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Histology Final > Embryology > Flashcards

Embryology Flashcards

1
Q

Three phases of human prenatal development

A
  1. Pre-embryonic period –> gametogenesis and fertilization
  2. Embryonic period –> blastogenesis (1-2) and embryogenesis (3 to 8)
  3. Fetal period –> fetogenesis (9th week to birth)
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2
Q

Sheaths of oocyte

A

Plasma membrane with microvilli
Zona Pellucida
Corona Radiata

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3
Q

Zona peullucida

A
  • secreted by follicular cells and oocyte
  • composed of glycoprotein, ZP3 is sperm receptor
  • for fertilization and implantation
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4
Q

Corona radiata

A
  • follicular cells

- protection, Nutrition and growth Regulation

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5
Q

Sperm parts

A

Head: haploid nucleus, covered by acrosome

neck: contains pair of centrioles (9x3 centrioles)

tail:

  • middle piece: axoneme in Center (central pair and 9 doublets of microtubules), 9 outer dense fibers, sheath of mitochondria
  • principal piece: axoneme and 9 outer fibers, fibrous sheath
  • end piece: axoneme, no outer fibers
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6
Q

Fertilization phases

A

Phase I:
Penetration of CR, binding to ZP3

Acrosome reaction:
Plasma membrane of sperm and acrosome fuse

Phase II.
Penetration of ZP

Phase III:
Fusion of oocyte and sperm Plasma membranes

Cortical reaction
Release of cortical granules with Enzymes of oocyte

Zona reaction
Alteration of ZP3, prevents ither sperm binding
Male and female pronuclei form, pronuclei fuse and form zygote

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7
Q

Results of Fertilization

A 
Finishing the secnid meioitc division of oocyte
Diploid number of chromosomes
Determination of sex
Variation of human
Initiation of cleavage
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8
Q

Cleavage or segmentation

A
  • part of blastogenesis
  • series of mitotic divisions
  • cells are blastomeres

Purpose: to generate a mutlicellular embryo

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9
Q

Migration inside uterine tube

A
  • emrbyo is carried passivly by cilia and contraction if tube
  • Nutrition: yolk and secretions of tube
  • on 3rd day: 16 cell Morula
  • two types of blastomeres: inner and outer cell mass
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10
Q

Entering the uterine cavity

A
  • blastocyst Formation: on 4th day
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11
Q

Parts of Blastocyst

A

1- Trophoblast: flattened outer cell, develops into Chorion and placenta
2- Embryoblast: inner cell mass at one pole, develops into Embryo, Amnion and yolk sac
3- Blastocyst cavity

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12
Q

Blastocyst inside uterus

A

Migration until 6th day

covered in Zona pellucida

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13
Q

Implantation stages

A

site: Fundus or corpus of Uterus

  1. Hatching from blastocyst from the zona pellucida
  2. Attachment of blastocyst to uterine Endometrium
  3. Penetration of blastocyst into Endometrium
    –> trophoblast differentiates into:
    >cytotrophoblasts (inner)
    >syncytiotrophoblast (outer)
  4. Embedding of the blastocyst in endometirum and Proliferation of trophoblast
    >lacunae appear in STB and maternal blood enters

Penetration is stopped in compact layers

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14
Q

Functions of the STB

A
  • produces Enzymes that erode Endometrium
  • resolves the destroyed products
  • produes Hormones hCG
  • will later form placental barrier
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15
Q

Decidual reaction of endometrium

A
  • Response to Implantation

- Endometrium becomes more succulant and edematous

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16
Q

Decidual cells

A
  • large with Lipids and glycogens

- Nutrition of Embryo, Regulation of development of Embryo, protection of agressive penetration

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17
Q

During Implantation, embryoblast differentiates into two layers

A
  • Epiblast layer
  • Hypoblast layer

–> Bilaminar germ Disc

two extraembryonic cavities: Amnion, Yolk sac

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18
Q

Amnion formation

A
  • small Cavity within epiblast -> primitive Amnion

- 11-12th days: primitive Amnion covered by extraembryonic Mesoderm –> definite mesoderm

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19
Q

yolk sac formation

A
  • flat cells of Hypoblast cover Surface of CTB –> primitive yolk sac
  • covered by extraembryonic Mesoderm –> definitive yolk sac
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20
Q

Extraembryonic mesoderm

A
  • 12th day: cells derive from primitive yolk sac
  • extraembryonic cavity: cavity within the extraembryonic Mesoderm
  • lines the trophoblast: froms Chorion
  • Embryo remains connected to trophoblast by connecting stalk (forms umbilical cord)
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21
Q

Gastrulation

A
  • start of Embryogensis in 3rd week
  • process during which the bilaminar germ Disc develops into a 3 laminar germ Disc
  1. Ectoderm
  2. Mesoderm
  3. Endoderm
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22
Q

beginning of 3rd week

A

Epiblast is source of all germ layers

Primitive streak: at caudal midline of epiblast, contains primitive groove

Cranial end of primitive streak: primitive node with primitive pit

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23
Q

Invagination/ ingression

A
  • Migration of epiblast cells towards the primitive streak
  • enterinf through primitive streak
  • detaching from epiblast
  • migrating beneath it
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24
Q

Formation of Endoderm

A
  • some invaginated cells invade and displace the hypoblast
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25
Q

Formation of Mesoderm

A
  • invaginated cells between epibalst and newly created endoderm
  • cells invaginated in primitive node: definitive notochord
  • cells invaginated in primitive streak: paraxial Mesoderm, intermediate Mesoderm, lateral Mesoderm, cardiogenic mesiderm
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26
Q

Trilaminar germ Disc contains of three layers, except:

A
  1. Oropharyngeal membrane

2. Cloacal membrane

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27
Q

Derivatives of ectoderm

A

Neurulation (3-4 weeks) induced by notochord

  1. Surface ectoderm
  2. Neuroectoderm (neural tube, neural crest)
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28
Q

Neurulation

A

neural plate –> neural groove –> neural fold –> neural tube and neural crest

  • Fusion Begins in cervical regionand proceeds in borth directions
  • cranial and caudal Ends are open until Fusion is complete (anterior and posterior neuropores)
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29
Q

Derivatives of neural tube

A

CNS
Retina
Neurohpophysis
Epiphysis

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30
Q

Dervatives of neural crest

A

PNS
Melanocytes
Adrenal medula
Mesenchyme of head

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31
Q

Derivatives of Surface ectoderm

A
  • dermal Epithelium
  • hair, nail, Skin Glands
  • ectodermal thickenings or placodes in head –> sensory epithelium
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32
Q

Derivatives of mesoderm

A
  • axial Mesoderm (notochord)
  • Paraxial Mesoderm (somites)
  • Intermediate Mesoderm (nephrotomes)
  • Lateral plate Mesoderm (2 layers - parietal and visceral)
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33
Q

Notochord

A

Axis of germ Disc
Inductor of neurulation adn somitogenesis
Contributes to nucleus pulposus and vertebral disc

34
Q

Paraxial mesoderm

A
  • middle of 3rd week: divides into Segments –> SOMITOMERES
  • Formation Begins in cephalic Region
  • 7 pairs of SMM in the head –> Mesenchyme of head
  • from occipital Region caudally: somites (3 pairs a day)
35
Q

Derivatives of the somite

A

Sclerotome: mesenchymal cells surround notochrod and neural tube –> vertebral column

Myotome: mesenchymal cells form skeletal muscles

Dermatome: mesenchymal cells form the dermis of back

36
Q

Intermediate Mesoderm and its drivatives

A
  • connects paraxial and lateral plate Mesoderm

- consists of segmented nephrotomes (form urinary System and Glands)

37
Q

Lateral plate Mesoderm and its derivatives

A
  1. Parietal layer: forms dermis of bidy, Skeleton of limbs

2. Visceral layer: forms CT and muscles of internal organs

38
Q

Primordial heart

A
  • cardiogenic Region is anterior to buccopharyngeal membrane

- 21 to 22 day: heart tube Begins to beat

39
Q

Coleom

A
  • between parietal and visceral layers of lateral plate Mesoderm
  • transforms into serous cavities
40
Q

Derivatives of endoderm

A
  • gut tube –> forms during Embryo folding
41
Q

Embryo folding

A
  • 4th week
  • Head and tail fold –> cephalocaudal folding
  • lateral Body wall folds –> lateral folding
    Embryo separates from yolk sac
    Gut tube forms
42
Q

Gut tube

A

Ends are boundedn by buccopharygeal and cloacal membranes

foregut
midgut
hindgut

43
Q

Derivatives form gut tube

A

Epithelium of digestive System
Epithelium of respiratory sytstem
Epithelium of liver, pancreas
Epithelium of urinary bladder

44
Q

Features of the external Body by the end of 8th week

A 
human appearance
shape of face and extremities
tail has disappeared
bended Body Begins to traighten
head takes half of Body length
33 mm
45
Q

Fetal membranes and adnexa

A
  • Chorion
  • Amnion
  • Allantois
  • umbilical cord
  • decidua
  • placenta
46
Q

Chorion

A

extraembryonic Mesoderm lines CTB of trophoblast –> Chorion forms

Wall: trophoblast and extraembryonic mesoderm

47
Q

Chorionic villi

A

emerge from Chorion and invade Endometrium

Primary (11 to 13th day): CTB core, covereby by STB layer

Secondary (13 to 15th): extraembryonic Mesoderm penetrates core of Primary villi

Tertiary (18th to 22nd): blood vessel in extraembryonic mesodermal core

in embryonic period:
- villi cover entire Surface of Chorion
in fetal period:
- only on embryonic pole –> Chorion frondosum

48
Q

Amnion

A
  • sac that contains Embryo and amniotic fluid
  • inner lining of amniotic cells
  • outer layer of extraembryonic Mesoderm
49
Q

Amniotic fluid

A

fluid is derived from:

  • maternal blood
  • fetal blood
  • produced by amniotic cells and fetal respiratory epithelium
50
Q

Amniotic fluid recirculation

A

4th to 5th month: Fetus swallows it

  • -> blood circulation
  • -> placenta or urine
51
Q

Vernic caseosa

A
  • fatty substance that covers the fetal Skin
  • from 5th to 6th month
  • protects Skin from maceration
52
Q

Lanugo hair

A
  • anchor to hold vernix caseosa to the Skin
  • before birth: replaced by vellus hair
  • fetur consumes Lanugo hair together with amniotic fluid
53
Q

Meconium

A
  • earliest stool of an Infant

- consists of: intestinal epithelial cells, Lanugo hair, water, bile

54
Q

Function of amnion

A
  • absorbs jolts
  • allows fetal movement
  • insures bod temperature, symmetrical growth and normal development of the fetal lungs
55
Q

Yolk sac

A
  • inner layer: extraembryonic endoderm
  • outer layer: extraembryonic Mesoderm

end of 3rd month: yolk sac shrinks but stays connected by vitalline duct

56
Q

Functions of the yolk sac

A
  • hematopoietic stem cells areise in vitelline vessels (3rd to 4th week)
  • Primoirdial germ cells in 3rd to 4th week
57
Q

Vitelline duct

A
  • Yolk stalk

- later becomes vitelline ligament between Ileum and umbilicus of fetus

58
Q

Allantois

A
  • diverticulum of yolk sac
  • 3rd week
  • rudimentary
  • becomes fibrous cord, (urachus) during mebryo folding
  • becomes median umbilical ligament after birth
59
Q

Formation of the umbilical cord

A

Amnion envelops connecting stalk and yolk stalk –> primitive umbilical cord

60
Q

Physiological umbilical hernia

A

6th to 7th week: abdominal cavity is too small for intesines –> some of them are in umbilical cord

11th week: intestines returs into body

61
Q

Decidua

A

Functional layer of the Endometrium

  • decidua basalis: at site of Implantation, over Chorion frondosum
  • decidua capsularis: decidual layer of implanted Embryo
  • decidua parietalis: at opposite site of Uterus

3rd month: decidua capuslaris fuses with decidua parietalis

62
Q

Placenta

A
  1. maternal Portion
    - decidua basalis
    - decidual Septa
  2. fetal Portion
    - chorionic plate
    - chorionic villi
63
Q

Lacunae

A
  • filled with maternal blood

- separated by decidual septa

64
Q

Maternal blood circulation

A
  • spiral arteries open into Lacuna
  • oxygenated blood bathes the villi
  • blood flows back by endometrial veins
65
Q

Chorionic plate

A
  • covered by Amnion
66
Q

Cotyledon

A
  • structural and functional unit of placenta
  • composed of stem villi in Lacuna
  • 15 to 30 in one placenta
67
Q

Placental membrane until 4th month

A

STB
CTB on b.m.
Connective tissue in villus core
Wall of fetal vessel

68
Q

Placental membrane after 4th month

A

Fetal vessel come in contact with STB

All CTB was used to make STB

69
Q

Functions of the placenta

A
  1. Exchange of metabolic products
  2. Exchange of gaseous products
  3. Protection from bateria, maternal Hormones..
  4. Hormone production
  5. Depot of the Vitamins, glycogen, Fe
  6. Immunological barrier
70
Q

5 types of birth defects

A 
structural
behavioral
functional
metabolic disorfer
present at birth
71
Q

Teratology

A

science that studies the causes, mechanisms and Patterns of abnormal development

72
Q

Types of abnormalities during different prenatal periods

A

Gametopathies
Blastopathies
Embryopathies
Fetopathies

73
Q

Types of abnormalities according to different mechanisms

A
  • malformations (abnormal organogenesis)
  • disruption (morphological alterations of already formed structures)
  • Deformation (mechanical Forces press in Fetus)
  • Chromosomic disorders
74
Q

Causes of birth defects

A
  • unknown (40-45%)
  • genetic factors (28%)
  • Multifactorial (20-25%)
  • Environmental (3-4%)
  • Twinning (1%)
75
Q

Genetic factors to abnormalities

A

numerical or structural abnormalities of chromosomes

76
Q

Non-Disjunction

A
  • failure of homologous chromosomes to separate in meiosis I
    or
  • failrue of sister Chromatids to separate during meiosis II or mitosis
  • -> death of gametes
  • –> death of Embryo ir Fetus
  • -> Trisomies or monosomies
77
Q

Environmental factors /teratogens

A

Teratogens are able of Crossing placental membrane and causing a brith defect

infectious agents
Pharmaceutical drugs and chemical agents
Maternal nutritional deficiencies
heavy metals
radiation
78
Q

Principle of teratology

A

1- Susceptibility depends on genotype of Embryo
2- Susceptibility depends on stage
3- Dose and Duration of exposure
3- Mechanism of exposure
5. manifestations are detah, malformation, growth retardaton anf functional disorders

79
Q

Dizygotic twinning

A
  • 90%
  • two oocytes are fertilized by different spermatozoa
  • two blastocysts implant individually
80
Q

Monozygotic twinning

A

a single fertilized Ovum and result of Splitting of Zygote and Embryo at various stages

early spitting: individual Implantation –> dizygotic Twins

Twins with the same Chorion and Amnion (monochorionic and monoamniotic) –> Separation in bilaminar germ Disc stage –> MoMo twins

Histology Final (18 decks)

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