Derivatives Of Mesoderm

DERIVATIVES OF MESODERM

Q. 1

All are mesodermal origin, except:

 A

Sphincter pupillae

 B

Cilary muscle

 C

Iris

 D

Ovarian tissue

Q. 1

All are mesodermal origin, except:

 A

Sphincter pupillae

 B

Cilary muscle

 C

Iris

 D

Ovarian tissue

Ans. A

Explanation:

A. i.e. Sphincter pupillae


Q. 2

All of the following are mesodermal in origin except:

 A

Dilators of iris

 B

Iris stroma

 C

Ciliary body

 D

Choroid

Q. 2

All of the following are mesodermal in origin except:

 A

Dilators of iris

 B

Iris stroma

 C

Ciliary body

 D

Choroid

Ans. A

Explanation:

A i.e. Dilator of iris 

  • Nervous system including all neurons, neuroglia & Schwann cells are of ectodermalQ origin except microglia which is mesodermal 
  • All muscles (smooth, striated & cardiac) are mesodermal except the musculature of the iris (sphincter & dilator pupillae) which are ectodermal 
  • Kidney, ureter, bladder trigone, posterior wall of female urethra, posterior wall of prostatic male urethra & inner glandular zone of prostate are of mesodermal origin.

Endodermal origin epithelium is seen in urinary bladder except trigone (mesodermal); Female urethra except part of its posterior wall (mesodermal); male urethra except part of the posterior wall of its prostatic part (mesodermal) & except the penile urethra lying in glans penis (ectoderm) and greater part of prostate except inner glandular zone (mesodermal)


Q. 3

Which of the following is not derivative of mesoderm‑

 A

Ureter

 B

Gall bladder

 C

Uterus

 D

Epididymis

Q. 3

Which of the following is not derivative of mesoderm‑

 A

Ureter

 B

Gall bladder

 C

Uterus

 D

Epididymis

Ans. B

Explanation:

B i.e. Gall bladder


Q. 4

Paraxial mesoderm develops into:

 A

Somites

 B

Mesonephric duct

 C

Notochord

 D

All of the above

Q. 4

Paraxial mesoderm develops into:

 A

Somites

 B

Mesonephric duct

 C

Notochord

 D

All of the above

Ans. A

Explanation:

A. i.e. Somites


Q. 5

Which of the following muscles is notderivative of mesoderm?

 A

Skeletal muscles

 B

Smooth muscles

 C

Cardiac myocyte

 D

Dilators of pupil

Q. 5

Which of the following muscles is notderivative of mesoderm?

 A

Skeletal muscles

 B

Smooth muscles

 C

Cardiac myocyte

 D

Dilators of pupil

Ans. D

Explanation:

Ans. d. Dilators of pupil

Smooth muscles of iris (constrictor and dilator pupillae)

  • The sphincter and dilator pupillae muscles of the iris are derived from the ectoderm.
  • The region between the optic cup and the overlying surface epithelium is filled with loose mesenchyme.
  • The sphincter and dilator pupillae muscles form in this tissue.

Derivatives of Mesoderm

  • All connective tissue i.e. superficial and deepfascia(ligaments, tendons, aponeurosis, dermis of skin’, adipose reticular tissue, cartilage and bone)
  • All cardiovascular system i.e. heart, blood vessels, lymphatic and blood cells.
  • All Musculoskeletal system i.e. bone, cartilage, tendon, ligaments and muscles (smooth, striated and cardiac) musculature of iris (sphincter and dilator pupillae) which are ectodermale
  • All Reproductive system i.e. ovary, uterine tubes, uterus and upper vagina in females; testis, epididymis, ductus deferens, prostate (inner glandular zone) seminal vesicle and ejaculatory duct in males.
  • Except epithelium of greater part of vagina, vestibule and inner surface of labia minora in female and greater part of prostate (except inner glandular zone) is endodermal.
  • Outer surface of labia ininora and whole labia majora are ectodermal
  • All urinary system i.e. kidney, ureters, trigone of bladder, posterior part of female urethra, posterior part of urethra (upper half) of males and inner glandular zone of prostate
  • Epithelium of urinary bladder (except trigone), female urethra (except posterior wall), male urethra (except prostatic part which is mesodermal and penile urethra which is ectodermal) and most of prostate (except inner glandular zone) are endodermal
  • Mesothelial lining of –pleural, pericardial, and peritoneal cavitiese; and of tunica vaginalis, bursae and
  • Dentine of teethe; (enamel is ectodermal’)
  • Duramater and Microgliae
  • Except these all other nervous system i.e. neurons, neuroglia and schwann cells are ectodermal
  • Eye i.e. substance of cornea, sclera, choroid, ciliary body and iris
  • Except anterior epithelium of cornea, epithelium of conjunctiva, epithelium of ciliary and iris; iris muscles and lens are ectodermal.

Q. 6

Paraxial mesoderm contributes to development of ‑

 A

Parietal peritoneum

 B

Visceral peritoneum

 C

Skeletal muscles

 D

Peritoneal cavity

Q. 6

Paraxial mesoderm contributes to development of ‑

 A

Parietal peritoneum

 B

Visceral peritoneum

 C

Skeletal muscles

 D

Peritoneal cavity

Ans. C

Explanation:

Ans. is ‘c’ i.e., Skeletal muscles 

  • The intraembryonic mesoderm located on each side of notochord proliferate and is arranged in three columns : (i) paraxial mesoderm (immediately lateral to notochord); (ii) intermediate mesoderm (just lateral to paraxial mesoderm); and (iii) lateral plate mesoderm (more laterally placed mesoderm).
  • Small spaces appear in lateral plate mesoderm which later fuse to form intraembryonic coelom. This space divides the lateral plate mesoderm into : (i) an outer parietal layer (somatopleuric mesoderm) continous with mesoderm covering the amnion, and (ii) an inner visceral layer (splanchnopleuric mesoderm) continous with mesoderm covering the yolk sac. During 2nd month the intraembryonic coelom is divided into three cavities : (i) pericardial cavity (ii) pleural cavity, and (iii) peritoneal cavity. Somatopleuric mesoderm forms the parietal layer of these cavities (i.e., parietal pericardium, perietal layer of pleura and parietal peritoneum) and splanchnopleuric mesoderm forms the visceral layer of these cavities.
  • Paraxial mesoderm differentiates into somites. By the end of 20th day, the first pair of somites have formed in neck region. After this, about 3 pairs of somites are formed per day and by the end of 5th week about 42-44 somite pairs are formed (4-occipital, 8-cervical, 12-thoracic, 5-lumbar, 5-sacral and 8-10 cooccygeal). Somites are further differentiated into :‑
  1. Dermatomyotome :- Give rise to skeletal muscles and dermis.
  2. Sclerotomes :- Give rise to vertebral column.
  • Sclerotomes which surround notochord starts projecting posteriorly (dorsally) to surround neural tube and forms.
  • Ventral sclerotomes :- Give rise to vertebral body and annulus fibrosus.
  • Lateral sclerotomes :- Give rise to vertebral arch (pedicle and lamina).
  • Dorsal sclerotomes :- Give rise to spinous process.
  • The notochord forms the nucleus pulsosus.


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