusor muscle and inhibitory to the sphincter vesicae (internal urethral sphincter). 2. Sympathetic fibres are derived from T11, T12 thoracic and L1, L2 lumbar segments of the spinal cord. They are inhibitory to the detrusor and motor to the sphincter vesicae . 3. Somatic fibres (pudendal nerve) are derived from S2, S3, S4 spinal segments. They are motor to the external urethral sphincter. 6/9/2023 Tewodros Y.( Anatomist) 61

60. Cont.. The sympathetic innervation is responsible for the filling of the bladder Parasympathetic innervation for the emptying of the bladder. The somatic innervation is responsible for voluntary control of micturition. 6/9/2023 Tewodros Y.( Anatomist) 62

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62. Urethra The urethra is a fibromuscular tube that serves as the passage of urine from the urinary bladder to the exterior . In males it also serves as a passage for semen in most of its course. It is closed when fluid is not passing through it. 6/9/2023 Tewodros Y.( Anatomist) 64

63. Male urethra The male urethra is about 20 cm long. It begins at the neck of the bladder and extends through the prostate, the pelvic diaphragm, the sphincter urethrae and the root and body of the penis to the tip of the glans. Therefore it is divided in to 3 parts. 1 . Prostate part 2.Membranous part 3.Spongy (penile) part 6/9/2023 Tewodros Y.( Anatomist) 65

64. Cont… Prostatic part - traverses the prostate . This part is about 3 cm long and somewhat curved obliquely in the anterior direction. It is more dilatable than the other parts. When distended it is the widest part of the entire urethra . Ejaculatory ducts and numerous ducts of the prostatic glands open into this part. The proximal part of the prostatic urethra is provided with the so-called prostatic sphincter, which extends to the neck of the bladder. 6/9/2023 Tewodros Y.( Anatomist) 66

65. Cont… 2. Membranous part – extends from the lower part of prostate to the bulb of the penis by passing through the pelvic diaphragm and sphincter urethrae . It is the shortest, narrowest and least dilatable part of the male urethra. The membranous part of the male urethra is surrounded by the sphincter urethrae muscle as it enters the bulb of the penis. 6/9/2023 Tewodros Y.( Anatomist) 67

66. Cont….. 3. Spongy part – Lies in the corpus spongiosus penis. It is about 10 - 20 cm long and extends from the bulb of the penis to the external urethral orifice on the glans of the penis 6/9/2023 Tewodros Y.( Anatomist) 68

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68. Female urethra (urethra feminina ) The female urethra is about 3-5 cm long ; therefore ascending infection of the urinary tract is more common in females than in males. It is quite distensible, and can be dilated to about 1 cm without damage to it. It extends from the internal urethral orifice in the neck of the bladder to the external urethral orifice or vestibule of the vagina. passes through the pelvic diaphragm where it is controlled by the skeletal muscle, sphincter urethrae, formed by the transverse perinei profound muscle. 6/9/2023 Tewodros Y.( Anatomist) 70

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