1.2 anatomy of the urinary system Flashcards
What are the main functions of the kidney?
Excretion
Regulation
Endocrine
Matebolism
What is the regulatory functions of the kidneys?
Body fluid volume and ionic compounds
Homeostasis
Acid-base balance (DCT)
What is the endocrine function of the kidney?
Synthesis of:
renin (blood pressure and sodium balance),
erythropoietin (erythrocyte production)
prostaglandins (involved in regulation of renal function)
What is the metabolic role of the kidneys?
Vitamin D is metabolized to its active form, impacting calcium absorption.
Major site for catabolism of low-molecular-weight proteins. Including:
• Insulin
• Parathyroid hormone
• Calcitonin
Where are the kidneys located?
Retroperitoneum on the posterior abdominal wall, either side of the vertebral column. Located between the t12 and L3 vertebrae, with the hilum roughly at L1
Why is the left kidney higher up than the right?
Because the liver pushes the right kidney downwards
How large is a normal kidney?
11cm long x 6cm wide
140g
What layers surround the kidney?
From proximal to distal: Renal capsule Perirenal fat Renal fascia Pararenal/paranephral fat
Describe the blood supply to the kidneys?
Renal veins drain directly into the IVC
Abdominal aorta branches off left and right renal arteries.
Left renal vein passes anterior to the aorta.
Right renal artery runs behind the IVC
Renal arteries usually divide to from an anterior and posterior branch
What are the 2 common types of nephrons? Which is more common?
Cortical nephron (85%) Juxtamedullary nephron (15%)
How do juxtamedullary nephrons vary from cortical nephrons?
Juxtamedullary nephrons have longer loops of henle that descend into the medulla of the kidney, allowing more water to be reabsorbed.
What are the 2 components of a renal corpuscle?
Glomerulus
Bowmans capsule
What are peritubular capillaries?
Capillaries that surround the cortical nephron and the top of the juxtamedullary nephrons
What are arcuate arteries?
Small Arteries in the kidney that give off smaller branches to supply nephrons
What surrounds the loop of henle?
The vasa recta, a capillary network
What surrounds the glomerulus within the bowmans capsule?
Podocytes
Extraglomerular mesangial cells
What is the function of extraglomerular mesangial cells?
Pass messages
Secrete substances
Support the capillary network
What is the juxtaglomerular apparatus?
Formed from the macula densa cells in the DCT and the granular cells lining the afferent and efferent arterioles.
Why is it important that the DCT lies in close proximity to the renal corpuscle?
So that the macula densa cells lie close to the granular cells and can send signals.
What is the function of the juxtaglomerular apparatus?
To regulate flow of blood through the kidney based on composition of the filtrate.
What is the role of macula dense cells?
Detects water osmolality / composition (based on sodium concentration) and sends signals to the granular cells
What is the role of the granular cells?
To produce renin, causing construction of afferent of efferent arteriole to change the flow of blood through the glomerular
What landmark can be used to find the renal arteries?
Superior mesenteric artery
Branches from aorta just before the renal arteries. Runs anteriorly and runs over the top of the left renal vein
Describe the path of blood from the aorta to the vasa recta
Aorta Renal artery Segmental artery Interlobar artery Arcuate artery Interlobular artery Afferent arteriole Glomerulus Efferent arteriole Vasa recta
Describe the path of blood from the vasa recta to the IVC
Vasa recta Interlobular veins Arcuate vein Interlobar vein Segmental vein Renal vein IVC
What are ureters?
Tubes of transitional epithelium with surrounding smooth muscle running from the renal pelvis to the bladder.
What is the role of the ureters?
To propel urine from the renal pelvis to the urinary bladder. Smooth muscle fibres contract in peristaltic waves.
What are the size of the ureters?
25–30 cm long diameter
~ 1.5 mm wide
Which bony landmarks could you use on an X-ray to approximate the course of the ureter?
L1 ~ the hilum
Ureter runs along close to the tip of lumber transverse processes,
Often crosses the sacrum at approximately the SI joint and descends into the pelvis.
The ischial spine is a secondary bony land mark that shows the approximate point at which the ureter ‘kink’ towards the bladder
The ureters then run around the pelvis and enter the bladder posteriorly.
What are the divisions of the ureters?
proximal (abdominal) middle (pelvic) distal part (intramural)
Where is the most common area of ureteric injury?
Near the pelvic brim
What is the muscle of the bladder?
Detrusor
What is the structure of the inner surface of the bladder?
Lined with transitional epithelium
Rough folds called reggae to allow expansion
Trigone located at the posterior inferior aspect
What is the trigone?
smooth triangular region of the internal urinary bladder formed by the two ureteric orifices and the internal urethral orifice. No rugae
Describe the variation in embryological origin within the bladder.
Embryologically, the trigone of the bladder is derived from the caudal end of mesonephric ducts, which is of intermediate mesodermal origin (the rest of the bladder is endodermal from the hindgut). In the female the mesonephric ducts regress, causing the trigone to be less prominent, but still present.
What is the vesico-ureteral junction?
Where the ureters enter the bladder obliquely at the posterolateral surface to form a flap covering the entry of the ureters into the bladder. Acts to stop reflux up the ureters from the bladder
How much fluid can a bladder ordinarily hold?
750ml
What structure allows females to have conscious control over continence?
External sphincter within the urogenital diaphragm
Describe the different divisions of the urethra of a male?
Prostatic urethra Membranous urethra Bulbous urethra Penile/spongy urethra Navicular fossa
What is the navicular fossa?
navicular fossa is the spongy part of the male urethra located at the glans penis portion. It is essentially the part right before the external urethral orifice. It is lined by stratified squamous, non-keratinizing epithelium when viewed histologically.
The kidneys may have aberrant arteries, what does this mean?
Additional non-typical arteries supplying the kidneys aswell as the renal arteries.
May receive contributions from the SMA, suprarenal, testicular or ovarian arteries
How does the renal pelvis connect with the medulla of the kidney?
Renal pelvis lies in the hilum
Outer border of the renal pelvis divides into 2/3 major calycaes
Major calycaes divide into many minor calycaes
Minor calycaes are indented by a papilla of renal tissue called a renal pyramid
Where do collecting tubules empty urine?
Into the minor calycaes at the papilla
The ureter has 3 layers of smooth muscle, what are they?
Inner longitudinal layer
Middle circular layer
Outer longitudinal layer
State the anatomical position of the bladder
Retroperitoneal. When empty it lies on top of the pubic symphysis. When filled it enlarges into the abdominal cavity.
In females it is in front of the vagina, uterus and rectum. In males it is in front of the rectum
What is the blood supply to the bladder?
Superior and inferior vesicle branches of the internal iliac artery
What is meant by the base of the bladder?
The trigone. A triangular reddish smooth region bounded by the ureteric openings into the bladder and the internal urethral meatus
Describe the structure of the detrusor muscle in the neck of the bladder
Detrusor muscle runs circularly at the neck of the bladder to form the involuntary internal urethral sphincter
What is the anatomical position of the prostate?
Lies below the bladder in the male, lining the proximal urethra. It is connected to the bladder by connective tissue called stroma
How do the ureters run in respect to the iliac vessels?
Cross the bifurication of the common iliac arteries at the sacroiliac joints.
They run retroperitoneally over the posterior abdominal wall in front of the external iliac artery down to the pelvic brim.
How do the ureters run in respect to the uterine vessels, ovary/vas
Female = ureter runs under the uterine artery. Runs in close proximity to the posterior/superior aspect of the ovaries. Male = vas deferens cross the ureters anteriorly, superior to the seminal vesicles
What attaches at the apex of the bladder?
The urachus. A fibrous remnant of the fetal allantois, which is seen as medial umbilical ligament on anterior abdominal wall
