Lecture 33: The nephron Flashcards
What is the filtration barrier?
what is its function?
What are the three layers?
A barrier that allows free passage of small molecules and restricts passage of most proteins, RBCs are not filtered into nephron. - lies btw blood and Bowman’s space
Three layers
1. Fenestrated endothelium of glomerulus capillary
2. Fused basement membrane
3. Filtration slits between pedicles of podocytes
= Renal corpuscle is the location of the filtration barrier
What is the renal corpuscle ?
Renal corpuscle consists of a capillary bed called the glomerulus and the Bowman’s capsule
- glomerulus enclosed by Bowman’s capsule
- site of filtration
- glomerulus has afferent and efferent arterioles entering/leaving
What is the structure of the bowman’s capsule ?
Two layers
- Outer parietal layer of simple squamous cells
- Inner visceral layer of podocytes
Between the two layers is the bowman’s space
What are podocytes?
- surround glomerulus capillaries
- very branched, very specialised epithelium
- branches form intertwining foot processes called pedicles
- filtration slits form btw pedicles
- filtered blood goes through these slits and passes into Bowman’s space
What are the components of the nephron ?
- Bowman’s capsule
- Tubular system
= proximal convoluted tubule PCT, loop of henle and distal convoluted tubule - Collecting duct
What components make up the renal tubular system ?
What is their structure
Proximal convoluted tubule
= cuboidal epithelium, dense microvilli and many mitochondria
Loop of Henle
= descending and ascending limb which both have thick and thin parts
- simple squamous epithelium
Distal convoluted tubule
= cuboidal epithelium which is thinner , fewer microvilli and fewer mitochondria
- many DCT’s empty into one collecting duct - lined with simple cuboidal epithelium
What is the juxtaglomerular apparatus JGA ?
Where the afferent arteriole and DCT meet
- Afferent arteriole = JC cells = mechanoreceptors which sense BP
- DCT = Macula densa = chemoreceptors which sense NaCl concentrations
What do renal tubules do ?
- Selectively re-absorb what body needs
- actively secretes into during what body does not need anymore
What is each nephron comprised of:
What is each nephron associated with ?
Comprised of:
- bowman’s capsule, renal tubules and a collecting duct
Associated with:
- glomerulus
- pertibular capillaries
What is the structure and function of glomerular capillaries ?
- thin walled single layer of fenestrated endothelial cells
- fed and drained by arterioles
- high pressure and regulated
- specialised for filtration
What is the structure and function of peritubular capillaries ?
- adjacent to renal tubules
- arise form efferent arterioles draining into glomeruli
- low pressure and porous
- after filtration the blood is viscous and protein rich
- specialised for absorption
What is the vasa recta?
- Long straight vessels
- associated with the loop of Henle in Juxtamedullary nephrons
What are the two types of nephrons?
Cortical nephrons
- 85% and lie mainly in cortex
Juxtamedullary nephrons
- extend deep into the medulla
- important for the formation of concentrated urine
