2. Umbilical cord

#### 2.1. Structure

The umbilical cord is a structure discarded after the birth and the transplant of their cells may present less risks of causing reactions, resulting immune reactions, resulting in minimum for the recipient of its cells [4]. This structure has amniotic and allantoic segments. The amniotic segment of the umbilical cord contains two arteries and a vein that arborize into the amnion. These segments continue as multiple vessels in the allantoic segment of the cord with mainly two arteries and two veins with branches (Figure 1) [6]. The urachus courses within the cord from the fetus and empties into the allantoic cavity [6].

The umbilical cord is a unique mammalian fetal attachment and was attached to the center of the placental disk [7, 8]. This structure plays an important role in the transport of maternal nutrients for developing of fetus during gestation [1]. The umbilical cord shows distinct types of composition with respect to the number of blood vessels. There are many morphological changes that appear at the birth into local anatomical structures around the umbilical cord form a complex device to help the organism to severe relation with the placenta. The relation between anatomical structures that form the umbilical cord arrows the morphological support as basis of contraction to eliminate remnants that was inside the abdominal cavity [1, 6].

As has already been mentioned, this structure has a main function of making the connection between the fetus and placenta, ensuring its viability mainly during the later stages of pregnancy [9]. In relation to the umbilical vessels, these are not supplied by vasa vasorum and thus

The umbilical cord was originated from the embryonic stem which connects the bladder of both yolk sac and amniotic. This is discarded after birth in all species of mammals [2]. The umbilical cord forms a connection between placenta and the fetus. This structure is responsible for exchange of nutrients during the gestation. The main characteristic that umbilical cord shows is a specific gross morphology of vein and arteries surrounded of mucous connective tissue. It is known that fetus-mother nutrients exchange is very delicate and difficult to maintain; however, many morphological and functional alterations may produce changes in

In relation to the hematopoietic cells, these have been widely studied functionally, molecularly and structurally, but there are few studies about ultrastructural characterization [3]. The use of stem cells obtained from umbilical cord have originated a lot of expectative for use it in cell therapy and regeneration of organs [4]. Furthermore, it is known that the umbilical cord cells

The scarcity of bibliographic information about studies of optical microscopy of the umbilical cord in mammals and lack researches about these topics in mammalian species have motivated to execution of this type of reviews that reveal main characteristics in relation to the histology of umbilical cord and comparative aspects between different species of mammals of interest.

The umbilical cord is a structure discarded after the birth and the transplant of their cells may present less risks of causing reactions, resulting immune reactions, resulting in minimum for the recipient of its cells [4]. This structure has amniotic and allantoic segments. The amniotic segment of the umbilical cord contains two arteries and a vein that arborize into the amnion. These segments continue as multiple vessels in the allantoic segment of the cord with mainly two arteries and two veins with branches (Figure 1) [6]. The urachus courses within the cord

The umbilical cord is a unique mammalian fetal attachment and was attached to the center of the placental disk [7, 8]. This structure plays an important role in the transport of maternal nutrients for developing of fetus during gestation [1]. The umbilical cord shows distinct types of composition with respect to the number of blood vessels. There are many morphological changes that appear at the birth into local anatomical structures around the umbilical cord form a complex device to help the organism to severe relation with the placenta. The relation between anatomical structures that form the umbilical cord arrows the morphological support as basis of contraction to eliminate remnants that was inside the abdominal cavity [1, 6].

As has already been mentioned, this structure has a main function of making the connection between the fetus and placenta, ensuring its viability mainly during the later stages of pregnancy [9]. In relation to the umbilical vessels, these are not supplied by vasa vasorum and thus

this mechanism of exchange easily.

2. Umbilical cord

2.1. Structure

48 Histology

have been studied only in preclinical approaches [5].

from the fetus and empties into the allantoic cavity [6].

Figure 1. Photograph of umbilical cord of alpaca (Vicugna pacos) showing two umbilical veins (V) and umbilical arteries (a). Next to the umbilical arteries is located allantoid duct (AD). (adapted from barrios-Arpi et al. 2017. Histological characterization of umbilical cord in alpaca (Vicugna pacos).

depend on their oxygen supply making them more vulnerable to changes originated by hemodynamic disorders and similar conditions [10].

This structure is coated by amniotic epithelium (simple squamous epithelium) and the conjunctive layer is adhered closely to the fundamental substance of the umbilical cord majority known as fetal mesenchyme, which is constituted of mesenchymal connective tissue with stellate cells and amorphous ground substance which contains abundant glycogen. This gelatinous composition also called Wharton's jelly or mucous connective tissue has been of great interest and potential impact due to research about tissue repair and differentiation [10]. However, many of the investigations have not been able to continue due to the lack of an animal model that can be used in the preclinical studies [11]. This mucous connective tissue (Wharton's jelly) is an active metabolically tissue involved in fluid exchange between umbilical vessels and amniotic fluid [12].

In the majority of domestic species, two arteries and two veins wound spirally being immersed in a mucous connective tissue appears [13, 14]; however, it is known that in some species, appear the formation of anastomosis of arteries in middle third and proximal to the maternal part of the placenta appears [15].

There are important changes evidenced in the structure of umbilical cord in different animal species. It is indicated that from the beginning, vessels of umbilical cord are represented by two umbilical veins and arteries in species such as bovines and small ruminants [16], zebucrossed bovines [17], buffaloes [18–20], pigs [21], African lions and gazelles [22], and Bactrian camels and dromedaries [23, 24] (Figure 2); however, it is known that in some species the disintegration of right umbilical vein appears without have a strong explanation about this feature [25] (Figure 3). Among these species are carnivores, horses, guinea pigs, nutrias, chinchillas, cavies and rock cavies [26–32].

Finally, as the stages of gestation, the tunica adventitia is becoming thicker in relationship to the tunica intima in both arteries and veins [23].

There are some characteristics that differ between lumens of umbilical arteries in different mammalian species. In the majority of mammals, umbilical arteries show a very large lumen and irregular shape. In some species such as buffaloes, bovines and zebu cows, the umbilical arteries show a lumen of star-shaped lumen [17, 18, 34–36]; however, in species as South American Camelids, the animals present a lumen of slightly star-shaped [37]. In mammals, the umbilical artery is constituted by tunicas intima, media and external/adventitia (Figure 4).

Histology of Umbilical Cord in Mammals http://dx.doi.org/10.5772/intechopen.80766 51

The intima layer consists of elongated endothelium to the long axis of the blood vessel. The endothelium of tunica intima corresponds to the thinnest layer comprised of simple squamous

Figure 4. Umbilical artery, light microscopy, H-E stain. The tunica intima is constituted by endothelium and a small endothelial space. The tunica media is formed mainly by smooth muscle and has double size of tunica adventitia. The abundant collagen and elastic fibers of the tunica adventitia contrasts with muscular tissue and collagen fibers of the

2.2.1. Intima

tunica media. 40 x.

Figure 2. Schematic representation of structure of umbilical cord in cattle, sheep, goat, buffalo, alpaca, canine and feline showing two arteries and two veins. Furthermore, this figure shows the localization of allantoic duct and their relation with blood vessels.

Figure 3. Schematic representation of structure of umbilical cord in horses, pigs and humans showing two arteries and only one vein. Furthermore, this figure shows the localization of allantoic duct and their relation with blood vessels.

#### 2.2. Umbilical artery

At parturition the umbilical arteries retract into the abdomen and close by smooth muscle contraction. This process appears in response to the increased partial pressure of oxygen in the blood [33].

There are some characteristics that differ between lumens of umbilical arteries in different mammalian species. In the majority of mammals, umbilical arteries show a very large lumen and irregular shape. In some species such as buffaloes, bovines and zebu cows, the umbilical arteries show a lumen of star-shaped lumen [17, 18, 34–36]; however, in species as South American Camelids, the animals present a lumen of slightly star-shaped [37]. In mammals, the umbilical artery is constituted by tunicas intima, media and external/adventitia (Figure 4).

#### 2.2.1. Intima

2.2. Umbilical artery

with blood vessels.

50 Histology

blood [33].

At parturition the umbilical arteries retract into the abdomen and close by smooth muscle contraction. This process appears in response to the increased partial pressure of oxygen in the

Figure 3. Schematic representation of structure of umbilical cord in horses, pigs and humans showing two arteries and only one vein. Furthermore, this figure shows the localization of allantoic duct and their relation with blood vessels.

Figure 2. Schematic representation of structure of umbilical cord in cattle, sheep, goat, buffalo, alpaca, canine and feline showing two arteries and two veins. Furthermore, this figure shows the localization of allantoic duct and their relation The intima layer consists of elongated endothelium to the long axis of the blood vessel. The endothelium of tunica intima corresponds to the thinnest layer comprised of simple squamous

Figure 4. Umbilical artery, light microscopy, H-E stain. The tunica intima is constituted by endothelium and a small endothelial space. The tunica media is formed mainly by smooth muscle and has double size of tunica adventitia. The abundant collagen and elastic fibers of the tunica adventitia contrasts with muscular tissue and collagen fibers of the tunica media. 40 x.

epithelium. Most animals, the internal elastic lamina is discontinuous and thin [17, 18, 32–38] with exception of humans and camels which the umbilical arteries possess no internal elastic lamina [10, 23]. In some species as alpacas is possible to observe a very small sub endothelial space which consisted of muscular fibers (non-differentiated muscular cells) cross and cut diagonally (circular disposition), and connective tissue fibers [37] (Figure 5).

adventitia. Finally, the tunica adventitia is constituted by small blood vessels denominated Vasa vasorum, non-myelinated nerves cross-sectional and clearly separated from mucous con-

Histology of Umbilical Cord in Mammals http://dx.doi.org/10.5772/intechopen.80766 53

At parturition the umbilical vein and urachus remain outside the abdomen. In relation to the vein, this structure closes soon by smooth muscle contraction and the urachus shrinks and

Figure 6. Umbilical artery, light microscopy, van Gieson stain. The tunica media is constituted by a double layered muscular of smooth muscle bundles, characterized for inner circular (IC) and outer longitudinal muscular (OL) layers. 100 x.

Figure 7. Umbilical artery, light microscopy, Masson's trichrome stain. The tunica adventitia/external is the most external layer of umbilical cord and is constituted by small blood vessels denominated Vasa vasorum (short arrows). AD: Allantoic

nective tissue (Figure 7) [10, 17, 18, 32, 34–38].

2.3. Umbilical vein

dries within a day [1].

duct. 100 x.

#### 2.2.2. Media

The media layer is located below to the sub endothelial space and the thickness of this layer is double the size of the external/adventitia. The tunica media is constituted by a double layered muscular of smooth muscle bundles, characterized for inner circular muscular layer (collagen and reticular fibers) and outer longitudinal layer (Figure 6). Another characteristic of the media layer is absence of elastic lamina, a presence of reticular fibers and both collagen and elastic fibers and presence of capillaries [10, 17, 32–38].

#### 2.2.3. Adventitia

The tunica adventitia is the most outer layer that forms the umbilical cord wall in all mammals. The tunica adventitia consists of collagen, smooth muscle and elastic fibers. This layer is constituted by smooth muscular fibers which invade part of tunica media and muscle fibers cross-sectional [10, 17, 18, 32, 34–36, 38].

Unlike other mammals, in alpacas, the inner layer is not well defined [37]. In alpacas, the concentration of collagen fibers is increased towards longitudinally oriented muscular fibers and towards periphery. The elastic fibers are abundant between the tunicas media and

Figure 5. Umbilical artery, light microscopy, H-E stain. The tunica intima is comprised of a simple squamous epithelium (E) and a small endothelial space (SE) characterized by elastic and reticular fibers. Note that the internal elastic lamina is not well-defined. TM: Tunica muscular. 400 x.

adventitia. Finally, the tunica adventitia is constituted by small blood vessels denominated Vasa vasorum, non-myelinated nerves cross-sectional and clearly separated from mucous connective tissue (Figure 7) [10, 17, 18, 32, 34–38].

#### 2.3. Umbilical vein

epithelium. Most animals, the internal elastic lamina is discontinuous and thin [17, 18, 32–38] with exception of humans and camels which the umbilical arteries possess no internal elastic lamina [10, 23]. In some species as alpacas is possible to observe a very small sub endothelial space which consisted of muscular fibers (non-differentiated muscular cells) cross and cut

The media layer is located below to the sub endothelial space and the thickness of this layer is double the size of the external/adventitia. The tunica media is constituted by a double layered muscular of smooth muscle bundles, characterized for inner circular muscular layer (collagen and reticular fibers) and outer longitudinal layer (Figure 6). Another characteristic of the media layer is absence of elastic lamina, a presence of reticular fibers and both collagen and

The tunica adventitia is the most outer layer that forms the umbilical cord wall in all mammals. The tunica adventitia consists of collagen, smooth muscle and elastic fibers. This layer is constituted by smooth muscular fibers which invade part of tunica media and muscle fibers

Unlike other mammals, in alpacas, the inner layer is not well defined [37]. In alpacas, the concentration of collagen fibers is increased towards longitudinally oriented muscular fibers and towards periphery. The elastic fibers are abundant between the tunicas media and

Figure 5. Umbilical artery, light microscopy, H-E stain. The tunica intima is comprised of a simple squamous epithelium (E) and a small endothelial space (SE) characterized by elastic and reticular fibers. Note that the internal elastic lamina is

diagonally (circular disposition), and connective tissue fibers [37] (Figure 5).

elastic fibers and presence of capillaries [10, 17, 32–38].

cross-sectional [10, 17, 18, 32, 34–36, 38].

not well-defined. TM: Tunica muscular. 400 x.

2.2.2. Media

52 Histology

2.2.3. Adventitia

At parturition the umbilical vein and urachus remain outside the abdomen. In relation to the vein, this structure closes soon by smooth muscle contraction and the urachus shrinks and dries within a day [1].

Figure 6. Umbilical artery, light microscopy, van Gieson stain. The tunica media is constituted by a double layered muscular of smooth muscle bundles, characterized for inner circular (IC) and outer longitudinal muscular (OL) layers. 100 x.

Figure 7. Umbilical artery, light microscopy, Masson's trichrome stain. The tunica adventitia/external is the most external layer of umbilical cord and is constituted by small blood vessels denominated Vasa vasorum (short arrows). AD: Allantoic duct. 100 x.

Similar to the umbilical artery, there are some characteristics that differ between lumen of umbilical arteries in different mammalian species. In some mammals such as buffaloes, carnivores, horses, guinea pigs, nutrias, chinchillas, cavies and rock cavies, umbilical vein shows a lumen in elliptic shape with wall thinner than umbilical artery [26–32]; however, in species as South American Camelids and horses, the umbilical vein displays a lumen obliterated into starshaped [29, 37, 38]. In mammals, umbilical vein is constituted of tunicas intima, media and external/adventitia (Figure 8).

sub endothelial space which consist of muscular fibers (non-differentiated muscular cells) cross and cut diagonally (circular disposition), and connective tissue fibers [37] (Figure 9).

Histology of Umbilical Cord in Mammals http://dx.doi.org/10.5772/intechopen.80766 55

The media layer is located below to the sub endothelial space and the thickness of this layer is variable in relation to the external/adventitia in different mammalian species. Most animals display a tunica media which is smaller than tunica adventitia including species such as buffaloes, carnivores, horses, guinea pigs, nutrias, chinchillas, cavies and rock cavies [26–32]. Additionally, the South American camelids present a tunica media which is larger in dimension than the tunica adventitia [37], however, the cause of this morphologic evidence is not

This tunica is constituted by a double layered muscular of smooth muscle bundles, characterized for inner circular muscular layer (collagen and reticular fibers) and outer longitudinal layer (Figure 10). The tunica media comprises the inner circular and outer longitudinal muscular layers, with an absence of outer elastic lamina and presence of reticular fibers. Also, it presented a small amount of collagen and elastic fibers [10, 17, 23, 34–38]. Furthermore, in alpacas is known that smooth, cross-sectional muscle fibers invade part of the tunic adventitia consisting in muscular fibers cross-transverse, abundant collagen fibers, collagen and muscu-

Figure 9. Umbilical vein, light microscopy, H-E stain. The tunica intima is comprised of a simple squamous epithelium

(E) and a small endothelial space (SE). TM: Tunica muscular. 400 x.

2.3.2. Media

known.

lar fibers arranged longitudinally [37].

#### 2.3.1. Intima

The tunica intima consists of endothelium but lack of external elastic lamina with less organization line compared to the umbilical artery. However, in general, endothelium showed similar characteristics as observed in the umbilical artery.

There are several studies that confirm this conformation of the tunica intima which is thin and lack internal elastic lamina [10, 17, 23, 34–38]. Similar to alpacas, is possible to observe a small

Figure 8. Umbilical vein, light microscopy, H-E stain. The tunica intima is constituted by endothelium and a very small endothelial space. The tunica media is formed mainly by smooth muscle and has a thickness similar to the tunica adventitia. The abundant collagen and elastic fibers of the tunica adventitia is slightly invaded by muscular tissue and collagen fibers of the tunica media. 40 x.

sub endothelial space which consist of muscular fibers (non-differentiated muscular cells) cross and cut diagonally (circular disposition), and connective tissue fibers [37] (Figure 9).

#### 2.3.2. Media

Similar to the umbilical artery, there are some characteristics that differ between lumen of umbilical arteries in different mammalian species. In some mammals such as buffaloes, carnivores, horses, guinea pigs, nutrias, chinchillas, cavies and rock cavies, umbilical vein shows a lumen in elliptic shape with wall thinner than umbilical artery [26–32]; however, in species as South American Camelids and horses, the umbilical vein displays a lumen obliterated into starshaped [29, 37, 38]. In mammals, umbilical vein is constituted of tunicas intima, media and

The tunica intima consists of endothelium but lack of external elastic lamina with less organization line compared to the umbilical artery. However, in general, endothelium showed similar

There are several studies that confirm this conformation of the tunica intima which is thin and lack internal elastic lamina [10, 17, 23, 34–38]. Similar to alpacas, is possible to observe a small

Figure 8. Umbilical vein, light microscopy, H-E stain. The tunica intima is constituted by endothelium and a very small endothelial space. The tunica media is formed mainly by smooth muscle and has a thickness similar to the tunica adventitia. The abundant collagen and elastic fibers of the tunica adventitia is slightly invaded by muscular tissue and

external/adventitia (Figure 8).

collagen fibers of the tunica media. 40 x.

characteristics as observed in the umbilical artery.

2.3.1. Intima

54 Histology

The media layer is located below to the sub endothelial space and the thickness of this layer is variable in relation to the external/adventitia in different mammalian species. Most animals display a tunica media which is smaller than tunica adventitia including species such as buffaloes, carnivores, horses, guinea pigs, nutrias, chinchillas, cavies and rock cavies [26–32]. Additionally, the South American camelids present a tunica media which is larger in dimension than the tunica adventitia [37], however, the cause of this morphologic evidence is not known.

This tunica is constituted by a double layered muscular of smooth muscle bundles, characterized for inner circular muscular layer (collagen and reticular fibers) and outer longitudinal layer (Figure 10). The tunica media comprises the inner circular and outer longitudinal muscular layers, with an absence of outer elastic lamina and presence of reticular fibers. Also, it presented a small amount of collagen and elastic fibers [10, 17, 23, 34–38]. Furthermore, in alpacas is known that smooth, cross-sectional muscle fibers invade part of the tunic adventitia consisting in muscular fibers cross-transverse, abundant collagen fibers, collagen and muscular fibers arranged longitudinally [37].

Figure 9. Umbilical vein, light microscopy, H-E stain. The tunica intima is comprised of a simple squamous epithelium (E) and a small endothelial space (SE). TM: Tunica muscular. 400 x.

2.4. Mucous connective tissue (Wharton jelly)

and eosinophilic dense and finely granular cytoplasm [37].

features to lymphoid cells [37].

2.5. Allantoic duct

(Figure 13) [37].

32, 34–38].

The mucous connective tissue surrounding the umbilical artery is almost the same in thickness and share histological features with that of umbilical vein region except that smaller blood vessels and blood capillaries are more numerous towards periphery (Figure 12). Moreover, small nerve bundles cut in different profiles (and some structures resembling to ganglion) have been also observed towards periphery of the mucous connective tissue [10, 17, 18, 32, 34–38]. In alpacas has been observed some larger cells that had triangular or star-shaped with less basophilic nuclei and strongly eosinophilic cytoplasm, probably mesenchymal stem cells. A few round cells with differently stained nuclei were also observed which showed similar

Histology of Umbilical Cord in Mammals http://dx.doi.org/10.5772/intechopen.80766 57

The allantoic duct present irregular lumen and is comprised by simple cuboidal to columnar epithelium [10, 17, 18, 32, 34–38]. In alpacas has been recognized some characteristics such as the less basophilic nuclei of varying shapes that are oriented in mid portion of the epithelium,

Most animals display the outer layer consisting of band of smooth muscle bundles arranged in

In alpacas, this structure presents abundant fine blood vessels between arterioles, venules and capillaries which have been reduced to adjacent portion of the mucous connective tissue

Umbilical cord is covered by simple squamous epithelium in all mammalian species [10, 17, 18,

Figure 12. Mucous connective tissue, light microscopy, Masson's trichrome stain. In the most periphery part is observed

great number of blood vessels that alternate with abundant reticular, elastic and collagen fibers. 400 x.

different directions; oblique, circular and longitudinal [10, 17, 18, 32, 34–38].

Figure 10. Umbilical vein, light microscopy, H-E stain. The tunica media is constituted by abundant muscular fibers separated by elastic and fibrous tissue. 400 x.

#### 2.3.3. Adventitia

In the majority of mammalian species, the tunica adventitia is larger than the tunica media [26– 32] and this layer consists of collagen and elastic fibers, and small blood vessels called Vasa vasorum (Figure 11). Additionally, the tunica adventitia is slightly smaller than the tunica media in alpacas [37]. Generally, this tunica not is clearly separated of the mucous connective tissue also called Wharton's Jelly, however, is species as alpacas, it is possible observe a clear separation among both structures [37]. This tunica displays variations in their thickness where most mammalian species present a great number of transversal nerves in all thickness fibers [10, 17, 23, 34–38].

Figure 11. Umbilical vein, light microscopy, Masson's trichrome stain. The tunica adventitia/external is constituted by small blood vessels denominated Vasa vasorum. Note the presence abundant collagen and elastic fibers. 400 x.

#### 2.4. Mucous connective tissue (Wharton jelly)

The mucous connective tissue surrounding the umbilical artery is almost the same in thickness and share histological features with that of umbilical vein region except that smaller blood vessels and blood capillaries are more numerous towards periphery (Figure 12). Moreover, small nerve bundles cut in different profiles (and some structures resembling to ganglion) have been also observed towards periphery of the mucous connective tissue [10, 17, 18, 32, 34–38].

In alpacas has been observed some larger cells that had triangular or star-shaped with less basophilic nuclei and strongly eosinophilic cytoplasm, probably mesenchymal stem cells. A few round cells with differently stained nuclei were also observed which showed similar features to lymphoid cells [37].

#### 2.5. Allantoic duct

2.3.3. Adventitia

56 Histology

separated by elastic and fibrous tissue. 400 x.

[10, 17, 23, 34–38].

In the majority of mammalian species, the tunica adventitia is larger than the tunica media [26– 32] and this layer consists of collagen and elastic fibers, and small blood vessels called Vasa vasorum (Figure 11). Additionally, the tunica adventitia is slightly smaller than the tunica media in alpacas [37]. Generally, this tunica not is clearly separated of the mucous connective tissue also called Wharton's Jelly, however, is species as alpacas, it is possible observe a clear separation among both structures [37]. This tunica displays variations in their thickness where most mammalian species present a great number of transversal nerves in all thickness fibers

Figure 11. Umbilical vein, light microscopy, Masson's trichrome stain. The tunica adventitia/external is constituted by

small blood vessels denominated Vasa vasorum. Note the presence abundant collagen and elastic fibers. 400 x.

Figure 10. Umbilical vein, light microscopy, H-E stain. The tunica media is constituted by abundant muscular fibers

The allantoic duct present irregular lumen and is comprised by simple cuboidal to columnar epithelium [10, 17, 18, 32, 34–38]. In alpacas has been recognized some characteristics such as the less basophilic nuclei of varying shapes that are oriented in mid portion of the epithelium, and eosinophilic dense and finely granular cytoplasm [37].

Most animals display the outer layer consisting of band of smooth muscle bundles arranged in different directions; oblique, circular and longitudinal [10, 17, 18, 32, 34–38].

In alpacas, this structure presents abundant fine blood vessels between arterioles, venules and capillaries which have been reduced to adjacent portion of the mucous connective tissue (Figure 13) [37].

Umbilical cord is covered by simple squamous epithelium in all mammalian species [10, 17, 18, 32, 34–38].

Figure 12. Mucous connective tissue, light microscopy, Masson's trichrome stain. In the most periphery part is observed great number of blood vessels that alternate with abundant reticular, elastic and collagen fibers. 400 x.

References

9-55

978-3-319-62383-2

25-35. DOI: 10.1590/S1516-84842009005000038

29:686-693. DOI: 10.1016/S0301-472X(01)00638-5

Blackwell; 2012. p. 241. DOI: 10.1002/9781119949053

395-402. DOI: 10.1089/scd.2008.0314

DOI: 10.1007/s10529-011-0727-0

469-473. DOI: 10.1002/j.1879-3479.1977.tb00735.x

[thesis]. São Paulo: Universidade de São Paulo; 1995

2001. 2001;42(4):699-708. DOI: 10.3109/10428190109099332

[1] Fahmy M. Umbilicus and Umbilical Cord. 1st. ed. Springer; 2018. p. 264. DOI: 10.1007/

Histology of Umbilical Cord in Mammals http://dx.doi.org/10.5772/intechopen.80766 59

[2] Bydlowski OP, Debes AA, Maselli LMF, Janz FL. Características biológicas das célulastroncos mesenquimais. Revista Brasileira de Hematologia e Hemoterapia. 2009;31(Supl. 1):

[3] Deliliers LG et al. Ultrastructural features of CD 34+ hematopoetic progenitor cells from bone marrow, peripheral blood and umbilical cord blood. Leukemia and Lymphoma.

[4] Zucconi E, Vieira NM, Bueno DF. Mesenchymal stem cells derived from canine umbilical cord vein—A novel source for cell therapy studies. Stem Cells and Development. 2019;19:

[5] Niemeyer GP, Hudson J, Bridgman R, Spano J, Richard AN, Lathrop CD. Isolation and characterization of canine hematopoetic progenitor cells. Experimental Hematology. 2001;

[6] Bradley LN. Diagnosis of Abortion and Neonatal Loss in Animals. 4th ed. Wiley-

[7] Blanchette H. The rising cesarean delivery rate in America: What are the consequences? Obstetrics and Gynecology. 2011;118:687-690. DOI: 10.1097/AOG.0b013e318227b8d9

[8] Favaron et al. Placentation in Sigmodontinae: A rodent taxon native to South America. Reproductive Biology and Endocrinology. 2011, 2011;9(55):1-14. DOI: 10.1186/1477-7827-

[9] Caughey AB et al. Maternal and neonatal outcomes of elective induction of labor. Evidence Report/Technology Assessment. 2009;176:247-257. DOI: 10.1007/s00404-017-4354-4

[10] Barnwal M, Rathi SK, Chhabra S, Nanda S. Histomorphometry of umbilical cord and its vessels in pre eclampsia as compared to normal pregnancies. Nepal Journal of Obstetrics

[11] Sousa AF, Andrade PZ, Pirzgalska RM, Galhoz TM, Azevedo AM. A novel method for human hematopoietic stem/progenitor cell isolation from umbilical cord blood based on immunoaffinity aqueous two-phase partitioning. Biotechnology Letters. 2011;33:2373-2377.

[12] Tavares-Fortuna LF, Lourdes-Pratas M. Coarctation of the umbilical cord: A cause of intrauterine fetal death. International Journal of Gynaecology and Obstetrics. 1978;15(5):

[13] Ribeiro AACM. Pesquisa anatômica sobre o funículo umbilical em bovinos azebuados

and Gynaecology. 2012;7(1):28-32. DOI: 10.3126/njog.v7i1.8832

Figure 13. Allantoic duct, light microscopy, Masson's trichrome stain. Note the irregular shape lumen with plane epithelium and presence of abundant small blood vessels located near to this structure immersed in abundant connective tissue. 100 x.

## Conclusions

Histology plays an important role in the characterization of umbilical cord in mammals. There are many structures which enable to be recognized through of this method and furthermore, allow compares and differentiate among different animal species. According with the presence of certain structures and characteristics that comprise the wall of arteries and veins is possible a well-characterized description of the umbilical cord in mammals.

#### Acknowledgements

The present chapter contains several details obtained of article entitled "Histological characterization of umbilical in alpaca (Vicugna pacos)" which was published by Jose Luis Rodríguez Gutierrez, Bernardo Lopez Torres and me as corresponding author and main author. As author, I want to recognize the contribution of these authors for presentation of this book chapter.

## Author details

Luis Manuel Barrios Arpi

Address all correspondence to: lbarriosa@unmsm.edu.pe

Animal Physiology Laboratory, San Marcos University, Lima, Peru
