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UNSW Embryology

Glossary G

© Dr Mark Hill (2007)


G0 The state of a cell that has withdrawn from the cell cycle.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 represents the gap between the completion of mitosis and the beginning of DNA replication; also called the first growth phase. (More? Week 1 Notes)

G2 The period of the cell cycle that represents the gap between the completion of DNA synthesis and the beginning of mitosis (of the next cell cycle). (More? Week 1 Notes)

galactorrhoea 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 enzyme deficiency disorder. The enzyme galactose-1-phosphate uridyl transferase metabolizes galactose in milk sugar. (More? Prenatal Diagnosis | Neonatal Screening | MedlinePlus - Galactosemia)

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? Week 1 Notes)

gameteogenesis The production of sperm and eggs (More? Week 1 Notes)

gametophyte The haploid form of a life cycle characterized by alternation of generations. (More? Week 1 Notes)

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 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)

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

gastrulation The process of forming a gastrula. Term means "to form a gut" but implies more in development of the embryo. (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 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 the term used to describe either the external or internal male and female sexual organs. (More? Urogenital Notes)

genital ridge (= gonadal ridge) thickened region adjacent and medial to 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 in the second and third week of development, the first three cellular layers (ectoderm, mesoderm, and endoderm) that will form all tissues of the embryo. Named originally by Robert Remak (1815 - 1865) a German scientist and embryologist. (More? Week 2 Notes Week 3 Notes | Robert Remak)

germinal epithelium cellular component covering surface of ovary, it is continuous with mesothelium covering mesovarium. Note that it is a historical misnomer, as it is not the actual site of germ cell formation.

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 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 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) 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 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. (More? Neural Notes)

glottis (Greek, = larynx) the boundary between pharynx to the larynx. (More? Gastrointestinal Tract 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) 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 also called the Golgi complex in eukaryotic cells, a set of flattened discs, usually near the nucleus, involved in the processing and export of proteins.

gonad (Greek, gonos = seed) A gamete-producing organ; an ovary or testis. (More? Week 1 Notes)

greater omentum the stomach has 2 peritoneal folds attached to each of the stomach curvatures. The greater omentum is the peritoneal fold extending from the greater curvature of the stomach to the colon, and hanging down over the small intestine. The lesser omentum is the peritoneal fold extending from lesser curvature of the stomach to liver. (More? GIT Notes)

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)

growth hormone (GH) A peptide hormone, made in the anterior pituitary, that stimulates tissue and skeletal growth. (More? Endocrine Notes - Hypothalamus)

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 intermittent aches or pains in legs that occur in the evening or at night occuring in children aged 3-12 years and may reoccur during puberty growth. (More? Child- Normal Development)

guanine (guanine triphosphate) one of the 4 types (ATCG) of nucleotides that make up DNA. Base pairs with cytosine by 3 hydrogen bonds. (More? DNA Notes)

Guthrie test blood screening carried out on neonate (newborn) for a variety of knowm genetic disorders. Blood is collected using a heelprick 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)

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External Resources

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About Glossary

Notes 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.


Dr Mark Hill

Use this page to access specific terms listed alphabetically.

In addition, there is another index (now slightly out of date) which also lists all Notes pages.

Please email Dr Mark Hill if you wish to make a comment about this current project.

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