Hello everyone, welcome to my channel Today we are going to give the embryology of the Urogenital System first part The urogenital system is a complex of related organs with very diverse functions such as the elimination of metabolic waste material and the reproduction of the species This system therefore includes the urinary and genital organs. In this image we can see a dorsal view of an embryo during the third week if we make a cross section it is possible to observe three types of mesoderm the lateral, intermediate and paraxial mesoderm The Urogenital System comes from the intermediate
mesenchyme and during the folding of the embryo in a horizontal plane this mesoderm is displaced in a ventral direction and loses its connection with the somites On the other hand, a longitudinal elevation of the mesoderm rises on each side of the dorsal aorta called urogenital crest The part of the urogenital ridge, which gives rise to the urinary system is the Nephrogen Cord Development of the Urinary System Starts to develop before the genital system and this is formed by the Kidneys that excrete urine the ureters that carry urine from the kidneys to the urinary bladder the
urinary bladder that stores urine temporarily and the urethra that carries urine from the bladder to the outside of the body Development of the kidneys and ureters Three kidney systems appear in human embryos at the cervical level, Pronephros, which are rudimentary systems and their structure lack function at the thoracic and lumbar level, there are the Mesonephros that are well developed and work for a short time and the third system is located at the pelvic level and are the Metanephros that become the ultimate Kidneys At the beginning of the fourth week the pronephros is represented by 7
or 10 compact cell groups The groups form vestigial excretory units called Nephrotomes that recede before other more flows are formed Towards the end of the fourth week all signs of the pronéphric system have disappeared During regression of the pronéphric system the first excretory tubules of the mesonephros appear which lengthen and flex an S-shaped handle and create a network of capillaries that will form a glomerulus at its medial extremity Around the glomerulus the tubules form Bowman's capsule and together these structures constitute the renal corpuscle Laterally the tubule is introduced into the Longitudinal Collecting Duct known as
mesonephric duct or Wolffian duct The Methane or primordia of the permanent kidneys begin to form at the beginning of the fifth week and start to work about four weeks later Permanent kidneys have two origins The ureteral outline or metanephric diverticulum and the metanephrogen blastema The metanephric diverticulum is an outgrowth of the mesonephric conductor near its entry into the cloaca and metanephrogen blastema derives from the caudal part of the nephrogenic cord As the metanephric diverticulum increases in length penetrates the metanephrogen blastema The pedicle of the metanephric diverticula becomes the ureter and the cranial portion of the
diverticulum undergoes several branching processes giving rise to branches that differ in collecting tubules of the metanephros The first four generations of tubules increase in size and converge to form the major calyces and the next four generations fuse to form the lesser calyces The end of each arcuate collecting tubule induces mesenchymal cell aggregates in the metanephrogen blastema to form small metanephric vesicles these vesicles elongate and become metanephric tubules the proximal ends of these tubules are invaginated by the glomeruli and the tubules differentiate into proximal and distal convoluted tubules The loop of the nephron together with the
glomerulus and Bowman's capsule form a nephron which is the basic functional structural unit of the kidney and approximately one million are formed by birth in each kidney At birth the kidneys have a lobulated appearance but lobulation disappears during childhood as a result of later growth of the nephrons although these do not increase the number Kidney position in an initial stage the kidneys are located in the pelvic region and later move to a more cranial position in the abdomen This rise of the kidney is caused by the decrease in the curvature of the body as well
as its growth in the lumbar and sacral regions Development of the bladder and urethra As an introduction to the fourth the seventh week of development cloaca divides anteriorly into the urogenital sinus and posteriorly into the anorectal duct The urorectal septum is a layer of the mesoderm that is located between these two and at its end will form the perineal body In the Urogenital Sinus you can distinguish three portions The bladder part that make up most of the bladder and is in continuity with the allantois The pelvic part that becomes the urethra, the bladder neck, postatic
urethra in men and urethra in women And the phallic part that grows towards the genital tubercle The bladder comes mainly from the bladder portion of the urogenital sinus but the portion of the trigone derives at the caudal ends of the mesonephric ducts At first the bladder maintains continuity with the allantois but soon, it contracts and turns into a thick fibrous cord called Uraco In the adult, the Urachus is represented by the Middle Umbilical Ligament As a result of the rise of the kidneys, the orifices of the ureters are displaced even more cranially and the orifices
of the mesonephric ducts approach each other to be able to penetrate the prostatic urethra In the male they will form the ejaculatory ducts, whereas in the female the distal ends of the mesonephric ducts degenerates Urethral epithelium The epithelium of most of the male urethra and the entire female urethra derives endoderm from the Urogenital Sinus Towards the end of the third month, the epithelium of the prostatic urethra begins to proliferate and several evaginations arise that are introduced into the surrounding mesenchyme In the male these outbreaks will originate in the Prostate Gland and in women, in the
cranial portion of the urethra, it gives rise to the urethral and paraurethral glands As an example of congenital anomalies of the Renal System we have renal agenesis, duplication of the ureter, pelvic kidney, cross ectopia, and horseshoe kidney Well, and that's all the first part of the embryology of the urogenital system would understand. this part was, the development of the urinary system in the next we will give the development of the genital system don't miss the next video
