Chapter 04: Organogenetic Period: The Fourth to Eighth Weeks

Chapter 04: Organogenetic Period: The Fourth to Eighth Weeks

Complete Chapter Questions With Answers

Sample Questions Are Posted Below

MULTIPLE CHOICE

Directions: Each group of questions below consists of a numbered list of descriptive words or phrases accompanied by a diagram with certain parts indicated by letters or by a list of lettered headings. For each numbered word or phrase, select the letter or heading that matches it correctly. Then insert the letter in the space to the right of the appropriate number. Sometimes more than one numbered word or phrase may be correctly matched to the same lettered part or heading.

________ Hyoid arch

ANS:   D

The second or hyoid pharyngeal arch is recognizable early in the fourth week. As its name implies, this arch gives rise to part of the hyoid bone. Mesenchyme in this arch also gives rise to the muscles of facial expression and to various skeletal structures.

________ Gives rise to the mandible

ANS:   C

The mandibular prominences of the first pair of pharyngeal arches give rise to the lower jaw or mandible. Rostral extensions of the first arch—maxillary prominences—give rise to the upper jaw or maxilla.

________ Forms from the paraxial mesoderm

ANS:   E

The somites form by differentiation and division of longitudinal columns of paraxial mesoderm into cubical segments. The somites give rise to most of the axial skeleton, the associated musculature, and the dermis of the skin.

________ Neuropore

ANS:   B

The caudal neuropore is indicated. The neuropores (rostral and caudal) normally close by the end of the fourth week. The rostral neuropore closes on day 25 or 26, and the caudal neuropore usually closes about 2 days later. Defective closure of the caudal neuropore gives rise to a severe anomaly—spina bifida.