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Scientific Basis of Midwifery > Embryology > Flashcards

Embryology Flashcards

1
Q

How long does the embryonic period last?

A

3-8 weeks

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2
Q

Define proliferation

A

The rapid growth and production of cells

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3
Q

Define differentiation

A

The process of developing and changing to become specialised

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4
Q

Define specialisation

A

The adaptation of a cell to carry out a particular function

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5
Q

Define apoptosis

A

Cell death as a normal and controlled process of cell growth and development

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6
Q

Define morphogenesis

A

The biological process that causes a cell to develop its shape

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7
Q

Name 2 conditions that arise from ineffective proliferation/ apoptosis

A

Excessive proliferation = Polydactyly

Failed apoptosis = Syndactyly

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8
Q

Describe the process of fertilisation

A

Sperm cell –> Corona radiata of egg –> Acrosome releases enzymes –> Sperm cell penetrates zona pellucida –> Sperm cell’s membrane fuses with egg cell’s membrane

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9
Q

Outline what occurs just after fertilisation takes place

A
  • Oocyte completes meiosis II
  • Cumulus oophorus cells surround the oocyte
  • Theca cells form the corpus luteum
  • Corpus luteum secretes progesterone which prepares and sustains the uterine wall for implantation
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10
Q

Describe the fertilised ovum

A
  • 12-24 hours after fertilisation
  • Sperm must get through corona radiate and zona pellucida
  • Zona becomes specialised once a sperm has traversed it, blocking others from entering
  • Oocyte completes meiosis II and 2 pronuclei form
  • Male and female pronuclei fuse to form zygote (2n)
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11
Q

What are the stages of embryonic development?

A
  1. Fertilised ovum
  2. Cleavage (30 hrs - day 3, mitosis increases cell number)
  3. Morula (day 3-4, solid ball of cells)
  4. Blastocyst (day 5, trophoblast, blastocoel and inner cell mass form)
  5. Implantation (blastocystic stage, day 7-8, syncytiotrophoblast secretes enzymes that allow implantation)
  6. Gastrulation (end of week 2, primary germ layers form)
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12
Q

What is a blastocoel?

A

Cavity in blastocyst

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13
Q

When are the discs formed?

A

Week 2 = Bilaminar disc

Week 3 = Trilaminar disc

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14
Q

How does the bilaminar disc form?

A

Differentiation of the embryoblast (inner cell mass)

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15
Q

What are the 2 parts of the bilaminar disc?

A

Epiblast

Hypoblast

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16
Q

Describe the formation of the epiblast

A
  • Cells cavitate to form the amnion
  • Cells from the epiblast will also eventually form the body of the embryo
  • Located above amniotic cavity
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17
Q

Describe the formation of the hypoblast

A
  • Future cranial region
  • Cells of hypoblast migrate along inner surface of cytotrophoblast and form primary yolk sac
  • Primary yolk sac reduces in size and becomes secondary yolk sac
  • Transfers nutrients between foetus and mother
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18
Q

What is the yolk sac?

A

Origin of blood cells and vessels

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19
Q

What are the 2 types of trophoblast?

A
  1. Cytotrophoblast

2. Syncytiotrophoblast

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20
Q

Describe the cytotrophoblast

A
  • Inner
  • Divides mitotically into syncytiotrophoblast to form primary chorionic villi
  • Cells from these villi can be removed for chorionic villus sampling
  • Have membranes
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21
Q

Describe the syncytiotrophoblast

A
  • Outer
  • Acellular (no membranes or mitosis)
  • Produces hCG
  • Invades endometrium
  • As it comes in contact with blood vessels, it forms lacunae which fuse to form lacunar networks
  • Blood flows in and out of these networks, exchanging nutrients and waste products with the foetus
22
Q

What are lacunae?

A

Spaces filled with maternal blood

23
Q

What is gastrulation?

A

A phase in the early stages of embryonic development in which the single-layered blastula becomes a multi-layered gastrula

24
Q

What is a primitive streak?

A
  • Raised groove on dorsal surface

- Region of cell migration from the epiblast layer, forming 2 germ cell layers (endoderm and mesoderm)

25
What causes the formation of the trilaminar disc?
Cell migration
26
What are the 2 cavities in the gastrula?
1. Yolk sac | 2. Amniotic cavity
27
What is the notochord?
- A flexible rod similar to cartilage | - Defining structure in all chordate embryos
28
Describe neurulation
- Neural tube (beginning of CNS) and neural crest (beginning of PNS) development - Neural tube closure which begins at week 3 and ends in week 4 - Folic acid can be used as 'therapy' to prevent occurrence of neural tube defects
29
Name 3 other developments that occur during gastrulation
- Primordial mouth and anus - Primordial cardiovascular system - Secondary and tertiary chorionic villi
30
What are the 3 layers of the trilaminar disc?
1. Ectoderm 2. Mesoderm 3. Endoderm
31
What structures are derived from the ectoderm?
- Epidermis; hair and nail follicles; sweat glands - NS; pituitary gland; adrenal medulla - Lens + cornea; internal ear - Mucosa of oral + nasal cavities; salivary glands
32
What structures are derived from the mesoderm?
- Dermis; bone and cartilage - Skeletal, cardiac and smooth muscle - Kidneys + adrenal cortex - Bone marrow + blood; lymphatic tissue; lining of blood vessels
33
What structures are derived from the endoderm?
- Mucosa of oesophagus, stomach and intestines - Epithelium of respiratory tract, including lungs - Liver and mucosa of gall bladder - Thyroid gland; pancreas
34
In which week does organogenesis occur?
4
35
Describe organogenesis
- Embryonic folding - Cranio-caudal regions are formed - Neural tube fusing - Primitive ear present - Upper limb buds appear - Beating heart prominent - All organ systems recognisable by week 8
36
What is embryonic folding?
Trilaminar disc folds into cylindrical shaped embryo
37
What do the words 'cranio' and 'caudal' represent?
``` Cranio = head Caudal = tail ```
38
Describe the continued development of the embryo
Wk 5 - heartbeat can be seen and heard and brain, lens, nasal pit and upper limbs form Wk 6 - differentiation of limbs and ears Wk 7 - development of limbs Wk 8 - digits form, tail disappears, human characteristics develop Wk 12 - placenta becomes functional
39
Outline what occurs in the embryonic period
- Organs develop from the 3 primary germ tissues - Basic body plan emerges - Embryo grows from 3.5mm to 30mm
40
What are teratogens?
- Factors that cause congenital malformations during embryonic development - Structures in the developing embryo are sensitive to teratogens at different times
41
When do most abnormalities in embryonic development occur?
Major morphological abnormalities = week 3-8 | Functional defects and minor morphological abnormalities = week 8-40
42
What are 5 factors that affect embryonic development?
1. Genetic factors (15%) 2. Mutant genes 3. Environmental agents (10%) 4. Multifactorial causes (25% 5. Unknown causes (>50%)
43
Describe the embryonic membranes
- Amnion surrounds the embryo | - Umbilical cord formed from structures of connecting stalk
44
What does the placental membrane consist of?
- Epithelial wall of an embryonic capillary | - Epithelial wall of a chorionic villus
45
What are the 2 portions of the placenta called?
Chorion (maternal portion) | Amnion (embryonic portion)
46
Why are pregnant women advised to take folic acid?
- Supports healthy development of foetal brain and spinal cord - Helps prevent neural tube defects
47
Give 2 common neural tube defects
1. Spina bifida | 2. Anencephaly
48
What is the recommended daily dose of folic acid?
400mcg OR 5mg (high-risk women)
49
Give 4 factors that increase the risk of neural tube defects
1. Either the mother or her partner have spina bifida or have had a previously affect pregnancy 2. Mother has diabetes 3. Mother takes anti-epilepsy medication 4. Mother has coeliac disease
50
Give 4 ways of taking in folate
1. Folic acid supplements 2. Vegetables (asparagus, spinach, broccoli) 3. Fruits (oranges, bananas, strawberries) 4. Legumes (chickpeas, dried beans, lentils)

Scientific Basis of Midwifery (22 decks)

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