R

Glossary R

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Link to the Original UNSW Embryology Glossary R

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)

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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