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WEEK 3:
Embryology of abdominal viscera 2:
| Question | Answer |
|---|---|
| derivatives of the hindgut include (7) | Left 1/3 to 1/2 of the transverse colon, Descending colon, Sigmoid colon, Rectum, Superior part of the anal canal, and epithelium of urinary bladder and most of urethra |
| the cloaca partitions into (2) | anorectal canal and urogenital sinus |
| ectoderm + endoderm contact makes | cloacal membrane |
| cloaca | distal expansion of hindgut, the primitive anorectal canal |
| why does the cloacal membrane fold/ vaginate | due to the contact of the urorectal septum |
| allantois | primitive urogenital sinus |
| cloacal membrane | boundary between endoderm and ectoderm |
| urorectal septum | mesodermal of origin separating hindgut from allantois |
| space between urogenital sinus and rectum | perineal body will form here |
| embryological origin of upper part of anal canal | endoderm |
| embryological origin of lower part of anal canal | ectoderm |
| upper part of anal canal arterial supply | Superior rectal (a branch of inferior mesenteric artery |
| upper part of anal canal venous drainage | Superior rectal (portal venous system) |
| upper part of anal canal histology | Simple columnar |
| lower part of anal canal arterial supply | Inferior rectal (a branch of internal pudendal artery) |
| lower part of anal canal venous drainage | Inferior rectal (systemic venous system) |
| lower part of anal canal histology | Stratified squamous |
| urorectal septum grows down into | cloaca |
| the urorectal spetum grows down into the cloaca which divides what | urogenital sinus (anteriorly) from hindgut (posteriorly) |
| urogenital sinus differentiates into | urinary bladder (above urethra) |
| end of mesonephric ducts become part of | bladder wall (so that ureters open directly into bladder) |
| apex of bladder continuous with | |
| allantois becomes | |
| urachus involved with | |
| fistula | |
| genitourinary system consists of what systems (2) | urinary system and reproductive system |
| urinary and reproductive system both develop from | intermediate mesoderm |
| types of mesoderm (3) | paraxial mesoderm, intermediate mesoderm, and lateral plate mesoderm |
| urogenital ridge split into | nephrogenic cord (urinary system) and gonadal ridge (genital system) |
| nephrogenic cord | comes from urogenital ridge becoming the urinary system |
| gonadal ridge | comes from urogenital ridge becoming the genital system |
| pronephros | appears briefly in cervical region |
| mesonephros develops where | in thoracic and upper lumbar regions |
| mesonephros | transient in humans and has some glomeruli and a duct (mesonephric/ wolffian duct) |
| during the 5th week, metanephros develops where | sacral region (is the definitive kidney) |
| metanephros begins as | uretic bud growing into intermediate mesoderm from lower end of mesonephric duct |
| ureter and renal pelvis develops when | when ureteric bud forms a tube (ureter) and its expanded end becomes the renal pelvis |
| growing tips divide repeatedly to form (4) | major calyces, minor calyces, collecting ducts, and collecting tubules |
| groups of metanephric cells gather around the collecting tubules and form | nephrons |
| uretic bud forms (5) | • Ureter • Renal pelvis • Major calyces • Minor calyces • Collecting ducts |
| metanephric mesoderm forms (5) | • Distal convoluted tubule • Loop of Henle • Proximal convoluted tubule • Bowman’s capsule • Glomerulus |
| commonest causes of end stage renal failure in young children (5) | Renal agenesis (absence) & dysplasia (not fully developed), Ectopic kidney, Horseshoe kidney, Double ureter or Bladder exstrophy (bladder outside abdomen) |
| gonads develop in which position | anterior surface of mesonephros |
| gonads are closely related to | |
| gonads quickly become infiltrated by | |
| primordial germ cells multiply where | wall of yolk sac |
| primordial germ cells migrate to | developing gonads (after multiplying in yolk sac wall) arriving about 6 weeks after conception |
| migrating primordial gonads arrive in gonads about | 6 weeks after conception |
| paramesonephric ducts/ mullerian ducts | develop near mesonephros, are cranially open to abdominal cavity and caudally they end near midline in urogenital sinus where they degenerate in males and persist in females |
| difference in paramesonephric ducts/ mullerian ducts in males and females | degenerate in males but persist in females |
| what secrete a testis determining factor (TDF) in males | SRY gene on the Y chromosome (sex determining region) |
| role of SRY gene on Y chromosome | ats as the sex determining region - if it is present the gonad will become a testis and the paramesonephric (Mullerian) ducts will degenerate/ if not the gonad becomes an ovary and mesonephric (Wolffian ducts) degenerate instead |
| if SRY gene present on Y chromosome | gonad will become a testis and the paramesonephric (Mullerian) ducts will degenerate |
| if SRY gene not present on Y chromosome | gonad becomes an ovary and mesonephric (Wolffian ducts) degenerate instead |
| role of parameonephric (Mullerian) ducts in females | form fallopian tube, uterus, cervix and upper part of vagina |
| lower part of vagina develops from | sinovagina bulbs |
| paramesonephric ducts possible genital tract defects | lack of fusion can lead to uterus bicornis (2 unteruses) and complete/ partial atresia (atresia of cervix or vagina meaning they are closed fully) |
| mesonephros becomes what in males | testis |
| mesonephric duct forms what in males | duct through which spermatozoa reach the urethra and its associated glands (epididymis, vas deferens, seminal vesicle and ejaculatory duct) |
| gubernaculum | fibrous cord which links the lower pole of testis to developing lower abdominal wall and also interrupts the developing muscles forming a defect (inguinal canal) |
| growth of gubernaculum | does not grow as it only anchors testis which is gradually pulled downward as the fetus grows (so goes down due to growth doesnt actually grow) |
| when does the testis reach the scrotum | by birth/ shortly afterwards |
| spermatic cord includes (4) | vas deferens, testicular vessels, nerves and lymphatics |
| processus vaginalis | forms when gubernaculum pulls a small outpouching of peritoneum |
| appearance of processus vaginalis | normally disappears except for its lower extremity which forms the tunica vaginalis around testis |
| tunica vaginalis | |
| cryptorchism | |
| developmental abnormalities associated with descent of testis (2) | |
| incomplete descent of testis | |
| maldescent | |
| urethra ends as | |
| S29 | |
| formation of labia majora | |
| formation of clitoris | |
| genital tubercle becomes | clitoris |
| labia minora formation | |
| vestibule found where | |
| opening of urethra and vagina found where | |
| hypospadias | |
| epispadias | |
| ectopia vesicae or extrophy of bladder | |
| horseshoe kidney | forms when caudal end of kidneys fuse in midline and account for 90% of fused kidneys and this ascends until its path is blocked by inferior mesenteric artery |
Created by:
22tango
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