Embryology of Renal System - Galala University PDF

Lec-3 Embryology Of Renal System BMS 305/ BMS207 spring 2025 Dr. Mohamed Gamal Ayoub lecturer of anatomy dTQM health care from AUC mental health diploma from HIPH  ILOs: By the end of this lecture, the student should be able to: Describe the embryology of...

Lec-3 Embryology Of Renal System BMS 305/ BMS207 spring 2025 Dr. Mohamed Gamal Ayoub lecturer of anatomy dTQM health care from AUC mental health diploma from HIPH  ILOs: By the end of this lecture, the student should be able to: Describe the embryology of the kidney Describe the congenital anomalies of the kidney Describe the embryology of urinary bladder and urethra. Describe the congenital anomalies of urinary bladder and urethra Intraembryonic Mesoderm 1. Development of Kidney and Ureter Primordia Intermediate mesoderm: nephrotomes Cervical part → nephrogenic Caudal part → cords. I. Pronephros Nephrotomes → pronephric tubules and duct → degenerates. The most distal part of the pronephric duct persists to be used in mesonephros as a mesonephric duct.  II. Mesonephros It has no special duct → it utilizes the pronephric duct which is now called → Mesonephric duct. The tubules are → more caudal, more numerous, invaginated by capillaries →internal glomerulus The mesonephric duct elongates down till it opens into the cloaca. Mesonephric tubules → most disappear. Mesonephric duct → elongates and opens into cloaca. III. Metanephros Developed in the pelvis in the 5th week. Origin: Collecting part and Secretory part ureteric bud and metanephric cap  a. Collecting part Ureteric bud grows from the caudal part of mesonephric duct near its entry to cloaca. Ureteric bud grows cranially its distal end dilates and invade the caudal part of nephrogenic cord ( metanephrogenic cap ) → Ureter , renal pelvis, calyces, collecting tubules. b. Secretory part Each newly formed collecting tubule is covered at its distal end by a metanephric tissue cap. Under the inductive influence of the tubule, cells of the tissue cap form the nephron. Each metanephric cap→ cell clusters →canalized forming renal vesicles. -The vesicle now becomes an S-shapd tube. Its distal end comes to be invaginated by a tuft of capillaries which form a glomerulus. The various parts of the nephron are derived from this S-shaped tube.  ASCENT OF THE KIDNEYS Kidneys don’t stay at caudal end of body. They “ascend” to a position just caudal to diaphragm and liver. During the ascent of the kidney it rotates medially 90 degree so the hilum is directed medially.  POSITION OF THE KIDNEY The kidney, initially in the pelvic region, later shifts to a more cranial position in the abdomen. This ascent of the kidney is caused by diminution of body curvature and by growth of the body in the lumbar and sacral regions.  Congenital anomalies During the long process of renal development, problems can arise at any stage: ❖ Renal dysplasia and agenesis (1) ❖ Abnormal rotation and ectopic kidneys ❖ Horseshoe kidney (2) ❖ Congenital polycystic disease (3) (2 (1) ) (3) Multicystic dysplastic kidney Polycystic kidney Abnormal development of the collecting system, or failure of the collecting tubules and nephrons to join Kidney contains many cysts, and failure of renal function may be caused. Pelvic kidney Failure of kidney to ascend and still in the pelvis. Horseshoe kidney Both kidneys fail to ascend, and their lower poles fuse together. Double ureter Early splitting of ureter completely or partially; Ureters open into bladder separately, or unite and open as usual. 2. Development of urinary bladder and urethra The cloaca ( dilated caudal part of hindgut= endoderm) is divided by cloacal septum ( wedge shaped mesoderm between allantois and hindgut) which grows towards the cloacal membrane into: 1- A dorsal part ( anorectal canal). 2- A ventral part ( primitive urogenital sinus).  The primitive urogenital sinus is divided by a constriction at the level of the entry of the mesonephric duct, into cranial and caudal parts.  The cranial part with the constriction is named the primative urinary bladder ( vesico-urethral part)  and the caudal part is named definitive urogenital sinus. Primitive urinary bladder receives the openings of 3 ducts: 2 mesonephric ducts and allantois.  Urorectal septum Primitive Urogenital sinus Cloaca Anorectal canal Vesicouretheral canal Pelvic part Definitive Urogenital Phallic part sinus Divided into: Pelvic part; Phallic part.  Formation of the trigone& migration of mesonephric ducts -The caudal parts of mesonephric ducts are absorbed into wall of urinary bladder forming trigone. - Due to traction which is exerted by kidneys during their ascent the orifices of ureters move superolaterally and the ureters enter oblique through the base of the bladder. - The caudal ends of mesonephric ducts become the ejaculatory ducts. The orifices of these ducts move close together and enter the prostatic part of the urethra. - The caudal ends of the mesonephric ducts in females degenerate. 1- mesonephric duct trigone Migration of 2-ureter mesonephric 3-bladder ducts to open into prostatic urethra - The greater part of the urinary bladder develops from vesico-urethral part. - The apical part develops from the proximal part of alantois. - The distal part of alantois is obliterated to form obliterated urachus then median umbilical ligament. - The trigone develops from absorbed caudal parts of mesonephric ducts.  Development of urinary bladder and urethra Male Female Upper ： Urinary Urinary bladder bladder Primitive Urogenital constriction: upper part Urethra sinus of prostatic Cloaca urethra Urorectal Lower: Anorectal pelvic: lower part of Vestibule septum prostatic& of vagina canal membranous urethra Phallic : penile urethra  CONGENITAL ANAMALIES Ectopia Vesicae: due to failure of formation of anterior abdominal wall and anterior wall of urinary bladder. Urachal Fistula: due to failure of obliteration of urachus. Urachal Cyst: failure of obliteration of localized part of urachus Urachal Sinus: failure of obliteration of distal part of urachus. Ectopia vesica Fistulae formation: (Rectovaginal, rectouretheral, rectovesical, anouretheral and anovaginal fistula) due to incomplete development of cloacal septum.  Development of the urethra in male -Upper part of prostatic urethra above the ejuculatory ducts develops from the constriction of vesico-urethral part. -Lower part of prostatic urethra and membranous urethra develop from pelvic part of definitive urogenital sinus -Penile urethra develops from phallic part of definitive urogenital sinus except in glans penis developed from ectodermal cord cells which become canalized and communicate with the rest of urethra Development of Female Urethra -The Female urethera is developed from the constriction of vesico-urethral part of primitive urogenital sinus CONGENITAL ANOMALIES OF URETHERA Epispadius: when urethera opens into the upper surface of penis. Hypospadius: when urethera opens into lower surface of penis. 36 Thank You gu.edu.eg