fetal membranes

membrane /mem·brane/ (mem´brān) a thin layer of tissue that covers a surface, lines a cavity, or divides a space or organ.

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alveolar-capillary membrane , alveolocapillary membrane a thin tissue barrier through which gases are exchanged between the alveolar air and the blood in the pulmonary capillaries. Called also blood-air barrier and blood-gas barrier.

alveolodental membrane  periodontium.

arachnoid membrane  arachnoid (2).

atlantooccipital membrane  either of two midline ligamentous structures, one (the anterior ) passing from the anterior arch of the atlas to the anterior margin of the foramen magnum, and the other (the posterior ) connecting the posterior aspects of the same structures.

basement membrane  a sheet of amorphous extracellular material upon which the basal surfaces of epithelial cells rest; it is also associated with muscle cells, Schwann cells, fat cells, and capillaries, interposed between the cellular elements and the underlying connective layer.

Basement membrane, comprising the basal lamina and reticular lamina, in a diagram of a section through epithelial tissue.

basilar membrane of cochlear duct  lamina basilaris.

Bichat's membrane  fenestrated m.

Bowman's membrane  a thin layer of cornea between the outer layer of stratified epithelium and the substantia propria.

Bruch's membrane  the inner layer of the choroid, separating it from the pigmentary layer of the retina.

Brunn's membrane  the epithelium of the olfactory region of the nose.

cloacal membrane  the thin temporary barrier between the embryonic hindgut and the exterior.

Corti's membrane  a gelatinous mass resting on the organ of Corti, connected with the hairs of the hair cells.

croupous membrane  the false membrane of true croup.

cytoplasmic membrane  plasma m.

decidual membranes , deciduous membranes decidua.

Descemet's membrane  a thin hyaline membrane between the substantia propria and endothelial layer of the cornea.

diphtheritic membrane  a false membrane characteristic of diphtheria, formed by coagulation necrosis.

drum membrane  tympanic m.

elastic membrane  one made up largely of elastic fibers.

enamel membrane 

1. dental cuticle.

2. the inner layer of cells within the enamel organ of the fetal dental germ.

epiretinal membrane  a pathologic membrane partially covering the surface of the retina, probably originating chiefly from the retinal pigment epithelial and glial cells.

extraembryonic membranes  those that protect the embryo or fetus and provide for its nutrition, respiration, and excretion; the yolk sac (umbilical vesicle), allantois, amnion, chorion, decidua, and placenta.

false membrane  neomembrane; a membranous exudate, such as the diphtheritic membrane.

fenestrated membrane  one of the perforated elastic sheets of the tunica intima and tunica media of arteries.

fetal membranes  extraembryonic m's.

fibroelastic membrane of larynx  the fibroelastic layer beneath the mucous coat of the larynx.

germinal membrane  blastoderm.

glomerular membrane  the membrane covering a glomerular capillary.

hemodialyzer membrane  the semipermeable membrane that filters the blood in a hemodialyzer, commonly made of cuprophane, cellulose acetate, polyacrylonitrile, or polymethyl methacrylate.

hyaline membrane 

1. a membrane between the outer root sheath and inner fibrous layer of a hair follicle.

2. a layer of eosinophilic hyaline material lining alveoli, alveolar ducts, and bronchioles, found at autopsy in infants who have died of respiratory distress syndrome of the newborn.

hyaloid membrane  vitreous m. (1).

Jackson's membrane  a web of adhesions sometimes covering the cecum and causing obstruction of the bowel.

keratogenous membrane  matrix unguis.

limiting membrane  one which constitutes the border of some tissue or structure.

medullary membrane  endosteum.

mucous membrane  the membrane lining various canals and cavities of the body.

Nasmyth's membrane  dental cuticle.

nuclear membrane 

1. either of the membranes, inner and outer, comprising the nuclear envelope.

2. nuclear envelope.

olfactory membrane  the olfactory portion of the mucous membrane lining the nasal fossa.

ovular membrane  vitelline m.

peridental membrane , periodontal membrane periodontal ligament.

placental membrane  the membrane separating the fetal from the maternal blood in the placenta; sometimes inappropriately called the placental barrier.

Placental membrane separating the blood in the fetal capillaries from the maternal blood in the intervillous space. (A), chorionic villus containing the fetal vessels and surrounded by maternal blood in the intervillous space; (B), cross-section through a villus, showing the layers of the placental membrane separating the fetal blood from the maternal blood surrounding the villus.

plasma membrane  the structure, composed of lipids, proteins, and some carbohydrates, that encloses the cytoplasm of a cell, forming a selectively permeable barrier.

pupillary membrane  a mesodermal layer attached to the rim or front of the iris during embryonic development.

Reissner's membrane  the thin anterior wall of the cochlear duct, separating it from the scala vestibuli.

reticular membrane , reticulated membrane a netlike membrane over the spiral organ of the ear, through which pass the free ends of the outer hair cells.

membrane of round window  secondary tympanic m.

Ruysch's membrane , ruyschian membrane lamina choroidocapillaris.

Scarpa's membrane  secondary tympanic m.

schneiderian membrane  the mucous membrane lining the nose.

secondary tympanic membrane  the membrane enclosing the fenestra cochlearis.

serous membrane  tunica serosa.

Shrapnell's membrane  the thin upper part of the tympanic membrane.

suprapleural membrane  the strengthened portion of the endothoracic fascia attached to the inner part of the first rib and the transverse process of the seventh cervical vertebra.

synaptic membrane  the part of the plasma membrane of a neuron that is within a synapse.

synovial membrane 

1. the inner of the two layers of the articular capsule of a synovial joint, composed of loose connective tissue and having a free smooth surface that lines the joint cavity.

2. either of two membranes, superior and inferior, lining the articular capsule of the temporomandibular joint.

tectorial membrane  Corti's m.

tympanic membrane  the thin partition between the external acoustic meatus and the middle ear.

Tympanic membrane (membrana tympanica).

undulating membrane  a protoplasmic membrane running like a fin along the bodies of certain protozoa.

unit membrane  the trilaminar structure of the plasma membrane and other cellular membranes (e.g., nuclear m's, mitochondrial m's) revealed by the electron microscope.

vestibular membrane of cochlear duct  the thin anterior wall of the cochlear duct, separating it from the scala tympani.

vitelline membrane  the cytoplasmic, noncellular membrane surrounding an oocyte.

vitreous membrane 

1. a delicate boundary layer investing the vitreous body.

2. Bruch's m.

3. Descemet's m.

4. hyaline m. (1).

yolk membrane  vitelline m.

Zinn's membrane  ciliary zonule.

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fetal membranes,

the structures that protect, support, and nourish the embryo and fetus, including the yolk sac, allantois, amnion, chorion, placenta, and umbilical cord.

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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.