3rd Semester Embryology Past Paper PDF

## ANA 331 ### Multiple Choice Questions 1. If the distal part of the thyroid duct persisted, this will lead to the formation of: - A. elevator glandulae thyroidae. - B. abnormally fibrosed duct. - C. pyramidal lobe. 2. Which of the following muscles are derived from the first brac...

## ANA 331 ### Multiple Choice Questions 1. If the distal part of the thyroid duct persisted, this will lead to the formation of: - A. elevator glandulae thyroidae. - B. abnormally fibrosed duct. - C. pyramidal lobe. 2. Which of the following muscles are derived from the first brachial arch: - A. The muscles of mastication. - B. The muscles of mastication and anterior belly of digastric. - C. The muscles of mastication, and anterior and posterior bellies of digastric. - D. The muscles of mastication, anterior and posterior bellies of digastric, and geniohyoid. 3. Pharyngeal muscles are innervated by the glossopharyngeal nerve because it develops from: - A. 1st pharyngeal arch. - B. 2nd pharyngeal arch. - C. 3rd pharyngeal arch. - D. 4th pharyngeal arch. 4. The metanephros gives rise to: - A. Bowman's capsule & Convoluted tubules. - B. Collecting tubules. - C. Balloffibraebore. - D. All of the above. - E. All but E. 5. The permanent mesonephric duct is part of this structure(s): - A. Metanephros. - B. Mesonephros. - C. Metanephros and mesonephric duct. - D. All of the above. 6. At what week do mesenchymal cells migrate and differentiate into osteoblasts? - A. 4th week - B. 8th week - C. 12th week - D. 4th week 7. Skeletal system develops from: - A. Ossification. - B. Mesenchyme. - C. Ectoderma. - D. Endoderma. 8. As the bladder forms, the allantois atrophies and is seen in postnatal life as a - A. fibrous band. 9. The anomaly resulting from the failure of mesenchymal cells to migrate between the ectoderm of the abdomen and cloaca during the fourth week is known as: - A. ectopia of the cordomis. 10. _. and _ merge to form the upper lips. 11. The primary palate is formed by fusion of _. 12. A cleft lip is the result of the defective fusion of _. 13. _ percent of cleft lip cases are unilateral, and _ bilateral. 14. On the lateral wall of the developing nose appears an elevation called: - A. _. 15. Orofacial development begins at week _. 16. Upper lip formation occurs from week _ to week _ , and. 17. The primary manifestation of cleft palate is: - A. _. 18. Displacement of the ear and absence of cheeks result in a condition called: - A. _. 19. Olfactory epithelium is formed from: - A. _. 20. The spinal cord is developed from the _. part of the neural tube. 21. The midline layer of the spinal cord is divided by a groove called _. 22. The suprarenal gland develops from two components _ and _. 23. Autonomic nervous system is composed of _ that innervate _ and _ . 24. Parasympathetic ANS are most often referred to as _. 25. The budding that differentiates into the reproductive gonads develops from: - A. _ 26. In the female, the parasympathetic ducts give origin to the _. 27. With the formation of the urogenital septum, the cloacal membrane becomes divided into a _. membrane and a _. membrane. 28. In the development of the ovary, the cell masses from the primordial sex cords surround the primordial germ cell to form a _. ### True/False Statements 29. Metanephric blastema arises as an outgrowth from the caudal part of the mesonephric duct close to its entrance to the cloaca. 30. The prostatic urethra extends from the urinary bladder up to the openings of the ejaculatory duct and part of the pelvic part of the urogenital sinus. 31. Palatine tonsil and supratonsillar fossa develop from the 2nd and 3rd endodermal pouch. 32. The clitoris is formed from the genital tubercle. 33. The ribs are derived from the lateral extensions of the sclerotome mesenchyme. 34. Hindlimb buds appears at about the 28th day of development. 35. The vertebral column forms from the _ portion. 36. The uterine tubes develop from the _ parts of the paramesonephric ducts. 37. In the descent of the testes, they reach the scrotum by the end of the _ month. 38. Primordial germ cells form some spermatozoa and ova in the human body during development. 39. Paramesonephric ducts are the most important in the development of the _ genital system. 40. The mesonephric tubules anastomose with one another to form the _. ## ESSAY 1. Write on the development of the tongue and list 4 anomalies. 2. Describe the development of the upper lip. 3. Write briefly on the formation of the primitive palate. 4. Write on the development of the testis and list 3 anomalies. 5. Write on the development of the brain and spinal cord. ## Answers ### Multiple Choice 1. C 2. C 3. C 4. A 5. B 6. B 7. B ### Fill-In-The-Blanks 8. Urachus 9. Ectopic vesicae 10. Frontonasal process and maxillary process. 11. Primitive palate (frontonasal process) and palatal process (maxillary process). 12. Medial nasal and maxillary processes. 13. 80% unilateral, 20% bilateral. 14. Nasal conchae 15. هفته 4 16. هفته 4 & 7 17. Bifid uvula. 18. Mandibulofial dysostosis or first arch syndrome (Treacher Collins Syndrome). 19. Olfactory placodes 20. caudal 21. Sulcus limitans 22. Neural crest cells (medulla) and intermediate mesoderm (cortex) 23. Craniosacral system 24. Intermediate mesoderm 25. Uterus and part of the vagina 26. Ventral urogenital and caudal anal 27. Primordial follicle 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. ### True/False 29. True 30. True 31. True 32. True 33. True 34. True 35. Sclerotome ## Essay Answers 1. The tongue is the most mobile organ in the oral cavity that helps with chewing, tasting, and swallowing. The development of the tongue begins in the fourth week of gestation. First, two lateral lingual swellings develop on each side of the tongue. These swellings are derived from the first arch. Then, a median tongue bud grows from the midline and two tuberculum impar develop from the medial aspect of the first arch. Eventually, the two tuberculum impar fuse to form the apex of the tongue, and the lateral lingual swellings grow up and around to cover the inferior surface of the tongue. The posterior part of the tongue arises from the second and third arches. The most common anomalies affecting the tongue include: - **Cleft tongue:** A cleft tongue is a rare congenital anomaly that affects the tongue's development. It is a condition in which there is a separation or gap in the tongue. - **Ankyloglossia:** Ankyloglossia is a condition in which the lingual frenulum is too short or too tight, resulting in a restricted movement of the tongue. - **Macroglossia:** Macroglossia is a condition in which the tongue is abnormally large. This can be caused by various factors, including genetic syndromes, tumors, and a buildup of fluid in the tongue. - **Microglossia:** Microglossia is a condition in which the tongue is abnormally small. It is a rare condition that can be caused by genetic syndromes or injury. - **Bifid tongue:** Bifid tongue is a rare condition in which the tongue appears to be split or have a fork-shaped structure. 2. The development of the upper lip is a complex process that begins during the fourth week of gestation. Firstly, the frontonasal process, which forms the top of the nose, and the maxillary processes each give rise to two separate facial swellings on the ventral side. Then, the maxillary process, which is a bilateral structure, surrounds the primitive mouth and grows towards the midline. The medial nasal process forms the septum and the philtrum. During the fifth and sixth weeks, the medial nasal processes fuse with the maxillary processes. This fusion results in the formation of the upper lip, while the philtrum is formed from the two medial nasal processes. If this fusion does not happen properly, it can result in cleft lip, a condition where there is a gap in the upper lip. Cleft lip is more common than cleft palate and occurs in about 1 in 750 newborns. 3. The primitive palate forms in the fifth and sixth weeks of gestation. It is formed by the fusion of three structures: the medial nasal processes, the maxillary processes, and the palatal shelves. The medial nasal processes fuse together to form the primary palate, which makes up the anterior portion of the hard palate. The palatal shelves, which are extensions of the maxillary processes, grow downward and fuse together to form the secondary palate, which forms the posterior part of the hard palate. If the fusion of these processes does not happen properly, it can result in cleft palate, which can affect either the hard or soft palate. 4. The testes develop from the mesonephric ridge. In the early stages of fetal development, the mesonephric ridge, which is located in the urogenital region, gives rise to two primordial structures: the mesonephros and the metanephros. The mesonephros is a temporary kidney structure that regresses during gestation. The metanephros develops into the permanent kidney. The mesonephric ridge also gives rise to the male gonad, the testes. The development of the testes is a complex and multi-step process. The primordial germ cells, which are the precursors to sperm cells, migrate from the yolk sac to the mesonephric ridge. Once in the mesonephric ridge, the primordial germ cells proliferate and differentiate into spermatogonia. The seminiferous tubules, which are the structures where sperm are produced, develop from the mesonephric tubules. The Leydig cells, which produce testosterone, develop in the interstitial tissue of the testes. The development of the testes is regulated by a number of hormonal influences, most notably by testosterone. While testosterone is key to the development of the testes, several other factors contribute to its successful development. These include: - **Genetic factors:** The Y chromosome contains the SRY gene, which is crucial for triggering the development of testes. - **Endocrine factors:** Hormones like testosterone and FSH (follicle-stimulating hormone) are essential for regulating testis development and sperm production. - **Environmental factors:** Environmental factors like temperature and exposure to certain chemicals can also influence the development of the testes. - **Growth factors:** Growth factors such as fibroblast growth factor (FGF) and platelet-derived growth factor (PDGF) are crucial for the development of the testes and their structures. 5. The brain develops from the anterior part of the neural tube. In the early stages of fetal development, the neural tube forms a cavity, the neural canal, enclosed by a layer of cells called the neuroepithelium. The neuroepithelium differentiates into various types of cells, including neurons, glial cells, and ependymal cells, which combine to form the different components of the brain. At the end of the third week, the anterior end of the neural tube expands into three primary vesicles: the prosencephalon (forebrain), the mesencephalon (midbrain), and the rhombencephalon (hindbrain). The prosencephalon develops into the telencephalon (cerebrum), the diencephalon, and the optic vesicles. The mesencephalon develops into the midbrain. The rhombencephalon develops into the metencephalon (pons and cerebellum) and the myelencephalon (medulla oblongata). The brain continues to develop throughout gestation, and its development involves the growth of the ventricles, which are fluid-filled cavities within the brain, and the formation of different brain regions responsible for specific functions. The spinal cord, which is a major component of the central nervous system, also develops from the neural tube. The neural tube begins to close during the fourth week of gestation. Once closed, the neural tube starts differentiating into the spinal cord, which extends from the brainstem to the end of the vertebral column. The spinal cord is responsible for transmitting signals between the brain and the rest of the body. - **Anencephaly:** Anencephaly is a severe neural tube defect in which the cerebrum is completely or partially missing at birth. This condition often results in death soon after birth. - **Spina bifida:** Spina bifida occurs when the neural tube fails to close properly in the spinal cord region. This can cause a range of disabilities, depending on the severity of the defect. - **Encephalocoele:** Encephalocele is a rare birth defect where part of the brain protrudes through a gap in the skull. The severity of this condition varies greatly, depending on the size and location of the protrusion.