Urinary Tract Flashcards
Divisions of kidney
Pale outer cortex
Darker inner medullary tissue
Thickness of healthy cortex
At least 7mm
Medullary pyramids- structure
10-15 whose apices point towards the hilum of the kidney
Each pyramid is surrounded on 3 sides by cortex
What does the renal cortex contain
All of the glomeruli of the kidney
Convoluted parts of the proximal and distal tubules
Proximal parts of collecting duct
Number of medullary pyramids in each kidney
10-15
What do the medullary pyramids contain
Straight portions of the proximal and distal tubules
Loops of Henle
Distal parts of collecting duct
Where does the filtrate from the medullary pyramids drag into
From up to 20 pores into a funnel-shaped calyx from where the urine is collected into the widened pelvic portion of the ureter for transport to the bladder
What enters and exits the kidney at the hilum
Renal artery
Renal vein
Branches of renal artery
Divides into 5 or 6 main branches that give off arcuate arteries at the corticomedullary junction
These then form the interlobular arteries
Where do the arcuate arteries form interlobular arteries
At the corticomedullary junction
Interlobular arteries
Penetrate the cortex at regular intervals dividing the cortex into lobules
Give off Afferent arterioles that supply the glomeruli
Which arteries give off the afferent arterioles of the glomeruli
Interlobular arteries
How does the filtered blood return to systemic circulation
Arcuate veins
Straight arterioles- vasa recta
Near the corticomedullary junction arcuate arteries give off straight arterioles that penetrate deep into the medulla (vasa recta) before returning blood to the arcuate veins
Structure of glomerulus
A parallel array of fenestrated capillaries ensheathed by podocytes
What forms the filtration barrier of the kidney
Basement membrane between endothelial cells of capillaries and podocytes of epithelium
Function of renal glomerulus
Blood enters the kidney where it is filtered
Primary filtrate then passed to the rest of the nephron for selective reabsorption of solutes
What lies between the coiled loops of glomerular tuft
Matrix-forming mesangial cells
What do the walls of the afferent arteriole contains
Specialised renin-producing cells
Macula densa location
Specialised palisade cells in the segment of distal tubule that sits alongside the glomerulus
Where does the glomerular tuft arise from
The vascular pole- the point of entry into the glomerulus of the afferent arteriole and point of exit of the efferent arteriole
The vascular pole
the point of entry into the glomerulus of the afferent arteriole and point of exit of the efferent arteriole
Structure of the glomerulus tuft
Capillary loops supported by podocytes
Surrounded by the Bowman’s capsule- separates it from the glomerular capsule
What lies in the angle between the afferent and efferent arterioles
The returning distal loop of the same nephron
Structure of filtration barrier
Fenestrated endothelial cells
Podocytes ‘stand off’ from the membrane by complex foot processes
Arrangement forms physical pores between the cells guarded only by the filtration membrane
Charged nature of filtration barrier
Restricts passage of some molecules
Water and solutes up to about 50000 daltons are able to pass into the urinary space and constitute the primary filtrate
What constitutes the primary filtrate
Water and solutes up to about 50000 daltons
Structure of proximal tubules
Most highly coiled segment although a straight distal portion projects in some cases into the medulla
Cells have a prominent brush border and complex invaginations of baso-lateral membrane
Function of proximal tubules
Extensive re-absorption of filtrate
Sodium is actively transported in with glucose/amino acids
Cells take up proteins and polypeptides by Endocytosis
Function of lysosomes in proximal tubule cells
Break down proteins and polypeptides before returning constituents to circulatiom
Which proteins pass into the filtrate before being reabsorbed
Almost any negatively charged small protein
Which proteins will not pass into the filtrate
Albumin and haemoglobin as are too large
Where is the loop of henle located
Medulla
Structure of loop of henle
A thick straight descending portion
A thin loop
A thick ascending portion
Thin loop of loop of henle
Vary in length
Ascending portion of thin limb of loop of henle function
Retains water
Chloride and sodium are reabsorbed
Produces a dilute (hypotonic) filtrate (urine) and a hypertonic interstitium
What runs alongside the loop of henle
Vasa recta - long straight capillaries
When are the thin loops longest
When glomeruli lie close to the cortico-medullary junction
Permeability of thin descending limb of loop of henle
Low permeability to ions and urea
High permeability to water
Permeability of thin ascending limb of loop of henle
Not permeable to water
Highly permeable to ions
Function of difference in permeability of 2 limbs of loop of henle
Creates a concentration gradient within renal medulla
Macula densa function
Monitor sodium levels and influence filtration process of glomeruli
Cells of distal tubule
Only a few short microvilli
No brush border
Deep invaginations of the basal plasma membrane with numerous mitochondria
Function of mitochondria in distal tubule cells
Control of acid/base balance and concentration of urea
Do proximal or distal tubule cells stain lighter
Distal
Influence of aldosterone on distal tubules
Sodium ion reabsorption
Potassium ion secretion
Bicarbonate ion reabsorption
Hydrogen ion section - urine acidoc
Within the cortex of the kidney, are proximal or distal tubules more numerous
Proximal tubule is normally longer and more tightly coiled so appears more numerous
Formation of collecting ducts
Collecting tubules from several nephrons coalesce to form larger ducts that pass into the medulla
Medullary rays
Visible streaks in the medulla formed by collecting ducts
Structure of thick ascending and descending limbs of loop of henle
Structurally similar to proximal and distal convoluted tubules respectively
Cells of collecting duct
Few organelles
Dark intercalated cells with high concentrations of mitochondria
What surrounds the collecting ducts
Hypertonic medium generated by the loop of henle
ADH function
Increases the permeability of the collecting ducts cells so water is reabsorbed into the hypertonic interstitium- concentrating the urine
What does the juxta-glomerular apparatus contain
Afferent and efferent arterioles
Macula densa
Lacis cells (specialised cells of the glomerular matrix)
Where is renin produced
Cells in the walls of the afferent arterioles- appears as granules in the cytoplasm
Function of renin
Catalyses conversion of angiotensinogen to angiotensin I
First step in stimulation of aldosterone release by the suprarenal glands
Role of lacis cells and mucula densa
Regulation of renin secretion through the monitoring of sodium ions in the distal tubule
Where is angiotensin II produced
Lungs
Which cells of the kidney are particularly responsive to aldosterone
Distal tubule and collecting ducts
Function of aldosterone
Promote reabsorption of sodium ions and water - concentrating urine
Where is angiotensinogen produced
Liver
What stimulates the release of aldosterone by glomerular cells in the cortex of the suprarenal gland
Angiotensin II
What is aldosterone secreted by
glomerular cells in the cortex of the suprarenal gland
Structure of urothelium
Between the surface layer of umbrella cells and basement membrane there are several apparent layers of cells- all of which are in contact with the basement membrane
Number of layers varies between 3 and 8 according to location and degree of distension
Stratified with 2 layers but appears pseudostratified
Shape of basal cells in urothelium
Cuboidal
Shape of cells above basal cells in urothelium
Columnar in the relaxed state
Umbrella cells
Large bi-nucleate cells
Surface composed of thick membrane plates joined by thinner membrane bands
Composition of thick membrane plates of umbrella cells
Unique lipid composition
Rich in cerebrosides
Number of layers of cells between umbrella cells and basement membrane
3-8 depending on location and degree of distension
Location of membrane plates in relaxed state
Perpendicular to the membrane surface - giving it a fuzzy appearance
Location of membrane plates when stretched
Drawn out onto the surface of the cell
Umbrella cells function
specially adapted to resist attack by the urine in the lumen
Number of layers of cells in urothelium when bladder is empty
4-6 ish due to the squashing up of cells when the bladder is emoty
Number of layers of cells in urothelium when bladder is full
Epithelium is stretched so apparent number of layers of cells decreases
When most full- appears as a single layer of cells covered by the urine-proof umbrella cells
Function of ureter
Conducts urine from pelvis of the kidney to the urinary bladder
Length of ureter
20cm
Structure of ureter
Star shaped lumen
Epithelial tube surrounded by 2 helical layers of smooth muscle
Towards the bladder the muscle fibres become predominantly longitudinal in orientation
Where is the ureter constricted
Origin in pelvis of kidney
As it passes into the true pelvis anterior to the sacro-iliac joint
As it enters the postero-inferior surface of the bakdder
Where does the ureter enter the bladder
Postero-inferior surface
Where does the ureter pass into the pelvis
Anterior to the sacro-iliac joint
Where are kidney stones likely to become lodged
3 points of constriction of ureter
Number of points of constriction of ureter
3
What prevents reflux of urine
Compression of the ureter as it passes obliquely through the muscular wall of the bladder
Shape of ureter lumen
Star shaped
What lines the lumen of the ureter
Urethelium
What surrounds the urethelium of the ureter
2 helical layers of smooth muscle
In which layer of the ureter do thin-walled venules lie
Lamina propria underneath urothelium of the ureter
Structure of urinary bladder
Thick bundles of smooth muscle with no preferred direction except at the neck where 3 distinct layers are evident
Innermost longitudinal layer of smooth muscle in neck of bladder
Projects inferiorly and turns transversely to form a sphincter around the prostatic urethra (males) and the external meatus (females)
Cell structure of urinary bladder
Lining urothelium sits in a fibrous Lamina propria
Thrown into folds
Prostatic urethra
Males
External meatus
Females
Nerve supply to the bladder
Autonomic
Sensory nerve supply of bladder
Provide information about degree of distention
Motor nerve supply of bladder
Contraction of muscle during micturition
Parasympathetic nerve supply to bladder
Sacral outflow
What nerves supply blood vessels to the bladder
Sympathetic
Is the urethra longer in males or females
Males
Divisions of urethra in males
Prostatic
Membranous
Bulbous
Pendulous
Lining of urethra in males
Urothelium mainly except at the distal (penile) end
Mucous glands found along whole length
Lining of urethra in females
Stratified squamous epithelium punctuated by areas of mucous glands
What surrounds the membranous part of the urethra
A striated muscle sphincter derived from the muscles of the pelvic diaphragm
What kind of tissue lies underneath the prostatic urothelium
Dense fibrous connective tissue which will restrict the distension of urothelium
How is blood flow through the glomerulus regulated
Constriction of the afferent and efferent arterioles
Why is the wall of the ureter composed mainly of smooth muscle rather than fibrous connective tissue
Undergoes peristaltic contractions that help to conduct urine to the bladder
Which nerves cause micturition
Occurs once the external sphincter of the bladder is relaxed= sympathetic stimulation
And the muscle wall of the bladder (detrusor muscle) contracts = parasympathetic
Name of muscle wall of bladder
Detrusor muscle
Which glands drain into the prostatic urethra
Prostate
Seminal vesicles
Deferent duct (sperm)
Which glands drain into the penile urethra
Bulbo-urethral glands
Other small mucous glands
What type of epithelium lines the distal end of both the male and female urethra
Stratified squamous epithelium
Components of urinary tracts
Kidneys
Ureters
Bladder
Urethra
Number of nephrons in each kidney
Roughly 1 million
3 areas of kidney
Cortex
Medulla
Renal pelvis
What encases the glomerulus
Bowman capsule
What lines the glomerulus
Podocytes
What supports the glomerulus
Mesangial cells
What is commonly used to stain the glomerulus
PAS
Function of mesangial cells
Provide structural support for capillary by producing extra-cellular matrix protein
Contraction of smooth muscle tightens capillaries and reduces glomerular filtration rate
Phagocytosis of glomerular basement membrane break down products
How much albumin in urine is abnormal
More than 3g per day
Loss of which proteins in the basement membrane are associated with kidney disease
Nephrin
CD2AP
2 components of juxtaglomerular apparatus
Glomerulus
Distal convoluted tubule
What lines the proximal convoluted tubule
Cuboidal epithelium
Round central/basal nucleus
Brush border of microvilli at apical end
Many mitochondria so appear eosinophilic
Lining of thin part of loop of henle
Simple squamous
Lining of thick part of loop of henle
Low cuboidal
Lining of distal convoluted tubule
Low cuboidal epithelium
Lining of collecting duct
Cuboidal epithelium
Principal cells of collecting duct
Respond to aldosterone and ADH
Intercalated cells of collecting duct
Exchange H+ for HCO3-
How does ADH increase permeability of collecting duct
Insertion of aquaporin 2 into apical membrane of principal cells
Alpha intercalated cells
Secrete acid
Beta intercalated cells
Secrete bicarbonate
Kidney blood supply
Abdominal aorta
Renal artery L1
Anterior and posterior division
Interlobar artery
Arcuate artery
Interlobular artery
Afferent arteriole
At what level does the renal artery leave the abdominal aorta
L1
Divisions of renal artery
Anterior and posterior division
What do anterior and posterior divisions of the renal artery divide into
Interlobar arteries
What do Interlobar arteries give rise to
Arcuate arteries
What do the efferent arterioles give rise to
Peritubular capillaries
What do peritubular capillaries give rise to
Vasa recta
Lining of renal pelvis
Urothelium
Arrangement of smooth muscle in ureter
Inner longitudinal
Outer circular
Layers of bladder
Urothelium
Lamina propria
Muscularis mucosae
Submucosa
Muscularis propria
Subserosa and serosa
Length of female urethra
4-5cm
Which glands open into female urethra
Paraurethral
Periurethral
Length of male urethra
20cm
What has a lining of urothelium
Renal pelvis
Ureter
Bladder
Urethra
Basement membrane of glomerulus
Double thickness- lamina lucida interna
Lamina densa
Lamina lucida externa
Contains collagen and negatively charged heparin sulfate molecules
Bartholin’s glands
glands are located on each side of the vaginal opening. These glands secrete fluid that helps lubricate the vagina
