|Embryology - 1 Dec 2023 Expand to Translate|
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- Glossary: A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | Numbers | Symbols | Term Link
- General term for chemicals that may play a role in weight gain and obesity. An example of such a chemical class are "tributyltin" (TBT) containing the (C4H9)3Sn group, with a specific example being tributyltin oxide.
- Leptin hormone receptor found in many different tissues. Receptor belongs to class I cytokine receptor family. These act through intracellular JAKs (Janus kinases) and STATs (signal transducers and activators of transcription) pathways.
- A large protein (820 kDa) located in the contractile sarcomere of skeletal and cardiac muscle. The protein has several different structural domains (68 immunoglobulin domains, 2 fibronectin 3 domains, 1 calcium/calmodulin binding domain, 1 RhoGEF domain).
obstetric brachial plexus palsy
- (OBPP) Clinical condition detected in the newborn involves traction of the segmental spinal nerve roots C5 and C6, that in turn results in a weakness of shoulder function and elbow flexion. Additional involvement of segmental spinal nerve roots C7, C8 and T1 affects elbow extension and wrist and hand function.
- (More? PMID 22043309 )
- Childbirth injury caused by several days of obstructed labour without prompt medical intervention. Blood supply is interrupted to surrounding tissues (bladder or rectum) leading to tissue death generating a hole or fistula.
- (non-communicating hydrocephalus) A form of hydrocephalus that is caused by some visible blockage in the flow of cerebrospinal fluid. This blockage can be caused by: a mass (such as a brain tumor) in the brain which blocks the flow of fluid; scarring or malformation which narrows or completely blocks part of fluid flow. A common site for this obstruction is the narrow cerebral aqueduct. A non-obstructive hydrocephalus (communicating hydrocephalus) is the form with no visible blockage in the flow of cerebrospinal fluid.
- (More? neural)
obstructive renal pelvis defect
- (obstructive defects of the renal pelvis, uteropelvic junction obstruction, pelvo-uterero junction obstruction) Term describing a developmental renal abnormality due to partial or complete blockage of the drainage of the kidney pelvis requiring surgical correction. The blockage can also have several causes including: unusual ureter twisting or bending, ureter compression by a blood vessel, malformations of the muscular wall. The blockage leads to an accumulation of urine in the affected region, with several potential effects: nephron damage from compression (hydronephrosis); decreased urine output leading to lack of amniotic fluid (oligohydramnios); respiratory development effects due to the lack of amniotic fluid. The most common type of obstruction is at the uteropelvic junction (UPJ), between the junction of the ureter and the kidney. Blockage lower as the ureter enters the bladder, the ureterovesicular junction (UVJ), usually involves only one kidney and the back flow enlarges the affected ureter (megaureter).
- (More? renal)
- (pl, foramina) Anatomical term for the space created between the ischium and pubis bones of the pelvis through which nerves and muscles pass to the lower limbs. Adult male and female pelvises differ in several respects, one is that the obturator foramina are round in the male and oval in the female.
- (Latin, oestrus = gadfly, madness estrous cycle) The cyclic alterations in the animal female tract and in sexual receptivity related to hormone changes. When searching for related topics use the American (estrous cycle) and British (oestrous cycle) spellings, which are both used in the literature.
- A genetic evolutionary theory that suggests that the mammalian X chromosomes are conserved among species. Named after Susumu Ohno (大野 乾 (1928 – 2000) a Japanese-American geneticist and evolutionary biologist.
- Common name for children prenatally exposed persistent organic pollutants during 1978-1979 in the form of rice oil contaminated with polychlorinated biphenyls (PCBs) and their heat-degradation products, mainly polychlorinated dibenzofurans (PCDFs). Children of the exposed women were born with retarded growth, with dysmorphic physical findings, and, during development, with delayed cognitive development, increased otitis media, and more behavioral problems than unexposed children.
- (More? Persistent Organic Pollutants | Abnormal Development - Chemicals | Endocrine System - Abnormalities)
- A genetic abnormality of forearm with Duane syndrome of eye retraction. In humans, due to mutation in SALL4 gene on chromosome 20q13.13-q13.2.
- (More? PMID 12393809)
- Region of the brain that olfactory sensory neurons connect by the olfactory nerve, (cranial nerve I). Anatomically these neuronal axons pass through the cribriform plate region of the skull.
- Term used to refer to the sense of smell and related structures (olfaction, olfactory epithelium, olfactory bulb, olfactory nerve CN I, olfactory epithelium).
- The specialised sensory epithelium that lines the nasal cavity associated with smell. Some cells within the adult epithelium remain as stem cells which can be isolated and purified.
- (nasal placode) (placode - Greek, plax = "plate" or "scale", eidos = shape or form) Cranial region of thickened ectoderm that will generate the sensory olfactory epithelium of the nose required for smell.
- A term referring to a low volume of amniotic fluid, often measured by ultrasound. This condition is often associated with developmental abnormalities, such as renal development, and a poor perinatal outcome. The opposite condition, excess amniotic fluid volume, is called polyhydramnios.
- The brainstem cholinergic and GABAergic efferent system that innervates the sensory cells and the sensory neurons of the inner ear.
- A congenital gastrointestinal malformation, omphalocele with herniation of abdominal contents through the umbilicus, which can be covered by a membrane. Not to be confused with gastroschisis (para-umbilical hernia) or hypoplasia of abdominal muscles, skin-covered umbilical hernia.
- (vitelline duct, yolk stalk) The omphalomesenteric duct is a connection through the umbilicus between the yolk sac to the primitive gut that disappears at 8 to 9 weeks of gestation. Many developmental abnormalities are associated with failure of the vitelline duct to resorb, most commonly Meckel's diverticulum.
- (vitelline vein) Embryonic vessels providing the venous pole input into the heart from the yolk sac connected at the umbilicus.
- A clinical term referring to a new medical discipline bridging oncology and reproductive medicine in order to discover and apply new fertility preservation options for patients with fertility threatening diseases or treatments.
- (More? oocyte | ovary | Polycystic Ovary Syndrome | USA - Oncofertility Consortium | Australia - South Australia PDF | Australia - Victoria)
- (Greek, oo = egg, ovum) The term used to describe the haploid egg or ovum formed within the ovary (female gonad) and released to enter the uterine tube and be transported to the uterus. The mature oocyte is the cell released from the ovary during ovulation.
- (egg retrieval) A clinical in vitro fertilization (IVF) procedure to collect the eggs contained in the ovarian follicles.
- (Greek, oo = egg + genesis = origin, creation, generation) process of diploid oogonia division and differentiation into an haploid oocyte (egg) within the ovary (female gonad). Mammalian meiosis will only be completed within the oocyte if fertilization occurs.
- (More? oocyte | ovary | Histology Image - Oocyte | Lecture - Fertilization | Lecture - Genital Development)
- (Greek, oo = egg) diploid germ cells within the ovary (female gonad) which provide the primary oocytes for oocyte (egg) formation. In humans, all oogonia form primary oocytes within the ovary before birth.
- (zona pellucida, vitelline membrane, egg coat) An alternative term for the zona pellucida surrounding the oocyte.
- (Greek, oo = egg + phorus = carrying, egg-bearing) as in cumulus oophorus, used to describe the granulosa cells within the follicle that tether or link the oocyte to the wall of the follicle.
- (lens placode) In week 4 a pair of surface ectoderm placodes that fold in to form the lens vesicle that will form the adult lens (crystalline lens or aqua; Latin, aquula = a little stream) of the eye. The lens functions to focus light (with the cornea) upon the neural retina. The lens focusses by refracting light as it passes through the biconvex lens, which can be altered in shape (accommodation) by surrounding ciliary muscles. These ciliary muscles are activated (contracted) by parasympathetic innervation from the ciliary ganglion itself innervated by the oculomotor nerve (Cranial Nerve III) (More? Cranial Nerves).
- Early embryonic secondary brain vesicle transient structure occurring as a paired narrow neural tube-like extensions at the level of the diencephalon. This primitive connection is the route later taken by the retinal ganglion axons from the retina forming the optic nerve.
- (orchiometer) A simple clinical instrument used to measure postnatal testis volume using 12 beads ranging from 1 to 25 millilitres. Developed by Dr. Andrea Prader (1919 – 2001) an endocrinologist who also discovered the Prader-Willi syndrome and developed the Prader scale, a second clinical classification used to describe CAH virilization of female genitalia.
origin recognition complex
- (ORC) Six proteins (ORC1-6) that bind DNA replication origins to mark the competency for the initiation of DNA synthesis (DNA replication licensing factor). ORC4 has been shown to be associated with chromosomes extruded in both polar bodies during murine oogenesis.
organ of Corti
- The anatomical structure of the inner ear involved in converting mechanical vibrations into electrical signals in the cochlear ganglia (CNVIII).
- A group of cells that secrete factors that can change the fate of adjacent cells and instruct a specific pattern of development.
- (More? gastrulation)
- (embryonic period) In human development, this period of time corresponds to the first eight weeks (weeks 1 - 8) following fertilization when most organs are initially formed and also called the embryonic period. In other species this is also the initial period after fertilization, but will have a different overall time course.
- (More? Embryonic Development)
- The second portion of the pharynx (throat) that is posterior to the oral cavity. The other pharynx regions are the nasopharynx and laryngopharynx (hypopharynx).
- (More? respiratory)
- (Greek, orthos = straight or rigid, ptera = wing) Order of insects including grasshoppers, locusts, katydids and crickets. Grasshopper neural development has been used as models for mechanisms of neural development.
- (Ortolani maneuver) A clinical term to describe a physical examination of the newborn for developmental dysplasia of the hip (DDH). This is a test for posterior dislocation of the hip. Using the examiner's thumb, abduct the infant's leg, while using the examiner's index finger to place anterior pressure on the greater trochanter. A positive sign is a distinctive 'clunk' which can be heard and felt as the femoral head relocates anteriorly into the acetabulum, usually becomes negative after 2 months of age. This test is combined with the Barlow test (maneuver). Named after Marino Ortolani, the test developer in 1976.
- (More? Musculoskeletal System Development | Postnatal Development | Screening for developmental dysplasia of the hip: recommendation statement PMID 16510673)
- (OSX) A transcription factor that has been shown to be essential for bone formation. Osterix structure contains three Cys2-His2 zinc-finger DNA-binding domains at its C terminus.
- The most common form of arthritis that occurs after birth, caused by the accumulated wear of the cartilage in joints that disrupts the normal function of the joint, causing pain and functional limitations. The condition affects mainly the hands, spine, and weight-bearing joints such as the hips, knees and ankles.
- The mesenchymal stem cell that form an osteoprogenitor cell differentiate to an osteoblast that form the cellular component of bone and produce the bone matrix. Osteoblast mature to form osteocytes. Pluripotent mesenchymal stem cells are the common mesenchymal progenitor for several different cell types including: osteoblasts, chondroblasts, muscle, bone marrow stromal cells and adipocytes. Osteoblasts express alkaline phosphatase, collagens and non-collagen bone matrix proteins (osteocalcin) and hormone receptors (PTH, 1,25-dihydroxyvitamin D3, estrogen, glucocorticoids).
- The most common benign bone tumor occuring mainly at the metaphyseal region of the long bones. The tumor is slow-growing and painless, forming a cartilage-capped bony outgrowth on the surface of the bone in children and adolescents.
- Cells that remove bone (bone resorption) by enzymatically eroding the bone matrix deposited by an osteocyte. These cells are blood cell (monocyte-macrophage) in origin and fuse to form a multinucleated osteoclast. These cells allow continuous bone remodelling and are also involved in calcium and phosphate metabolism. The erosion cavity that the cells lie within and form is called a resorptive bay or Howship's lacuna. Osteoclasts express a number of proteolytic Matrix MetalloProteinases (MMPs) including MMP-9, MMP-10, MMP-12 and MMP-14.
- (More? bone | Cardiovascular System - Blood Development | Histology Image - Osteoclast | Lecture - Musculoskeletal Development | Practical - Bone Development)
- The mature bone-forming cell, which are the cellular component of bone and produce bone matrix. These cells differentiate from osteoprogenitor cells, the mesenchymal stem cells, that first differentiate to osteoblasts that secrete bone matrix. In compact bone, individual osteocytes are organised in circular columns separated by layers of bone matrix forming part of the osteon or Haversian system. The deposited bone matrix is remodeled and removed by osteoclast cells.
- (Haversian system) The term used to describe the histological and micro-anatomical unit structure (principal structure) of compact bone. Consists of a central cavity surrounded by lamellar bone matrix within which osteocytes reside. The central cavity or canal (Haversian canal) contains blood vessels for osteocyte nutrition and nerves for sensation.
- (More? bone | Bone Histology | Lecture - Musculoskeletal Development | Practical - Bone Development)
- The mesenchymal stem cell that form differentiate to an osteoblast that form the cellular component of bone and produce the bone matrix. Osteoblast mature to form osteocytes. Pluripotent mesenchymal stem cells are the common mesenchymal progenitor for several different cell types including: osteoblasts, chondroblasts, muscle, bone marrow stromal cells and adipocytes.
- (Osx) An osteoblast-specific transcription factor required for osteoblast differentiation, which inhibits the Wnt pathway activity.
- (primary opening, first opening) In early heart development during atrial septation, the initial septum primum is incomplete leaving this initial opening between the left and right atria. Later the septum primum begins to degenerate forming a second opening, the ostium secundum.
- (secondary opening, second opening) In early heart development during atrial septation, the initial septum primum begins to degenerate forming this second opening between the developing left and right atria.
ostium secundum atrial septal defect
- (secundum atrial septal defect) Term describing a cardiac abnormality due to due to partial or complete failure closure of the atrial embryonic blood shunt bypassing the pulmonary system. The interatrial septum has an enlarged opening at the location of the foramen ovale and the ostium secundum.
- The fluid in the middle ear accompanied by signs and symptoms of ear infection. Common developmental problem, prolonged or repeated occurance can lead to developmental delay in learning, speech and even damage to the middle ear structures.
- (otocyst) The sensory otic placode forming as a pair on the surface of the developing head, which sinks into mesoderm to form spherical vesicle (stage 13/14 embryo) that will form the membranous labyrinth (cochlea, semi-circular canals) and cranial nerve (CN VIII) components of the inner ear.
otoacoustic emission testing
- (OAE) The basis of a simple infant hearing test of the inner ear. A small probe containing both a speaker producing "clicks" and a microphone to detect cochlea responses is placed inside the ear canal. Acoustic energy produced by vibration of the hair cells in response to the clicks is detected by the microphone within the probe. A more complex test that can be used at an earlier stage is the automated auditory brainstem response.
- (otic vesicle) The sensory otic placode forming as a pair on the surface of the developing head, which sinks into mesoderm to form spherical vesicle (stage 13/14 embryo) that will form the membranous labyrinth (cochlea, semi-circular canals) and cranial nerve (CN VIII) components of the inner ear.
- (statoconium, otoconium) A calcium carbonate concretion found within the otolitic membrane of the utricle and saccule in the vestibular portion of inner ear, that functions with balance.
- The extracellular matrix that cover the sensory epithelia of the inner ear. This membrane within the utricle and saccule contain embedded hair cell cilia and small crystalline bodies of calcium carbonate (otoliths) that functions to detect head motion.
- (auditory tube, eustachian tube, pharyngotympanic tube) A narrow canal connecting the middle ear space to the back of the oral cavity. The tube allows ventilation, protection and clearance for the middle ear cavity. Ventilation is the pressure equalization in the middle ear. Clearance is to allow fluid drainage from the middle ear. Embryonic origin is from the first pharyngeal pouch. In development, the canal is initially both horizontal, short and very narrow leading to poor drainage and easy blockage.
- The paired type homeobox gene identified in many species which has a role in early head and brain development.
- (More? OMIM - Otx2)
outer hair cells
- (OHCs) Within the cochlea, the three rows of hair cells that function to increase basilar membrane motion through a local mechanical feedback process within the cochlea, the "cochlear amplifier".
outer pillar cells
- Within the cochlea, cells arranged in rows and form a boundary between the single row of inner hair cells and three rows of outer hair cells.
outer submucous plexus
- (OSP, Meissner's plexus, plexus submucosus externus , Schabadasch plexus) A gastrointestinal tract intrinsic neral network, that is one of the two (inner and outer) lying within the submucosa involved in intestinal secretion and gut motility in large mammals. Smaller animals have only a single submucous plexus.
- A cause of infertility due to problems with egg production by the ovaries.
- The female reproductive structural unit located in the ovary and formed by a number of different cell types. The primordial germ cell (oocyte), the surrounding support cells (granulosa cells) and the hormone secreting cells (thecal cells). The ovarian follicle goes through a number of classified structural and growth changes with development (primordial follicle, preantral follicle, antral follicle). Note there are a number of different follicle classifying/description systems and clinically development can be determined by ultrasound analysis of antral follicle development.
ovarian hyperstimulation syndrome
- (OHSS) Condition associated with fertility drugs used for in vitro fertilization and other reproductive abnormalities. The drugs stimulate follicular development and oocyte maturation, there are no agreed standards for reporting this condition. Australian data shows "OHSS occurred in 0.8% of cycles that involved an oocyte retrieval with the incidence of OHSS increasing with the number of oocytes collected" (Wang YA, Chambers GM, Dieng M & Sullivan EA 2009. reproductive technology in Australia and New Zealand 2007 Assisted reproduction technology series no. 13. Cat. no. PER 47. Canberra: AIHW).
- (More? Assisted Reproductive Technology | Medlineplus - OHSS | Assisted reproductive technology in Australia and New Zealand)
- The use of ultrasound and/or blood or urine tests to monitor ovarian follicle development and hormone production.
- (ovarian reserve markers) Clinical term describing the ability for follicular development in ovaries in response to gonadotropins. This reserve value is relevant for fertility and in vitro fertilization treatments and a number of different ovarian reserve serum and ovarian markers have been identified: baseline follicle stimulating hormone (FSH) levels, baseline anti-Müllerian hormone (AMH) levels, and antral follicle count (AFC). In addition, with reproductive aging there is seen both a quantitative and a qualitative reduction of the primordial follicle pool available.
ovarian reserve markers
- See ovarian reserve
- Clinical term for the use of drugs to stimulate the ovaries to develop ovarian follicles or eggs (oocytes).
- The two female gonads where female germ cells (oocytes, eggs) are generated and also the source of estrogen and progesterone the female hormones regulating secondary sex characteristics and menstrual cycle uterine changes. The ovary is embryonically formed from primordial germ cells entering region of the paired mesonephric ducts (Wolffian ducts) which are lost in females.
- (uterine horn, fallopian tube, oviduct, salpinx) see uterine tube. A pair of tubular structures designed to transport the oocyte (egg) from the ovary to the uterus body.
- (Astacin-Like Metalloendopeptidase, ASTL) An oocyte enzyme (zinc-dependent metalloprotease) involved in altering zona pellucida structure, following fertilisation by cleaving zona pellucida glycoprotein (ZP2) at 166LA↓DE169.
- (Graafian follicle) The most hormonally sensitive and developed antral follicle that is released by ovulation each menstrual cycle.
- The term used to describe the process of the mature follicle releasing the oocyte or ovum (and support cells) from the ovary surface into the peritoneal cavity. In humans, generally a single oocyte is released from a cohort of several maturing follicles. More than one follicle may be released (superovulation) following reproductive therapeutic treatment.
- (oocyte, egg) Term used to describe the oocyte. Note historically this term was used (inaccurately) to also describe the conceptus at early periods of post-fertilization development.
- (oxycephalus = "tower skull") A developmental skull defect resulting from premature coronal suture synostosis. One of the several different forms of skull deformity (scaphocephaly, oxycephaly, plagiocephaly, trigoncephaly) caused by premature fusion (synostosis) of different developing skull sutures.
- (Greek, "quick birth") An 8 amino acid peptide hormone released from the maternal posterior pituitary, involved in initiation and maintenance of birth labor by acting on the uterine myometrium.
- (More? birth)
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. and WHO ART terminology (2009).
These notes are for Educational Purposes Only Please email Dr Mark Hill if you wish to make a comment about this current project.
- Glossary: A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | Numbers | Symbols | Term Link
Cite this page: Hill, M.A. (2023, December 1) Embryology O. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/O
- © Dr Mark Hill 2023, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G