Oral Biology Embryology Final Prep

Front 1

What constitutes the embryonic period? What is this part of?

Back 1

Part of prenatal period.

•embryonic period refers to early stages of development
•fertilization to day 56 (8 weeks) •tissues and the organs are formed during the embryonic period •differentiation and growth of the organs continues in the fetal period.

Front 2

What is the critical period of development?

Back 2

The critical period of development is weeks 3-8 of development (or weeks 4-8).

Exposure to teratogens during first 2 weeks interfereces w/ implanation or directly kills the embryo.

It does NOT interfere with organ system development

Front 3

What is the difference between fertilization age and gestational age?

Back 3

• fertilization age(1)- The age of the embryo counting from the actual time of fertilization (usually day 14-16 of the menstrual cycle). Female releases egg (ovulation). Egg MUST be fertilized within 24 hours. From here, there's 2 weeks to the end of the cycle.
• gestational age(2) -How physicians calculate the age of the embryo- from the first day of the last normal menstrual period (LNMP). Since its hard to know exactly when you ovulation.
• gestational age is 2 weeks longer than fertilization age!

Front 4

What's happening in the ovary?

Back 4

1. produce hormones (endocrine function)
2. release the egg into the duct (exocrine)

The follicle is growing in the first stages. Estrogen is primary hromone. This triggers in spike of hormone in the peritoneal cavity.

After ovulation, corpus luteum forms. It either begins corpus luteum of menstruation or preganancy.

Front 5

What's happening in the endometrium?

Back 5

Day 14: very thick endometrium is sloughed off.

Proliferative phase - Day 14 majority of mitosis occurs
Secretory phase/progestational - Day 21 - filled with glycoens and lipids to nourish embryo
Day 26-28 ischemic stage - stops producing hormones and arteries clamp off and die.

Day 1 - back after sloughing off.

Front 6

2 major events in the ovary..

Back 6

1. maturation of oocyte:
primary oocyte to secondary, to definitive oocyte or ovum/fertilized oocyte. The only time that female completes meiosis 2.

2. maturation of follicle - occurs in prenatal stage

flat stromal cells surround the oocyte (meiosis I) - primordial follicle

-there are millions of these that go through atresia (atretic follicles)

puberty: becomes the primary follicle. Zona pellucida forms. follicular cells/stromal cells become cuboidal instead of flat.

now as cuboidal, they're called granulosa cells ( now producing hormones)

2ndary follicle: fluid filled antrum. primary oocyte is still stuck in meiosis I.

mature follicle/Graffian: the chosen follicle that will ovulate. once its larger, it becomes the secondary oocyte.

oocyte, zona pellucida, and corona radiata are all released into the peritoneum.

Front 7

What portion of the infundibulum/fimbriae responsible to get ovum in the right place?

Back 7

1. cilia are responsible for movin the ovum to the proper area of the oviduct.

Front 8

What is an eptopic pregnancy?

Back 8

Any fertilization that happens outside the uterus

Front 9

What happens in the ampulla?

Back 9

1. 200 to 600 million sperm are ejaculated into female.
only 1 sperm will penentrate corona radiata and zona pellucida (zone reaction)
2. fusion of plasma membranes of oocyte and sperm
3. resume meiosis 2; female pronucleus and 2nd polar body forms. (female cell is larger)
4. Male pronucelus forms. BOTH male and female replicate DNA
5. Pronuclei fuse into 1 diploid cell = zygote. 30 hrs after fertilization, it gets ready to divide.

Mitotic divisions are called cleavage divisions, and there's no reduction or increase in cytoplasmic mass.

However, with daughter cells (blastomeres) become smaller in size with each division

Front 10

What events are responsible for genetically unique zygote?

Back 10

1. random distribution
2. synapsis - during meiosis 1

Front 11

1. Totipotent?

Back 11

• latin, “capable of forming everything”
• in humans the 8-cell embryo stage is the last stage of totipotency (day 3 of development)
• each individual cell is capable of producing trophoblast and embryoblast precursors

Front 12

When does the morula enter the uterine cavity?

Back 12

3 days post fertilization. cavitation: trophoblast cells secrete fluid into morula and create cavity (stimulated by oviduct cells)
• the developing embryo is now a blastocyst or blastula
• the zona pellucida starts to disintegrate and cell division results in average sized daughter cells

Front 13

What happens after we have cavitation and fluid in the cavity? What can these cells seperate into?

Back 13

1. outer cell layer =trophoblast, contributes to the placenta
2. centrally located cells =the inner cell mass or embryoblast, giving rise to the tissues of the embryo
The cells of the embryoblast are attached to the trophoblast at the embryonic pole of the blastocyst.

Front 14

Why is it important for the blastocyst to hatch? What happens to zona pellucida?

Back 14

It degenerates slowly..
• allows for growth of the conceptus
• zona pellicuda prevented
attachment to oviduct wall – absence allows the trophoblast layer to implant in the endometrial lining of the uterus

Front 15

What is the implantation day corrsponding to the female reproductive cycle?
To the days post fertilization?

Back 15

Female reproductive cycle: Day 21
days post fertilization: Day 6

Front 16

What is HCG?

Back 16

hormone that helps to maintain the corpus luteum of pregnancy.

Front 17

Back to the trophoblast..

What are the 2 layers that it divides into at the embryonic pole?

Back 17

A. outer mass- some trophoblasts fuse to make a large multinucleated cell -the syncytiotrophoblast
B. inner layer of cells- some trophoblast cells remain unfused and are called the cyotrophoblast
• mitotically active layer of cells that migrate into the increasing mass of syncytiotrophoblast,

Front 18

Epithelium

Back 18

• one of the four basic tissue types
• line body cavities, constitutes glands
• avascular
• exhibit polarity- three functional domains (apical, basal, lateral)
• always associated with basement membrane

Front 19

What are the functions of epithelium?

Back 19

• selective barrier (inhibits or facilitates passage to underlying connective tissue)
• secretion • absorption • transport • protection

Front 20

How is epithelium classified?

Back 20

First name is based on number of layers (simple, stratified, pseudostratifed)

then by shape of cell (cuboidal, squamous, etc.)

Front 21

What structures are transient?
1. primary yolk sac
• secondary yolk sac • chorionic cavity • hypoblast • buccopharyngeal membrane • cloacal membrane • pharyngeal arch 5 • pharyngeal membrane I • pharyngeal clefts 2-5 • pharyngeal pouch 5 • neural crest

Back 21

1. Yes - goes away
2. Yes
3. Yes
4. lose it when embryo swallows
5. gone at Day 26
6. gone at day 26
7. disappears
8. no, stays as tympanic membrane
9. all go away
10. cleft 1: EAM
11. pouch 5 - thought to go away
12. neural crest - go away. Cells stay with us.