Embryology Flashcards
What is the Fimbria?
It is a finger-like projection near ovary.
When does DNA duplication occur?
3 days.
What are the three layers of the uterine wall?
Endometrium, perimetrium and myometrium.
What is the Graafian follicle?
A fluid-filled structure in the mammalian ovary within which an ovum develops prior to ovulation.
A fertilised ovum is known as a what?
Zygote.
What is a lump of cells called and what period of time would the cells be called this?
Morula- 4-6 days.
At what period of time do the cells become known as a blastocyst?
6-10 days.
What does a blastocyst consist of?
An inner cell mass and trophoblast.
At what period of time is a bilayer embryo found?
10-12 days.
What is the function of an epiblast?
Gives rise to the three primary germ layers (ectoderm, definitive endoderm, and mesoderm)
What is the function of a hypoblast?
Participates on formation of endoderm and extraembryonic mesoderm.
What is the ectoderm and what does it form during embryonic development?
outer covering= skin, mucous membranes of mouth and anus, brain, spinal chord, TOOTH ENAMEL.
What is the mesoderm and what does it form during embryonic development?
middle= most connective tissues (dermis, tendons, cartilage, bone), muscle
What is the endoderm and what does it form during embryonic development?
inner lining= alimentary canal, respiratory system, parts of urogenitial system.
What is gastrulation?
Gastrulation is a phase early in the embryonic development of most animals, during which the single-layered blastula is reorganized into a multilayered structure known as the gastrula. The embroidery develops and axis and the three embryonic layers.
How is the mesoderm formed?
It is formed by the migration of cells towards the hypoblast.
What is organogenesis and when does it occur?
During weeks 3-8 the major organs form from the basic 3 germ cell layers.
What is one of the first organs to be formed?
The CNS.
What does the primitive steak then form?
The nerual tube.
What is spina bifida.
It is when the fetal spinal column doesn’t close completely.
What 3 structures are important within the developing of the face?
Notochord, neural fold and neural crest .
Where is ectomesenchyme derived from?
The ectoderm. It has the characteristics of mesenchyme (a loosely organized, mainly mesodermal embryonic tissue which develops into connective and skeletal tissues, including blood and lymph).
What happens in the first stage of the embryo taking shape?
- The trilaminar (3 layers) embryo: the front and back ends begin to fold under the middle.
- Longnitudinal layer reearrangement. Folding on front and back of embryo forming other tissues- creates pericardium.
What happens in the second stage of the embryo taking shape?
About 25 days.
The embryo folds round the yolk sac, and some important organ appear (heart, liver, lungs).
Organisation of mouth and formation of lung. Very early-great development of number of organs.
What are the periods of time when the cells are called an embryo and a foetus.
Embryo- 4-7 weeks.
Foetus- 9-20 weeks.
How and when are natural abortions more likely to happen?
Notice how fast the process is going. Mitosis is sensitive process, is prone to failures. Natural abortions- fragile period associated with rapid modification first 12 weeks. Moving from embryo to foetus.
Why is the ectomesenchyme important to dental studies?
- A ‘fourth’ layer, very relevant to dental studies. It gives rise to:
- Most of the peripheral nervous system: sensory and autonomic nerves
- 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.
What is a morula?
A morulla is a “rounded closely packed mass of blastomeres.” This stage is short-lived. Morulla consists of two or more layers of disc-shaped mass of cells called blastoderm. The cells are smaller and completely defined at the center of the blastoderm while cells are larger and flattened at the corners of blastoderm.
