Renal System Histology

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Introduction

Nephron histology

This section of notes gives an overview mainly of adult renal histology, see also Renal System Development notes. A key structure of the kidney functional unit, the nephron, is the glomerulus (renal corpuscle), which represents the initial vascular/renal interface.

HMsmall.jpg
Page also provides further background information for Medicine phase 1 Health Maintenance B Urinary Tract Histology Practical Virtual Slides. This page content is not part of the HMB practical class.


HMB: Pancreas Histology | Liver Histology | Gall Bladder Histology | Renal System Histology
{Renal Links}}
Renal Histology: Histology | Histology Stains | Renal Development
Kidney - Nephron overview | Glomerulus | Vascular and renal poles | Medullary ray | tubules
Ureter - Ureter labeled | Ureter epithelium
Bladder - overview | wall 1 | wall 2 | transitional epithelium | Urinary Bladder Development

Kidney Anatomy

Kidney cartoon.jpg
  1. Parenchyma
  2. Cortex
  3. Medulla
  4. Perirenal fat
  5. Capsule
  6. Ureter
  7. Pelvis of kidney
  8. Renal vessels
  9. Hilum
  10. Calyx
Gray1128.jpg

Adult nephron structure

Nephron
  • Functional unit of kidney
  • Humans up to 1 million
  • Filtration of waste from blood
  • Endocrine
  • Blood pressure regulation

Nephron Histology

  • Development - mean glomerular number shown to level at 36 weeks, increasing from about 15,000 at 15 weeks to 740,000 at 40 weeks.

Glomerulus

Nephron histology 01.jpg Nephron histology 02.jpg
Glomerulus structure Vascular and renal poles
Links: glomerulus structure image | vascular and renal poles image

Nephron Tubules

Nephron histology.jpg

Nephron overview

Nephron histology 03.jpg Nephron histology 04.jpg


Renal System Histology: Nephron tubule overview | glomerulus structure | vascular and renal poles | Medullary rays | Nephron tubules
Large Images: medullary rays | glomerulus | distal tubule and collecting duct | proximal and distal tubule | distal and intermediate tubule | medullary ray | glomerulus | proximal tubule | Renal System Development

Large Images

Ureter Histology

  • The adult ureter is a thick-walled muscular tube, 25 - 30 cm in length, running from the kidney to the urinary bladder.
  • Anatomically can be described in two parts the abdominal part (pars abdominalis) and pelvic part (pars pelvina).
  • The ureter is composed of three layers: outer fibrous layer (tunica adventitia), muscular layer (tunica muscularis) and mucous layer (tunica mucosa).
  • The muscular layer has also been described as being subdivided into 3 fibre layers:
  1. an external longitudinal
  2. a middle circular
  3. an internal longitudinal
Adult bladder.jpg

Ureter histology 001.jpg Ureter histology 002.jpg

Bladder Histology

Can be described anatomically by its 4 layers from inside outward:
  • Mucosa - (mucus layer) a transitional epithelium layer formed into folds (rugae).
  • Submucosa - connects the muscular layer with the mucous layer.
  • Muscular - the detrusor muscle is the muscle of the urinary bladder wall.
  • Serous - the superior or abdominal surfaces and the lateral" surfaces of the bladder are covered by visceral peritoneum, the serous membrane (serosa) of the abdominal cavity, consisting of mesthelium and elastic fibrous connective tissue.


Detrusor Muscle

  • The adult detrusor muscle consists of three layers of smooth (involuntary) muscle fibres.
    • internal layer - fibres arranged longitudinally
    • middle layer - fibres arranged circularly
    • external layer - fibres arranged longitudinally

Note that while the smooth muscle fibre layer organisation is described as longitudinal or circular, this is only a general organisation of fibre direction, and is better described as a "spiral" organisation.

Bladder histology.jpg

Fetal Kidney

Fetal Renal Links: fetal kidney histology 01 | fetal kidney histology 02 | fetal kidney histology 03 | fetal kidney histology 04


Fetal Urethra Histology

Images

External Links

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Practical Overview

retroperitoneal kidney

Normal Histology

  • kidneys, ureters, urinary bladder, urethra

Anatomy

  • retroperitoneal
  • kidney - bean shaped
  • rich blood supply

Kidney Function

  • elimination of foreign substances
  • regulation of the amount of water in the body
  • control of the concentration of most compounds in the extracellular fluid
  • filtration - glomeruli of the kidney
  • selective resorption and excretion - tubular system of the kidney
Capsule
  • outer layer - dense CT (fibroblasts and collagen
  • inner layer - myofibroblasts
Cortex
  • outer renal corpuscles
  • medullary rays
    • only straight tubules + straight collecting tubules
    • 400-500 project medulla to cortex
  • between medullary rays - convoluted tubules of nephrons
Medulla
  • medullary pyramids (together with associated cortical region = renal lobe)
    • base at cortioco-medullary border
    • apex at renal papilla (surrounded by minor calyx)
  • minor calyces converge to form major calyces then renal pelvis

Blood Supply

  • renal artery
  • interlobar arteries (across medulla thru renal columns)
  • arcuate arteries (cortico-medullary junction)
  • interlobular arteries
  • afferent glomerular arterioles
  • glomerular capillary network
  • efferent glomerular arterioles

Vasa Recta

  • descending arterioles (arteriole rectae) + ascending venules (venulae rectae)

Glomerulus

  • glomerulus - round (~0.2 mm in diameter) blind beginning of the nephron
  • vascular pole - invaginated by a tuft of capillaries
  • urinary pole - substances leave the capillaries enter the renal tubule
  • Bowman's capsule - anatomical glomerulus is enclosed by two layers of epithelium.
    • outer or parietal layer of Bowman's capsule form a simple squamous epithelium.
    • inner layer, podocytes in the visceral layer, are extremely complex in shape.
  • Mesangial cells in the glomerulus form the connective tissue that gives structural support to podocytes and vessels (Podocytes, mesangial cells, glomerular capillaries)
  • Juxtaglomerular cells - smooth muscle cells afferent glomerular arteriole (epithelial-like cells)
  • Macular Densa
    • distal convoluted tubule near vascular pole (narrower and taller than rest of DCT)

Tubules

Proximal Convoluted Tubules (PCT)

  • brush border
  • star-shaped
  • larger outside diameter

Distal Convoluted Tubules (DCT)

  • clean lumen surface
  • apical nuclei

Collecting Tubules (CT)

  • larger lumen than DCT (about size of PCT)
  • cuboidal cells and smaller than DCT

Renal Pyramids

  • medullary straight tubules, ducts and vasa recta
  • apical renal papilla - simple cuboidal/columnar epithelia
  • calyx - lined by transitional epithelia

Note the urinary system transitional epithelium is also known as urothelium.

Ureters

  • epithelium - transitional epithelia
  • lamina propria - mainly of dense connective tissue, with many bundles of coarse collagenous fibres
  • muscularis - consists of an inner longitudinal and outer circular layer of smooth muscle cells
    • In lower parts of the ureter and the bladder an additional outer longitudinal layer of muscles is added to the first two.

Bladder

  • epithelium - transitional epithelia
    • apical plaques - thickened domain allows great changes in surface area.
  • lamina propria - mainly of dense connective tissue, with many bundles of coarse collagenous fibres
  • muscularis - consists of an inner longitudinal and outer circular layer of smooth muscle cells
    • In the bladder (and lower parts of the ureter) an additional outer longitudinal layer of muscles is added to the first two.

Urethra

  • penile urethra within corpus spongiosum
  • pseudostratified columnar epithelia
  • distal end - stratified squamous
  • continuous with outer skin

Terms

  • arcuate artery -
  • Bowman's capsule - Term describing the cup-shaped double epithelium surrounding the glomerulus of the nephron within the kidney. The outer parietal layer is a squamous simple epithelium. The inner visceral layer is formed by podocytes covering glomerular capillaries.
  • collecting tubule -
  • distal tubule -
  • glomerulus -
  • medullary ray -
  • nephron - Term describing the functional unit of the kidney. Formed by blood vessels and specialised epithelia.
  • podocyte - (glomerular podocyte) Kidney epithelial cell type in the nephron (kidney functional unit) located in the glomerulus. Podocytes form the visceral layer of Bowman's capsule and are at the filtration barrier between capillary blood and the nephron tubular system and function to ultrafiltrate blood, and support glomerular capillary pressures. The differentiation of podocytes involves the formation of cellular foot processes and then the slit membrane.
  • proximal tubule -
  • renal corpuscle -
  • transitional epithelium - (urothelium)


Glossary Links

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Cite this page: Hill, M.A. 2017 Embryology Renal System Histology. Retrieved February 27, 2017, from https://embryology.med.unsw.edu.au/embryology/index.php/Renal_System_Histology

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© Dr Mark Hill 2017, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G