dactyly
(Greek, daktulos = finger or digit) used as a siffix with words describing limb abnormalities associated with either fingers on the hand or toes on the foot. For example, polydactyly is an abnormality resulting in additional fingers or toes. (More? Limb Abnormalities)
damaged DNA-binding protein
(DDB) two proteins (DDB1 and DDB2) that form a complex which recognizes ultraviolet-damaged (UV) DNA and begins repair process (nucleotide excision repair, NER). This complex has been shown to be required for (mouse) epidemis and hair follicle development. (More? Skin Notes | OMIM - DDB1 DDB2| Cang Y, Zhang J, Nicholas SA, Kim AL, Zhou P, Goff SP. DDB1 is essential for genomic stability in developing epidermis. Proc Natl Acad Sci U S A. 2007 Feb 14)
acronym for Dosage sensitive sex reversal (DSS), Adrenal hypoplasia congenita (AHC) critical region on the X chromosome, gene 1 , (gene NR0B1) is a nuclear hormone receptor involved in female ovary development. (More? Urogenital Notes | OMIM Entry DAX1)
DAZL
acronym for DAZ-like due to homology to DAZ (Deleted in AZoospermia), a gene on the long arm of the Y chromosome that is frequently deleted in infertile men with nonobstructive azoospermia. (More? Spermatogenesis | OMIM Entry DAZL)
DDB
acronym for damaged DNA-binding protein complex. This complex, consisting of two proteins DDB1 and DDB2, recognizes ultraviolet-damaged (UV) DNA and begins repair process (nucleotide excision repair, NER). Required for (mouse) epidemis and hair follicle development. (More? damaged DNA-binding protein | Skin Notes)
decidua
(Latin, decidua = a falling off) name given to the uterine endometrium following implantation and signaling which transforms the uterine stromal cells (fibroblast-like). (More? Placental Notes | Week 2 Notes | Endocrine Notes | Genital Notes)
decidua basalis
name given to the uterine endometrium at the site of implantation where signaling transforms the uterine stromal cells (fibroblast-like) into decidual cells. This forms the maternal component of the placenta, the decidualization process gradually spreads through the remainder of the uterus, forming the decidua parietalis. (More? Placental Notes | Week 2 Notes | Endocrine Notes | Genital Notes)
decidua capsularis
name given to the uterine endometrium which has been converted to decidua surrounding the conceptus on the smooth chorion side. (More? Placental Notes | Week 2 Notes | Endocrine Notes | Genital Notes)
decidua parietalis
name given to the remainder of the uterine endometrium, away from the site of implantation, that gradually becomes comverted to decidua. (More? Placental Notes | Week 2 Notes | Endocrine Notes | Genital Notes)
decidual cell
uterine stromal cells (fibroblast-like) that differentiate in response to both steroid hormones (progesterone) and embryonic signals. These cells then alter uterine environment to support further embryonic development as well as producing cytokines related to prolactin (PRL) and have an innate immune function. (More? Placental Notes | Week 2 Notes | Endocrine Notes | Genital Notes)
decidualization
process by which uterine stromal cells differentiate in response to both steroid hormones and embryonic signals into large epitheliod decidual cells. This process is essential for the progress of implantation and establishing fetal-maternal communication. (More? Placental Notes | Week 2 Notes | Endocrine Notes)
delta cell
pancreatic cells that secretes somatostatin. (More? Endocrine Development - Pancreas | Endocrine Notes | Gastrointestinal Notes)
Delta-like ligand
(Dll) one of two (Delta and Serrate family) plasma membrane (transmembrane) ligands for the Notch family of receptors. Vasular endothelial growth factor (VEGF) induces one form (Dll4) to acting in negative feedback regulatoion to prevent excessive blood vessel formation (More? Cardiovasular - Blood Vessel | Molecular Development- Vascular Endothelial Growth Factor | OMIM - Dll4)
Delta-like ligand (Dll) 4
Delta-like ligand (Dll) 4, a transmembrane ligand for the Notch family of receptors, ... Dll4 is induced by VEGF as a negative feedback regulator and acts to prevent overexuberant angiogenic sprouting
dendrite
neuronal processes that bring signals towards the neurons cell body (soma). (More? Neural Notes)
dentin phosphophoryn
(DPP) is part of dentin sialophosphoprotein (DSPP) synthesized in both mesenchyme and epithelium, involved in two developmental processes: epithelial-mesenchymal interactions and branching morphogenesis.
DES
Diethylstilbestrol or diethylstilbetrol, a drug prescribed to women from 1938-1971 to prevent miscarriage in high-risk pregnancies. Acts as a potent estrogen (mimics natural hormone) and therefore a potential endocrine disruptor. Female fetus, increased risk abnormal reproductive tract and cancer. Male fetus, abnormal genitalia. Banned by USA FDA in 1979 as a teratogen, previously used as livestock growth promoter. (More? Abnormal Development)
DET
acronym for D double-Embryo Transfers, two embryos transferred when women undergo Assisted Reproduction Technology compared to single-embryo transfer (SET). (More? Week 1 - In Vitro Fertilization)
DNA
acronym for DeoxyriboNucleic Acid. The genetic material found in mammalian chromosomes and mitochondria. Consisting of 4 nucleic acids (ATCG) that combine in a triptych (3 nucleotide) code for protein amino acids (3nt=1aa). (More? DNA Notes)
DNA duplex
double stranded base-paired DNA forming a helix. (More? DNA Notes)
dermatoglyphic
line patterns (ridges) on the skin found on the palms of the hands (finger and palm prints) and soles of the feet. (More? Skin Notes)
dermomyotome
dorsolateral half of each somite that forms the dermis and muscle. Paraxial mesoderm forms the somite which segregates into scleretome and dermomyotome, which will further divide into dermis (connective tissue) and myotome (developing muscle).
diabetes insipidus
disease due to inadequate production of AntiDiuretic Hormone (ADH). (More? Endocrine- Pancreas)
diabetes mellitus
disease due to inadequate production of insulin. (More? Endocrine- Pancreas | Maternal Diabetes)
Diabetes Type 1
the pancreas does not make insulin. (More? Endocrine- Pancreas | Maternal Diabetes | Medline - Diabetes Type 1))
Diabetes Type 2
noninsulin-dependent diabetes, where body does not respond correctly to insulin a life-long disease marked by high levels of sugar in the blood. (More? Endocrine- Pancreas | Maternal Diabetes | Medline - Diabetes Type 2)
diamniotic
a twinning term, having two amniotic sacs which can occur in both early and late monozygotic twinning. In a monozygotic twinning event (one fertilised egg and a single spermatazoa, form a single zygote) which occurs early (within 2 days of fertilization) where each embryo then develops separately its own chorionic sac (placenta) and amnionic sacs (dichorionic diamniotic). Later splitting (more than 2 days after fertilization) may result in a shared placenta and only duplication of the embryonic amnionic sacs (monochorionic diamniotic twins). (More? Monozygotic Twinning | Twinning | Week 1 Twinning)
diastema
a toothless region found in mice between the incisor and the first molar. Thought to result from murine evolutionary loss of incisor, canine, and premolars. (More? Mouse Notes)
Dicer
a 21 nucleotide small regulatory RNA required in RNA interference and small temporal RNA (stRNA) pathways to produce the active small RNA component that represses gene expression. (More? Cartilage Notes | Molecular Development | OMIM - DICER | Pubmed Review)
dichorionic
twinning term, in a monozygotic twinning event (one fertilised egg and a single spermatazoa, form a single zygote) which occurs early (within 2 days of fertilization) where each embryo then develops separately its own chorionic sac (placenta) and amnionic sacs (dichorionic diamniotic). Later splitting (more than 2 days after fertilization) may result in a shared placenta and only duplication of the embryonic amnionic sacs (monochorionic diamniotic twins). (More? Monozygotic Twinning | Twinning | Week 1 Twinning)
the caudal portion of forebrain after it divides into 2 parts in the 5 secondary vesicle brain (week 5) the cavity being the developing 3rd ventricle. Forms the thalmus and other nuclei in the adult brain.
diaphragm
muscular sheet separating chest from abdomen with several different embryoic origins: the septum transversum provides the tendon of the diaphragm, 3rd to 5th somite provide the musculature of diaphragm, ventral pleural sac provides connective tissue, mesentry of oesophagus provides the connective tissue around oesophasus and IVC, and pleuroperitoneal membranes provide the connective tissue around central tendon. Regular contraction of the diaphragm is required in respiration. (More? Respiratory Development - Diaphragm | Respiratory Notes | Musculoskeletal Notes)
differentiation
development of specific cell types from stem cells by gene activation and repression.
diffusion
(Latin, diffundere = to pour out) Random movements that lead to a uniform distribution of molecules both within a solution and on the two sides of a membrane.
dihydrotestosterone
the hormonally active form of testosterone (male sex hormone) produced by enzyme (5-alpha reductase) conversion. In the male embryo, this can occur in the genital skin which then supports external genital development. In the adult, this conversion occurs in a number of different tissues. A known treatment for prostate cancer include 5-alpha reductase inhibitors. (More? Urogenital Notes | Endocrine Notes )
dioscorea bulbifera
a plant, the "air potato" which contains the steroid diosgenin used historically for progesterone synthesis. (More? Human Menstrual Cycle - Birth Control)
(Greek, di = double + ploion = vessel) Having two sets of chromosomes. (More? Week 1 Notes)
diverticulum
(Latin, diverticulum = by-road) blind tubular process, also used to describe a sac or pouch in organ or seen in the colon. Occurs often in development when a new structure is forming from a epithelia or tract branch or in the initial/early stages of an epitheilal-mesenchymal interaction. The plural term is diverticula. Can also be found in normal and abnormal adult anatomical structures. (More? Developmental Mechanism - Epithelial Mesenchymal Interaction | GIT Abnormalities - Meckel's Diverticulum)
dizygotic twins
twins resulting from two fertilization events, that is involving two seperate ova and sperm. (More? Abnormalities - Twinning | Week 1 - Twinning)
Dolly
the name given to the first cloned sheep (1996) generated from an adult mammary gland cell. The name "Dolly" came from Dolly Parton a play on the mammary cell association. (More? Week 1 - Cloning)
gene determining phenotype, allelic pair is therefore resessive.(More? DNA Notes)
With autosomal dominant inheritance, there is an error in one of the 22 chromosome pairs. But the damaged gene dominates over the normal gene received from the other parent. If one of the parents has a disease caused by an autosomal dominant gene, all the children will have a 50 per cent risk of inheriting the dominant gene and a 50 per cent chance of not inheriting it. The children who do not inherit the damaged dominant gene will not themselves suffer from the disease, nor will they be able to pass the gene on to future children. This type of inheritance is present for example in Huntington's disease.(More? DNA Notes)
An embryo formed from the egg of a woman who has donated it for transfer to a woman who is unable to conceive with her own eggs (the recipient). The donor relinquishes all parental rights to any resulting offspring. (More? Week 1 Notes)
(French, dormire = to sleep) Referring to a stage in the development of a seed, in which growth is suspended until restarted by environmental cues.
Major embryonic blood vessel lying in the splanchnic mesoderm running the length of the embryo, begins as a pair of dorsal aortas which fuse to form a single vessel. Will eventually form the descending thoracic aorta. (More? Heart Notes)
(drg = spinal ganglia) sensory ganglia derived from the neural crest lying laterally paired and dorsally to the spinal cord (in the embryo found ventral to the spinal cord). Connects centrally with the dorsal horn of the spinal cord. (More? Neural Crest Notes)
DTPa
acronym for Diptheria-Tetanus-acellular Pertussis vaccine. (More? Normal Development- Immunization)
vitelline blood vessel lying within the liver that connects (shunts) the portal and umbilical veins with the inferior vena cava and also acts to protect the fetus from placental overcirculation. Absence can cause hydrops fetalis and the umbilical vein then drains directly into the inferior vena cava or right atrium. (More? Cardiovascular Notes)
(Latin, duodenarius = twelve, due to approximate length of 12 finger-widths) First part of small intestine lying between the end of the stomach (pyloric valve) and the jejunum. (More? Gastrointestinal Tract Notes)
ductal plate
a mesenchymal structure in the developing liver that is remodelled to generate the intrahepatic bile ducts (IHBD). Developmental abnormalities, "ductal plate malformation", arise from failure to reorganise. (More? Gastrointestinal Tract Notes - Liver Development)
ductuli efferentes
testis (male gonad) series of tubular structures which arise from the rete testis and conduct spermatazoa into the ductus epididymidis. Their columnar epithelium lining consisting of both absorptive and ciliated cells (giving rise to "cogwheel appearance) which removes much of the fluid associated with the spermatazoa leaving the testes (also by the upper epididymis) thereby increasing the spermatazoa concentration. (Spermatozoa Duct Pathway: seminiferous tubule → straight tubule → rete testis → ductuli efferentes → ductus epididymidis → ductus deferens) (More? Spermatogenesis | Genital - Male | Genital Notes)
ductus arteriosus
a prenatal vascular "shunt" which connects the left pulmonary artery and the descending aorta. Postnatal neonatal patency (patent ductus arteriosus, PDA) is a relatively common congenital cardiac anomaly occurring more frequently in premature infants. (More? Cardiovascular System Development | Cardiovascular Abnormalities)
ductus epididymidis
(epididymidis) male testes tubular structure which arise from the ductuli efferentes and conduct spermatazoa into the ductus deferens (vas deferens). The long duct is lined by a tall pseudostratified columnar epithelium. (More? Genital - Male | Genital Notes)
(Latin, dura mater = hard mother) tough outer connective tissue meningial coat of central nervous system. (overlays arachnoid and piamater layers) Duramater at the level of the spinal cord is separated from the periosteum of the vertebral canal by an epidural space. (More? Neural Notes | Axial Skeleton Notes)
dynorphin
full biological function unknown, 2 possibilities. In development, neuroendocrine regulation of the developing hypothalamo-pituitary-adrenal (HPA) axis. Secondly, a potential endogenous opioid peptide which has a high affinity for the kappa-opioid receptor. (More? Endocrine Notes)
dysmenorrhoea
period pain which can be primary (increased sensitivity to the prostaglandins) or secondary (pathological), can be common with no associated abnormality or in association with ovarian cysts or endometriosis. (More? Human Menstrual Cycle)
dysraphism
(Greek, rhaphe = suture) term used to describe defective fusion of neural folds. (More? Neural Abnormalities | Neural Notes | Neural Tube Defects)
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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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