FORMATION OF THE FACE AND ORAL CAVITY Flashcards
It is the crucial development event wherein folding in two planes along the rostro-caudal axis and along the lateral axis occurs.
Folding of the embryo
In the folding of the embryo, it is the first to appear
Head fold
It is produced as a result of craniocaudal elongation caused by the rapidly developing notochord and CNS
Head fold
It is critical to the formation of a primitive stomatodeum/oral cavity for it is through this fold that the ectoderm comes to line the stomatodeum
Head fold
2 IMPORTANT TISSUE STRUCTURES IN THE DEVELOPMENT OF THE FACE AND ORAL CAVITY
Pharyngeal arches
Neural Crest Cells
Arise from the 4th week of development as out pocketings of mesoderm on both sides of pharynx
Each has a branch of aorta, cranial nerve, and cartilage bar associated with it.
Pharyngeal arches
Specialized cell lineage which originate from the neuroectoderm
Cells enter the pharyngeal arches to help contribute to their derivatives
Migrate throughout the body to form the various structures of relevance to the head and neck
Neural Crest Cells
The depression or the primitive mouth is bounded at this point caudally by?
Developing cardiac plate
The depression or the primitive mouth is bounded at this point laterally by
First pair of pharyngeal/branchial arches
The depression or the primitive mouth is bounded at this point posteriorly by
The buccopharyngeal membrane
Due to the spread of the arches midventrally, It is eliminated from the stomadeum and the floor of the mouth is formed by the epithelium covering the mesenchyme of the first, second, and third branchial arches.
cardiac plate
Multipotent stromal cells that can differentiate into a variety of cell types
Mesenchyme/Mesenchymal Cells
Variety of cell types of the mesenchyme/mesenchymal cells
Osteoblast
Chondrocytes
Myocytes
Adipocytes
bone cells
Osteoblast
cartilage cells
Chondrocytes
muscle cells
Myocytes
fat cells which give rise to marrow adipose tissue
Adipocytes
About 24 days, First branchial arch establishes another process called the _________.
maxillary process
The stomatodeum is now limited cranially by:
Rapidly expanding forebrain
The stomatodeum is now limited Laterally by:
Newly formed maxillary process
The stomatodeum is now limited laterally by:
First branchial arch now called the mandibular arch
Ruptures, connecting the primitive mouth to primitive gut
Buccopharyngeal membrane
ectodermal/ tissue bulges outward, first termed as the mandibular arch
FIRST PHARYNGEAL ARCH
Mesenchyme divides into ____________ and ____________.
dorsal maxillary process and ventral mandibular process
Maxilla, zygoma, palatine, and squamous temporal bones
Maxillary process
Becomes ossified to form the malleus and incus
Dorsal end of maxillary process (meckel’s cartilage)
WHAT PHARYNGEAL ARCH?
Musculature
- Muscles of mastication - masseter, temporalis, lateral pterygoid, medial pterygoid
- Anterior belly of digastric
- Mylohyoid
- Tensor tympani
- Tensor palatini
FIRST PHARYNGEAL ARCH
WHAT PHARYNGEAL ARCH?
Cranial nerve component
- Mandibular division of the trigeminal nerve (V)
FIRST PHARYNGEAL ARCH
Hyoid arch
SECOND PHARYNGEAL ARCH
WHAT PHARYNGEAL ARCH?
Neural - derived mesenchyme condenses to form a bar of cartilage known as Reichert’s Cartilage
SECOND PHARYNGEAL ARCH
WHAT PHARYNGEAL ARCH?
Gives rise to bony process, stylohyoid ligament and upper part of body and lesser horns of hyoid bone
SECOND PHARYNGEAL ARCH
WHAT PHARYNGEAL ARCH?
Forms facial muscles, vessels, and hyoid bone
SECOND PHARYNGEAL ARCH
WHAT PHARYNGEAL ARCH?
Cranial nerve: Facial Nerve (VII)
SECOND PHARYNGEAL ARCH
WHAT PHARYNGEAL ARCH?
Gives rise to the lower part of the body and greater horns of hyoid bone
THIRD PHARYNGEAL ARCH
WHAT PHARYNGEAL ARCH?
Supply nutrients to tissues
THIRD PHARYNGEAL ARCH
WHAT PHARYNGEAL ARCH?
Shifts the bloody supply to the face and internal and external carotid vessels
THIRD PHARYNGEAL ARCH
WHAT PHARYNGEAL ARCH?
Cranial nerve: Glossopharyngeal nerve (IX)
THIRD PHARYNGEAL ARCH
WHAT PHARYNGEAL ARCH?
Gives rise to cartilage of larynx
FOURTH PHARYNGEAL ARCH
WHAT PHARYNGEAL ARCH?
Vagus nerve (X)
FOURTH PHARYNGEAL ARCH
WHAT PHARYNGEAL POUCH?
Middle ear, eardrum, eustachian tube
FIRST PHARYNGEAL POUCHES
WHAT PHARYNGEAL POUCH?
Palatine tonsils
SECOND PHARYNGEAL POUCH
WHAT PHARYNGEAL POUCH?
Expands dorsally and ventrally into two compartments
THIRD PHARYNGEAL POUCH
WHAT PHARYNGEAL POUCH?
Dorsal component - gives origin to inferior parathyroid glands
THIRD PHARYNGEAL POUCH
WHAT PHARYNGEAL POUCH?
Ventral component
- with its anatomic counterpart from the opposite side, forms the thymus
THIRD PHARYNGEAL POUCH
WHAT PHARYNGEAL POUCH?
Dorsal component
- gives origin to superior parathyroid gland
FOURTH PHARYNGEAL POUCH
WHAT PHARYNGEAL POUCH?
Ventral component
- gives rise to ultimobranchial body, which gives rise to the parafollicular cells of thyroid gland
FOURTH PHARYNGEAL POUCH
WHAT PHARYNGEAL POUCH?
Rudimentary, either disappears or becomes incorporated into the fourth pouch
FIFTH PHARYNGEAL POUCH
WHAT BRANCHIAL CLEFT
Deepens to become the external auditory canal leading to the middle ear
The membrane at the depth of this tube becomes the tympanic membrane
1st Branchial clef
Normally obliterated by the overgrowth of second arch, but sometimes persist as a cervical sinus that may or may not open at the side of the neck
Second, third and fourth cleft
Are their any branchial clefts seen externally after fifth week
No
starts to develop between 3rd or 4th week of development
Face
What week?
- 4mm long
- Buccopharyngeal membrane ruptures
- Frontal process of brain bulges forward and laterally to dominate the facial area
- Immediately below is the mandibular arch, which appears divided or constricted at the midline
4th Week
WHAT WEEK?
- Expect the base of tongue and facial muscles, which are formed from 2nd and 3rd branchial arches, all of the face and all parts of oral and nasal cavities will develop from the two primary embryonic structures: Frontal process and first branchial arch (mandibular arch)
4th Week
WHAT WEEK?
- After stomodeum is established, budding of the round process happens on either side of the 1st branchial arch
- Buds grow upward and medially at the right and left sides of the promotive mouth - these buds are called the maxillary process
4TH WEEK
WHAT WEEK?
- Mandibular arch is divided into the maxillary process and mandibular processes
- After maxillary process are formed, the growth of the lower part of the face is retarded and upper part of the face starts a rapid development
4TH WEEK
WHAT WEEK?
- 8-10mm long
- On the lower border of the frontal process, bilateral olfactory placodes - thickened areas of epithelium, appear on the upper border of the lip
- With presence of nasal pit, frontal area became known as the fronto-nasal process
5TH WEEK
WHAT WEEK
- Nasal pits/nostrils continue to grow, deepen into sacs as the tissue around this placode grow
- Remains separated from the primitive oral cavity by the oronasal membrane
- Nasal pits divide the frontonasal process into the medial nasal process and the lateral nasal process
5TH WEEK
WHAT WEEK?
- The frontal prominences diminish and the face broadens
- Eye becomes prominent on the sides of the head
- Fusion of medial nasal processes has narrowed the entrance into the nasal pit
5TH WEEK
WHAT WEEK?
- 10mm long
- Start of this week, oronasal process ruptures
- At its lower boarder, median nasal process now grows in length and produces a pair of bulges called the globular processes
- Forms the philtrum of the lip and premaxilla
6TH WEEK
WHAT WEEK?
- Between maxillary process and nasal primordium is a nasolacrimal groove that extends to the developing eye
- Ectoderm of the floor of the groove thickens to form a solid epithelial cord, which detaches from the cord
- Epithelial cord undergoes canalization and forms the nasolacrimal duct and near the eye the nasolacrimal sac
6TH WEEK
WHAT WEEK?
- Six small hillocks of tissue, the auricular hillocks, grouped around the external ear canal
- Three of these come from the mandibular arch and three from the second or hyoid arch
6TH WEEK
WHAT WEEK?
- Fusion of medial and lateral nasal processes has further narrowed the nostrils
- Medial nasal process is reduced in relative width
- Eyes are at the lateral edges of the face
6TH WEEK
WHAT WEEK?
- 14mm long
- Face is more human appearance
- Because of rapid growth of surrounding areas, slower growing median nasal process becomes relatively more narrow and nasal opening relatively closer together
7TH WEEK
WHAT WEEK?
- Two maxillary processes grow forward and merge with the left and right sides of globular processes
- Globular process forms the center of the upper lip and the maxillary process form the sides of upper lip
7TH WEEK
WHAT WEEK?
- On upper median border, maxillary process is beginning to overlap the lateral nasal processes and the median nasal process is firmly attached to the lateral nasal process
- Closure also occurs at the corners of the mouth between the maxillary processes and mandibular processes
7TH WEEK
WHAT WEEK?
- Lateral growth of brain, resulting in facial expansion, causes the eye to appear in front of the face
- A third of the face has been added laterally to each nostrils
- Eyes are now on the same horizontal plane as the nostrils, which will change after the bridge of the nose develops and lengthens
7TH WEEK
WHAT WEEK?
- Ears at the level below the mouth cleft, which is exceptionally wide
- Danger of cleft lip has passed
7TH WEEK
WHAT WEEK?
18-25 mm long
- Front view is low and broad and almost square in outline
- Nasal septum narrowed further and nose is more prominent
- Ears are at the level of the mouth cleft which is very wide
8TH WEEK
WHAT WEEK?
- Lidless eye are on normal position
- Ridges around the eye will soon develop into eyelids
- Prominently projecting forehead and pronounced recession of lower jaw
8TH WEEK
WHAT WEEK?
- 60 mm long
- Eyelids are formed and closed
- Nostrils are closed
- Maxillo-mandibular relationship is nearly in normal position
- Face approaches human proportions
12TH WEEK
WHAT PROMINENCE?
Derivatives:
Forehead, bridge of nose, medial and lateral nasal prominences
Frontonasal
WHAT PROMINENCE?
Derivatives:
Philtrum, primary palate, upper 4 incisors, and associated jaw
Medial nasal
WHAT PROMINENCE?
Derivatives:
Sides of the nose
Lateral nasal
WHAT PROMINENCE?
Derivatives:
Cheeks, lateral upper lip, secondary palate, lateral upper jaw
Maxillary (1st pharyngeal arch)
WHAT PROMINENCE?
Derivatives:
Lower lip and jaw
Mandibular (1st pharyngeal arch
Result of non-union of margins of the globular and maxillary process (for the upper lip) and anterior margins of the mandibular process (for lower lip - true median cleft)
Cheiloschisis (cleft lip)
harelip, lack of fusion between two median nasal process
Median cleft lip
Slanting cleft, extending from the mouth up to the cheek even reaching the lower eyelid; lack of fusion between maxillary and lateral nasal process
Oblique facial cleft
Lack of fusion between maxillary processes and median nasal process
Bilateral cleft lip
Lack of fusion between median nasal process and maxillary process on one side
Unilateral cleft lip
Abnormally small jaw
Micrognathia
Abnormally large jaw
Macrognathia
Congenital absence of either the upper or lower jaw
Agnathia
Abnormally small mouth due to excessive union of maxillary and mandibular processes
Microstomia
Complete closure of mouth
Astomia
Featureless face
Aprosopus
