G

UNSW Embryology Glossary G

Link to the Original UNSW Embryology Glossary G

G0

The state of a cell that has withdrawn from the cell cycle.

(More? Week 1 Notes)

G1

The period of the cell cycle that occurs after the completion of mitosis and before the beginning of DNA replication; also called the first growth phase.

(More? Week 1 Notes)

G2

The period of the cell cycle that occurs between the completion of DNA synthesis and before the beginning of mitosis (of the next cell cycle).

(More? Week 1 Notes)

galactorrhoea

An inappropriate milk production. Term is not used in relation to postnatal lactation where excess milk may be produced. Condition can occur in association with an anterior pituitary tumour producing prolactin (hyperprolactinemia).

(More? Endocrine Development - Pituitary | Normal Development - Milk)

galactosemia

An enzyme deficiency disorder. The enzyme galactose-1-phosphate uridyl transferase metabolizes galactose in milk sugar.

(More? Prenatal Diagnosis | Neonatal Screening | MedlinePlus - Galactosemia)

gall bladder

The septum transversum differentiates to form the hepatic diverticulum and the hepatic primordium, these two structures together will go on to form different components of the mature liver and gall bladder. In the adult, the gall bladder is a site of bile salt storage and concentration, to then be released into the small intestine where they act to solubilize dietary lipids by their detergent effect. Bile salts are a cholesterol derivative (breakdown product).

(More? Gastrointestinal Tract - Gall Bladder | Liver Notes | Gastrointestinal Tract Notes)

gametes

(Greek, gamos = marriage) A specialized reproductive cell through which sexually reproducing parents pass chromosomes to their offspring; a sperm or an egg.

(More? Week 1 Notes)

gamete intrafallopian transfer

see GIFT

(More? In Vitro Fertilization Notes)

gameteogenesis

The production of either the haploid germ cells of spermatazoa (male) or eggs (female)

(More? Week 1 Notes)

gametophyte

The haploid form of a life cycle characterized by alternation of generations.

(More? Week 1 Notes)

gamma

Greek letter, ( capital letter gamma; lower case gamma) the lower case form used in scientific literature to designate different forms/variants of a similar protein, gene, energy form or substance.

(More? [greek.htm Greek Symbols])

gamma radiation

(Greek letter Γ capital letter gamma; γ lower case gamma) electromagnetic radiation or light emission of frequencies produced by sub-atomic particle interactions which can be either mutagenic (DNA damage) or can cause serious cellular damage when absorbed by living cells.

(More? Abnormal Development - Radiation)

ganglion

The antomical ball formed by a group of peripheral neuron cell bodies (plural ganglia).

Gartner's duct

A female developmental abnormality caused by the persistance of the mesonephric duct (normally lost in females) when the ureteric bud fails to separate from the mesonephric duct. Can generate a broad ligament or vaginal cyst. Named after Hermann Treschow Gartner (1785-1827) a Danish surgeon and anatomist.

(More? Genital Abnormalities)

gastrointestinal tract

(GIT) The digestive tube extending from the oral cavity (mouth) to the anus. The digestive system includes the associated organs, which may also have other functions.

(More? GIT Notes)

gastroschisis

(omphalocele, paraomphalocele, laparoschisis, abdominoschisis, abdominal hernia) A developmental abnormality, which occurs as an abdominal wall defect associated with evisceration of the intestine.

(More? GIT Abnormalities | Feldkamp ML, Carey JC, Sadler TW. Development of gastroschisis: Review of hypotheses, a novel hypothesis, and implications for research. Am J Med Genet A. 2007 Jan 17)

gastrosplenic ligament

(gastrolienal ligament, ligamentum gastrosplenicum) Structure derived from the dosal mesogastrium (mesentery) connects the spleen to the stomach as part of the greater omentum.

(More? Spleen | GIT Notes)

gastrula

(Greek, gastrula = little stomach) A stage of an animal embryo in which the three germ layers have just formed.

(More? Gastrulation)

gastrulation

The process of differentiation forming a gastrula. Term means literally means "to form a gut" but is more in development, as this process converts the bilaminar embryo (epiblast/hypoblast) into the trilaminar embryo ([E.htm#endoderm endoderm]/mesoderm/ectoderm) establishing the 3 germ layers that will form all the future tissues of the entire embryo. This process also establishes the the initial body axes.

(More? Gastrulation)

GATA3

One of the GATA-binding protein family of zinc-finger transcription factors (recognize a consensus sequence known as the 'GATA' motif) involved in many aspects of embryo development. Expressed in white adipocyte precursors prior to diifferentiation and also to have a role in regulation of skin development through lipid biosynthesis.

(More? Integumentary Development | JCB - Skin Development | OMIM - GATA3)

GATA4

one of the GATA-binding protein family of zinc-finger transcription factors (recognize a consensus sequence known as the 'GATA' motif) involved in many aspects of embryo development. GATA4 and GATA6 activity interact to regulate gene expression in the developing cardiovascular system.

(More? Cardivascular Notes | Cardivascular Molecular | PNAS - Cardivascular Development | OMIM - GATA4)

GBS

see [#GroupBStreptococcus Group B Streptococcus]

gene

A DNA sequence that is transcribed as a single unit and encodes a single polypeptide (protein) or a set of closely related polypeptides. There are approximately 20,000-25,000 protein encoding genes in the human genome. In each cell, DNA is found within the nucleus and also within mitochondria.

(More? DNA Notes)

genetics

The science of studying genes.

(More? DNA Notes)

genitalia

(Latin, genitalia = ) The term used to describe either the external or internal male and female sexual and reproductive organs.

(More? Urogenital Notes)

genital ridge

(= gonadal ridge) The thickened epithelial/mesenchymal region adjacent and medial too the mesonephros. Primordial sex cells migrate into this region to form the indifferent gonad. These undifferentiated gonads have a cortex and a medulla. Female ===XX=== chromosome complex, cortex differentiates into an ovary, and medulla regresses. Male ===XY=== complex, medulla differentiates into a testis and cortex regresses.

(More? Urogenital Notes)

genital tubercle

A prominence or rounded protuberance extending ventrally at the inferior end of the body of the embryo. It has initially a sexually indifferent external genitalia structure and contributes to either male (glans penis) and female (clitoris) external genitalia.

(More? Urogenital Notes)

genome

The collection of all the DNA in an organism.

(More? DNA Notes)

genomic imprinting

Epigenetics, expression of imprinted genes is monoallelic and dependent upon the parents sex (parental imprinting), in contrast most genes (which are non-imprinted) have biallelic expression. This is an heritable change that does not alter DNA sequence.

(More? Week 1 Notes)

genotype

The genes present in a particular organism or cell.

germ layers

The first three cellular layers (ectoderm, mesoderm, and endoderm) that will form all tissues of the embryo. In humans, these layers begin to form during week 3 of development. Term should not be confused with germ cells, which are the oocyte and spermatazoa forming cells. Term originally used by Robert Remak (1815 - 1865), a German scientist and embryologist.

(More? Week 2 Notes Week 3 Notes | Robert Remak | Development Week by Week) 

germinal epithelium

The cuboidal epithelium component covering surface of ovary, it is continuous with mesothelium covering mesovarium. Note that it is a historical misnomer, as it is was thought to be the site of germ cell formation, but is a covering epithelium with no role in primordial follicle formation.

(More? Week 1 - Oogenesis)

Germinal Matrix-Intraventricular Haemorrhage

(GM-IVH) in preterm infants most common form (up to 20% of preterm infants, less than 32 weeks gestation) of intracranial bleeding (haemorrhage).

(More? NZ National Women's Health GM-IVH)

germination

(Latin, germinare = to sprout) the resumption of growth by a seed.

gestation

The period of time from conception to birth. A pregnancy with multiple fetuses is referred to as a multiple gestation.

gestational age

The clinical term to describe human development timed from the last menstrual period (LMP) and therefore differs by approximately two weeks from research materials timed from fertilization.

(More? Development Week by Week)

gestational carrier

A woman who carries an embryo that was formed from the egg of another woman; the gestational carrier is expected to return the infant to its genetic parents.

gestational sac

A fluid-filled structure that forms within the [U.htm#uterus uterus] early in pregnancy. In a normal pregnancy, a gestational sac contains a developing fetus.

Gestational Trophoblastic Disease

mainly as a Hydatidiform Mole, (though there can be non-hydatidiform forms) tumour with "grape-like" placental appearance without enclosed embryo formation, arises mainly from a haploid sperm fertilizing an egg without a female pronucleus.

(More? Week 1 Abnormalities | Week 2 Abnormalities)

gestational trophoblastic neoplasia

(GTN) The development of the trophoblastic cell not containing an embryo, hydatidiform mole, which can be benign or malignant. Due to the continuing presence of the trophoblastic layer, this abnormal conceptus can implant in the [U.htm#uterus uterus].

(More? Week 2 Abnormalities)

ghrelin

(Greek, leptos = thin) a polypeptide hormone produced in the gastrointestinal tract (stomach) that stimulates release of growth hormone from the anterior pituitary. Hormone which probably has a role in regulating appetite and energy balance.

(More? Endocrine Other Endocrine Notes | Meier U, Gressner AM. Endocrine regulation of energy metabolism: review of pathobiochemical and clinical chemical aspects of leptin, ghrelin, adiponectin, and resistin. Clin Chem. 2004 Sep;50(9):1511-25.

GHRH

Arconym for Growth Hormone Releasing Hormone, secreted by the Hypothalamus it is a protein that activates Growth Hormone synthesis and release from the pituitary.

(More? Endocrine Notes - Hypothalamus)

GIFT (gamete intrafallopian transfer)

A procedure that involves removing eggs from a woman's ovary, combining them with sperm, and using a laparoscope to assist in placing the unfertilized eggs and sperm into the woman's fallopian tube through small incisions in her abdomen. (More? Week 1 Notes)

glial cell

A cell within the nervous system that does not itself transmit electrical and chemical signals, but which provides metabolic and structural support for neurons. There are many different types of glial cells.

(More? Neural Notes)

glycodelin

a glycoprotein secreted from different tissues and in several glycosylated forms, it is a member of the lipocalin superfamily. Glycodelin-A is released from endometrial glands (into the uterine space) under progesterone regulation. Glycodelin from the placenta has an apparent immunosuppressive activity.

Globozoospermia

also called round-headed spermatozoa, is a human infertility syndrome caused by spermatogenesis defects leading to a malformed or absent sprematazoa acrosome. The acrosomal reaction being a key component of sperm [F.htm#fertilization fertilization] of the egg.

(More? Week 1 Abnormalities | OMIM - Globozoospermia)

glottis

(Greek, = larynx) the boundary between pharynx to the larynx and consists of the vocal folds and their associated intervening space.

(More? Gastrointestinal Tract Notes | Respiratory Notes)

glucagon

A protein hormone produced in the pancreas; a signal for the postabsorptive state; glucagon inhibits glycogen synthesis and stimulates its breakdown into glucose.

glycocalyx

(Greek, glykos = sweet + Latin, calix = cup), also called the cell coat. A densely staining zone just out-side most eukaryotic cells.

glycolysis

(Greek, glykys = sweet, referring to sugar + Iyein = to loosen) A set of ten chemical reactions that is the first stage in the metabolism of glucose.

goitre

(goiter) The enlargement of thyroid gland due to a dietry deficiency of iodine, or thyroid hormone level abnormalities. Iodine is required to synthesise thyroid hormone which in turn is required for normal neurological development.

(More? Abnormal Development - Iodine Deficiency | Endocrine Development - Thyroid)

golgi apparatus

(Golgi complex) The cytoplasmic organelle within eukaryotic cells, involved in protein processing for the cellular processes of exocytosis (secretion) and endocytosis (absorbtion). The organelle consists of a set of membrane flattened discs, usually near the nucleus. In spermatazoa, the golgi apparatus apparatus is modified to form the acrosome.

gonad

(Greek, gonos = seed) A gamete-producing (germ cell) organ. A non-sexual term which is used to describe both the female ovary and male testis.

(More? Week 1 Notes)

gonadotrophin releasing hormone

(Greek, gonos = seed) (GnRH) Hormone released from hypothalamus that stimulates pituitary gonadotropin synthesis and secretion ([L.htm#luteinizing_hormone luteinizing hormone, LH] and [F.htm#follicle_stimulating_hormone follicle stimulating hormone, FSH]). The cyclic release of GnRH has been shown to differentially affect gonadotropin release (rapid frequency, more than 1 pulse / hour LH; slower frequencies FSH secretion).

(More? Week 1 Notes | Marshall JC, Eagleson CA, McCartney CR. Hypothalamic dysfunction. Mol Cell Endocrinol. 2001 Oct 25;183(1-2):29-32. Review.)

granulosa cell

A specific cell type that proliferates in association with the oocyte within the developing follicles of the ovary. These cells form the follicle stratum granulosa and are also given specific names based upon their position within the follicle. In the antral follicle, [M.htm#membrana_granulosa membrana granulosa] sits on the [F.htm#follicular_basal_lamina 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 corpus luteum.

(More? Week 1 - Oogenesis | [week1_3d.htm Corpus luteum])

greater omentum

Splanchnic mesoderm peritoneal fold extending from the greater curvature of the stomach and hanging ventrally down "like an apron" in the peritoneal cavity over the small intestine. It forms initially in the embryo and fetus as a loop of the dorsal mesentery, which later fuses to form a single sheet attached to the posterior body wall. The [L.htm#lesser_omentum lesser omentum] is a smaller ventral peritoneal fold extending from lesser curvature of the stomach to liver.

(More? GIT Notes)

Greek Symbols

These symbols are used in scientific literature to designate different forms/variants of a similar protein or gene.

(More? [greek.htm Greek Symbols])

Gremlin

A 184-amino acid protein and bone morphogenic protein (Bmp) antagonist expressed during limb development in a region anterior to the zone of polarising activity (ZPA). Recent studies suggest that it acts as a signaling intermediate between sonic hedgehog (Shh) and fibroblast growth factor (Fgf). Belongs to the BMP antagonist gene family as Cerberus (head-inducing factor) and DAN (tumor suppressor)

(More? Musculoskeletal Notes - Limb Development | OMIM - Gremlin)

Gridlock

(grl) Name given to a zebrafish mutant and the related protein which generates cardiovascular system defects. The subsequent gene protein product "gridlock" is a transcription factor which has a role in determining artery/vein fate of lateral posterior mesoderm precursor cells.

(More? Blood Vessel | Zhong TP, Childs S, Leu JP, Fishman MC. Gridlock signalling pathway fashions the first embryonic artery. Nature. 2001 Nov 8;414(6860):216-20.)

growth hormone

(GH) A peptide hormone, made in the anterior pituitary, that stimulates tissue and skeletal growth.

(More? Endocrine Notes - Pituitary)

growth hormone releasing hormone

(GHRH) secreted by the hypothalamus it is a protein that activates Growth Hormone synthesis and release from the pituitary.

(More? Endocrine Notes - Hypothalamus)

Group B Streptococcus

(GBS) common bacteria in lower intestine of healthy adults (10 - 35%) also found in the vagina (13%) Women infected with no symptoms "colonized". This bacteria can also cause overwhelming infection and death.

growing pains

An intermittent aches or pains in legs that occur in the evening or at night occuring in children aged 3-12 years and may also occur during puberty growth.

(More? Child- Normal Development)

guanine

(guanine triphosphate) one of the 4 types (ATC===G===) of nucleotides that make up DNA. Base pairs with cytosine by 3 hydrogen bonds.

(More? DNA Notes)

Guthrie test

A newborn blood screening tes carried out for a variety of known genetic disorders. Blood is collected using a heel prick and spotted onto a test sheet to dry for later testing.

(More? Neonatal Screening)

gynecologist

(Greek, gyne = woman) doctor specializing in treating diseases of female reproductive organs.

gynecomastia

(Greek, gyne = woman, mastos = breast) is the excessive development of the male breast, which can occur transiently in puberty or due to other (hormonal) abnormalities.

(More? Integumentary Development - Mammary Glands)

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

UNSW CRICOS Provider Code No. 00098G