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UNSW Embryology Glossary O

Link to the Original UNSW Embryology Glossary O

OB-R

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.

(More? leptin)

obstetric fistula

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. (More? End Fistula Organisation)

Okihiro syndrome

abnormality of forearm with Duane syndrome of eye retraction. In humans, due to mutation in [S.htm#Sall4 SALL4] gene on chromosome 20q13.13-q13.2.

(More? Kohlhase J, Heinrich M, Schubert L, Liebers M, Kispert A, Laccone F, Turnpenny P, Winter RM, Reardon W. Okihiro syndrome is caused by SALL4 mutations. Hum Mol Genet. 2002 Nov 1;11(23):2979-87.)

olfactory

Refers to the sense of smell.

(More? Senses Smell | Senses Notes)

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.

(More? Senses Smell | Senses Notes | Stem Cell Notes)

omphalocele

a congenital malformation 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.

(More? GIT Abnormalities)

omphalocele

a congenital malformation 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.

(More? GIT Abnormalities)

omphalomesenteric artery

(vitelline artery) An embryonic artery carrying blood to the yolk sac from the embryo.

(More? Heart Notes)

omphalomesenteric duct

(vitelline duct) 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.

(More? GIT Abnormalities | GIT Movies | Pubmed omphalomesenteric duct malformations)

omphalomesenteric veins

(vitelline veins) Embryonic vessels providing the venous pole input into the heart from the umbilicus.

(More? Heart Notes)

oocyte

(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 [U.htm#uterus uterus]. The mature oocyte is the cell released from the ovary during ovulation.

(More? Week 1 - Oogenesis)

oogenesis

(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 [F.htm#fertilization fertilization] occurs.

(More? Week 1 - Oogenesis)

oogonia

(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.

(More? Week 1 - Oogenesis)

oophorus

(Greek, oo = egg + phorus = carrying, egg-bearing) cumulus oophorus, used to describe the granulosa cells within the follicle that tether or link the oocyte to the wall of the follicle.

(More? Week 1 - Oogenesis)

oropharynx

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 Notes)

Orthoptera

(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.

(More? Other Embryos)

osteoblast

The mesenchymal cells that first differentiate to form the cellular component of bone and produce bone matrix. Osteoblast mature to form [#osteocyte 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).

(More? Musculoskeletal Development - Bone)

osteochondroma

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.

(More? Musculoskeletal Development - Bone)

osteoclast

Cells that remove bone (bone resorption) by enzymatically eroding the bone matrix. 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 iwithin and form is called Howship's lacuna. Osteoclasts express a number of proteolytic Matrix MetalloProteinases (MMPs) including MMP-9, MMP-10, MMP-12 and MMP-14.

(More? Musculoskeletal Development - Bone |http://embryology.med.unsw.edu.au/Notes/heart20.htm Cardiovascular System - Blood])

osteocyte

The mature bone-forming cell, which form the cellular component of bone and produce bone matrix. These cells differentiate from [#osteoblast osteoblasts], mesenchymal cells that first differentiate to initially form bone.

(More? Musculoskeletal Development - Bone)

osteon

The anatomical (histological) unit structure (principal structure) of compact bone.

(More? Musculoskeletal Development - Bone)

Osterix

(Osx) osteoblast-specific transcription factor required for osteoblast differentiation, which inhibits the Wnt pathway activity.

(More? Bone Development | Molecular Development)

otitis media

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.

(More? Senses Notes | Hearing Abmnormalities)

otocyst

(= otic vesicle) the sensory otic [P.htm#placode placode] which sinks into mesoderm to form spherical vesicle (stage 13/14 embryo) that will form components of the inner ear.

(More? Organs of Audition and Equilibrium | Senses Notes)

otolith

A calcium carbonate concretion in the vestibular portion of inner ear, involved with balance.

(More? Organs of Audition and Equilibrium | Senses Notes)

otopharyngeal tube

(auditory tube, eustacian 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.

(More? Middle Ear | Hearing Notes | Abnormal Hearing Notes)

Otx2

The paired type homeobox gene identified in many species which has a role in early head and brain development.

(More? OMIM - Otx2)

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.

(More? Gastrointestinal Tract Notes)

ovarian factor

A cause of infertility due to problems with egg production by the ovaries.

(More? Week 1 - Oogenesis)

ovarian hyperstimulation syndrome

(OHSS) Condition associated with fertility drugs for in vitro fertilization and other reproductive abnormalities.

(More? Week 1 - In Vitro Fertilization | Medlineplus - OHSS)

ovarian monitoring

The use of ultrasound and/or blood or urine tests to monitor ovarian follicle development and hormone production.

(More? Week 1 Notes | Week 1 - Oogenesis)

ovarian stimulation

The use of drugs to stimulate the ovaries to develop follicles/eggs. (More? Week 1 - Oogenesis | Human Menstrual Cycle)

ovary

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.

(More? Week 1 Notes | Week 1 - Oogenesis)

oviduct

(uterine horn, fallopian tube, oviduct, salpinx) see [#uterine_tube uterine tube]. A pair of tubular structures designed to transport the oocyte (egg) from the ovary to the [U.htm#uterus uterus] body.

(More? Week 1 - Oogenesis | Week 1 Notes | Blue Histology - Female Reproductive System)

ovulation

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.

(More? Week 1 - Oogenesis | Week 1 Notes)

oxycephaly

(oxycephalus, "tower skull")Skull defect resulting from premature coronal suture synostosis. One of several skull deformities (scaphocephaly, oxycephaly, plagiocephaly, trigoncephaly) caused by premature fusion (synostosis) of different developing skull sutures.

(More? Skull Notes | Head Notes)

oxytocin

(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 myometrium.

(More? Normal Development - Birth | Birth Overview )

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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