GEMP I: Normal and Abnormal Urogenital System Development (Lecture 2) PDF

Normal & abnormal development of the urogenital system: GEMP I: Lecture 2 Mrs Natasha Loubser [email protected] School of Anatomical Sciences Office: 2P20 2024 Intended learning outcomes Describe the development of the urinary system:...

Normal & abnormal development of the urogenital system: GEMP I: Lecture 2 Mrs Natasha Loubser [email protected] School of Anatomical Sciences Office: 2P20 2024 Intended learning outcomes Describe the development of the urinary system: Three embryonic kidneys (pronephros, mesonephros, metanephros) The development of the collecting & excretory system The ascent of the kidneys The development of the urinary bladder & urethra Abnormalities Describe the development of the genital system: The formation of the indifferent gonads The embryonic formation of the testes & ovaries The descent of the testis & ovaries The development of the paramesonephric ducts The development of the external genitalia  © 2020, Elsevier Inc. All rights reserved. Epiblas Urogenital system t Gastrulation: process by which the bilaminar embryonic disc is converted into a trilaminar embryonic disc Hypoblas t Begins during the 3rd week of development Each germ layer (ectoderm, mesoderm, endoderm) of the trilaminar disc gives rise to specific tissues and organs Derived from the cells of the epiblast 1 © 2020, Elsevier Inc. All rights reserved.  Trilaminar disc Embryonic ectoderm: epidermis, CNS and PNS, eyes and internal ears, neural crest cells, and many connective tissues of the head Embryonic mesoderm: all skeletal muscles, blood cells, the lining of the blood vessels, all visceral smooth muscle coats, serosal linings of the body cavities, ducts and organs of the reproductive and excretory systems, most of the cardiovascular system Embryonic endoderm: source of the epithelial linings of the respiratory, urinary system, and GI tracts, including the glands opening into the GIT, and glandular cells of associated organs such as the liver and pancreas 2 © 2020, Elsevier Inc. All rights reserved.  Intraembryonic mesoderm Intraembryonic mesoderm fills the space between the endoderm and ectoderm Amniotic cavity The mesoderm cells differentiate: paraxial mesoderm: forms the dermatome, sclerotome, and myotome intermediate mesoderm: contributes to the urogenital system Yolk sac: secretes extraembryonic mesoderm that surrounds the yolk lateral plate mesoderm: involved in the sac and amniotic cavity formation of the body cavities splanchnic mesoderm: follows the endoderm somatic mesoderm: follows the ectoderm 3 © 2020, Elsevier Inc. All rights reserved.  Urogenital ridge (~4th week) Nephrogenic Gonadal cord ridge Urinary Genital system system [kidneys, [external ureters, genitalia, urinary internal bladder, genitalia, urethra] accessory glands] 4 © 2020, Elsevier Inc. All rights reserved. 5  Pronephros Rudimentary and nonfunctional Appear early in the 4th week Tubular cell clusters in the cervical region Pronephric ducts run caudally and open into the cloaca Pronephros will degenerate Duct system persists, used by the mesonephros 6 © 2020, Elsevier Inc. All rights reserved.  Mesonephros Appears late in the 4th week Caudal to the degenerating pronephros Function as interim kidneys Consists of ~40 glomeruli and mesonephric tubules Tubules open into mesonephric ducts [previously pronephric ducts] The duct opens into the cloaca Degenerate at the end of the first trimester [~3 months] Fxn: create urine between weeks 6 – 10, until permanent kidneys begin to function Tubules ➔ efferent ductules of the testes Regress in females 7 © 2020, Elsevier Inc. All rights reserved.  Metanephros Primordia of the permanent kidneys Develops early in the 5th week Begins to function early in the 9th week Reciprocal induction: Ureteric bud (metanephric diverticulum) Collecting system: ureter, renal pelvis, calices, and collecting tubules & ducts Metanephrogenic blastema [mesenchyme from the nephrogenic cord ➔ nephrons] Excretory system: renal corpuscles, proximal convoluted tubules, loops (of Henle), distal convoluted tubules 8 © 2020, Elsevier Inc. All rights reserved.  Urinary system 9 © 2020, Elsevier Inc. All rights reserved.  Urinary system – positional changes 10 © 2020, Elsevier Inc. All rights reserved.  Congenital abnormalities Accessory renal arteries: Blood supply to the kidneys continually changes during embryonic and early fetal life Common iliac arteries ➔ renal arteries Distal aorta ➔ renal arteries Abdominal aorta ➔ renal arteries ~25% of adult kidneys ➔ supernumerary (accessory) renal arteries Inferior pole: polar arteries (hydronephrosis) 11 © 2020, Elsevier Inc. All rights reserved.  Congenital abnormalities Renal agenesis (absence of kidney): Unilateral 0.1% of the population Hypertrophy of the single kidney Bilateral Oligohydramnios (reduction of amniotic fluid) Little or no urine excreted into the amniotic cavity 1 in 3000 births (3x more common in males) Incompatible with postnatal life Also have pulmonary hypoplasia Failure of ureteric bud to penetrate metanephric blastema ➔ absence of renal development [no nephrons are induced by the collecting tubules] 12 © 2020, Elsevier Inc. All rights reserved.  Congenital abnormalities Cystic kidney disease: Autosomal dominant polycystic kidney disease (ADPKD) most common 1:500 Reduce normal kidney function Malrotation of kidneys: No rotation: hilum faces anteriorly Over rotation: hilum faces posteriorly Medial rotation: hilum faces laterally ➔ Ectopic kidneys: kidneys remain in the pelvis / inferior part of the abdomen 13 © 2020, Elsevier Inc. All rights reserved.  Congenital abnormalities Unilateral fused kidney: Developing kidneys while in the pelvis Move to normal position Horseshoe kidney (U-shaped): Most common renal fusion defect, usually inferior pole fusion 0.2% population, Usually located in the pelvic region Function preserved, normal blood supply and ureteric formation Duplication of urinary tract: Supernumerary kidney – duplication of ureteric bud Bifid ureter Double kidney (bifid / separate ureter) 14 © 2020, Elsevier Inc. All rights reserved.  Urinary bladder Urogenital sinus: Vesical part: bladder Pelvic part: urethra [& prostate in males] Phallic part: genital tubercle (primordium of the penis or the clitoris) Urinary bladder: Vesical part Trigone: caudal ends of the mesonephric ducts Allantois ➔ urachus ➔ median umbilical ligament Epithelium ➔ endoderm Walls ➔ splanchnic mesoderm 12th week 15 © 2020, Elsevier Inc. All rights reserved.  Urethra Urogenital sinus: Pelvic part: urethra [& prostate in males] Endoderm of urogenital sinus ➔ epithelium of most of the male urethra and the entire female urethra Ectodermal cells ➔ distal part of the urethra in the glans penis Splanchnic mesenchyme ➔ connective tissue and smooth muscle of the urethra Surface ectoderm ➔ epithelium of the terminal part of the urethra 16 © 2020, Elsevier Inc. All rights reserved.  Urinary bladder Ectopic ureter: Does not enter the urinary bladder ➔ incontinence Males: neck / prostatic utricle Females: neck / urethra / vagina / vestibule Urachal anomalies: Urachal lumen persists Urachal cysts / sinus / fistula Exstrophy of bladder [Epispadias]: 1 in 30 000 / 50 000 (females) Protrusion of mucosal surface of posterior bladder Failure of mesenchymal cells to migrate between the ectoderm and endoderm (rupture of the cloacal membrane) 17 © 2020, Elsevier Inc. All rights reserved.  Genital system Gonadal development (5th week): Mesothelium (mesodermal epithelium) ➔ medial aspect of mesonephros ➔ (with underlying mesenchyme) gonadal ridge Mesenchyme (embryonic connective tissue) ➔ gonadal cords Primordial germ cells (earliest undifferentiated sex cells from the epiblast) ➔ gonadal cords ➔ Oocytes ( ) & sperm ( ) 18 © 2020, Elsevier Inc. All rights reserved.  Genital system Indifferent gonads ➔ external cortex & internal medulla Males [XY] ➔ Medulla: testis; cortex: regresses Females [XX] ➔ Cortex: ovary; medulla: regresses 19 © 2020, Elsevier Inc. All rights reserved.  Relocation Descent of the testes: 7th week ➔ birth Controlled by androgens (testosterone) Gubernaculum: guides the descent of the testes into the scrotum (though the abdominal cavity) Pulls structures involved reproduction and forms the spermatic cord with the processus vaginalis Decent of the ovaries: Descend from the lumbar region to the pelvis Gubernaculum: guides the ovaries and attaches from uterus near the attachment of the uterine tube Forms ovarian and round ligament Development of the Urogenital System. Schoenwolf, Gary C., Ph.D., Larsen's Human Embryology, 20 Chapter 15, 479-541. Copyright © 2009 by Churchill Livingstone, an imprint of Elsevier Inc. © 2020, Elsevier Inc. All rights reserved.  Male genital system Development of the Urogenital System Schoenwolf, Gary C., Ph.D., Larsen's Human Embryology, Chapter 15, 479-541. Copyright © 2009 by Churchill Livingstone, an imprint of Elsevier Inc. 21 © 2020, Elsevier Inc. All rights reserved.  Female genital system Development of the Urogenital System Schoenwolf, Gary C., Ph.D., Larsen's Human Embryology, Chapter 15, 479-541. Copyright © 2009 by Churchill Livingstone, an imprint of Elsevier Inc. 22  External genitalia Males: Urogenital folds fuse and the genital tubercle elongates to form the shaft and glans of the penis. Fusion of the urethral folds encloses the phallic portion of the urogenital sinus to form the penile urethra. The labioscrotal folds fuse to form the scrotum. Females: Genital tubercle bends inferiorly to form the clitoris, and the urogenital folds remain separated to form the labia minora. The labioscrotal folds form the labia majora 23 © 2020, Elsevier Inc. All rights reserved. Resources https://thecomicalanatomist.com/category/urinarysystem/ Before We Are Born: Essentials of Embryology and Birth Defects by Moore, 10th edition, 2020 Fundamentals of Human Embryology By Kramer and Allan Larsen’s Human Embryology by Schoenwolf Thank you to Dr Joshua Davimes for the lecture framework https://thecomicalanatomist.com/category/urinarysystem/