Development of face and oral cavity

Question 1

Origin of facial tissues

After fertilization of the ovum, a series of cell divisions gives rise to an egg cell mass known as the ______ in mammals.

Answer 1

morula

Question 2

Origin of facial tissues

In most vertebrates, including humans, the major portion of the egg cell mass forms the ______ and other supportive structures, such as the ______.

Answer 2

extraembryonic membranes, placenta

Question 3

Origin of facial tissues

The inner cell mass separates into two layers, the ______ and ______.

Answer 3

epiblast, hypoblast

Question 4

Origin of facial tissues

Cell marking studies in chick and mouse embryos have shown that only the ______ forms the embryo, with the ______ and other cells forming supporting tissues, such as the placenta.

Answer 4

epiblast, hypoblast

Question 5

Origin of facial tissues

The ______ (______) end of the primitive streak forms the lower germ layer, the ______, in which are embedded the midline ______ (and ______) plates.

Answer 5

anterior, rostral, endoderm, notochordal, prechordal

Question 6

Origin of facial tissues

Prospective mesodermal cells migrate from the epiblast through the primitive streak to form the middle germ layer, the ______.

Answer 6

mesoderm

Question 7

Origin of facial tissues

Cells remaining in the epiblast form the ______, completing formation of the three germ layers. Thus, at this stage, three distinct populations of embryonic cells have arisen largely through ______ and ______. They follow distinctly separate courses during later development.

Answer 7

ectoderm, division, migration

Question 8

Origin of facial tissues

Migrations, such as those described above, create new associations between cells, which, in turn, allow unique possibilities for subsequent development through interactions between the cell populations. Such interactions have been studied experimentally by isolating the different cell populations or tissues and recombining them in different ways in culture or in transplants. From these studies it is known, for example, that a median strip of mesoderm cells (the ______) extending throughout the length of the embryo induces ______ formation within the overlying ectoderm.

Answer 8

chorda mesoderm, neural plate

Question 9

Origin of facial tissues

The ______ is thought to have a similar role in the anterior neural plate region. The nature of such inductive stimuli is presently unknown. Sometimes cell-to-cell contact appears to be necessary, whereas in other cases (as in ______) the inductive influences appear to be able to act between cells separated by considerable distances and consist of diffusible substances.

Answer 9

prechordal plate, neural plate induction

Question 10

Origin of facial tissues

It is known that inductive influences need only be present for a ______ time, after which the responding tissue is capable of independent development. For example, an induced neural plate isolated in culture will roll up into a tube, which then differentiates into the brain, spinal cord, and other structures.

Answer 10

short

Question 11

Origin of facial tissues

In addition to inducing neural plate formation, the ______ appears to be responsible for developing the organizational plan of the head.

Answer 11

chorda mesoderm

Question 12

Origin of facial tissues

As noted previously, the notochord and prechordal plates arise initially within the ______, from which they eventually separate.

Answer 12

endoderm

Question 13

Origin of facial tissues

The mesodermal portion differentiates into well-organized blocks of cells, called ______, caudal to the developing ear and less organized somitomeres rostral to the ear. Later these structures form ______ and some of the skeletal and connective tissues of the head. Besides inducing the neural plate from overlying ectoderm, the ______ organizes the positional relationships of various neural plate components, such as the ______ of the eye.

Answer 13

somites, myoblasts, chorda mesoderm, initial primordium

Question 14

Origin of facial tissues

A unique population of cells develops from the ______ along the lateral margins of the neural plate. These are the ______. They undergo extensive migrations, usually beginning at about the time of tube closure, and give rise to a variety of different cells that form components of many tissues.

Answer 14

ectoderm, neural crest cells

Question 15

Origin of facial tissues

The crest cells that migrate in the trunk region form mostly ______, ______, and ______ cells, whereas those that migrate in the head and neck also contribute extensively to ______ and ______ tissues (i.e., cartilage, bone, dentin, and dermis).

Answer 15

neural, endocrine, pigment, skeletal, connective

Question 16

Origin of facial tissues

In the trunk, all skeletal and connective tissues are formed by ______. Of the skeletal or connective tissue of the facial region, it appears that ______ is the only one not formed by crest cells.

Answer 16

mesoderm, tooth enamel

Question 17

Origin of facial tissues

The enamel-forming cells are derived from ______ lining the oral cavity.

Answer 17

ectoderm

Question 18

Origin of facial tissues

The migration routes that cephalic (head) neural crest cells follow are illustrated in Fig. 2.4. They move around the sides of the head beneath the surface ______, en masse, as a sheet of cells. They form all the ______ in the upper facial region, whereas in the lower facial region they surround ______ already present in the visceral arches.

Answer 18

ectoderm, mesenchyme, mesodermal cores

Question 19

Origin of facial tissues

The ______ region is then characterized by grooves (clefts and pouches) in the lateral pharyngeal wall ______ and ______ that approach each other and appear to effectively segment the ______ into a number of bars that become surrounded by ______.

Answer 19

pharyngeal, endoderm, ectoderm, mesoderm, crest mesenchyme

Question 20

Origin of facial tissues

Toward the completion of migration, the trailing edge of the crest cell mass appears to attach itself to the ______ at locations where sensory ganglia of the ______, ______, ______, and ______ cranial nerves will form.

Answer 20

neural tube, 5th, 7th, 9th, 10th

Question 21

Origin of facial tissues

In the trunk sensory ganglia, supporting (e.g., Schwann) cells and all neurons are derived from ______. On the other hand, many of the sensory neurons of the cranial sensory ganglia originate from placodes in the surface ______.

Answer 21

neural crest cells, ectoderm

Question 22

Origin of facial tissues

Eventually, ______ cells derived from ______ cells invade the crest cell mesenchyme, and it is from this mesenchyme that the supporting cells of the developing ______ are derived. Initially, these supporting cells include only ______, which are closely apposed to the outer surfaces of endothelial cells. Later, additional crest cells differentiate into the ______ and ______ cells that will form the ______. The developing blood vessels become interconnected to form vascular networks. These networks undergo a series of modifications, examples of which are given in Fig. 2.5, before they eventually form the mature ______. The underlying mechanisms are not clearly understood.

Answer 22

capillary endothelial, mesoderm, blood vessels, pericytes, fibroblasts, smooth muscle, vessel wall, vascular system

Question 23

Origin of facial tissues

Almost all the myoblasts that subsequently fuse with each other to form the multinucleated striated muscle fibers are derived from ______.

Answer 23

mesoderm

Question 24

Origin of facial tissues

The ______ that form the hypoglossal (tongue) muscles are derived from ______ located beside the developing ______.

Answer 24

myoblasts, somites, hindbrain

Question 25

Origin of facial tissues ______ are condensed masses of cells derived from mesoderm located adjacent to the neural tube.

Answer 25

Somites

Question 26

Origin of facial tissues The myoblasts of the extrinsic ocular muscles originate from the ______. They first migrate to poorly condensed blocks of mesoderm (______) located rostral to (in front of) the ______, from which they migrate to their final locations.

Answer 26

prechordal plate, somitomeres, otocyst

Question 27

Origin of facial tissues The supporting connective tissue found in facial muscles is derived from ______. Much of the development of the masticatory and other facial musculature is closely related to the final stages of ______ development and will be described later.

Answer 27

neural crest cells, visceral arch

Question 28

Origin of facial tissues A number of other structures in the facial region, such as the ______ components or glands and the ______ of the tooth bud, are derived from epithelium that grows (invaginates) into underlying mesenchyme. Again, the connective tissue components in these structures (e.g., fibroblasts, odontoblasts, and the cells of tooth- supporting tissues) are derived from ______.

Answer 28

epithelial, enamel organ, neural crest cells

Question 29

Development of facial prominences On the completion of the initial crest cell migration and the vascularization of the derived mesenchyme, a series of outgrowths or swellings termed “______” initiates the next stages of facial development.

Answer 29

facial prominences

Question 30

Development of facial prominences The growth and fusion of upper facial prominences produce the ______ and ______ palates.

Answer 30

primary, secondary

Question 31

Development of the frontonasal region: Olfactory placode, primary palate, and nose After the crest cells arrive in the future location of the upper face and midface, this area often is referred to as the ______. The first structures to become evident are the ______. These are thickenings of the ______ that appear to be derived at least partly from the anterior rim of the ______.

Answer 31

frontonasal region, olfactory placodes, ectoderm, neural plate

Question 32

Development of the frontonasal region: Olfactory placode, primary palate, and nose Experimental evidence indicates that the lateral edges of the placodes actively curl ______, which enhance the initial development of the ______ (LNP, sometimes called the ______. This morphogenetic movement combined with persisting high rates of cell proliferation rapidly brings the LNP ______ so that it catches up with the ______, which was situated in a more forward position at the beginning of its development. However, before that contact is made, the ______ has already grown forward from its origin at the proximal end of the first visceral arch to merge with the LNP and make early contact with the MNP.

Answer 32

forward, lateral nasal prominence, nasal wing), forward, medial nasal prominence (MNP), maxillary prominence (MxP)

Question 33

Development of the frontonasal region: Olfactory placode, primary palate, and nose With development of the LNP–MNP contact, all the three prominences contribute to the initial separation of the developing ______ and ______. This separation is usually called the ______. The combined right and left MxPs are sometimes called the ______.

Answer 33

oral cavity, nasal pit, primary palate, intermaxillary segment

Question 34

Development of the frontonasal region: Olfactory placode, primary palate, and nose The contacting epithelia form the ______. Before contact many of the surface epithelial (______) cells are ______, and the underlying ______ cells appear to actively participate in the contact phenomenon by forming processes that span the space between the contacting epithelia.

Answer 34

epithelial seam, peridermal, lost, basal epithelial

Question 35

Development of the frontonasal region: Olfactory placode, primary palate, and nose During the ______ week of human embryonic development, a portion of the ______ breaks down and the ______ of the three prominences becomes confluent.

Answer 35

5th, epithelial seam, mesenchyme

Question 36

Development of the frontonasal region: Olfactory placode, primary palate, and nose ______ accumulates between the cells of the persisting epithelium behind the point of epithelial breakdown. Eventually, these fluid-filled spaces coalesce to form the initial nasal passageway connecting the ______ with the roof of the ______.

Answer 36

Fluid, olfactory pit, primitive oral cavity

Question 37

Development of the frontonasal region: Olfactory placode, primary palate, and nose The tissue resulting from development and fusion of these prominences is termed the ______. It forms the roof of the anterior portion of the ______, as well as forming the initial separation between the ______ and ______ cavities. In later development, derivatives of the primary palate form portions of the upper ______, anterior ______, and upper ______.

Answer 37

primary palate, primitive oral cavity, oral, nasal, lip, maxilla, incisor teeth

Question 38

Development of the frontonasal region: Olfactory placode, primary palate, and nose The outlines of the developing external nose can be seen in Figure 2.8C. Although the nose is disproportionately large, the basic form is easily recognizable. Subsequent alterations in form lead to progressively more mature structure. Figure 2.8 is a schematic illustration of the contribution of various facial prominences to the development of the ______.

Answer 38

external face

Question 39

Development of maxillary prominences and secondary palate New outgrowths from the medial edges of the MxPs form the shelves of the ______. These palatal shelves grow ______ beside the tongue, at which time the tongue partially fills the ______.

Answer 39

secondary palate, downward, nasal cavities

Question 40

Development of maxillary prominences and secondary palate At about the ______ gestational week, the shelves elevate, make contact, and fuse with each other above the tongue. In the ______ region, the shelves are brought to the horizontal position by a rotational (hinge-like) movement. In the more ______ regions, the shelves appear to alter their position by changing shape (remodeling) as well as by rotation.

Answer 40

9th, anterior, posterior

Question 41

Development of maxillary prominences and secondary palate Available evidence indicates that the shelves are incapable of ______ until the tongue is first withdrawn from between them. Although the motivating force for shelf elevation is not clearly defined, contractile elements may be involved.

Answer 41

elevation

Question 42

Development of maxillary prominences and secondary palate Fusion of ______ requires alterations in the epithelium of the medial edges that begin prior to ______. These alterations consist of cessation of cell division, which appears to be mediated through distinct underlying biochemical pathways, including a rise in ______ levels. There is also loss of some surface ______ cells and production of extracellular surface substances, particularly ______, that appear to enhance adhesion between the shelf edges as well as between the shelves and inferior margin of the nasal septum.

Answer 42

palatal shelves, elevation, cyclic AMP, epithelial (peridermal), glycoproteins

Question 43

Development of maxillary prominences and secondary palate The ultimate fate of these remaining epithelial cells is controversial. Some of them appear to undergo ______ and eventually are ______, but recent studies indicate that many undergo direct transformation in ______ cells. The fate of cells in the epithelial seam of the primary palate described previously also is questionable. Some of the epithelial cells remain indefinitely in clusters (______) along the fusion line. Eventually, most of the hard palate and all of the soft palate form from the ______.

Answer 43

cell death, phagocytized, mesenchymal, cell rests, secondary palate

Question 44

Development of visceral arches and tongue The ______ develops as a result of inductive interactions between the ventral ______ and oral ______ and is derived in part from both tissues. Following initial crest cell migration, these cells invade the area of the developing pituitary gland and are continuous with cells that will later form the ______. Eventually, ______ form the connective tissue components of the gland.

Answer 44

pituitary gland, forebrain, ectoderm, MxP, crest cells

Question 45

Development of visceral arches and tongue In humans, there is a total of ______ visceral arches, of which the ______ is rudimentary. These arches are also known as ______ or ______ arches.

Answer 45

six, fifth, pharyngeal, branchial

Question 46

Development of visceral arches and tongue The proximal portion of the first (mandibular) arch becomes the ______.

Answer 46

MxP

Question 47

Development of visceral arches and tongue As the heart recedes caudally, the ______ and ______ arches develop further at their distal portions to become consolidated in the ______.

Answer 47

mandibular, hyoid, ventral midline

Question 48

Development of visceral arches and tongue As noted previously, the mesodermal core of each visceral arch is concerned primarily with the formation of ______. As noted below, these cells appear to be later replaced by cells that eventually form ______.

Answer 48

vascular endothelial cells, visceral arch myoblasts

Question 49

Development of visceral arches and tongue The ______ and ______ visceral arches undergo further developmental changes. As the heart recedes caudally, both arches send out ______ processes that merge with their opposite members in the ______.

Answer 49

first (mandibular), second (hyoid), bilateral, ventral midline

Question 50

Development of visceral arches and tongue Nerve fibers from the ______, ______, ______, and ______ cranial nerves extend into the ______ of the first ______ visceral arches.

Answer 50

5th, 7th, 9th, 10th, mesoderm, four

Question 51

Development of visceral arches and tongue The mesoderm of the definitive mandibular and hyoid arches gives rise to the ______ and ______ nerve musculature, while mesoderm associated with the less well-developed 3rd and 4th arches forms the ______ and ______ nerve musculature.

Answer 51

5th, 7th, 9th, 10th

Question 52

Development of visceral arches and tongue Recent studies show that ______ cells in the visceral arches actually originate from ______ more closely associated with the ______ (as do the cells that form the hypoglossal and extrinsic eye musculature; Fig. 2.6). They would then migrate into the visceral arches and replace the ______ cells that initiated blood vessel formation earlier. It therefore appears that myoblasts forming voluntary striated muscle fibers of the facial region would then originate from mesoderm adjacent to the ______.

Answer 52

myoblast, mesoderm, neural tube, mesodermal, neural tube

Question 53

Development of visceral arches and tongue Groups of visceral arch myoblasts that are destined to form individual muscles each take a branch of the appropriate visceral arch ______.

Answer 53

nerve

Question 54

Development of visceral arches and tongue Myoblasts from the second visceral arch, for example, take branches of the ______ cranial nerve and migrate very extensively throughout the head and neck to form the contractile components of the “______.”

Answer 54

seventh, muscles of facial expression

Question 55

Development of visceral arches and tongue Myoblasts from the first arch contribute mostly to the muscles of ______, while those from the third and fourth arches contribute to the ______ and ______ musculature. As noted earlier, connective tissue components of each muscle in the facial region are provided by ______ of crest origin.

Answer 55

mastication, pharyngeal, soft palate, mesenchymal cells

Question 56

Development of visceral arches and tongue The ______ of the visceral arches give rise to skeletal components such as the temporary visceral arch ______ (e.g., Meckel’s cartilage; Fig. 2.11), middle ear cartilages, and mandibular bones. Also visceral arch crest cells form connective tissues such as ______ and the connective tissue components of the ______.

Answer 56

crest mesenchymal cells, cartilages, dermis, tongue

Question 57

Development of visceral arches and tongue The ______ forms in the ventral floor of the pharynx after arrival of the hypoglossal muscle cells.

Answer 57

tongue

Question 58

Development of visceral arches and tongue The significance of the ______ and other swellings in the forming tongue has not been carefully documented.

Answer 58

lateral lingual tubercles

Question 59

Development of visceral arches and tongue It is known that the anterior two-thirds of the tongue is covered by ______ whereas ______ covers the posterior one-third.

Answer 59

ectoderm, endoderm

Question 60

Development of visceral arches and tongue The ______ forms by invagination of the most anterior endoderm (______).

Answer 60

thyroid gland, thyroglossal duct

Question 61

Development of visceral arches and tongue A residual pit (the ______; Fig. 2.14C) left in the epithelium at the site of invagination marks the junction between the anterior two-thirds and posterior one-third of the tongue, which are, respectively, covered by epithelia of ______ and ______ origin.

Answer 61

foramen cecum, ectodermal, endodermal

Question 62

Development of visceral arches and tongue It is also known that the connective tissue components of the anterior two-thirds of the tongue are derived from ______, whereas those of the posterior one-third appear to be primarily derived from the ______.

Answer 62

first-arch mesenchyme, third-arch mesenchyme

Question 63

Development of visceral arches and tongue The epithelial components of a number of glands are derived from the ______ lining of the ______. In addition to the ______, these include the ______ and ______. The epithelial components of the salivary and anterior pituitary glands are derived from ______.

Answer 63

endodermal, pharynx, thyroid, parathyroid, thymus, oral ectoderm

Question 64

Development of visceral arches and tongue Finally, a lateral extension from the inner groove between the first and second arch gives rise to the ______, which connects the pharynx with the ear. The ______ or ______ is formed at least partially from tissues of the ______ and ______ arches (day ______)

Answer 64

eustachian tube, external ear, pinna, first, second, 44