P

UNSW Embryology Glossary P

Link to the Original UNSW Embryology Glossary P

p

a prefix combined with a number to indicate a protein of a specific molecular size (mass). Often given initially if no specific "name" has been given to the protein, see examples in the following entries.

p16

a cell cycle protein in mammals that suppresses G1-Cdk activity in G1 and is frequently inactivated in cancer. Belongs to a class of Cdk inhibitory proteins. Nomenclature is p for protein and 16 is molecular size (16,000 daltons).

(More? Week 1 Mitosis | OMIM Entry for p16)

p53

(recently renamed tp53) A cell cycle related transcription factor that promotes transcription of genes that induce cell cycle arrest or apoptosis in response to DNA damage or other cell stresses. This tumor suppressor gene is mutated in about half of all human cancers. Nomenclature is t for tumor, p for protein and 53 is molecular size (53,000 daltons).

(More? Week 1 Mitosis | OMIM Entry for p53)

p63

a p53 related transcription factor and is essential for the development of stratified epithelia. p63 acts as a "master regulator" controlling stratified epithelial development program, through induction of downstream signals important for epithelial function. Nomenclature is ===p=== for protein and ===63 ===for the molecular size (63,000 daltons).

(More? Reference: R.A. Ihrie etal., Perp Is a p63-Regulated Gene Essential for Epithelial Integrity See also : OMIM Entry for p63)

palatal rugae

(rugae palatinae) The transvere ridges forming on the secondary palate which are also sequentially added during development as the palate grows. Their number and arrangement on the hard palate of mammals is species specific. Along with the teeth and the tongue these ridges function in the process of mastication.

(More? Face Notes | Face - Abnormalities | Head Notes | Medline Plus - Cleft Lip and Palate)

palate

The roof of the mouth (oral cavity) a structure which separates the oral from the nasal cavity. Develops as two lateral palatal shelves which grow and fuse in the midline. Initally a primary palate forms with fusion of the maxillary processes with the nasal processes in early face formation. Later the secondary palate forms the anterior [H.htm#hard_palate hard palate] which will ossify and separate the oral and nasal cavities. The posterior part of the palate is called the soft palate (velum, muscular palate) and contains no bone. Abnormalities of palatal shelf fusion can lead to [C.htm#cleft_palate cleft palate].

(More? Face - Abnormalities | Face Notes | Head Notes | Medline Plus - Cleft Lip and Palate)

palatogenesis

The process of palate formation, divided into primary and secondary palate development.

(More? Face - Abnormalities | Face Notes | Head Notes | Medline Plus - Cleft Lip and Palate)

pancreas

The gastrointestinal tract associated organ with both exocrine (pH change and digestive enzyme secretion) and endocrine (hormone secretion) functions. In humans, the pancreas develops at the foregut/midgut junction (the septum transversum) and initially form connected to the gastrointestinal tract as two pancreatic buds (dorsal and ventral endoderm) which later fuse to form a single organ. The pancreas exocrine function (alkylate acidic stomach contents and amylase protein digestion) begins mainly fter birth. The endocrine function (alpha cell - glucagon, delta cell - somatostatin, beta cell - insulin) can be measured from 10 to 15 weeks onward.

(More? Gastrointestinal Tract - Pancreas | Endocrine Development - Pancreas)

pancreatitis-associated protein -III

(PAP-III) a macrophage chemoattractant, implicated in nerve regeneration as it has been shown to be induced and released from injured nerves. Journal of Neuroscience Paper

Paneth cell

a differentiated cell type cell within the gastrointestinal system epithelium. Paneth cells are located at the bottom of crypts of Lieberkühn in the small intestine. Their role is to control of infections by release of several antibacterial substances, including lysozyme. Paneth cell differentiation and positioning is apparently controlled by the developmental signaling protein Wnt.

(More? Gastrointestinal Tract Notes | Molecular Notes | Wnt7a)

Panton-Valentine leucocidin toxin

(PVL) produced by about 2% of Staphylococcus aureus (S aureus) bacteria, occurs very rarely and can be fatal in neonates.

(More? Abnormal Development - Bacterial Infection)

PAPP-A

acronym for [#PAPPA pregnancy-associated plasma protein-A]. Protein produced by both embryo and placenta during pregnancy. Maternal serum concentrations are related to subsequent fetal growth and it is thought to have several different functions, including preventing recognition of the fetus by the maternal immune system.

(More? [#PAPPA pregnancy-associated plasma protein-A])

paramesonephric duct

(also called [M.htm#Mullerian_duct Mullerian duct]) (Greek, para = "beside") The paired ducts that lie beside the [M.htm#mesonephric_duct mesonephric ducts], that will differentiate in the female embryo to form the female internal genital tract (uterine tubes, [U.htm#uterus uterus], upper vaginal canal).

(More? Urogenital Notes)

paranasal sinuses

Air-filled cavities surrounding the nasal cavity and open into it, which combine in function to: reduce skull weight, produce mucus, and act as resonating chambers affecting voice quality. Located within in the frontal, maxilae, ethmoid, and sphenoid bones with the same name as the bones in which they are located.

(More? Respiratory Notes)

parathyroid hormone-related protein

(PTHrP) A protein hormone produced by many fetal tissues and with a number of different functions including endochondral bone development, tooth development, and mammary gland epithelial-mesenchymal developmental interaction. Also suggested to have an autocrine role in lung development.

(More? Parathyroid Notes | Respiratory Notes)

paraxial mesoderm

The two lateral strips of mesoderm lying beside the axial mesoderm (notochord). This mesoderm at the body level will segment into [S.htm#somite somites], at the head level it remains unsegmented.

(More? Musculoskeletal Notes | Week 3 Notes)

parenchyma

(Greek, enkeim = "to pour in") Term used to describe the cells forming the functional cells of an organ or tissue. These cells carry out the function of the organ at a cellular level. Within the organ, the other population of cells, [S.htm#stroma stroma], are structural cells, connective tissue, the non-cellular extracellular matrix.

parietal pleura

Serous membrane which forms the outer lining of pleural cavity. Mesoderm of the thoracic cavity body wall and derived from epithelia of pericardioperitoneal canals from intraembryonic coelom. The inner pleural layer, visceral pleura, is splanchnic mesoderm in origin.

(More? Respiratory Notes)

Parkinson's disease

(paralysis agitans, shaking palsy) A postnatal neurological disease of the central nervous system, typically in ageing and more common in men than in women. The neurons affected are those in the brain that control muscle movement and have dopamine as their neurotransmitter. Named after James Parkinson (1730-1813), an English physician who made the detailed description of the disease in "An Essay on the Shaking Palsy" (1817).

(More? Neural Notes | Neural Abnormalities | Medline Plus - Parkinson's Disease | Pearce JM. Aspects of the history of Parkinson's disease. J Neurol Neurosurg Psychiatry. 1989 Jun;Suppl:6-10)

pars

(Latin, pars = part of) Anatomical term describing something as part of an organ or tissue.

parthenogenesis

(Greek, parthenos = virgin, genesis = birth) The development of an unfertilized egg (no sperm). Occurs mainly in plants but can also occur in animals.

(More? Week 1 Abnormalities | Molecular Development - Epigenetics - Parthenogenesis)

partial androgen insensitivity

A genetic disorder causing ambiguous genitalia in 46,XY individuals. This X-linked disease is due to an absence or deficiency of androgen receptors in the androgen target tissues (e.g. genital skin region).

(More? Reproductive System - Abnormalities)

parturition

(Latin, parturitio = childbirth) term used to describe the process of childbirth.

(More? Parturition Notes)

parvovirus

(Latin, parvo = poor) A family of viruses that infect many species. Human parvovirus B19 (a single-strand 5,594 nucleotide DNA Class II virus) infection is also called "fifth disease" and occurs mainly in children. Animal parvoviruses do not infect humans.

(More? Defect - Parvovirus)

passive immunity

(maternal passive immunity) Term used to describe the transfer of antibodies from one person to another, this can occur artificially or by maternal transfer ([M.htm#maternal_passive_immunity maternal passive immunity]) to the fetus and neonate.

(More? Placenta | Normal Development - Milk)

Pax

The name derived from Drosophila gene "===pa===ired" (prd) with a bo===x=== domain. Transcription factor of the helix-turn-helix structural family, DNA binding, and activating gene expression. In human, nine member proteins from Pax-1 to Pax-9.

(More? Molecular Factors - Pax | Molecular Notes)

PCB

Acronym for ===p===oly===c===hlorinated ===b===iphenyls, a class of chemicals linked to developmental defects.

(More? Defects - Chemical Notes)

PCB153

(2,2===,4,4===,5,50-hexachlorobiphenyl) A form of ===p===oly===c===hlorinated ===b===iphenyls, a class of chemicals linked to developmental defects.

(More? Defects - Chemical Notes)

Peabody Developmental Motor Scale II

(PDMS-2) An early postnatal neurological assessment scale used in screening and diagnosis of neural development.

(More? Neural Notes | Postnatal Development)

parenchymal

(parenchyma) Histological term used to describe the functional cells of an organ, tissue or structure. The term is often paired with stromal (stroma), which describes the supportive cells within an organ, tissue or structure.

perichondrium

The undifferentiated mesenchymal cells which surround the growth plate cartilage and regulate chondrocyte differentiation. Involved with endochondral bone formation process.

(More? Bone Notes)

pericyte

The smooth muscle-like cell which covers over blood vessel endothelial cells.

(More? Cardiovascular Notes | Lymphatic Notes)

perinatal

The early postnatal period relating to the birth, statistically it includes the period up to 7 days after birth.

(More? Normal Development - Birth)

perinatal mortality ratio

A statisical term which refers to the sum of late fetal deaths plus infant deaths within 7 days of birth divided by the number of live births, per 1,000 live births.

(More? Normal Development - Birth | Statistics | Australian Statistics)

perinuclear theca

The region located in the sperm head perinuclear region, containing a cytoskeletal element to maintain the shape of the sperm head and functional molecules leading to oocyte activation during [F.htm#fertilization fertilization].

(More? Spermatogenesis | Fertilization)

periosteum

fibrous membrane covering bone except on the surface of joints which are covered in articular cartilage.

(More? Musculoskeletal Notes | Bone Notes)

perisylvian cortex

region of the cortex (frontal and posterior) involved in the human cognitive specializations including language. posterior perisylvian superior temporal gyrus (STG)

(More? Neural Notes | Abrahams BS, Tentler D, Perederiy JV, Oldham MC, Coppola G, Geschwind DH. Genome-wide analyses of human perisylvian cerebral cortical patterning. Proc Natl Acad Sci U S A. 2007 Nov 6;104(45):17849-54.)

pericardial cavity

The anatomical body cavity in which the heart lies. The pericardial cavity forms in the lateral plate mesoderm above the buccopharyngeal membrane, as part of the early intraembryonic coelom. This cavity is initially continuous with the two early pleural cavities. Note the single intraembryonic coelom forms all three major body cavities: pericardial, pleural, peritoneal.

(More? Coelomic Cavity Notes | GAstrointestinal Tract Notes)

peritoneal cavity

The anatomical body cavity in which the lower body organs lie: intestines, liver, bladder, [U.htm#uterus uterus], ovary. The peritoneal cavity forms initially from two separate regions of the early intraembryonic coelom (formed in the lateral plate mesoderm), which with embryo folding, fuse to form a single cavity. Note the single intraembryonic coelom forms all three major body cavities: pericardial, pleural, peritoneal.

(More? Coelomic Cavity Notes | Gastrointestinal Tract Notes)

peritubular cells

(peritubular myoid cells) stromal cells (mesenchymal) located in the male gonad (testis) seminiferous tubule lying outside the basal membrane in the lamina propria surrounding seminiferous tubulus that regulate Sertoli cell function and contractility of seminiferous tubules. Also used to describe cells found in the kidney glomerulus.

(More? Week 1 - Spermatogenesis)

perivitelline space

(PVS) space between the oocyte (egg) and the surrounding zona pellucida, enlarged in the region where the polar body lies. In mice this has been shown to influence the site sperm entry independent of any asymmetry of the oocyte membrane.

(More? Week 1 - Fertilization | Motosugi N, Dietrich JE, Polanski Z, Solter D, Hiiragi T. Space asymmetry directs preferential sperm entry in the absence of polarity in the mouse oocyte. PLoS Biol. 2006 May;4(5):e135. )

perlecan

(heparan sulfate proteoglycan 2) An extracellular matrix proteoglycan expressed in the basal lamina of the neuroepithelium.

(More? Neural Notes | Extracellular Matrix Lecture)

Persistent Pulmonary Hypertension of the Newborn

(PPHN) A serious newborn condition due to due to the failure of closure one of the prenatal circulatory shunts, the ===ductus arteriosus===. Occurs in about 1-2 newborns per 1000 live births and results in hypoxemia.

(More? Respiratory Development - Birth)

Peyer's patches

The Gut-Associated Lymphoid Tissue (GALT) located in the ileum and appendix (lying between the lamina propria to the submucosa). These immune system structures are the first line of protection against ingested infectious agents.

(More? Gastrointestinal Tract Notes)

PGC

An acronym for ===P===rimordial ===G===erm ===C===ell, the embryonic cell that will form eventually either egg or sperm cell.

(More? Genital Notes | primordial germ cell movies)

PGD

===P===re-implantation ===G===enetic ===D===iagnosis, a screening procedure for embryos produced through in vitro fertilisation (IVF) for genetic diseases that would generate developmental abnormalities or serious postnatal diseases.

(More? Week 1 Notes | In Vitro Fertilization Notes)

pharyngeal arch

(branchial arches, Greek, branchial = gill) These are a series of externally visible anterior tissue bands lying under the early brain that give rise to the structures of the head and neck. In humans, five arches form (1,2,3,4 and 6) but only four are externally visible on the embryo. Each arch has initially identical structures: an internal endodermal pouch, a mesenchymal (mesoderm and neural crest) core, a membrane (endoderm and ectoderm) and external cleft (ectoderm). Each arch mesenchymal core also contains similar components: blood vessel, nerve, muscular, cartilage. Each arch though initially formed from similar components will differentiate to form different head and neck structures.

(More? Head Notes | Face Notes |Neural Crest Notes | Endocrine Notes)

pharyngeal arch artery

Each early developing pharyngeal arch contains a lateral pair of arteries arising from the aortic sac, above the heart, and running into the dorsal aorta. later in development these arch arteries are extensively remodelled to form specific components of the vascular system. Pharyngeal Arch 1 arteries are mainly lost and forms part of maxillary artery. Pharyngeal Arch 2 arteries remains to form the stapedial arteries. Pharyngeal Arch 3 arteries forms the common carotid arteries, internal carotid arteries in the neck. Pharyngeal Arch 4 arteries will form part of aortic arch (left arch artery) and part right subclavian artery (right arch artery) Pharyngeal Arch 6 arteries form part of left pulmonary artery (left arch artery) and part of right pulmonary artery (right arch artery).

(More? Cardiovascular Notes | Head Notes | Face Notes)

pharyngeal arch cartilage

Each early developing pharyngeal arch contains a horseshoe shaped band of cartilage that acts as a template and contributes to the development of head and neck bony and cartilagenous features, including the middle ear bones. Pharyngeal Arch 1 cartilage (Meckel’s cartilage) dorsal ends form malleus and incus midpart forms ligaments (ant. malleus, sphenomandibular) ventral part forms mandible template. Pharyngeal Arch 2 cartilage (Reichert’s cartilage) dorsal ends form stapes and Temporal bone styloid process, ventral part ossifies to form hyoid bone components, lesser cornu and superior body. Pharyngeal Arch 3 cartilage forms hyoid components, greater cornu and inferior part of hyoid. Pharyngeal Arch 4 and 6 cartilage forms laryngeal cartilages except epiglottis (from hypobranchial eminence).

(More? Middle Ear Notes | Head Notes | Face Notes)

pharyngeal arch nerve

Each early developing pharyngeal arch contains the developing cranial nerves, as a pair, within the arch mesenchyme. Each cranial nerve is numbered (roman numeral) in rostrocaudal sequence and also has a specific name. The cranial nerve within each arch often relates to the other structures formed from taht arch. Pharyngeal Arch 1 contains the trigeminal nerve (CN V, cranial nerve 5). Pharyngeal Arch 2 contains the facial nerve (CN VII, cranial nerve 7). Pharyngeal Arch 3 contains the glossopharyngeal nerve (CN IX, cranial nerve 9) Pharyngeal Arch 4 and 6 contains the Vagus (CN X cranial nerve 10), forming the adult superior laryngeal and recurrent laryngeal branches.

(More? Neural Notes | Neural Crest Notes | Head Notes | Face Notes)

pharyngeal arch pouch

An out-pocketing of the endoderm lined pharynx occurring between each developing pharyngeal arch. Each of the pharyngeal arch pouches contributes different components of the head and neck, either cavities or endocrine tissues. Pharyngeal Arch 1 pouch elongates to form tubotympanic recess tympanic cavity, mastoid antrum and auditory tube (Eustachian tube). Pharyngeal Arch 2 pouch forms the tonsillar sinus and is later mostly oblierated by palatine tonsil. Pharyngeal Arch 3 pouch forms the inferior parathyroid and thymus. Pharyngeal Arch 4 pouch forms the superior parathyroid, parafollicular cells of Thyroid.

(More? Middle Ear Notes | Thymus Notes | Parathyroid Notes | Thyroid Notes | Endocrine Notes | Head Notes | Face Notes)

pharyngotympanic tube

(auditory tube, eustacian tube, otopharyngeal 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)

pharynx

(throat) Forms the initial segment of the upper respiratory tract divided anatomically into three regions: nasopharynx, oropharynx, and laryngopharynx (hypopharynx). Anatomically extends from the base of the skull to the level of the sixth cervical vertebra.

(More? [respire.htm Respiratory Notes])

phenylketonuria

(PKU) A disease resulting from an inability to break down phenylalanine, an amino acid. Causes mental and motor retardation, microcephaly, poor growth rate and seizures. Can be tested in newborn screening.

(More? Neonatal Screening)

pheromone

A secreted chemical in sweat or urine that causes specific physiological response in other members of the same species.

(More? Mouse Development- Estrous Cycle)

phocomelia

(Greek, phoco = seal, melia = limb) a flipper-like appendage attached to the trunk, as described in the original classical classification of limb deficiencies. Seen in genetic and environmentally derived abnormalities, for example in association with thalidomide.

(More? Limb Abnormalities - Classification)

pineal gland

endocrine gland named as shape resembles a pine cone. Formed from a dorsal outpocket of diencephalon. The hormone melatonin (high in dark, low in day) involved with the diurnal cycle, inhibits pituitary-gonad axis.

(More? Endocrine Notes | Pineal Gland)

Pink Disease

chronic mercury poisoning in infants and young, also called acrodynia (Greek, acrodynia = painful extremities)

(More? [A.htm#acrodynia acrodynia] | Heavy metals | Michigan Health MercurySpillFactsheet_85689_7.pdf)

pharynx

The uppermost end of gastrointestinal and respiratory tract, in the embryo beginning at the buccopharyngeal membrane and forms a major arched cavity within the phrayngeal arches.

(More? Head Notes | GIT Notes | Carnegie stage 13 pharynx)

PKU

An acronym for the disease [#phenylketonuria phenylketonuria]

placental malaria

malarial infection of the placenta by sequestration of the infected red blood cells. Common in regions where malaria is endemic with women carrying their first pregnancy (primigravida).

(More? Abnormal Development | Brown University Maternal Malaria)

placentophagia

Term used to descrbe the maternal ingestion of afterbirth materials (placental membranes and amniotic fluid) that can occur following mammalian parturition (birth).

placode

(Greek, plax = plate, eidos = shape or form) A surface ectoderm thickening seen in the early embryo head region. Each pair of placodes will contribute a different component of each sensory system (otic placode, optic placode, nasal placode).

(More? Head Notes)

plagiocephaly

one of several skull deformities (scaphocephaly, oxycephaly, plagiocephaly, trigoncephaly) caused by premature fusion (synostosis) of different developing skull sutures. Plagiocephaly results from asymmetric coronal suture synostosis.

(More? Skull Notes | Head Notes)

plagiopatagium

is the thin skin membrane (extending from the fifth digit and the posterior aspect of the forelimb, along the side of the body, to the anterior aspect of the hindlimb) forming the bat wing.

(More? Other Embryos - Bat)

Plan B

A two pill high dose regimen of the oral contraceptive levonorgestrel, 90% effective in preventing pregnancy when taken within 72 hours of unprotected sex. Approved for use in some countries, but not the USA as it is considered an abortifacient not a contraceptive.

US Food and Drug Administration:

• September 2006 - approved the emergency contraceptive Plan B for sale over the counter to women aged 18 or over.
• April 2009 - would accept and not appeal against a New York federal court decision that 17 year old women should be able to buy the emergency contraceptive pill Plan B without a prescription.

(More? Human Menstrual Cycle - Birth Control)

plasma cell

A cell in the blood, the active B cell (lymphocyte) which is secreting antibody. Located in either bone marrow or peripheral lymphoid tissues, these cells have and increased cytoplasmic volume (due to increase rough endoplasmic reticulum) in comparison to the inactive (non-secreting) lymphocyte.

(More? Cardiovascular System - Blood | Cardiovascular System Development - Lymphatics)

Plasmodium falciparum

The microorganism that acts as a malarial parasite and can cause [#placental_malaria placental malaria].

(More? Placental Abnormalities | Abnormal Development - Maternal)

pleural cavity

Anatomical body cavity in which the lungs develop and lie. The pleural cavity forms in the lateral plate mesoderm as part of the early single intraembryonic coelom. This cavity is initially continuous with pericardial and peritoneal cavities and later becomes separated by folding ([#pleuropericardial_fold pleuropericardial fold], [#pleuroperitoneal_membrane pleuroperitoneal membrane]) and the later formation of the diaphragm. The pleural cavities form initially as two narrow canals. Note the single intraembryonic coelom forms all three major body cavities: pericardial, pleural, peritoneal.

(More? Respiratory Notes | [coelom.htm Coelomic Cavity Notes])

pleuropericardial fold

(pleuropericardial membrane) An early embryonic fold which restricts the communication between pleural cavity and pericardiac cavity, contains both the cardinal vein and phrenic nerve.

(More? Coelom Notes | Respiratory Notes)

pleuroperitoneal membrane

An early embryonic membrane that forms inferiorly at the septum transversum to separate peritoneal cavity from pleural cavity.

(More? Coelom Notes)

plexus

(Latin, plexus = a network) used anatomically to describe a network of interconnecting structures either nerves, blood vessels, or lymphatic vessels.

pluripotent

A stem cell term describing the ability of a stem cell to form (differentiate) into many different cell types. The term is often used in stem cell research instead of totipotent, which means that the stem cell can form all embryo cell types.

(More? Stem Cell Notes)

PMS

Acronym for [#PreMenstrual_Syndrome Pre-Menstrual Syndrome]

podocyte

(glomerular podocyte) Kidney epithelial cell type in the nephron (functional kidney unit) located in the glomerulus. Podocytes are at the filtration barrier between capillary blood and the nephron tubular system and function to ultrafiltrate blood, and support glomerular capillary pressures. The differentiation of podocytes involves the formation of cellular foot processes and then the slit membrane.

(More? Nephron Notes | Kidney Notes)

polar body

A small cytoplasmic exclusion body formed from the excess DNA formed during the egg meiotic cycle and following sperm [F.htm#fertilization fertilization]. There are 2-3 polar bodies derived from the oocyte present in the zygote, the number is dependent upon whether polar body 1 (the first polar body formed during meiosis 1) divides during meiosis 2. This exclusion body contains the excess DNA from the reductive division (the second and third polar bodies are formed from meiosis 2 at [F.htm#fertilization fertilization]). These polar bodies do not contribute to the genetic complement of the zygote, embryo or fetus. Recent research in some species suggest that the space formed by the peripheral polar body (between the oocyte and the zona pellucia) can influence site of sperm [F.htm#fertilization fertilization].

(More? Week 1 Notes)

polychlorinated biphenyls

PCBs, a class of chemicals linked to developmental defects.

(More? Defects - Chemical Notes)

Polycomb/Trithorax

(PRE/TREs) cis-regulatory DNA elements initiator elements and maintenance elements identified in drosophila development. They can activate or silence transcriptional state of associated genes for many cell generations (divisions).

(More? PubMed Review)

polysialic acid

(PSA) is a cell surface carbohydrate attached to neural cell adhesion molecule (NCAM) that regulates (inhibits) cell interactions. During development PSA has a role in promoting neural precursor cell migration and axon path-finding.

(More? PNAS Image)

Polycystic ovary syndrome

(PCOS) or Stein-Leventhal syndrome (1930s researchers) a metabolic syndrome with many other symptoms, ovarian cysts arise through incomplete follicular development or failure of ovulation.

(More? Urogenital Abnormalities)

polyestrous

Term used to describe animals which have an estrous cycle that continues throughout the year (cattle, pigs, mouse, rat). Other types of estrous cycles include: seasonally polyestrous animals (multiple estrous cycles only during certain periods of the year) and monestrous animals (have only one estrous cycle per year).

(More? Estrous Cycle)

polydactyly

(polydactylia or polydactylism) A developmental abnormality resulting in an additional fingers or toes. Occasional there is aslo a combination of polydactyly with syndactyly is known as polysyndactyly.

(More? Limb Abnormalities)

polysyndactyly

An abnormal digit (finger or toe) development resulting in a combination of polydactyly (additional digit) with syndactyly (digit fusion).

(More? Limb Abnormalities)

ponderal index

(PI) - Fetal calculation based upon the ratio of body weight to length PI = [weight (in g) x 100] √∑ [length (in cm)]

(More? Fetal Weight | Fetal Length | Fetal Notes)

positive predictive value

Prenatal diagnostic test term describing the probability that a congenital anomaly is present given that the prenatal screening test is positive.

(More? Prenatal Diagnosis)

posterior neuropore

(caudal neuropore) The initial opening at the spinal cord end or "tail end" of the neural tube before it closes (humans approximately 26 days post-fertilization). The opening at the other "head end" of the neural tube is the [A.htm#anterior_neuropore anterior neuropore]. Failure of posterior neuropore to close can lead to the neural tube defect (NTD) [S.htm#spina_bifida spina bifida].

(More? Neural Abnormalities | Neural Tube Defects)

postmature

A term used to describe infants born after 42 weeks clinical gestation. Normal clinical gestation is 40 weeks (which is usually 36-38 weeks embryonic development) infants born before 37 weeks are called premature.

(More? Normal Development - Birth)

Pouch of Douglas

(rectouterine pouch or rectovaginal) A female anatomical region describing the portion of the peritoneal cavity lying between the back wall of the [U.htm#uterus uterus] and rectum.

PPHNA

Acronym for [#Persistent_Pulmonary_Hypertension_Newborn Persistent Pulmonary Hypertension of the Newborn].

PPM

Acronym for ===p===arts ===p===er ===m===illion, used to describe chemical concentrations.

(More? Chemicals)

preantral follicle

([#primary_follicle primary follicle]) Term used to describe the developmental stage of ovarian follicle development following primordial in describing the sequence (primordial, preantral, antral) of follicle development within the ovary. In humans, a number of primordial follicles will begin to develop into preantral follicles (primary), some of which will then form antral follicles (secondary), with only a single antral follicle developing into the ovulating follicle (Graafian) each menstrual cycle.

(More? Week 1 - Oogenesis)

precocial species

newborn animals that are relatively mature and mobile from birth or hatching, for example guinea pigs and hoofed animals. (altricial is where newborns are immature and not motile).

preeclampsia

(toxemia, pregnancy-induced hypertension) high blood pressure and protein in the urine which can occur during pregnancy and may lead to eclampsia, a serious maternal condition leading to seizures or coma.

(More? Placenta | Medline Plus - preeclampsia eMJA - Pre-eclampsia: a lifelong disorder)

pregnancy-associated plasma protein-A

(PAPP-A) This placental protein is thought to have several different functions, including preventing recognition of the fetus by the maternal immune system, matrix mineralization and angiogenesis. It is a member of the alpha-macroglobulin plasma protein family, which bind cytokines and specifically cleave a binding protein for insulin-like growth factors (IGF binding protein 4 protease) modulating cytokine activity. Detection of this protein is also used as a first and second trimester diagnostic test for Trisomy 21.

(More? Abnormal Development - Prenatal Diagnosis - PAPP-A | Abnormal Development - Trisomy 21 (Down Syndrome) | Placenta Notes)

pregnancy (clinical)

A pregnancy verified by the presence of a gestational sac on ultrasound.

(More? Week 1 Notes)

pre-implantation genetic diagnosis

(PGD) a screening procedure for embryos produced through in vitro fertilisation (IVF) for genetic diseases that would generate developmental abnormalities or serious postnatal diseases.

(More? Prenatal Diagnosis | Week 1 Notes | In Vitro Fertilization Notes)

premature

The term used to describe infants born before 37 weeks. Normal clinical gestation is 40 weeks (which is usually 36-38 weeks embryonic development) infants born after 42 weeks clinical gestation are called postmature.

(More? Normal Development - Birth)

Pre-Menstrual Syndrome

a diverse range of symptoms that appear before menstruation, which apparently occur due to changing levels of sex hormones (progesterone, estrogen) and progesterone's metabolite (alopregnanolone) during the menstrual cycle. The possible PMS symptoms: tiredness, depression, restlessness, insomnia, irritability, emotional, outbursts of anger, headache, dizziness, abdominal pain, breast pain, water retention, diarrhoea, increase in appetite and food craving (sugar, salt). Women can show some or all of these symptoms.

(More? Human Menstrual Cycle | ABC RN Monday 8 June 1998 - Premenstrual Syndrome)

prenatal screening sensitivity

(detection rate) Prenatal diagnostic test term describing the probability of testing positive on a prenatal screening test if the congenital anomaly is present.

(More? Prenatal Diagnosis)

prenatal screening specificity

Prenatal diagnostic test term describing the probability of testing negative on a prenatal screening test if the congenital anomaly is absent.

(More? Prenatal Diagnosis)

presentation

A birth term, referring to how the fetus is situated in the [U.htm#uterus uterus] at the time of birth.

(More? Normal Development - Birth)

presenting part

A birth term, referring to the part of fetus body that is closest to the cervix.

(More? Normal Development - Birth)

prevalence

A statistical term used mainly in studying disease/disorders and is a measure of the proportion of a population that are disease cases at a point in time. Generally used to measure only relatively stable conditions, not suitable for acute disorders.

(More? Abnormal Development)

primary follicle

([#preantral_follicle preantral follicle]) Term used to describe the developmental stage of ovarian follicle development following primordial in describing the sequence (primordial, primary, secondary) of follicle development within the ovary. In humans, a number of primordial follicles will begin to develop into primary follicles, some of which will then form secondary (antral follicles), with only a single antral follicle developing into the ovulating follicle (Graafian) each menstrual cycle.

(More? Week 1 - Oogenesis)

primary heart field

(PHF, first heart field, FHF) A mesodermal region that forms the early primary heart field and contribute specific components (left ventricle) of cardiac development (endocardium, myocardium, and smooth muscle). A later forming [S.htm#second_heart_field second heart field] forms adjacently and contributes other cardiac structures. Recently suggested that this primary/secondary terminology should be replaced with gene specific expression domains or fields.

(More? Heart Notes)

primary organizer

The term used originally by Spemann to describe the dorsal lip of the blastopore, meaning that its action established the organization of the entire early embryo. (see [#primitive_node primitive node] | Hans Spemann | Nobel Laureate- Hans Spemann)

primigravida

Clinical term for woman who is pregnant for the first time.

primitive node

(Hensen's node, primitive knot) The small circular region located at the cranial end of the primitive streak, where gastrulation occurs, and is a controller of this process. It is centered around the primitive pit, the site of epiblast extension cranially to form the initial axial process. Region is equivilant to the blastopore in amphibians.

(More? Carnegie Stage 7 | Week 3 Gastrulation | Neural Notes | Nobel Laureate- Hans Spemann)

primitive streak

Visible region on the surface of the early epiblast embryonic bilaminar disc, representing the site of cell migration during gastrulation (cell migration to form endoderm then mesoderm). The primitive streak extends centrally from the [#primitive_node primitive node] (Hensen's node) to the disc periphery near the connecting stalk. The orientation of the streak establishes the early body axis (rostro-caudal, head-tail). In the human embryo, gastrulation occurs from week 3 through to week 4.

(More? Carnegie Stage 7 | Week 3 Gastrulation)

primordial follicle

Present in the ovary from birth, located in the stroma of the ovary cortex beneath the tunica albuginea. The primordial follicle is the oocyte and the surrounding follicular cells.

(More? Week 1 Notes)

primordial germ cell

Term used to describe either the sperm progenitor in the embryonic testes or oocyte progenitor present in the primordial follicle ovary from birth, located in the stroma of the ovary cortex beneath the tunica albuginea. The primordial follicle is the oocyte and the surrounding follicular cells. (More? Week 1 Notes)

processus vaginalis

A transient communicating channel in testes development between tunica vaginalis and peritoneal cavity.

(More? Urogenital Notes)

progesterone

A steroidal hormone of the progestogens class, which has many roles in the female. Functions include regulation of the menstrual cycle, uterine changes, maintaining pregnancy and effects on systems throughout the body. Biological sources include: adrenal glands, gonads (corpus luteum), brain, and placenta. Male progesterone has a suggested role in neural development. Progesterone is also used clinically as a part of hormone replacement therapy (HRT) in women. The human progesterone receptor has two isoforms (PRA and PRB).

(More? Human Menstrual Cycle)

progestins

these compounds are synthetically produced progestogens used clinically and experimentally.

(More? Human Menstrual Cycle)

prolactin

(PRL) anterior pituitary hormone which stimulates breast development and milk production in pregnancy. Also has a role in regulating follicle stimulating hormone (FSH) effect on the ovary. Protein hormone is similar in structure to both growth hormone (anterior pituitary) and chorionic somatomammotropin (placenta). Anterior pituitary release of prolactin is in turn regulated by the hypothalamus [#prolactin-releasing_hormone prolactin-releasing hormone] (PRLH, prolactin-releasing peptide). Recently been shown to to mimic in pregnancy effects of increased maternal myelination processes (oligodendrocyte precursor proliferation).

(More? Endocrine Development - Pituitary | Normal Development - Milk | OMIM - PRL)

prolactin-releasing hormone

(PRLH, prolactin-releasing peptide, PRRP) an 87 amino acid peptide hypothalamus hormone which regulates anterior pituitary release of prolactin.

(More? Endocrine Development - Hypothalamus | OMIM - PRLH)

pronephros

(Greek, pro = before) The first temporary stage of kidney development (pro-, meso-, meta-). This forms the kidney of primitive fish and lower vertebrates. Kidney development occurs within the intermediate mesoderm interacting with endoderm. In humans, this very rudimentary kidney forms very early at the level of the neck. It is rapidly replaced by the mesonephros, intermediate stage kidney, differentiating in mesoderm beneath.

(More? Urogenital Notes)

pronuclear fusion

(Greek, pro = before) The process of the fusion of the two haploid nuclear structures ([#pronucleus pronuclei]) contributed from the spermatazoa and oocyte to form the first diploid nucleus cell. Can also be called fusion of pronuclei.

(More? Week 1 Notes)

pronucleus

(Greek, pro = before) The two haploid nuclear structures from spermatazoa and oocyte that will fuse together to form the first diploid nucleus cell. Therefore the nuclear structures that exist "before the nucleus", the plural term is pronuclei.

(More? Week 1 Notes)

propatagium

is the thin skin membrane (extending from the shoulder to the wrist anterior to the upper arm and forearm) forming the leading edge of the bat wing.

(More? Other Embryos - Bat)

prophase

(Greek, pro = before) The first phase of mitosis, when the diffusely stained chromatin resolves into discrete chromosomes, each consisting of two chromatids joined together at the centromere.

(More? Week 1 Notes)

proprioception

(Greek, pro = before) The neurological sense of body position that is perceived both at the conscious and unconscious levels. There are a variety of peripheral specialized sensory structures that together provide the information on body position in space.

(More? Neural Notes)

proteasome

a large multiprotein complex found in all cells that functions in degradation of ubiquitylated proteins.

(More? UNSW Cell Biology)

proteinuria

The abnormal presence of protein in the urine and an indicator of diesease including diabetic kidney disease (DKD, diabetic nephropathy).

(More? Kidney Abnormalities)

prosencephalon

(forebrain) the most anterior neural tube primary brain vesicle (there are 3 primary brain vesicles) that will form the two secondary brain vesicles, telencephalon and diaencephalon. These generate in the adult brain the cerebral hemispheres (neocortex, basal nuclei, palaeocortex, archicortex) and thalmus, hypothalmus and other nuclei respectively. The prosencephalon lumen (cavity of the neural tube) will form the lateral and third ventricle.

(More? Neural Notes | Ventricular System)

pruritus

(Latin, prurire = to itch) itching skin sensation which can have a number of different causes (diabetes, iron deficiency, hyperthyroidism, Hodgkin's Disease, hair loss, allergic drug reaction).

(More? Skin Notes)

pseudohermaphrodite

(===Disorder of Sex Development, DSD===) A historic terminology no longer applied and replaced with the term ===Disorders of Sex Development=== (DSD). Humans having both male and female reproductive organs, occurs in both male and female forms.

• 46,XY DSD karyotype who have a predominantly female phenotype (blind-ending vagina, absence of breast development, primary amenorrhea, presence of testicular structures) that is with gonads of one sex, external genitalia of opposite.

• 46,XX DSD karyotype with gonads as ovaries, external genitalia ambiguous and hyperplastic adrenals secreting androgens.

• Ovotesticular DSD

(More? Reproductive System - Abnormalities)

puberty

(Latin, pubertas = adulthood) process involving maturation of the reproductive system. A complex process, initiated by an unknown mechanism, but involving the brain driving the hormonal axis.

(More? Endocrine Notes - Gonad | Puberty Notes)

puerperal

pertaining to childbirth or the period immediately following birth.

(More? Birth Notes)

puerperium

six weeks following parturition (birth). Maternal reproductive organs and physiology return to pre-pregnant state.

(More? Birth Notes)

pyelectasis

dilatation of the fetal renal pelvis (anteroposterior pelvic diameter >/=4 mm) visible with ultrasound.

(More? Kidney Notes | Movies - Abnormal Ultrasound)

pyknons

(Greek, pyknon = dense) term used to describe a DNA non-random pattern of repeated sequence elements identified in the human genome following computer analysis (genic and nongenic regions, patterns of 16+ bases in length, occurring 40+ times in nongenic). These sequences are: found frequently in the 3' untranslated regions (3'UTR) of genes, can be repeated with a regular spacing of 18 to 22 nucleotides between copies, and have currently an unknown function.

PV-1

A type II membrane glycoprotein component found in fenestrae and in caveolae.

(More? Stan RV, Kubitza M, Palade GE. PV-1 is a component of the fenestral and stomatal diaphragms in fenestrated endothelia. Proc Natl Acad Sci U S A. 1999 Nov 9;96(23):13203-7.)

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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