M1-Embryology

Question 1

1. The part of the sperm containing proteolytic enzymes to digest the zona pellucida is the:
   A. capacitor
   B. head
   C. corona
   D. acrosome
   E. cumulus

Answer 1

D. is correct.
The acrosome is the part of the sperm containing proteolytic enzymes to digest the zona pellucida. It is exposed by the process of capacitation. Then, under the influence of substances released by corona radiata cells, it releases its proteolytic enzymes and penetrates the oocyte.

Question 2

2. The ovulated mammalian oocyte is arrested at:
   A. prophase of meiosis I
   B. metaphase of meiosis I
   C. prophase of meiosis II
   D. metaphase of meiosis II
   E. none of the above

Answer 2

D. is correct.
The long arrest in meiosis occurs in the primary oocyte. These descendants of oogonia begin meiosis before birth and stop dividing during prophase of the first division. Years later, this first division is completed just prior to ovulation. Ovulated secondary oocytes then stop at metaphase II until fertilized.

Question 3

3. The seven-day blastocyst:
   A. has a single layer of trophoblast at the embryonic pole
   B. has an amniotic cavity
   C. is attached to the endometrial epithelium
   D. is surrounded by a degenerating zona pellucida
   E. is called the hypoblast

Answer 3

C. is correct.
The decidual reaction of the endometrium creates a nourishing environment for the conceptus a it buries itself by invasion of the uterine endometrial wall. Progesterone
produced by the corpus luteum stimulates glandular secretion in the endometrium during the secretory phase of menstruation or early pregnancy.

Question 4

4. Haploid nuclei that fuse at fertilization are called:
   A. homunculi
   B. mitotic figures
   C. centrioles
   D. nucleoli
   E. pronuclei

Answer 4

E. is correct.
After the sperm reaches the ovum, it deposits its genetic load, the male pronucleus, into the cytoplasm of the egg. After finally completing the meiotic division that had begun years before, the female pronucleus fuses with the male pronucleus to create the diploid nucleus of the zygote

Question 5

5. The first week of human development is characterized by formation of the:
   A. inner cell mass
   B. hypoblast
   C. trophoblast
   D. blastocyst
   E. all of the above

Answer 5

E. is correct.
At four days, the blastocyst cavity of blastocele forms within the morula. Trophoblast are outer cells of the blastocyst, while a knot of cells appears, protruding into the blastocele. This is the inner cell mass. Trophoblast becomes 2 layers: syncytiotrophoblast and cytotrophoblast. Inner cell mass becomes epiblast and hypoblast.

Question 6

6. During implantation, the blastocyst:
   A. implants in the endometrium
   B. usually attaches to endometrial epithelium at its embryonic pole
   C. usually implants in the posterior wall of the body of the uterus
   D. causes change in the endometrial tissues
   E. all of the above are correct

Answer 6

E. is correct.
Implantation occurs when the trophoblast cells at the embryonic pole secrete proteolytic enzymes that allow the blastocyst to penetrate the wall of the uterus, usually the posterior wall. The endometrial lining responds to implantation through the decidua reaction, by
which it becomes more succulent for nourishing the blastocyst.

Question 7

7. Capacitation of the sperm:
   A. is caused by the zona pellucida
   B. occurs in the male
   C. prevents polyspermy
   D. is essential for fertilization
   E. removes the head of the sperm

Answer 7

D. is correct.
Capacitation involves removing the glycoprotein coat and seminal plasma proteins from the head of the sperm, exposing the acrosome and allowing the acrosome reaction to occur. Capacitation occurs within the female genital tract, and without its occurrence, fertilization could not occur.

Question 8

8. The early stages of cleavage are characterized by:
   A. formation of a hollow ball of cells
   B. formation of the zona pellucida
   C. increase in the size of the cells in the zygote
   D. increase in the number of cells in the zygote
   E. none of the above

Answer 8

D. is correct.
The earliest stages of cleavage are marked by a series of mitotic divisions that increase the number of cells in the zygote without an increase in size. As the cleavage continues the zygote becomes a morula or a solid ball of 12-16 cells. A cavity forming within the morula transforms it into a blastocyst, at about day 4.

Question 9

9. The most common site for implantation in ectopic pregnancy is:
   A. internal os of the uterus
   B. mesentery
   C. ovary
   D. uterine tube
   E. other

Answer 9

D. is correct.
The most common site of ectopic implantation is the uterine tube. The growth of the embryo in this site usually causes rupture of the tube and severe hemorrhage in the mother. Abdominally, an ectopic pregnancy often occurs in the rectouterine pouch, an area between the uterus and the rectum.

Question 10

10. With the light microscope, the zona pellucida appears as a translucent membrane surrounding the:
    A. primary oocyte
    B. zygote
    C. morula
    D. very early blastocyst
    E. all of the above are correct

Answer 10

E. is correct.
The zona pellucida persists until early it the blastocyst stage. It dissolves during the blastocyst stage in order that implantation may occur.

Question 11

11. The amniotic cavity develops:
    A. on the tenth day
    B. within the outer cell mass
    C. within the inner cell mass near the cytotrophoblast
    D. in extraembryonic mesoderm
    E. none of the above

Answer 11

C. is correct.
The amniotic cavity begins to develop around the 8th day as a slit-like area within the epiblast near the cytotrophoblast. It usually has a thin strip of epiblast cells, called amnioblasts, between it and the cytotrophoblast.

Question 12

12. During the second week of development, the trophoblast differentiates into:
    A. syncytiotrophoblast
    B. ectoderm
    C. intraembryonic mesoderm
    D. yolk sac (secondary)

Answer 12

A. is correct.
The trophoblast gives rise to both the syncytiotrophoblast and the cytotrophoblast, as well as the extraembryonic mesoderm. The ectoderm is a derivative of the epiblast, and the secondary yolk sac comes from endoderm cells that line the exocoelomic cavity or the primitive yolk sac.

Question 13

13. The first two intraembryonic germ layers to differentiate are the:
    A. ectoderm and hypoblast
    B. epiblast and hypoblast.
    C. ectoderm and endoderm
    D. ectoderm and mesoderm

Answer 13

B. is correct.
The epiblast and hypoblast develop from the inner cell mass during the 2nd week (week of TWOs). During the 3rd week, the epiblast produces cells between itself and the hypoblast, called the mesoderm. Epiblast also replaces the hypoblast with endoderm cells. Epiblast then changes its name to ectoderm, completing the process of gastrulation.

Question 14

14. The blastocoele becomes the:
    A. amniotic cavity
    B. extraembryonic coelom
    C. primary yolk sac
    D. chorionic cavity
    E. secondary cavity

Answer 14

C. is correct.
Around the 9th day, cells from the hypoblast spread around the blastocoele, forming the exocoelomic or Heuser’s membrane. When the blastocoele is surrounded by this membrane, it is referred to as the primary yolk sac or exocoelomic cavity.

Question 15

15. The bilaminar germ disc:
    A. consists of epiblast and mesoblast
    B. is derived from the outer cells of the morula
    C. forms the embryo proper
    D. synthesizes human chorionic gonadotropin, HCG

Answer 15

C. is correct.
The bilaminar germ disc develops from the inner cells of the morula and inner cell mass of the blastocyst. It is composed to epiblast and hypoblast layers, and it is also called the embryoblast because it becomes the embryo. The outer cells of the morula and blastocyst, become cyto- and syncytiotrophoblast. The latter produces HCG.

Question 16

16. The primitive streak first appears at the beginning of the _____ week.
    A. first
    B. second
    C. third
    D. fourth
    E. fifth

Answer 16

C. is correct.
Gastrulation, the process of formation of the three germ layers, occurs during the third week. Epiblast cells form a thickening called the primitive streak, with a primitive knot or node located at its cranial end. Epiblast cells invaginate from this streak to form the mesoderm layer and to replace hypoblast with endoderm.

Question 17

17. Which of the following structures is believed to be a primary organizer or inducer during organogenesis?
    A. somites
    B. notochord
    C. metanephric blastema
    D. lens placode
    E. none of the above

Answer 17

B. is correct.
The notochord is thought to be an important structure in induction of nervous system development, axial skeleton development and other organogenic events.

Question 18

18. Cells from the primitive streak DO NOT become:
    A. endoderm
    B. intermediate mesoderm
    C. paraxial mesoderm
    D. lateral plate mesoderm
    E. amnioblasts

Answer 18

E. is correct.
All mesoderm is a derivative of the invaginating cells at the primitive streak. The invagination occurs at the beginning of the third week. It is interesting that endoderm cells are also derived from the epiblast during gastrulation, replacing the hypoblast.

Question 19

19. The primitive streak:
    A. is derived from the outer cells of the morula
    B. is formed during the second week in development
    C. persists as the cloacal membrane
    D. is the site of involution of epiblast cells to form mesoderm
    E. was done in a bathing suit, for those who remember streaking

Answer 19

D. is correct.
The primitive streak begins to form on the surface of the epiblast at the beginning of the third week (3=streak). It is at the primitive streak that epiblast cells invaginate to form the mesoderm, through the process of gastrulation.

Question 20

20. In the third week of human embryonic development:
    A. the amnion appears
    B. a bilaminar embryonic disc is formed
    C. the body stalk moves ventrally and joins with the yolk sac stalk to form the umbilical cord
    D. the neural plate is induced by the notochordal process and associated mesoderm
    E. the uteroplacental circulation is established

Answer 20

D. is correct.
It is during the third week that the nOtOchOrdal process (note: 3 O= week3) and its associated mesoderm induce the Neural Plate.
The hollow notochordal process eventually becomes the solid notochord, the forerunner of the axial skeleton.

Question 21

21. During development, the notochordal process:
    A. arises from involuting endodermal cells
    B. extends from the prochordal plate to the primitive node
    C. is involved in the induction of the primitive gut
    D. becomes the appendicular skeleton

Answer 21

B. is correct.
The notochordal process extends from the primitive node up to the prochordal plate. It develops into the notochord, around which the vertebral column forms.
The notochord is not endodermal, and does not induce the primitive gut. It persists in the adult only as the nucleus pulposus of the intervertebral discs.

Question 22

22. The following organs are derived from mesoderm EXCEPT:
    A. skeletal musculature
    B. musculature of blood vessels
    C. cardiac musculature
    D. suprarenal cortex
    E. suprarenal medulla

Answer 22

E. is correct.
The suprarenal or adrenal medulla is actually a part of the sympathetic nervous system.
Therefore, it is a derivative of neural crest cells, and neural crest cells are ectodermal in origin.
(Masculatur= mesoderm , medulla not contain (r) so ectodermal )

Question 23

23. Somites:
    A. differentiate into myotomes which give rise to skeletal muscle in trunk and limbs
    B. differentiate into sclerotomes which give rise to vertebrae
    C. arise from segmentation of the paraxial mesoderm
    D. differentiate into myotomes which give rise to skeletal muscle of the limbs
    E. all of the above are correct

Answer 23

E. is correct.
Somites differentiate into sclerotomes, myotomes and dermatomes. The sclerotomes give rise to the vertebrae. The myotomes give rise to skeletal muscle of the trunk and limbs.
The dermatomes give rise to the dermal skin component. The skeletal muscle of the face arises from the pharyngeal arches.

Question 24

24. Almost all of the internal organs are well laid down at _____ months.
    A. 1
    B. 2
    C. 3
    D. 4
    E. 5

Answer 24

B. is correct
By the end of the embryonic period at about two months of the development almost all of the internal organs are well established.
This is important, in that most malformations occur within the first two months, while the internal organs are being formed. The rest of the gestational period allows for growth and maturation.

Question 25

25. Which of the following structures does not turn under onto the ventral surface of the embryo during folding of the head?
    A. prochordal plate
    B. heart
    C. notochord
    D. pericardial cavity
    E. septum transversum

Answer 25

C. is correct.
The buccopharyngeal membrane, heart, pericardial cavity and septum transversum all end up as ventral structures in the embryo, whereas the notochord remains dorsal. Remember, though, that before the folding of the embryo, the heart begins its development extraembryonically in a region anterior to the prochordal plate.

Question 26

26. When the amount of amniotic fluid exceeds two liters, the condition is called:
    A. oligohydramnios
    B. polyhydramnios or hydramnios
    C. amniotitis
    D. bag of waters
    E. hydrogravida

Answer 26

B. is correct.
Polyhydramnios is a condition of excess amniotic fluid exceeding 1.5 liters. It is often caused by failure of the fetus to drink the normal amount of amniotic fluid, and may be due to anencephaly, esophageal atresia, or an upper GI tract blockage. Oligohydramnios, too little amniotic fluid, may indicate urinary problems.

Question 27

27. The wall of the chorionic sac is composed of:
    A. cytotrophoblast and syncytiotrophoblast
    B. two layers of trophoblast lined by extraembryonic somatic mesoderm
    C. trophoblast and exocoelomic membrane
    D. extraembryonic splanchnic mesoderm and both layers of trophoblast
    E. none of the above

Answer 27

B. is correct.
The outer layer of chorionic sac is the cytotrophoblast shell; the sac is lined with extraembryonic mesoderm of somatic type, because it does not contact the yolk sac; lining the intervillous space is syncytium. Later, the amniotic sac pushes up against and fuses to the chorionic sac, obliterating the chorionic cavity.

Question 28

28. The most distinctive characteristic of a primary chorionic villus is its:
    A. outer syncytiotrophoblastic layer
    B. cytotrophoblastic shell
    C. extraembryonic somatic mesodermal core
    D. bushy appearance
    E. cytotrophoblastic core

Answer 28

E. is correct.
All chorionic villi have outer layer of syncytiotrophoblast. The cytotrophoblast shell is a feature of the mature chorion. Extraembryonic somatic mesoderm forms the core of secondary villi, becoming tertiary with vascular development.
Primary villi, at 14 days, are syncytial processes with a core of cytotrophoblast.

Question 29

29. Chorionic villi are designated as secondary chorionic villi when they:
    A. contact the decidua basalis
    B. are covered by syncytiotrophoblast
    C. develop a mesenchymal core
    D. give rise to branch villi
    E. none of the above

Answer 29

C. is correct.
All chorionic villi have outer layer of syncytiotrophoblast. The cytotrophoblast shell is a feature of the mature chorion. Extraembryonic somatic mesoderm forms the core of secondary villi, becoming tertiary with vascular development.
Primary villi, at 14 days, are syncytial processes with a core of cytotrophoblast.

Question 30

30. When chorionic villi become vascularized they are called _____ villi.
    A. branch
    B. stem
    C. tertiary
    D. anchoring
    E. mature

Answer 30

C. is correct
As secondary chorionic villi become vascularized, they become known as tertiary villi.
Maturation of the villi involves thinning of the placental barrier, so that, only a thin layer of syncytium, extracellular matrix and endothelium separates maternal and fetal blood.

Question 31

31. The most important region of the decidua for the nourishment of the conceptus is the decidua ___________.
    A. frondosum
    B. capsularis
    C. parietalis
    D. basalis
    E. laeve

Answer 31

D. is correct.
The placenta is made of maternal tissue, the decidua basalis, the chorion frondosum or bushy/villous chorion and fetal tissue.
The smooth chorion or chorion laeve is covered by decidua capsularis, which disappears as the fetus grows and smooth chorion pushes up against the decidua parietalis.

Question 32

32. The intervillous space contains all of the following substances EXCEPT:
    A. oxygen
    B. carbon dioxide
    C. maternal blood cells
    D. fetal blood
    E. electrolytes

Answer 32

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.

Question 33

33. 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

Answer 33

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.

Question 34

34. 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

Answer 34

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.

Question 35

35. Failure of the brain to grow may result in:
    A. plagiocephaly
    B. craniostenosis
    C. acrocephaly
    D. scaphocephaly
    E. microcephaly

Answer 35

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.

Question 36

36. 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

Answer 36

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.

Question 37

37. 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

Answer 37

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.

Question 38

38. The notochord is replaced by the:
    A. ependyma
    B. nucleus pulposus
    C. spinal canal
    D. dorsal roots
    E. spinal cord

Answer 38

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.

Question 39

39. 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

Answer 39

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.

Question 40

40. 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

Answer 40

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.

Question 41

41. 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

Answer 41

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.

Question 42

42. 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

Answer 42

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.

Question 43

The heart is derived from:
A. splanchnic mesoderm
B. somatic mesoderm
C. septum transversum
D. intermediate mesoderm
E. paraxial mesoderm

Answer 43

A. is correct
The heart tubes form within the cardiogenic region cranial to the oropharyngeal membrane and beneath the intraembryonic coelom. If it is beneath the intraembryonic coelom, then it lies toward the yolk sac and must be splanchnic mesoderm. Somatic mesoderm would be the other side, or roof, of the intraembryonic coelom.

Question 44

The following are true statements with regard to the fetal circulation EXCEPT:
A. Since the fetal liver is a hemopoietic organ, it is large and well supplied with oxygenated blood.
B. Fetal brain receives relatively pure arterial blood.
C. Fetal and maternal blood vessels anastomose in the placenta
D. In early developmental stages, one pulmonary vein buds from the left atrium of the heart.
E. Foramen primum of the interatrial septum closes after the formation of the foramen secundum.

Answer 44

C. is correct.
In the placenta, there is no anastomosis between the maternal and fetal vessels. Maternal blood from the spiral arteries enters the cotyledons, where it bathes the villi from the fetus. This all occurs without anastomosis.

Question 45

Which duct is NOT associated with urinary system development?
A. ureteric bud
B. paramesonephric duct
C. Wolffian duct
D. pronephric duct
E. mesonephric duct

Answer 45

B. is correct.
The paramesonephric duct arises along the urogenital ridge, separate from the urinary system.
In the female, the paramesonephric duct develops into the uterine tubes, uterus and upper part of the vagina.

Question 46

The penile urethra is derived from the:
A. urogenital sinus
B. pelvic part of the vesicourethral canal
C. phallic part of the vesicourethral canal
D. cloaca
E. mesonephric duct

Answer 46

A. is correct.
The penile urethra, all but navicular portion, develops from the urogenital sinus. The urogenital sinus also produces the urinary bladder, prostate and bulbourethral glands.

Question 47

After the sinovaginal bulbs have proliferated and fused, they form a solid core of endodermal cells known as the:
A. sinus tubercle
B. prostatic utricle
C. vaginal plate
D. uterovaginal primordium
E. vault of the vagina

Answer 47

C. is correct.
The sinovaginal bulbs are evaginations from the urogenital sinus in the female. They proliferate, fuse, and form the vaginal plate, which then canalizes to form the lumen of vagina.

Question 48

The embryonic origin(s) of the labia minora is/are:
A. urethral folds
B. genital tubercle
C. genital swellings
D. sinovaginal bulbs
E. cloacal membrane

Answer 48

A. is correct.
The labia minora develop from the urethral or urogenital folds. In the male, the urethral folds ultimately fuse, forming the ventral aspect of the penis. The labia majora and the scrotum arise from the genital folds or swellings.

Question 49

The embryonic origin(s) of the penile urethra is/are:
A. urethral folds
B. genital tubercle
C. genital swellings
D. sinovaginal bulbs
E. cloacal membrane

Answer 49

A. is correct.
The labia minora develop from the urethral or urogenital folds. In the male, the urethral folds ultimately fuse, enclosing the penile or spongy urethra. However, the urethra passing through the glans is formed by canalization of the glandular plate.

Question 50

The embryonic origin(s) of the scrotum is/are:
A. urethral folds
B. genital tubercle
C. genital swellings
D. sinovaginal bulbs
E. cloacal membrane

Answer 50

C. is correct.
The scrotum in the male and the labia majora arise from the genital swellings or folds.
Cloacal membrane is subdivided into the urorectal membrane and anal membrane by the
urogenital septum. These membranes should rupture during the 9th week.

Question 51

The following structures are directly or indirectly derived from the mesonephric or
Wolffian duct EXCEPT:
A. part of the epididymis
B. part of the kidney
C. part of the urinary bladder
D. seminal vesicles
E. prostate

Answer 51

E. is correct.
The prostate is derived from the urogenital sinus, with no contribution from the mesonephric ducts. Ureteric bud, from mesonephric duct, gives rise to the collecting system of the kidney. A portion of the mesonephric ducts becomes incorporated into the trigone region of the bladder. Seminal vesicles bud from the mesonephric duct.

Question 52

The following structures are the derivatives of the primitive urogenital sinus EXCEPT:
A. most of the urinary bladder
B. male urethra
C. female urethra
D. lower vagina
E. ejaculatory ducts

Answer 52

E. is correct.
The ejaculatory ducts are derivatives of the mesonephric ducts.
All of the others have at least some contribution from the urogenital sinus.

Question 53

The derivatives of the Wolffian duct include each of the following except:
A. longitudinal duct of Gartner
B. round ligament of uterus
C. ductus deferens
D. duct of the epididymis
E. ejaculatory duct

Answer 53

B. is correct.
Gartners duct, like the appendix of the epididymis, holds more importance to National Board examiners than anyone else. It is a vestigial remnant of the mesonephric duct in the female. The round ligament of the uterus is derived from the gubernaculum, rather than the
mesonephric duct

Question 54

Of the following, the one most closely associated with the oviduct is:
A. mesonephric tubules
B. mesonephric duct
C. paramesonephric duct
D. genital swellings
E. urogenital sinus

Answer 54

C. is correct.
Paramesonephric ducts give rise to the oviducts or uterine tubes, uterus and upper portion of the vagina. In males, the prostatic utricle and the appendix of the testis are vestigial remnants of the paramesonephric ducts.

Question 55

Of the following, the one most closely associated with the efferent ducts of the testes is:
A. mesonephric tubules
B. mesonephric duct
C. paramesonephric duct
D. genital swellings
E. urogenital sinus

Answer 55

A. is correct.
The efferent ductules of the testes are the only functional derivatives of the mesonephric tubules.

Question 56

Of the following, the one most closely associated with the vestibule in the female is:
A. mesonephric tubules
B. mesonephric duct
C. paramesonephric duct
D. genital swellings
E. urogenital sinus

Answer 56

E. is correct.
In the male, the urogenital sinus gives rise to the urinary bladder, all but distal urethra, prostate and bulbourethral glands. In the female, it gives rise to the urinary bladder, urethra, lower part of vagina, vestibule, urethral and paraurethral glands and greater vestibular glands.

Question 57

Of the following, the one most closely associated with the urethra in the female is:
A. mesonephric tubules
B. mesonephric duct
C. paramesonephric duct
D. genital swellings
E. urogenital sinus

Answer 57

E. is correct.
In the male, the urogenital sinus gives rise to the urinary bladder, prostate, bulbourethral glands and all but distal urethral. In the female, it gives rise to the urinary bladder, urethra, lower part of vagina, vestibule, urethral and paraurethral glands and greater vestibular glands.

Question 58

Which of the following associations are correct?
A. renal pelvis - ureteric bud
B. ureter - ureteric bud
C. urethra - urogenital sinus
D. median umbilical ligament - urachus
E. all of the above are correct

Answer 58

E. is correct.
Ureteric bud gives rise to everything from collecting ducts through ureters. Derivatives of UG sinus include bladder and urethra of both sexes, prostate and bulbourethral glands, lower
vagina and urethral, paraurethral and vestibular lands. Allantois becomes urachus, which then becomes median umbilical ligament.

Question 59

The ureteric bud appears as an outgrowth from the:
A. metanephric mass
B. lateral plate mesoderm
C. urogenital sinus
D. allantoic duct
E. mesonephric duct

Answer 59

E. is correct.
The ureteric bud is an outgrowth of the mesonephric duct. It forms the ureter, renal pelvis,
calyces and collecting ducts

Question 60

The paramesonephric ducts in female embryos give rise to the:
A. uterine tubes and uterus
B. epoohoron
C. inferior fifth of the vagina
D. round ligament of the uterus
E. ovarian ligament

Answer 60

A. is correct.
The paramesonephric ducts in the female develop in the uterine tubes, the uterus and the
upper 1/3 of the vagina. The epoophoron come fromthr mesonephric tubules. The lower portion of the vagina develops from the urogenital sinus. The round ligament and the ovarian ligament are from the gubernaculum.

Question 61

Which of the following gives rise to the labia majora?
A. genital folds
B. genital swellings
C. genital tubercle
D. urorectal gold
E. inguinal fold

Answer 61

B. is correct.
Labia majora arise from the genital swellings. Their counterpart in the male is the scrotum,
which also arises from the genital swellings. The genital tubercle forms the distal end of penis and most of clitoris.

Question 62

The optic nerve is derived from what embryonic tissue?
A. neural crest
B. head mesenchyme
C. endoderm
D. mesoderm
E. ectoderm

Answer 62

E. is correct.
The optic nerve is derived from nervous tissue, therefore ectoderm, but not neural crest.
Optic sulci of the neural folds forming the forebrain send out the optic vesicles, which then
develop into the optic cups connected to forebrain by the optic stalk. The optic stalk becomes the optic nerve.

Question 63

Neural crest cells differentiate into:
A. postganglionic sympathetic cell bodies
B. cells of the inferior mesenteric ganglion
C. adrenal medullary cells
D. cells of the enteric plexus
E. all of the above are correct

Answer 63

E. is correct.
Neural crest cells give rise to the peripheral parts of the autonomic nervous system, which
includes all sympathetic and parasympathetic ganglia. Neural crest cells form all sensory
ganglia of the peripheral nervous system. Neural crest cells also populate the adrenal medulla.

Question 64

Of the following, the item most closely associated with the regulation of visceral and endocrine functions is:
A. telencephalon
B. diencephalon
C. mesencephalon
D. metencephalon
E. myelencehalon

Answer 64

B. is correct.
The hypothalamus of the diencephalon is the control center for visceral and endocrine functions

Question 65

Of the following, the item most closely associated with the pons is:
A. telencephalon
B. diencephalon
C. mesencephalon
D. metencephalon
E. myelencephalon

Answer 65

D. is correct.
The metencephalon differentiates into the cerebellum, the coordination center for posture
and movement and the pons, which serves as a neural relay center.

Question 66

Of the following, the one most closely associated with the cerebrum is:
A. telencephalon
B. diencephalon
C. mesencephalon
D. metencephalon
E. myelencephalon

Answer 66

A. is correct.
The cerebrum arises from the telencephalon. Telencephalon, the most rostral part of the brain vesicles, develops from the prosencephalon as lateral outgrowths, the cerebral hemispheres and an intermediate area, the lamina terminalis. Lamina terminalis develops into the commissures connecting the hemispheres.

Question 67

Of the following, the one most closely associated with the 3rd ventricle is:
A. telencephalon
B. diencephalon
C. mesencephalon
D. metencephalon
E. myelencephalon

Answer 67

B. is correct.
The 3rd ventricle lies within the thalamic area in the diencephalon. The lateral ventricles are cavities of the forebrain cerebral vesicles, from telencephalon. The 4th ventricle lies within the metencephalon.

Question 68

Cerebrospinal fluid:
A. is produced in choroid plexuses
B. circulates in the ventricular system of the brain and in the subarachnoid spaces
C. re-enters the venous blood at the arachnoid
D. granulations
E. blockage of its circulation can lead to internal or external hydrocephalus
F. all of the above are correct

Answer 68

E. is correct.

Cerebrospinal fluid is produced by ependymal cells of the choroid plexus.

It circulates within the ventricles of the brain, the central canal of the spinal cord and the subarachnoid space.

It is resorbed into the venous system via arachnoid granulations.

If flow is blocked, CSF accumulates and creates hydrocephalus.

Question 69

In the development of the nervous system:
A. there are five primary brain vesicles.
B. during the 5th week, each brain vesicle subdivides into 2 parts
C. the pontine flexure is in a direction opposite the mesencephalic and cervical flexure
D. neural epithelial cells are found in the marginal layer

Answer 69

C. is correct.
There are initially 3 brain vesicles: prosencephalon, mesencephalon and rhombencephalon.
The pros- and rhombencephalon divide into 2 parts. The pontine flexure is opposite to the mesencephalic and cervical flexures. The marginal layer contains the nerve fibers arising from the neuroblasts.

Question 70

In the development of the nervous system:
A. the sulcus limitans is found in the diencephalon
B. the infundibulum is an outgrowth of the telencephalon that develops into the neurohypophysis
C. sensory nuclei in the hindbrain lie ventral to the sulcus limitans
D. the inner ear is derived from surface ectoderm

Answer 70

D. is correct.
The sulcus limitans is a lateral, longitudinal groove dividing basal and alar plates. The infundibulum is an outpouching of the hypothalamic region that becomes neurohypophysis. Sensory nuclei lie dorsal to the sulcus limitans. Internal ear is from thickened surface ectoderm (otic placode) near rhombencephalon.

Question 71

In the development of the nervous system:
A. the neural groove forms from the neural plate
B. the neural folds are composed of neuroepithelial cells
C. the neural tube maintains temporary contact with the amniotic cavity via neuropores
D. neuroepithelial cells give rise to both neuroblasts and glia blasts
E. all of the above are correct

Answer 71

E. is correct.
The neural groove forms the neural plate when lateral parts of the plate elevate to form neural folds. Neural folds are composed of neuroepithelium which gives rise to neuroblasts, gliablasts and ependymal cells. After the neural tube forms, it maintains contact with the amniotic cavity via cranial and caudal neuropores.

Question 72

Congenital absence of neural crest cells could result in:
A. absence of sympathetic chain ganglia
B. facial malformations
C. absence of adrenal medulla
D. absence of pigment cells
E. all of the above are correct

Answer 72

E. is correct.
Neural crest cells form all sensory and autonomic ganglia, Schwann cells, meninges of the brain and spinal cord, adrenal medulla, pigment cells of the skin and connective tissues of the head and neck, including odontoblasts for dentin of the teeth.

Question 73

The brain flexure which develops between the metencephalon and the myelencephalon is called the:
A. pontine
B. hindbrain
C. cervical
D. cephalic
E. midbrain

Answer 73

A. is correct.
The pontine flexure occurs between the metencephalon, which forms the pons and
cerebellum, and the myelencephalon, which forms the medulla. The two other flexures, the cephalic and the cervical, flex in a direction opposite that of the pontine.

Question 74

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

Answer 74

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.