DH220 Embryology Exam #4 Ch. 1-5

What are the eight regions of the face?

Frontal, orbital, nasal, infraorbital, zygomatic, buccal, oral, mental regions

Where does the zygomatic arch extend?

From just below the lateral margin of the eye toward the middle part of the external ear

What joint is located just inferior to the zygomatic arch and anterior to the external ear?

TMJ

What makes up the buccal region of the face?

Soft tissues of the cheek

Which strong cheek muscle can enlarge due to bruxism or clenching?

Masseter muscle

Where is the parotid salivary gland located?

From the zygomatic arch inferiorly to the posterior border of the lower jaw

What junction separates the lips from surrounding skin at the vermilion border?

Mucocutaneous junction

What is the vertical groove extending from the nasal septum down the middle of the upper lip?

Philtrum

What is the thicker area at the end of the philtrum called?

Tubercle of the upper lip

Which muscle divides each side of the neck into anterior and posterior cervical triangles?

Sternocleidomastoid muscle

What structure protects the opening of the parotid duct opposite the maxillary second molar?

Parotid papilla

Where does the labial or buccal mucosa meet the alveolar mucosa?

Mucobuccal fold

What are the small yellowish elevations caused by misplaced sebaceous glands in oral mucosa?

Fordyce spots

What is the horizontal white ridge of calloused tissue on the buccal mucosa at the occlusal plane?

Linea alba

What attaches teeth to the bony surfaces of their alveoli?

Periodontal ligament or PDL

What tissue forms the outermost layer of a tooth root?

Cementum

What junction separates attached gingiva from alveolar mucosa?

Mucogingival junction

What is the midline ridge extending from the incisive papilla to the uvula?

Median palatine raphe

What inverted V-shaped groove separates the body and base of the tongue?

Sulcus terminalis

Which part of the pharynx lies above the soft palate and connects with the nasal cavity?

Nasopharynx

What are the three periods of prenatal development?

Preimplantation during week 1 followed by embryonic during weeks 2 through 8 and fetal from week 9 to birth

What are environmental factors that cause changes in a developing embryo called?

Teratogens

How many chromosomes does each sperm and ovum contain after meiosis?

23 chromosomes

What is another name for trisomy 21?

Down syndrome

What process divides the zygote into smaller and more numerous cells during the first week?

Mitosis

What solid ball of cells develops into the hollow blastocyst?

Morula

What outer blastocyst layer supports development and helps form the placenta?

Trophoblast

Where does the blastocyst implant at the end of the first week?

Endometrium of the uterus

What two layers make up the bilaminar embryonic disc?

Superior epiblast of high columnar cells and inferior hypoblast of small cuboidal cells

What prenatal organ connects the pregnant female with the developing embryo during the second week?

Placenta

What is the first physiological process of prenatal development in which one group of cells acts on another?

Induction

What type of growth adds layers to the outside of a structure?

Appositional growth

What is the development of a specific tissue structure or shape called?

Morphogenesis

What structure forms during the third week and establishes bilateral symmetry?

Primitive streak

What three layers make up the trilaminar embryonic disc?

Ectoderm and mesoderm and endoderm

What structures develop from the ectoderm?

Epidermis and hair and nails and nervous system and dental enamel

What membrane forms at the cephalic end of the trilaminar disc and leads to the primitive mouth?

Oropharyngeal membrane

What forms when the neural folds meet above the neural groove and later develops into the spinal cord?

Neural tube

What cells migrate from the neural folds and are considered a fourth embryonic cell layer?

Neural crest cells

How many pairs of somites form during the third week?

38 pairs

What process transforms the flat embryonic disc into a tubular embryo during the fourth week?

Embryonic folding

What developmental disorder may cause partial or complete anodontia?

Ectodermal dysplasia

Failure of neural crest cells to migrate to the facial region can cause what syndrome?

Treacher Collins syndrome

What dental abnormalities are associated with congenital syphilis caused by Treponema pallidum?

Hutchinson incisors and mulberry molars

In which sex cell do the final stages of meiosis occur?

Ovum

What chromosome combination produces a female embryo?

Two X chromosomes

Which inner blastocyst layer becomes the embryo proper?

Embryoblast

Between which two cavities is the bilaminar embryonic disc suspended?

Amniotic cavity facing the epiblast and yolk sac facing the hypoblast

What type of growth occurs from deep within tissues such as skin and gingiva?

Interstitial growth

What is the development of different histologic tissue types within a structure called?

Histodifferentiation

What prenatal procedure can detect chromosomal abnormalities?

Amniocentesis

What embryonic tissue develops from epiblast cells migrating toward the hypoblast and can form connective tissues?

Mesenchyme

What membrane forms at the caudal end of the embryonic disc and eventually becomes the anus?

Cloacal membrane

What structure forms when neuroectoderm thickens and invaginates during the third week?

Neural groove

During which week of prenatal development does facial development begin?

Fourth week

During which week is facial development completed?

Tenth week

What does the primitive mouth become at the beginning of the fourth week?

Stomodeum

What is the first event in facial development?

Disintegration of the oropharyngeal membrane

What arch forms when the paired mandibular processes fuse at the midline?

Mandibular arch or first pharyngeal arch

What cartilage develops within each side of the mandibular arch?

Meckel's cartilage

What are rounded areas of thickened ectoderm associated with developing special sense organs?

Placodes

What swelling over the developing brain forms the future forehead?

Frontonasal process

What paired processes fuse to form the middle of the nose and upper lip and philtrum?

Median nasal processes

What crescent-shaped swellings are located on the outer sides of the nasal pits?

Lateral nasal processes

What structure forms when the paired medial nasal processes fuse internally and grow downward?

Intermaxillary segment

What process forms from increased growth of the swelling on each side of the stomodeum?

Maxillary process

What fusion forms the upper lip?

Fusion of each maxillary process with each medial nasal process

What structures form when the maxillary processes partially fuse with the mandibular arch?

Labial commissures

Failure of fusion between the maxillary and medial nasal processes causes what condition?

Cleft lip

In which sex is cleft lip more common?

Males

How many major processes become centers of facial growth?

Five

What event marks the end of major growth of the lower two-thirds of the face?

Eruption of the permanent third molars

During which prenatal period do the paranasal sinuses develop?

Fetal period

What structures make up the branchial apparatus?

Branchial arches and branchial grooves and membranes and pharyngeal pouches

What cartilage is found in the second branchial or hyoid arch?

Reichert's cartilage

Which cranial nerve innervates muscles derived from the hyoid arch?

Seventh cranial nerve or facial nerve

Which pharyngeal pouches give rise to palatine tonsillar tissue?

Second pharyngeal pouches

What cyst may develop when the second branchial groove is not obliterated?

Cervical lymphoepithelial cyst or branchial cleft cyst

What does the stomodeum eventually become?

Oral cavity

What placodes migrate medially to form the future eyes?

Lens placodes

What placodes form pits that develop into the internal ear?

Otic placodes

How does the bony mandible develop in relation to Meckel's cartilage?

By intramembranous ossification lateral to the cartilage as most of the cartilage disappears

Which cranial nerve supplies the first branchial arch and muscles of mastication?

Fifth cranial nerve or trigeminal nerve

What structures develop from Reichert's cartilage?

Stapes and styloid process of the temporal bone and parts of the hyoid bone

What structures arise from the first branchial groove?

External auditory meatus and auditory tube and tympanic membrane

What develop from the third and fourth pharyngeal pouches?

Parathyroid glands and thymus

By the end of which week is fusion of the upper lip completed?

Sixth week

When does palatal development begin and end?

Begins during the fifth week and is completed during the twelfth week

What fusion creates the intermaxillary segment?

Internal fusion of the two medial nasal processes

What palate develops from the intermaxillary segment?

Primary palate

What part of the hard palate develops from the primary palate?

Premaxilla or anterior one-third

Which teeth are contained within the primary palate?

Maxillary anterior incisors

What structures arise from the bilateral maxillary processes during the sixth week?

Two lateral palatine processes or palatal shelves

What change allows the palatal shelves to fuse with the primary palate?

A change in tongue position

What structures develop from the secondary palate?

Posterior two-thirds of the hard palate and soft palate and uvula

In what direction do the primary and secondary palates fuse?

Anterior to posterior

What mucosal structure marks the line of fusion of the palatal shelves?

Median palatine suture

What opening beneath the incisive papilla represents the paired nasopalatine canals?

Incisive foramen

What is the least complicated form of cleft palate?

Cleft uvula

In which sex is isolated cleft palate more common?

Females