fetal circulation

circulation /cir·cu·la·tion/ (ser″ku-la´shun) movement in a regular course, as the movement of blood through the heart and blood vessels.

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collateral circulation  that carried on through secondary channels after obstruction of the principal channel supplying the part.

enterohepatic circulation  the cycle in which bile salts and other substances excreted by the liver are absorbed by the intestinal mucosa and returned to the liver via the portal circulation.

extracorporeal circulation  circulation of blood outside the body, as through an artificial kidney or a heart-lung apparatus.

fetal circulation  that propelled by the fetal heart through the fetus, umbilical cord, and placental villi.

Schematic diagram of fetal circulation, with red indicating the highest level of oxygen saturation, blue the lowest, and purple an intermediate level.

first circulation  primordial c.

hypophysioportal circulation  that passing from the capillaries of the median eminence of the hypothalamus into the portal vessels to the sinusoids of the adenohypophysis.

intervillous circulation  the flow of maternal blood through the intervillous space of the placenta.

lesser circulation  pulmonary c.

omphalomesenteric circulation  vitelline c.

persistent fetal circulation  pulmonary hypertension in the postnatal period secondary to right-to-left shunting of the blood through the foramen ovale and ductus arteriosus.

placental circulation 

1. the circulation of blood through the placenta during prenatal life.

2. intervillous c.

portal circulation  a general term denoting the circulation of blood through larger vessels from the capillaries of one organ to those of another; applied to the passage of blood from the gastrointestinal tract and spleen through the portal vein to the liver.

primordial circulation  the earliest circulation by which nutrient material and oxygen are conveyed to the embryo.

pulmonary circulation  the flow of blood from the right ventricle through the pulmonary artery to the lungs, where carbon dioxide is exchanged for oxygen, and back through the pulmonary vein to the left atrium.

systemic circulation  the general circulation, carrying oxygenated blood from the left ventricle to the body tissues, and returning venous blood to the right atrium.

umbilical circulation  fetal circulation through the umbilical vessels.

vitelline circulation  the circulation through the blood vessels of the yolk sac.

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fetal circulation,

the pathway of blood circulation in the fetus. Oxygenated blood from the placenta travels through the umbilical vein to the heart. The blood enters the right atrium at a pressure sufficient to direct most of the flow across the atrium and through the foramen ovale into the left atrium; thus oxygenated blood is available for circulation through the left ventricle to the head and upper extremities. The blood returning from the head and arms enters the right atrium via the superior vena cava. It flows through the atrium at a relatively low pressure. Passing the tricuspid valve, it falls into the right ventricle, from which most of it is pumped through the pulmonary artery and the ductus arteriosus into the descending aorta for circulation to the lower parts of the body. A small amount of blood in the pulmonary artery is not shunted through the ductus and is carried to the lungs. The blood is returned to the placenta through the umbilical arteries.

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circulation

movement in a regular or circuitous course, returning to the point of origin, as the circulation of the blood through the heart and blood vessels. See also circulatory system.

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antegrade circulation

circulation in the normal direction of flow.

artificial circulation

is maintained in cardiopulmonary arrest by cardiac compression.

collateral circulation

circulation carried on through secondary channels after obstruction of the principal channel supplying the part.

coronary circulation

that within the coronary vessels, which supply the muscle of the heart.

cutaneous circulation

cutaneous vessels are innervated by sympathetic adrenergic vasoconstrictor fibers; vasodilation is an important mechanism for losing heat after the body has been warmed.

enterohepatic circulation

the cycle in which bile salts and other substances excreted by the liver in the bile are absorbed by the intestinal mucosa and returned to the liver via the portal circulation.

extracorporeal circulation

circulation of blood outside the body, as through a hemodialyzer or an extracorporeal circulatory support unit.

fetal circulation

circulation of blood through the body of the fetus and to and from the placenta through the umbilical cord. See also fetal circulation.

hepatic circulation

includes the hepatic arterial blood supply and the supply from the portal vein; drainage is via the hepatic veins to the caudal vena cava.

lymph circulation

see lymph.

maternal circulation

the circulation of the dam during pregnancy, including especially that of the uterus.

micro-circulation

see microcirculation.

neonatal circulation

circulation in the newborn immediately after birth; the umbilical vessels contract forcing blood into the fetal veins; the foramen ovale closes, the ductus arteriosus narrows and eventually closes at day 1 to 2 after birth.

ocular circulation

consists of the uveal and retinal blood vessels supported by the aqueous humor and vitreous body.

placental circulation

consists of the umbilical arteries, the vessels of the placenta proper and the umbilical veins; approximates the fetal corporeal circulation in volume.

portal circulation

a general term denoting the circulation of blood through larger vessels from the capillaries of one organ to those of another; applied especially to the passage of blood from the gastrointestinal tract, pancreas and spleen through the portal vein to the liver.

pulmonary circulation

the flow of blood from the right ventricle through the pulmonary artery to the lungs, where carbon dioxide is exchanged for oxygen, and back through the pulmonary vein to the left atrium. See also pulmonary circulation.

splenic circulation

flow of blood through the splenic artery and arterioles to either the capillaries, e. g. white pulp, or the highly permeable sinuses of the red pulp. Splenic venous blood drains into the portal vein and passes through the liver before re-entering the general circulation.

systemic circulation

the flow of blood from the left ventricle through the aorta, carrying oxygen and nutrient material to all the tissues of the body, and returning through the superior and inferior venae cavae to the right atrium.

circulation time

the time required for blood to flow between two given points. It is determined by injecting a substance into a vein and then measuring the time required for it to reach a specific site.

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fetal

of or pertaining to a fetus or to the period of its development.

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fetal age

age of the fetus; this may be determined by its crown to rump length, and various other surface features such as hair follicles and eyelids.

fetal alcohol syndrome

in humans and laboratory animals; in laboratory animals manifested by small head and nose, narrow forehead, short palpebral fissures, long thin upper lip.

fetal circulation

the circulation of blood through the body of the fetus and to and from the placenta through the umbilical cord. Oxygenated blood from the placenta is carried to the fetus by the umbilical vein. The blood from the fetus is returned to the placenta by two umbilical arteries. Oxygenation of the fetal blood and disposal of its waste products is carried on through the placenta. When the lungs begin to function at birth some of the fetal vessels, such as the ductus arteriosus, and the fetal passages, such as the foramen ovale, begin to fall into disuse. This is a gradual process of fibrosis that takes place in the period after birth.

fetal crowding

too much fetal tissue in the uterus. May cause fetal retardation in some; also papyraceous fetus. Thought to cause some of the minor congenital deformities, e.g. carpal flexion in calves, facial distortion in foals.

fetal death

results in resorption, mummification or discharge to the exterior.

fetal death ratio

see fetal death ratio.

fetal dimensions

crown to rump (tail head) length; varies with species; useful as a guide to pregnancy duration.

fetal disease

disease of the fetus in utero.

fetal dropsy

in cattle may be due to inherited defect of lymph nodes and lymphatic drainage.

fetal dystocia

dystocia caused by some characteristic of the fetus, e.g. size, monstrosity, dropsy.

fetal early death

see early embryonic mortality.

fetal extractor

a device consisting of a breech bar that fits across the back of the cow's thighs below the vulva, with a 6 ft long rod with a ratchet running its length. A small tractor is levered along the ratchet and exerts traction on the calf via obstetric chains fitted to its feet. Has the advantages of a block and tackle but with the mobility of being fixed to the cow.

Calving jack (fetal extractor) for use in a cow. By permission from Parkinson TJ, England GCW, Arthur GH, Arthur's Veterinary Reproduction and Obstetrics, Saunders, 2001

fetal fluids

the amniotic and allantoic fluids.

fetal giantism

due to prolonged gestation, although all prolonged gestations are not giants. Inherited in Holstein cows.

fetal hepatitis

focal or diffuse lesions in the fetal liver caused by bacteria or viruses, e.g. Tyzzer's disease, equine herpesvirus 1.

fetal maceration

sterile necrosis and dissolution of the fetus. May be ejected in this form or go on to mummification.

fetal malposition

presentation of the fetal parts in inappropriate positions for the easiest passage through the cervix, e.g. retention of the head, breech presentation.

fetal maternal rotation

alteration of the longitudinal relationship of the fetus to the dam effected per vaginam by manipulation with the hand or an obstetric crutch, or externally by casting the dam and rolling her from side to side while the fetus is held in position via a hand in the vagina.

fetal membranes

the membranes which protect the embryo and provide for its nutrition, respiration and excretion; the yolk sac (umbilical vesicle), allantois, amnion, chorion, decidua and placenta. See also extraembryonic membranes, placenta.

fetal membrane expulsion

occurs usually at the birth or less commonly within 12 hours; expulsion is by means of separation of the uterine attachment and contraction and involution of the uterine wall.

fetal membrane retention

see retained placenta.

fetal membrane slip

the sensation of a thread or edge of tissue slipping through the fingers when the amniotic vesicle in an early pregnant bovine uterus is grasped between the thumb and forefinger; the best indicator in a manual check for pregnancy until the time when cotyledons can be palpated.

fetal mobility

fetal movements during pregnancy.

fetal mole

see mole.

fetal monstrosities

see monster, monstrosity.

fetal position

position of the fetus within the dam, described in terms of the dorsum of the fetus and the sector of the circumference of the dam's pelvis, e.g. dorsosacral, dorsoventral.

fetal posture

relationship of the movable extremities or appendages of the fetus to each other and the rest of the fetus, e.g. flexed neck.

fetal presentation

see presentation.

fetal rotation

a method of correcting uterine torsion in cows; the fetus is reached manually via the vagina and the fetus rotated around its long axis using a firm grasp on the upper part of a limb as a handle; the uterus, clinging to the fetus, rotates with it, undoing the torsion. Requires a fresh parturition, a slim but strong forearm and a nice appreciation of the physical law of torque.

fetal resorption

early death of the embryo during the fetal period with lysis and complete resorption of all of the products of the conception. The dam resumes normal estral cyclicity after a period of anestrus while there is maternal recognition of the pregnancy. See also early embryonic mortality.

fetal sex diagnosis

the karyotype of the fetus is determined from fetal cells collected from the amniotic fluid by amniocentesis.

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fetal circulation

Embryology Prenatal circulation which bypasses the lung and right heart, and is returned to the systemic circulation at the aorta via a patent ductus arteriosus, which usually closes at or shortly after birth, after which the blood flows to the lungs