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- (Greek, labyrinthos) Term used to describe the complex inner ear system of fluid-filled passages which provides the sense of balance (semicircular canals, vestibule), the membranous labyrinth. Named by analogy with the Greek mythology maze that imprisoned the Minotaur.
- (Latin lactans = suckling) production of milk through action of prolactin and other hormones on breast tissue. Therefore associated mainly with mammals.
- Term used to describe the lymphatic vessels of the small intestine.
- (Lactobacillus acidophilus, L. acidophilus) Genus of Gram-positive bacteria, used in many different processes of food production. Lactobacillus acidophilus is the most common bacteria found as part of the normal flora of the female vagina, acidifying the environment and preventing urogenital infections. Other idenitifed vaginal species include L. jensenii, L. crispatus and L. iners. The plural is lactobacilli and the bacteria lower the pH by creating lactic acid.
- Anatomical and histological description of a small pit or cavity. Often used to describe the maternal blood-filled spaces formed during placenta development, maternal lacunae.
- (More? Lecture - Placenta Development)
- Blood-filled spaces within endometrium, formed following blastocyst implantation and trophoblast erosion of the maternal sinusoids.
- A feature of abnormal intestinal rotation involving a series of bands crossing the duodenum which can cause duodenal obstruction.
- (dendritic cell) Antigen-presenting immune cell found mainly in adult skin and mucosa.
- (More? Immune System Development)
- (layer of Langhans) Historic terminology for the trophoblast layer, the cytotropboblast cells were therefore also called Langhans' cells (not immune Langerhan cells).
- (More? Placenta Development)
- A fine coat of body hair found on the fetus.
- A term describing the concentric layers of bone.
- (More? Bone Development)
- The highly organized strong bone matrix deposited in concentric sheets with a low proportion of osteocytes found in compact bone. Many collagen fibers parallel to each other in the same layer.
- A term describing a thin layer or sheet.
- The layer of loose connective tissue underneath the epithelium of mucosa.
- A surgical procedure in which a fiber optic instrument (a laparoscope) is inserted through a small incision in the abdomen to view the inside of the pelvis.
- The gastrointestinal tract region lying between the end of the small intestine ileum and anus. Function is to absorb fluid, water and salts, from solid wastes before they leave the body as faeces. Functions also in vitamin K metabolism. The large intestine is subdivided further in order into regions: cecum, colon (ascending, transverse, descending, and sigmoid), and rectum.
- (More? Intestine Development | Gastrointestinal Tract Development | Lecture - Gastrointestinal Development)
- (congenital laryngeal webs) Laryngeal abnormality due to embryonic (week 10) incomplete recanalization of the laryngotracheal tube. Rare abnormality occuring mainly at the level of the vocal folds (glottis).
- Early embryonic foregut developmental feature, forms on the anterior (ventral) wall of the pharynx and gives rise to larynx, trachea and entire respiratory tree. In humans, this feature is the first indication of respiratory development and appears during week 4.
- (More? Respiratory System Development | Gastrointestinal Tract Development | Image B3 - Embryo stage 13 | Image B4 - Embryo stage 13)
- Site of the the vocal folds in the neck. Embryologically develops from the foregut with the lining derived from endoderm and the cartilage from pharyngeal arch 4 and 6. Beginning as a simple foregut groove, the laryngotracheal groove which folds to form the laryngotracheal bud, then the larynx and trachea.
- (More? Respiratory System Development | Gastrointestinal Tract Development | Image B5 - Embryo stage 13 | Image B6 - Embryo stage 13)
last menstrual period
- (LMP) Clinical term used to describe the menstrual period (menses) that occurs before a pregnancy and is used as the date to calculate clinical pregnancy development (gestational age). Note that in humans this is approximately two weeks different from embryonic development, which begins at fertilization around the mid-point of the menstrual cycle. The interval between the beginning of the LMP and fertilisation can have a wide range (7 to 25 days), due to both maternal (menstrual cycle timing and ovulation) and fetal (blastocyst implantation) variations.
late-gestation lung protein 1
- (LGL1) A glycoprotein secreted by fetal lung mesenchyme and fetal kidney, involved in retinoic acid stimulated branching morphogenesis.
- An anatomical description for away from the midline (paired with medial, towards the midline).
lateral cervical anomaly
- (branchial cleft anomaly) Abnormality which can be four different types: first, second, third and fourth.
- (More? Head Development)
- A neural tube defect where herniation of the meninges occurs through a dilated neural foramina. One of the three classes of spinal meningocele (simple, lateral and anterior sacral meningocele).
- (Pb) An environmental heavy metal linked to developmental defects. Lead was historically present in many products (piping, paint, dyes, petrol) leading to accumulation in industrial and urban environments.
- (More? Abnormal Development - Lead | Abnormal Development - Heavy Metals | Abnormal Development - Environmental )
- Class of carbohydrate-binding proteins originally found in plants. Can be used to specifically bind/identify glycoproteins.
- Reproductive change in female mice housed together (in groups) results in a synchronization of their estrus cycles. In addition, the extended absence of male pheromones leads to a state of anestrus (lack of a normal estrus cycle).
- (More? Mouse Estrous Cycle)
- (uterine fibroids) A benign smooth muscle tumor of the uterus. These are also one of the most common gynecologic neoplasm in women, often detected on pelvic examination or by a range of diagnostic tools (endovaginal sonography, sonohysterography, hysterosalpingography, magnetic resonance imaging, computerized tomography, radionucleotide scanning, serum markers). The condition is difficult to distinguish from another uterine disease adenomyosis.
- (Greek, leptos = thin) a polypeptide hormone (16 kDa) produced in adipose and many other tissues. Hormone receptor (OB-R, leptin receptors) found in many different tissues. Hormone levels associated with fertility and reproductive maturity in many species. Other hormonal roles include: satiety, adiposity, and metabolism, body mass control, angiogenesis, immunity, wound healing, bone remodelling cardiovascular function, and specific metabolic pathways.
- (leptotene phase, leptonema; Greek, leptotene = "thin threads") A meiotic cell division stage seen during prophase I. Prophase I is further divided into 5 stages based upon changes associated with the synaptonemal complex structure that forms between two pairs of homologous chromosomes. In leptotene, the duplicated paired homologs condense.
- The smaller peritoneal fold of splanchnic mesoderm extending from lesser curvature of the stomach to liver formed from the ventral mesentery at this level of the gastrointestinal tract. The second larger greater omentum extends from the greater curvature of the stomach and hanging down "like an apron" ventrally over the small intestine.
leukemia inhibitory factor
- (More? PMID 19470478)
- (Greek, leukos = clear or white; kytos = cell) Scientific name for the white blood cell. Blood cells are part of a liquid connective tissue and is mesoderm in origin. In the adult, these cells are formed from blood stem cells located in bone marrow cavities mainly found in long bones. The granulocytes (neutrophils, basophils, and eosinophils) are characterized by the presence of cytoplasmic granules and are named according to their histological staining properties. The agranulocytes (lymphocytes, monocytes, and macrophages) are characterized by the apparent absence of obvious granules in their cytoplasm.
- A synthetic progesterone used in oral contraceptives and as an emergency contraceptive. (Other Progestins: 3-keto-desogestrel, dienogest, drospirenone, Nestorone, nomegestrol acetate and trimegestone) Note that Trimegestone and Nestorone are currently the most potent fourth-generation progestins with no androgenic or estrogenic actions.
- (More? Menstrual Cycle)
- (interstitial cell) Male gonad (testis) cell which secrete the androgen testosterone, beginning in the fetus. These cells are named after Franz von Leydig (1821 - 1908) a German scientist who histologically described these cells.
Leydig cell hypoplasia
- (LCH) or male pseudohermaphroditism is an autosomal recessive disorder in individuals with a 46,XY karyotype with a predominantly female phenotype
- Acronym for late-gestation lung protein 1, a glycoprotein secreted by fetal lung mesenchyme and fetal kidney, involved in retinoic acid stimulated branching morphogenesis.
- The postnatal ligament remnant structure formed from the ductus arteriosus, a prenatal vascular shunt.
- (ligamentum teres uteri, Hunter's ligament) The round ligament of uterus which maintains the ventral uterine position.
- The postnatal ligament remnant of the ductus venosus, a vessel which prenatally connects (shunts) the portal and umbilical veins to the inferior vena cava and also acts to protect the fetus from placental over-circulation. In the adult, the ligament is the anatomical landmark between the medial and lateral portions of the left portal vein.
- (Latin, ligare = to bind) A molecule that binds to a specific binding site on a protein (receptor), ligands occur as a variety of different molecules.
- Acronym for LIM domain proteins, named after the worm proteins (Lin11 and Mec3). LIM homeodomain (LIM-hd) proteins are transcription factors and for vertebrates specify cell lineage and organ development (also involved in cytoskeleton organization and oncogenesis). Ldb genes encode LIM domain-binding (Ldb) factors and have been identified as a regulator of neural tube differentiation at the spinal cord level (Lim hox gene expression).
- (More? Worm Development)
- (Old English lim) Anatomical term used to describe appendages, humans have specialized upper limbs (arms) and lower limbs (legs) that develop initially as limb buds at different times using similar developmental patterning mechanisms to establish limb axes. The bones within the limbs forms the appendicular skeleton. The skeletal muscle within the limbs is derived from specific somite levels.
- (Old English lim) The initial embryonic structures that will form the paired upper and lower limbs. The buds form in a rostrocaudal sequence, the upper before the lower limbs, in humans about a 2 day difference. Buds appear as ectoderm and mesoderm "paddle-like" projections from the trunk at the segmental levels corresponding to their innervation and are patterned in 3 axes by specific regional signals. Somite mesoderm contributes the skeletal muscle within the limbs.
limb-girdle muscular dystrophy type 2A
- (LGMD2A) Human recessive genetic disorder caused by mutations in the calpain 3 (CAPN3) gene.
- (lin-35 Rb) A retinoblastoma tumor suppressor (Rb) related gene in worm C. elegans, identified as a synthetic multivulva (synMuv) class B gene.
- (Leucine-Rich Repeat Neuronal Protein, LRRN6A) gene family encoding type 1 transmembrane proteins, with 12 extracellular leucine rich repeats, an immunoglobulin C2 domain and a short intracellular tail. Expressed in neural and nonneronal developing tissues: developing cranial ganglia (trigeminal, facio-acoustic) and dorsal root ganglia, somites (dermomyotome), spinal cord (motor horn), otic vesicle and developing gut epithelium.
- (More? Neural System Development | OMIM - Leucine-Rich Repeat Neuronal Protein | Haines BP, Rigby PW. Expression of the Lingo/LERN gene family during mouse embryogenesis. Gene Expr Patterns. 2008 Jan;8(2):79-86.)
- (Latin, lingua = tongue) Term used to describe structures and features related to the tongue: lingual papilla, lingual plate, lingual plexus, lingual thyroid nodule.
- (Lp) lipoprotein particle formed in insect cells that has been identified as having a role in Hedgehog (Hh) signaling during development. Lipophorins (Lp) contain two apolipophorins I and II (ApoLI and ApoLII). Similar lipoprotein particles can be found in vertebrates and consist of a phospholipid monolayer surrounding a core of esterified cholesterol and triglycerides which is scaffolded by apolipoproteins. Reference: Callejo A, Culi J, Guerrero I. Patched, the receptor of Hedgehog, is a lipoprotein receptor. Proc Natl Acad Sci U S A. 2008 Jan 15
- (follicular fluid) The fluid found in the cavity or antrum of a developing ovarian follicle.
- (smooth brain) A developmental brain abnormality resulting from an absence (agyria) or the paucity (pachygyria) of cerebral convolutions, caused by defects in neuronal migration by the gene LIS1. Two major types: Miller–Dieker syndrome (MDS) and isolated lissencephaly sequence (ILS).
- (L. monocytogenes) A large family of bacteria found throughout the environment (soil, dust, water, unwashed raw produce, fish, undercooked poultry, prepared meats such as hot dogs and deli meats, and faeces of domestic and wild animals). Listeria monocytogenes is the specific bacteria form that causes the infection "listeriosis". The most common human source of infection is contaminated foods: delicatessan meats, unpasteurized milk or dairy products, soft cheeses, and pate. Once infected, listeria lives in the gastrointestinal Maternal listeriosis with symptoms has a risk (2-14 days after maternal infection) of miscarriage, stillbirth, uterine infection, premature labor, and death in the newborn period.
- An infection caused by the listeria family of bacteria, pregnancy greatly increases the risk of in mammalian species. Once infected, listeria lives in the gastrointestinal and maternal listeriosis with symptoms has a risk (2-14 days after maternal infection) of miscarriage, stillbirth, uterine infection, premature labor, and death in the newborn period.
- (hernia of the Meckel diverticulum) The protrusion of a Meckel diverticulum through a potential abdominal opening. The hernia sites are: inguinal (50%), umbilical (20%), and femoral (20%). Named after Alexis de Littre (1700) who initially reported ileal diverticula.
- The delivery of one or more babies with any sign of life. The World Health Organization (WHO) definition:
- "Live birth is the complete expulsion or extraction from its mother of a product of conception, irrespective ot the duration of pregancy, which, after separation, breathes or shows evidence of life, such as the beating of the heart, pulsation of the umbilical cord, or definite movement of voluntary muscles, whether or not the umbilical cord has been cut or the placenta is attached; each product of such a birth is considered liveborn."
- (More? Birth)
- See the term live birth definition above.
- (More? Birth)
- Acronym for Last Menstrual Period that occurred before a pregnancy and is used as the date to calculate clinical pregnancy development (gestational age).
- A Lim homeodomain-containing transcription factor shown to have many developmental roles including a role in mammalian inner ear development (maintaining proper neurogenic, sensory, and non-sensory domains).
- (More? Molecular Development)
- Anatomical term referring to a projecting part or subdivision of an organ or gland, it can also be further subdivided into a number of smaller lobules.
- Term used to describe a small lobe. Can be used to describe part of a gland, ear, organ structure (lung, liver).
- Clinical term for the maternal uterine (placental) discharge occurring during the 2-4 weeks after birth, consisting of blood plus mucous.
- (LRP) Two of these receptors 5 and 6 (LRP5 and LRP6) act as Wnt co-receptors for the canonical β-catenin pathway. Protein stricture contains in the cytoplasmic domain five conserved PPPSPxS motifs, for signaling and act as phosphorylation-dependent docking sites for the scaffolding protein Axin. LRP6 as a Wnt co-receptor is essential for embryogenesis.
- A gene encodes a secreted signaling protein that signals formation of boundaries between groups of cells during development. One mechanism is by modifying Notch and inhibits signaling through the Notch pathway. In neural tube, regulates early neural crest differentiation. In mesoderm, regulates somite formation (segmentation).
- The term describing the primordia of lung development in the respiratory embryonic stage. Foregut endoderm branches into the surrounding visceral mesoderm, forming the trachea, which brances again into the bronchi and thsi process is repeated over and over again through development. Establishing the major respiratory branches first, followed by minor branches, then terminal branches, then immature alveoli which later mature to form teh functional end structures of the lung.
lung embryonic stage
- Term used to describe the earliest lung development stage of the histological/developmental stages (pseudoglandular, fetal canalicular, terminal sac, alveolar). This stage occurs during the embryonic period from the earilest of lung bud development.
- (secretory phase) The phase of the menstrual cycle following [[O#ovulation|ovulation]. The term refers to within the ovary the ovulating follicle forming the corpus luteum.
- (More? Menstrual Cycle)
- (LH, gonadotropin, lutropin, Interstitial Cell Stimulating Hormone, ICSH) Glycoprotein hormone releasd from anterior pituitary hormone that acts on the gonad and has a role in male and female reproduction. In female, increase in concentration during the menstrual cycle triggers ovulation (release of the oocyte). In male, stimulates testis interstital cell (Leydig cell) production of testosterone. Gonadotrophins have been used clinically in humans for the treatment of female infertility.
- alternative spelling, (LH, gonadotropin) (LH, gonadotropin, lutropin, Interstitial Cell Stimulating Hormone, ICSH) Glycoprotein hormone releasd from anterior pituitary hormone that acts on the gonad and has a role in male and female reproduction. In female, increase in concentration during the menstrual cycle triggers ovulation (release of the oocyte). In male, stimulates testis interstital cell (Leydig cell) production of testosterone.
luteinizing hormone/chorionic gonadotropin receptor
- (LHCGR) a G protein-coupled receptor expressed in male testis (Leydig cells) and female ovary (granulosa-lutein and theca cells)
- (More? Genital System Development)
- The process of corpus luteum (CL) degradation, in the absence of pregnancy, occurring at the end of the reproductive cycle luteal phase for both the menstrual cycle and the estrous cycle. In the estrous cycle degradation is triggered by prostaglandin and oxytocin.
- (More? Menstrual Cycle)
- Caused by a bacterium, Borrelia burgdorferi, which was cultured from the midgut of Ixodes ticks in the mid-1980s. Named after a small town of Lyme in Connecticut where in the mid-1970s this diesease was initially identified.
- Term describing the spherical body formed initially by vein endothelial cells that is the first precursor to lymph node development. Mesenchymal cells surround and invade the sac contributing the lymph node stroma.
- (More? Lymph Node Development)
- Term used to describe the development or growth of lymphatic vessels. This process of vessel development occurs during development, and postnatally during physiological and pathological processes.
- (More? Lymphatic Development)
- A disfiguring vascular malformation of early childhood (mostly before 2 years of age) occuring in soft tissues of the head and neck or axilla, may also occur in the limbs, trunk, viscera and serous cavities.
- (More? Lymphatic Development)
- Lymphatic vessel term describing the functional unit of a lymph vessel lying between two semilunar (half moon-shaped) valves.
- abnormal accumulation of interstitial fluid in tissues due to a lack of lymphatic drainage, which in turn leads to localized swelling.
- (More? Lymphatic Development)
- (lymphoid hematopoiesis, lymphocytopoiesis) the process of generating lymphocytes (the immune cells) in various tissues (bone marrow, lymph nodes, thymus and spleen).
- A form of virus closely related to classical rabies (though genetically and serologically distinct). A form of this virus carried in bats (Australian bat lyssavirus) has been associated with two human fatalities. Effects on embryonic development are unknown.
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.