Comparison between tract and nerve

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  Comparison between tract and nerve Nerve Nerve contain bundle of axons (nerve fibers) in the peripheral nervous system (PNS) that transmits signals between the central nervous system (CNS) and other parts of the body. It is the most important part of peripheral nervous system Location: Peripheral nervous system. Structure: Made of axons, connective tissue layers (endoneurium: axon is surrounded by it , perineurium: bundle of axons are surrounded by it, epineurium: whole nerve trunk is surrounded by it), and blood vessels. It gets myelination by Schwann cell   Function: Carries sensory signals to the CNS (afferent) from peripheral part of body or motor signals carry from from the CNS (efferent) to target organs like skeletal muscle, cardiac muscle, smooth muscle or glands Example: Sciatic nerve, median nerve, except optic nerve (though optic nerve is technically part of CNS in develop...
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Difference between development of ovary and testis

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Difference between development of ovary and testis 

                                                             Development of ovary 

1.        intermediate mesoderm form urogenital ridge, a longitudinal elevation at the dorsal body wall of fetus

2.       The coelomic epithelium and underlying mesoderm of the urogenital ridge proliferate to form the gonada ridge

3.       The coelomic epithelium forms irregular primary sex cords and incorporate primordial germ cells which migrate from the wall of yolk sac

4.       The primary sex cord extends deep to medulla and dissociate into irregular cell clusters which eventually degenerate and replace by vascular stroma, the ovarian medulla.

5.       The surface epithelium of female gonad unlike that of the male continues to proliferate

6.       In the 7th week of development it produces second generation of cords, cortical cords, which penetrate underlying mesenchyme but remain close to the surface do not extend into medulla.

7.       In the 3rd months, the cortical cords get fragmented and form isolated cell cluster.

8.      Each cell cluster consists of a primordial germ cell in the center surrounded by a layer of celomic epithelial cells

9.       The primordial germ cells form oogonia and coelomic epithelial cells form follicular cells. The resulting structure is called primordial follicles which remain confined in the cortex of the ovary

10.   A large number of primordial follicles are formed during fetal life

11.     No new primordial follicles are formed after birth

12.    The further development of  primordial follicles takes place after puberty

13.    Tunica albuginea formed around the testis but in case ovary tunica albuginea is not formed . the surface epithelium of ovary flattens to form a single layer of cells , called germinal epithelium which is continuous with peritoneum

14.    The connective tissue of ovary derived from mesoderm

Development of testis 

                                                                               Development of testis

1.          Intermediate mesoderm forms the urogenital ridge, a longitudinal elevation at the dorsal body wall of the fetus.
The coelomic epithelium and underlying mesoderm of the urogenital ridge protifelate to form the gonadal ridge.
The coelomic epithelium forms irregular primary sex cords and incorporative primordial germ cells, which migrate from the wall of the yolk sac.
The primary sex
The development of the testis ord extends deep into the medulla to form medullary cords, which lose their connection to the surface epithelium as the thick tunica albuginea forms in between the medullary cord and coelomic epithelium.

2.       Near the hilum medullary cord break up into network of tiny cell stands that form rete testis

3.       By the 4th month of interuterine life medullary cord is continuous with rete testis

4.       The testis or medullary cord contain and primitive germ cells and sustentacular cell of  sertoli cell which derived from the surface epithelium of genital ridge.

5.       Sertoli cell secrete mullarian inhibiting factor (MIF) which degenerate mullarian duct

6.       Interstitial cell of leydig derive from mesenchyme of genital ridge which derived from intermediate mesoderm ,By the 8th week of gestation leydig cell begin to produce testosterone which influence development of genital duct and external genitalia

7.       The testis or medullary cord of testis remain solid cord until puberty , then it become canalize and known seminiferous tubule, the canal of seminiferous tubules are continuous with rete testis which inturn join with efferent ductile. The efferent ductules and other excretory part of male genital system derived from mesonephric or wolffian duct

Difference between development of ovary and testis 

Development of Testis

Development of Ovary

Formation of only one generation of sex cords know as medullary cords which produce seminiferous tubules and rete testis

 

Formation of two generations of sex cords

a)      1st generation of sex cords like medullary cords form stroma of ovarian medulla

b)     2nd generation of sex cords cortical cords form primordial ovarian follicles

Formation of tunica albuginea separating seminiferous tubules from surface epithelium

No formation of tunica albuginea

The ovarian follicle are not separated from surface epithelium

Present of SRY gene develop testis

Absence of SRY gene develop ovary

 

Following genes are act during development of testis : STY, TDF,SOX9,FGF9

Following genes are act during development of ovary  : wnt4,SOX9,FOXL2

The production of testosterone in the human fetus begins shortly after the testis differentiates (around 8 weeks of gestation), and the maximum amount of testosterone in the fetal testes is reached between 10 and 15 weeks of fetal life.

8th week of intrauterine life. the ovaries are formed, they start to produce hormones such as estrogen and progesterone, which are crucial for the development of the female reproductive system and the overall growth and maturation of the fetus.

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