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BL Sem 1 > Lecture 3 & 4- Embryology > Flashcards

Lecture 3 & 4- Embryology Flashcards

1
Q

From which embryonic tissue are the three germ layers derived from?

A

Epiblast

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2
Q

What is the function of the hypoblast layer?

A

It lines the blastocyst cavity forming the yolk sac

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3
Q

Initial development of which system in the body is driven directly by the notochord?

A

CNS

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4
Q

Which tissue lines the intraembryonic coelom?

A

Mesoderm

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5
Q

What is the function of the notochord?

A
  • Drives neurulation (formation of spinal cord, CNS)
  • Is a hollow cord (becomes solid rod)
  • Forms nucleus pulposus of intervertebral disc
  • Has no function in adult life
  • Acts as midline
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6
Q

What is a derivative for the splanchnic layer of the lateral plate mesoderm?

A
  • Cardiac muscle

- Blood vessels

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7
Q

What is the difference between pluripotent and totipotent?

A
  • Zygote is totipotent: Has the ability to differentiate into any type of cell.
  • Pluripotent: Diff. into many but not all cell types (forms anything from the trilaminar disc)
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8
Q

Why does the buccopharyngeal membrane and the cloacal membrane have no mesoderm?
(mesoderm gives rise to all tissues of the CVS)

A
  • Opening for mouth & anus
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9
Q

What can umbilical cord stem cells be used for?

A
  • Multipotent (more specialised than pluri)
  • Form haematopoetic blood cells
  • Form mesenchymal stroma cells (multipotent adult stem cells)
  • Used in blood transplants to cure blood cancers (leukemia), immune deficiency disorders
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10
Q

What are embryonic stem cells and what are the ethical issues posed by their use?

A
  • Pluripotent

- Ethical issues: consent?

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11
Q

Why is C-section recommended in cases of placenta previa?

A
  • Baby might not make it to term: placenta is unstable, less uterine tissue
  • Increase risk of detachment: major blood loss
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12
Q

How can an ectopic pregnancy present clinically? And why are they life-threatening?

A
  • Implantation in any other place except for uterine lining
  • Signs: missed period, hemorrhage, brown watery discharge, lower abdominal pain on one side
  • Can rupture blood vessels leading to internal bleeding (burst fallopian tube)
  • 4-8 days after implantation
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13
Q

What are the most common causes of maternal mortality globally?

A
  • Poverty: lack of resources
  • Complications from delivery
  • Pre-eclampsia: High BP during pregnancy
  • Severe bleeding
  • Infections
  • Unsafe abortion
  • Diabetes
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14
Q

In the UK, maternal mortality is due to…

A
  • Stroke
  • Pulmonary embolism
  • Deep vein thrombosis
  • Postnatal depression
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15
Q

How long is the different stages in pregnancy?

A
  • Pre-embryonic (1-3 weeks)
  • Embryonic (3-8 weeks)
  • Fetal (9-38 weeks)
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16
Q

Where does fertilisation usually occur? What is the ideal site of implantation? And how long is oocyte/sperm viable for?

A
  • Ooctye released from ovary –> fertilised in ampulla of Fallopian tube
  • Endometrium ideal site of implantation
  • Oocyte - 1 day, sperm - 3 days
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17
Q

What is cleavage and what is its results?

A
  • First mitotic division
  • Forms 2 blastomeres of equal size
  • Zona pellucida (glycoprotein shell) prevent entry of sperm
18
Q

What forms after blastomeres in day 3? Is it totipotent or pluripotent?

A
  • Morula (16 cells)

- Totipotent: Capacity to form any type of cell

19
Q

What is Pre-implantation Genetic Diagnosis (PGD)? Why is it preceded by IVF?

A
  • Cell removed from morula tested for hereditary diseases prior to transfer of embryo to mother
  • IVF, oocyte taken from mother, fertilised in vitro, morula then transferred for implantation
20
Q

In week 1, compaction occurs. What happens in compaction?

A
  • Formation of first cavity
  • Blastocyst formed: Outer cell mass (trophoblast) –> form placenta, inner cell mass (embryoblast)
  • After compaction, cells become pluripotent (diff into many type of cells)
21
Q

On day 5, hatching occurs. Why?

A
  • Blastocyst hatches from zona pellucida, free to divide

- Interact w uterine surface

22
Q

What happens at the end of 1st trimester?

A
  • Implantation (100 cells)
23
Q

What occurs in differentiation?

A

Outer cell mass:

  • Syncytiotrophoblast (outside)
  • Cytotrophoblast

Inner cell mass:

  • Epiblast
  • Hypoblast
24
Q

What is the significance of implantation?

A
  • Implantation is interstitial: Conceptus implants itself within the endometrium
  • Establishes maternal blood flow within the placenta (support, nutrients)
  • Establishes basic structural unit for maternal-fetal exchange
25
Q

Describe some implantation defects

A
  1. Placenta previa: Implantation occurs in lower uterine segment (cervix)
    - Can cause haemorrhage
    - Require C-section
  2. Ectopic pregnancy: Implantation anywhere other than endometrium (peritoneal, ampulla)
    - Life-threatening emergency
26
Q

Summary of first lecture

A
  • Zygote –> morula –> blastocyst
  • Inner cell mass: epiblast & hypoblast –> germ disc
  • Outer cell mass: Syncytiotrophoblast & cytotrophoblast –> placental membranes
27
Q

What are some risk factors of ectopic pregnancy?

A
  • IVF
  • Past pelvic infections
  • IUCD
  • Becoming pregnant whilst on progesterone-only contraceptive pills
28
Q

Symptoms of ectopic pregnancy

A
  • Abdominal pain
  • Pelvic pain
  • Vaginal bleeding
  • Breast tenderness
  • Dizziness
29
Q

Signs of ectopic pregnancy

A
  • Pelvic/abdominal tenderness
  • Pallor
  • Enlarged uterus
  • Tachycardia/Hypotension
30
Q

Risk factors of placenta previa are?

A
  • Previous history of P.P
  • Previous caesarean section
  • Age
  • Smoking
  • Cocaine use during pregnancy
31
Q

Symptoms of placenta previa

A
  • Incidental finding on ultrasound scanning
  • Painless bleeding (sudden, X last long)
  • Risk of preterm delivery
32
Q

What are some teratogenic agents?

A
  • Thalidomide
  • Radiation
  • Rubella virus
33
Q

How deadly is the impact of teratogenic agents during pre-embryonic, embryonic & fetal phase?

A
  • Pre-embryonic: lethal effects
  • Embryonic: V. sensitive
    (after embryonic period, risk of structural defects very low, except CNS)
  • Fetal: Less sensitive
34
Q

State the 4 key events in order

A

Gonna Need Some Food

Gastrulation –> Neurulation –> Segmentation –> Folding

35
Q

What is gastrulation?

A
  • Epiblast diff. into 3 layers (endo,meso & ecto)
    [bilaminar –> trilaminar disc]
  • Hypoblast displaces to form yolk sac
36
Q

What are some derivatives of endo,meso and ectoderm?

A

Ectoderm: Organs & structures that have contact w outside world

  • Nervous system
  • Skin

Mesoderm: Supporting tissues

  • Muscle
  • Cartilage
  • Liver (organs)
  • Bone

Endoderm: Internal structures

  • Epithelial lining of GI tract
  • Respiratory tract
37
Q

What is situs inversus and what causes it?

A
  • Heart is on right side
  • Caused by immotile cilia, no associated morbidity

(Action of ciliated cells on primitive node pushes cell signalling molecules to left)

38
Q

When does gastrulation occur, how and why?

A
  • Occurs in third week of development, start of embryonic period
  • How? Primitive streak forms –> migration & invagination of epiblast cells
  • Why? Ensure correct placement of tissues to allow for morphogenesis
39
Q

What are somites and what forms them?

A
  • Paraxial mesoderm (forms somatic [limbs,muscle] & splanchnic [heart muscles] mesoderm)
    Extra: coelom form body cavities (mesoderm)
  • Somites are regular blocks of mesoderm cells
  • Undergo organised degeneration (somite –> sclerotome –> dermatome & myotome)
40
Q

What are derivatives of dermatome, sclerotome and myotome?

A
  • Dermatome: Skin
  • Sclerotome: (hard tissue) bone
  • Myotome: muscle
41
Q

How many somites are there? What do they give rise to?

A
  • 31

- Form ribs, vertebrae, spinal cord segments

42
Q

What does folding achieve?

A
  • Creates margins of the disk (endo inside, ecto outside)
  • Creates ventral body wall
  • Makes embryo suspended in amniotic sac

BL Sem 1 (13 decks)

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