Embryology Flashcards
What happens in the first week of embryology?
- Ovulation
- Fertilisation
- Implantation
(no time scale)
What is ovulation?
- Egg released from ovaries and travels through fallopian tube
- Uterus prepares to receive egg - wall thickens
What is implantation?
- Fertilised egg attaches to wall of uterus
What is a fertilised ovum called?
Zygote
Your’e a zygote
What is a morula?
Lump/clump of cells
Lump Clump Bump Dump
What is a blastocyst?
A hollow ball of cells:
- Inner cell mass
- Trophoblast
(Like Georgie’s heart) JK
What is a trophoblast?
A layer of tissue on the outside of a mammalian blastula, supplying the embryo with nourishment and later forming the major part of the placenta
(AKA LP)
What is the placenta?
A system that will organise the transport of nutrients to developing embryo and remove the waste from is
- At the beginning of implantation there is an organisation to help the embryo establish the placenta
(A yucky thing)
Explain the exchange of nutrients through the barrier between the baby’s blood and the mothers blood?
- The babies blood is replenished from the mothers blood
- The circulations do not mix. They are separated by a thin barrier
- The barrier is permeable to most molecules, but not cells
(How was coffee?)
At approximately 10-12 days, the implanted trophoblast contains an embryo, which has 2 cell layers. What are the names of these layers?
- Epiblast
- Hypoblast
(Abbyblast)
What does the epiblast give rise to?
The embryonic ectoderm, mesoderm and endoderm
Or does it ;)
What does the hypoderm give rise to?
Participates in the formation of endoderm and extraembryonic mesoderm
(What kind of a word is mesoderm LOL)
What is meant by the term ‘gastrulation’?
- Means the formation of gut, but now has a more broad sense to describe the formation of the trilaminar embryo. The epiblast layer, consisting of totipotent cells, derives all 3 embryo layers; ectoderm, mesoderm and endoderm. The primitive streak is the visible feature which represents the site of cell migration to form additional layers
(or does it mean farting?)
What is the bilaminar embryo?
- It is a disk
- It has no distinct orientation or axis
(Do u have a distinct orientation and axis?)
What happens during gastrulation?
The embryo develops:
- An axis
- The three embrionic cell layers
What is the key stage of formation during gastrulation?
The formation of a groove: the primitive streak
What is the primitive streak?
- Some ectodermal cells are induced to differentiate and migrate through the primitive streak, towards the hypoblast
- These new cells are the mesoderm
- A ‘not so clear’ interaction between the newly formed mesoderm and the hypoblast will form the endoderm
During what weeks do the major organs develop?
- 3-8 weeks
- They develop from the 3 basic germ cell layers
- This is ‘organogenesis’
Give an example of one of the first organs to be formed during organogenesis?
The CNS
What is present at 19-20 days?
- The neural groove is evident and some muscles are present
What is a disease caused by the developmental defect of the neural tube?
Spina bifida
What is mesenchyme?
A loosely organised, mainly mesodermal embryonic tissue which develops into connective and skeletal tissues, including blood and lymph
What is the neural crest derived from?
The ectoderm, but has the characteristics of mesenchyme
- This is very important in the development of the head
What is meant by the ‘trilaminar’ embryo?
The front and back ends begin to fold under the middle
At around how many days does the embryo fold round the yolk sac, and some important organs appear?
Around 25 days
When is the embryo then called a foetus?
From 9 weeks onwards
What are stem cells?
- Unspecialised cells that can develop into more specialised cells
What is a totipotent stem cell?
- Can differentiate into anything
What is a pluripotent stem cell?
- Can produce any organ from a specialised group
What are embryonic stem cells?
- Inner cell mass (totipotent)
- Cells in the 3 germ layers are more restricted in potential (pluripotent)
What are adult stem cells?
Generally committed cell lines e.g. bone marrow stem cells
What does stem cell development involve?
Genes and various signalling molecules
What are the 3 primary embryonic layers?
- Ectoderm - outer covering
- Mesoderm - middle
- Endoderm - Inner lining
What does the ectoderm produce?
- Skin
- Mucous membranes of mouth and anus
- Brain, spinal cord
- TOOTH ENAMEL
What does the mesoderm produce?
- Most connective tissues
- Dermis, tendons, cartilage, bone
- Muscle (most)
- Blood vessels
- Kidney and urinary system
- Reproductive system
- Serous membranes
What does the endoderm produce?
- Alimentary canal
- Respiratory system
- Parts of the urogenital system
What is the name of the fourth layer of the embryo?
Ectomesenchyme
What does the Ectomesenchyme give rise to?
- Most of the PNS: sensory and autonomic
- Melanocytes in skin
- Adrenal medulla
- Most of the mesenchyme in the head
- muscles, connective tissues, most dental and periodontal tissues - EXCEPT ENAMEL
- Dentine, cementum, pulp, periodontal ligament, jaw bones
When do developmental abnormalities occur?
During ‘critical’ or ‘sensitive’ periods during development
What occurs if there is a developmental abnormality in the first 2 weeks of pregnancy?
Spontaneous abortion
what happens if there is a developmental abnormality in weeks 3-12 (first trimester) of pregnancy?
- Period of greatest sensitivity
- Most developmental defects occur during this period
What ‘period’ is weeks 13-39 of pregnancy?
The period of functional maturity
P.s. Leanne smells LOL
