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
Mouse renal podocyte EM02.jpg

Mouse renal podocyte (EM)[1]

Transmission electron micrscopy of a mouse glomerular capillary revealing the structural composition of the glomerulus.


The primary filtrate drains into Bowman’s space (BS) and, via the urinary pole, reaches the proximal tubule.


On the outside of the capillary, the foot processes (FP) cover a major part of the glomerular basement membrane (GBM) circumference.


The slit-diaphram can be discerned in between the foot processs.


The endothelial cell coats the inner surface of the capillary wall and is followed by the three layers of the glomerular basement membrane (GBM).

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

References

  1. 1.0 1.1 Florian Grahammer New structural insights into podocyte biology. Cell Tissue Res.: 2017; PubMed 28283912

Terms

Renal Terms  
  • bladder exstrophy - A congenital malformation with bladder open to ventral wall of abdomen (between umbilicus and pubic symphysis) and may have other anomolies associated with failure of closure of abdominal wall and bladder (epispadias, pubic bone anomolies).
  • blastema - Term used to describe a mass of undifferentiated cells. (More? Wilm's tumour)
  • Bowman's capsule - (capsula glomeruli, glomerular capsule) Surrounds the glomerulus within the nephron with a vascular and urinary pole and is the beginning of the tubular component. Named in 1842 after Sir William Bowman (1816 – 1892) an English surgeon and anatomist.
  • diabetes insipidus - The disorder is related to the hormone antidiuretic hormone (ADH, also called vasopressin) its synthesis, secretion, receptors and signaling pathway. In diabetes insipidus there is an excretion of large amounts (up to 30 litres/day) of a watery urine and an unremitting thirst.
  • fenestrated capillary - Specialised capillaries containing circular pores (fenestrae) that penetrate the endothelium, may be closed by a thin diaphragm.
  • glomerulus - The capillary network (tuft) within Bowman's capsule of the nephron enters at the vascular pole (afferent and efferent arteriole).
  • hydronephrosis - (congenital hydronephrosis, Greek, hydro = water) A kidney abnormality due to partial or complete obstruction at the pelvi-ureteric junction. This leads to a grossly dilated renal pelvis causing extensive renal damage before birth.
  • hyperplastic rests - In kidney development, embryonic blastema cells can persist and proliferate to form a pool of cells, which under either genetic or epigenetic influence can then change to become a neoplastic rest. Normally the majority of nephrogenic rests either regress or become dormant.
  • juxtaglomerular cells - Cells located at the vascular pole that secrete renin and form a part of the juxtaglomerular complex.
  • loop of Henle - Nephron region spanning from the proximal convoluted tubule to the distal convoluted tubule. Named after Named after Friedrich Gustav Jakob Henle (1809–1885) a German anatomist.
  • macula densa - Columnar cell cluster located in the wall of the ascending limb at the transition to distal convoluted tubule in the nephron. Involved in sodium chloride regulation.
  • mesangial cells - Cells in the nephron glomerulus that form the connective tissue giving structural support to podocytes and vessels.
  • mesonephros - The second temporary stage of kidney development (pro-, meso-, meta-). The intermediate mesonephros develops and disappears with the exception of its duct, the mesonephric duct, which will form the male reproductive duct system. In males, the mesonephric tubules go on to form the ducts of the testis. In females, these degenerate. A few mesonephric tubules remain as efferent ductules in the male and vestigial remnants in the female.
  • mesonephric duct - (= Wollfian duct) An early developing urogenital duct running the length of the embryo that will differentiate and form the male reproductive duct system. In females this duct degenerates (some remnants may remain associated in broad ligament).
  • metanephros - The adult kidney, third stage of mammalian kidney (pro-, meso-, meta-) development within the intermediate mesoderm.
  • metanephric cap - In kidney development, the intermediate mesoderm which surrounds the ureteric bud and will develop into nephrons.
  • Multicystic Kidney - There is no functional kidney tissue present in the kidney and it is replaced by a multilocular cyst. This is non-familial and is produced by atresia of a ureter and is always unilateral.
  • neoplastic rest - In kidney development, a neoplastic rest can develop under either genetic or epigenetic influence from a hyperplastic rest, originating from an embryonic blastema cell. Normally the majority of nephrogenic rests either regress or become dormant.
  • nephrogenic rest - A kidney term used to describe the embryonic blastema cells which persist and under either genetic or epigenetic can change to become a neoplastic rest. These neoplastic rests can develop postnatally as a benign form (adenomatous rest) or a malignant Wilm's tumour form. The rests are further characterised by the time of generation leading to different anatomical kidney locations: early intralobar nephrogenic rests (within the renal lobe) and late pelilobar nephrogenic rests (periphery of the renal lobe)
  • nephron - (Greek, nephros = kidney) The functional unit of the kidney.
  • nephros - (Greek, nephros = kidney) Term used to describe features associated with the kidney. (pronephros, mesonephros, metanephros, nephric, nephron, nephroblastoma).
  • parietal layer - Cells of the outer of Bowman's capsule that form a simple squamous epithelium. The inner layer is the visceral layer.
  • podocyte - (visceral epithelial cell) kidney glomerulus cell forming the main component of the glomerular filtration barrier. (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.
  • podocyte specific proteins - podocalyxin, glomerular epithelial protein-1, podocin, nephrin, synaptopodin, and alpha-actinin-4), podocyte synthesized proteins (vascular endothelial growth factor and novH), transcription factors (WT1 and PAX2).
  • pronephros - (Greek, pro = before) The first temporary stage of kidney development (pro-, meso-, meta-). This forms the kidney of primitive fish and lower vertebrates. Kidney development occurs within the intermediate mesoderm interacting with endoderm. In humans, this very rudimentary kidney forms very early at the level of the neck. It is rapidly replaced by the mesonephros, intermediate stage kidney, differentiating in mesoderm beneath.
  • proteinuria - The abnormal presence of protein in the urine and an indicator of diesease including diabetic kidney disease (DKD, diabetic nephropathy).
  • proximal tubule -
  • renal - (Latin, renes = kidney) Term used in relation to the kidney and associated structures (renal pelvis, renal artery)
  • transitional epithelium - (urothelium)
  • trigone - refers to the urinary bladder triangular region formed by the two ureters and the urethra.
  • ureter - The two ureters are hollow tubes that link the kidney and the bladder and carry urine. They develop from the ureteric bud and are lined by a transitional epithelium with an outer muscular wall.
  • urethra - The single muscular tube that links and carries urine from the bladder to the exterior. In humans, the urethral length differs between the sexes (male longer, female shorter).
  • vascular pole - The side of nephron Bowman's capsule where the afferent arteriole and efferent arteriole enter the glomerulus. image
  • visceral layer - Cells (podocytes) of the inner of Bowman's capsule that form extremely complex shapes. Cytoplasm form a fenestrated epithelium around the fenestrated capillaries of the glomerulus. The outer layer is the parietal layer.
  • urinary - Term used to describe all components of the kidney system including the bladder, ureters and urethra.
  • urinary pole - The side of nephron Bowman's capsule where the proximal convoluted tubule starts. image
  • urine - Term used to describe the liquid waste produced by the kidney, stored in the bladder and excreted from teh body through the urethra.
  • urorectal septum - (URS) The structure which develops to separate the cloaca (common urogenital sinus) into an anterior urinary part and a posterior rectal part.
  • Wilms' tumour - A form of kidney/renal cancer (nephroblastoma) named after Dr Max Wilms who first described the tumor. This childhood kidney cancer is caused by the inactivation of a tumour suppressor gene (BRCA2) or Wilms tumor-1 gene (Wt1) and is one of the most common solid tumors of childhood, occurring in 1 in 10,000 children and accounting for 8% of childhood cancers. Wt1 also required at early stages of gonadal development. (More? OMIM - Wilm's tumour | Dr Max Wilms)
  • Wilms' tumor 1-associating protein - (WTAP) protein expressed in extraembryonic tissues and required for the formation of embryonic mesoderm and endoderm.
  • Wolffian duct - (= mesonephric duct, preferred terminology), runs from the mesonephros to cloaca, differentiates to form the male vas deferens and in the female regresses. Named after Caspar Friedrich Wolff (1733-1794), a German scientist and early embryology researcher and is said to have established the doctrine of germ layers. (More? Caspar Friedrich Wolff)
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Cite this page: Hill, M.A. 2017 Embryology Renal System Histology. Retrieved June 29, 2017, from https://embryology.med.unsw.edu.au/embryology/index.php/Renal_System_Histology

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