What are the four parts of the urinary tract?
What are the three main parts of the kidney?
What do we primarily find in the renal cortex?
Glomeruli, proximal convoluted tubules and distal convoluted tubules
What is a medullary ray? Where is it found?
- A collection of loops of Henle and collecting ducts
- Specialised area within the renal cortex
What does the renal medulla comprise?
Loops of Henle and collecting ducts of nephrons both close to and far away from the capsular surface of the kidney
What are nephrons? Where does the nephron start? What is the glomerulus lined by? What is the glomerulus encased by?
- Each kidney made up of ~million filtering units called nephrons, each includes a glomerulus (filter) and a tubule
- Nephrons start at glomerulus (a tuft of fenestrated capillaries)
- Glomerulus lined by podocytes
- Glomerulus encased by Bowman's capsule
- White space on diagram is where filtrate forms from glomerulus
What are the two main cell types within the glomerulus?
- Capillary endothelial cells
- Mesangial cells
- PAS allow us see basement membrane here
What do mesangial cells comprise? What is their function?
- Mesangial cells comprise smooth muscle
- Provide structural support for capillary in its production of extracellular matrix protein. Contraction of this smooth muscle reduces glomerular filtration rate
The glomerular basement membrane comprises three layers. What are these? What is the basement membrane lined by on its inner surface?
- Glomerular capillary wall
- Basement membrane
- Foot processes of podocyte
- Capillary basement membrane lined on its inner surface by vascular endothelial cells that are fenestrated, these are bridged by fibrils that prevent passage of large molecules, e.g. albumin
What does an epithelial basement membrane contain? How about a glomerular basement membrane?
- Epithelial basement membrane = lamina lucida + lamina rarer
- Glomerular basement membrane = lamina lucida interna, double thickness lamina densa + lamina lucida external (two basement membranes back to back). Also contains collagen + negatively charged heparin sulphate molecules
Magnified image of the glomerular basement membrane.
What is the juxtaglomerular apparatus? What are its two components?
- Next to glomerulus
- 2 components: one from afferent arteriole and one from distal convoluted tubule
What is the role of the juxtaglomerular apparatus? What are the three types of cells in the juxtaglomerular apparatus?
- Juxtaglomerular apparatus emulates function of each nephron, it is next to the glomerulus
- Macula densa
- Juxtaglomerular cells (secrete renin)
- Lacis cells
Where can we find the proximal convoluted tubule? What is it lined by? What is its role?
- Renal cortex
- Lined by simple cuboidal epithelium
- Reabsorption of solutes
Next is the loop of Henle. What does this do? What are its two parts? What is it lined by?
- Concentration of urine
- Dsecending and ascending limbs
- Thin segment lined by simple squamous epithelium
- Thick segment lined by low cuboidal epithelium
Next is the distal convoluted tubule. What is its function? What is it lined by?
- Reabsorption of more water and solutes
- Lined by low cuboidal epithelium
From the distal convoluted tubules, urine drains into the collecting ducts. What is their function? What are they lined by? What are the two types of epithelial cell that it contains?
- Water reabsorption and controlling acid-base and ion balance
- Cuboidal epithelium
- Principal cells and intercalated cells
What is the blood supply to the kidney?
Diagram of blood supply to kidney.
What is the renal corpuscle?
Whole unit of glomerulus and Bowman's capsule
Once blood has left the glomerulus, where does it pass to?
- Passes to efferent arteriole, which then gives rise to peritubular capillaries
- As it descends into medulla, gives rise to vasa recta --> renal veins --> back into inferior vena cava
The collecting ducts in the medulla drain into the renal pelvis. What is the renal pelvis? What is it lined by?
- Transmits filtrate from nephron to ureter
- Lined by urothelium
What is urothelium?
Another diagram of urothelium.
The only cells we can be confident are not in contact with the basement membrane are the umbrella cells
What are ureters? What are they lined by?
- Muscular tubes that convey urine via peristalsis from the kidney to the bladder
- Lined by the same urothelium as is found in the renal pelvis
What is the bladder formed by?
Bladder drains through the urethra
What is the urethra like in females?
What is the urethra like in males?
Divided into three parts