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Link to the Original UNSW Embryology Glossary M

macrosomia

Term used to describe a newborn with an excessive birth weight. The definition is either a birth weight of 4000 to 4500 g (8 lb 13 oz to 9 lb 15 oz) or greater than 90% for gestational age after correcting for neonatal sex and ethnicity.

(More? Human Fetal Weight | Maternal Diabetes)

magnetoencephalographic

(MEG) A brain imaging system that measures electromagnetic changes in regions of the brain that correspond to activity.

major urinary proteins

(MUPs) Proteins which carry volatile substances, including pheromones, and protect them during their internal passage (liver to kidneys into urine).

(More? Mouse Development- Estrous Cycle)

male factor

Any cause of infertility due to deficiencies in sperm quantity, function, or motility (ability to move) that make it difficult for a sperm to fertilize an egg under normal conditions.

(More? Week 1 Notes)

manchette

A transient microtubule structure formed in spermatids involved in the process of assembly of the mammalian sperm tail and mechanical shaping and condensation of the sperm nucleus.

(More? Spermatogenesis | Fertilization)

mandible

Term used to describe the lower jaw of the face, which forms from the lower part pharyngeal arch 1, the [#mandibular_process mandibular process]. The smaller upper part of pharyngeal arch 1 forms the two [#maxillary_process maxillary processes], which form the upper jaw.

(More? Face Development | Face Abnormalities | Head Development)

mandibular process

In head and face development, lower part and majority of pharyngeal arch 1 which forms the lower jaw (mandible) of the face Smaller upper part of pharyngeal arch 1 are the [#maxillary_process maxillary processes].

(More? Face Development | Face Abnormalities | Head Development)

mammary gland

A specialised modified secretory gland producing milk in female mammals for neonatal nutrition. Note that milk production and neonatal nutrition through milk, define us as mammals.

(More? Integumentary Development - Mammary Glands)

massive chronic intervillositis

(chronic intervillositis, chronic histiocytic intervillositis) Rare placental abnormality and pathology defined by inflammatory placental lesions, mainly in the intervillous space (IVS), with a maternal infiltrate of mononuclear cells (monocytes, lymphocytes, histiocytes) and intervillous fibrinoid deposition.

(More? Placenta Abnormalities)

maternal

Term relating to the mother and used genetically, biologically and legally. The term paternal relates to the father.

maternal passive immunity

(maternal passive immunity) Term used to describe the transfer of maternal antibodies to the fetus (through the placenta) and the neonate (through milk).

(More? Placenta | Normal Development - Milk)

maternal mortality rate

Statistical term defined as the number of maternal deaths per 100,000 live births.

(More? Statistics- Australian Maternal Statistics | Statistics - World Death)

Math1

(===M===ouse homolog of ===ATH1===, also called Atoh1) Basic helix-loop-helix (bHLH) transcription factor both necessary and sufficient for hair cell development in the mammalian cochlea.

(More? Hearing Development | OMIM ATONAL)

matrix

Term used to describe the non-cellular material in which cells are embedded, as in ===extracellular matrix===. The term matrix is also used in cell biology to describe the space within mitochondria, enclosed by the two mitochondrial membranes.

MAVS

Mitochondrial AntiViral Signaling, induces interferon expression and therefore increased antiviral defenses.

maxillary process

In head and face development, upper part of pharyngeal arch 1 which forms as a pair of small lateral swellings which contributes the upper jaw and forms the palatal shelves. Larger lower part of pharyngeal arch 1 is the [#mandibular_process mandibular process]. Associated abnormality is cleft palate/lip.

(More? Face Development | Face Abnormalities | Head Development)

measles

(paramyxovirus) A single-stranded RNA virus which is highly contagious. Before measles vaccination (USA 1963) more than 90% of children had an infection before puberty and in developing countries it is still a common and often fatal childhood disease. Pregnancy effects of measles results in a higher risk of premature labor, spontaneous abortion, low-birth-weight, and possibly rare cases of birth defects with no definable pattern of malformation.

(More? Viral Infection)

meatal plate

An ectodermal plug that temporarily blocks the external auditory meatus of the ear.

(More? Senses Notes)

meatus

(Latin, meatus = a channel or way) An anatomical description of an opening or passageway (external auditory meatus, female urethral meatus).

(More? Senses - Hearing)

meatoplasty

A surgical technique allowing reconstructive surgery of the external ear canal, often used to treat external meatus stenosis

(More? Ear Abnormalities)

Meckel's cartilage

A temporary cartilage located in the first pharyngeal arch (mandibular component) that forms the template for formation of the mandible and middle ear bones. Named after Johann Friedrich Meckel, the Younger a German anatomist (1781 - 1833).

(More? Head Notes | Who Named it? Johann Friedrich Meckel | PalaeosThe Gill Arches: Meckel's Cartilage )

meconium

The gastrointestinal contents that accumulate in the intestines during the fetal period. This material is a mixture of liver bile and glandular secretions, amniotic fluid, and cellular debris. Meconium is also used to describe the first postnatal rectal discharge from the neonate. Fetal stress in the third trimester or at parturition can lead to premature meconium discharge, into the amniotic fluid and ingestion by the fetus ([#meconium_aspiration_syndrome meconium aspiration syndrome]) and damage to respiratory function. Damage to placental vessels [#meconium_myonecrosis meconium myonecrosis] may also occur.

(More? Birth | Gastrointestinal Tract Notes | Respiratory Notes)

meconium aspiration syndrome

(MAS) Fetal stress in the third trimester, prior to/at/ or during parturition can lead to premature meconium discharge into the amniotic fluid and sunsequent ingestion by the fetus and damage to respiratory function. Damage to placental vessels [#meconium_myonecrosis meconium myonecrosis] may also occur.

(More? Birth | Gastrointestinal Tract Notes | Respiratory Notes)

meconium myonecrosis

Placental pathology resulting from prolonged meconium exposure which is toxic for myocytes of placental vessels (umbilical cord or chorionic plate).

(More? Placental Notes)

meconium peritonitis

(MP) A sterile chemical peritonitis resulting from small bowel perforation in utero. Often detected by ultrasound and can result in a mortality rate as high as 60%.

meconium plug syndrome

(functional immaturity of the colon) Term used to describe a transient disorder of the newborn colon, which is characterized by delayed passage of meconium (more than 24 to 48 h), intestinal dilatation and yellow/green vomiting. More common in premature infants and can be determined by radiological dye study.

(More? GIT Abnormalities | Gastrointestinal Tract Notes | Birth | PMID: 18485962 | U Mich - Meconium Plug Syndrome)

medial

(Latin, medialis = middle) Anatomically towards the midline of the body or structure. The opposite term is lateral.

medial epithelial seam

(MES) Embryonic structure formed by the fusion of the two palatal shelves, forming a two-layered medial edge epithelial seam, which is then lost with palate development.

(More? Face - Abnormalities | Face Notes | | Head Notes | Medline Plus - Cleft Lip and Palate)

mediastinum testis

(Latin, medialis = middle) A single conical mass of connective tissue within the testis (male gonad) which extends from the tunica albuginea (cortical thick capsule surrounding the testis) into the seminiferous tubule region (medullary). Embedded within this connective tissue are the rete testis component of the duct conduction system for spermatazoa (Spermatozoa Duct Pathway: seminiferous tubule ‚ straight tubule ‚ rete testis ‚ ductuli efferentes ‚ ductus epididymidis ‚ ductus deferens)

(More? Spermatogenesis)

median eminence

(Latin, medialis = middle) A midline pouch or recess in the floor of the third ventricle and an extension of the hypothalamus together with the neural stalk forms the infundibular stem, which in turn together with the posterior lobe forms the pituitary neurohypophysis.

(More? Endocrine - Hypothalamus | Endocrine - Pituitary )

medullary

(Latin, medialis = in the middle) Term relating to the medulla; pith, marrow, inner portion of an organ. Usually combined with cortex (cortical) meaning the outer layer.

medulloblast

An undifferentiated cell of the embryonic neural tube that can develop into either a neuroblast or spongioblast similar to a neural stem cell.

medulloblastoma

The most common malignant brain tumor in children (leading causes of cancer-related death in children under 9 years of age) and is thought to result from the transformation of granule cell precursors in the developing cerebellum. Approximately 25% of medulloblastoma cases have mutations in components of the Sonic hedgehog - Patched signaling pathway.

(More? Neural System - Abnormal Development | Molecular Development - Sonic hedgehog)

megalin

A transmembrane protein acts as an endocytic receptor on the apical surface of polarised epithelial cells. It requires interaction with another protein, cubulin, for the endocytosis of ligands. In development, it has been shown that sonic hedgehog can also bind megalin and this interaction now requires further research.

(More? Molecular Development - Sonic hedgehog | NCBI Bookshelf - Megalin)

megacolon

([I.htm#intestinal_aganglionosis intestinal aganglionosis], aganglionic colon, Hirschsprung's Disease) Gastrointestinal tract abnormality due to a lack of enteric nervous system (neural ganglia) in the intestinal tract responsible for gastric motility (peristalsis). In general, its severity is dependent upon the amount of the GIT that lacks intrinsic ganglia, due to an earlier developmental lack of neural crest migration into those segments.

(More? Gastrointestinal Tract Abnormalities | Neural Crest Abnormalities)

meiosis

The cell division that occurs only in production of germ cells where there is a reduction in the number of chromosomes (diploid to haploid) which is the basis of sexual reproduction. Note all other non-germ cells divide by mitosis.

(More? Week 1 Notes)

meiotic sex chromosome inactivation

(MSCI) The process of transcriptional silencing of the X and Y chromosomes that occurs only during male meiotic spermatogenesis. This is a specialised form of [#MSUC meiotic silencing of unsynapsed chromatin]. This specific silencing has also be called the second form of X chromosome inactivation, the first form occurs in all female embryo cells.

(More? Meiotic sex chromosome inactivation. Turner JM. Development. 2007 May;134(10):1823-31.)

meiotic silencing of unsynapsed chromatin

(MSUC) An aneuploidy protective mechanism for subsequent generations, during meiosis where chromosomes are silenced that fail to pair with their homologous partners.

melanocyte

A pigmented cell located in the skin, neural crest in origin. This cell type proliferates in the cancer melanoma.

(More? Neural Crest Notes)

melatonin

An endocrine hormone secretd from the pineal gland involved with the diurnal cycle, melatoinin levels are high in dark, low in daylight.

(More? Endocrine Notes | Pineal Gland)

membrana granulosa

The granulosa cells that line the developing follicles of the ovary. These cells proliferate to form the stratum granulosa and other granulosa cells are given specific names based upon their position within the follicle. In the antral follicle, membrana granulosa sits on the follicular basal lamina and lines the antrum as a stratified epithelium. The [C.htm#cumulus_oophorus cumulus oophorus] is a column of granulosa cells that attaches the oocyte to the follicle wall. The [C.htm#corona_radiata corona radiata] are the granulosa cells that directly surround the oocyte, and are released along with it at ovulation. Following ovulation the corona radiata provide physical protection to the oocyte and granulosa cells within the ovulating follicle contribute to [C.htm#corpus_luteum corpus luteum].

(More? Week 1 - Oogenesis)

meningococcal disease

(meningitis) Disease can be a viral or bacterial infection of cerebrospinal fluid of the spinal cord and brain. Treatment and outcomes differ for either viral (less severe, resolves without specific treatment) or bacterial (severe, may result in brain damage, hearing loss, or learning disability) infections.

(More? Abnormal Development - bacteria | Postnatal Development | CDC - meningococcal disease)

menopause

(Greek, mene = moon, men = month, pause = end or cessation) The decrease in ovarian production of estrogen and progesterone leading to cessation of menstrual cycles, decrease in fertility, and end of female reproductive life. Usually occurs in the mid-40's, the term was first used by the French physician, de Gardanne in 1812.

(More? Human Menstrual Cycle | Medline Plus - Menopause)

menorrhagia

Term used to describe heavy menstrual bleeding, is common in women of reproductive age (WHO data, affects 1011 out of 5322 women).

(More? Human Menstrual Cycle)

menstrual age

The gestation time calculated from the first day of the last menstrual period (LMP) prior to [F.htm#fertilization fertilization]. In humans, this differs from embryonic age by approximately two weeks.

(More? Week 1 Notes)

menstrual cycle

The human reproductive cycle, an endocrine regulated change in female anatomy and physiology that occur over 28 days (4 weeks, a lunar month) during reproductive life (between puberty and menopause). This cycle ceases during pregnancy and differs from other non-primate vertebrates (eg rats, mice, horses, pig) females that have a reproductive cycle called the estrous cycle (oestrous, British spelling).

(More? Human Menstrual Cycle | Estrous Cycle)

merle

The pattern of coloring observed in the coat of the domestic dog and is characterized by patches of diluted pigment. Dogs inherit trait in an autosomal, incompletely dominant fashion and heterozygous or homozygous for the merle locus exhibit a wide range of auditory and ophthalmologic abnormalities, similar to those in human Waardenburg syndrome.

(More? Animal Embryos | PNAS Article 2006)

meromelia

(Greek, melia = limb) A limb abnormality with the partial absence of a limb, as described in the original classical classification of limb deficiencies.

(More? Limb Abnormalities - Classification)

mesangial cell

(glomerular mesangial cell) A kidney epithelial cell type located in the nephron (functional kidney unit) surrounding glomerular capillaries (blood vessels). Mesodermal in origin, there are mesangial cells within (intraglomerular) and outside (extraglomerular) the glomerulus. Have several functions including: contractile activity (smooth muscle-like) controlling blood flow and basement membrane surface area (glomerular filtration rate), structural support, phagocytosis (remove basal lamina components and immunoglobulins).

(More? Nephron Notes)

mesencephalon

( mes = mid, encephalon = brain) The embryonic neural tube region that will form midbrain structures of the tectum and tegmentum in the adult brain. The mesencephalon is the middle of the 5 secondary brain vesicles formed from the mesencephalon of the primary brain vesicle (there are 3 primary brain vesicles). The mesencephalon lumen (cavity of the neural tube) will form the midbrain aqueduct.

(More? Neural Notes | Ventricular System)

mesenchyme

Term used to describe the cellular organisation of undifferentiated embryonic connective tissue . Mesenchymal tissue is mainly derived from mesoderm and neural crest, which will form most of the adult connective tissues. This connective tissue organization contrasts with the other main form of cellular organization, epithelial tissue.

(More? Musculoskeletal Notes)

mesenchymal stem cell

The cells derived from various connective tissues that form a population of stem cells with potential to differentiate for repair and replacement of connective and other tissues. Can be found mainly in bone marrow, but also in other places (dermis, lung and heart atria). The bone marrow mesenchymal stem cell (or bone marrow stromal cell) differs from the hematopoietic stem cell (which forms blood cells) and can form bone, cartilage and adipose tissue.

mesentery

The tissue fold attaching gastrointestinal tract to posterior abdominal wall in which blood vessels, lymph and nerves run. Developmentally derived from lateral plate mesoderm forming splanchnic mesoderm which then forms the posterior mesogastrium.

(More? [#mesogastrium mesogastrium] | GIT Notes)

mesethmoid cartilage

The ventral component of the nasal capsule. In the chicken embryo, it is induced by sonic hedgehog (Shh) expression from endoderm (endoderm zone I).

(More? Face Notes)

mesoderm

The middle layer of the 3 germ cell layers of the embryo. Mesoderm outside the embryo and covering the amnion, yolk and chorion sacs is extraembryonic mesoderm.

(More? Musculoskeletal Notes | Week 3 Notes)

mesogastrium

The developmental term for the splanchnic mesoderm forming early mesenteries (dorsal and ventral) that support the developing gastrointestinal tract. The majority of the ventral mesentery is developmentally lost at the level of the midgut and the dorsal mesentery remains in the adult, through which blood vessels, nerves and lymph connects to the gastrointestinal wall. Note that specific visceral organs also develop within each mesogastrium.

(More? GIT Notes)

mesonephros

The second temporary stage of kidney development (pro-, meso-, meta-). The intermediate mesonephros develops and disappears with the exception of its duct, the ===mesonephric duct===, which will form the male reproductive duct system. In males, the mesonephric tubules go on to form the ducts of the testis. In females, these degenerate. A few mesonephric tubules remain as efferent ductules in the male and vestigial remnants in the female.

(More? Urogenital Notes)

mesonephric duct

(= Wollfian duct) An early developing urogenital paired duct system that initially runs the length of the embryo, that will differentiate and form the male reproductive duct system (ductus deferens). In females, this duct degenerates occasionally some remnants may remain associated in broad ligament.

(More? Genital Notes)

mesorchium

A peritoneal fold attaching testes to the mesonephros during development.

(More? Genital Notes)

mesovarium

The mesentry of the ovary formed from a fold of the broad ligament that attaches the ovary.

(More? Week 1 Notes)

messenger RNA

(mRNA) The form of RNA that is translated into a protein amino acid sequence by the ribosome.

metanephros

The adult kidney, third stage of mammalian kidney (pro-, meso-, ===meta-===) development within the intermediate mesoderm.

(More? Urogenital Notes)

metanephric cap

In kidney development, the intermediate mesoderm ([#metanephric_mesenchyme metanephric mesenchyme]) which surrounds the ureteric bud and will develop into nephrons.

(More? Urogenital Notes)

metanephric mesenchyme

Metanephric mesenchyme caudal part of intermediate mesoderm that will develop into nephrons within the kidney. The intermediate mesoderm forms as an unsegmented strip running rostro-caudally between the somite and lateral plate mesoderm. The very caudal (tail) end of this mesoderm strip where the uteric bud forms is the metanephric mesenchyme, which induces the formation of, and surrounds the end of, the ureteric bud.

(More? Urogenital Notes)

metaphase

One of the 5 mitosis phases (prophase, prometaphase, metaphase, anaphase, and telophase). Originally based on light microscopy of living cells and electron microscopy of fixed and stained cells. At metaphase kinetochore microtubules align chromosomes in one midpoint plane. Metaphase ends when sister kinetochores separate.

(More? Week 1 Notes | Week 1 Mitosis)

metencephalon

(encephalon = brain) The embryonic neural tube region that will form hindbrain structures of the pons and cerebellum in the adult brain. The metencephalon is the fourth of the 5 secondary brain vesicles formed from the rhombencephalon of the primary brain vesicle (there are 3 primary brain vesicles). The metencephalon lumen (cavity of the neural tube) will form the fourth ventricle.

(More? Neural Notes | Ventricular System)

methionine aminopeptidase

(MetAPs) An enzyme family of cytosolic metalloproteases which are responsible for cleavage from nascent proteins (newly translated) of the initial methionine from the N termini. Eukaryotes express two forms of MetAPs (types 1 and 2), with type 2 required for normal vascular development, deletion in mouse causes embryonic death at the midsomite stage.

(More? Cardiovascular Notes)

methyldopa

(alpha methyldopa) A central alpha agonist used to lower blood pressure. Used as an antihypertensive drug to lower blood pressure in pre-eclampsia, acting by either a direct or indirect central vasodilatory mechanism. A recent study suggests this drug may have a direct effect on placental and/or endothelial cell function in pre-eclampsia patients, altering angiogenic proteins. Drug commercial brandname (USA) "Aldomet", also available in combination with other drugs: methyldopa and chlorothiazide "Aldochlor", methyldopa and hydrochlorothiazide "Aldoril".

(More? Placenta Abnormalities - Pre-eclampsia | Medline Plus - Methyldopa | Effect of antihypertensive therapy with alpha methyldopa on levels of angiogenic factors in pregnancies with hypertensive disorders. Khalil A, Muttukrishna S, Harrington K, Jauniaux E. PLoS ONE. 2008 Jul 23;3(7):e2766. PMID: 18648513)

metopic suture

A skull fibrous joint, cranial suture between adjacent developing bones of the skull. This suture begins at nose and runs superiorly to meet sagittal suture and fuses in early childhood before all other cranial sutures. Premature fusion (synostosis) of metopic suture causes Trigoncephaly (wedge skull).

(More? Skull Notes | Head Notes)

methylmercury

(organic mercury) Toxic form, at high concentrations, of mercury found in the environment (air, water, soil, plants and animals) and is different from elemental mercury (thermometers, dental amalgams). Industrial mercury can enter water systems, which is then converted into methylmercury and can contaminate exposed fish or shellfish, entering the human food chain.

(More? Abnormal Development - Heavy Metals)

MiRNA

Acronynm for [#MicroRNA MicroRNA] a small noncoding ribonucleotide-based (RNA) regulators of gene expression. They have diverse functions including regulation of cellular differentiation, proliferation and apoptosis.

microcephaly

An abnormally small skull cranium marked by premature fusion of the skull sutures and also under-developed brain.

microchimerism

(Mc) Term used to describe when a usually small population of cells or DNA is harbored by one individual that derive from a genetically distinct individual. May occur in pregnancy when cells exchange beween fetus and mother, mother and fetus or in twinning.

MicroRNA

(miRNA) a small noncoding ribonucleotide-based (RNA) regulators of gene expression. These recently discovered small RNA molecules (18-24 nucleotides) negatively regulate target mRNAs and appear to have a role in many developmental processes as well as in the adult. (See also "Dicer") There is also another class of small RNAs involved in gene expression present in cells, small interfering RNAs (siRNAs), generated from double-stranded RNA (dsRNA) precursors.

microtia

The condition of an abnormally small external ear.

(More? Abnormal Ear | Microtia)

midbrain

An early subdivision of the brain development at the stage when there are three primaryof the neural tube (forebrain, midbrain, hindbrain). (More? Neural Notes)

midbrain flexure

(pontine flexure) [P.htm#pontine_flexure pontine flexure] The middle curvature that forms in the early rapidly growing neural tube.

(More? Neural Notes)

midgut

The middle of the three part/division ([F.htm#foregut foregut] - ===midgut=== - [H.htm#hindgut hindgut]) of the early forming gastrointestinal tract. The midgut is initially connected on the ventral embryo surface to the external yolk sac by a yolk stalk, a narrow tubular connection. The midgut forms all the tract from beneath the stomach (duodenum, small intestine and large intestine) to the distral transverse colon. The midgut develops as an external loop "herniated" ventrally, until early fetal growth of the body wall recaptures this external loop, which also undergoes a rotation about the superior mesenteric artery to establish the adult anatomical position.

(More? Gastrointestinal Tract - Intestine | Gastrointestinal Tract Notes)

mifepristone

(RU 486) The commercial name for a progesterone receptor antagonist similar in structure to the natural hormone progesterone, which is used medically as a birth control drug.

(More? Birth Control)

miscarriage

The loss of embryo or fetus by spontaneous abortion.

misoprostol

A drug used in medical management of first trimester miscarriage, in some countries often in combination with [#mifepristone mifepristone]. Drug is a potential teratogen, used in non-pregnant treatment to prevent ulcers in people taking some arthritis or pain medicines.

(More? Medline Plus - misoprostol)

missed abortion

(blighted ovum) Term previously used to describe ===early fetal loss===, embryo loss in first trimester.

mitosis

The normal division of all cells, except germ cells, where chromosome number is maintained. Note germ cell division (egg, sperm) is reductive meiotic division.

(More? Week 1 Notes)

MMR

Acronym for ===M===easles-===M===umps-===R===ubella vaccine.

(More? Normal Development - Immunization | Abnormal Development - Rubella Virus)

modulo

Drosophila transcription factor which binds to the promoter of spermatid-differentiation gene Sdic and integrate meiosis and spermatid differentiation in the male germ line. (homologue of nucleolin)

(More? PNAS paper | OMIM nucleolin)

monozygotic twin

Twins (identical) produced from a single [F.htm#fertilization fertilization] event (one fertilised egg and a single spermatazoa, form a single zygote), these twins therefore share the same genetic makeup. Occurs in approximately 3-5 per 1000 pregnancies, more commonly with aged mothers. Late monozygotic twins can result in conjoined twins or both a shared placenta and a shared amniotic sac (monochorionic monoamniotic twins). Note dizygotic twins (fraternal) arise from separate fertilizations of different eggs.

(More? Twinning | Week 1 Twinning)

morphogenesis

Term used to describe the process of development involving a change in form (shape) and size or either cells or tissues.

morula

(Latin, morula = mulberry) An early stage in post-fertilization development when cells have rapidly divided to produce a solid mass of cells (12-15 cells) with a "mulberry" appearance. This stage is followed by formation of a cavity in this cellular mass ([B.htm#blastocyst blastocyst] stage). In humans, morula stage of development occurs during the first week following [F.htm#fertilization fertilization].

(More? Week 1 Notes | Week 1 Early Cell Division)

MIS

Acronym for [#Mullerian_Inhibiting_Substance Mullerian Inhibiting Substance], a hormone that regulates genital development.

MSC

Acronym for [#mesenchymal_stem_cell mesenchymal stem cell], a connective tissue stem cell.

MSH

Acronym for muscle specific homeobox (which is not muscle specific), a homeobox gene involved in pattern formation in several systems in development.

MSS

Acronym for Maternal Serum Screening, used to detect potential genetic abnormalities in both mother and embryo.

(More? Abnormal Development - Genetic)

Mullerian Duct

([P.htm#paramesonephric paramesonephric duct]) An embryonic paired duct system that will form the epithelial lining of female reproductive organs: utererine tube, [U.htm#uterus uterus], upper vaginal canal. This duct system degenerate in male gonadal development. Named after Johannes Peter Muller (1801-1858) a German scientist.

(More? [genitalXXuterus.htm Uterus Development] | [genitalXX.htm Genital System - Female] | [genitalX.htm X chromosome] | Human Menstrual Cycle | Genital Notes)

Johannes Peter Mullerian

Johannes Peter Muller (1801 - 1858) in 1830 was the first to describe the duct named after him, the "Mullerian duct" also called the paramesonephric duct.

(More? [genitalXXuterus.htm Uterus Development] | [genitalXX.htm Genital System - Female] | [genitalX.htm X chromosome] | Human Menstrual Cycle | Genital Notes)

Mullerian Inhibiting Substance

(MIS, Anti-Mullerian Hormone, AMH, Mullerian inhibiting hormone, MIH). A sertoli cell secreted glycoprotein (transforming growth factor-beta, TGF-beta superfamily) that regulates gonadal and genital tract development. The main role is to inhibit paramesonephric (Mullerian) duct development in males. Postnatally, after puberty it is also expressed in females by ovarian granulosa cells and has a role in follicle development.

(More? Male | OMIM - AMH)

multifetal pregnancy reduction

A procedure used to decrease the number of fetuses a woman carries and improve the chances that the remaining fetuses will survive and develop into healthy infants. Multifetal reductions that occur naturally are referred to as spontaneous multifetal reductions.

multiple birth

A pregnancy that results in the birth of more than one infant.

(More? Twinning Notes)

mutagen

A chemical or agent that can cause permanent damage to the deoxyribonucleic acid (DNA) in a cell. DNA damage in the human egg or sperm may lead to reduced fertility, spontaneous abortion (miscarriage), birth defects and heritable diseases.

muscle

Term used to describe the tissue that has contractile activity, also used to describe the functional cells that contract. There are three main types of muscle: smooth, cardiac and skeletal. Muscle is mesodermal in origin, each muscle type coming from a different mesoderm region.

(More? Musculoskeletal Notes)

Mycoplasma genitalium

M. genitalium A parasitic bacterium that can populate the epithelial layer of human uterine (Fallopian) tubes and lead to cilia damage and therefore contribute to [t.htm#tubal_factor_infertility tubal factor infertility]. A recent study has shown that M. genitalium can also bind to human spermatozoa, could be carried by motile sperm, and contribute to this process of female genital disease and infertility.

(More? Week 1 - Abnormalities)

myelomeningocele

(spina bifida) A neural tube defect, a form of spina bifida (developmental abnormalities leading to failure of closure of the spinal column). Can be of two forms: ===spina bifida occulta=== (spinal column fails to close, spinal cord and meninges remain in place and defect is covered by skin) ===meningoceles=== (tissue covering the spinal cord sticks out of the spinal defect but the spinal cord remains in place)

(More? Neural Abnormalities)

myelencephalon

(Greek, enkephalon = brain) The embryonic neural tube region that will form hindbrain structures of the medulla oblongata in the adult brain. The myelencephalon is the last vesicle before the spinal cord the fifth of the 5 secondary brain vesicles formed from the rhombencephalon of the primary brain vesicle (there are 3 primary brain vesicles). The myelencephalon lumen (cavity of the neural tube) will form the lower part of the fourth ventricle.

(More? Neural Notes | Ventricular System)

myoblast

The undifferentiated mononucleated muscle cells that will fuse together to form a multinucleated myotube, then mature into a muscle fibre.

(More? Musculoskeletal Notes)

myocardin

A protein that acts as a transcriptional co-activator of serum response factor (Srf), which is a regulator of both smooth and cardiac muscle gene expression.

(More? Heart Molecular | Creemers EE, Sutherland LB, McAnally J, Richardson JA, Olson EN. Myocardin is a direct transcriptional target of Mef2, Tead and Foxo proteins during cardiovascular development. Development. 2006 Oct 4)

MyoD

Myoblast determining factor, a transcription factor involved in the determination of muscle cells in the somite. A basic helix-loop-helix factor which binds DNA.

(More? Musculoskeletal Notes | Molecular Notes)

myogenesis

The process of muscle cell development or formation. In skeletal muscle the cellular sequence is: myoblast, myotube and myofibre.

(More? Musculoskeletal Notes | Molecular Notes)

myonecrosis

The term used to describe pathological death of myocytes. Can occur during development in placental vessels (umbilical cord or chorionic plate) following prolonged exposure to meconium (meconium myonecrosis).

(More? Placental Notes

myotendinous junction

(MTJ) The specialiazed junction between a skeletal muscle and the tendon which transmit the force of the muscle contraction to the bone of the skeleton. Their role is to transmit the force of the muscle contraction. The histology of tendons is that of a dense regular connective tissue high in collagen type I. During development the MTJ has a unique microenvironment.

(More? Ligament Tendon Notes | Ligament Tendon Notes)

myotome

The portion of the dermamyotome that generates skeletal muscle. Has 2 components epaxial (dorsal muscles) hypaxial (ventral muscles)

(More? Musculoskeletal Notes)

myxomatous

The term (histology/pathology) used to describe a connective tissue embedded in mucus, for example Wharton's jelly of the placental cord.

(More? Placenta Histology)

Comments

Use this page to access brief definitions of specific 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 this glossary list includes: texts listed on page 1 Reading of each notes section, Department of Anatomy Publications, WWW resources from NCBI, NIH, OMIM, NHMRC (Australia), AMA (USA), Office of Rare Diseases (USA), PubMed Medline Dictionaries, MSDS, Merck Manual home edn.

These notes are for Educational Purposes Only Please email Dr Mark Hill if you wish to make a comment about this current project.

Copyright: Dr Mark Hill Created: 01.06.1997 Updated: 11.05.2009

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