Human Embryology Flashcards

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1
Q

Why is embryology studied?

A
  • history of prenatal origin
  • understand birth defects
  • to understand adult anatomy
  • understand adult illness’s and origins
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2
Q

What are the embryological periods?

A

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

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3
Q

What is the embryonic period? (organogenesis)

A

beginning of 4th week to end of 8th week

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4
Q

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

A

Ectoderm, Mesoderm, Endoderm

give rise to specific tissues and organs

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5
Q

what is the period of the foetus?

A

beginning of 3rd month to birth

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6
Q

What is gametogenesis?

A

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

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7
Q

What are male and female gametogenesis called?

A

male - spermatogenesis

female - oogenesis

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8
Q

What are the principal goals of gametogenesis?

A

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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9
Q

What do chromosomal abnormalities lead to?

A

birth defects, spontaneous abortions, fertility

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10
Q

What is fertilisation?

A

process of male and female gametes fuse to form a zygote

restores diploid number of chromosomes

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11
Q

what is capacitation?

A

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

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12
Q

what is acrosome reaction?

A

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

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13
Q

what is the cortical reaction?

A

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

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14
Q

what is the zona reaction?

A

structure and composition of the zona pellucida is altered preventing polyspermy

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15
Q

what causes male infertility?

how can it be treated?

A

quality and quantity of spermatozoa

assisted reproductive technology (ART)

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16
Q

what causes female infertility?

A

multiple physiological and anatomical factors

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17
Q

what is and when does cleavage happen

A

within week of fertilisation

rapid repeated mitotic cell division of zygote to produce blastomeres

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18
Q

what is the purpose of cleavage?

A

form multicellular embryo (morula) from the single large zygote

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19
Q

what is the process of compaction

A

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

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20
Q

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

A

the fully developed morula wi/ fluid filled cavity

21
Q

what is the bilaminar embryonic germ disc?

A

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

22
Q

Stem cell definition

A

undifferentiated cell that can form specialised cell types

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

23
Q

Pluripotent cell definition

A

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

24
Q

Multipotent cell definition

A

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

25
Q

Totipotent cell definition

A

can form all differentiated cells types in body

26
Q

what is the primitive streak?

A

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

27
Q

what is gastulation?

A

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

28
Q

what is the principle goal of gastrulation

A

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

29
Q

clinical implications of errors of gastrulation

A

caudal dyslasia (caudal regression syndrome), caudal or sacral agenesis

dextrocardia (right side heart)

heart/septal defects

atrial/ventricular isomerism’s/inversions

30
Q

what does the ectodermal germ layer give rise to?

A

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

31
Q

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

A

cranial connective tissue

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

32
Q

what are the 3 parts of the mesodermal germ layer?

A

paraxial mesoderm

intermediate mesoderm

lateral plate mesoderm

33
Q

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

A

urogenital system - primordial germ cells, gametes, gonads

34
Q

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

A

splits in 2 - parietal = cavity walls
visceral - wall of gut tube

dermis of skin, limbs, bones, connective tissue, muscle

35
Q

what does the endodermal germ layer give rise to?

A

epithelial lining of GI tract

36
Q

what is morphogenesis?

A

shape forming of embryo controlled by cell behaviours (shape, size, position, number)

interference with this process can result in birth defects

37
Q

what is dysmorphogenesis

A

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

38
Q

birth defect definition

A

structural, behavioural, functional, metabolic disorder present at birth

can be caused by malformations and deformations

39
Q

what is malformation

A

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

40
Q

what is deformation

A

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

41
Q

what is disruption

A

morphological alterations of already formed structures due to destructive processes

42
Q

Malformation syndrome - down syndrome cause and effects

A

missing chromosome

flat face, small nose
reduced muscle
eye slants
hyper flexibility

43
Q

Malformation syndrome - alcohol foetal syndrome effects

A

small eye openings
smooth philtrum
thin upper lip
brain damage

44
Q

what is teratology?

A

the study of birth defects

a teratogen causes a birth defect

45
Q

what determines the capacity of a teratogen

A

genotype of conceptus & maternal genome

Development stage at the time of exposure to teratogens

dose and duration of exposure

mechanism & actions of teratogen

46
Q

what is pathogenesis

A

abnormal development that leads to dysmorphogenesis

can involve cell death, decreased proliferation

47
Q

what can abnormal development cause?

A

death, malformation, growth retardation, functional disorders

48
Q

congenital malformations statistics

A

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

49
Q

what can minor anomalies help detect

A

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