Embryology

Question 1

What is the Fimbria?

Answer 1

It is a finger-like projection near ovary.

Question 2

When does DNA duplication occur?

Answer 2

3 days.

Question 3

What are the three layers of the uterine wall?

Answer 3

Endometrium, perimetrium and myometrium.

Question 4

What is the Graafian follicle?

Answer 4

A fluid-filled structure in the mammalian ovary within which an ovum develops prior to ovulation.

Question 5

A fertilised ovum is known as a what?

Answer 5

Zygote.

Question 6

What is a lump of cells called and what period of time would the cells be called this?

Answer 6

Morula- 4-6 days.

Question 7

At what period of time do the cells become known as a blastocyst?

Answer 7

6-10 days.

Question 8

What does a blastocyst consist of?

Answer 8

An inner cell mass and trophoblast.

Question 9

At what period of time is a bilayer embryo found?

Answer 9

10-12 days.

Question 10

What is the function of an epiblast?

Answer 10

Gives rise to the three primary germ layers (ectoderm, definitive endoderm, and mesoderm)

Question 11

What is the function of a hypoblast?

Answer 11

Participates on formation of endoderm and extraembryonic mesoderm.

Question 12

What is the ectoderm and what does it form during embryonic development?

Answer 12

outer covering= skin, mucous membranes of mouth and anus, brain, spinal chord, TOOTH ENAMEL.

Question 13

What is the mesoderm and what does it form during embryonic development?

Answer 13

middle= most connective tissues (dermis, tendons, cartilage, bone), muscle

Question 14

What is the endoderm and what does it form during embryonic development?

Answer 14

inner lining= alimentary canal, respiratory system, parts of urogenitial system.

Question 15

What is gastrulation?

Answer 15

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.

Question 16

How is the mesoderm formed?

Answer 16

It is formed by the migration of cells towards the hypoblast.

Question 17

What is organogenesis and when does it occur?

Answer 17

During weeks 3-8 the major organs form from the basic 3 germ cell layers.

Question 18

What is one of the first organs to be formed?

Answer 18

The CNS.

Question 19

What does the primitive steak then form?

Answer 19

The nerual tube.

Question 20

What is spina bifida.

Answer 20

It is when the fetal spinal column doesn’t close completely.

Question 21

What 3 structures are important within the developing of the face?

Answer 21

Notochord, neural fold and neural crest .

Question 22

Where is ectomesenchyme derived from?

Answer 22

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).

Question 23

What happens in the first stage of the embryo taking shape?

Answer 23

• 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.

Question 24

What happens in the second stage of the embryo taking shape?

Answer 24

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.

Question 25

What are the periods of time when the cells are called an embryo and a foetus.

Answer 25

Embryo- 4-7 weeks.

Foetus- 9-20 weeks.

Question 26

How and when are natural abortions more likely to happen?

Answer 26

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.

Question 27

Why is the ectomesenchyme important to dental studies?

Answer 27

• 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.

Question 28

What is a morula?

Answer 28

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.