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ANA > Lecture 29 - Prenatal Development > Flashcards

Lecture 29 - Prenatal Development Flashcards

1
Q

Define -Embrynology

A

Embryology: the study of developmental events during the prenatal period

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2
Q

When is the prenatal period?

A

Prenatal period = conception -> delivery

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3
Q

What are the 3 stages of prenatal development?
Overview

A

1) Pre-embryonic development
- fertilization to 2 weeks
- ends after implantation
- cleavage
- “pre-embryo”

2) Embryonic development
- week 3-8
- organogenesis
- “embryo”

3) Fetal development
- week 9 - delivery
- “fetus”

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4
Q

After 1 week egg =

A

pre embryo

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5
Q

after 4 weeks egg =

A

embryo

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6
Q

after 9 weeks egg =

A

fetus

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7
Q

Define - Fertilization

A

Fertilization: sperm fusing with egg to produce a zygote

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8
Q

What is the first cell of a new indiv called?

A

zygote = first cell of a new indiv

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9
Q

How long does fertilization take?

A

Takes 30 minutes - 2 hours from penis to ampulla
then the sperm has to hang out for 6-8 hours waiting for capacitation to occur

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10
Q

Define - Capacitation

A

Capacitation: transition of sperm cap from tough membrane to weak and fragile membrane bc secretions of enzymes from the female genital tract
- only capacitated sperm are fertile

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11
Q

only ____ sperm are fertile

A

only capacitated sperm are fertile

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12
Q

What are the layers of cells surrounding the egg that must be penetrated by the sperm

A

1) corona radiata = cells surrounding the secondary oocyte
2) Zona pellucida = glycoproteins

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13
Q

What happens after capacitation

A

after capacitation acrosomal reactions occur

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14
Q

Define - Acrosomal reaction

A

Acrosomal reaction : dozens of sperm rupture releasing enzymes from their head

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15
Q

What is the function of the enzymes released from the acrosomal reaction?

A

Enzymes from the acrosomal reaction breakdown the material that holds together the cells of the corona radiate then digest a hole thru the zona pellucida

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16
Q

What is the end result of the acrosomal reaction

A

As a result of the acrosomal reaction the surface of the egg is exposed to 1 sperm which will make contact with the egg

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17
Q

What triggers the egg to be “activated” and what does that mean?

A

The process of membrane fusion triggers the egg to become “activated”
Activation causes changes to the egg membrane which prevent fertilization by another sperm

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18
Q

Where in the egg do the sperm wait while it unpacks its chromosomes

A

the sperm waits in the peripheral cytoplasm of the egg while it unpacks its chromosomes

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19
Q

Describe the end part of fertilization when the chromosomes meet

A

1) The egg nucleus and sperm nucleus swell and form a female and male pronuclei which will start to approach each other while the mitotic spindle forms btwn them
2) Then the pronuclei membrane ruptures releasing the chromosomes into the vicinity of the spindles
3) The moment of fertilization occurs when the maternal chromosomes combine to form a diploid zygote with 46 chromosomes

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20
Q

Define - clevage

A

Cleavage: period of cell division of the zygote
- division of the zygote into blastomeres

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21
Q

What is a pre-embryo

A

2 identical blastomeres

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22
Q

How long after fertilization does the first cleavage occur

A

30 hours after fertilization the first cleavage occurs producing 2 identical blastomeres = pre-embryos

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23
Q

What is the thing called 72 hours after cleavage
how many cells
when/where

A

72 hours = morula
16 cells
The morula reaches the uterus on the 4th day after fertilization. goes into lumen of uterus

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24
Q

A fluid penetrates the zona pellucida what/from where

A

A fluid penetrates the zona pellucida which rearranges the blastomere around a fluid filled central cavity
Fluid = uterine milk,
- secreted by glands of the endometrium

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25
Q

What is the result of the fluid penetrating the zona pellucida

A

Bc the milk penetrates the zona pellucida, it causes the layers of glycoprotein to breakdown and then the ball of cells inside can escape = Blastocyst

26
Q

Blastocyst
When:
Where:
What:

A

Blastocyst
When: 5 days after fertilization
What: fluid filled hollow space composed of trophoblasts and embryoblasts
- is ready for implantation

27
Q

Blastocytes are composed of trophoblasts and embryoblasts … what do they become

A

Trophoblasts -> form placenta
Embryoblast -> embryo

28
Q

What ends pre-embryonic development?

A

implantation

29
Q

Define - Blastocoele

A

Blastocoele = cavity inside blastocyst

30
Q

When does implantation occur>

A

Implantation = 6 days after fertilization

31
Q

Describe the steps of implantation

A

1) Trophoblast adheres to and embeds into the endometrium
2) The trophoblast cells release human gonadotropin which is the basis of a pregnancy test
3) Trophoblast divides into:
- cellular trophoblast (inner layer)
- synctiotrphoblast (outer layer)
4) Has lost membrane so can burry into the uterine walls until the blastocyst is fully barried
5) Takes 1 wee, completed 14 days after fertilization

32
Q

Which hormone is used for pregnancy test

A

Human gonadotropin

33
Q

What does the trophoblast divide into during implantatino

A
  • cellular trophoblast = inner layer
  • syncytiotrophoblast = outer layer
34
Q

How long does implantation take

A

1 week

35
Q
A
35
Q
A
35
Q

9 days after fertilization … is implantation complete?

A

No, implantation starts 6 days after fertilization and takes 1 week to complete

36
Q

What happens 8 days after fertilization?

A
  • The embryo divides into a 2 layer bilaminar disc composed of hypoblasts and epiblasts
37
Q

What are the cell layers of the bilaminar disc called

A

hypoblasts and epiblasts

38
Q

Btwn what cells layers is the amniotic cavity

A

The amniotic cavity is btwn the hypoblast and the epiblast

39
Q

Define - Dizygotic fraternal twins

A

Fraternal Twins = 2 oocytes each fertilized by a diff sperm

40
Q

Define - Monozygotic twins

A

Monozygotic = identical

41
Q

When is is common for twins to form>?

A

2 Cell Stage
- zygote divides giving rise to 2 indiv blastocytes
- each get own amniotic cavity

Level of Inner Cell Mass - Blastocyst stage
- Most common
- common placenta, diff amniotic cavity

Level of bilaminar disc
- each form an embryo
- share amniotic cavity

42
Q

When do twins share amneiotic cavity

A

when spit at level of the bilaminar disc

43
Q

when does the bilaminar disc become a trilaminar disc

A

week 3

44
Q

When does gastrulation occur

A

15 days after fertilization

45
Q

Define - Gastrulation

A

Gastrulation: the process where the bilaminar embryonic disc, consisting of the epiblast and hypoblast is transformed into a trilaminar embryonic disc consisting of 3 layers:
- ectoderm
- mesoderm
- endoderm
Begins the formation of the primitive streak

46
Q

What are the 3 layers of the trilaminar embryonic disc formed from primitive streak?

A
  • ectoderm
  • mesoderm
  • endoderm
47
Q

Define - Primitive streak

A

Primitive streak = narrow midline groove on the surface of the epiblast

48
Q

What happens immediately following the formation of the primitive streak

A

As soo as the streak forms:
- some epiblast cells on either side of the streak migrate to the middle where they invaginate into the primitive streak and slide down the epiblast layer displacing the original hypoblast forming a mesoblast

49
Q

What happens on day 16-18

A

Day 16-18
- cells combine and form the notochord which is the basis of the axial skeleton

50
Q

Define - notochord

A

Notochord: axis around which the vertebral column forms

51
Q

What happens in week 3-8

A

embryonic folding

52
Q

What causes malformations in babies

A

tetragens

53
Q

What are the derivatives of the ectoderm germ layer (9)

A

= forms structures that maintain contact with the external environment
- NS
- Epithelium of ear, nose, eye
- epidermis of skin
- epidermal derivatives (hair, nails, sweat glands, mammary glands)
- enamel of teeth
- pituitary gland
- lens of eye
- adrenal medulla

54
Q

What are the derivatives of the mesoderm? (9)

A

-> forms supporting tissues
- ct including cartilage and bone
- muscle (striated and smooth)
- subcutaneous tissue of skin
- blood and bv
- kidney and ureters
- gonads and their ducts
- spleen
- adrenal cortex
- heart
-> medial mesoderm segments into somites which give rise to:
- skull
- vertebral column
- skeletal muscle
- dermis of skin

55
Q

What are the derivatives of the endodermal germ layer?

A

-> Forms the epithelial lining of:
- GI tract
- Respiratory tract
- Bladder
- Middle Ear
-> Forms parenchyma of:
- liver
- pancreas
- thyroid
- parathyroid
- thymus
- tonsils

56
Q

When is the fetal period?

A

Week 9 - birth

57
Q

By which week are all adult organs formed?

A

By week 13 all adult organs are in place

58
Q

What does the fetus grow to during the fetal period?

A

Grows form 22 mm -> 360 mm
1 g -> 2.7-4.4 kg
22 inches at birth

ANA (7 decks)

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