Seediscussions,stats,andauthorprofilesforthispublicationat:
https://www.researchgate.net/publication/22630051
Morphometricobservationsonthe
kidneyofthecamel,Camelus
dromedarius
ArticleinJournalofAnatomy·September1979
Source:PubMed
CITATIONS
READS
36
376
2authors,including:
MohamedAhmedAbdalla
UniversityofKhartoum
28PUBLICATIONS281CITATIONS
SEEPROFILE
Availablefrom:MohamedAhmedAbdalla
Retrievedon:20July2016
J. Anat. (1979), 129, 1, pp. 45-50
With 1 figure
Printed in Great Britain
45
Morphometric observations on the kidney of the camel,
Camelus dromedarius
M. A. ABDALLA
and
0. ABDALLA
Department of Anatomy, Faculty of Veterinary Science, University of
Khartoum, P.O. Box 32, Khartoum North, Sudan
(Accepted 12 June 1978)
INTRODUCTION
Sperber (1944) was one of the first to note that certain features of renal anatomy
in different mammals vary with the aridity of the habitat. According to the countercurrent theory developed since then, the efficiency of urine concentration and dilution in the mammalian kidney can be inferred from the structure of the renal medulla
and the length of the loop of Henle (Vimtrup & Schmidt-Nielsen, 1952; Lamdin,
1959; Schmidt-Nielsen & O'Dell, 1961; Berliner & Bennett, 1967; Marsh, 1971).
Evidence in favour of the countercurrent theory was first brought together by Hargitay & Kuhn (1951) and Wirz (1954). The theory has been tested and confirmed in
mammals from widely different habitats (Schmidt-Nielsen, 1958, 1964; Gottschalk
& Mylle, 1959; Pfeiffer, Nungesser, Iverson & Wallerius, 1960; Wirz & Dirix, 1973).
The kidney of the camel is known to play a vital role in water conservation through
the production of a highly concentrated urine (Schmidt-Nielsen, 1964). However,
those anatomical features which should be present in a kidney capable of producing
highly concentrated urine have not been deliberately looked for in the camel. The
available information on the camal kidney is mainly concerned with general morphology and topography (Chauveau, 1891; Lesbre, 1906; Leese, 1927; Droandi, 1936;
Tayeb, 1948; Joseph, 1969; Abdalla, 1973).
This paper reports some measurements made on the kidney of the one-humped
camel in an attempt to correlate structure and urine-concentrating capacity.
MATERIALS AND METHODS
Ten pairs of kidneys were collected from adult animals of both sexes at Tamboul
camel slaughterhouse.
For macroscopic morphometry the volume of each kidney was determined by
water displacement (Scherle, 1970). This was confirmed by calculating the volume
of each kidney from its length, width and thickness. Each kidney was cut into slices
about 1 cm thick across its long axis. The volumetric proportions of the cortex,
medulla and renal pelvis were determined by the point-counting method (Dunnill,
1968). A transparent grid with points arranged in a hexagonal lattice was superimposed on the slices in turn. The hexagonal arrangement of points was preferred
to the quadratic lattice (Weibel, 1963 a). The points were 0 5 cm apart. The relative
thickness of the medulla was calculated as follows: relative thickness = mean thickness of the medulla x 10 . cube root of kidney volume, where kidney volume is the
product of the dimensions of the kidney (Sperber, 1944).
For microscopic analysis, five kidneys from five animals were used. Five blocks
0021-8782/79/2828-6190 $02.00 © 1979 Anat. Soc. G.B. & I.
46
M. A. ABDALLA AND 0. ABDALLA
of tissue were taken from different parts of the cortex of each kidney following a
standard method of sampling (Weibel, 1963b). The blocks of cortical tissue were
then fixed in buffered neutral formalin and paraffin sections were cut at 7,am. The
sections were stained with haematoxylin and eosin. One section from each block was
selected as being the best technically (Weibel, 1963a). In such sections the volumetric proportions of the glomeruli, tubules, and interstitial tissue with its blood
vessels were estimated by the recently developed dual purpose Zeiss integrating eyepiece. In each case 20 adjacent fields were analysed, covering almost the whole
section (using a x 16 objective and a x 1 2-5 eyepiece). The surface area of the tubules
in the cortex was estimated by the linear intercept method (Tomkeieff, 1945; Hennig,
1956), using the same Zeiss eyepiece. The diameter of the glomeruli was measured
with a graticule. The method of Weibel & Gomez (1962) was used to estimate the
number of glomeruli in each kidney.
The statistical analysis of the data obtained in this study was restricted to the
calculation of the arithmetic mean and standard deviation, as suggested by Weibel
(1 963 a).
RESULTS
Analysis ofgross slices
The average volume of a kidney in the sample of adult camels studied was 858 ±
10 cm3 (mean + standard deviation). The volumetric proportions of the main components of the kidney are shown in Table 1.
The renal cortex occupied about 50 % by volume of the kidney. The ratio of the
volume of cortex to medulla was 1-3:1, whereas the medullary/cortical thickness
ratio was about 4:1. Measurements of the medulla were made from the corticomedullary junction to the edge of the renal crest. The long axis of the medulla was
about 16 cm. On the other hand the relative thickness of the medulla, which is an
indicator of the length of the loops of Henle, was about 7-89. The renal crest itself
was well developed (Fig. 1), and measured about 4 cm across its long axis.
The volumetric proportion of the renal pelvis included all the tissues other than
cortex and medulla.
Table 1. The percentage and absolute volumes of the main components of the kidney
obtained from the analyses of the gross slices
(The values are the arithmetic means and standard deviations of the populations studied.)
Component
Percentage volume
Absolute volume (cm3)
Cortex
51-37+ 2-03
38-78 + 2-09
9 77+1-10
440 75 + 5 2
332-73 + 40
83-82 + 2-6
Medulla
Pelvis
Measurements on histological sections
The measurements made on sections of the cortex are shown in Table 2. The
absolute volume of the cortical tubules could be of functional significance. It was
found to be about 335 5 cm3 in each kidney. The total glomerular volume was
about 51-13 cm3. The rest of the cortical volume was occupied by interstitial tissue
including blood vessels.
Sections of the medulla taken near the edge of the renal crest (inner medulla)
Morphometry of the camel's kidney
\b
-'
..
.
4.
\
47
A
4
.--.
½
7.
- --- ----
,m
..
%.
..
I
-1,
v4N. -!N;:. t
,
.1.0
1
$
V44
I
X
A
t
Fig. 1. Longitudinal section of the right kidney of the camel. Note the well developed renal crest
and medullary pyramids separated by branches of the renal pelvis. The kidney was fixed
through the renal artery with 5 % formalin. x i.
Table 2. Histological analysis of the renal cortex
(The values pertain to each kidney and represent the arithmetic means and standard deviations.)
Percentage volume of cortex occupied by
____________
_ Tubules
Glomeruli
76-12+2-8
11-6+1-5
Interstitial
tissue
12-26+1-6
Number of
glomeruli
Diameter of Total surface area
glomerulus of tubules of cortex
(x 106)
(AgM)
(m2)
3-6±0-12
245+10
9-46+1-7
showed that the greater part of any given field was apparently occupied by thin
segments of the loops of Henle and collecting ducts.
DISCUSSION
Previous studies on the mammalian kidney have indicated that the ability to
concentrate urine is related to three main structural features. The first, and apparently the most important, is the relative thickness of the medulla. This is an index
of both the length of the loops of Henle, which act as a countercurrent multiplier
system, and of the length of the vasa recta, which act as a countercurrent exchange
system. Schmidt-Nielsen & O'Dell (1961) found that the relative medullary thickness
in various mammalian species varied directly with the ability to produce hypertonic
urine. The minimum value was found in beavers (1 3), the maximum in the water
M. A. ABDALLA AND 0. ABDALLA
48
conserving African rodent Psammomys obessus. In this study the relative medullary
thickness of the kidney of the camel was about 7-89. This value is very near to that
of the kangaroo rat (8 5) as reported by Schmidt-Nielsen & O'Dell (1961). Further-
more, sections taken from the inner medulla of the kidney of the camel showed that,
in addition to vasa recta, this part was occupied mainly by thin segments of loops
of Henle and collecting tubules. This indicated that there were many nephrons with
long loops - a requisite for the production of hypertonic urine (Schmidt-Nielsen,
1964). However, Tisher (1971) and Tisher, Schrier & McNeil (1972) have shown that
rhesus and macaque monkeys produce concentrated urine in the absence of a well
developed inner medulla with long loops of Henle.
The kangaroo rat produces highly concentrated urine, and Sperber (1944) found
that it had a medullary to cortical thickness ratio of 5: 1. In the camel in the present
investigation this ratio was about 4: 1. At the other end of the scale, Pfeiffer et al.
(1960) stated that the ratio was about unity in Aplodontia (a primitive rodent which
produces dilute urine).
As suggested by Dunnill & Halley (1973), the ratio of the volume of cortex to
medulla may be of greater functional significance. They found that in man it ranged
from 1-68 in the newly born to 2-59 in the adult. In the adult camel the value was
only 1-3. Age differences have not been investigated here, but Lewis & Alving (1938)
have shown that in man the ability of the kidney to concentrate urine decreases with
age.
The second feature concerns the architecture of the renal pelvis and its relation to
the medulla. In this connexion Pfeiffer (1968) reported that urea could be recycled
from the pelvic urine in species in which the renal pelvis is thrown into folds called
' specialized fornices'. The presence of these folds affords a close association between
the pelvic urine and the medullary tissue, thereby facilitating the recycling of urea
with consequent building up of the osmotic concentration in the medulla. In a
previous study (Abdalla, 1973) the renal pelvis of the camel was found to form
numerous 'specialized fornices' which were closely related to the renal pyramids.
Therefore, in accordance with the theory advanced by Pfeiffer (1968), the ability of
the kidney of the camel to produce concentrated urine is due in part at least to the
special morphology of the renal pelvis and medulla.
The third feature concerns the cortical tubules. Darmady, Offer, Prince & Fay
(1963) stated that the proximal tubule is responsible for the reabsorption of 7ths of
the water entering the glomerulus. In the kidney of the camel the cortical tubules
occupied about 76-12 + 2 8 00 by volume of the cortex, with an absolute volume of
about 335-5 cm3 and a mean surface area of about 9 46 + 1-7 M2. In the human kidney
the cortical tubular surface area varies from 0-8 m2 at birth to a mean value of
8-7 + 2-3 m2 in those over the age of 16 years (Dunnill & Halley, 1973).
The number of glomeruli in the kidney does not seem to have a direct influence on
the ability to produce concentrated urine. The values for the various mammalian
species have been listed by Smith (1951). In the kangaroo rat there are 18840
glomeruli in each kidney. Munkacsi (1964) estimated the number to be about
160000 in the kidney of the African jerboa. The latter species also produces highly
hypertonic urine. In the camel the mean glomerular number in one kidney was about
3.6 + 0.12 x 106. This compares well with a value of about 3 9 x 106 for the ox (Smith,
1951); and yet the ox is not noted for the production of hypertonic urine!
In view of the previous investigations on renal anatomy and physiology, and the
present findings, it is concluded that the anatomical requisites for the production of
Morphometry of the camel's kidney
49
concentrated urine are to be found in the kidney of the camel. However, the urineconcentrating role of antidiuretic hormones, well established in some other mammals,
remains to be investigated in the camel.
SUMMARY
Morphometric analysis of the kidney of the camel was carried out on gross slices
and histological sections using standard morphometric methods. The renal cortex
occupied about 50 % by volume of the kidney, and the ratio of the thickness of the
medulla to that of the cortex was about 4: 1. The relative thickness of the medulla
was about 7-89. This parameter is an indicator of the lengths of the loops of Henle
and vasa recta, and, according to the countercurrent theory, is consequently an
indicator of the ability of the kidney to concentrate urine. In each kidney the
volume and surface area of the cortical tubules and the number of glomeruli were
determined and compared with these parameters in some other mammals. In
addition the architectures of the renal pelvis and medulla and their significance in
relation to the excretion of hypertonic urine were discussed. It was concluded that
the kidney of the camel possesses the anatomical requisites for the production of
hypertonic urine.
REFERENCES
ABDALLA, M. A. (1973). Anatomical study of the urinary system of the camel (Camelus dromedarius).
M.V.Sc. Thesis, University of Khartoum.
BERLINER, R. W. & BENNETT, C. M. (1967). Concentration of urine in the mammalian kidney. American
Journal of Medicine 42, 777-789.
CHAUVEAU, A. (1891). Comparative Anatomy of Domestic Animals. New York: W. R. J. Atkins.
DARMADY, E. M., OFFER, J., PRINCE, J. & FAY, S. (1963). The proximal convoluted tubule in the renal
handling of water. Proceedings of the International Congress of Nephrology, pp. 461-462. New York:
Czechoslovak Academy of Sciences and Excerpta Medica Foundation.
DROANDI, 1. (1936). II Camello: Storia naturale-anatomia, fiziologia - zootecnica, patologia. Firenze:
Instituto Agricolo Coloniale Italiano.
DUNNILL, N. S. (1968). Quantitative methods in histology. In Recent Advances in Clinical Pathology,
series V (ed. S. C. Dyke), pp. 401-416. London: Churchill.
DUNNILL, M. S. & HALLEY, W. (1973). Some observations on the quantitative anatomy of the kidney.
Journal of Pathology 110, 113-121.
GoTrscHALK, C. W. & MYLLE, M. (1959). Micropuncture studies of the mammalian urinary concentrating
mechanism: evidence for the countercurrent hypothesis. American Journal of Physiology 196, 927-936.
HARGITAY, B. & KUHN, W. (1951). Das Multiplikationsprinzip als Grundlage der Hamkonzentrierung
in der Niere. Zeitschrift fur Elektrochemie 55, 539-558.
HENNIG, A. (1956). Bestimmung der Oberflache beliebig geformter Korper mit besonderer Anwendung
auf Korperhaufen im mikroskopischen Bereich. Mikroskopie 11, 1-20.
JOSEPH, T. (1969). Das Nierbecken des Dromedars. Zeitschrift fur Anatomie und Entwicklungsgeschichte
128, 235-242.
LAMDIN, E. (1959). Mechanism of urinary concentration and dilution. Archives of Internal Medicine 103,
644671.
LEESE, A. S. (1927). A Treatise on the One-humped Camel. Stamford: Hayens and Sons.
LESBRE, F. K. (1906). Recherches Anatomique sur les Camelides. Paris: J. B. Bailliere et Fils.
LEWIS, W. H. & ALVING, A. S. (1938). Changes with age in the renal function in adult men. American
Journal of Physiology 123, 500-51 1.
MARSH, D. J. (1971). Osmotic concentration and dilution of the urine. In The Kidney, vol. 3 (ed. C.
Rouiller & A. F. Muller), pp. 71-126. New York: Academic Press.
MUNKACSI, I. (1964). The vascular and tubular structure of the mammalian kidney in relation to water
conservation. Ph.D. Thesis, University of Khartoum.
PFEIFFER, E. W. (1968). Comparative anatomical observations of the mammalian renal pelvis and
medulla. Journal of Anatomy 102, 321-331.
PFEIFFER, E. W., NUNGESSER, W. C., IVERSON, D. A. & WALLERIUS, J. F. (1960). The renal anatomy of
the primitive rodent Aplodontia rufa, and a consideration of its functional significance. Anatomical
Record 137, 227-235.
4
ANA
129
50
M. A. ABDALLA AND 0. ABDALLA
SCHERLE, W. (1970). A simple method for volumetry of organs in quantitative stereology. Mikroskopie 26,
57-60.
SCHMIDT-NIELSEN, B. (1958). Urea excretion in mammals. Physiological Reviews 38, 139-168.
SCHMIDT-NIELSEN, B. (1964). Organ systems in adaptation: The excretory system. In Handbook of
Physiology, ch. 13 (ed. D. B. Dill, E. F. Adolf & C. G. Wilber). Washington D.C.: American Physiological Society.
SCHMIDT-NIELSEN, B. & O'DELL, R. (1961). Structure and concentrating mechanism in the mammalian
kidney. American Journal of Physiology 200, 1119-1124.
SCHMIDT-NIELSEN, K. S. (1964). Desert Animals. Physiological Problems of Heat and Water. Oxford:
Clarendon Press.
SMITH, H. W. (1951). The Kidney: Structure and Function in Health and Disease, p. 570. New York:
Oxford University Press.
SPERBER, I. (1944). Studies on the mammalian kidney. Zoologiska Bidrag fran Uppsala 22, 249-432.
TAYEB, M. A. F. (1948). Urinary system of the camel. Journal of the American Veterinary Medical
Association 113, 568-572.
TISHER, C. C. (1971). Relationship between renal structure and concentrating ability in the rhesus
monkey. American Journal of Physiology 220, 1100-1106.
TISHER, C. C., SCHRIER, R. W. & McNEIL, J. S. (1972). Nature of urine concentrating mechanism in the
macaque monkey. American Journal of Physiology 223, 1128-1137.
TOMKEIEFF, S. I. (1945). Linear intercepts, areas and volumes. Nature 155, 24.
VIMTRUP, BJ. & SCHMIDT-NIELSEN, B. (1952). The histology of the kidney of the Kangaroo rats.
Anatomical Record 114, 515-528.
WEIBEL, E. R. (1963 a). Principles and methods for the morphometric study of the lung and other organs.
Laboratory Investigation 12, 131-155.
WEIBEL, E. R. (1963 b). Morphometry of the Human Lung. Berlin: Springer Verlag.
WEIBEL, E. R. & GOMEZ, D. M. (1962). A principle for counting tissue structures on random sections.
Journal of Applied Physiology 17, 343-348.
WIRZ, H. (1954). The production of hypertonic urine by the mammalian kidney. In The Kidney, Ciba
Foundation Symposium, pp. 38-49. Boston: Little, Brown and Co.
WIRZ. H. & DIRIX, R. (1973). Urinary concentration and dilution. In Handbook ofPhysiology, section 8
(ed. J. Orloff, R. W. Berliner & S. R. Geiger). Washington D.C.: American Physiological Society.