EXAM III Renal Histology Flashcards
What are the two components of the urinary system?
Two kidneys and ureters
Urinary bladder and urethra
What components are within a nephron?
Renal corpuscle = Bowman’s capsule
Renal tubule = continuation of Bowman’s capsule
What are the two types of nephrons? What are their characteristics?
Cortical Nephrons (cortex region) - have short LOHs w/ no capillaries
Glomeruli empty into peritubular capillary networks that surround PCT and DCT
Juxtramedullary Nephrons (deeper in cortex)
Glomeruli empty into vasa recta near LOHs and collecting ducts, long LOHs in deep medulla
List the vascular supply to the kidneys
Interlobar A.
Arcuate A.
Interlobular A.
Afferent A.
Glomeruli
Efferent A.
Interlobular vein
Arcuate vein
Interlobar vein
Renal vein
What two locations can the efferent arterioles feed into?
Vasa recta of juxtamedullary nephrons (capillary loop)
Peritubular capillaries of cortical nephrons (capillary network)
What makes up the renal corpuscle? What is its function?
Glomerulus
Bowman’s capsule
Involved in producing a filtrate for blood
The remainder of the nephron functions as to modify the filtrate
What are the 3 processes that are involved in forming urine?
Filtration (renal corpuscle)
Reabsorption (renal tubule)
Secretion (renal tubule)
What are the components of the glomerulus? What type of cells are involved in the afferent arteriole? What do they secrete?
Afferent Arteriole
Juxtaglomerular cells - secrete renin, circular smooth muscle cells at vascular pole
Glomerular capillaries
Efferent Arteriole
Mesangium - mesangial cells
What is the Bowman’s capsule made up of? What type of cells are in the layers?
Double-layered, cup-shaped dilation of the nephron
Parietal layer - outer layer = simple squamous, continuous w/ simple cuboidal epi. of PCT
Visceral layer - inner layer = podocytes in contact w endothelium of glomerular capillaries (the actual filtration layer)
Bowman’s Space - b/w the parietal & visceral layers; continuous w/ lumen of PCT
What are the 2 types of mesangial cells?
Intraglomerular mesangial cells
b/w nearby capillaries in golmerulus and cover endothelium not covered by podocytes
Extraglomerular mesangial cells
b/w afferent & efferent arterioles at vascular pole, associated w/ juxtaglomerular apparatus
What are the characteristics and functions of mesangial cells?
Contractile = modify blood flow thru glomerular capillaries
Phagocytic - recycles worn out glomerular basal lamina, phagocytose immunoglobulins trapped in basal lamina
Proliferative
Synthesize matrix & collagen
Secrete prostaglandins and endothelins
Respond to angiotensin II
Provide mechanical support & regulate blood flow
Which cells help modify blood flow through the glomerular capillaries?
Mesangial cells
What are the components of the juxtaglomerular apparatus?
Macula densa
Extraglomerular mesangial cells
Juxtaglomerular cells
What are the functions of the macula densa?
Responds to changes in [Na+] and [Cl-] in urine or hypotensin
Signals renin release from juxtraglomerular cells
Involved in regulation of fluid-electrolyte balance and blood pressure regulation
Reversed polarity of cells; formed by elongated, densely packed cells in wall of convoluted tubule
What are the characteristics of the juxtaglomerular cells? What are they made up of?
Modified smooth muscle cells associated w/ macula densa and afferent arteriole
Secrete renin into blood; stimulated by mascula densa
Innervated by sympathetic nerve endings w/ increase renin release
What are the components of the renal tubule? (5)
PCT
Descending LOH
LOH
Ascending LOH
DCT - continuous w/ collecting duct
What are the components of the renal filtration barrier?
Fenestrated endothelium of glomerular capillaries
Fused basal laminae of endothelial cells & podocytes
Filtration slits
What are the filtration slits of the renal filtration barrier made up of? Basal lamina?
Fenestrated endothelium of capillaries
Basal lamina = Type IV collagen, fibronectin, laminin, heparin sulfate
Filtration slits created by adjacent pedicels of podocytes; pedicels are attached to basal lamina via alpha-3-beta-1 integrins
What creates the filtration slits of the renal filtration barrier?
Pedicels of the podocytes
Where does the PCT begin and end?
Extends from the urinary pole of the renal corpuscle to the beginning of the LOH
What are the characteristics of the PCT? What type of epithelium? Cytoplasm? Nuclei?
Simple cuboidal made up of truncated pyramidal cells
Apical - tight juncts & brush border
Basolateral infoldings & interdigitations
Basal striations w/ abundant mitochondria
large, pale-staining nuclei
Eosinophilic cytoplasm
What are the functions of the PCT?
Reabsorbs majority of filtrate including H2o, glucose, and amino acids, Na+ and Cl-
Characterized by a complex set of transporters, co-transporters, channels, and exchangers
What type of cells make up the thick segments (thick ascending LOH) of the LOH?
Simple low cuboidal epithelium
No brush border, more basal vertical striations
Impermeable to water
What type of epithelium makes up the thin LOH (thin descending and ascending LOH)
Simple squamous epithelium
What are the functions of the thin descending LOH?
Permeable to water, Na+, Cl- ions
Makes medulla less salty
Hyperosmotic
Helps to establish a countercurrent exchange system
What is the counter-current exchange system?
Creates the osmotic conditions that are necessary to pull water out of the DCT and collecting duct in the presence of ADH
What is the function of the thin ascending LOH?
Impermeable to water
Makes medulla salty by actively pumping Cl- ions out, with Na+ following
What type of cells make up the DCT? PCT?
DCT - simple cuboidal with smaller nuclei
PCT - simple cuboidal with LARGE nuclei
What are the 3 distinguishable characteristics of the PCT and DCT?
DCT has a larger lumen than PCT (think veins)
A less eosiniphilic cytoplasm
Smaller cells/nuclei
Impermeable to water except when in the presence of ADH/vasopressin (via posterior pituitary)
What type of epithelium makes up the collecting duct?
Simple cuboidal epithelium
What two specialized cells are involved with the collecting duct? What are their functions?
Principal cells
Reabsorb Na+ and H2o, Secrete K+ via ATPase
Intercalated cells
Secrete either hydrogen or bicarbonate ion, Reabsorb K+
What are the 4 layers of the renal pelvis, ureter, and urinary bladder?
Mucosa
Submucosa (not clearly demarcated)
Muscularis
Adventitia (FECT external to muscularis)
What type of epithelium make up the mucosa of the renal pelvis, ureter, and urinary bladder? What are the other characteristics?
Transitional/Urothelium epithelium
Basement membrane
Lamina propria of FECT
Some loose lymphoid tissue
Few smooth muscle cells
What are the features of the muscularis layer of the renal pelvis, ureter, and urinary bladder?
Inner = longitudinal smooth muscle coat
Outer = circular smooth muscle coat
Lower 3rd of ureter has a 3rd external longitudinal coat
Smooth muscle layers of bladder = detruser muscle
What are the 4 components of the male urethra? Type of epithelium in each?
MGCP - Male’s Grow Colorful Penises
Membranous Urethra - tall pseudostratified columnar, variable
Glands
Cavernous Urethra - pseudostratified epithelium w/ patches of stratified squamous
Prostatic urethra - mucosa lined w/ transitional/urothelium
What are the characteristics of the prostatic urethra of the male urethra?
Mucosa lined with transitional/urothelium epithelium
Section of urethra passing thru prostate gland
Highly vascularized w/ veins and abundant elastic tissue
What are the characteristics of the membranous urethra of the male urethra?
Tall pseudostratified columnar cells, variable
Extends thru urogenital diaphragm and receives straiated muscle cells = external sphincter of bladder
What are the 2 types of glands of the male urethra?
Lacunae of Morgagni
invaginations of mucous membrane w/ single/groups of intraepithelial mucous cells
Gland of Littre
Branched tubulara glands opening into lacunae of Morgagni
Which portions of the female urethra are not discernible? (2)
Leave a female AS IS!
Adventitia
Submucosa
What type of epithelium is the mucosa of female urethra?
Stratified or Pseudostratified columnar epithelium w/ intraepithelial nests of mucous glands
Characteristics of the lamina propria and muscularis of the female urethra?
Lamina Propira - highly vascularized w/ veins and abundant elastic tissue
Muscularis - inner longitudinal and outer circular layer of smooth muscle cells but not well defined
What is the function of renin?
Converts protein Angiotensinogen to Angiotensin I
What is the function of ACE in the Renin-Angiotensin-Aldosterone system?
Converts Angiotensin I to Angiotensin II
What is the function of Angiotensin II?
Stimulates secretion of aldosterone from adrenal cortex - acts on principal cells and collecting ducts, thick ascending LOH
Increases reabsorption of Na+ and Water = increases BP
Stimulates ADH release
