2D:4D
ratio of 2nd and 4th finger (digit) length. This ratio has been suggested to relate to high fetal testosterone concentration (males have lower 2D:4D than females) and also thought to be an indicator of various neurological abnormalities. (More? Neural Abnormalities | Endocrine Notes | McIntyre MH. The use of digit ratios as markers for perinatal androgen action. Reprod Biol Endocrinol. 2006 Feb 26;4:10.)
abdominal circumference
(AC) used in clinical ultrasound measurements made in late pregnancy and reflects fetal growth in size and weight. (More? Ultrasound Movies)
abnormal spindle-like microcephaly-associated protein
concentrated at mitotic spindle poles in embryonic neuroepithelial cells (progenitor cells of the brain) and down-regulated when they switch from proliferative to neurogenic divisions. Protein is associated with determining human cerebral cortical size, possibly by maintaining symmetric cleavage plane orientation in neuroepithelial cells during brain development. (More? Neural Notes | Neural Abnormalities | OMIM ASPM | Fish JL, Kosodo Y, Enard W, Paabo S, Huttner WB. Aspm specifically maintains symmetric proliferative divisions of neuroepithelial cells. Proc Natl Acad Sci U S A. 2006 Jun 23)
abortion
premature expulsion or loss of embryo, may be induced (medical) or spontaneous (miscarriage).
AC
acronym for abdominal circumference, clinical ultrasound measurements made in late pregnancy and reflects fetal growth in size and weight. (More? Ultrasound Movies)
acaricide
Acarida are a subclass of the athropods, ticks and mites. Chemicals used for killing or preventing ticks and mites in crops or animals. Some of the early chemicals (eg endosulphan) may have also had a suggested endocrine disruptor function. (More? Endocrine Abnormalities)
accessory pancreatic duct
(APD) also called Santorini’s duct may be present as an anatomical variation due to the embryological origin of the pancreas from two pancreatic buds (dorsal and ventral). Note the main pancreatic duct (MPD) from the dorsal bud, present in the body and tail of the pancreas (also called Wirsung’s duct). (More? Pancreas | Pancreas History)
acheiria
limb abnormality with a missing hand or foot as described in the original classical classification of limb deficiencies. (More? Limb Abnormalities - Classification)
achondroplasia
short limb skeletal dysplasia, due to a mutation in a dominant gene encoding fibroblast growth factor receptor-3 (FGFR3). Most common limb dysplasia, with shortened long bones (mainly proximal long bones) and is difficult to prenatally diagnose. Other mutaions of this gene cause milder skeletal dysplasia (hypochondroplasia) and a lethal skeletal dysplasia (thanatophoric dysplasia). (More? Musculoskeletal Abnormalities | OMIM Achondroplasia | FGFR3)
acrocentric
used to describe chrompsomes which pair with a centromere located very close to one end giving a "V" shape rather than "X" of a central centromere pair. In the human, chromosomes 13,14,15,21 and 22 are acrocentric. In bovine all chromosomes are acrocentric. (More? Endocrine Notes)
acrolein
reactive aldehyde (conjugated Type-2 alkenes) formed as a product of lipid peroxidation in biological systems. Recently identified as a cigarette-related lung cancer agent (More? Abnormal Development - Smoking | PNAS Article)
Acquired Immune Deficiency Syndrome (AIDS)
a fatal disease caused by a virus (human immunodeficiency virus, HIV) that destroys the immune system's ability to fight off infection. HIV virus is capable of being transmitted from mother to fetus. (More? Abnormal Development - Viral Infection)
acrodynia
(Greek, acrodynia = painful extremities) chronic mercury poisoning in infants and young, also called "Pink Disease" occurred throughout the world (Australia 1890's) before the recognition of mercurys toxic effects. Mercurous chloride was used in "teething powders" which were given to crying babies as a purgative agent to cleanse the system. (More? Heavy metals | Michigan Health MercurySpillFactsheet_85689_7.pdf)
acromegaly
in the adult, overproduction of growth hormone causes bone thickening and cartilage growth.
acroplaxome
forms the acrosome plate with intermediate filament bundles of the marginal ring at the leading edge of the acrosome. (More? Spermatogenesis | Fertilization)
acrosin
spermatazoa acrosomal protein has a role in fertilization including that of lysis of the zona pellucida (a serine protease) and in secondary zona pellucida (ZP) binding. Stored in mature spermatazoa as proacrosin. (More? Spermatogenesis | Fertilization | OMIM Entry)
acrosome
the packet of enzymes in a sperm's head that allows the sperm to dissolve a hole in the coating around the egg, which allows the sperm to penetrate and fertilize the egg (More? Spermatogenesis | Fertilization)
acrosome reaction
a chemical change that enables a sperm to penetrate an egg. (More? Spermatogenesis | Fertilization)
activin A
(inhibin, erythroid differentiation factor) a transforming growth factor beta (TGFbeta) superfamily member which has roles in many different tissues. Acts through binding a number of activin receptors, transmembrane ser/thr kinase receptors. This protein is involved in the process of uterine endometrium development (decidualization) of human endometrial stromal cells following blastocyst implantation. (More? Week 2 Notes | OMIM - inhibin)
adactyly
the absence of metacarpal or metatarsal leading to an absence of all digits as described in the original classical classification of limb deficiencies. (More? Limb Abnormalities - Classification | Limb Abnormalities - Hand Classification)
ADAMTS-13
a blood metalloprotease, found in plasma, which cleaves von Willebrand factor (VWF) in the A2 domain at the Tyr-1605–Met-1606 bond.
adenine
(adenine triphosphate) one of the 4 types (ATCG) of nucleotides that make up DNA. Base pairs with thymidine by 2 hydrogen bonds.
adenohypophysis
anterior pituitary, pars distalis. This part of the pituitary develops in the early embryo from a region (that exists only transiently) on the roof of the pharynx called Rathke's pouch. (More? Endocrine Development - Pituitary)
adenomyosis
(endometriosis interna, adenomyoma) a uterus disease involving infiltration (immediately adjacent to the endometrial cavity) of endometrial glands and stroma within the myometrium. Difficult to distinguish from leiomyoma. (More? Reproductive System - Abnormalities | Medlineplus - adenomyosis)
adenovirus
a Class I virus containing a single double-stranded DNA (dsDNA), which can cause infections in the upper respiratory tract and gastrointestinal tract in many animals. (More? Abnormal Development - Viral Infection)
adnexa
(Latin, adnexae = appendages) used to describe any anatomical appendage (accessory structure, extension or outgrowth from the body). In reproductive anatomy used to describe appendages of the uterus "body"; ovaries, uterine tubes and uterus supporting ligaments.
adrenal virilism
the development of male secondary sexual characteristics in women with excessive adrenal gland activity. (More? Endocrine Notes)
AFP
acronym for Alpha-FetoProtein a protein detected in a prenatal diagnostic test. (More? Alpha-FetoProtein)
Age-specific fertility rates
statistical value (used by Australian Bureau of Statistics) showing the number of live births (occurred or registered) during the calendar year, according to age of mother, per 1,000 of the female estimated resident population of the same age at 30 June. (More? Australian Statistics)
Artificial Insemination
(AI) placement of a sperm sample inside the female reproductive tract can be carried out by a number of different techniques: intracervical insemination, intrauterine insemination, intratubal insemination. (More? Week 1 Notes)
alar plate
the dorsal region in the developing neural tube derived from the lateral regions of the nerual plate In the spinal cord, this is the sensory afferent, dorsal horn region. Nomenclature may have come from the "wing-like" appearance of this region of the folding neural plate. (More? Neural Notes | Dev Biol Development of the human spinal cord)
alpha
Greek letter, (Α capital letter alpha; α lower case alpha) first letter of the Greek alphabet. The lower case form used in scientific literature to designate the first forms/variants of a similar protein, gene, energy form or substance. (More? Greek Symbols)
alpha-fetoprotein test (AFP)
A prenatal test to measure the amount of a fetal protein in the mother's blood (or amniotic fluid). Abnormal amounts of the protein may indicate genetic or developmental problems in the fetus. Low levels of AFP normally occur in the blood of a pregnant woman, high levels may indicate neural tube defects (spina bifida, anencephaly). (More? Abnormal Development- AFP test)
alpha smooth muscle actin
(SMA) one of the 6 mammalian actin isoforms. This actin is associated with vascular smooth muscle, but SMA can also be expressed in myofibroblasts, and is involved in cell-generated mechanical tension.
alpha synuclein
a protein found in neurons. A dominantly inherited mutation in alpha-synuclein can cause Parkinson’s disease. (More? UNSW Cell Biology)
allantois
extraembryonic membrane, generates vascularization of chorion, proximally forms urinary bladder.
allosteric
(Greek allos = other , stereos = solid or three-dimensional) used to describe proteins (receptors, enzymes, motors) that have at least 2 sites that alter the protein properties. The active site binds the principal substrate. The regulatory site(s) bind effector molecule(s) that influence the protein's biological activity.
Alzheimer's Disease
(AD) a neurodegenerative disease associated mainly with ageing. Histopathology is shown psotmortum by extracellular beta-amyloid (Aß) fibrils plus intraneuronal tau (a microtubule associated protein) filaments. (More? Neural Notes)
amelia
the complete absence of a limb, as described in the original classical classification of limb deficiencies. (More? Limb Abnormalities - Classification)
amenorrhea
absence of a menstrual period, it can be either primary (not yet had a period by age 16) or secondary (regular period that has now stopped for 3 months). (More? Human Menstrual Cycle)
amniocentesis
a prenatal diagnostic test involving sampling of amniotic fluid by needle aspiration for genetic analysis. (More? Prenatal Diagnosis - Amniocentesis)
amnioinfusion
a medical procedure in which a physiologic solution (such as normal saline) is infused into the uterine cavity to replace the amniotic fluid.
amnion
the fluid-filled sac initially above the embryonic disc (ectoderm and extaembryonic mesoderm), with embryoic disc folding this sac is drawn ventrally to enclose (cover) the embryo, then fetus.
amniotic fluid
fills amniotic cavity totally encloses and cushions the embryo. Amniotic fluid enters both the gastrointestinal and respiratory tract following rupture of the buccopharyngeal membrane. The late fetus swallows amniotic fluid.
amniotic band syndrome
(amniotic bands) are relatively rare and is caused by damage to the amnion, producing fiber-like bands that trap periperal structures (arms, legs, fingers, or toes) reducing local blood supply in turn leading to abnormal development of those structures or regions. (More? Musculoskeletal - Limb Development Abnormalities)
amniotomy
birth medical procedure thought to speed labor, where the amniotic sac is artificially ruptured using a tool (amniohook). (More? Normal Development - Birth)
aminopterin
rodenticide also studied as a chemotherapy drug for treating leukemia and other cancers. Teratogenic, not used as a rodenticide in the USA because exposure to it is associated with serious birth defect. (More? Abnormal Development)
amphimixis
(Greek, amphi = on both sides ; mixis = a mingling) term to describe fusion of male and female gametes, also used when referring to pronuclei fusion. (More? Week 1 Notes)
amphiregulin
(AREG) also called schwannoma-derived growth factor (SDGF). A heparin-binding and heparin-inhibited epidermal growth factor (EGF) family member, which stimulates fibroblast and keratinocyte proliferation. In mammary glands, under induction by estrogen, it stimulates mammary epithelium proliferation during puberty. (More? Integumentary Development - Mammary Glands | Puberty | OMIM - amphiregulin)
ampulla
dilation of canal lumen. Anatomical description of the opening end of the uterine tube lying above the ovary.
anagen
hair follicle active growth phase, hair follicle progenitors derived from the bulge interact with the mesenchymal dermal papilla cells to generate the lineages of the hair follicle (telogen phase is resting phase of hair growth cycle). (More? Integumentary Development - Hair)
anaphase
(Greek, ana = up, again) mitotic stage, paired chromatids separate and migrate to spindle poles. (More? Week 1 - Mitosis | Week 1 Notes)
anaphase A
The part of anaphase during which the chromosomes move. (More? Week 1 - Mitosis | Week 1 Notes)
anaphase B
The part of anaphase during which the poles of the spindle move apart. (More? Week 1 - Mitosis | Week 1 Notes)
anastomosis
connection between two tubes. Term used with peripheral blood vessels without capillary bed.
anacephaly
developmental abnormality, incomplete development of cerebral hemispheres and cranium. Usually related to neural tube defect at the cranial neuropore. (More? Neural Notes | Neural Abnormalities)
aneuploidy
abnormal number of chromosomes mainly (90%) due to chromosome malsegregation mechanisms in maternal meiosis I. (More? Trisomy 21 | Meiosis)
angiopoietin
(ANGPT) factors of the vascular endothelial growth factor family which are involved with blood vessel development, recognised by two tyrosine kinase receptors (Tie1 and Tie2). Angiopoietin-1 and Angiopoietin-2 appear to have opposite effects acting through the same (Tie2) receptor. (More? Blood Vessel | OMIM - Angiopoietin 1 | OMIM - Tie2)
Animalia
The kingdom that includes animals, heterotrophic multicellular organisms that undergo embryonic development.
anticonvulsants
(antiepileptic drugs) a class of therapeutic drugs that are used to prevent and minimize seizures by acting on either ion channels, active transport, or membrane stabilization. In embryology they are teratogenic and increase the occurance of neural tube defects (NTDs). (Drug examples: Carbamazepine, Clonazepam, Ethosuximide, Phenobarbital, Phenytoin, Primidone, Valproic Acid) (More? Neural Abnormalities | Neural Tube Defects | Drug Use)
Anti-Mullerian Hormone
(AMH) also called Mullerian Inhibiting Substance (MIS). Secreted factor (transforming growth factor-beta, TGF-beta superfamily) that regulates gonadal and genital tract development. Inhibits paramesonephric (Mullerian) duct development in males. (More? Male | OMIM - AMH)
antral follicle
(secondary follicle) the stage following preantral (primary) in the decription of the sequence ovarian follicle development (primordial, preantral, antral). (More? Week 1 - Oogenesis)
antrum
(Latin from Greek, antron = a cave, cavity; a nearly-closed cavity or bulge). Identified anatomically in many structures (ovarian follicle, bone, cardiac, gastric). In the ovary this refers to the follicular fluid-filled space within the follicle. (More? Week 1 - Oogenesis)
apgar
Non-invasive clinical test designed by Dr Virginia Apgar (1953) carried out immediately on newborn. The name is also an acronym for: Activity (Muscle Tone), Pulse, Grimace (Reflex Irritability), Appearance (Skin Color), Respiration. A score is given for each sign at one minute and five minutes after the birth. (More? APGAR | History)
aphalangia
the absence of phalanges (long bones) leading to an absent digit, finger or toe as described in the original classical classification of limb deficiencies. (More? Limb Abnormalities - Classification | Limb Abnormalities - Hand Classification)
apoptosis
(Greek, apo = away from + ptosis = fall) Programmed cell death which occurs in the development of many systems. e.g. between digits, nervous system. Kerr JF, Wyllie AH, Currie AR. Apoptosis: a basic biological phenomenon with wide-ranging implications in tissue kinetics. Br J Cancer. 1972 Aug;26(4):239-57. Review. (More? necrosis | apoptosis )
Apoptosis Inducing Factor
(AIF) a mitochondrial protein associated apoptosis by initial chromatin condensation and high molecular weight DNA fragmentation.
appositional growth
(Latin, appositus = to put near) Used in describing a specific form of bone growth on a pre-existing surface or growth at the periphery. (appositus, past participle of appnere, to put near)
arachnoid
(Greek, arachne = spider + -oeides = form) spider web-like meningial layer covering central nervous system. Lies between tough outer duramater and fine piamater.
Archaea
(Greek, archein= to begin), also called the Archaebacteria The kingdom (or "domain") of single-celled organisms that live under extreme environmental conditions and have distinctive biochemical features.
Archaebacteria
(Greek, archein = to begin), also called the Archaea The kingdom (or "domain") of single-celled organisms that live under extreme environmental conditions and have distinctive biochemical features.
archenteron
(Greek, arche = beginning + enteron = gut) The "primitive gut," the innermost tube of an animal embryo; lined with endoderm, it will become the digestive tract.
arrhythmia
(= dysrhythmia) refers to cardiac abnormality of heartbeat either fast, slow, or irregular. (More? Heart Notes)
Arnold-Chiari Malformation
A type of malformation which appears multifactorial (including inherited and acquired). Cerebellar tonsils elongate and herniate through foramen magnum into spinal canal, resulting in compression of parts of the brain and spinal cord, and disruption of cerebrospinal fluid flow. Thought to be fundamentally the same as anencephaly and spina bifida. (More? Neural Abnormalities)
ART
acronym for Assisted Reproductive Technology. All treatments or procedures that involve the handling of human eggs and sperm for the purpose of helping a woman become pregnant. Types of ART include in vitro fertilization, gamete intrafallopian transfer, zygote intrafallopian transfer, embryo cryopreservation, egg or embryo donation, and surrogate birth. (More? Week 1 - In Vitro Fertilization)
ART cycle
A process in which 1) an ART procedure is carried out, 2) a woman has undergone ovarian stimulation or monitoring with the intent of having an ART procedure, or 3) in the case of frozen embryos, embryos have been thawed with the intent of transferring them to a woman. A cycle begins when a woman begins taking fertility drugs or having her ovaries monitored. (More? Week 1 Notes)
ASD
acronym for atrial septal defect, a developmental defect in the formation of the dividing septum between the two atria of the heart. (More? Heart Abnoormalities)
aster
(Latin, aster = star) A star-like object visible in most dividing eukaryotic cells contains the microtubule organizing center.
astral
Having an aster and centrioles that participate in mitosis; characteristic of mitosis in animals and in nonvascular plants.
astral microtubules
Microtubules that extend from each pole of the mitotic spindle without attaching to any other visible structure.
ataxia
(Greek, a = without + taxis = order) refers to a lack of coordination of muscule movements. Both central and peripherial neurological disorders can generate this loss of coordination. (More? Neural Notes | Neural Abnormalities | NINDS (USA) Ataxia Telangiectasia)
ataxia telangiectasias
neurodegenerative disease with no current cure resulting in death in teens or early 20's. (More? NINDS (USA) Ataxia Telangiectasia | Neural Abnoormalities)
ataxia-telangiectasia mutated
(ATM) protein kinase involved in early signaling of DNA damage (double-stranded DNA breaks) and initiates the signal transduction cascade at damage sites. ATM phosphorylates substrates involved in DNA repair and/or cell cycle control. See also Rad3-related (ATR) a broad spectrum DNA damage response signaling protein kinase. (More? DNA Notes OMIM - ataxia-telangiectasia mutated | Entrez - ataxia-telangiectasia mutated)
ataxia-telangiectasia and Rad3-related
(ATR) (= FRAP-related protein 1) a broad spectrum DNA damage response signaling protein kinase. (More? OMIM - ataxia-telangiectasia and Rad3-related | Entrez - ataxia-telangiectasia and Rad3-related)
atresia
(Greek, a = without + tresis = perforation) closing of a cavity or opening. (More? see atretic follicle
atretic follicle
an ovarian follicle that fails to mature and degenerates. Also called "atresia" referring to the process of degeneration of the ovarian follicle. At any one time the majority of follicles are destined not to complete maturation and degeneration can occur at any stage (from type 4-7). (More? Week 1 Notes | Ovary Notes)
atrial septal defect
(ASD) abnormal opening or hole in the septum between right and left atria. Normally allows left to right blood shunting, though additional cardiac abnormalities causing higher right side pressure (pulmonary stenosis or tricuspid atresia) allow right to left blood shunting. (More? Heart Abnoormalities)
auricular hillocks
series of 6 external "bumps" three on each of pharyngeal arch 1 and 2 that form the external ear (auricle). (More? External Ear | Hearing Notes)
Automated Auditory Brainstem Response
(AABR) basis of a neonatal hearing test that uses a stimulus delivered through earphones and detected by scalp electrodes. Computer ananalysed electrical measurement of activity through nuclei in the hearing central neural pathway. (More? Child Notes - Neonatal Hearing Screening)
autonomic nervous system
Involuntary nervous system; coordinates the responses of smooth muscles, cardiac muscles, and other effector organs including those of the endocrine, digestive, excretory, respiratory, and cardiovascular systems.
autosomal inheritance
some hereditary diseases are described as autosomal which means that the disease is due to a DNA error in one of the 22 pairs that are not sex chromosomes. Both boys and girls can then inherit this error. If the error is in a sex chromosome, the inheritance is said to be sex-linked. (More? DNA Notes)
autotroph
(Greek, autos = self + trophos = feeder) An organism that makes its own organic molecules from simple inorganic compounds (like carbon dioxide water and ammonia).
axial mesoderm
alternative name for the notochord, lying in the midline of mesoderm within the early trilaminar embryo. (More? notochord | Neural Notes | Week 3 Notes)
axoneme
The basic structure in cilia and eukaryotic flagella; consists of parallel microtubules in a characteristic "9 + 2 pattern". (More? Week 1 Notes)
AZF regions
regions on the long arm of Y chromosome (AZFa, b, and c) deletions of which result in severe damage to spermatogenesis with azoospermia or severe oligozoospermia. (More? Week 1 - Spermatogenesis | Week 1 Abnormalities)
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Search the NIH Medlineplus Medical Dictionary Type the word that you would like to find. If unsure of spelling, type the first few letters, followed by an asterisk(*). |
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Use this page to access brief definitions of specific alphabetically listed embryology terms. Additional information can be accessed from links listed at the end of each definition. Glossary from the UNSW Embryology program compiled and written by Dr Mark Hill. Reference Material used in preparing Glossary List: Texts listed on page 1 Reading of each notes section, Department of Anatomy Publications, WWW resources from NCBI, AMA (USA), Office of Rare Diseases (USA), PubMed Medline Dictionaries, MSDS, Merck Manual home edn., NHMRC (Australia). These notes are for Educational Purposes Only. Please email Dr Mark Hill if you wish to make a comment about this current project. |
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