URINARY SYSTEM human body physiology anatomy

Urinary System urinary System urinary System urinary System urinary effect urinary System urinary System urinary System urinary System urinary System urinary System urinary

1. DEVELOPMENT OF URINARY SYSTEM

2. Urinary sys develops from 2 embryonic structures: Intermediate mesoderm Cloaca

3. Intraembryonic mesoderm is subdivided into: Paraxial mesoderm which becomes segmented to form somites . Lat plate mesoderm in which intra-embryonic coelom appears. Intermediate mesoderm lying bet the 2.

4. After folding of embryonic disc & formation of peritoneal cavity, intermediate mesoderm forms a bulging on post abd wall lat to att of dorsal mesentery of gut. This bulging is- nephrogenic cord, which extends from cervical region to sacral region of embryo.

5. DEVELOPMENT OF KIDNEYS & URETERS 3 sets of kidneys develop: Pronephros -it is rudimentary & is present in fishes Mesonephros -well developed, functions briefly & is present in amphibians Metanephros -it becomes permanent kidneys

6. Pronephros : It is transitory structure, non functional They are few cell clusters & tubular structures in neck region Pronephric ducts arise from pronephros , run caudally & open into cloaca Most of these ducts persist & are used by next set of kidneys

7. It is a large elongated structure c/a nephrogenic cord Appears caudal to rudimentary pronephros They are well developed & function as temporary kidneys for about 4 wks Initially a mesonephric vesicle appears which is converted into mesonephric tubules These tubules open into pronephric ducts which are now c/a mesonephric ducts Mesonephros :

8. Free end of tubules are invaginated by a tuft of capillaries c/a glomeruli with aff & eff arterioles Mesonephros degenrates .

9. It is the primordium of permanent kidney Begins to dev in 5 th wk Starts function in 9 th wk Urine formation continues throughout foetal life & excreted into amniotic cavity Metanephros :

10. Permanent kidney develops from 2 sources: Metanephric diverticulum ( ureteric bud): Metanephric blastema

11. It is an outgrowth from mesonephric duct near its entrance into cloaca derived from caudal part of nephrogenic cord

12. Metanephric diverticulum gives rise to: Ureter Renal pelvis Calyces Collecting tubules Diverticulum elongates & becomes ureter Free end expands to form ampulla Ampulla divides 3-4 times & fuses to form renal pelvis Renal pelvis divides into major calyces, minor calyces & collecting tubules

13. Metanephric blastema gives rise to nephron Ampulla of collecting tubule induces formation of a small metanephric vesicle within metanephric blastema These vesicles elongate to form metanephric tubules Which become pear shaped & then s-shaped These metanephric tubules are now c/a renal tubules, their proximal ends are invaginated by a tuft of capillaries c/a glomerulus Invaginated part becomes glomerular capsule, together c/a corpuscle

14. Part of tubule next to corpuscle becomes coiled to form proximal convoluted tubule followed by loop of Henle & distal convoluted tubule which gets coiled & communicates with collecting tubule. Number of glomeruli increase & reach max no. by 32 wks

15. Foetal kidneys are initially lobuled as seen in new born In infancy lobulation disappears At term (9 mnths ) there are 8-10 lac nephrons Size of kidney is increased after birth d/t increase in length of PCT’s & increase in interstitial tissue Functional maturity occurs after birth Glomerular filtration begins in 9 th wk & rate of filtration increases after birth

16. Functional changes in kidneys: Initially primordial permanent kidneys lie close to each other ventral to sacrum As abd & pelvis grow, they lie in para vertebral gutters of abd & move apart Kidneys attain adult position by 9 th wk Initially hilum of kidney faces ventrally. As it ascends it rotates medially by almost 90 degrees Finally hilum faces anteromedially ‘coz of presence of vertebral column in median plane. Ascent of kidneys is stopped by suprarenal glands

17. Changes in blood supply: Initially renal art is a br of common iliac art Then renal art arises from distal end of aorta Finally permanent renal art is a br of abdominal aorta

18. CONGENITAL ANOMALIES One or both kidneys may be absent (Agenesis). Kidney may be underdeveloped ( Hypoplasia ) or overdeveloped (Hyperplasia). Adrenal tissue may be present within substance of the kidney. Distension of the pelvis with urine ( Hydronephrosis ) may occur d/t obstruction in urinary passages. Duplication: there may be an extra kidney on one side. It may be separate, or may be fused to the normal kidney.

19. Anomalies of shape: Horseshoe kidney: lower poles of the 2 kidneys (or sometimes upper poles) may be fused. Connecting isthmus may lie either in front of or behind the aorta & IVC. A horshoe kidney does not ascend higher than level of inf mesenteric art as inf mesenteric art prevents its ascent.

20. Pancake kidney: 2 kidneys may form one mass, lying in midline or on one side. 2 kidneys may lie on one side, one above the other, the adjacent poles are fused.

21. Lobulated kidney: Foetal kidney is normally lobulated . This lobulation may persist.

22. Anomalies of position: Kidneys may fail to ascend. Then they lie in the sacral region. Ascent of the kidneys may be incomplete so they may lie opp lower lumbar vertebrae. Kidneys may ascend too far & may be present even within the thoracic cavity. Both kidneys may lie on one side of the midline. They may lie one above the other or side by side. Ureter of the displaced kidney crosses to opp side across the midline.

23. Malrotated kidney: Hilum may face ant, post or lat Usually ass with ectopic kidney

24. Polycystic kidney: Diagnosed at birth or by USG during IUL Both kidneys contain many small cysts Death occcurs after birth d/t renal insufficiency Cause: Dilatation of part of loop of Henle Failure of ureteric bud to join tubules

25. Accessory renal arts: In 25% cases there are 2-4 renal arts on each side They are end arts They arise from aorta above/below main renal art They enter kidney at sup/ inf pole Inf accessory renal art may cross ureter causing obstruction leading to hydronephrosis .

26. ANOMALIES OF URETER: Duplication of urinary tract: Duplication of ureter & renal pelvis are common Cause: It occurs d/t div of metanephric diverticulum 2 metanephric diverticula Diff forms of duplication: Bifid ureter Double kidney with bifid ureter Double kidney with separate ureter Supernumerary kidney with 2 ureters

27. Ectopic ureter : Ureter does not open into urinary bladder In males, ureter may open into: Neck of bladder Prostatic urethra Prostatic utricle Ductus deferens Seminal vesicle In females, ureter may open into: Neck of bladder Urethra Vagina or vestibule

28. DEVELOPMENT OF URINARY BLADDER

29. Distal part of hind gut is- cloaca It is divided by a urorectal septum into a ventral part- urogenital sinus & a dorsal part-rectum.

30. Urogenital sinus: divided into 3 parts Cranial- vesical part: gives rise to urinary bladder continuous with allantois Middle pelvic part- In females gives rise to entire urethra In males-prostatic part of urethra Caudal phallic part : Grows towards genital tubercle

31. Bladder mainly develops from vesical part of UG sinus As bladder enlarges, distal parts of mesonephric ducts are incorporated into dorsal wall & forms CT of trigone This absorption of mesonephric ducts causes ureters to open separately into urinary bladder ‘coz of ascent of kidneys, openings of ureters move superolat & enter obliquely thro’ base of urinary bladder

32. Allantois initially continuous with urinary bladder is converted into a thick fibrous cord c/a urachus Urachus extends from apex of urinary bladder to umbilicus & in adults form median umbilical ligament Epi of urinary bladder is derived from endoderm & wall from mesenchyme

33. CONGENITAL ANOMALIES Urinary bladder may be absent or may be duplicated. Sphincter vesicae may be absent Lumen of urinary bladder may be divided into compartments by septa Bladder may be divided into upper & lower compartments (hourglass bladder) d/t constriction in middle of the organ.

34. If epi lining of urachus persists, it forms urachal cyst If patent inf end of urachus dilates, it forms urachal sinus that opens into bladder If entire lumen persists, it forms urachal fistula & urine comes from umbilicus

35. Exstrophy of bladder/ Ectopia vesicae : There is exposure & protrusion of post wall of bladder Trigone of bladder & ureteric orifices are exposed & urine dribbles intermittently from everted bladder Usually ass with wide separation of pubic bones In some cases, penis & scrotum are divided into 2 halves Cause: Incomplete median closure of inf part of ant abd wall It involves ant abd wall & ant wall of urinary bladder Inf parts of rectus abdominis are absent Ext oblique, int oblique & transversus abdominis are absent

36. DEVELOPMENT OF SUPRARENAL GLANDS It has 2 parts: Cortex derived from mesoderm Medulla derived from neural crest cells-ectoderm It develops bet root of dorsal mesentery & developing gonad one on each side Foetal cortex: Derived from mesothelial lining of post abd wall Cells are large & acidophilic It surrounds medulla Foetal cortex is very large in size

37. Medulla: Derived from cells of adjacent sym ganglion (formed by neural crest cells) These cells form a mass on medial side of foetal cortex Cells of medulla differentiate into secretory cells of suprarenal medulla

38. Formation of definitive cortex: More mesenchymal cells arise from mesothelium & surround primary foetal cortex Now foetal cortex starts regressing So definitive cortex is formed Differentiation of cortical zones occur in late foetal life At birth ZG & ZF are present ZR appears at end of 3 rd yr of life Foetal cortex disappears during 1 st yr of life Suprarenal gl in foetus is 10-20 times larger than adult gl relative to body wt They are larger than kidneys ‘coz of large size of foetal cortex Suprarenal medulla remains small until after birth Suprarenal gl regains its original wt by end of 2 nd yr

39. Development of Female Urethra

40. Whole of female urethra develops from caudal part of vesicourethral canal except a small terminal part, which develops from pelvic part of definitive urogenital sinus Phallic part of urogenital sinus forms vestibule of vagina into which urethra opens

41. Development of Male Urethra

42. Prostatic part: From caudal part of vesicourethral canal Membranous part: From lower pelvic part of definitive urogenital sinus Spongy part: From phallic part of definitive urogenital sinus except terminal part of urethra that is derived from surface ectoderm.