URINARY TRACT – I
The kidney
Maria M. Picken MD, PhD
mpicken@luc.edu
Renes = Latin kidneys
nephros = Greek kidney
Outline:
I – the kidney
development
gross structure
vasculature
Objectives:
General objectives:
- to identify the kidney’s structures, function and location
- to analyze the relationship between microscopic structure and function
Specific objectives:
1. Identify elements of the gross and microscopic structure of the kidney and analyze the relationship between them
2. Identify developmental stages of kidney and their position
3. On gross kidney identify: cortex, medulla, papillae at apex of medullary minor calyces, major calyces, renal pelvis
4. Describe the renal blood supply: renal artery, arcuate arteries, interlobular arteries, differences between cortical
and medullary blood supply, define arterioles (afferent and efferent), peritubular capillary plexus
Retroperitoneum,
Thoracic vertebra12-Lumbar vertebra3
115-170 g (M>F)
11-12 x 5-7.5 x 2.5-3 cm
- Kidneys – paired, bean shaped
- Ureters – paired
- urinary bladder
- Urethra, male versus female
Renes = Latin kidneys
Nephros = Greek kidney (Nephrology)
Function:
1. Filter blood & reabsorb nutrients
2. Control water, ion, and salt balance of the body
3. Maintain acid-base balance of the blood (pH)
4. Excrete metabolic wastes (urea and uric acid), toxins, drug components
5. Secrete hormones (renin, erythropoietin)
6. Produce calcitriol (active form of vitamin D – absorption of dietary calcium into the blood)
Kidney development through a series of successive phases:
- the pronephros (most immature)
- mesonephros
- metanephros, persists as the definitive adult kidney
http://www.meddean.luc.edu/lumen/MedEd/urology/nlrendev.htm
Kidney development - complex
3 stages: pronephros, mesonephros, metanephros
cranial to caudal direction followed by “ascend”
- mesonephric duct comes in contact with cloaca, grows cranially as ureteric bud
- ureteric bud & metanephros reciprocally induce growth, forming kidney
- the kidney “ascends”
- takes new arterial supply from the aorta, new venous drainage into the vena cava
developmental abnormalities are relatively common
important in pediatric nephrology
6
Kidney structure: bean shaped
- capsule
- cortex (outer)
- medulla (inner)
- hilum (pelvis, ureter, renal artery, vein)
Cortex, renal columns (septa) of Bertin
(cortical tissue on either side of the medullary pyramids)
Medulla divided into several conical pyramids
Papillae at apex of medullary pyramid
Papillae lead into minor calyces
Minor calyces lead into 2-3 major calyces
Major calyces lead to the expanded upper end of the ureter, renal pelvis (latin: pelvis=basin)
Glossary:
capsule - a structure enclosing an organ, usually composed of dense connective tissue
cortex - the outer portion of an organ, distinguished from its inner, medullary portion
septum/septa - a wall, dividing a cavity or structure into smaller ones
calyx; plural noun: calyces - a cuplike cavity or structure
minor – lesser, small, major - greater
hilus or hilum - a depression or pit at that part of an organ where the vessels and nerves enter
medulla - the inner portion of an organ, usually in the center
See also: http://www.bu.edu/histology/m/glossary.htm
on either side of medullary pyramid
Posterior division
of renal artery
Interlobular
arteries
Kidney blood supply:
0.5% of total body weight, 25% of the cardiac output
- renal artery, anterior & posterior divisions, segmental arteries (do not anastomose, “end arteries”)
- interlobar arteries on either side of medullary pyramid
- arcuate artery (Latin = curved) between cortex and medulla, parallel to kidney surface), interlobular arteries
Posterior segment
juxtamedullary
glomerulus
- interlobular arteries → afferent arteriole → glomerulus → efferent arterioles
- efferent arterioles in the cortex form peritubular capillary plexus
- efferent arterioles of juxtamedullary nephrons (juxta [Latin] close to)
go into medulla and loop back “vasa recta” (straight vessels [Latin])
Afferent, from afferre [Latin] = to bring toward
Efferent, from efferre [Latin] = to bring out
Correlation with pathology:
- cortex: 90% of blood supply
- medulla is relatively a-vascular (10%, low oxygenation)
- tubular capillary beds derived from the efferent arterioles
- acute tubular necrosis (injury), papillary necrosis
vascular pole
Bc
*
tubular pole
Afferent arterioles arise from interlobular vessels
and supply the glomeruli
Efferent arterioles arise from glomerular capillaries
Glomerulus in paraffin section:
Bowman’s capsule (Bc)
+
glomerular tuft*
Questions?
mpicken@luc.edu