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Link to the Original UNSW Embryology Glossary B

B-Myb

A protein transcription factor and a member of the A-Myb, B-Myb (MybL2) and C-Myb family found in all proliferating cells. B-Myb is the only member of this Myb family specific to embryonic stem cells and is required for both cycle progression and mitotic spindle formation. In mice, lack of the gene leads to early embryonic death, after implantation due to defects on the inner cell mass.

bacteriophage

(Greek, bakterion = little rod + phagein = to eat) or phage A virus that infects bacteria.

Balbiani body

(mitochondrial cloud) collection of cell organelles (mitochondria, ER, and granulofibrillar material) asymmetrically located beside the nucleus in very young oocytes in some species. Appears similar to germinal granule precursors seen some species that contain a definitive germ plasm (flies, worms, and frogs).

(More? PNAS - Mouse oocytes within germ cell cysts and primordial follicles contain a Balbiani body)

Ballottement

(French, ballottement = "a tossing about") Clinical palpatory test (clinical week 6 - 20) used to detect pregnancy, when the lower uterine segment (or cervix) is tapped by examiner's finger, the fetus floats upward, then sinks again and can be felt on the finger. (not considered diagnostic as it can also be elicited in the presence ovarian cysts)

Bardet-Biedl syndrome

(BBS) is an abnormality with triallelic inheritance and is characterized by a rangne of multisystem abnormalities (cone-rod dystrophy, truncal obesity, postaxial polydactyly, cognitive impairment, neural development, male hypogonadotrophic hypogonadism, complex female genitourinary malformations, and renal dysfunction).

(More? Vision Abnormalities | Urogenital Abnormalities | OMIM - Bardet-Biedl syndrome | GeneReviews - Bardet-Biedl syndrome)

Barker Hypothesis

(Fetal Origins Hypothesis) Term named after the researcher, Barker who began a statistical analysis in the UK, of low birth weight data (early 1900's). The hypothesis has since been renamed as the Fetal Origins Hypothesis and proposes that in utero influences can lead too permanent changes in embryo/fetus, low birth weight, which predisposes to chronic disease in adult life.

(More? Fetal Origins Hypothesis Notes)

Barr body

Name given to a visible cellular feature produced by the inactivation of a single X chromosome in females.

Bartholin Gland

(= greater vestibular gland) female genital tract glands which secretes mucous. The equivalent male gland are the Bulbourethral glands.

(More? Urogenital Notes)

basal body

The base of an axoneme; a cylinder about 500 nm long that resembles a centriole; the microtubule organizing center of a cilium or a eukaryotic flagellum.

basal body temperature

The temperature taken at its lowest point in the day, typically in the morning before getting out of bed. Note body temperature changes are used to approximately establish ovulation (increases bbt).

(More? Human Menstrual Cycle | Hyperthermia)

base

Another term for anucleotide (usually a t c g).

(More? DNA Notes)

base pair

Double stranded DNA has nucleotides A-T, C-G, paired by hydrogen bonds (2 for AT, 3 for GC). Note this means that GC is harder to separate that AT.

(More? DNA Notes)

Bayley Scales of Infant Development

(BSID) A postnatal (from 1 to 42 months) neurological assessment scale used in screening and diagnosis of development using 178 item mental scale and the 111 item motor scale, the original BSID was revised in 1993 to version 2 (BSID-II). THere are several alternative assessments tests and tasks including: Alberta Infant Motor Scale (AIMS), Fagan Test of Infant Intelligence (FTII), Peabody Developmental Motor Scale II (PDMS-2) Comprehensive Developmental Inventory for Infants and Toddlers (CDIIT), Means-End Problem-Solving Task, Operant Discrimination Learning, Mobile/Train Conjugate Reinforcement Tasks, The Transparent Barrier Detour Task, The A-not-B Task

(More? Neural Notes | Postnatal Development)

biliary cells

The liver epithelial cell formed from hepatoblast differentiation (hepatoblasts form from endoderm).

(More? Gastrointestinal Tract - Liver | GIT Notes)

Billings Ovulation Method

(BOM, Ovulation Method) A self-observation method for women use to monitor their fertility.

biopsy

A fragment of tissue removed for (clinical/pathological/medical) study under the microscope.

biotinidase

An enzyme required to free biotin from its bound form for use. Biotinidase deficiency can be detected in newborn screening and treated with daily biotin supplementation.

biparietal diameter

An ultrasound measurement of Biparietal Diameter (BPD) is used to determine fetal age and normal development (small/large/abnormal) parameters. Measured as the diameter between the 2 sides of the head, used in clinical ultrasound measurements after 13 weeks (2.4 cm) to term (9.5 cm). It is one of the four typical ultrasound assessments of fetal size and age: Biparietal Diameter (BPD), [H.htm#head_circumference Head Circumference] (HC), [A.htm#abdominal_circumference Abdominal Circumference] (AC), and [F.htm#femur_length Femur Length] (FL).

(More? Ultrasound | Head Notes) | Fetal Notes | Birth Notes)

birth

(parturition) Term describing the pysiological process of offspring (child) being born.

(More? Normal Development - Birth)

birth rate

A statictical term typically calculated by dividing the number of live births in a population in a year by the mid-year resident population.

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

bladder exstrophy

(Greek, ekstriphein = "turn inside out") A congenital malformation with bladder open to ventral wall of abdomen (between umbilicus and pubic symphysis) and may have other anomolies associated with failure of closure of abdominal wall and bladder (epispadias, pubic bone anomolies).

(More? Urogenital Abnormalities)

blastema

Term used to describe an undifferentiated mass of cells.

(More? [W.htm#Wilms_tumour Wilm's tumour])

blastocoel

A fluid-filled cavity that exists in early development within the blastocyst. Initially the dividing cells form a solid cellular mass (morula) in which the cavity will form. In humans this cavity is present during the first and second week of development.

(More? Week 1 - Blastocyst)

blastocyst

(Greek, blastos = sprout + cystos = cavity) Term used to describe the hollow cellular mass that forms in early development. The blastocyst consists of cells forming an outer trophoblast layer, an inner cell mass and a fluid-filled cavity. The blastocyst inner cell mass is the source of true embryonic stem cells capable of forming all cell types within the embryo. In humans, this stage occurs in the first and second weeks after the [Z.htm#zygote zygote] forms a solid cellular mass ([M.htm#morula morula] stage) and before implantation.

(More? Week 1 - Blastocyst | Week 2 Notes | Stem Cell Notes)

blastopore

The opening formed by the gastrulating cell migration in early blastula to gastrula development.

(More? Week 2 Notes | Week 3 Notes | Frog Development - Gastrulation)

blastula

(Greek, blastos = sprout = little sprout) A stage of an animal embryo that consists of a fluid-filled sphere of cells on the surface.

(More? Week 2 Notes)

blighted ovum

(missed abortion, early fetal loss) A historic term now called replaced by ===early fetal loss===, describing embryo loss that occurs in first trimester.

BLIMP1

DNA-binding transcriptional repressor (zinc-finger) which has a role in both embryo development and adult tissues by regulating (repressing) p53 expression allowing normal cell growth.

(More? PNAS Yan J, Jiang J, Lim CA, Wu Q, Ng HH, Chin KC. BLIMP1 regulates cell growth through repression of p53 transcription. Proc Natl Acad Sci U S A. 2007 Jan 30)

blood islands

The initial small patches which form within mesoderm that differentiate into both the blood vessel wall and blood cells. These islands enlarge and connect together to form the initial vascular beds.

(More? Cardiovascular System - Blood)

BMI

Acronym for Body Mass Index which is a measure of body composition. Used to determine adiposity, that is fat content, which has influences upon growth and health.

Bmi1

A proto-oncogene protein located in the nucleus, which is a member of the Polycomb-group gene family (required to maintain the repression of homeotic genes). Expressed in range of stem cells including hematopoietic, neural and intestinal stem cells. Human BMI-1 gene on the short arm of chromosome 10 (10p13).

Sangiorgi E, Capecchi MR. Bmi1 is expressed in vivo in intestinal stem cells. Nat Genet. 2008 Jul;40(7):915-20.

(More? Gastrointestinal Tract Development | OMIM - proto-oncogene BMI-1 |

BOC

Acronym for Brother of Cdon a cell surface receptor. CDON is also a acronym for Cell adhesion molecule-regulated/downregulated by oncogenes. Both Boc and Cdon are cell surface receptors (for sonic hedgehog) of the immunoglobulin (Ig)/fibronectin type III that interact with each other, are coexpressed and involved in neural and muscle development.

(More? Molecular Development - sonic hedgehog | OMIM - BROTHER OF CDON)

bombesin receptor

A cell receptor family associated mainly with gastrointestinal function (motility and secretion) and neural functions (circadian rhythm, thermoregulation anxiety/fear responses, food intake). In mammals, these G protein-coupled receptors are: neuromedin B, gastrin-releasing peptide, and orphan receptor bombesin receptor subtype 3.

(More? GIT Development | Endocrine Development |)

bone

A connective tissue forming the main structural component of the skeleton. There are two processes of bone formation (ossification): endochondrial, replacing a pre-existing cartilage template (most of the skeleton); or intramembranous, ossification directly from a membrane (cranial vault, scapula). Adult bone gross histology is described as either trabecular bone (also called cancellous or spongy bone) or compact bone (does not have any spaces or hollows).

(More? Musculoskeletal Development - Bone | Musculoskeletal Development | Blue Histology - Bone)

bone marrow

The cellular components found within the core of bones, mainly long bones, which contain the adult blood stem cell population and a range of other cell types. Generally described as either red marrow (myeloid tissue) or yellow marrow (mainly fat cells.)

(More? Musculoskeletal Development - Bone | Musculoskeletal Development)

bone marrow stromal cells

(BMSCs) These are pluripotental cells from bone marrow that can potentially differentiate into a range of connective tissue and muscle cell types (cardiomyocytes, rhabdomyocytes, hepatocytes, osteocytes, chondrocytes, tencoytes, adipocytes, smooth muscle cells). These cells have therefore been seen as a source of stem cells for tissue repair.

(More? Musculoskeletal Development - Bone | Musculoskeletal Development)

borrelia burgdorferi

(B. burgdorferi) The agent of Lyme disease in North America and Europe. A species of bacteria of the spirochete class of the genus Borrelia.

(More? Abnormal Development - Bacterial Infection)

Botallo's duct

(ductus arteriosus) A vascular shunt between pulmonary trunk and the aortic arch. This channel degenerates to form the ligamentum arteriosum (ligamentum Botalli). In preterm infants this channel may remain open as Patent Ductus Arteriosus. Named after Leonardo Botallo an Italian surgeon in Paris (1530-1600).

(More? Patent Ductus Arteriosus | PDA Image Heart Notes | Normal Development - Birth)

bowel

(intestine) Term used to describe the midgut and hindgut portion of the gastrointestinal tract running from after the stomach to the anus. Also subdivided into the small bowel (small intestine) and the large bowel (large intestine).

(More? Gastrointestinal Tract Notes)

BPD

Acronym for biparietal diameter, measurement between the 2 sides of the head, used in clinical ultrasound measurements after 13 weeks.

(More? Ultrasound Movies)

brachial plexus

(Latin, bracchium = arm) The mixed spinal nerves innervating the upper limb form a complex meshwork (crossing). (More? Neural Notes)

brachiocephalic trunk

(Latin, bracchium = arm, cephalicus = head) The blood vessel forming the first branch of the aortic arch, arises superolaterally and splits into the right subclavian and the right common carotid arteries. (More? Cardiovascular Notes)

brain

The general term for the central nervous system (CNS) component formed initially from the cranial end of the neural tube. The remainder of the CNS is the spinal cord. The brain forms initially as 3 primary brain vesicles which later form 5 secondary brain vesicles.

(More? Neural Notes)

breech

A birth term where the fetal buttocks are presented first, this can also occur in different forms depending on the fetal structure presentation (complete breech, frank breech, footing breech, knee breech).

(More? Normal Development - Birth | Birth Abnormalities)

Brek/Lmtk2

Acronym for brain-enriched kinase/lemur tyrosine kinase 2. Signaling protein member of the Aatyk family of kinases, mouse knockouts are infertile with azoospermia.

(More? Week 1 Notes)

broad ligament

Human female genital tract mesentery formed by a double fold of peritoneum that connects the [U.htm#uterus uterus] to the peritoneal floor and walls. Anatomically it has three parts: mesometrium (surrounding the [U.htm#uterus uterus]), mesosalpinx (surrounding the uterine tube) and mesovarium (surrounding the ovary).

(More? Genital System - Female)

bronchi

(Latin, bronchos = windpipe) Plural of bronchus, the two subdivisions of the trachea carrying air to the lungs. Embryologically forms as an endodermal outpocket of the foregut which branch (bronchiole, subdivision of the bronchus) as they grow.

(More? Respiratory Notes)

bronchiole

(Latin, bronchos = windpipe) A smaller branch subdivision of the bronchus.

(More? Respiratory Notes)

bronchus

(Latin, bronchos = windpipe) The individual division of the trachea carrying air to the lungs. Embryologically forms as an endodermal outpocket of the foregut which branch as they grow (bronchiole, subdivision of the bronchus).

(More? Respiratory Notes)

brown adipose

(brown fat) Neonatal specialized form of adipose tissue used in mammals to generate body temperature (thermogenic organ) by non-shivering thermogenesis. Adult fat (white adipose) cannot be used in this fashion. This form of adipose tissue is also seen in animals that hibernate.

(More? Musculoskeletal Development - Adipose)

Bruce Effect

Reproductive change in female mice, pheromones from a strange male can prevent embryo implantation in recently bred female.

(More? Mouse Development- Estrous Cycle)

buccal

(Latin, bucca = cheek) A term used to relate to the mouth (oral cavity).

(More? GIT Notes)

buccopharyngeal membrane

(oral membrane) (Latin, bucca = cheek) A membrane which forms the external upper membrane limit (cranial end) of the early gastrointestinal tract (GIT). This membrane develops during gastrulation by ectoderm and endoderm without a middle (intervening) layer of mesoderm. The membrane lies at the floor of the ventral depression (stomadeum) where the oral cavity will open and will breakdown to form the initial "oral opening" of the gastrointestinal tract. The equivilent membrane at the lower end of the gastrointestinal tract is the [C.htm#cloacal_membrane cloacal membrane].

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

Bulbourethral Gland

(= Cowper's Gland) A male genital tract gland which secretes a small amount of a thick clear mucous fluid prior to ejaculation, the alkaline content apparently buffers acidity of the urethra. The equivalent female gland are Bartholin's glands.

(More? Urogenital Notes)

bulbus cordis

A region of the early developing heart tube forming the common outflow tract.

Blood Pathway: sinus venosus -> atrium -> ventricle -> bulbus cordis (outflow tract)

(More? Heart Notes)

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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