MODULE 1: UNIT 1 – RENAL ANATOMY
Urinary System
• Remove metabolic waste
➢ By removing waste from blood and excrete in urine
• Regulate blood composition, pH, volume, pressure
• Maintain blood osmolality, produce hormones
• Consists of kidney, ureter, urinary bladder, urethra
➢ Kidney – main organ responsible for urine formation
Anatomy of Kidney
• Paired, reddish, bean shaped
• Location: retroperitoneal; Right kidney – lower
• L: 10-12cm, W: 5-7cm, T: 3cm, M: 135-150g, size = bar soap
• Indentation at concave side (Renal Hilum)
• 3 layers of tissue:
1. Renal Fascia
▪ Superficial layer
▪ Dense irregular connective tissue
▪ Anchor to organs
2. Adipose Capsule
▪ Beneath renal fascia
▪ Fatty tissue
3. Renal Capsule
▪ Innermost layer
▪ Dense irregular tissue
▪ Maintain shape
•
Cross-section
1. Renal Cortex
▪ Superficial layer
▪ Granular appearance, light red (macroscope)
▪ Outer cortex – exclusive site for plasma filtration
because all glomeruli is located here
2. Renal Medulla
▪ Dark red inner layer
▪ Renal tissue
o Renal Colum
▪ Portion of the renal cortex, extend toward medulla
▪ Divide renal medulla to renal pyramids
o Renal Lobe – renal pyramid, overlying renal cortex, half of
the adjacent renal column
o Renal Parenchyma
▪ Functional portion
▪ Consist of cortex and medulla
o Renal Papilla
▪ Apex of each pyramid
▪ Drains urine to renal calyx
o Minor calyx
▪ Receive urine from renal papilla
▪ Join together to form 2-3 major calyces
o Major calyx – drain urine to renal pelvis (funnel-shaped)
o Renal pelvis –> ureter
Nephron as a Functional Unit
• 1.3mil nephrons each kidney
• Cortical nephron (85%)
➢ Located in renal cortex
➢ Primarily remove waste
➢ Reabsorb nutrients
• Juxtamedullary nephrons
➢ Closer to medulla
➢ Concentrate urine
➢ Longer loop of Henle – extend toward medulla
•
3 regions:
1. Renal Corpuscle
▪ Glomerulus
o Network of fenestrated capillaries
o Surrounded by bowman’s capsule
o Blood is filtered –> low molecular weight
plasma unfiltrate –> Bowman’s space –>
renal tubule
▪ Bowman’s Capsule
o Thin epithelial layer
o Where renal tubule originates
▪
Four distinct regions
a. Mesangium
✓ Mesangial cells
✓ Contractile – contribute to
controlling blood flow in glomerulus
✓ Remove entrapped macromolecules
via phagocytosis and pinocytosis
b. Fenestrated Endothelial Cells
✓ Large open pores (50-100nm)
✓ Negatively charged coating – repel
anionic molecules that confer
solute selectivity during filtration
c. Podocytes/Visceral Epithelial Cells
✓ Foot-like
✓ Completely cover glomerular
capillary w/ finger-like projections
that interdigitate to form snake like
chamber (filtration slit)
✓ Filtration slits – lined with
extracellular structure (slit
diaphragm)
d. Three-layered basement membrane
✓ Separate endothelium of urinary
space from endothelium of
glomerular capillaries
✓ 3 layers: lamina rara, lamina densa,
lamina rara externa
✓ 3 layers contribute to permeability
of glomerular filtration barrier due
to heparan sulfate which confers a
negative charge in the structure
▪
Juxtaglomerular apparatus
o Vascular pole
o Composed of juxtaglomerular cells of
afferent and efferent arteriole, mesangial
cells, specialized cells in distal convoluted
tubule (maula densa – detect and respond
to changes in pressure)
▪ Juxtaglomerular cells contain large quantities of
renin – released when there is change in pressure
2. Renal Tubule
a. Proximal convoluted tubule
o Begin at glomerulus
o Lined with simple cuboidal epithelium –
interdigitate to increase surface area
o Microvilli – facilitate reabsorption
b. Loop of Henle
o
o
o
Thin descending limb – simple squamous,
differ in permeability – >lack interdigitation
Thin ascending limb – simple squamous
Thick ascending limb – simple columnar to
low columnar, interdigitate
c.
3.
➢
➢
➢
Distal Convoluted Tubule
o Reenter cortex
o Simple cuboidal
Collecting duct
▪ Simple cuboidal
▪ No interdigitation, principal cells and intercalated
cells
Principal cells
▪ Receptors for Antidiuretic Hormone (ADH) and
aldosterone
Intercalated cells - regulation of blood pH
When ADH is present, spaces b/n cells dilate making it more
permeable to water