Histology #7 (Urinary) Flashcards
Renal Corpsucle
Marks the begining of the Nephron
- Nephron = basic functional unit of the kidney
Encompasses Bownman’s Capsule and Glamerulus
Bowman’s Capsule
A hollow sphere formed by a simple layer of squamous epithelial parietal cells
Has two poles:
Vasulure pole = Afferent and Efferent arterioles
Urinary pole = Begning of proximal convulated tubule (PCT)
Image - see shell that bowmans capsule creates for glamerulus
Afferent vs. Efferent arterioles
Afferent arterioles - ushers unfiltered blood into the glamerulus
Efferent Arteriole - Usgers filtered blood out of the glamerulus
PCT = tube that ushers filterate (filtered water) out of the glamerous (out of the nephron)
Bowman’s Capsule Histology
Bowmans capsule - circular boarder of cells that provde a base for glamerous inside
Glomeruslus
A filtration appertatus composed of fenestrated capilaries + golmerular mesengial cells + Podocytes
Three compoents:
1. Fenstarted capilaries
2. Glamerular mesengial cells
3. Pdocytes
Glomeruslus Histology
Glomerous = looks lke interweaving capialeiries (looks like tarn ball)
Fenetratsed capilaries
Function - responsible for filtering blood + creating urine + reabsorbing nutrients
Lined with fenetrated endothelial cells
- Fenetsrated = pore within the endothelial cells that allows substances to go through
Fenetratsed capilaries Histology
EM - have siluete of capilaries
***stains are hard to find
Golmerular mesengial Cells
Function - Repsonsible for turning over the basal lamina (replaces old cells with new ones) + controlling capilary diameter + sereting vasoactive compound and cytokines
Mesengial cell types prodvides structural supprt to glomerular tuft (supports ball of capilaries)
Cells are dispersed between capilary branches
Golmerular mesengial Cells Histology
See nucleus of mesengial cells
Podocytes
Overall - Unique visceral epithelial cell type
Function:
1. Provides extensive processes that completey enclose glamerular capilaries
- Preform encapsulation giving sheath to capilaries
2. Creates barriers of filtration slits
3. Maintains gloerular basement membrane
Podocytes Histology
EM - see A is complete podocyte ; B shows processes that are extension form protocyte that allow capialries to be engulfed and protexted
Golmeular filter
Golmeular filter = how we keep unwanted things out of capilaries
Composed of 3 compoenets:
1. Fenestrated epithelieum
2. Thcik badsal lamina
3. Pedicles - filtration slits between podocytes procsses
Function - stop the passage fo proteins 68kDA or larger
- 68kDa (size of albumin)
Golmeular filter Histology
See podocyte + glemalar basement membrane + endothlial + foot processes of the podocyte
Proximal conculated Tubule (PCT)
Overall - first elements where the filtrate from the renal capsule is modified
Largest section of the nephorn tubule
- Provides more opperyunity to absorb ions and molescules from the lumen
Follows a twisting conveluted path (coils in the cortext)
- When PCT enters the medulla it becomes a proximal straight tubule (Proximal straight tubules is parallel to other elements in the medula)
Epithelial cells in PCT
Epithelial cells in PCT:
1. Large
2. Eosenphilic cytoplasm
3. Forms a simple cuboidal epithelium
Proximcal conveluted tubule (PCT) histology
Becomes convuled = have different orientations (Round vs. Oval vs. straiht structures)
PCT epithelial cells = large + can’t aways see nuclei (look like they ave fewer nuclei but they don’t)
- Have esoenophilc cytoplasm
PCT epithelial cells Histology
Pink is less densly packed
See microvilli around PCT
Featires for PCT reabsorptoion
Has features on the:
1. Apical surface
2. Basolaeteral surface
3. Cytoplasm
Features for PCT reabsportion (Apical surfcae)
Apical surface has microvilli (forms brush boarder)
Has Na+-dependt co-trasnprts to imporatnt specifci molecules from the lumen into epithelial cells
- Example - absorbs all glucose + Amino Acids + Na (65% of na)
Features for PCT reabsportion (basolateral surfcae)
Has basolateral invagination
Has Na-K pumps - maintains Na and K grdainets
- ALSO has absorptive role by pumoing Na from the lumen into the iterstitial to peritubular capialries
Has chanels for molecules absorbed from the PCT lumen to exit the cells
Features for PCT reabsportion (cytoplasm)
Cytoplasm of PCT ells = has densley packed mitocondria making ATP to support Na/K pumps
PCT histology
EM - shows PCT epithelial cells (see mitocodnria + microvilli + basostatsitons)
- Basostraitoons = because of basoinvaginations
Loops of henle (overview)
First - Entering medual is the Thin decdending limb - comes from the proximal convuluted tubule
THEN as it dips it makes a 180 degre turn at the bottom
THEN becomes a thin acending limb
THEN trasnitions into the tick ascending limhb
Exits the medula back into the cortext
Loops of henle Thin dedcening limb
Function:
1. Allows water to move out of the tubule into the interstitial space
- Conatin pasive trasnports down concetration gradient - aquaporins (water moves through aquporins)
3. Concetrates filtrate
Loops of henle Thin dedcening limb Histology
Thin dcesninding is lined with simple squamous epitheliam
No Apical brush boarder
Loops of henle Thin ascending limb
Function:
1. Reabsorb Na and Cl form filtrate into the interstitial fluid through Na and Cl transporters
- Conatains passive Na and Cl chanels
- Impermable to water = diluares diltrate as it is passing through
Loops of henle Thin ascending limb Histology
Lined with simple squamous epithelum
No apical brush boarder
Image - Thin ascending and decscedning
- Left - section of thin lined with simple squamous + can see lopp
- Right - shows the thin has simple sqamous epithelium
Loops of henle thick ascending limb
Function:
1. Activley transports Na, Cl, K into interstitial fluid
- Conatins active pumps
- Impermeable to water
- Further dilates filtarte because impermebale to water
Loops of henle thick ascending limb Histology
Lined with simple Cuboidal epitheliam
No Apical Brish boarder
Uniform luminal space (disctict luminal space)
Image -
Left - lined with cuboidal
Right - Has smaller diamter than collecting ducts + uniform luminal space
Distal convaluted tubules
Follow the thick ascending limb
Have a coiled path (similar to PCT) found mainly in the corext
- Less convoluted and shorter than PCT
Intial segment lies next to the corpsucle and forms the juxtagolmerular appuratus
Distal convaluted tubules Histology
Always occupy less space than PCT
- DCT epithelial cells are smaller than PCT epithelial cells
- Tall + simple cudoidal epitheluum
In any given sectio of kidney the corext - less space is distal convaluted tube compared to prximal tube
Distal convaluted tubules function
Overall function - fine tuning of Na reapsoption (<5%)
Apical surface - Na-dependent co-trasnporters and Na chanels (imports Na from lumen into epithelial cells)
Basolateral surface - Na/K pumps (transports Na from the fitrate (urine) in lumen into the interstitium)
Cytoplasm - densly packed mitocondria
Distal convaluted tubules Histology (EM)
Shows DCT epithelialc ells + shows apical microvilli + basoinvagination + packed eloggated mitcondira