Prenatal & Face/Neck Development

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1.     What is embryology? Study of prenatal development.

2.     What are the 3 periods of prenatal development? Pre implantation, embryonic, fetal.

3.     Earliest indication of part or organ during pre natal development is: primordium.

4.     In what week does pre implantation take place? 1^st week.

5.     An egg that is fertilized by sperm is: zygote.

6.     Zygote undergoes mitosis, what is mitosis? Individual cell division.

7.     The zygote keeps dividing into a ball of cells that becomes a: morula.

8.     Blastocyst: bigger morula/ ball of cells, still traveling.

9.     How does the uterus prepare to accept the blastocyst? Uterus lining gets thicker.

10.                         Describe the process of implantation: Once the blastocyst reaches the uterus, it embeds itself in the endometrium (sticky wall).

11.                         List the layers of the blastocyst & what they eventually will become: trophoblast layer: which becomes the prenatal support tissues, embryoblast layer: eventually becomes the embryo.

12.                        When does the embryonic period take place? 2-8 week.

13.                         There are 5 processes in the embryo, list them in order and their function:

1.     Induction: interaction between cells, cells talking to each other.

2.     Proliferation: controlled levels of cellular growth with accumulation of cellular by products.

3.     Differentiation: change that occurs in embryonic cells that is identical genetically so they can become structurally & functionally different. Any cells formed during this time are those, which perform a specific function such as, heart, lungs, liver, kidney. They form at different rates.

4.     Morphogenesis: development of specific tissue by their form by migration of embryonic cells. Continued interaction among cells to develop into different forms.

5.     Maturation: fetal period (adult size & form).

14.                        Interstitial growth: deep with in tissue or organ. (Soft tissue, heart, lungs).

15.                        Appositional growth: Tissue enlarges by addition of layers on outside of structure. (Bone).

16.                         At which week is embryo recognized as looking like a human being? 8 weeks.

17.                         In prenatal development, where does the bilaminar embryonic disc originate? Blastocyst.

18.                        From what disc does the embryo develop? Bilaminar disc.

19.                        The bilaminar disc has 2 layers, what are they and what type of epithelium do they have?

20.                        In what week is the bilaminar disc forming? 2^nd week.

21.                        The bilaminar disc suspends in the uterus’ endometrium between what 2 cavities? Amniotic cavity & Yolk sac.

22.                         Fill in chart with the cavities & their function if any:

23.                        In the 3^rd week the primitive streak forms and will cause disc to have bilateral symmetry.

24.                        What is bilateral symmetry? Gives uniform appearance. Right & left halves.

25.                        What is mesenchyme? Embryonic connective tissue. Creates a new layer called mesoderm.

26.                        Where is mesenchyme located? Between cell layers.

27.                        Bilaminar become trilaminar because of: the addition of mesoderm.

28.                        The disc thickens & becomes a trilaminar embryonic disc. List layers & what they create:

29.                        The features of the trilaminar disc:

Cephalic end~ head

Oropharnygeal membrane~ only endoderm & ectoderm. Becomes the full mouth.

Caudal end~ butt/tail.

Cloacal membrane~ becomes anus.

Primitive CNS~

Neuroectoderm~ Specialized cells that run from head to tail end. Grow & form neural groove.

Neural groove~ Neuroectoderm cells growing as they grow they form folds that eventually form neural tube.

Neural tube~ Undergoes fusion & becomes spinal cord.

30.                        What cells are considered to be the 4^th embryonic layer? Neural crest cells.

31.                        What are neural crest cells? Specialized cells that develop from Neuroectoderm, and help in the development of structures that form the face & neck.

32.                         Somites:

What are they: masses of mesoderm that continue to divide.

Where are they? In area of neural tube.

Becomes: Skeleton, head, neck, trunk, muscles,

dermis of skin.

33.                        What does the disc undergo in the 4^th week?  Embryonic folding.

34.                         Where does embryonic folding occur? Head end & tail end.

35.                        What happens during this folding? The disc takes on a more recognizable form, & a hollow tube is formed that runs from head to tail.

36.                        What is the tube that forms during embryonic folding? Future digestive tract.

37.                         The future digestive tract separates into 3 regions:

Foregut: forms pharynx

Midgut: forms rest of throat & rest of digestive tract.

Hindgut: forms rest of throat & rest of digestive tract.

38.                        Teratogens are anything that can cross the placenta & harm the fetus. List some examples and the cause:

German Measles (rubella): blindness, deafness.

Syphilis: blindness, defects in teeth.

Fetal alcohol syndrome: retardation, growth deficiencies.

Radiation:  not during 1^st trimester. Depends on dosage: cell death, chromosome injury.

39.                        In what week does the fetal period begin? 9^th-10^th.

40.                        What happens when the embryo enlarges? The existing structures mature and become fetus.

41.                        When does breathing start? 3^rd week.

42.                        By the end of the 4^th month what can be detected? Heart beat.

43.                         Cartilage of mandibular arch: Meckle’s Cartilage.

44.                         When does Meckle’s cartilage disappear? After mandible is formed.

45.                         What does the mandibular arch eventually become? Lower face & bottom lip, muscles of mastication, nerve&blood supply & part of tongue.

46.                         Placodes: rounded areas located on outer surfaces of frontonasal process.

47.                         What are the 3 placodes located on either side of the frontonasal process? Lens placode (eyes), Otic placode (ears), & nasal placode (nose).

48.                         What does the median nasal process form? Tissue around nasal placodes. Middle of nose, philitrum region, intermaxillary segment, center of lip.

49.                         What does the intermaxillary segment form? Palate, nasal septum, maxillary incisor teeth.

50.                         What does the lateral nasal process form? Nasal alae, sides of nose, nostrils, outer portion of tissue located around nasal placodes.

51.                         The upper lip is formed in what week? 6^th.

52.                         What 2 processes form the upper lip? Maxillary process fusing w/ each of the medial nasal processes.

53.                         Five Facial Processes:

54.                        What is the cause of cleft lip? Failure of fusion between maxillary process with medial nasal processes.

55.                        The primitive pharynx and brachial apparatus develop: the neck.

56.                         What is the brachial apparatus made up of? Brachial arches, grooves, membranes, & pharyngeal pouches.

57.                        What are brachial arches? 6 pair of U-shaped bars of tissue.

58.                         What do the brachial arches support? The lateral walls of primitive pharynx.

59.                         Fill in chart about Brachial Arches

60.                        What are pharyngeal pouches? Balloon like structures that will develop tissues of face & neck.

61.                        Name, in order, the pouches that form & what they form? 1^st: auditory tube & lympanic nerve, 2^nd: palatine tonsular tissue, 3^rd: parathyroid & thymus glands.

 Disclaimer: These notes were copied and pasted from files sent to me by Andrea.  They have not been reviewed for errors. You are responsible for checking out the information to verify the accuracy. This site, Amy Nieves and Andrea are not responsible for typographical errors.