Human Embryology Flashcards by Oscar Moores

Why is embryology studied?

history of prenatal origin
understand birth defects
to understand adult anatomy
understand adult illness’s and origins

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What are the embryological periods?

1st, 2nd, 3rd trimesters and pre-embryonic period

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What is the embryonic period? (organogenesis)

beginning of 4th week to end of 8th week

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What are the 3 germ layers and what do they give rise to

Ectoderm, Mesoderm, Endoderm

give rise to specific tissues and organs

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what is the period of the foetus?

beginning of 3rd month to birth

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What is gametogenesis?

process of production of male and female gametes from the primordial germ cells (PGC) via meiotic cell divisions

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What are male and female gametogenesis called?

male - spermatogenesis

female - oogenesis

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What are the principal goals of gametogenesis?

reduces chromosomal number of gametes from 46 (paired) to 23 (unpaired)

enhance genetic variability

starts at puberty in males and from fetal life in females

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What do chromosomal abnormalities lead to?

birth defects, spontaneous abortions, fertility

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What is fertilisation?

process of male and female gametes fuse to form a zygote

restores diploid number of chromosomes

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what is capacitation?

a sperm conditioning process within the female reproductive tract in preparation for fertilisation - only capacitated sperm can pass corona cells

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what is acrosome reaction?

release of enzymes needed to penetrate the zona pellucida (layer of ovum)

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what is the cortical reaction?

the oocyte releases lysosomal enzymes from cortical granules making the plasma membrane impenetrable to other sperm

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what is the zona reaction?

structure and composition of the zona pellucida is altered preventing polyspermy

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what causes male infertility?

how can it be treated?

quality and quantity of spermatozoa

assisted reproductive technology (ART)

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what causes female infertility?

multiple physiological and anatomical factors

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what is and when does cleavage happen

within week of fertilisation

rapid repeated mitotic cell division of zygote to produce blastomeres

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what is the purpose of cleavage?

form multicellular embryo (morula) from the single large zygote

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what is the process of compaction

inner (embryoblast) and outer (trophoblast) cell masses forming and polarity being established

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what is the blastocyst (inner mass) (2nd week)

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the fully developed morula wi/ fluid filled cavity

what is the bilaminar embryonic germ disc?

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a cluster of embryonic cells

inner cell mass (hypoblast) becomes embryo

outer cell mass (epiblast) becomes placenta and other fetal membranes

defines dorsal-ventral axis

Stem cell definition

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undifferentiated cell that can form specialised cell types

can be either embryonic (pluripotent) or adult stem cell (multipotent)

Pluripotent cell definition

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can form all mature cell types in body (other than placental & extraembryonic cells)

Multipotent cell definition

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can form more than one closely related mature cell type in body

Totipotent cell definition

can form all differentiated cells types in body

what is the primitive streak?

transient thickening longitudinal midline structure forms on day 15 in the bilaminar embryonic germ disc

what is gastulation?

process of epiblastic cell movements (ingression or invagination) through the primitive streak the leads to formation of the trilaminar germ disc

what is the principle goal of gastrulation

establish all major body axes, (cranio-caudal, medio-lateral, dorso-vental, left-right)

clinical implications of errors of gastrulation

caudal dyslasia (caudal regression syndrome), caudal or sacral agenesis dextrocardia (right side heart) heart/septal defects atrial/ventricular isomerism's/inversions

what does the ectodermal germ layer give rise to?

organs and structures that maintain contact with the outside world eg, skin, teeth, ear, nose, mouth

what does the mesodermal germ layer (paraxial) give rise to?

cranial connective tissue somitomeres (somites) develop with neural tube (segments of spine) can be counted according to age of embryo

what are the 3 parts of the mesodermal germ layer?

paraxial mesoderm intermediate mesoderm lateral plate mesoderm

what does the mesodermal germ layer (intermediate) give rise to?

urogenital system - primordial germ cells, gametes, gonads

what does the mesodermal layer (lateral plate) give rise to?

splits in 2 - parietal = cavity walls visceral - wall of gut tube dermis of skin, limbs, bones, connective tissue, muscle

what does the endodermal germ layer give rise to?

epithelial lining of GI tract

what is morphogenesis?

shape forming of embryo controlled by cell behaviours (shape, size, position, number) interference with this process can result in birth defects

what is dysmorphogenesis

abnormal foetal development (outside the norm of form and function)

birth defect definition

structural, behavioural, functional, metabolic disorder present at birth can be caused by malformations and deformations

what is malformation

primary morphologic defects in a organ or body part (results from disturbed developmental events or process during formation of structure)

what is deformation

secondary morphological defects causes by prolonged mechanical force being applied eg clubfeet due to compression in amniotic cavity

what is disruption

morphological alterations of already formed structures due to destructive processes

Malformation syndrome - down syndrome cause and effects

missing chromosome flat face, small nose reduced muscle eye slants hyper flexibility

Malformation syndrome - alcohol foetal syndrome effects

small eye openings smooth philtrum thin upper lip brain damage

what is teratology?

the study of birth defects a teratogen causes a birth defect

what determines the capacity of a teratogen

genotype of conceptus & maternal genome Development stage at the time of exposure to teratogens dose and duration of exposure mechanism & actions of teratogen

what is pathogenesis

abnormal development that leads to dysmorphogenesis can involve cell death, decreased proliferation

what can abnormal development cause?

death, malformation, growth retardation, functional disorders

congenital malformations statistics

birth defects - 25% of infant deaths (leading cause) 3% infants have structural anomalies birth defect frequency's are non-discrimatory (similar levels globally) 40-45% of defect have unknown cause genetic factors account for 28% birth defects

what can minor anomalies help detect

major anomalies in infants as they are common in those that already show minors

Human Embryology Flashcards

(49 cards)