Embryo Implantation And Fetal Development 5.2.24 Flashcards

1
Q

What are the stages in the ovarian cycle?

A
  1. Follicular phase , pre-ovulation
  2. Ovulation
  3. Luteal phase
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2
Q

How long is the average Ovarian cycle?

A

28 days

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3
Q

What is involved in the first stage of the Endometrial cycle?
1. Proliferative Phase

A

oestrogen - growth of the endometrium and myometrium , secretion of the mucus alongside the vagina and uterus

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4
Q

What is involved in the 2nd stage of the Endometrial cycle?
2. Secretory Phase

A

Oestrogen - grows the endometrium
Progesterone - softens the connective tissues in preparation for implantation and promotes secretion of nutrients ( fat and glycogen)

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5
Q

What is involved in the 3rd stage of the Endometrial cycle ?
3. menstrual phase

A

Only occurs if no fertilisation occurs
- Corpus leuteum decreases
- progesterone and oestrogen support is lost
- Uterine prostaglandins —> Vasoconstriction —> Tissue death
- Blood and endometrial debris (menses) lost through Vagina

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6
Q

How long can sperm survive for?

A

It can survive for up to 5 days but is only viable for 48 hours

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7
Q

What hormone does the Hypothalamus release?

A

GnRH

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8
Q

What hormone does the Anterior pituitary release?

A

LH/FSH

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9
Q

Which 2 hormones do the Ovaries release?

A

Oestrogen/ progesterone

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10
Q

What does GnRH stand for?

A

Gonadotropin hormone releasing hormone

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11
Q

What does a Rise in FSH stimulate?

A

Stimulates Oocyte (egg) development and follicular growth

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12
Q

What causes LH to spike?

A

Ovulation

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13
Q

IS ovulation a positive or negative feedback?

A

Positive

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14
Q

Is after ovulation positive or negative feedback?

A

Negative feedback due to progesterone

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15
Q

What process is Sperm is driven by to reach the oviduct?

A

Chemotaxis

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16
Q

How long after ovulation does fertilisation occur?

A

24 hours

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17
Q

what membrane do sperm penetrate?

A

The Corona Radiata

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18
Q

What do the sperm bind to after penetration?

A

Receptors on the Zona pellucida

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19
Q

What does the binding of sperm onto the receptors on Zona pellucida cause?

A

It causes an enzyme to be released form the acrosome that digest the Zona pellucida.

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20
Q

What reaction is triggered when the sperm head penetrates the ovum?

A

Cortical reaction

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21
Q

What does a cortical reaction trigger?

A

Inactivation of ZP3 receptor as and prevents polyspermy

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22
Q

when does Fusion of Nuclei occur?

A

Occurs within an hour triggering embryonic development

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23
Q

What are the 4 Stages of Ovum development?

A

1 - Ovum
2 - Cleavage
3 - Morula
4 - Blastocyst

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24
Q

What are the Stages of implantation?

A
  1. Blastocyst surface becomes sticky and adheres to endometrium
  2. The trophoblastic cells release protein-digesting enzymes
  3. Cords of trophoblastic cells go deeper into the endometrium
  4. The embraces of trophoblastic cells disintegrate
  5. Underlining endometrium produces prostaglandins that increase vascularisation and nutrients
  6. The embryo is implanted into the endometrium
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25
Q

What is the endometrium called after its been modified by prostaglandins?

A

Decidua

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26
Q

What is an ectopic pregnancy?

A

When implantation occurs outside of the uterus. Most typically in one of the fallopian tubes.

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27
Q

What is the cause for molar pregnancy?

A

Abnormal fertilisation

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28
Q

What is a molar pregnancy?

A

It’s where the trophoblastic tissue over grows and shows as a mass of cysts.
when there is a problem with fertilisation so the embryo and placenta don’t form correctly.

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29
Q

What is a molar pregnancy also known as?

A

Hydatiform pregnancy

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30
Q

What is the placenta responsible for?

A

Delivery of oxygen and nutrients
Removal of wastes and CO2 from the fetus

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31
Q

When is the developed Placenta?
What happens with the embryo when the placenta embeds itself?

A

Day 12 - embryo is embedded in the decidua
The placenta is well developed by 5 weeks after implantation (6 weeks of gestation)
This is when the embryonic heart starts pumping blood into the placental villi.
Fetal part of placenta starts secretion of hCG and progesterone.

32
Q

Which Substances can cross the placenta barrier?

A
  • cocaine and heroine
  • Rubella virus
  • Cytomegalovirus virus
  • HIV
  • Toxoplasma
  • Treponema pallidum (syphilis)
33
Q

what substances are transported From mother to fetus?

A

+ O2
+ water , electrolytes
+ Nutrients - carbohydrates, amino acids and lipids
+ Hormones
+ antibodies
+ Vitamins
+Iron and trace elements
+ drugs
+ toxic substances
+ viruses

34
Q

what substances are transported From fetus to mother?

A
  • CO2
  • water, electrolytes
  • urea, Uris acid
  • Creatinine
  • bilirubin
  • Hormones
  • red blood cells antigens
35
Q

Which are the most common congenital abnormalities?

A

Heart
Neurotube defects
Down syndrome

36
Q

Environmental factors that can cause birth defects

A

= thalidomide
=Radiation
=Alcohol
= Drugs
= smoking
= poisons
= infections (eg: rubella, toxoplasma Gondi, herpes)

37
Q

What are some of the Genetic factors that can cause birth abnormalities?

A
  • Chromosomal abnormalities
    Eg: Down, turner, Patau syndromes
  • Mutant genes
    Eg: achondroplasia, primordial dwarfism, fragile X syndrome and split foot anomaly
38
Q

What are some Abnormalities that are visible at birth?

A

Spina bifid a
Cleft lip and palate
Gastroschisis/ exompholos
Anencephaly
Down syndrome
Under development of limbs

39
Q

What are some of the Abnormalities invisible at birth?

A

Cardiac defects : tetralogy of fallout
Atresias
Rare congenital disorders eg: pain receptors

40
Q

How many layers are there in the development of an embryo?
What are these layers?

A

3 - Ectoderm, mesoderm, endoderm

41
Q

What are the Contents of the Ectoderm?

A

Structures that maintain contact with the outside world
- CNS and pNS
- Sensory apparatus of eye, ear and nose
- epidermis, hair and nails
- subcutaneous, mammary, pituitary glands
- enamel of the teeth

42
Q

What are the Contents of the Mesoderm?

A

+ vertebral column
+ Dermatomes
+ Myotomes
+ urogenital structures
+ peritoneal, pleural and pericardial linings
+ Haemopoetic stem cells

43
Q

What are the Contents of the endoderm?

A

~ GI tract
~ Epithelial linings of the respiratory tract
~ urinary bladder and urethra
~ tympanic cavity and auditory tube
~ parenchyma of thyroid, parathyroid, liver and Pancreas

44
Q

What is the process of Neurulation?

A

The forming of the neural tubes during Fetal development

45
Q

What are some of the Factors that impact the development of neural tubes and can cause defects?

A
  • Anti-epileptic medication
  • Maternal diabetes
  • Hyperthermia
  • High glucose + insulin
  • Retinoic acid ( vitamin A metabolite)
46
Q

What medicine can protect against neural tube defects?

A
  • Folic acid supplementation can reduce the chance of defects by ~ 75% if started 2 months before conception
47
Q

What is Spina bifida?
What are the different types of Spina Bifida?

A

Neural tube fails to close along its length
It involves the meninges, vertebrae, muscles and skin - sometimes neural structures

The spinal cord and nerves may be :
- open to the outside world - Spina bifida aperta
- covered with skin - Spina bifida occulta
- covered with just the surrounding membranes - Spina bifida cystica - meningocele or myelomeningocele

48
Q

What type of Spina bifida is where the nerves are open?

A

Spina bifida aperta

49
Q

Which type of Spina bifida are the nerves covered by skin

A

Spina bifida occulta

50
Q

Which type of Spina bifida are the nerves covered with just the surrounding membranes ?

A

Spina bifida cystica, meningocele, mylomeningocele

51
Q

What are the common neuro associations of Spina bifida?

A

Arnold chiari malformations and Hydrocephalus

52
Q

How is Spina bifida detected and diagnosed?

A

Antenatal screening - elevated alpha fetoprotein levels
On ultrasound scan - routine scans 12 weeks and 20 weeks

53
Q

What is the medical term for the Forebrain?

A

prosencephalon

54
Q

What is the medical term for the Midbrain?

A

Mesencephalon

55
Q

What is the medical term for the Hind brain?

A

Rhombencephalon

56
Q

What gene controls Facial development?

A

Controlled by the HOX (homebox) gene

57
Q

What happens in the 7th week of facial development?

A

The medial nasal prominences fuse to form the inter-maxillary segment

58
Q

What is the resultant of the failure of fusion of the maxillary prominence and the inter-maxillary segment?

A

Cleft lip

59
Q

What happens during during the 14th week of facial development?

A

The inter-maxillary process forms the philtrum of the upper lip.

60
Q

What happens in the 10th week of facial development?

A

A fusion of the palatine shelves and primary palette to form the secondary palate.
Failure to fuse results in a cleft palate

61
Q

Cleft lip is most common in?

A

Males

62
Q

Cleft pallet is most common in ?

A

Females

63
Q

When does the heart begin to beat?

A

Day 22 - 24
It can be heard at 6 weeks on ultrasound

64
Q

When does blood start to flow?

A

Week 4

65
Q

What are Common heart abnormalities?

A
  • septal defect
  • Transposition of the great arteries
  • Persistent truncus arteriousus
  • hypo-plastic left heart
66
Q

At what stage does the embryo have Paddle- like upper limb buds?

A

Week 5 - 32 days

67
Q

At how many weeks are Handplates formed?

A

Week 5 - 35 days

68
Q

At how many weeks/days do Digital rays appear in hand plate ?

A

Week 6 - 44 days

69
Q

At how many weeks is there- bend at the elbow, fingers are short and slightly webbed

A

Week 7 - 48 days

70
Q

After how many weeks are the Fingers and toes are distinct and separated?

A

Week 8 - 56 days

71
Q

What is the Apical Ectodermal ridge (AER) responsible for?

A

One of the main signaling centres during limb development

72
Q

What does the AER determine?

A
  • pattern of the limb
  • Formation of early skeleton
  • Muscles, tendons and vasculature
73
Q

What are common Limb Development abnormalities?

A

~ Meromelia
~ Amelia
~ polydactyly
~ Triphalangeal thumb
~ Dysplasia’s
~ deformations due to amniotic bands

74
Q

What is Meromelia?

A

Reduction of part of the limb

75
Q

What is Amelia?

A

Missing limb

76
Q

What is Polydactyly?

A

Presence of extra digits

77
Q

What are Dysplasia’s?

A

Fusion of limb parts / disproportionate growth