Umbilical cord
Overview
In placental mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...

s, the umbilical cord (also called the birth cord or funiculus umbilicalis) is the connecting cord from the developing embryo
Embryo
An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...

 or fetus
Fetus
A fetus is a developing mammal or other viviparous vertebrate after the embryonic stage and before birth.In humans, the fetal stage of prenatal development starts at the beginning of the 11th week in gestational age, which is the 9th week after fertilization.-Etymology and spelling variations:The...

 to the placenta
Placenta
The placenta is an organ that connects the developing fetus to the uterine wall to allow nutrient uptake, waste elimination, and gas exchange via the mother's blood supply. "True" placentas are a defining characteristic of eutherian or "placental" mammals, but are also found in some snakes and...

. During prenatal development, the umbilical cord is physiologically and genetically part of the fetus and (in humans) normally contains two arteries (the umbilical arteries) and one vein
Vein
In the circulatory system, veins are blood vessels that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenated blood to the heart...

 (the umbilical vein
Umbilical vein
The umbilical vein is a vein present during fetal development that carries oxygenated blood from the placenta to the growing fetus.The blood pressure inside the umbilical vein is approximately 20 mmHg.-Development:...

), buried within Wharton's jelly
Wharton's jelly
Wharton's jelly is a gelatinous substance within the umbilical cord, largely made up of mucopolysaccharides . It also contains some fibroblasts and macrophages...

. The umbilical vein supplies the fetus with oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

ated, nutrient
Nutrient
A nutrient is a chemical that an organism needs to live and grow or a substance used in an organism's metabolism which must be taken in from its environment. They are used to build and repair tissues, regulate body processes and are converted to and used as energy...

-rich blood
Blood
Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....

 from the placenta
Placenta
The placenta is an organ that connects the developing fetus to the uterine wall to allow nutrient uptake, waste elimination, and gas exchange via the mother's blood supply. "True" placentas are a defining characteristic of eutherian or "placental" mammals, but are also found in some snakes and...

.
Encyclopedia
In placental mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...

s, the umbilical cord (also called the birth cord or funiculus umbilicalis) is the connecting cord from the developing embryo
Embryo
An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...

 or fetus
Fetus
A fetus is a developing mammal or other viviparous vertebrate after the embryonic stage and before birth.In humans, the fetal stage of prenatal development starts at the beginning of the 11th week in gestational age, which is the 9th week after fertilization.-Etymology and spelling variations:The...

 to the placenta
Placenta
The placenta is an organ that connects the developing fetus to the uterine wall to allow nutrient uptake, waste elimination, and gas exchange via the mother's blood supply. "True" placentas are a defining characteristic of eutherian or "placental" mammals, but are also found in some snakes and...

. During prenatal development, the umbilical cord is physiologically and genetically part of the fetus and (in humans) normally contains two arteries (the umbilical arteries) and one vein
Vein
In the circulatory system, veins are blood vessels that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenated blood to the heart...

 (the umbilical vein
Umbilical vein
The umbilical vein is a vein present during fetal development that carries oxygenated blood from the placenta to the growing fetus.The blood pressure inside the umbilical vein is approximately 20 mmHg.-Development:...

), buried within Wharton's jelly
Wharton's jelly
Wharton's jelly is a gelatinous substance within the umbilical cord, largely made up of mucopolysaccharides . It also contains some fibroblasts and macrophages...

. The umbilical vein supplies the fetus with oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

ated, nutrient
Nutrient
A nutrient is a chemical that an organism needs to live and grow or a substance used in an organism's metabolism which must be taken in from its environment. They are used to build and repair tissues, regulate body processes and are converted to and used as energy...

-rich blood
Blood
Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....

 from the placenta
Placenta
The placenta is an organ that connects the developing fetus to the uterine wall to allow nutrient uptake, waste elimination, and gas exchange via the mother's blood supply. "True" placentas are a defining characteristic of eutherian or "placental" mammals, but are also found in some snakes and...

. Conversely, the fetal heart pumps deoxygenated, nutrient-depleted blood through the umbilical arteries back to the placenta.

Development and composition

The umbilical cord develops from and contains remnants of the yolk sac
Yolk sac
The yolk sac is a membranous sac attached to an embryo, providing early nourishment in the form of yolk in bony fishes, sharks, reptiles, birds, and primitive mammals...

 and allantois
Allantois
Allantois is a part of a developing animal conceptus . It helps the embryo exchange gases and handle liquid waste....

 (and is therefore derived from the same zygote
Zygote
A zygote , or zygocyte, is the initial cell formed when two gamete cells are joined by means of sexual reproduction. In multicellular organisms, it is the earliest developmental stage of the embryo...

 as the fetus). It forms by the fifth week of fetal development, replacing the yolk sac as the source of nutrients for the fetus. The cord is not directly connected to the mother's circulatory system, but instead joins the placenta
Placenta
The placenta is an organ that connects the developing fetus to the uterine wall to allow nutrient uptake, waste elimination, and gas exchange via the mother's blood supply. "True" placentas are a defining characteristic of eutherian or "placental" mammals, but are also found in some snakes and...

, which transfers materials to and from the mother's blood without allowing direct mixing. The length of the umbilical cord is approximately equal to the crown-rump length
Crown-rump length
Crown-rump length is the measurement of the length of human embryos and fetuses from the top of the head to the bottom of the buttocks...

 of the fetus throughout pregnancy. The umbilical cord in a full term neonate is usually about 50 centimeters (20 in
Inch
An inch is the name of a unit of length in a number of different systems, including Imperial units, and United States customary units. There are 36 inches in a yard and 12 inches in a foot...

) long and about 2 centimeters (0.75 in) in diameter. This diameter decreases rapidly within the placenta. The fully patent umbilical artery has two main layers: an outer layer consisting of circularly arranged smooth muscle cells and an inner layer which shows rather irregularly and loosely arranged cells embedded in abundant ground substance
Ground substance
Ground substance is a term for the non-cellular components of extracellular matrix which contain the fibers.It is usually not visible on slides, because it is removed during the preparation process....

 staining metachromatic
Metachromasy
Metachromasy is a characteristic change in the color of staining carried out in biological tissues, exhibited by certain aniline dyes when they bind to particular substances present in these tissues, called chromotropes. For example, toluidine blue becomes pink when bound to cartilage...

. The smooth muscle cells of the layer are rather poorly differentiated, contain only a few tiny myofilament
Myofilament
Myofilaments, the filaments of myofibrils constructed from proteins,. The principal types of muscle are striated muscle, obliquely striated muscle and smooth muscle. Various arrangements of myofilaments create different muscles. Striated muscle has transverse bands of filaments...

s and are thereby unlikely to contribute actively to the process of postnatal closure.

The umbilical cord is composed of Wharton's jelly
Wharton's jelly
Wharton's jelly is a gelatinous substance within the umbilical cord, largely made up of mucopolysaccharides . It also contains some fibroblasts and macrophages...

, a gelatinous substance made largely from mucopolysaccharides. It contains one vein, which carries oxygenated, nutrient-rich blood to the fetus, and two arteries that carry deoxygenated, nutrient-depleted blood away. Occasionally, only two vessels (one vein and one artery) are present in the umbilical cord. This is sometimes related to fetal abnormalities, but it may also occur without accompanying problems.

It is unusual for a vein to carry oxygenated blood and for arteries to carry deoxygenated blood (the only other examples being the pulmonary veins and arteries, connecting the lungs to the heart). However, this naming convention reflects the fact that the umbilical vein carries blood towards the fetus's heart, while the umbilical arteries carry blood away.

The blood flow through the umbilical cord is approximately 35 ml / min at 20 weeks, and 240 ml / min at 40 weeks of gestation. Adapted to the weight of the fetus, this corresponds to 115 ml / min / kg at 20 weeks and 64 ml / min / kg at 40 weeks.

Connection to fetal circulatory system

The umbilical cord enters the fetus via the abdomen, at the point which (after separation) will become the umbilicus
Navel
The navel is a scar on the abdomen caused when the umbilical cord is removed from a newborn baby...

 (or navel). Within the fetus, the umbilical vein continues towards the transverse fissure of the liver
Liver
The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...

, where it splits into two. One of these branches joins with the hepatic portal vein
Hepatic portal vein
The hepatic portal vein is not a true vein, because it does not conduct blood directly to the heart. It is a vessel in the abdominal cavity that drains blood from the gastrointestinal tract and spleen to capillary beds in the liver...

 (connecting to its left branch), which carries blood into the liver. The second branch (known as the ductus venosus
Ductus venosus
In the fetus, the ductus venosus shunts approximately half of the blood flow of the umbilical vein directly to the inferior vena cava. Thus, it allows oxygenated blood from the placenta to bypass the liver. In conjunction with the other fetal shunts, the foramen ovale and ductus arteriosus, it...

) allows the majority of the incoming blood (approximately 80%) to bypass the liver and flow via the left hepatic vein
Hepatic vein
In human anatomy, the hepatic veins are the blood vessels that drain de-oxygenated blood from the liver and blood cleaned by the liver into the inferior vena cava....

 into the inferior vena cava
Inferior vena cava
The inferior vena cava , also known as the posterior vena cava, is the large vein that carries de-oxygenated blood from the lower half of the body into the right atrium of the heart....

, which carries blood towards the heart. The two umbilical arteries branch from the internal iliac arteries, and pass on either side of the urinary bladder
Urinary bladder
The urinary bladder is the organ that collects urine excreted by the kidneys before disposal by urination. A hollow muscular, and distensible organ, the bladder sits on the pelvic floor...

 befoin term ones. In contrast to the contribution of Wharton's jelly, cooling causes only temporary vasoconstriction.

Within the child, the umbilical vein and ductus venosus close up, and degenerate into fibrous remnants known as the round ligament of the liver and the ligamentum venosum
Ligamentum venosum
The ligamentum venosum is the fibrous remnant of the ductus venosus of the fetal circulation. Usually, it is attached to the left branch of the portal vein within the porta hepatis...

 respectively. Part of each umbilical artery closes up (degenerating into what are known as the medial umbilical ligament
Medial umbilical ligament
The medial umbilical ligament is a paired structure found in human anatomy. It is on the deep surface of the anterior abdominal wall, and is covered by the medial umbilical folds ....

s), while the remaining sections are retained as part of the circulatory system.

Problems and abnormalities

A number of abnormalities can affect the umbilical cord, which can cause problems that affect both mother and child:
  • Nuchal cord
    Nuchal cord
    A nuchal cord occurs when the umbilical cord becomes wrapped around the fetal neck 360 degrees. Nuchal cords are very common, with prevalence rates of 6% to 37%...

    , when the umbilical cord becomes wrapped around the fetal neck
  • Velamentous cord insertion
    Velamentous cord insertion
    Velamentous cord insertion is an abnormal condition during pregnancy. Normally, the umbilical cord inserts into the middle of the placenta as it develops. In velamentous cord insertion, the umbilical cord inserts into the fetal membranes , then travels within the membranes to the placenta...

  • Single umbilical artery
    Single umbilical artery
    Occasionally, there is only the one single umbilical artery present in the umbilical cord. Approximately this affects between 1 in 100 and 1 in 500 pregnancies, making it the most common umbilical abnormality. It is more common in multiple births. Its cause is not known.Most cords have one vein...

  • Umbilical cord prolapse
  • Vasa praevia
    Vasa praevia
    Vasa praevia is an obstetric complication defined as "fetal vessels crossing or running in close proximity to the inner cervical os...


Clamping and cutting

General hospital
Hospital
A hospital is a health care institution providing patient treatment by specialized staff and equipment. Hospitals often, but not always, provide for inpatient care or longer-term patient stays....

-based obstetric
Obstetrics
Obstetrics is the medical specialty dealing with the care of all women's reproductive tracts and their children during pregnancy , childbirth and the postnatal period...

 practice introduces artificial clamping as early as 1 minute after the birth of the child. In birthing center
Birthing center
A birthing center or centre is a healthcare facility, staffed by nurse-midwives, midwives and/or obstetricians, for mothers in labor, who may be assisted by doulas and coaches. By attending the laboring mother, the doulas can assist the midwives and make the birth easier. The midwives monitor the...

s, this may be delayed by 5 minutes or more, or omitted entirely. Clamping is followed by cutting of the cord, which is painless due to the lack of any nerve
Nerve
A peripheral nerve, or simply nerve, is an enclosed, cable-like bundle of peripheral axons . A nerve provides a common pathway for the electrochemical nerve impulses that are transmitted along each of the axons. Nerves are found only in the peripheral nervous system...

s. The cord is extremely tough, like thick sinew, and so cutting it requires a suitably sharp instrument. Provided that umbilical severance occurs after the cord has stopped pulsing (5–20 minutes after birth), there is ordinarily no significant loss of either venous or arterial blood while cutting the cord.

There are umbilical cord clamps which combine the cord clamps with the knife. These clamps are safer and faster, allowing one to first apply the cord clamp and then cut the umbilical cord. After the cord is clamped and cut, the newborn wears a plastic clip on the navel area until the compressed region of the cord has dried and sealed sufficiently. The remaining umbilical stub remains for up to 7–10 days as it dries and then falls off.

Early versus delayed clamping

The health implications of early versus delayed cord clamping are receiving attention in medical journals.

Delayed clamping may be supported by various health benefits: A recent analysis of attended home births over a 6-year period reported that none of the infants experienced adverse outcomes as a result of delayed cord clamping. A meta-analysis showed that delaying clamping of the umbilical cord in full-term neonates for a minimum of 2 minutes following birth is beneficial to the newborn in giving improved hematocrit
Hematocrit
The hematocrit or packed cell volume or erythrocyte volume fraction is the percentage of the concentration of red blood cells in blood. It is normally about 45% for men and 40% for women...

, iron status as measured by ferritin
Ferritin
Ferritin is a ubiquitous intracellular protein that stores iron and releases it in a controlled fashion. The amount of ferritin stored reflects the amount of iron stored. The protein is produced by almost all living organisms, including bacteria, algae and higher plants, and animals...

 concentration and stored iron, as well as a reduction in the risk of anemia (relative risk
Relative risk
In statistics and mathematical epidemiology, relative risk is the risk of an event relative to exposure. Relative risk is a ratio of the probability of the event occurring in the exposed group versus a non-exposed group....

, 0.53; 95% CI, 0.40-0.70). A decrease was also found in a study from 2008. However, a Cochrane Review from 2008 showed that, although there is higher hemoglobin level at 2 months, this effect did not persist beyond 6 months of age.

Negative effects of delayed cord clamping include an increased risk of polycythemia
Polycythemia
Polycythemia is a disease state in which the proportion of blood volume that is occupied by red blood cells increases...

. Still, this condition appeared to be benign in studies. The 2008 Cochrane review found that infants whose cord clamping occurred later than 60 seconds after birth had a statistically higher risk of neonatal jaundice
Neonatal jaundice
Neonatal jaundice or Neonatal hyperbilirubinemia is a yellowing of the skin and other tissues of a newborn infant. A bilirubin level of more than 85 umol/l manifests clinical jaundice in neonates whereas in adults a level of 34 umol/l would look icteric...

 requiring phototherapy. Conversely, a recent randomized, controlled trial noted in the 2008 Examination of the Newborn & Neonatal Health compared the timing of cord clamping on the newborn venous hematocrit
Hematocrit
The hematocrit or packed cell volume or erythrocyte volume fraction is the percentage of the concentration of red blood cells in blood. It is normally about 45% for men and 40% for women...

 and reported an increase in anemia
Anemia
Anemia is a decrease in number of red blood cells or less than the normal quantity of hemoglobin in the blood. However, it can include decreased oxygen-binding ability of each hemoglobin molecule due to deformity or lack in numerical development as in some other types of hemoglobin...

 in the infants whose cords were clamped immediately.

Delayed clamping is not recommended for health care providers as a solution to cases where the newborn is not breathing well and needs resuscitation. Rather, the recommendation is instead to immediately clamp and cut the cord and perform cardiopulmonary resuscitation
Cardiopulmonary resuscitation
Cardiopulmonary resuscitation is an emergency procedure which is performed in an effort to manually preserve intact brain function until further measures are taken to restore spontaneous blood circulation and breathing in a person in cardiac arrest. It is indicated in those who are unresponsive...

. The umbilical cord pulsating is not a guarantee that the baby is receiving enough oxygen.

Umbilical nonseverance

Some parents choose to omit cord severance entirely, a practice called "lotus birth
Lotus Birth
Lotus birth, or umbilical nonseverance, is the practice of leaving the umbilical cord attached to both the baby and the placenta following birth, without clamping or severing, and allowing the cord the time to detach from the baby naturally...

" or umbilical nonseverance. The entire intact umbilical cord is allowed to dry like a sinew, which then separates naturally (typically on the 3rd day after birth), falling off and leaving a healed umbilicus.

Umbilical cord catheterization

As the umbilical vein is directly connected to the central circulation, it can be used as a route for placement of a venous catheter for infusion and medication. The umbilical vein catheter is a reliable alternative to percutaneous peripheral or central venous catheters or intraosseous canulas and may be employed in resuscitation or intensive care of the newborn.

Storage of cord blood

Recently, it has been discovered that the blood within the umbilical cord, known as cord blood
Cord blood
Umbilical cord blood is blood that remains in the placenta and in the attached umbilical cord after childbirth. Cord blood is collected because it contains stem cells which can be used to treat hematopoietic and genetic disorders.-Collection:...

, is a rich and readily available source of primitive, undifferentiated
Cellular differentiation
In developmental biology, cellular differentiation is the process by which a less specialized cell becomes a more specialized cell type. Differentiation occurs numerous times during the development of a multicellular organism as the organism changes from a simple zygote to a complex system of...

 stem cell
Stem cell
This article is about the cell type. For the medical therapy, see Stem Cell TreatmentsStem cells are biological cells found in all multicellular organisms, that can divide and differentiate into diverse specialized cell types and can self-renew to produce more stem cells...

s (of type CD34
CD34
CD34 molecule is a cluster of differentiation molecule present on certain cells within the human body. It is a cell surface glycoprotein and functions as a cell-cell adhesion factor. It may also mediate the attachment of stem cells to bone marrow extracellular matrix or directly to stromal cells...

-positive and CD38
CD38
CD38 , also known as cyclic ADP ribose hydrolase is a glycoprotein found on the surface of many immune cells , including CD4+, CD8+, B and natural killer cells...

-negative). These cord blood cells can be used for bone marrow transplant
Bone marrow transplant
Hematopoietic stem cell transplantation is the transplantation of multipotent hematopoietic stem cell or blood, usually derived from bone marrow, peripheral blood stem cells, or umbilical cord blood...

.

Some parents have chosen to have this blood diverted from the baby's umbilical blood transfer through early cord clamping and cutting, to freeze for long-term storage at a cord blood bank
Cord blood bank
A cord blood bank is a facility which stores umbilical cord blood for future use. Both private and public cord blood banks have developed since the mid- to late-1990s in response to the potential for cord blood transplants in treating diseases of the blood and immune systems.Public banks accept...

 should the child ever require the cord blood stem cells (for example, to replace bone marrow
Bone marrow
Bone marrow is the flexible tissue found in the interior of bones. In humans, bone marrow in large bones produces new blood cells. On average, bone marrow constitutes 4% of the total body mass of humans; in adults weighing 65 kg , bone marrow accounts for approximately 2.6 kg...

 destroyed when treating leukemia
Leukemia
Leukemia or leukaemia is a type of cancer of the blood or bone marrow characterized by an abnormal increase of immature white blood cells called "blasts". Leukemia is a broad term covering a spectrum of diseases...

). This practice is controversial, with critics asserting that early cord blood withdrawal at the time of birth actually increases the likelihood of childhood disease, due to the high volume of blood taken (an average of 108ml) in relation to the baby's total supply (typically 300ml). The Royal College of Obstetricians and Gynaecologists
Royal College of Obstetricians and Gynaecologists
The Royal College of Obstetricians and Gynaecologists is a professional association based in the UK. Its members, including people with and without medical degrees, work in the field of obstetrics and gynaecology, that is, pregnancy, childbirth, and female sexual and reproductive health...

 stated in 2006 that "there is still insufficient evidence to recommend directed commercial cord blood collection and stem-cell storage in low-risk families".

The American Academy of Pediatrics
American Academy of Pediatrics
The American Academy of Pediatrics is the major professional association of pediatricians in the United States. The AAP was founded in 1930 by 35 pediatricians to address pediatric healthcare standards. It currently has 60,000 members in primary care and sub-specialist areas...

 has stated that cord blood banking for self-use should be discouraged (as most conditions requiring the use of stem cells will already exist in the cord blood), while banking for general use should be encouraged. In the future, cord blood-derived embryonic-like stem cells (CBEs) may be banked and matched with other patients, much like blood and transplanted tissues. The use of CBEs could potentially eliminate the ethical difficulties associated with embryonic stem cells (ESCs).

While the American Academy of Pediatrics discourages private banking except in the case of existing medical need, it also says that information about the potential benefits and limitations of cord blood banking and transplantation should be provided so that parents can make an informed decision.

Cord blood education is also supported by legislators at the federal and state levels. In 2005, the National Academy of Sciences published an Institute of Medicine (IoM) report which recommended that expectant parents be given a balanced perspective on their options for cord blood banking. In response to their constituents, state legislators across the country are introducing legislation intended to help inform physicians and expectant parents on the options for donating, discarding or banking lifesaving newborn stem cells. Currently 17 states, covering two-thirds of U.S. births, have enacted legislation recommended by the IoM guidelines.

Research in this area that has the potential to revolutionize medicine is advancing rapidly and it is difficult for professional medical societies, and other resources that expectant parents turn to for information, to keep pace.

Physicians and researchers are making significant progress evaluating the safety and efficacy of umbilical cord blood stem cells for therapeutic uses far beyond cancers and blood disorders. The use of cord blood stem cells in treating conditions such as brain injury and Type 1 Diabetes is already being studied in humans, and earlier stage research is being conducted for treatments of stroke, and hearing loss.

The fundamental differences between private and public cord blood banking should be noted. Cord blood stored with private banks is reserved for use of the donor child only. In contrast, cord blood stored in public banks is accessible by anyone with a closely matching tissue type. The terms public and private do not necessarily indicate the funding source, but rather the availability of use.

The utilization of cord blood from public banks is rising rapidly. Currently it is used in place of a bone marrow transplant in the treatment of blood disorders such as leukemia, with donations released for transplant through one registry, Netcord, passing 9000. This is usually when the patient cannot find a matching bone marrow donor. It is this "extension" of the potential donor pool which has driven the expansion of public banks.

Private banks which collect for specific individuals store on the premise of future technologies and uses of cord blood. While this is a valid reason for private donation, it must be remembered that for many diseases such as leukemia, it is actually preferable to not use your own cord blood. This is because the disease may be in latent form in your own cord blood, as well as a graft-versus-tumor effect.

Anatomy

The umbilical cord in some mammals contains two distinct umbilical veins, rather than just one (as is the case for humans). Examples include cows and sheep.

Cord disposal

In some animals, the mother will gnaw through the cord, thus separating the placenta from the offspring. It (along with the placenta) is often eaten by the mother, to provide nourishment and to dispose of tissues that would otherwise attract scavengers or predators. In chimpanzees, the mother focuses no attention on umbilical severance, instead nursing her baby with cord, placenta, and all, until the cord dries and separates within a day of birth, at which time the cord is discarded. (This was first documented by zoologists in the wild in 1974.)

Other uses for the term "umbilical cord"

The term "umbilical cord" or just "umbilical" has also come to be used for other cords with similar functions, such as the hose connecting a surface-supplied diver
Surface supplied diving
Surface supplied diving refers to divers using equipment supplied with breathing gas using a diver's umbilical from the surface, either from the shore or from a diving support vessel sometimes indirectly via a diving bell...

 to his surface supply of air and/or heating, or a space-suited astronaut
Astronaut
An astronaut or cosmonaut is a person trained by a human spaceflight program to command, pilot, or serve as a crew member of a spacecraft....

to his spacecraft. Engineers sometimes use the term to describe a complex or critical cable connecting a component, especially when composed of bundles of conductors of different colors, thickness and types, terminating in a single multi-contact disconnect.
The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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