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Yr 1 - Embryology > Glossary > Flashcards

Glossary Flashcards

1
Q

Hydatidiform Mole

A

A sperm fertilises an enucleated egg, followed by duplication of the paternal chromosomes to restore a diploid number. Trophoblasts form placental tissue, but with no embryo. Moles only express parental genes and secrete high concentrations of hCG.

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2
Q

Ectopic

A

Outside the uterus.

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3
Q

Placenta Previa

A

Low lying placenta within the uterus that partially or completely covers the cervix. Caused by implantation low in the uterus.

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4
Q

Anencephaly

A

Congenital malformation in which the anterior neuropore fails to close, leading to failure of formation of higher brain centres. Results in large part of skull and cerebral hemispheres of brain are absent.

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5
Q

Acrosome Reaction

A

Release of degrative enzymes from acrosome on head of sperm (induced by zona proteins). Assists in sperm penetration of zona pellucida.

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6
Q

Cleavage

A

Division of cells in the early embryo

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7
Q

Corona radiata

A

Innermost layer of cumulus oophorus adjacent to the zona pellucida

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8
Q

Cortical reaction

A

Occurs after fertilisation. Cortical granules released by the egg prevent polyspermy

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9
Q

Fertilisation

A

Fusion of male and female gametes (sperm&ovum)

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10
Q

Gametogenesis

A

Formation of male and female sex cells

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11
Q

Gametes

A

A haploid cell (sex cell) that has undergone meiosis

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12
Q

Meiosis

A

Cell division to produce haploid cells

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13
Q

Mitosis

A

Process where one cell divides giving rise to 2 daughter cells, each with 46 chromosomes

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14
Q

Pronuclei

A

Either of a pair of gametic nuclei after fertilisation but before fusion leads to formation of nucleus of the zygote

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15
Q

Trisomy 21

A

Downs syndrome. Genetic disorder caused by presence of 3rd copy of chromosome 21

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16
Q

Zona Pellucida

A

Specialised layer surrounding the plasma membrane of the ovum

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17
Q

Zygote

A

First structure formed after fertilisation by fusion of a sperm and ovum

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18
Q

Blastomeres

A

Cells formed by cleavage of fertilised ovum

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19
Q

Blastocyst

A

Stage of embryogenesis at the time of implantation where outer trophoblast cells form a fluid-filled sphere with a small group of embryo blast cells (inner cell mass) at one pol.

After fertilisation, cells in zygote cleave to form a hollow ball with a layer of cells on outside, called a blastocyst

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20
Q

Embryoblast

A

Cells that form inner cell mass. Goes on to form the embryo proper.

Differentiates into the epiblast and hypoblast cells.

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21
Q

Trophoblast

A

Outer cells of blastocyst. Important in development of support structures that are important in implantation and nourishment of embryo.

Differentiate into cytotrophoblast and syncytiotrophoblast cells

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22
Q

Teratogen

A

A factor that causes a birth defect, such as a drug or environmental toxicant

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23
Q

Spina Bifida

A

Neural tube defect that involves incomplete formation of the vertebral arches and may or may not involve the meninges (meningeocele) and neural tissue (mylomeningeocele)

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24
Q

Outer Cell Mass

A

Cells that surround the blastocyst cavity and cover the inner cell mass. Will form the trophoblast.

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25
Q

Morula

A

Cleavage of the developing zygote to form a ball of 16-32 cells

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26
Q

Microcephaly

A

A condition in which the brain fails to form properly, resulting in a head with an abnormally small circumference

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27
Q

Inner Cell Mass

A

Cluster of cells segregated to one pole of the blastocyst and from which the entire embryo develops

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28
Q

Capacitation

A

A period of sperm conditioning in the female reproductive tracts lasting about 7 hours that is required for sperm to be able to fertilise the egg

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29
Q

Cytotrophoblast

A

Proliferative inner layer of trophoblast

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30
Q

Lithopaedian

A

Stone baby. A foetus dies during an ectopic pregnancy but is too large to be resorbed by the body and so is calcified.

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31
Q

Syncytiotrophoblast

A

Outer multinucleated layer of trophoblast that serves to invade the endometrium of the uterus

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32
Q

Bilaminar Disc

A

Stage in week 2 development when the inner cell mass/embryoblasts differentiate into a layer of epiblast cells and a layer of hypoblast cells

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33
Q

Epiblast

A

Dorsal (top) layer of cells comprising the bilaminar disc during the 2nd week of development. The hypoblast forms the ventral layer. All tissues of the embryo are derived from the epiblast

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34
Q

Hypoblast

A

Ventral layer of bilaminar germ disc. Contributes to formation of yolk sac and extra embryonic mesoderm but not to tissues of embryo

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35
Q

Hydrocephalus

A

Condition in which there is a build-up of CSF within the brain

36
Q

Ventral

A

Towards the front

37
Q

Dorsal

A

Towards the back

38
Q

Primary Yolk Sac

A

Formed by migration of hypoblast cells around blastocyst cavity. It is a transient structure replaced by definitive yolk sac

39
Q

Extraembryonic Mesoderm

A

Layer formed by hypoblast/1ary yolk sac. Surrounds the developing embryo and forms the connecting stalk. The chorionic cavity also forms within this layer

40
Q

Chorionic Cavity

A

Space formed between extraembryonic mesoderm lining the cytotrophoblast and that surrounding the yolk sac and embryo. This cavity will eventually be obliterated by expansion of the amniotic cavity and fusion of the amnion with the chorion

41
Q

Trophoblastic Lacuna

A

Irregular spaces within syncytiotrophoblast that join together to form larger spaces. Maternal blood flows into the lacuna when the syncytiotrophoblasts have established a uteroplacental circulation

42
Q

Connecting Stalk

A

Extraembryonic mesoderm that connect the embryo to the placenta. It contains the allantois and will be incorporated into the umbilical cord along with the vitelline duct and yolk sac

43
Q

Definitive Yolk Sac

A

One of the 3 embryonic cavities form by migration of hypoblast cells around the blastocyst cavity to form the 1ary yolk sac. The 1ary yolk sac is pinched off and degenerates. A second wave of hypoblast migration produces a new membrane and the definitive yolk sac

44
Q

Situs Inversus

A

Complete reversal of left-axis. The left and right side of the body are switched around.

45
Q

Primitive Streak

A

A groove formed on the dorsal aspect of the embryo in the epiblast. Appears at the caudal end at the bilaminar disc stage and marks the beginning of gastrulation. Epiblast cells migrate through the primitive streak to form 3 germ layers (endoderm, mesoderm and ectoderm)

46
Q

Caudal

A

Tail end

47
Q

Cranial

A

Head end

48
Q

Dextrocardia

A

Rare condition in which apex of heart points to right (opposite side to normal anatomical position of heart)

49
Q

Endoderm

A

1st germ layer formed during gastrulation. The most internal layer. Goes on to form lining of gut tube and its derivatives

50
Q

Mesoderm

A

2nd germ layer formed during gastrulation. The middle layer. Goes on to become organised (paraxial mesoderm, intermediate mesoderm, lateral plate mesoderm)

51
Q

Ectoderm

A

3rd germ layer formed during gastrulation. Most external layer. Goes on to form skin, neural tube etc

52
Q

Gastrulation

A

Process that forms 3 germ layers by migration of epiblast cells through primitive streak. Formation of primitive streak marks start of gastrulation

53
Q

Germ Layers

A

3 basic cell layers formed by gastrulation. The endoderm, mesoderm, ectoderm go on to form all systems in the embryo.

54
Q

Paraxial Mesoderm

A

Mesoderm tissue next to midline. Responsible for forming somites

55
Q

Intermediate Mesoderm

A

Organised area of mesoderm between the paraxial and lateral plate mesoderm. Gives rise to a great deal of the urogenital system

56
Q

Lateral Plate Mesoderm

A

Organised area of mesoderm that splits into parietal layer that surrounds the body wall and a splanchnic (visceral) layer that surrounds the organs

57
Q

Meningeocele

A

Failure of vertebral arch to form correctly (spina bifida) with meninges protruding through gap

58
Q

Myelomeningeocele

A

Neural tube defect that involves failure of vertebral arches to form correctly with protrusion of the meninges and spinal cord

59
Q

Anterior Neuropore

A

Cranial opening of neural tube. Closes by day 25

60
Q

Posterior Neuropore

A

Caudal opening of neural tube. Closes by day 28

61
Q

Notochord

A

An extended column of cells in the midline that forms as the primitive streak regresses. Induces neurulation and induces the sclerotome to form vertebrae

62
Q

Sclerotome

A

Area of the somite that forms vertebrae

63
Q

Sacrococcygeal Teratoma

A

Formed by excessive formation of mesoderm because of increased number of epiblast cells migrating through the primitive streak. Usually caused by persistent primitive streak

64
Q

Rachischisis

A

Failure of the posterior neuropore to close. As a result, the tube does not separate from the surface ectoderm and the neural tissue is exposed to the external environment. Leads to motor and sensory deficits and an increase risk of infection

65
Q

Neurulation

A

Process to form the neural tube. Thickening of the ectoderm overlying the notochord to form neuroectoderm and the neural plate. Elevation of the neural plate to form neural folds which fuse to form a neural tube. This tube then separates from the overlying surface ectoderm to complete neurulation

66
Q

Neural Tube

A

The result of neurulation. Once the neural folds fuse, the resulting tube separates from the overlying ectoderm.

67
Q

Neural Crest Cells

A

Cells of the neuroepithelium that form at the edges of the neural folds. These cells to migrate to form numerous different structures in different areas of the body.

68
Q

Myotome

A

Muscle forming region of a somite

69
Q

Sirenomelia

A

Mermaid Syndrome. Caused by insufficient formation of the mesoderm in the caudal region due to lack of epiblast cells migrating through the primitive streak. Usually caused by the premature regression of the primitive streak preventing enough epiblasts migrating through the primitive streak to form the mesoderm.

70
Q

Dermatome

A

Area of the somite that forms the dermis of the skin of the back

71
Q

Somite

A

Derived from the paraxial mesoderm that organises to form segmental blocks either side of the neural tube. Differentiates into the sclerotome (forms the vertebrae), myotome (muscles of the back) and dermatome (dermis of the skin)

72
Q

Vitelline Duct

A

Connection between the yolk sac and the developing midgut

73
Q

Cloacal Membrane

A

Membrane at the caudal end formed by adhesion between epiblast and hypoblast cells. It later covers the cloaca, a chamber where the gut and urinary system drain into before the chamber is segregated

74
Q

Oropharyngeal Membrane

A

Membrane formed at the cranial end of the embryonic disc by adhesion of epiblast and hypoblast cells. Goes on to cover the opening of the oral cavity and pharynx

75
Q

Parietal Mesoderm

A

Mesoderm that is concerned with the body wall. Formed from splitting of the lateral plate mesoderm into parietal and visceral (splanchnic layers)

76
Q

Splanchnic (visceral) Mesoderm

A

Mesoderm that is concerned with lining the outside of the gut and its derivatives. Formed from splitting of the lateral plate mesoderm into parietal and visceral (splanchnic layers)

77
Q

Oligospermia

A

Deficiency of spermatozoa in the semen

78
Q

Gastroschisis

A

Ventral body wall defect caused by failure of the lateral body walls to fuse in the midline in the abdominal region. Results in intestines residing outside the abdominal cavity

79
Q

Ectopia Cordis

A

Ventral body wall defect caused by failure of the lateral body walls to fuse in the midline in the thorax region. As a result, the heart lies outside the thoracic cavity

80
Q

Azoospermia

A

Medical condition in which a male’s semen contains no mature spermatozoa

81
Q

Amnion

A

Membrane derived from the epiblast that surrounds the fluid-filled cavity around the embryo and foetus. The fluid cushions the foetus and forms a hydrostatic wedge to assist with dilation of the cervix during labour.

82
Q

Allantois

A

Waste storage organ. Connected to the developing foetal bladder

83
Q

Gestation

A

Process of development within the uterus

84
Q

Cumulus Oophorus

A

Collection of cells that surround the oocyte

85
Q

Corona Radiate

A

Innermost layer of the cumulus oophorus adjacent to the zona pellucid

86
Q

Chromosomal

A

DNA molecule with some/all genetic material of an organism

87
Q

Necrotic Tissue

A

Dead or devitalised tissue - must be removed for healing to take place

Yr 1 - Embryology (11 decks)

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