Urinary Session 2- Development Of Urinary Tract & Histology Flashcards
What is the location of the kidneys?
Retroperitoneal each side of the vertebral column between T12 & L3
Where does the kidney’s blood supply come from?
Direct branch of the abdominal aorta
What are the 3 layers of the trilaminar embryo? (Sem 1)
Endoderm
Mesoderm
Ectoderm
What are the areas within the mesoderm after organisation?
Paraxial mesoderm Intermediate mesoderm Somatic mesoderm Splanchnic mesoderm Intraembryonic coelom
After gastrulation, what are the areas where mesoderm does not separate ectoderm and endoderm?
Buccopharyngeal membrane
Cloacal membrane
Which are of mesoderm does the kidney develop from?
Intermediate mesoderm
Name the areas of the urinary system in the order they develop
Pronephros
Mesonephros
Metanephros
What does a nephrotome consist of?
Glomerulus
Bowmans capsule
Proximal and distal convoluted tubule
Collecting duct
What is the function of the pronephros?
Never functions in humans BUT pronephric duct extends from cervical region to cloaca and drives development of next developmental stage
What is the urogenital ridge?
Region of intermediate mesoderm giving rise to the embryonic kidney and the gonad
What structures form the embryonic kidney?
Mesonephric tubules and mesonephric duct
Where do mesonephric tubules develop?
Caudal to the pronephric region
What is the function of the mesonephric duct?
Sprouts the ureteric bud which induces development of definitive kidney
Important role in development of the reproductive system in the male
What is the function of the ureteric bud?
Induces development of definitive kidney within intermediate mesoderm of the caudal region of the embryo
Collecting system is derived from ureteric bud itself
Excretory component is derived from intermediate mesoderm under influence of ureteric bud
How does the ureteric bud form the definitive kidney?
Ureteric bud contacts metanephric blastema
Bud expands and branches forming renal pelvis, major calyx and minor calyx
Describe what occurs during the ascent of the kidney
Metanephric kidney first appears in pelvic region
Undergoes caudal to cranial shift, crossing arterial fork formed by vessels returning blood from foetus to placenta
As kidneys ascend, new blood vessels form and old ones regress
What can occur when kidney formation goes wrong?
Ureteric bud fails to interact with intermediate mesoderm- renal agenesis Migration goes awry Wilm's tumour Duplication defects Ectopic ureter Cystic disease
How do duplication defects occur?
Splitting of ureteric bud- can be partial or incomplete
Symptomatic consequence is ectopic urethral opening
What are the 3 types of cystic kidney disease and their characteristics?
Multicystic kidney disease- atresia of ureter
Polycystic kidney disease- recessive, presents early, poor prognosis
What is the cloaca?
The structure where the GI, urinary and reproductive tracts end
What is the urogenital sinus?
Created from hindgut by urogenital septum to separate anus and urogenital system
Continuous with umbilicus
What are the 3 parts of the urogenital sinus and what will they become?
Largest part = future bladder
Pelvic and phallic parts = parts of future urethra
How is the prostate and prostatic urethra formed in males?
Mesonephric ducts reach urogenital sinus
Ureteric bud sprouts from mesonephric ducts
Smooth musculature begins to appear, UGS begins to expand
Ureteric buds and mesonephric ducts make independant openings in UGS
How does the development of the urinary system differ in females?
As UGS begins to expand, MD begin to regress
MD regress completely- ureteric bud opens into UGS
What is the female urethra formed by?
Pelvic part of urogenital sinus
What are the 4 parts of the male urethra and which part of UGS?
Pelvic part- proprostatic, prostatic, membranous
Phallic part- spongy
What are the basic components of external genitalia?
Genital tubercle
Genital folds
Genital swellings
How do the genitals form in males?
Genital tubercle elongates and genital folds fuse to form spongy urethra
How do the genitals form in the female?
No fusion occurs and urethra opens into the vestibule
What can happen when formation of genitals goes wrong?
Fistulae
Exstrophy of the bladder- bladder opens onto abdominal wall
Ectopic urethral orifices
What is hypospadia?
Defect in fusion of urethral folds
Urethra opens onto ventral surface- not end of the glans
What does the renal corpuscle consist of?
Glomerulus and bowmans capsule
What are the 2 poles of the renal corpuscle?
Vascular pole- Afferent and efferent arterioles (glomerulus)
Urinary pole- Bowmans capsule
What is the function of the renal corpuscle and how does it achieve this?
To produce ultrafiltrate of plasma
Filtration barrier produced by capillary endothelium and visceral layer of bowmans capsule
Describe the structure of the renal corpuscle
Parietal layer of Bowmans capsule = simple squamous epithelium
Visceral layer wraps around capillary endothelium and parietal layer makes funnel to collect ultrafiltrate
Describe the filtration barrier
Capillary endothelium is fenestrated and podocytes invest making filtration slits
Endothelium and podocytes share basement membrane
Describe the basic structure and function of the PCT (epithelium)
Longest most convoluted section of tubule
Reabsorption begins
Simple cuboidal epithelium with pronounced brush border and contain mitochondria
What are the 4 parts of the loop of Henle?
Pars recta
Thin descending limb
Thin ascending limb
Thick ascending limb
Describe the structure of the thin limb
Simple squamous epithelium
No brush border
No active transport
Describe the structure of the thick limb
Simple cuboidal epithelium
No brush border
Active transport
What is the differences between DCT and PCT?
DCT=no brush border and larger lumen
Both contain mitochondria
What does the juxtaglomerular apparatus consist of?
Macula densa of DCT
Juxtaglomerular cells of afferent arteriole of glomerulus
Extraglomerular mesangial cells
Describe the appearance of the collecting duct
Connects to DCT via collecting tubule
Similar appearance to thick limb of loop of Henle but larger and more irregular lumen
What is the renal pyramid?
Progressively larger ducts formed by merging of collecting ducts that empty at renal papilla
Describe the structure of the ureter
Muscular tube- 2 layers of smooth muscle (3rd layer in lower 3rd of ureter)
Lined by transitional epithelium
Describe the structure of the bladder
3 layers of muscle
Outer adventitia
Transitional epithelium
How is urothelium (transitional epithelium) impermeable?
‘Umbrella cells’ on the surface layer
