1 - Renal Histology Flashcards
4 functions of the kidney?
- Filters blood and removes waste as urine
- Produces hormones and enzymes (vit d, erythropoietin, renin)
- Regulates body water, salt and acid-base balance and so regulated BP
- Homeostatic regulation
Ureter vs urethra
Ureter exits kidney urethra exits body
The kidney is made up of lots of …. called nephrons
Filtering tubules
What is the centre of the kidney called and what does it contain?
Sinus/ cavity that is full of fat (even in cachexic people)
Where does the urine go once it exits the kidney
Ureter > bladder > urethra
What are nephrons
- the functional unit of the kidney
- there are approx 1 million per kidney
- they are a blood filter (renal corpuscle/glomerulus/capillary tuft enveloped by the tubule) and proximal, thin and distal tubules which then drain to the collecting ducts
What is the order of the structures in a nephron?
Renal corpuscle (containing glomerulus) Proximal convoluted tubule Proximal straight tubule Thin descending limb Thing ascending limb Thick ascending limb Distal convoluted tubule Collecting tubule Collecting duct
What makes up most the cortex?
The proximal convoluted tubules
What makes up the loop of henle?
Proximal straight tubule
Thin descending loop
Thin ascending loop
Thick ascending loop
Where does the filtration occur
Renal corpuscle
- salts proteins etc filtered out. The glomerulus doesn’t discriminate well - most needs to be reabsorbed
Where does bulk reabsorption occur
Proximal tubules (convoluted and straight)
- 65% of filtrate is reabsorbed in the proximal convoluted/straight tubules
- all of the glucose and salt, aa’s and water (bulk reabsorption of filtrate - secretion also occurs)
What occurs in the thin limbs and thick ascending limb?
Water extraction - IF required to make the urine more conc and retain water.
Distal convoluted, connecting tubule?
Fine tuning of salt levels, pH and water
Collecting ducts?
Water reabsorption
Renal corpuscle?
Contains a capillary tuft/glomerulus. Is surrounded by epithelial cells - podocytes which sit on the endothelial cells of the capillaries and parietal epithelial cells line the capsule
What is the vascular pole?
Where the afferent arteriole enters while the urinary pole is where the proximal convoluted tubule exits the renal corpuscle
Where does the filtrate go?
Urinary space
Where are podocytes and parietal epithelial cells continuous?
The VASCULAR pole
Describe the embryonic development of the renal corpuscle
The developing glomerulus invaginates into the tubule lining cells of the primitive renal tubule - the layer touching the glomerulus/endo cells will become the podocytes (visceral layer) while the outer layer is the parietal layer of the renal corpuscle
What dies the glomerular filtration barrier consist of?
3 major components
- Fenestrated endothelium of glomerular capillary
- Glomerular basement membrane
- Podocytes
- is a physical barrier, charge-selective barrier (negative charges such as albumin are repelled)
- restricts cells and large proteins
Glomerular Capillary Endothelium
- fenestrated; permeable to small molecules but restricts cells
- has a negative glycocalyx coat that is also IN the fenestrations
Glomerular BM
- thick
- the glomerular basement membrane is made up of collagen and negatively charged proteoglycans
- has a dense core and 2 less dense outer layers
- dense inner layer acts as a physical barrier (meshwork of fibres acts like a sieve)
- less dense layers act as a charge barrier as are negative and repel
Podocytes
The podocytes adhere to the GBM of the capillaries. Primary processes give off secondary processes that interdigitate that form slits and are linked by a protein bridge called a slit diaphragm (the slits form a physical filter). The podocytes are also covered in a glycocalyx coat.
Describe the slit membrane
Protein complexes that link adjacent secondary processes (covered in a glycocalyx)
