Embryology and Development Practice Questions

Q: The structure marked A in the image below gives rise to which of the following structures?

Falciform ligament. ***Falciform ligament*** - The structure marked 'A' represents the **ventral mesentery** in the embryonic stage, which connects the primitive gut tube to the anterior body wall. - The **falciform ligament** develops from the ventral mesentery, specifically in the region of the liver, and connects the liver to the anterior abdominal wall and diaphragm. *Gastrosplenic ligament* - This ligament is derived from the **dorsal mesentery**, not the ventral mesentery. - It connects the greater curvature of the stomach to the hilum of the spleen. *Lienorenal ligament* - Also derived from the **dorsal mesentery**, connecting the left kidney to the spleen. - This structure is not formed from the ventral mesentery which is indicated by 'A'. *Gastrophrenic ligament* - This ligament is part of the **dorsal mesentery** and connects the stomach to the diaphragm. - It is not a derivative of the ventral mesentery.

Q: Which of the following is a remnant of the Wolffian duct in females?

Gartner’s cyst. ***Gartner’s cyst*** - **Gartner's cysts** are remnants of the **Wolffian duct (mesonephric duct)** in females [3]. These ducts normally regress in females but can persist as vestigial structures [3]. - They typically present as cysts or small ducts along the lateral walls of the vagina or in the broad ligament [2], [3]. *Pouch of Douglas* - The **Pouch of Douglas (rectouterine pouch)** is a peritoneal recess located between the rectum and the uterus, not a remnant of the Wolffian duct [2]. - It is formed during development as the peritoneum drapes over the pelvic organs. *Uterovesical pouch* - The **uterovesical pouch** is a peritoneal reflection located between the uterus and the bladder, separate from the Wolffian duct remnants [1]. - Like the Pouch of Douglas, it is a normal anatomical space formed by the arrangement of the peritoneum in the pelvis. *Broad ligament* - The **broad ligament** is a wide fold of peritoneum that supports the uterus, fallopian tubes, and ovaries. It is not a remnant of the Wolffian duct itself, though Wolffian duct remnants (like Gartner's ducts) can sometimes be found within it [3]. - It serves as a mesentery for the reproductive organs, connecting them to the lateral walls of the pelvis.

Q: Which of the following statements about skin is false?

Both dermis & epidermis are derived from ectoderm. Both dermis & epidermis are derived from ectoderm - This statement is **FALSE** because the **epidermis is derived from the ectoderm**, but the **dermis is derived from the mesoderm**. - The ectoderm forms the outer layer of the embryo, giving rise to the epidermis, while the mesoderm forms the connective tissues, including the dermis. - This is the correct answer to this "false" question. [1] *Most of the cells in skin are keratinocytes derived from ectoderm* - This is **TRUE**. **Keratinocytes** constitute approximately **90% of the epidermal population**. - They are indeed derived from the **embryonic ectoderm**, which is the primary germ layer for the epidermis. [1] *Dermis is made up of type 1 and type 3 collagen in 4:1 ratio* - This is **TRUE**. The dermis is primarily composed of **collagen fibers**, with **Type I collagen** being the most abundant (80-90%). - **Type III collagen** is also present, and the ratio of **Type I to Type III collagen is approximately 4:1 to 5:1** in normal mature dermis. *Skin accounts for total of 15% of body weight* - This is **TRUE**. The skin is the **largest organ** of the body, and its weight typically constitutes around **15-20% of an adult's total body weight**. - This significant proportion reflects its extensive surface area and multiple essential functions. [1]

Q: Most common site for fertilization?

Ampulla. ***Ampulla*** - The **ampulla** of the **fallopian tube** is the widest and longest section, providing an ideal environment for the sperm and ovum to meet. - Fertilization most commonly occurs here, as it allows sufficient time for sperm capacitation and interaction with the egg. *Isthmus* - The **isthmus** is a narrow, thick-walled section of the fallopian tube, closer to the uterus. - While sperm may pass through here, it is not the primary site for fertilization. *Intramural* - The **intramural** (or interstitial) part is the segment of the fallopian tube that passes through the muscular wall of the uterus. - This narrowest part is not conducive to fertilization. *Fimbriae* - The **fimbriae** are finger-like projections at the end of the fallopian tube that capture the ovum after ovulation. - Their role is to direct the egg into the tube, not to be the site of fertilization.

Q: Nerves of the Branchial arches are derived from:

Neuroectoderm. ***Neuroectoderm*** - The **cranial nerves** (CN V, VII, IX, X) that supply the branchial arches are derived from **neuroectoderm**. - **Motor components** arise from motor nuclei in the brainstem (neural tube derivative). - **Sensory components** arise from sensory nuclei in the brainstem and from ectodermal placodes. - Neuroectoderm gives rise to the **neurons** that form the actual nerve fibers innervating branchial arch derivatives. *Neural crest* - While neural crest cells migrate extensively and are crucial to branchial arch development, they do **not** form the nerves themselves. - Neural crest contributes to **sensory and autonomic ganglia**, **Schwann cells**, and other supporting structures. - The actual **nerve fibers (axons)** of cranial nerves come from neuroectodermal neurons, not neural crest. *Mesoderm* - **Mesoderm** forms the muscles, cartilage, bones, and blood vessels of the branchial arches. - It does not contribute to the formation of the nervous tissue or nerves. *Endoderm* - **Endoderm** lines the pharyngeal pouches and forms glandular structures (thymus, parathyroid). - It has no role in nerve formation.

Q: Ureteric bud develops from:

Mesonephros. ***Mesonephros*** - The **ureteric bud** arises as an outgrowth of the **mesonephric duct** (Wolffian duct), which is the duct of the mesonephros. - The ureteric bud emerges from the **caudal portion of the mesonephric duct** near its entry into the cloaca around the 5th week of development. - It plays a crucial role in forming the **collecting system of the kidney**, including the ureter, renal pelvis, major and minor calyces, and collecting ducts. - **Note:** While technically the ureteric bud arises from the mesonephric duct (not the mesonephric tubules), "mesonephros" is accepted as the answer referring to the mesonephric duct system. *Metanephros* - The **metanephric mesoderm** (metanephric blastema) is induced by the ureteric bud to form the **definitive kidney**. - The metanephros forms the **nephrons** (from Bowman's capsule to distal convoluted tubule). - It does not give rise to the ureteric bud; rather, it interacts with it through **reciprocal induction**. *Pronephros* - The **pronephros** is the first, transient, and **non-functional** kidney structure in human embryonic development. - It appears in the **cervical region** around week 4 and completely **regresses** by week 5. - It does not contribute to the formation of the ureteric bud or the adult kidney. *Genital sinus* - The **urogenital sinus** is derived from the ventral part of the cloaca after division by the urorectal septum. - It gives rise to the **bladder**, parts of the urethra, and contributes to external genitalia. - It is not involved in the development of the ureteric bud or the kidney's collecting system.

Q: Which of the following muscles is derived from the first pharyngeal arch?

Masseter. ***Masseter*** - The **masseter** is one of the four **muscles of mastication** derived from the **first pharyngeal arch** mesoderm. - All muscles of mastication (masseter, temporalis, medial pterygoid, lateral pterygoid) develop from the first arch. - The masseter is innervated by the **masseteric nerve**, a branch of the **mandibular division of CN V (CN V3)**, which is the nerve of the first pharyngeal arch. *Stapedius* - The stapedius muscle is derived from the **second pharyngeal arch**, not the first. - It is the smallest skeletal muscle in the body and dampens sound vibrations in the middle ear. - Innervated by the **facial nerve (CN VII)**, which is the nerve of the second pharyngeal arch. *Stylopharyngeus* - The stylopharyngeus is derived from the **third pharyngeal arch**. - It elevates the pharynx and larynx during swallowing. - Innervated by the **glossopharyngeal nerve (CN IX)**, which is the nerve of the third pharyngeal arch. *Posterior belly of digastric* - The posterior belly of the digastric muscle is derived from the **second pharyngeal arch**. - It assists in depressing the mandible and elevating the hyoid bone. - Innervated by the **facial nerve (CN VII)**, the nerve of the second arch, distinguishing it from the anterior belly which is first arch.

Q: Number of stem villi at term in human placenta is?

240. ***240*** - At term, the **human placenta** contains numerous **stem villi** which branch extensively to form the villous tree. - The approximate number of **stem villi** at term is around **240**, contributing to the large surface area for maternal-fetal exchange. *60* - This number is significantly **lower** than the actual count of **stem villi** found in a mature, term placenta. - Such a low number would result in an **insufficient surface area** for effective nutrient and gas exchange. *120* - While higher than 60, this number is still **underestimated** for the quantity of **stem villi** present in a full-term human placenta. - A placenta with only 120 stem villi might not be able to adequately support a fetus at term. *480* - This number is an **overestimation** of the typical count of **stem villi** in a human placenta at term. - While villi are extensive, 480 stem villi represent a significantly higher number than usually observed.

Q: Which of the following statements about keratinocytes is true?

They are derived from the ectoderm.. ***They are derived from the ectoderm.*** - **Keratinocytes**, the predominant cell type in the epidermis, originate from the **ectodermal germ layer** during embryonic development. - The ectoderm gives rise to the nervous system, epidermis, and other external structures of the body. *Keratinocytes remain unchanged as they progress through the layers of the epidermis.* - Keratinocytes undergo significant **morphological and functional changes** as they migrate from the basal layer to the stratum corneum, a process called **keratinization** [1]. - These changes include the accumulation of **keratin filaments**, loss of organelles, and flattening of cells [1]. *Keratinocytes are only found in the basal and spinous layers of the epidermis.* - Keratinocytes are found in **all four to five layers** of the epidermis, from the deepest **stratum basale** to the most superficial **stratum corneum** [1]. - They are the primary cells that form the protective barrier of the skin. *Keratinocytes only differentiate in the stratum corneum layer.* - **Differentiation of keratinocytes** begins in the **stratum basale** (where they divide) and continues through the **stratum spinosum** and **stratum granulosum** as they mature and accumulate keratin [1]. - The stratum corneum primarily consists of **dead, fully differentiated keratinocytes** (corneocytes).

Q: Embryo gets implanted at what stage of development?

Blastocyst. Blastocyst - Implantation into the uterine wall occurs when the embryo has developed into a blastocyst, typically around day 6 post-fertilization [1]. - The blastocyst consists of an inner cell mass (which forms the embryo) and an outer layer called the trophoblast (which contributes to the placenta) [1]. Two cell stage - This stage occurs very early in development, usually within the first 24-30 hours after fertilization [1]. - At this point, the embryo is still in the fallopian tube and has not yet reached the uterus for implantation [1]. Four cell stage - The four-cell stage is also an early cleavage stage, occurring around 2 days post-fertilization [1]. - Like the two-cell stage, the embryo is still in transport through the fallopian tube and is not ready for implantation [1]. Morula - The morula is a solid ball of cells formed by cleavage, typically around day 3-4 post-fertilization [1]. - While it has moved closer to the uterus, it has not yet formed the distinct inner cell mass and trophoblast necessary for successful implantation [1].

Question 1

The structure marked A in the image below gives rise to which of the following structures?

Accepted Answer

Falciform ligament

Answer

Lienorenal ligament

Answer

Gastrophrenic ligament

Answer

Gastrosplenic ligament

Question 2

Which of the following is a remnant of the Wolffian duct in females?

Accepted Answer

Gartner’s cyst

Answer

Pouch of Douglas

Answer

Uterovesical pouch

Answer

Broad ligament

Question 3

Which of the following statements about skin is false?

Accepted Answer

Both dermis & epidermis are derived from ectoderm

Answer

Most of the cells in skin are keratinocytes derived from ectoderm

Answer

Dermis is made up of type 1 and type 3 collagen in 4:1 ratio

Answer

Skin accounts for total of 15% of body weight

Question 4

Most common site for fertilization?

Accepted Answer

Ampulla

Answer

Isthmus

Answer

Intramural

Answer

Fimbriae

Question 5

Nerves of the Branchial arches are derived from:

Accepted Answer

Neuroectoderm

Answer

Mesoderm

Answer

Endoderm

Answer

Neural crest

Question 6

Ureteric bud develops from:

Accepted Answer

Mesonephros

Answer

Metanephros

Answer

Pronephros

Answer

Genital sinus

Question 7

Which of the following muscles is derived from the first pharyngeal arch?

Accepted Answer

Masseter

Answer

Stapedius

Answer

Posterior belly of digastric

Answer

Stylopharyngeus

Question 8

Number of stem villi at term in human placenta is?

Accepted Answer

240

Answer

60

Answer

120

Answer

480

Question 9

Which of the following statements about keratinocytes is true?

Accepted Answer

They are derived from the ectoderm.

Answer

Keratinocytes remain unchanged as they progress through the layers of the epidermis.

Answer

Keratinocytes are only found in the basal and spinous layers of the epidermis.

Answer

Keratinocytes only differentiate in the stratum corneum layer.

Question 10

Embryo gets implanted at what stage of development?

Accepted Answer

Blastocyst

Answer

Two cell stage

Answer

Four cell stage

Answer

Morula

Embryology and Development — MCQs

Embryology and Development — MCQs

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