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Glossary Links

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 | Original 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)

obscurin

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 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)

oestrous 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.

(More? Menstrual Cycle - Estrous Cycle | Mouse estrous cycle)

Okihiro syndrome

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)

olfactory bulb

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.

(More? Senses Smell | Senses Notes)

olfactory

Term used to refer to the sense of smell and related structures (olfaction, olfactory epithelium, olfactory bulb, olfactory nerve CN I, olfactory epithelium).

(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)

olivocochlear

The brainstem cholinergic and GABAergic efferent system that innervates the sensory cells and the sensory neurons of the inner ear.

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, yolk stalk) 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 yolk sac connected at 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 uterus. The mature oocyte is the cell released from the ovary during ovulation.

(More? 2009 Lecture - Cell Division and Fertilization | 2009 Lecture - Genital Development | Week 1 - Oogenesis)

oocyte retrieval

(egg retrieval) A clinical in vitro fertilization (IVF) procedure to collect the eggs contained in the ovarian follicles.

(More? Week 1 - In Vitro Fertilization)

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 fertilization occurs.

(More? 2009 Lecture - Cell Division and Fertilization | 2009 Lecture - Genital Development | 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? 2009 Lecture - Cell Division and Fertilization | 2009 Lecture - Genital Development | 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)

organogenic period

(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)

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)

osteoarthritis

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.

(More? 2009 Lecture - Musculoskeletal)

osteoblast

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).

Differentiation Pathway: osteoprogenitor cells - osteoblasts - osteocyte

(More? 2009 Lecture - Musculoskeletal | Medicine Practical - Bone Development | 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 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.

Differentiation Pathway: mesenchymal stem cell (blood) - monocyte - osteoclast

(More? 2009 Lecture - Musculoskeletal | 2009 Bone Development Practical | Musculoskeletal Development - Bone | Cardiovascular System - Blood)

osteocyte

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.

Differentiation Pathway: osteoprogenitor cells - osteoblasts - osteocyte

(More? 2009 Lecture - Musculoskeletal | 2009 Practical - Bone Development | Musculoskeletal Development - Bone)

osteon

(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? 2009 Lecture - Musculoskeletal | 2009 Practical - Bone Development | Musculoskeletal Development - Bone)

osteoprogenitor cell

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.

Differentiation Pathway: osteoprogenitor cells - osteoblasts - osteocyte

(More? 2009 Lecture - Musculoskeletal | Medicine Practical - Bone Development | Musculoskeletal Development - Bone)

osterix

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

(More? 2009 Lecture - Musculoskeletal | 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? 2009 Lecture - Hearing | Senses Notes | Hearing Abmnormalities)

otic vesicle

(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.

(More? 2009 Lecture - Hearing | Organs of Audition and Equilibrium | Senses Notes)

otocyst

(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.

(More? 2009 Lecture - Hearing | Organs of Audition and Equilibrium | Senses Notes)

otolith

(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.

(More? 2009 Lecture - Hearing | Organs of Audition and Equilibrium | Senses Notes)

otolithic membrane

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.

(More? 2009 Lecture - Hearing | 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? 2009 Lecture - Hearing | 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 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".

(More? 2009 Lecture - Hearing)

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.

(More? 2009 Lecture - Hearing)

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 follicle

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.

(More? 2009 Lecture - Cell Division and Fertilization | 2009 Lecture - Genital Development | Week 1 - Oogenesis | Human Menstrual Cycle)

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. Assisted reproductive technology in Australia and New Zealand 2007. Assisted reproduction technology series no. 13. Cat. no. PER 47. 
Canberra: AIHW).

(More? Week 1 - In Vitro Fertilization | Medlineplus - OHSS | reproductive technology in Australia and New Zealand 2007)

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 reserve

(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

ovarian stimulation

Clinical term for the use of drugs to stimulate the ovaries to develop ovarian follicles or eggs (oocytes).

(More? 2009 Lecture - Cell Division and Fertilization | 2009 Lecture - Genital Development | 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? 2009 Lecture - Cell Division and Fertilization | 2009 Lecture - Genital Development | Week 1 Notes | Week 1 - Oogenesis)

oviduct

(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.

(More? 2009 Lecture - Cell Division and Fertilization | 2009 Lecture - Genital Development | 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? 2009 Lecture - Cell Division and Fertilization | 2009 Lecture - Genital Development | 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 )

Glossary 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. 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 Links

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Cite this page: Hill, M.A. (2024, May 3) Embryology O. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/O

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