Urinary System Flashcards
Functions of the kidney and urinary tract
- Maintain water and electrolyte homeostasis, body fluid osmolarity and acid-base balance
- Excrete toxic metabolic waste products (mainly urea and creatinine)
- Act as an endocrine gland, producing renin and erythropoietin
What functions do the urinary tract accomplish and how does it do this ?
- Maintain water and electrolyte homeostasis, body fluid osmolarity and acid-base balance
- Excrete toxic metabolic waste products (mainly urea and creatinine)
Does this by the production, storage and voiding of urine
Kidney gross structure - shape and location
Kidney bean shaped in upper retroperitoneal area
Kidney gross structure- hilum
Entry of renal artery and exit of renal vein and ureter
Name structures going towards kidney from ureter
Renal pelvis, major calyces and minor calyces
What are main two areas of kidney called
Cortex and medulla
Medulla is divided into what
Medullary pyramids
Each medullary pyramid and it’s associated cortical tissue is considered what?
A lobe of the kidney
What is the kidney covered by?
Fibrous capsule
What are medullary rays?
Collection of collecting ducts and straight segments of the proximal and distal convoluted tubules
Where in the kidney are the medullary rays found?
The cortex
What is the nephron?
The basic functional unit of the kidney
What is the nephron composed off?
The renal corpuscle and renal tubules
What is the principal role of the renal corpuscle?
Production and collection of glomerular filtrate
What is the renal corpuscle composed off?
Glomerulus and Bowman’s capsule
What is the glomerulus
Tuft of capillaries
What is the Bowman’s capsule
Cup of simple squamous epithelium at the blind end of the nephron which the capillaries invaginate into
What supplies the tuft of capillaries?
Afferent arterioles
What drains the tuft of capillaries?
The efferent arterioles
How many cell layers separate the blood from the glomerular filtrate and what are their names
Two
Capillary endothelium and specialised epithelium (lies ontop of glomerular capillaries)
- these epithelia cells are called podocytes
What is a special feature of the endothelium?
It is fenestrated with pores
What is a special feature of the podocytes?
Have interdigitating cell processes forming filtration slits
What cells are scattered in the renal corpuscle that produce a connective tissue core and what is this core called?
Mesangial cells
Mesangium
What are the functions of mesangial cells?
Support and removal of debris
There are two poles in the renal corpuscle what are these two poles called?
Vascular pole and urinary pole
Podocytes are said to have what appearance ?
Lightly coloured and their cell processes produce a saw tooth appearance
The glomerular filter has 3 components
Fenestrated endothelium of capillary wall
Thick basement membrane
Filtration slits between pedicels
What is the role of the proximal convoluted tubule?
Reabsorption of water, proteins, amino acids, carbohydrates and glucose
What percentage of sodium and water is reabsorbed by the PCT
70%
What else is reabsorbed by the PCT?
Almost all glucose and amino acids
Principle Role of Loop of Henle
Creation of hypertonic environment in medulla
What is the Vasa recta?
Loops of thin walled blood vessels that dip down into the medulla from above and then climb back up the cortex
Structures in the outer medulla
Collecting ducts
Blood vessels of vasa recta
Thin loop of Henle
Proximal and Distal staight tubules
Principle Role of the DCT
Acid-base and water balance
Absorption of water, Na and bicarbonate, excretion of K and H ions
Which is smaller DCT or PCT
DCT
Which has a clearer lumen PCT or DCT
DCT - only have sparse microvilli unlike PCT
What does the hormone aldosterone do?
Controls the reabsorption of Na+ in the DCT
What secretes aldosterone?
Adrenal cortex
What controls the secretion of Aldosterone ?
Renin-angiotensin system
A greater Na+ and water retention causes….
Increase in blood pressure
Role of collecting ducts
Controlled reabsorption of water under the control of ADH
What hormone increase the permeability of collecting ducts to water and where is it secreted from?
Anti-diuretic hormone ( vasopressin) from posterior pituitary
What type of urine results in the presence of ADH
Concentrated
ADH = high permeability in medulla, because of the high salt content in the surrounding tissue, water passes out of the lumen
What is the Juxtaglomerular apparatus?
Specialized region formed at the site where the distal convoluted tubule passes adjacent to the vascular pole of the same renal corpuscle that forms part of its own nephron
The Juxtaglomerular apparatus is made up of three compartments …they are ?
The macula densa
The Juxtaglomerular cells
The extraglomerular mesangial cells (lacis cells)
Info on macula densa
On side of DCT nearest the afferent arteriole the cells of the DCT are taller, crowded together and the nuclei are intensely stained.
Believe to have a function in sensing sodium content of fluid in the DCT
Info on Juxtaglomerular cells
Modified smooth muscle cells in the wall of afferent arterioles. These cells contain/excrete renin, initiating the renin-angiotensin system.
Info on extraglomerular cells (lacis cells )
Modified mesangial cells extending outside the renal corpuscle. They contact macula densa and are continuous with mesangial cells inside renal corpuscle.
Direction of urine flow from renal papila (where it is produced)
Collected in minor caylx, flows into major caylx, ureter and then into bladder .
During voiding it flows into the urethra and exits the body
What are the conducting parts of the urinary tract lined with?
Transitional epithelium or urothelium - stratified
Cells at lumen of urinary tract are called ?
Umbrella cells -domed
Two reasons for specialised epithelium of urine tract
- Variability in thickness of cells represents different states of distension
- Special surface structures are to provide a highly impermeable barrier
Lumen of the ureter has how many layers of smooth muscle
2 - an inner longitudinal layer and an outer circular layer
Near bladder how many layers of smooth muscle?
3 - another outer layer of longitudinal muscle is present
What do the smooth muscle layers in the bladder form?
The detrusor muscle
What is the detrusor muscle responsible for?
Micturition
In females what does the epithelium. Of the urethra change from ?
Transitional epithelium to stratified squamous near the surface of body
