2 - Urinay System Histology Flashcards
What are the components of the kidney?
- Hilum
- Renal Sinus
- Capsule
- Cortex
- Medulla
- Minor Calyx
- Major Calyx
- Kidney Lobe
- Kidney Lobule
- Uriniferous Tubule
- Juxtaglomerular (JG) Apparatus
- Renal Interstitium
- Blood Supply
Describe the hilum of the kidney
- depression in the kidney’s concave surface
- Opens into the renal sinus
- Is the site where vessels and nerves pass into or leave the kidney
- Where ureter exits kidney
What is the renal pelvis?
Renal pelvis - is the funnel-shaped, expanded, proximal end of the ureter
Describe the renal sinus
Is a fat-filled cavity enclosing the following:
- Branches of the renal artery and vein, lymph vessels
Ureter and nerve fibers
Describe the capsule of the kidney
Two layers:
- Its outer layer has collagen and fibroblasts
- Its inner layer has collagen and myofibroblasts
Describe the cortex of the kidney
- Is the outer region of the kidney
- The cortical tissue overlying the base of a pyramid is the cortical arch
- The cortex consists of alternating regions, the cortical labyrinth and medullary rays
Describe the cortical labyrinth of the cortex of the kidney
Consists of the regions between the medullary rays. It contains the following structures:
- Renal corpuscles
- Convoluted tubules
- Connecting tubules
Describe the meduallary rays of the cortex of the kidney
They consist of medullary tissue that extends from the base of the pyramids into the
cortex. Each medullary ray consists of:
- Straight tubules
- Collecting ducts
Describe the blood flow in the cortex of the kidney
90 - 95% of blood flowing through the kidney is in the cortex where it will be filtered through the glomeruli
Describe the medulla of the kidney
Is the inner region of the kidney. Contains the following:
- Renal pyramids (apex and base)
- Renal columns (of Bertin)
Describe the renal pyramids of the medulla
There are 8 - 18 per kidney
Apex
- AKA “renal paiplla” has an area cribrosa which consists of 20 openings of papillary ducts (of Bellini)
- The apex projects and drains/empties into a minor calyx
Base
- Found at the corticomedullary border
Describe the renal columns (of Bertin) of the medulla
- Consisting of cortical tissue
- Project between the medullary pyramids
- THEY RESIDE WITHIN AND ARE PART OF THE MEDULLA ***
Renal columns include the following:
- straight tubules (of the nephrons)
- collecting ducts
What are the vascular components of the medulla?
- Vasa recta (straight vessels)
- 5 - 10% of blood flowing through the kidney is in the medulla
Describe the minor calyx of the kidney
- Cup-like, funnel-shaped
- Receives apex of one pyramid
Describe the major calyx of the kidney
- Several minor calyces converge and open (and drain) into a major calyx
Describe the kidney lobe components
- A renal pyramid (the number of lobes = the number of pyramids)
- Associated cortical tissue at the base of the pyramid
- Associated cortical columns (of Bertin) (one half of each adjacent renal column)
- The human kidney is multilobar (has multiple lobes)
Describe the kidney lobule
consists of a central medullary ray and surrounding cortical tissue
- A collecting ducts
- All nephrons that empty into the collecting duct
What does the uriniferous tubule consist of?
Nephron + Collecting Duct
Describe the uniferous tubule
- It consists of epithelium and is covered by a basal lamina on its exterior
- Contains both the nephron and collecting duct
What is the structural and functional unit of the kidney?
NEPHRON ***
What are the components of the nephron?
- Renal Corpuscle
- Proximal tubule
- Thin limbs of Henle
- Distal dubule
What are the components of the first part of the nephron, the renal corpuscle?
- Glomerulus
- Bowman’s Capsule
- Bowman’s space (urinary space)
- Vascular Pole
- Urinary Pole
- Filtration Barrier
Describe the glomerulus of the renal corpuscle
- is a cluster of fenestrated capillaries
- is an arterio-capillary bed
- glomerular ultrafiltrate oozes out of glomerulus by passing through the filtration barrier
Describe Bowman’s capsule of the renal corpuscle
Bowman’s capsule
- is the proximal end of the nephron
- visceral layer of Bowman’s capsule (cover glomerulus with a cluster of capillaries and is composed of podocytes)
- ** Filtration slits are present here and have a slit diaphragm (nephrin) ***
- parietal layer of Bowman’s capsule (simple squamous epithelium that is covered by a basal lamina)
Describe Bowman’s space of the renal corpuscle
- is the space between the visceral and parietal layers of Bowman’s capsule
- contains ultrafiltrate
Describe the vascular poles of the renal corpuscle
Vascular poles is the site where…
- Afferent glomerular arterioles enter the renal corpuscle (mesangial cells)
- Efferent glomerular arteriol leaves the renal corpuscle (greater resistance to blood flow)
Describe the urinary poles of the renal corpuscle
Contains the initial part of the proximal convoluted tubule (PCT)
Describe the filtration barrier of the renal corpuscle
From inside outward, it consists of:
- endothelial surface layer of glomerular capillarie (glycocalyx glycoproteins)
- fenestrated endothelium of glomerular capillary (NO diaphragms over fenistrations)
- basal lamina (produced by endothelium and podocytes)
- subpodocyte space
- visceral layer of Bowman’s capsule (podocytes)
The filtration barrier ahs 2 discontinuous layer of all the components listed above
What is the next part of the nephron we will cover?
Proximal tubule
What are the parts of the proximal tubule?
- Proximal convoluted tubule (PCT)
- Proximal straight tubule
Describe the proximal convoluted tubule of the proximal tubule
- simple cuboidal epithelium
- striking eosinophilic, granular cytoplasm
- microvilli (“striated border”)
- basement membrane (PAS+)
Describe the proximal straight tubule of the proximal tubule
Proximal Straight Tubule (THICK Descending Limb of the Loop of Henle) – similar structure as PCT
What is the next part of the nephron we will discuss?
Thin limbs of Henle’s loop
What are the components of the thin limbs of Henle’s loop?
- Thin Descending Limb
- Henle’s Loop
- Thin Ascending Limb
Note that the entire loop is lined with simple squamous epithelium
Describe the thin descending limb
Makes a hairpin turn
Describe Henle’s loop
Is the entire U-shaped portion of a nephron
Describe the thin ascending limb
The segment after hairpin turn
What is the last part of the nephron?
Distal tubule
What are the components of the distal tubule?
- Distal Straight Tubule = (THICK Ascending Limb of the Loop of Henle)
- Macula Densa
- Distal Convoluted Tubule (DCT)
Describe the distal straight tubule of the distal tubule
Remember this is the THICK ascending limb of the loop of Henle
- low cuboidal epithelium with few microvilli
- more mitochondria than cells of PCT
Describe the macula densa of the distal tubule
Macula = spot, Densa = dense
- modified segment of the distal tubule located next to the afferent arteriole
- Between afferent and efferent arterioles
Describe the distal convoluted tubule of the distal tubule
- much shorter and less tortuous than the PCT
- wide, clear lumen
- pale, granular cytoplasm
- smaller cells, more cells per c/s profile
Where does the nephron end?
In the cortical collecting duct
Describe the cortical collecting duct
- Is part of the uriniferous tubule, but not part of the nephron
- The DCT empties into a connecting tubule or an arched connecting tubule that drains into a cortical collecting duct or a medullary collecting duct
What do we see after the cortical collecting duct?
Papillary ducts of Bellini
Describe the Papillary Ducts (of Bellini)
- Are the continuation of the medullary collecting ducts
- Open in the area cribrosa
- Are lined with tall columnar epithelium
What do we see after the papillary ducts?
Juxtaglomerular (JG) apparatus
Describe the juxtaglomerular (JG) apparatus
- Consists of the macula densa, the JG cells and the extraglomerular mesangial cells
- It controls blood pressure by activating the renin-angiotensin-aldosterone system
What are the components of the juxtaglomerular (JG) apparatus?
- Macula Densa of the DT
- JG cells of the afferent glomerular arteriole
- Extraglomerular Mesangial Cells
Describe the JG cells of the juxtaglomerular (JG) apparatus
JG cells of the afferent glomerular arteriole
- are modified smooth muscle cells in the tunica media of the afferent glomerular arteriole
- contain renin (a proteolytic enzyme)
Describe the extraglomerular mesangial cells of the juxtaglomerular apparatus
Reside in the interval bordered by the…
- Afferent arteriole
- Macula densa
- Efferent arteriole
- Vascular pole of the renal corpuscle
Describe the renal interstitium
- Contains a small amount of connective tissue
- Fibroblasts, Macrophages
Describe the blood supply to the kidney
Renal artery → anterior and posterior division → segmental arteries → lobar arteries → interlobar arteries → arcuate arteries → interlobular arteries → afferent glomerular arterioles ***
Know the last one (BOLD)
Describe the basic excretory passage of the urinary system
The minor calyces, major calyces, ureter, urinary bladder and proximal segment of the urethra are lined by transitional epithelium (urothelium). The free surface of this epithelium facing the lumen, is coated by rigid urothelial plaques with hinge regions between them. The urothelial plaques consist of uroplakins, transmembrane proteins that in combination with tight junctions create an impermeable barrier on the surface of the urothelium, preventing water, urea and protons present in the lumen from permeating the epithelium. Hinge regions have non-plaque proteins.
Describe the minor calyx
- Funnel-shaped
- Receives urine from the renal papilla of a single renal pyramid (Renal papilla is covered by transitional epithelium)
- Lined by transitional epithelium
- Lamina propria
- Smooth muscle layer
Know transitional epithelium***
Describe the major calyces
- May receive urine from up to 4 minor calyces
- Structure is similar to minor calyces
Describe the pelvis of the kidney (renal pelvis)
- Funnel-shaped, upper expanded portion of ureter
- Structure is similar to minor and major calyces
What are the components of the ureter?
- Mucosa
- Muscularis
- Fibrous CT covering
Describe the mucosa of the ureter
- The mucosa is thrown into folds when ureter is empty
- Transitional epithelial lining
- Basal lamina
- Lamina propria (contains dense irregular fibroelastic CT)
Describe the muscularis of the ureter
UPPER 2/3 of the ureter
- Outer circular layer
- Inner longitudinal layer
LOWER 1/3 of the ureter
- Outer longitudinal layer (extra layer) **
- Middle circular layer
- Inner longitudinal layer
How do the ureters deliver urine to the urinary bladder?
Ureters deliver urine to the urinary bladder via peristaltic waves
What are the components of the urinary bladder?
- Mucosa
- Muscularis
- Adventitia
- Serosa
Describe the mucosa of the urinary bladder
- Mucosa is is thrown into folds when bladder is empty
- Epithelium (Transitional epithelium)
- Lamina Propria has two parts (superficial and deep)
- Superficial lamina propria contains dense irregular collagenous CT
- Deeper lamina propria contains loose layer of CT (collagen and elastic fibers)
Describe the muscularis of the urinary bladder
- 3 layers of smooth muscle
- middle layer forms the internal sphincter muscle
Describe the adventitia of the urinary bladder
- Dense irregular collagenous CT
- Elastic fibers
- Attaches bladder to surrounding structures
Describe the serosa of the urinary bladder
Serosa (peritoneum) covers part of the bladder
Describe the female urethra
Layers
- Mucosa
- Muscularis
- External urethral sphincter
Describe the mucosa of the female urethra
Epithelium
- lined by transitional epithelium near bladder
- stratified squamous nonkeratinized lines remaining urethra
Lamina Propria
- fibroelastic
- glands of Littre (mucous)
Describe the muscularis of the female urethra
Muscularis
- inner longitudinal layer
- outer circular layer
Describe the external urethral sphincter of the female urethra
Skeletal muscle – where the urethra penetrates the UG diaphragm
Describe the components of the male urethra
- Prostatic Urethra
- Membranous Urethra
- Spongy Urethra (penile urethra)
- Lamina Propria
Describe the prostatic urethra
Lies within the prostate, transitional epithelium
Describe the membranous urethra
Traverses the UG diaphragm
- lined by stratified columnar epithelium
- pseudostratified columnar epithelium in some areas
Describe the Spongy Urethra (penile urethra)
In the spongiosum
- pseudostratified columnar epithelium
- stratified squamous non-keratinized epithelium in the distal end
Describe the lamina propria
Loose fibroelastic CT, very vascular, glands of Littre (mucous)
Describe the prostate gland
Is the largest accessory gland, is chestnut-shaped
What is the prostate capsule made out of?
Dense irregular collagenous CT (highly vascular), smooth muscle cells
What is the “framework” of the prostate gland?
STROMA ***
- Arises from the capsule, same composition as the capsule
What are the layers of the tubuloalveolar glands within the prostate?
Arranged into 3 layers of…
- Mucosal layer (inner layer, has small glands)
- Submucosal layer (intermediate layer, has larger glands)
- Peripheral layer (has the main prostatic glands, the largest glands)
Prostatic concretions (corpora amylacea) are calcified glycoproteins
What type of epithelium do we see in the prostate gland?
Simple to pseudostratified columnar epithelium – synthesizes proteins
