Turkish Journal of Veterinary & Animal Sciences 
Volume 41 Number 3 Article 10 
1-1-2017 
Morphological and histological structure of the interdigital gland 
in Awassi sheep (Ovis aries) 
BESTAMİ YILMAZ 
RAHŞAN YILMAZ 
İSMAİL DEMİRCİOĞLU 
İLKER ARICAN 
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Recommended Citation 
YILMAZ, BESTAMİ; YILMAZ, RAHŞAN; DEMİRCİOĞLU, İSMAİL; and ARICAN, İLKER (2017) "Morphological 
and histological structure of the interdigital gland in Awassi sheep (Ovis aries)," Turkish Journal of 
Veterinary & Animal Sciences: Vol. 41: No. 3, Article 10. https://doi.org/10.3906/vet-1605-8 
Available at: https://journals.tubitak.gov.tr/veterinary/vol41/iss3/10 
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Turkish Journal of Veterinary and Animal Sciences Turk J Vet Anim Sci
(2017) 41: 380-386
http://journals.tubitak.gov.tr/veterinary/ © TÜBİTAK
Research Article doi:10.3906/vet-1605-8
Morphological and histological structure of the interdigital gland in
 Awassi sheep (Ovis aries)
Bestami YILMAZ1,*, Rahşan YILMAZ2, İsmail DEMİRCİOĞLU1, İlker ARICAN3
1Department of Anatomy, Faculty of Veterinary Medicine, Harran University, Şanlıurfa, Turkey
2Department of Pathology, Faculty of Veterinary Medicine, Harran University, Şanlıurfa, Turkey
3Department of Anatomy, Faculty of Veterinary Medicine, Uludağ University, Bursa, Turkey
Received: 03.05.2016              Accepted/Published Online: 11.04.2017              Final Version: 12.06.2017
Abstract: We investigated the effects of sex and breeding season on the morphological and histological structures of the interdigital 
gland in Awassi sheep (Ovis aries). Forelimbs and hind limbs were collected from 10 males and 10 females in both the breeding (June–
July) and nonbreeding (November–December) seasons. The interdigital glands were located between the first and second phalanxes 
and were present on all of the limbs. The mean weight of the gland was 1.03 ± 0.03 g. Mean body length, body thickness, duct length, 
duct diameter, and duct opening diameter were 17.42 ± 0.23 mm, 8.12 ± 0.08 mm, 26.81 ± 0.31 mm, 4.65 ± 0.05 mm, and 3.53 ± 0.03 
mm, respectively. All of the parameters had higher values in males than in females. In the breeding season, values were generally 
higher than those in the nonbreeding season. Gland secretions were pink and necrotic cell debris was observed in the gland lumen. The 
morphometric and histological data from this study indicate that the structure of the interdigital gland in Awassi sheep is similar to that 
in other sheep breeds. The results also suggest that this gland may play a role in sexual communication in sheep.
Key words: Anatomy, Awassi sheep, breeding, histology, interdigital gland
1. Introduction foreign bodies entering the interdigital gland (4). Its 
Interdigital glands in ruminants are defined as skin incidence among foot diseases in sheep is 1.6% during 
invaginations located in the region between the digits pasture and 25.3% in the corral period (15). 
(1–3). They are specialized skin structures that include all The anatomical position and histological structure 
of the skin layers and have both sebaceous and apocrine of the interdigital gland have been reported in various 
sweat glands (4,5). The prenatal development of the pipe- breeds of sheep (7,12,16), goat (17,18), serow (19), and 
shaped structure is complete by approximately the 90th– roebuck (20). This is the first study on the morphological 
100th day (6). These glands are considered scent glands, and histological structures of the forelimb and hind limb 
and are responsible for sexual communication with the interdigital glands of male and female Awassi sheep (Ovis 
contents being secreted (7–11). Chemical secretions from aries) during and outside of the breeding season.
the gland reportedly play an important role in the social 
and biological behaviors of ruminants, and are also useful 2. Materials and methods
for regional determination (12). The interdigital gland 
contributes to elasticity of the skin in the region where it is 2.1. Sample collection
located, plays a role in protection from ultraviolet rays, and The interdigital gland samples used in the study were 
has fungicidal and bactericidal effects (13). In addition, its collected from Awassi sheep that were slaughtered in 
location and structure contribute to its clinical importance. a private slaughterhouse in Şanlıurfa, Turkey. Samples 
Because of its location, the gland is subject to infections, were taken during both the breeding (June–July) and 
such as interdigital sinusitis, that may be due to poor nonbreeding (November–December) seasons. For each 
hygienic conditions and high humidity levels, particularly season, the forelimbs and hind limbs from 10 males 
in the spring, as well as to mechanical injury by foreign (average body weight: 65 kg; age: 12 months–2 years 
bodies entering the gland (14). In sheep, interdigital old) and 10 females (average body weight: 55 kg; age: 18 
sinusitis frequently occurs due to microorganisms and months–3 years old) were collected.
* Correspondence: byilmaz@harran.edu.tr
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2.2. Radiography 2.5. Statistical analysis
Gland secretions were evacuated by massaging the feet The effects of sex (male or female) and season (breeding 
in an in situ position. Then the gland sinus was lavaged or nonbreeding) on the morphometric measurements 
using a saline solution with a plastic cannula placed within of the interdigital gland were analyzed using two-way 
the orifice of the excretory duct, after which a contrasting analysis of variance. Differences between morphometric 
agent containing barium sulfate (R-X Suspension 100%, measurements of the glands located on the forelimbs and 
Yenişehir Lab, Turkey) was injected. X-ray images were hind limbs as well as on the right limbs and left limbs were 
taken from both the dorsopalmar/dorsoplantar and tested using an independent t-test. Statistical analyses were 
mediolateral aspects. performed using SPSS version 22. Statistical significance 
was established at P < 0.05.
2.3. Macroanatomic and morphometric examinations
The interdigital gland was dissected from the area between 3. Results
the digits. A precision scale (Vibra HT 224, Shinko Denshi 
Co., Ltd, Japan) was used to weigh the gland. Morphometric 3.1. Radiographic observations
values (body length, duct length, body width, diameters of The interdigital gland was located in the space between the digits at the first and second phalanxes (Figures 1 and 2). 
the duct and opening) from the gland were measured using 
digital calipers (Mitutuyo Corporation, Japan). Images of 3.2. Macroanatomic and morphometric observations 
the gland were taken with a digital camera (Canon EOS The interdigital gland was present in all of the limbs. 
650D). The orifice was located between the medial and lateral 
digits at the level of the anterior part of the proximal 
2.4. Histological techniques interphalangeal joint (Figures 3A and 3B). Hairs were 
Gland tissues were embedded in paraffin according observed dangling from the tip of the orifice. The gland 
to a routine procedure after fixation in a 10% neutral resembled a tobacco pipe, with an orifice at the proximal 
formaldehyde solution. Then 4-µm-thick sections tip of a long and narrow neck, a wide body, and a bend 
were stained with hematoxylin and eosin. Histological connecting the two structures (Figure 3C). The duct of 
examinations were performed using a microscope the gland was oriented in a distopalmar/distoplantar 
(Olympus BX51) equipped with a digital camera (Olympus direction, starting from the orifice to the middle of the 
DP71). medial phalanx. The gland formed a bend by curling up 
Figure 1. Dorsopalmar (A) and mediolateral (B) radiographic appearance of the interdigital 
gland (forelimb).
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Figure 2. Dorsoplantar (A) and mediolateral (B) radiographic appearance of the interdigital 
gland (hind limb).
Figure 3. Cranial (A) and lateral (B and C) appearance of the interdigital gland.
at this level. The body, which formed a large part of the of the gland was 1.03 ± 0.03 g and was higher in males 
gland, reached the distal 1/3 of the proximal phalanx after than in females (P < 0.05), as well as in the breeding season 
the bend. The gland was attached to neighboring tissues compared to the nonbreeding season (P < 0.05) (Table 1). 
by connective tissue. Hairs were observed within both the Mean body length, body width, duct length, duct diameter, 
duct and the body. Morphometric measurements from the and duct opening diameter were 17.42 ± 0.23 mm, 8.12 ± 
interdigital gland are shown in Figure 4. The mean weight 0.08 mm, 26.81 ± 0.31 mm, 4.65 ± 0.05 mm, and 3.53 ± 
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Measurements for gland weight (P < 0.05), body width 
(P < 0.001), duct length (P < 0.001), duct diameter (P < 
0.05), duct opening diameter (P < 0.05), and body length 
were higher in the breeding season than in the nonbreeding 
season. All the morphometric parameters of the gland in 
the forelimb were higher than those in the hind limb (P < 
0.001) (Table 2). No statistically significant differences in the 
measurements of the gland between right and left limbs were 
observed (P > 0.05) (Table 2).
3.3. Histological observations
Microscopic examination of the interdigital gland showed a 
similar structure in the neck and body of the gland, except 
that the body had a larger lumen compared to the neck. The 
lumen of both parts was filled with secretions of the apocrine 
sweat glands and sebaceous glands that were dark pink. 
Indeed, there were keratin debris, fragmented wool fibers, 
and desquamated cells of epithelium within the secretion. 
The secretion in the lumen of the body was more viscous than 
that in the neck. The sinuses of both the neck and body were 
covered by three layers of skin consisting of the epidermis, 
dermis, and a fibrous capsule (Figure 5). The epidermis was 
covered with a multilayered, keratinized, flat epithelium. 
In the dermis, hair follicles were scattered in the loose 
connective tissue with sebaceous and apocrine sweat glands 
and erector pili muscles. The sebaceous glands were located 
Figure 4. The interdigital gland and its parts (lateral appearance). closer to the surface around the hair follicles. Apocrine 
A: duct length, B: duct opening diameter, C: duct diameter, D: sweat glands were located in clusters in the lower part of the 
body length, E: body width. dermis. The apocrine sweat gland epithelium was composed 
of a single row of cubic cells on the basal layer (Figure 6). 
The lumen of the glands was particularly large in samples 
0.03 mm, respectively (Table 1). Males had higher values collected during the breeding season and the presence of 
for gland weight (P < 0.05), body length (P < 0.01), body light pink secretions was noted. The fibrous capsule around 
width (P < 0.01), duct length (P < 0.001), duct diameter (P the gland was composed of a dense connective tissue that 
< 0.001), and duct opening diameter (P < 0.001). included blood vessels, nerves, and fat cells. 
Table 1. The effect of season and sex on the morphometric measurements of the interdigital gland analyzed by two way analysis of 
variance. 
Parameter Variable Gland Body length Body width Duct length Duct iameter Duct opening weight (g) (mm) (mm) (mm) (mm) diameter (mm)
Breeding 1.101 17.601 8.488 27.899 4.761 3.596
Season Nonbreeding 0.967 17.24 7.755 25.723 4.536 3.465
P * n.s. *** *** * *
Male 1.097 18.151 8.394 28.266 4.892 3.738
Sex Female 0.971 16.691 7.849 25.356 4.405 3.324
P * ** ** *** *** ***
Grand mean 1.034 17.421 8.122 26.811 4.648 3.531
SEM 0.031 0.232 0.085 0.312 0.050 0.031
* (P < 0.05); ** (P < 0.01); *** (P < 0.001); n.s.: not significant
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Table 2. The effect of direction and site on the morphometric measurements of the interdigital gland analyzed by t-test (mean ± S.E.M.). 
Parameter Variable Gland Body length Body width Duct length Duct diameter Duct opening weight (g) (mm) (mm) (mm) (mm) diameter (mm)
Fore 1.254 ± 0.050 19.877 ± 0.398 8.919 ± 0.150 29.476 ± 0.586 5.144 ± 0.093 3.947 ± 0.059
Direction Hind 0.814 ± 0.036 14.965 ± 0.266 7.324 ± 0.111 24.146 ± 0.349 4.153 ± 0.054 3.114 ± 0.044
P *** *** *** *** *** ***
Right 1.035 ± 0.050 17.648 ± 0.464 8.270 ± 0.156 26.880 ± 0.650 4.638 ± 0.087 3.538 ± 0.069
Site Left 1.032 ± 0.050 17.194 ± 0.406 7.974 ± 0.160 26.742 ± 0.472 4.659 ± 0.101 3.524 ± 0.070
P n.s. n.s. n.s. n.s. n.s. n.s.
*** (P < 0.001); n.s.: not significant
Figure 5. Microscopic appearance of the interdigital gland, 100×, Figure 6. Microscopic appearance of the apocrine sweat gland, 
H&E. Star: mass in the lumen; thick arrow: keratin layer; e: 400×, H&E. Arrowhead: Apocrine sweat gland; thick arrow: 
epidermis; d: dermis; arrowhead: cluster of apocrine glands; thin excretory duct, thin arrow: capillary, L: the lumen of apocrine 
arrow: sebaceous gland; filled triangle: hair follicle. sweat gland and excretory duct.
4. Discussion with a large pouch. Avdic et al. (14) defined the sections 
This study presents the topographic, morphometric, and of the gland as the fundus, body, and column, whereas 
histologic characteristics of the interdigital gland in Awassi Süzer et al. (7) described the parts of the gland as a blind 
sheep. Many studies have examined the interdigital gland. proximal end with a large body and a long, narrow neck. 
Its absence (17,21) and the existence of a rudimentary Demiraslan et al. (16) described the gland as having four 
gland (18) were reported in goats. It was reported that sections: mouth, excretion duct, bend, and corpus. Our 
the sheep (12,22,23), antelope (24), Japanese serow (5), sagittal view of the interdigital gland showed that it was a 
and fallow deer (23) have the gland in all four limbs, pipe-shaped structure consisting of three parts: a narrow 
whereas it is present only in the hind limbs in the deer neck with an orifice at the proximal tip, a wide body, and a 
(1) and roebuck (20). It is also present in all four limbs bend connecting these two parts.
in Awassi sheep, and is located between the proximal Süzer et al. (7) reported that the weight of the 
and distal interphalangeal joints of the two main digits interdigital sinus in Kivircik sheep was 0.84 g, whereas 
(7,11,12,14,16,17,25). The location of the interdigital gland Abbasi et al. (13) reported that the average weight of the 
in our study was consistent with the literature. gland was 1.16 g in the forelimbs and hind limbs of male 
The shape of the interdigital gland reportedly resembles and female Iranian domestic sheep in both the breeding 
a pipe (7, 16) or sock (19). Awaad et al. (21) reported and nonbreeding periods. The average weight of the gland 
that the interdigital gland consists of a body with a neck, in Awassi sheep (1.03 ± 0.03 g) was higher than that 
whereas Abbasi et al. (13) described it as a narrow channel reported in Kivircik sheep and lower than that reported in 
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Iranian domestic sheep (13). These differences might be males compared to females might be explained by the live 
due to the different body weights of the breeds examined. weight differences between the sexes. Meyer (1) reported 
Demiraslan et al. (16) reported a corpus length of that average gland size and body weight are correlated. 
21.9 mm, corpus width of 4.7 mm, duct length of 26.8 Average body weight of males is higher than that of 
mm, and channel diameter of 2 mm for the interdigital females in Awassi sheep raised in different regions (26). 
gland in Kivircik sheep. Süzer et al. (7) reported a length In accordance with the findings published by Abbasi et 
of 16.74 mm, duct diameter of 4.6 mm, and trunk al. (13), values in the present study were generally higher 
diameter of the body of 6.95 mm in their study on the in the breeding season than in the nonbreeding season. 
forelimb interdigital gland of female Kivircik sheep. In accordance with the results reported by several 
Abbasi (13) observed that the length, width, thickness, researchers (5,13,21) the morphometric parameters 
and duct length of the gland in Iranian domestic sheep were also significantly higher in the forelimbs (P < 
were 15.80, 7.60, 7.71, and 26.06 mm, respectively. Misk 0.001). The wall of the body and neck consisted of the 
and Misk (22) reported a duct length of about 30 mm, epidermis, dermis, and fibrous capsule. The epidermis 
pouch length of 25 mm, and width of 6 mm in sheep. consisted of stratified squamous keratinized epithelium. 
In our study, we found that mean body length, body Sebaceous glands, apocrine sweat glands, hair follicles, 
width, duct length, diameter of the duct, and diameter and erector pili muscles were observed in the dermis. 
of the orifice were 17.42, 8.12, 26.81, 4.65, and 3.53 mm, The sebaceous glands were closer to the surface, around 
respectively. The morphometric measurements obtained the hair follicles. Apocrine sweat glands were located in 
in this study are consistent with those reported by other the lower part of the dermis and were composed of a 
researchers. single layer of cubic cells. The fibrous capsule around the 
In our study, all of the morphometric parameters gland was composed of connective tissue, blood vessels, 
in males had higher values than in females. These nerves, and fat cells. Our histological data are consistent 
findings were in contrast to those reported by Atoji et with findings from previous studies (7,12,13,16,25). 
al. (5) and Awaad et al. (21). This might be attributed to We determined that the morphometric and histologic 
species or breed differences. However, our results were characteristics of the interdigital gland in Awassi sheep 
in accordance with those reported by Abbasi et al. (13), were similar to those of other sheep breeds. Higher 
who compared the interdigital glands of male and female morphometric values were observed during the breeding 
sheep in both the breeding and nonbreeding periods and season compared to the nonbreeding season, and the 
reported that the glands of males in the breeding season lumen of the glands of the forelimbs was larger than that 
had higher values in terms of volume and weight than in of the hind limbs, supporting the hypothesis that the 
the nonbreeding season. The higher values observed in interdigital gland plays a role in sexual communication.
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