Week 8 HRM Urinary Anatomy Flashcards
What does retroperitoneal mean?
Situated behind the peritoneum (the CT serous membrane that contains the abdominal contents) The kidneys are located retroperitoneal
What are the different components of the urinary system?
Kidneys, ureters, bladder and urethra
At what level of the spine are the kidneys located?
T12 - L3
Why is the the right kidney located slightly more inferiorly than the left?
The liver prevents the right kidney from ascending as far as the left
What are the various functions of the kidney?
Production, storage and excretion of urine Excretion of metabolic wastes Regulation of water levels and acid/base Regulation of arterial pressure Secretion of hormones (I.e. EPO, renin)
What are the 3 distinct regions of the kidney (as seen in a coronal cross section)?
Cortex
Medulla
Pelvis
What is the renal cortex? What structures are usually found there?
The outermost layer of the kidneys, which is covered by a fibrous capsule. Contains glomerulosa, PCT, DCT
What is the renal medulla and what structures are usually found there?
Medulla is located deep to the cortex and predominantly contains the Loop of Henle and the collecting ducts
What is the medial border of the kidney known as?
The hilum
What are the renal columns?
Columns of cortex that sit between the pyramids of medulla. These form the distinct lobes - usually 8.
What is the renal papilla?
The apex of the pyramids of medulla where urine travels out if the collecting ducts into papillary ducts
What are the minor and major calyces?
Where papillary ducts initially converge to form minor calyx. Where minor calyces merge leads to the formation of a major calyx
Why do the calyces contain smooth muscle?
To help move Urine along via peristalsis
When looking at a histological section - how can you differentiate between cortex and medulla?
The presence of glomerulosa. Areas where these are present are the cortex, and where absent is the medulla.
What major artery supplies the kidneys, and what large vessel has it branched from?
The renal artery - branched directly from the abdominal aorta
Why is the right renal artery longer than the left?
The aorta runs left of the midline, so the renal artery will travel further to reach the right kidney. The left renal vein will be longer as IVC is right of the midline
Where does the renal artery branch, and what is the branch called?
In the renal pelvis. Segmental arteries
Describe the blood flow into the kidneys from the segmental arteries through to the peri tubular capillaries and vasa recta:
Segmental –> interlobar –> arcuate –> interlobular –> afferent arteriole –> glomerulosa –> efferent arteriole –> peritubular and vasa recta
What is the function of the peritubular capillaries?
Associated with the convulsed tubules - allow for reabsorption
Where is the vasa recta capillaries located?
Associated with nephron loop
Which capillaries feed into the interlobular vein?
Peritubular and vasa recta
What is the only difference in the kidney venous system compared to the arterial system?
There are no segmental veins - straight from interlobar to renal vein
What percentage of cardiac output flows through the kidneys?
20-25%
What are the four components of a nephron?
Renal corpuscle (glomerulus + capsule)
Proximal convoluted tubule
Nephron loop (Henle)
Distal convoluted tubule
What are the 2 types of nephrons?
Cortical and juxtomedullary
Describe cortical nephron?
Contained mainly within the cortex, short nephron loops barely enter the medulla. Make up 70% of all glomeruli.
Describe juxtomedullary nephron?
Corpuscles lie close to the base of the pyramid . Long loops of Henle extend deep into medulla.
What is the function of the glomerulus?
Network of capillaries where blooded filtration occurs. Blood goes into the glomerulus and fluid is pushed out due to the higher pressure of the afferent arterioles.
Why is blood leaving the glomerulosa still said to be arterial?
Gas exchange didn’t take place in the glomerulosa, just the filtration. This blood will then go onto perfume the kidney itself.
What is the Bowman’s/nephron capsule?
Capsule made of epithelial cells which contains the blood filtrate. Parietal layer made of simple squamous epithelia. Visceral layer composed of podocytes which reside on the glomerulosa capillaries
What is the role of podocytes in blood filtration?
They have cytoplasmic projections called pedicels which wrap around the capillaries (which are fenestrated) and create filtration slits for fluid to pass through into the capsule
What occurs in the PCT?
Composition of filtered fluid changes as nutrients and vitamins are re absorbed into circulation (I.e. Glucose, amino acids, proteins etc). Re absorbed nutrients diffuse back into the peritubular capillaries
What is the major histological difference between the PCT and the DCT?
PCT has well defined brush border / micro villi, whereas the DCT has very little.
What are Mesangial cells?
Cells which are surrounded by glomerulus capillaries , secrete matrix which forms basement membrane structure between the capillaries.
What hormone determines water reabsorption at the DCT, and where is it secreted from?
ADH, secreted from posterior pituitary gland
Leads to formation of more concentrated urine
How long are the ureters on average? Describe how the ureters enter the bladder?
25cm
Ureters enter obliquely and posteriorly into the bladder
What type of epithelial lines the ureters?
Transitional epithelia (impermeable to salts and water)
How many layers of smooth muscle in the ureters, and how does that thickness change throughout their descent through the abdomen?
Outer circular layer and inner longitudinal layer. Smooth muscle gets thicker the more distal from the kidneys.
Where does the ureters get their blood supply from?
Renal arteries, aorta, common iliac, internal iliac arteries
How does the orientation of the ureters entering the bladder help prevent infection?
because they enter obliquely, when the bladder becomes distended, it squashes the ureter and prevents backflow of urine from the bladder back to the kidneys
What is the ruga?
The mucosal lining of the bladder lumen, lined by transitional epithelium. Very folded when empty, and stretched when bladder is full
What type of connective tissue is the sub muscosal layer of the bladder composed of?
Dense irregular connective tissue (helps support the bladder)
How many layers of smooth muscle in the bladder?
3 layers, collectively known as the detrusor muscle
Where are the two sphincters of the urinary system found?
Neck of the bladder, involuntary sphincter
Voluntary sphincter located within the levator ani group at the urogenital hiatus
Name the different sections of the urethra in males:
Pre-prostatic
Prostatic
Membranous
Spongy
Where are the 3 most common sites for kidney stones to become lodged?
Exiting their renal pelvis
Crossing the pelvic brim/inlet
Entering the bladder
At what point does the urethra join with the ductus deferents in males?
as it travels through the prostate
What is the length of the urethra in women?
4 cm
Describe the epithelia in the urethra?
Changes from transitional epithelia more proximally to become stratified columnar, then to stratified squamous (more sudden transition in females due to shorter distance of urethra)
What substances when found in the urine indicate some underlying pathology in the kidneys?
Glucose (diabetes)
Red blood cells (inflammation, trauma, cancers)
White blood cells (infection)
Proteins (indicates damage to tubules, high blood pressure)
What two germ layers lead to the formation of the urinary system?
Mesoderm and endoderm
What germ layer forms the kidneys and the ureters?
Mesoderm
What germ layer forms the bladder and urethra?
What is the exception to this statement?
Endoderm
The trigone of the bladder is formed by mesoderm
How can you define where the trigone is?
Smooth mucosal area which is marked out as a triangle by the three entry points of the ureters and the urethra
What are the 3 different developmental kidneys that form in foetal life?
Pronenephros
Mesonephros
Metanephros
In what direction does the pronephros and mesonephros grow?
Cranially to caudally
Which primitive kidney degenerates without functioning?
Pronephros
What do the mesonephroi become once the Metanephric kidneys begin formation?
Mesonephric ducts - go on to form the ductus deferens in males, and the round ligament in females
What is the primitive bladder known as?
Urogenital sinus
What does the uterus bud form and from what structure does it originate?
Forms the ureters, and originated from the Mesonephric ducts
Why is the collecting ducts not considered a part of a nephron?
Because it develops separately from nephrons and fuses later on.
What is kidney agenesis?
Where the is no kidneys formed in foetal life. If bilateral it won’t be compatible with life
What is the function of urothelium?
To protect underlying cells from urine toxicity
What is hydronephrosis and hydroureter?
Dilation of the renal pelvis and calyces
Dilation of the ureters
Both of these occurring due to inflammation causes by an interruption to the flow of urine
How is the bladder formed?
The cloaca becomes divided into two by the urorectal septum. This forms form the urogenital sinus and the rectal pouch. The urogenital sinus goes on to form the bladder
What is the fate of the allantois?
Initially continuous with bladder, constricts and becomes urachus (extending from the apex of the bladder to the umbilicus) it then becomes known as the umbilical ligament in adults
