R

Glossary Links

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raphe

Anatomical line of fusion of the urogenital folds lying along the urethra and scrotum in male external genitalia.

(More? Urogenital Notes)

Rathke's pouch

An ectodermal fold in roof of pharynx forming anterior pituitary (adenohypophysis) and pars intermedia. Named after German embryologist and anatomist Martin Heinrich Rathke (1793 — 1860).

(More? Pituitary Notes | Endocrine Notes | Martin Heinrich Rathke)

rectouterine pouch

(Pouch of Douglas or rectovaginal) Anatomical description of the female peritoneal cavity lying between the back wall of the [U.htm#uterus uterus] and rectum.

reductive division

Term describing meiosis where diploid DNA content becomes haploid (halved).

Reichert's cartilage

Neural crest forming the cartilage band of the second pharyngeal arch.

(More? Head Notes)

relative risk

(risk ratio or odds ratio) Term used in describing the effect of environmental teratogens on development. The ratio of the rate of the condition among the exposed and the non-exposed population. (e.g. smokers risk of having a low birth weight baby compared to non-smokers) A high relative risk may indicate a low absolute risk if the condition is rare. The other risk descriptor term used to describe the likelyhood of an abnormality is [A.htm#absolute_risk absolute risk].

(More? Abnormal Development - Environmental)

relaxin

The reproductive hormone involved in uterine relaxation (some species), reproductive tissue growth, connective tissue remodeling (collagen), cardiovascular, renal system, and brain. Relaxin receptor is G-protein-coupled receptor (relaxin family peptide receptors 1 - 4, RXFP1-4).

(More?Urogenital Notes)

renal

(Latin, renes = kidney) Term used in relation to the kidney and associated structures (renal pelvis, renal artery)

(More?Urogenital Notes)

repolarization

Term used in relation to the heart, repolarization is a term used to describe the relaxation after each cardiac contraction which is controlled by a gradient of ion channels.

(More?Heart Notes)

respiratory

Term used in relation to breathing (in and out) or associated with the lungs. Anatomically used to describe the lungs, air pathways and associated muscles. In cell biology used in relation to mitochondrial use of oxygen to produce energy and carbon dioxide waste.

(More? Respiratory Notes)

RESOLVE

A national, nonprofit consumer organization offering education, advocacy, and support to those experiencing infertility. Services include a national HelpLine, quarterly newsletter, extensive literature list, member-to-member contact systems, and local support groups through a network of over 50 chapters nationwide.

retained products of conception

Where part of the placenta or fetal membranes remains within the [U.htm#uterus uterus], often associated with early fetal loss in the first trimester (previously called incomplete abortion).

rete ovarii

A group of epithelial tubules located at the hilum of the ovary possibly mesonephric origin.

(More? Urogenital Notes)

rete testis

The duct (epithelial tubules) conduction system for spermatazoa embedded within the mediastinum (connective tissue) located in the center of the testis (male gonad) derived from the mesonephric duct, and allow spermatazoa to travel from the seminiferous tubules to the vasa efferentia. (Spermatozoa Duct Pathway: seminiferous tubule ‚Üí straight tubule ‚Üí rete testis ‚Üí ductuli efferentes ‚Üí ductus epididymidis ‚Üí ductus deferens)

(More? Spermatogenesis | Urogenital Notes)

retina

The stratified sensory structure of the eye, formed from the neural ectoderm that extends from the forebrain (diencephalon) to form initially the folded optic cup. Vertebrates have ten identifiable layers formed from nerve fibers, neurons, membranes, photoreceptors and pigmented cells. Light must pass through nearly all these layers to the photoreceptors. (1. Inner limiting membrane - Müller cell footplates; 2. Nerve fiber layer; 3. Ganglion cell layer - layer of retinal ganglion cells their axons form the nerve fiber layer and eventually the optic nerve; 4. Inner plexiform layer - another layer of neuronal processes; 5. Inner nuclear layer; 6. Outer plexiform layer; 7. Outer nuclear layer; 8. External limiting membrane - layer separating inner segment portions of photoreceptors from their cell nuclei; 9. Photoreceptor layer - rods and cones that convert light into signals; 10. Retinal pigment epithelium).

(More? Vision Notes)

retinal pigment epithelium

(RPE) An epethial pigmented cell layer lying outside the sensory retina, formed from the outer layer of the folded optic cup. The RPE is firmly attached to the underlying choroid and overlying retinal visual cells, for which it has a nutritional role.

(More? Vision Notes)

retinal waves

A form of coordinated spontaneous activity that occurs in the developing retina. These waves of electrical activity (action potentials) along with EphA/ephrin-A signaling are thought to have a role in establishing the initial retinotopic map by correlating/coordinating the activity of neighbouring retinal ganglion cells.

(More? Vision Notes)

Rhesus D

(RhD, Rh factor) The protein on surface of red blood cells in some blood types (Rh+) and absent in others (Rh-). Can cause erythroblastosis fetalis in second pregnancy if fetal/maternal blood of opposite groups mix on first pregnancy.

Rh factor

The protein on surface of red blood cells in some blood types (Rh+) and absent in others (Rh-). Can cause erythroblastosis fetalis in second pregnancy if fetal/maternal blood of opposite groups mix on first pregnancy.

Rho1

A small GTPase of the Rho subfamily (Rho, Rac and Cdc42) acts as regulatory switch for actin cytoskeleton. In development, activated in epithelial cells for invagination.

(More? Developmental Mechanisms)

rhombencephalon

(Greek rhombos = rhomboid, enkephalos = brain) The hindbrain, the most caudal neural tube primary brain vesicle (there are 3 primary brain vesicles) that will form the two secondary brain vesicles, metencephalon and the myeloncephalon. These will in turn generate in the adult brain the cerebellum, pons and medulla. The rhombencephalon lumen (cavity of the neural tube) will form the fourth ventricle.

(More? Neural Notes | Ventricular System)

rhombomere

A segmentation of the hindbrain (rhombencephalon) reflects segemental (rostro/caudal) expresion of Hox gene.

(More? Neural Notes)

ricin

A highly potent toxin produced by castor beans, it contains a ribotoxic A chain (RTA) and a cell-binding B chain.

roof plate

Term describing the thin dorsal region of the early neural tube.

(More? Neural Notes)

RU 486

RU 486 (or Mifepristone) is a steroid hormone similar in structure to the natural hormone progesterone, which is used as a birth control drug.

(More? RU486)

rubella

(Latin, rubella = little red) Virus also known as "german measles" (due to early citation in German medical literature). This virus can crosses the placenta from infected mothers and leads to major developmental defects in many different developing systems, including vision and hearing.

(More? Abnormal Development - Rubella Virus | Abnormal Development - Virus)

rugae palatinae

([P.htm#palatal_rugae palatal rugae]) The transverse ridges forming on the secondary palate which are also sequentially added as the palate grows.

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

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 S

S100B

A calcium-binding protein produced by glial cells (astrocytes, radial glia cells) with a trophic functions. :(More? [..neuron.htm Neural Notes] | OMIM - S100B | Hachem S, Laurenson AS, Hugnot JP, Legraverend C. Expression of S100B during embryonic development of the mouse cerebellum. BMC Dev Biol. 2007 Mar 15;7(1):17 )

sacculation

A general anatomical term meaning to formed a series of sac-like expansions. In lung development, the term refers to the sacculprocess of lung epithelial cell differentiation, vascular remodeling and thinning of the mesenchyme. This process leads to enlargement of the diameter and surface area of the alveolar sacs. Distal epithelial cells form 2 populations: 1. cells flattens, thins, and spreads to form type I cells; 2. cells remain cuboidal, acquire surfactant filled lamellar bodies and differentiate into type II cells.

(More? Respiratory Development)

SAHF

Acronym for Senescence-Associated Heterochromatic Foci, which are dense nuclear chromatin blobs found in cells undergoing senescence.

Sall4

A zinc finger transcription factor putatively involved in inner cell mass development. Nomenclature from Sal-like gene, homologus to Drosophila homeotic gene spalt (sal) which influences development of the fly's gut.

(More? Week 2 | OMIM - SALL4 | Flybase - splat | MBoC image - DNA binding by a zinc finger protein)

salpingitis

Clinical term referring to an inflammation of the uterine (fallopian) tube. For example, salpingitis isthmica nodosa whcih is a nodular swelling of the isthmic segment of the uterine tube.

(More? Human Menstrual Cycle | Genital System - Female Uterus)

SART

Acronym for [#SART Society for Assisted Reproductive Technology].

Santorini’s duct

(accessory pancreatic duct, APD) A duct which may be present as an anatomical variation due to the embryological origin of the pancreas from two pancreatic buds (dorsal and ventral). Named after Giovanni Domenico Santorini (1681 - 1737) an Italian anatomist who dissecting and delineating many anatomical features. Note the main pancreatic duct (MPD) from the dorsal bud, present in the body and tail of the pancreas (also called Wirsung’s duct).

(More? Pancreas | Pancreas History)

SBS

Acronym for ===S===haken ===B===aby ===S===yndrome, spectrum of neurological (eye, brain, subdural haemorrhage) and other (skeletal) injuries resulting from forcibly shaking an infant.

(More? Abnormal Development - Shaken Baby)

SC1

A chemical compound which has been found to allow embryonic stem cell in vitro propagation under chemically defined conditions in the absence of feeder cells, serum, and leukemia inhibitory factor. This chemical (a heterocycle compound) inhibits Ras-GAP (Ras remains activated) then enhancing stem cell renewal through the phosphatidylinositol 3-kinase (PI3K) pathway.

(More? Stem Cells)

scalp vascular plexus

A vascular feature visible on the head surface from Carnegie stage 20 (day 50).

(More? Skull Notes | Head Notes)

scaphocephalus

One of several skull deformities (scaphocephaly, oxycephaly, plagiocephaly, trigoncephaly) caused by premature fusion (synostosis) of different developing skull sutures. Scaphocephaly results from premature sagittal suture synostosis.

(More? Skull Notes | Head Notes)

Schmidt-Lanterman cleft

(Schmidt-Lanterman incisures, clefts of Schmidt-Lanterman, segments of Lanterman, medullary segments) A histological term describing the small amounts of Schwann cell cytoplasm located within the myelin sheath surrounding a myelinated neuronal axon. These spaces form channels for nutrient and other substances to be exchanged.

(More? Neural Notes)

schwannoma-derived growth factor

(SDGF) also called [A.htm#amphiregulin amphiregulin] (AREG), is an epidermal growth factor (EGF) family member having a role in regulating the epithelial proliferation.

sclerotome

The ventromedial half of each somite that forms the vertebral body and intervertebral disc.

(More? Musculoskeletal Notes | Week 3 Notes)

SDI

Sexually Transmitted Infection, this term replaces the older term Sexually Transmitted Disease, any infection that can be transmitted by sex between partners. Some of these infections have been shown to impact upon embryonic and fetal development.

(More? Abnormal Development - Bacterial Infection)

second heart field

(SHF) Mesodermal region that forms adjacent to the earlier forming primary heart field and contribute to the rapid growth of the heart by elongating the tube and providing specific components (right ventricle and outflow tract field) of cardiac development (endocardium, myocardium, and smooth muscle). Recently suggested that this primary/secondary terminology should be replaced with gene specific expression domains or fields.

(More? heart | original Heart Notes | PMID: 19609448)

second polar body

The small cytoplasmic exclusion body formed when the oocyte (egg) completes meiosis 2 at [F.htm#fertilization fertilization]. This exclusion body contains the excess DNA from the second reductive division (the first was formed from meiosis 1 at ovulation, and the third polar body is from division of this first body). 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)

second trimester

Clinical term used to describe and divide human pregnancy period (9 months) into three equal parts of approximately three calendar months. The first trimester corresponds approximately to embryonic development (week 1 to 8) of organogenesis and early fetal. The second and third trimester correspond to the fetal period of growth in size (second trimester) and weight (third trimester), as well as continued differentiation of existing organs and tissues.

(More? Embryo Stages | Human Fetal Period | Development Week by Week)

securin

An inhibitory chaperone protein important cell division. Destruction of this protein leads to activation of separase. which then allows separation of sister chromatids (chromosomes) at mitosis metaphase-to-anaphase transition.

(More? Week 1 Notes)

segmentation

Term used to describe the process of breaking a solid structure into a number of usually equal size pieces.

seizure

(Latin, sacire = to take possession of) A clinical condition associated with discharge (abnormal, excessive, hypersynchronous) of a group of cortical neurons. Recurrent seizures of unknown etiology occur in Epilepsy.

(More? Neural Notes)

sella turcica

(Latin sella = saddle, turcica = Turkish) refers to the shape of the sphenoid bone in which the pituitary gland resides (pituitary fossa). :(More? Endocrine Notes - Pituitary)

senescence

In aging, generally at a cellular level with the accumulation of various ageing effects. Cells no longer carrying out their differentiated function and begine to decline. In many cases cells can divide a limited number of times before they become senescent, while oncogenic (cancer) cells can "escape" senescence and become proliferative.

sensitivity

See [P.htm#prenatal_screening_sensitivity prenatal screening sensitivity]

separase

An important cell division protease allows the separation of sister chromatids (chromosomes) at mitosis metaphase-to-anaphase transition. This enzyme is activated by destruction of an inhibitory chaperone (securin).

(More? Week 1 Notes)

septicemia

Bacteria present in the blood lead to an amplified and dysregulated immune response. Common infection sites for bacterial entry into the blood are infections in: lungs, urinary tract, abdominal cavity, and primary infections of the bloodstream.

(More? Circulatory Notes | Placenta Notes)

septum transversum

(transverse septum) A mesodermal region in the early embryo. Identified externally as the junctional site between amnion and yolk sacs, and internally (within the embryo) lying directly beneath the heart and at the foregut/midgut junction. This ventro-dorsal "plate" of mesoderm contributes several structures including: the central tendon of diaphragm and some of the liver. The transverse septum has an important structural role in early embryonic development and is pierced by the gastrointestinal tract.

(More? Gastrointestinal Tract Notes | Liver Notes | Respiratory Development - Diaphragm)

Sertoli cells

The supporting cells in the testes (male gonad) that induce primordial germ cells to commit to sperm development. Support is nutritional and mechanical, as well as forming a blood-testis barrier. In development these cells secrete anti-Müllerian hormone, which causes the Müllerian (paramesonephric) duct to regress, and help to induce other somatic cells to differentiate into Leydig cells. The cells are named after Enrico Sertoli (1842 - 1910), and italian physiologist and histologist.

(More? Urogenital Notes | Enrico Sertoli | UWA Blue Histology - Male Reproductive System)

Sessel's pouch

In early head development, an endodermal bud underlying the nasofrontal bud will form Sessel's pouch which later degenerates. In the chick embryo, this structure patterns first the nasal septum and later the nasal capsule, the ethmoid bone, and the upper beak.

SET

Acronym for Single-Embryo Transfers, a single embryos transferred when women undergo Assisted Reproduction Technology compared to double-embryo transfer (DET).

(More? In Vitro Fertilization)

sflt-1

acronym for soluble vascular endothelial growth factor (VEGF) receptor-1 also known as sVEGFR-1. A soluble receptor which has been shown to trap VEGF-A stopping it from stimulating the formation of blood vessels in the cornea.

(More? Eye Notes | Ambati BK, etal. Corneal avascularity is due to soluble VEGF receptor-1. Nature. 2006 Oct 18)

SHFM

An acronym for [#split_hand_foot_malformation Split Hand Foot Malformation]

SIRT

A mammalian homologue of Sir2 (Silent information regulator 2) a NAD-dependent deacetylase that links metabolism with longevity in several species. Mammals have 7 homologues (SIRT1–7) which together potentially regulate several functions associated with physiology, calorie restriction, and aging.

shotgun sequencing

DNA sequencing method. Breaks chromosomal DNA into small overlapping fragments which are individually sequenced, the entire sequence is then "reconstructed" by linking overlapped sequences together. This method has been used for whole genome sequencing.

(More? Molecular Notes)

single letter amino acid code

The individual amino acids that form proteins can be represented by a standardised single letter code, three letter code or by their entire name.

===A=== - Alanine (Ala) | ===C=== - Cysteine (Cys) | ===D=== - Aspartic Acid (Asp) | ===E=== - Glutamic Acid (Glu) | ===F=== - Phenylalanine (Phe) | ===G=== - Glycine (Gly) | ===H=== - Histidine (His) | ===I=== - Isoleucine (Ile) | ===K=== - Lysine (Lys) |===L=== - Leucine (Leu) | ===M=== - Methionine (Met) | ===N=== - Asparagine (Asn) | ===P=== - Proline (Pro) | ===Q=== - Glutamine (Gln) | ===R=== - Arginine (Arg) | ===S=== - Serine (Ser) | ===T=== - Threonine (Thr) | ===V=== - Valine (Val) | ===W=== - Tryptophan (Trp) | ===Y=== - Tyrosine (Tyr)

(More? Molecular Notes)

single umbilical artery

(SUA) Placental cord with only a single placental artery (normally paired). This abnormality can be detected by ultrasound (colour flow imaging of the fetal pelvis) and is used as an indicator for further prenatal diagnostic testing for chromosomal abnormalities and other systemic defects.

(More? Prenatal Diagnosis | Ultrasound | Trisomy 21)

sinoatrial node

Heart region consisting of modified/specialized myocardial cells that initiate the heart beat. This cardiac pacemaker region lies at the junction of the right atrium and the superior vena cava (superior caval vein) and is initially formed from embryonic myocardial cells bordering the inflow tract of the early heart tube.

(More? Heart Notes | Embryonic Heart Rate)

sinus venosus

early developmental cardiovascular structure, thin walled cavity, forming the input to developing heart which has 3 venous inputs (vitelline vein, umbilical vein, commom cardinal vein). Later in heart development this structure gets incorporated into the wall of the future right atrium. Abnormalities of sinus venosus development contribute about 10% of all atrial septal defects.

(More? Heart Notes | Heart Abnormalities - ASD)

siRNA

acronym for small interfering RNAs, a class of regulators of gene expression. They are generated from double-stranded RNA (dsRNA) precursors. There is also another class of small RNAs involved in gene expression present in cells, MicroRNA, based upon "Dicer".

Sizzled

(Szl) a member of the secreted Frizzled receptor related protein (Sfrp) family identified in chicken. These proteins are antagonists and modifiers of Wnt and BMP signalling and is expressed in early heart development.

(More? Heart Notes)

SMAD4

A gene homologue 4 of Mothers Against Decapentaplegic (drosophila gene), tumor suppressor gene, its mutation causes 90% of human pancreatic carcinomas (pancreatic ductal adenocarcinomas). Deletion of SMAD4 in embryonic pancreatic epithelium had no apparent effect on pancreatic development.

(More? OMIM - SMAD4 | Endocrine Development - Pancreas | Article - knockout SMAD4)

small intestine

The gastrointestinal tract between stomach and large intestine, functions include digestion and absorption of nutrients. The small intestine is then subdivided into 3 regions: duodenum, jejunum and ileum.

(More? GIT Notes)

Snail

The zinc finger transcriptional repressors involved in regulation of epithelial–mesenchymal transitions in vertebrates.

(More? Molecular Factors- Snail)

single-nucleotide polymorphism

(SNP) places in the genome sequence where one fraction of the human population has one nucleotide, while another fraction has another. SNPs are the most abundant form of DNA variation in the human genome with an estimated 7 million common SNPs with a minor allele frequency (MAF) of at least 5% across the entire human population. Most SNPs have no effect on phenotype, though a subset of SNPs are the genetic basis of human variability. Reference: DA Hinds etal., Whole-Genome Patterns of Common DNA Variation in Three Human Populations

SNP

Acronym for [#snp single-nucleotide polymorphism]

Society for Assisted Reproductive Technology

(SART) An affiliate of the American Society for Reproductive Medicine composed of clinics and programs that provide ART (Assisted Reproductive Technology). SART reports annual fertility clinic data to the Centers for Disease Control and Prevention (CDC). SART Website

(More? Week 1 Notes - IVF)

soft palate

(velum, muscular palate) The muscular posterior portion of the palate forming the roof of the oral cavity. The bony anterior portion of the palate is called the hard palate, formed by maxillary and palatine bones.

(More? Head Notes)

somatic mesoderm

Mesoderm derived from lateral plate mesoderm, and found closest to the ectoderm and separated from other component of lateral mesoderm (splanchnic, near endoderm) by the intraembryonic coelom. Note: Students often confuse the terms, and therefore the derivatives of, somatic mesoderm with "somitic mesoderm" (which is the somite).

soma

(Greek, soma = body) Term used to describe tne cell body of a neuron. Also used in relation to body structures (somatic, somatosensory).

somesthetic

(Greek, soma = body) = somatosensory, sense perception.

somite

Segmental block (ball) of mesoderm formed from paraxial mesoderm adjacent to notochord (axial mesoderm) forming muscle and connective tissues of the body. Differentiates to form two intermediate components called the sclerotome and dermamyotome (then dermatome and myotome). Note the paraxial mesoderm of the head region does not segment.

(More? Musculoskeletal Notes | Week 3 Notes)

somitocoel

A transient cavity that appears within each of the early forming somites which is then lost as cells proliferate within the [#somite somite].

(More? Musculoskeletal Notes | Week 3 Notes)

somitogenesis

The process of segmentation of the paraxial mesoderm within the trilaminar embryo body to form pairs of somites, or balls of mesoderm. A somite is added either side of the notochord (axial mesoderm) to form a somite pair. The segmentation does not occur in the head region, and begins cranially (head end) and extends caudally (tailward) adding a somite pair at regular time intervals. The process is sequential and therefore used to stage the age of many different species embryos based upon the number visible somite pairs. In humans, the first somite pair appears at day 20 and adds caudally at 1 somite pair/90 minutes until on average 44 pairs eventually form.

(More? Week 3 - Somitogenesis | Musculoskeletal Notes)

sonic hedgehog

(SHH) secreted growth factor that binds patched (ptc) receptor on cell membrane. SHH function is different for different tissues in the embryo. In the ===nervous system===, SHH is secreted by the notochord, ventralizes the neural tube, inducing the floor plate and motor neurons. In the ===limb===, SHH is secreted by the zone of polarizing activity (ZPA) organizing limb axis formation. SHH has still others roles in ===organ development=== in lung, pancreas, etc. SHH name derives from homology to the original fruitfly (drosophila) "hedgehog" mutation, where these flies have hairs in regions (ventral) which are normally hair-free, and therefore have a disrupted body pattern. Nomenclature note lower case shh for other species, upper case SHH in humans.

(More? Molecular Factors - sonic hedgehog | Molecular Notes | Musculoskeletal Notes | Neural Notes)

SOX2

Acronym for ===S===ry-related HMG-B===ox ===2, a 317-amino acid protein involved in regulating many different systems.

(More? OMIM Sox2)

SOX9

Gene and protein name for SRY-related high-mobility group (HMG) box 9, a 509-amino acid transcription factor protein involved in regulating many different systems, including mammalian testis determination and pancreas organogenesis (a progenitor cell specific marker and maintenance factor). See also Sry.

(More? Pancreas Notes | Molecular Notes | OMIM Sox9 | Protein Sox9 | PNAS Seymour PA, Freude KK, Tran MN, Mayes EE, Jensen J, Kist R, Scherer G, Sander M. SOX9 is required for maintenance of the pancreatic progenitor cell pool. Proc Natl Acad Sci U S A. 2007 Jan 31)

spalt

Drosophila homeotic zinc finger transcription factor gene (sal) which influences development of the fly's gut. Human homologue are SALL (sal-like) genes.

(More? Flybase - splat | MBoC image - DNA binding by a zinc finger protein)

sperm

The male haploid reproductive cell, often used generically (and incorrectly) to describe these cells and the fluid of the ejaculate. Term is a shortened form of scientifically correct term [#spermatazoa spermatazoa].

(More? Week 1 - Spermatogenesis)

spermatazoa

The male haploid reproductive cell, produced by meiosis in the testis (male gonad).

(More? Week 1 - Spermatogenesis)

spermatogenesis

(Greek, genesis = origin, creation, generation) The term used to describe the process of diploid spermatagonia division and differentiation to form haploid spermatazoa within the testis (male gonad). The process includes the following cellular changes: meiosis, reoorganization of DNA, reduction in DNA content, reorganization of cellular organelles, morphological changes (cell shape). The final process of change in cell shape is also called [#spermiogenesis spermiogenesis].

(More? Week 1 - Spermatogenesis)

spermiogenesis

(Greek, genesis = origin, creation, generation) The maturation process of the already haploid spermatazoa into the mature sperm shape and organization. This process involves reorganization of cellular organelles (endoplasmic reticulum, golgi apparatus, mitochondria), cytoskeletal changes (microtubule organization) and morphological changes (cell shape, acrosome and tail formation).

(More? Week 1 - Spermatogenesis)

spermatogonia

The cells located in the seminiferous tubule adjacent to the basal membrane that either divide and separate to renew the stem cell population, or they divide and stay together as a pair (Apr spermatogonia) connected by an intercellular cytoplasmic bridge to differentiate and eventually form spermatazoa.

(More? Week 1 - Spermatogenesis)

spermatogonial stem cells

The spermatagonia cells located beside the seminiferous tubule basal membrane that either divide and separate to renew the stem cell population, or they divide and stay together as a pair (Apr spermatogonia) connected by an intercellular cytoplasmic bridge to differentiate and eventually form spermatazoa.

(More? Week 1 - Spermatogenesis)

spina bifida

( spina bifida = "split spine") A neural tube defect (NTD) caused by failure of the early neural tube to close correctly. This defect can occur anywhere along the length of the neural tube at the level of the spinal cord. The defect can also occur at the spinal cord end of the neural tube, the posterior neuropore. Because the neural tube remains open in adddition to the neural effects, the surrounding spinal column/vertebra, connective tissue and skin may also be affected. The two main forms are ===open=== (neural elements are exposed to the external environment) or ===closed=== (occult, covered with skin).

(More? Neural Abnormalities | Neural Tube Defects)

spinal canal

The mature space in the core of the spinal cord (filled with CSF) formed from the original lumen of the neural tube. :(More? Neural Notes)

spinal cord

The caudal (tail) end of neural tube that, together with the brain (rostral end of neural tube), forms the central nervous system (CNS). Note: the process of secondary neuralation contributes the very caudal end of the spinal cord.

(More? Neural Notes)

spinal dysraphism

(neural tube defects, NTD) abnormality resulting from a developmental incomplete closure of the neural tube leading to not only neural but also spinal column defects. The two main forms are open (neural elements are exposed to the external environment) or closed (occult, covered with skin).

(More? Neural Notes)

spinal ganglia

(dorsal root ganglia, DRG) Aperipheral nervous system sensory ganglia derived from the neural crest, lying laterally paired and dorsally to the spinal cord (in the embryo found ventral to the spinal cord). Connects centrally with the dorsal horn of the spinal cord.

(More? Neural Crest Notes)

spinal nerve

A mixed nerve (motor and sensory) arising as lateral pairs at each vertebral segmental level.

(More? Neural Notes)

splanchnic mesoderm

Gastrointestinal tract (endoderm) associated mesoderm formed by the separation of the lateral plate mesoderm into two separate components by a cavity, the intraembryonic coelom. Splanchnic mesoderm is the embryonic origin of the gastrointestinal tract connective tissue, smooth muscle, blood vessels and contribute to organ development (pancreas, spleen, liver). The intraembryonic coelom will form the three major body cavities including the space surrounding the gut, the peritoneal cavity. The other half of the lateral plate mesoderm (somatic mesoderm) is associated with the ectoderm of the body wall.

(More? Week 3 | Gastrointestinal Tract Notes | Heart Notes )

spleen

The spleen develops within the gastrointestinal tract dorsal mesogastrium mesenchyme. With folding it is located on the left side of the abdomen and has a role initially in blood (haematopoisis, blood cell formation) and later immune system development. The spleen's haematopoietic function is lost with fetal development and lymphoid precursor cells migrate into the developing organ.

(More? Spleen Notes | Gastrointestinal Tract Notes)

spontaneous abortion

(miscarriage) A pregnancy ending in the spontaneous loss of the embryo or fetus before 20 weeks of gestation.

spliceosome

The structure formed within the cell nucleus a complex assembly of proteins and RNA required for processing RNA, removing introns to generate the exon only mRNA sequence. The complex is formed from five small nuclear ribonucleoprotein particles (snRNPs) and more than 300 different proteins.

split hand foot malformation

(SHFM, ectrodactyly, cleft hand, central ray deficiency) highly variable malformation (genetic heterogeneous, 5+ loci mapped) of hand and foot abnormalities occuring in isolation or in association with other systematic anomalies (congenital heart defects).

(More? Musculoskeletal - Limb Development Abnormalities)

spontaneous abortion

(miscarriage) a pregnancy ending in the spontaneous loss of the embryo or fetus before 20 weeks of gestation.

SPS

(Serine, Proline, Serine) A protein general nuclear translocation signal (NTS) sequence. SPS is the single amino acid code for a 3 amino acid domain that when phosphorylated binds to importin7 and gets released from nuclear pore proteins.

(More? Molecular Cell, Vol 31, 850-861, 26 September 2008)

sry

(Sry, human; Testis-Determining Factor, TDF; Testis-Determining Factor on Y, TDY ) Gene name ===s===ex-determining ===r===egion of ===Y===, the gene locus on the Y chromosome encoding the male "testis determining factor", a protein transcription factor and a member of the high mobility group (HMG)-box family of DNA binding proteins. See also the transcription factor SRY-related protein, SOX9 (SRY-related high-mobility group (HMG) box 9)

(More? Molecular Notes | Week 1 Notes | OMIM)

SSRI

Acronym for ===S===elective ===S===erotonin ===R===euptake ===I===nhibitors, drugs used in the treatment of depression, antidepressants. Some examples include: citalopram (brand name of Celexa), fluoxetine (brand name of Prozac), paroxetine (brand name of Paxil) and sertraline (brand name of Zoloft).

(More? Abnormal Development - Maternal Drugs | Australia healthinsite - SSRIs)

Stage-Specific Embryonic Antigen-1

(SSEA-1) A cell surface embryonic marker (antigen) which has a role in cell adhesion, migration and differentiation and is often differentially expressed during stem cell development. Can be identified by Davor Solter monoclonal antibody MC-480 (SSEA-1).

(More? Stem Cell Notes)

Stage-Specific Embryonic Antigen 4

(SSEA-4) A cell surface embryonic marker (antigen) of human teratocarcinoma stem cells (EC), human embryonic germ cells (EG) and human embryonic stem cells (ES) which is down-regulated following differentiation of human EC cells. This antigen is not expressed on undifferentiated murine EC, ES and EG cells but upregulated on differentiation of murine EC and ES cells. Can be identified by Davor Solter monoclonal antibody MC-813-70 (SSEA-4).

(More? Stem Cell Notes)

stem cell

Term used to describe a cell with the potential to reproduce itself indefinitely, as well as differentiate into any other embryo tissue cell types. There are also a number of different specialised stem cell definitions: totipotential stem cell (as described above), pluripotential stem cell (capable of forming a number of different cell types), embryonic stem cell (derived from the blastocyst), cord blood stem cell (derived from placental cord blood), and adult stem cell (derived from adult or postnatal tissue).

(More? Stem Cell Notes)

Stem Cell Antigen 1

(Sca-1) A cell surface marker (antigen) for mouse hematopoietic progenitor/stem cell subset. It is a member of the Ly-6 family of GPI-linked surface proteins (Mr 18 kDa).

(More? Stem Cell Notes)

stenosis

Term used to describe an abnormal narrowing, usually in relation to a tube. For example, blood vessel, gastrointestinal tract or respiratory tract.

(More? Gastrointestinal Tract Abnormalities)

stillbirth

A fetus or infant delivered without signs of life after 20 weeks or more of gestation.

stigmergy

term, named by Pierre-Paul Grasse studying ants and termites, used to describe a self-organising system arising from individuals interacting with their environment. This mechanism is suggested to have a role in the developing neural system, responding to a series of attractive and repulsive extracellular cues.

(More? Neural Notes)

stimulated cycle

An ART cycle in which a woman receives drugs to stimulate her ovaries to produce more follicles.

(More? Week 1 Notes)

stomach

Gastrointestinal tract (GIT) foregut organ that has a major function in digestion. In humans, during week 4 initially as a dilatation of the foregut lying behind the heart. Differential growth of the ventral and dorsal walls establishes the greater curvature of the stomach and second rotation (of 90 degrees) occurs on the longitudinal axis establishing the adult anatomical orientation of the stomach.

(More? Gastrointestinal Tract - Stomach | Gastrointestinal Tract Notes)

stomadeum

(stomadeum) A ventral surface depression on the early embryo head surrounding the [B.htm#buccopharyngeal_membrane buccopharyngeal membrane], which lies at the floor of this depression. This surface depression lies between the maxillary and mandibular components of the first pharyngeal arch.

(More? Gastrointestinal Tract Notes | Head Notes)

straight tubule

(tubulus rectus) A structure within the testis (male gonad) a tubular system connecting seminiferous tubule to the rete testis within the mediastinum. (Spermatozoa Duct Pathway: seminiferous tubule ‚Üí straight tubule ‚Üí rete testis ‚Üí ductuli efferentes ‚Üí ductus epididymidis ‚Üí ductus deferens)

(More? Spermatogenesis)

stroma

(Greek, stroma = "a cover, table-cloth, bedding") Histological term used to describe supportive cells within an organ, tissue or structure. The term is often paired with [P.htm#parenchyma parenchyma], which describes the functional cells of an organ, tissue or structure. All organs can therefore be functionally divided into these 2 components, stromal/parenchymal.

stromal cells

(Greek, stroma = "a cover, table-cloth, bedding") Descriptive term in the ovary, for cells surrounding the developing follicle that form a connective tissue sheath (theca folliculi). This layer then differentiates into 2 layers (theca interna, theca externa). This region is vascularized and involved in hormone secretion.

(More? Week 1 Notes)

subcapsular sinus

(marginal sinus) space lying under the connective tissue capsule which receives lymph from afferent lymphatic vessels.

(More? Cardiovascular System Development - Lymphatics)

subventricular zone

(SVZ) A region/layer in the developing nervous system near the ventricular layer from which newly formed neuroblasts migrate. Also the site of adult neurogenesis (neural stem cells) in the anterior lateral ventricles.

(More? Neural Notes)

sulcation

The process of brain growth in the second to third trimester which forms sulci, grooves or folds visible on fetal brain surface as gyri grow (gyration). Abnormalities of these processes can lead to a smooth brain (lissencephaly).

(More? Neural Notes)

SUMO

An acronymn for Small Ubiquitin-like Modifier protein, which are a family of small proteins that modify the function of other proteins by covalently attaching to and detaching from the other proteins.

(More? Placental Molecular)

SUMOylation

A post-translational protein modification involving SUMO proteins attaching/detaching to other proteins and has a role in many different cellular processes. Similar to the degradation ubiquitination process.

(More? Placental Molecular)

surfactant

A detergent secreted by Type 2 alveolar cells between alveolar epithelium. Functions to lower surface tension, allowing lungs to remain inflated. Note: In humans, these cells and their secretion develop towards the very end of the third trimester, just before birth. Hence the respiratory difficulties associated with premature births (Newborn Respiratory Distress Syndrome, Hyaline membrane disease).

(More? Respiratory Notes | Respiratory Abnormalities | Newborn Respiratory Distress Syndrome)

SWISH

Acronym for State Wide Infant Screening Hearing program. A newborn hearing testing program using an automated auditory response technology. Program was introduced in NSW Australia in 2002 across 17 area health service coordinators.

(More? Hearing Notes | Hearing Abnormalities | Child Notes - Neonatal Screening | Child Notes - Neonatal Hearing Screening)

syncytialization

The process of cellular fusion to form a multinucleated cytoplasmic mass, occurs in placenta ([#syncytiotrophoblast syncytiotrophoblast]) and skeletal muscle (myoblast to myotube) development. The process involves cellular recognition, migration, adhesion and finally cell fusion between the two interacting cells.

(More? Week 2 Notes | Placenta Notes | Musculoskeletal Development - Muscle Development)

syncytiotrophoblast

A multinucleated cell currently thought to form by the fusion of cytotrophoblasts (trophoblasts) within the trophoblast layer (shell) of the implanting conceptus. In early development, these cells mediate implantation of the conceptus into the uterine wall and secrete the hormone ([C.htm#human_chorionic_gonadotrophin human Chorionic Gonadotrophin], hCG) responsible for feedback maintainance of the corpus luteum (in maternal ovary) and therefore maintaining early pregnancy.

(More? Week 2 Notes | Placenta Notes | [C.htm#human_chorionic_gonadotrophin human Chorionic Gonadotrophin])

syncytin

(human endogenous retrovirus, HERV) envelope gene of a human endogenous defective retrovirus and a factor specifically expressed in syncytiotrophoblasts with several suggested roles. 1. may contribute towards immune tolerance of the developing embryo (human syncytin-2 and mouse syncytin-B). 2. may mediates cell-cell fusion to initially form multinucleated syncytiotrophoblast from cytotrophoblasts on the trophoblast layer (shell) of the implanting conceptus (human syncytin-1 and mouse syncytin-A).

(More? Week 2 Notes | Placenta Notes | OMIM)

symphysiotomy

An operation carried out to increase the size of the pelvic outlet to permit vaginal delivery of a baby.

(More? Birth - Symphysiotomy | Birth)

syndactyly

(Greek, syn = together; daktulos = finger or digit) webbing between fingers which may be single or multiple and may affect: skin only, skin and soft tissues or skin, soft tissues and bone.

(More? Limb Abnormalities)

synoviolin

(Synovial Apoptosis Inhibitor 1, SYVN1, HRD1) protein enzyme (ubiquitin ligase) expression is induced by the unfolded protein response (UPR) following an endoplasmic reticulum (ER) stress. Protein is also overexpressed in the synovial cells of patients with rheumatoid arthritis.

(More? Joint Development | OMIM - Synovial Apoptosis Inhibitor 1)

syphilis

disease caused by the bacterium Treponema pallidum, a spirochete with a relatively small genome and requires a host to survive. First recognized in the 15th century in Europe, it can kill early fetuses or produce congenital deafness in older fetuses.

(More? Abnormal Development - Bacterial Infection)

syringocele

(Greek, syringo = tube, cele = swelling) an abnormality of duct systems. For example, seen in bulbourethral gland with dilatation of the Cowper's duct.

(More? Genital Male - Accessory Glands)

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 4) Embryology R. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/R

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