CLINICAL EMBRYOLOGY OF THE KIDNEYS, URINARY BLADDER AND URETERS Flashcards
Structures of the Renal (Urogenital) System are derived from two germ layers:
mesoderm
endoderm
what 3 layers is the mesodermal germ layer divided into
paraxial mesoderm
intermediate mesoderm
lateral plate mesoderm ( subdivided into somatic and splanchnic mesoderm)
IDENTIFY THE PRIMARY EMBRYONIC GERM LAYERS THAT GIVE RISE TO THE FOLLOWING REPRODUCTIVE SYSTEM STRUCTURES:
uterine tube
mesoderm
IDENTIFY THE PRIMARY EMBRYONIC GERM LAYERS THAT GIVE RISE TO THE FOLLOWING REPRODUCTIVE SYSTEM STRUCTURES:
uterus and uterine canal
mesoderm
IDENTIFY THE PRIMARY EMBRYONIC GERM LAYERS THAT GIVE RISE TO THE FOLLOWING REPRODUCTIVE SYSTEM STRUCTURES:
vagina
mesoderm and endoderm
IDENTIFY THE PRIMARY EMBRYONIC GERM LAYERS THAT GIVE RISE TO THE FOLLOWING REPRODUCTIVE SYSTEM STRUCTURES:
urethra
endoderm
IDENTIFY THE PRIMARY EMBRYONIC GERM LAYERS THAT GIVE RISE TO THE FOLLOWING REPRODUCTIVE SYSTEM STRUCTURES:
external genitalia
endoderm
what is the renal collecting ductal system made of
Ureters
Renal pelvis
Major calyces
Minor calyces
Collecting tubules.
what is the renal excretory ductal system made of
the nephron renal corpuscle - glomerulus , bowman capsule PCT loop on henle DCT
what is the mesonephric duct
connects primitive kidney ( mesonephros) to the cloaca and serves as the anlage(the rudimentary basis of a particular organ or other part, especially in an embryo) for certain male reproductive organs
what is the cloaca
The term describing the common cavity into which the intestinal, genital, and urinary tracts open in vertebrates. Located at the caudal end of the embryo it is located on the surface by the cloacal membrane
the mesonephric system is made from the mesodermal germ layer structure and contributes to formation of what
renal tubules ureter reproductive ductal system uterine canal vagina
the cloaca is part of the distal portion of the embryonic hindgut and is part of the endodermal germ layer structure and contributes to the formation of what
urinary bladder
urethra
vagina
external genitalia
Haeckel’s Biogenetic Law: “Ontogeny recapitulates Phylogeny”.
what is meant by this
an example of this is the Development of the urinary system
Pronephros - functional kidney in primitive fish
Mesonephros - functional kidney in advanced fish such as aquatic vertebrates
Metanephros - functional kidney in humans
The theory of recapitulation, also called the biogenetic law or embryological parallelism—often expressed using Ernst Haeckel’s phrase “ontogeny recapitulates phylogeny”—is a historical hypothesis that the development of the embryo of an animal, from fertilization to gestation or hatching (ontogeny), goes through stages resembling or representing successive adult stages in the evolution of the animal’s remote ancestors (phylogeny)
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In the embryo, the kidneys develop from three overlapping sequential systems; the pronephros, the mesonephros, and the metanephros. They are all derived from what
urogenital ridge
the pronephros
A transient vestigial excretory unit – nephrotomes, derived from the intermediate mesoderm.
Appear at the beginning of the 4th week and regress by the end of the 4th week.
when does this start and regress
what germ layer does it derive from
what duct is formed and where is this duct found and connected by
appears in the 4th week of development
begins in the cervical region of the embryo - segmented divisions of intermediate mesoderm from tubules known as nephrotomes( 6-10 formed)
These join into the pronephric duct which is the duct that cervical region to the cloaca ( distal end) of the embryo.
Because this is an early system and therefore cannot be functional it regresses completely by the end of week 4
Derived from the intermediate mesoderm which also gives rise to the mesonephric (Wolffian or nephric) ducts.
The mesonephric ducts give rise to primitive excretory tubules with tuft of glomerular capillaries around which it forms the primitive Bowman’s capsule.
These structures together constitute a primitive renal corpuscle that drain into the mesonephric or Wolffian or nephric ducts.
The mesonephric ducts also give rise to the ureteric buds.
The developing gonad lies on the medial side of each developing Mesonephros, both of them form a common ridge called Urogenital Ridge.
the mesonephros develops caudually ( inferior) to the pronephros. Its formation induced by the pronephric duct ( intermediate mesoderm- this is in the thoracolumbar region to form the mesonephric tubules).
mesospheric duct is a continuation of the pronephric duct
most of these tubules regress by the end 8 week mark
additionally the mesonephric duct sprouts the ureteric bud caudally, which induces the development of the definitive kidney.
Metanephros.
when does a permanent kidney arise?
when does the kidney become functional ?
A permanent kidney, appears in the fifth week of development.
Gives rise to the definitive excretory units in the same manner as the mesonephric system.
This constitute the permanent kidney ductal system.
the metanephros forms the definitive kidney - appears at 5th week and becomes functional at around the 12th week
the uteric bud from the mesonephric duct makes contact with caudal region of metanephric
what is the collecting system derived from
what do the collecting tubules converge on forming what
uteric bud
dilates to create ureter , renal pelvis , major and minor calyces and 1-3mill collecting tubules terminating at the DCT
collecting tubules converge on the minor calyces forming renal pyramids
what is the excretory system derived from
metanephric blastema
each collecting tube gives rise to excretory tubules
nephron
proximal end from the bowman capsule around the glomerulus with the distal end elongating to from the PCT, loop of henle and DCT
s shaped
at 1 end of each of the renal tubules - surround the caps diff to form glomerulus
the glomerulus indents that end of renal tubule to from bowman
other end forms stuff mentioned above
where does the definitive kidney initially develop
in the pelvic region before ascending into the abdomen
the kidney receives its blood supply from a pelvic branch of hat
abdominal aorta
these pelvic arteries regress but can resist as accessory renal arteries
what is a horseshoe kidney
2 developing kidneys fuse into a single horseshoe shaped structure - this occurs if the kidneys become too close together during their ascent from the pelvis to the abdomen
and become stuck under the inferior mesenteric artery
The definitive structures of the human kidney system are derived from two embryonic sources
what are they
The Ureteric bud which arise from the Mesonephric duct of the Mesonephric mesoderm (the Mesonephros), gives rise to the Collecting system.
The Metanephric blastema of the Metanephric mesoderm (the Metanephros), gives rise to the Excretory units.
when does urine production begin
12th week
urine passed into amniotic cavity and mixes with amniotic fluid
fluid swallows by foetus and recycled through the kidneys
during fetal life the kidneys are not responsible for excretion of waste products because the placenta serves this function
at birth what appearance to the kidneys have
lobulated appearance but the ovulation disappears during infancy as a result of further growth but with no increase in number of the nephrons
what is the ascent of the kidneys caused by
diminution of body curvature and growth of the body in the lumbar and sacral regions
vessels that supply the metanephros normally degenerate as lower but if they remain what are they called
accessory vessels
Accessory renal arteries are common, derived from the persistence of the embryonic vessels and enter the superior or inferior poles of the kidneys.
what is a wiles tumour
A cancer of the kidneys that usually affects children by 5 years of age but may also occur in the fetus.
Due to mutations in the WT1 gene on 11p13.
May be associated with other abnormalities and syndromes such as Wilms, Aniridia, Gonadoblastoma, and mental Retardation (WAGR), and Denys-Drash.
what is WAGR syndrome due to micro deletion in what chromosome
11 that include PAX6 (Aniridia) and WT1 genes.
what does Denys drash syndrome consist of
Denys-Drash syndrome consist of renal failure, ambiguous genitalia and Wilms tumor.
dysplasia
the presence of cells of an abnormal type within a tissue, which may signify a stage preceding the development of cancer.
causing abnormal formation or development of a tissue or organ
Agenesis
refers to the failure of an organ to develop during embryonic growth and development due to the absence of primordial tissue.
renal dysplasias and agenesis
Spectrum of severe malformations, that require dialysis and transplantation in the first year of life.
Renal agenesis may also arise if the interaction between the metanephric mesoderm and the ureteric bud fails to occur.
Multicystic dysplastic kidney
An abnormality in which numerous ducts are surrounded by undifferentiated cells.
Nephrons fail to develop, and ureteric bud fails to branch, so collecting ducts never form.
In some cases, these defects may cause involution of the kidneys and renal agenesis.
what is potter sequence characterised
anuria, oligohydramnios, and hypoplastic lungs secondary to oligohydramnios.
In 85% of cases, other severe defects, including absence or abnormalities of the vagina and uterus, vas deferens, and seminal vesicles, accompany this condition.
Common associated defects in other systems include cardiac anomalies, tracheal and duodenal atresias, cleft lip and palate, and brain abnormalities.
Because of the oligohydramnios, the uterine cavity is compressed, with a characteristic appearance of the fetus, including a flattened face (Potter facies) and club feet.
Congenital Polycystic Kidney Disease (PKD)
numerous cysts form
May be inherited as an autosomal recessive or dominant disorder or caused by other factors.
kidneys become very large and renal failure occurs in infancy or childhood
what is Autosomal recessive polycystic kidney disease (ARPKD), occurs 1:5,000 births.
Is a progressive disorder in which cysts form from collecting ducts.
The kidneys become very large, and renal failure occurs in infancy or childhood.
there is also a dominant version which is 1:500 so more common
Cysts form from all segments of the nephron and usually do not cause renal failure until adulthood.
Less progressive than ARPKD.
what is the ureter
The tube that carries urine from the kidney to the bladder.
duplication of the ureter results from early splitting of what
ureteric bud ( partial or complete split) each ureter may have its own renal pelvis and more kidney lobes in rare cases one goes to bladder and other could go ectopic and enter vagina - could result from 2 steric buds , one stays in normal position whereas other moves down with the mesonephric duct
the kidneys can be located in abnormal positions
what is a pelvic kidney
and is close to what structure
One of the kidney may fail to ascend to its definitive adult position and remains in the pelvis close to the common iliac artery.
what is a horshoe kidney
The kidneys may be very close together such that their lower poles fuse.
during ascent usually arrested at lower lumbar vertebrae by root of inferior mesenteric artery
ureters arise from antihero surface of kidneys and pass ventral to isthmus of fused poles
in the development of the urinary bladder and urethra there is the cloaca
what is this
An enlarged common sac for the lower parts of the hind gut and its diverticulum, called allantois - endodermal structure
during the 4-8th weeks the cloaca is divided by the urorectal septum into what
urogenital sinus anteriorly
anal canal posteriorly
what does the urogenital sinus form
urinary bladder- upper and larger part of the sinus
initially this is continuous with the allantois
the lumen of the allantois obliterates later on leaving what which connects the apex of the bladder with the umbilicus
urachus
what is this?
in adults what does the urachus form
umbilical ligament - function of this ?
in a male what does the pelvic part of the urogenital sinus form
prostatic and membranous parts of the urethra
what is the trigone and how is it formed
smooth triangular region of the internal urinary bladder formed by the two ureteric orifices and the internal urethral orifice. The area is very sensitive to expansion and once stretched to a certain degree, the urinary bladder signals the brain of its need to empty.
caudal portions of the mesonephric ducts later become absorbed into the wall of the urinary bladder to form the trigone
this causes the ureters to enter the urinary bladder separately
the mucosal lining of the region of the urianry bladder is from what germ layer
however over time what does this change to
mesodermal as both the mesonephric ducts and ureters originate in the mesoderm
however with time the mesodermal lining of the trigone become replaced by endodermal epithelium, so that the inside of the urinary bladder including the trigone is completely lined with endodermal epithelium.
in males where do the ejaculatory ducts form from
mesonephric ducts move closer together to enter prostatic urethra
the epithiulm of the urethra in both sexes originate from what germ layer
endoderm - surrounding connective tissue and smooth muscle tissue is derived from the visceral mesoderm.
what is Urachal Fistula
what common Sx
Formed when the lumen of the intraembryonic portion of the allantois persists.
May cause urine to drain from the umbilicus.
what is a urachal cyst formed how
when only a localised area of the allantois persists, and secretory activity of its lining results in cystic dilation
what is a urachal sinus
Formed when the lumen in the upper part of the allantois persists.
The urachal sinus is usually continuous with the urinary bladder.
Exstrophy of the urinary bladder and Epispadias:
Is a ventral abdominal wall defect in which the urinary bladder mucosa is exposed.
Epispadias is a constant feature of Exstrophy of the urinary bladder.
The open urinary tract extends along the dorsal aspect of the penis through the urinary bladder to the umbilicus.
Exstrophy of the urinary bladder is probably due to failure of the lateral body wall folds to close in the midline in the pelvic region.
Exstrophy of the Cloaca:
More severe ventral body wall defect.
Progress and closure of the lateral body wall folds are disrupted.
Normal development of the urorectal septum is also altered such that anal canal malformations and imperforate anus occur.
Defects in the external genitalia also occur.
