Controversial Latest Anatomy Question 2015-2016

Controversial Latest Anatomy Question 2015-2016

Q The intervillous space contains all of the following substances EXCEPT:

A. oxygen
B. carbon dioxide
C. maternal blood cells
D. fetal blood
E. electrolytes
D. is correct
Maternal blood cells find their way through the dark intervillous space with electrolytes, oxygen and other good things, and they carry away bad things like carbon dioxide and fetal waste products. However, fetal blood does not normally enter the intervillous space but is separated from it by the placental barrier.

Q The portion of the decidua which does not survive until the end of pregnancy is the:

A. capsularis
B. basalis
C. laeve
D. parietalis
E. frondosum
A. is correct
Chorion frondosum and the decidua basalis make up the placenta. Chorion laeve, or smooth chorion, is covered by decidua capsularis. As the fetus and chorion enlarge the chorion laeve pushes against the decidua parietalis and the capsularis disappears.

Q Which of the following is NOT a component of the mature placental barrier?

A. the endothelial lining of fetal capillaries
B. the cytotrophoblast
C. the syncytiotrophoblast
D. the basement membrane of fetal capillaries
E. all of the above are part of the mature placental barrier
B. is correct.
In the last half of pregnancy, the cytotrophoblast and extraembryonic mesoderm layers are lost from the placental barrier, leaving only syncytium, capillary basement membrane and capillary endothelium between maternal and fetal circulations.

Q Failure of the brain to grow may result in:

A. plagiocephaly
B. craniostenosis
C. acrocephaly
D. scaphocephaly
E. microcephaly
E. is correct.
If the brain does not grow, neither will the skull. This results in microcephaly. Premature closure of cranial sutures is called craniostenosis. Early sagittal suture fusion causes scaphocephaly or a long skull. Early coronal fusion causes acrocephaly or tower skull. Asymmetric fusions produce plagiocephaly.

Q Somitomeres, paraxial mesoderm cranial to the somites, give rise to much of the skeletal muscle in the head EXCEPT:

A. extrinsic muscles of the eye
B. temporalis tongue muscles
C. muscles of facial expression
D. muscles of mastication
B. is correct.
Somitomeres provide myotomal tissue for skeletal muscle development to the head. Muscles of somitomere origin include the extrinsic eye muscles, the muscles of facial expression and the muscles of mastication, of which temporalis is one. Tongue muscles and the muscles of the larynx are from somitic myotomes.

Q The sphenoid bone is derived from which portion of the embryonic skull?

A. cartilaginous neurocranium
B. membranous neurocranium
C. cartrilaginous viscerocranium
D. membranous viscerocranium
E. branchial cartilage
A. is correct.
The skull consists of two parts, the neurocranium, which forms the vault protecting the brain, and the viscerocranium, which forms the bones of the face. The base of the skull, of which sphenoid is part, develops from the cartilaginous neurocranium because it forms by endochondral ossification. Skull vault is membranous.

Q The notochord is replaced by the:

A. ependyma
B. nucleus pulposus
C. spinal canal
D. dorsal roots
E. spinal cord
B. is correct.
The notochord is the forerunner of the vertebral column. As it is replaced by the vertebral column, it degenerates. All that remains of the notochord in the adult is the nucleus pulposus in the intervertebral discs, surrounded by the sclerotome-derived annulus fibrosus.

Q The intraembryonic coelom located cranial to the oropharyngeal membrane becomes the:

A. oral cavity
B. cranial foregut
C. stomodeum
D. pericardial cavity
E. nasal cavity
D. is correct.
The cardiogenic region lies cranial to the prochordal plate and its descendant, the oropharyngeal membrane. The heart tubes form on the endoderm side of intraembryonic coelom in the cardiogenic region. Following the head and lateral body folding, heart and its portion of intraembryonic coelom called pericardial cavity lie in the chest.

Q The derivatives of the embryonic ventral mesentery include the following structures EXCEPT:

A. hepatoduodenal ligament
B. hepatogastric ligament
C. falciform ligament
D. ligamentum teres hepatis
E. lesser omentum
D. is correct.
The ligamentum teres hepatis is a remnant of the fetal umbilical vein. Although it is contained within the ventral mesentery, it is not a derivative of it.

Q The following peritoneal ligaments are derived wholly or in part from the embryonic dorsal mesogastrium EXCEPT:

A. hepatogastric ligament
B. splenorenal or lienorenal ligament
C. gastrosplenic or gastrolienal ligament
D. gastrocolic ligament
E. transverse mesocolon
A. is correct.
Splenorenal, gastrosplenic and gastrocolic ligaments are derived from the dorsal mesogastrium, while transverse mesocolon fuses with dorsal mesogastrium. The nepatogastric ligament, on the other hand, is derived from the ventral mesentery.

Q After folding of the head region, the structure lying just caudal to the pericardial cavity is the:

A. developing heart
B. connecting stalk
C. primitive streak
D. liver
E. septum transversum
E. is correct.
The septum transversum is the diaphragm’s earliest progenitor. After folding of the head region brings the heart and its coleom region ventrally, the septum transversum is the structure that lies immediately caudal to it. Liver is not a bad guess, but remember that the diaphragm lies between it and the thorax in the adult.