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Period: to
Prenatal timeline
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Meiosis (1st week)
Sperm chromosomes are shared among some of the ovum chromosomes to become one. The joining of chromosomes creates a new individual.
During meiosis process, a chromosome mutations may occur. -
Chromosome mutation; first week of pregnancy
A example of a chromosome mutation would be down syndrome. This occurs in 1 out of 10 cases, due to an extra chromosome.
Some orofacial features of a individual with down syndrome includes; flat and broad face, widely spaced eyes, flat-bridged nose, epicanthic folds, furrowed lip, etc.
An arched pallet and weak tongue muscles may also occur and protrusion of the tongue.
This may lead to periodontal disease, delayed tooth eruption, and fewer teeth present. -
Embryonic folding
Embryonic folding starts, when a flat disk starts to form into a cylinder. Which is composed of three layers; Ectoderm, Mesoderm, and Endoderm. -
Fourth week
During the fourth week the face and neck are beginning to develop.
This includes primitive eyes, ears, nose, oral cavity, and jaw areas. -
Orpharynageal membrane
As the endoderm gastric track moves towards the midline, it starts to forms the forward gut, Mid gut, and Hi-gut.
The forward gut contains the oropharyngeal membrane.
At the end of the forth week it will rupture to form the mouth. -
Facial development
Adult and embryonic faces development depends on five facial processes.
The five facial processes are; frontonasal, maxillary, maxillary, mandibular, and mandibular.
It takes a total of 12 weeks to finish facial development. -
Facial fusion; Week four
There is two types of facial fusions. First type is when two adjacent swelling of tissues form a grove between the same surface of embryo. Involving facial surfaces such as the philtrum.
Second type is when fusion is from tissue from two different surfaces coming together. Examples are upper lip, pallet, and jaw. -
Stromodeum
Stromedeum is limited to depth by the oropharyngeal membrane. Which separates the stomedeum from the primitive pharynx,
If the membrane was disintegrated it would increase the opening of the stomedeum, creating access to primitive pharynx.
The mandibular processes fuses form a arch (another name would be brachial arch), just inferior to the enlarged stomodeum. -
Placode development
Placode is rounded areas of specialized, thickened ectoderm found at the location of developing special sense organs. Such as the lensed, otic's, and nasals. -
Paired median nasal processes externally and internally
External fuse form the middle of the nose, root of the nose, tubercle of the lib and philtrum.
Internally fuse forms the inter maxillary segments; maxillary incisor teeth, primary palate, and nasal septum. -
Brachial Apparatus and Arches
There are six U-shape bar pairs of brachial arches. Theses arches support the walls of developing pharynx.
The first brachial arch is called the Mandibular arch.
The second thru fourth structures the neck; the second arch is called the Hyoid arch, third is the Portions of hyoid
Fourth thru six form larynx and pharynx.
