What are integuments? What is their importance in plant reproduction?
What is :
a) Wolffian duct
b) Mullerian duct?
What is Bartholin Gland's function?
What is :
a) Wolffian duct
b) Mullerian duct?
What is Bartholin Gland's function?
In seed plants the ovule ("small egg") is the structure that gives rise to and contains the female reproductive cells. It consists of three parts: The integument(s), forming its outer layer(s), the nucellus (or remnant of the megasporangium), and the female gametophyte (formed from a haploid megaspore) in its center. The female gametophyte — specifically termed a megagametophyte— is also called the embryo sac in angiosperms. The megagametophyte produces an egg cell (or several in some groups) for the purpose of fertilization. An integument is a protective cell layer surrounding the ovule. Gymnosperms typically have one integument (unitegmic) while angiosperms typically have two (bitegmic). The evolutionary origin of the inner integument (which is integral to the formation of ovules from megasporangia) has been proposed to be by enclosure of a megasporangium by sterile branches (telomes). Elkinsia, a preovulate taxon, has a lobed structure fused to the lower third of the megasporangium, with the lobes extending upwards in a ring around the megasporangium. This might, through fusion between lobes and between the structure and the megasporangium, have produced an integument.
The origin of the second or outer integument has been an area of active contention for some time. The cupules of some extinct taxa have been suggested as the origin of the outer integument. A few angiosperms produce vascular tissue in the outer integument, the orientation of which suggests that the outer surface is morphologically abaxial. This suggests that cupules of the kind produced by the Caytoniales or Glossopteridales may have evolved into the outer integument of angiosperms.
The integuments develop into the seed coat when the ovule matures after fertilization.
The integuments do not enclose the nucellus completely but retain an opening at the apex referred to as the micropyle. The micropyle opening allows the pollen (a male gametophyte) to enter the ovule for fertilization. In gymnosperms (e.g., conifers), the pollen is drawn into the ovule on a drop of fluid that exudes out of the micropyle, the so-called pollination drop mechanism.Subsequently, the micropyle closes. In angiosperms, only a pollen tube enters the micropyle. During germination, the seedlings's radicle emerges through the micropyle.
Located opposite from the micropyle is the chalaza where the nucellus is joined to the integuments. Nutrients from the plant travel through the phloem of the vascular system to the funiculus and outer integument and from there apoplastically and symplastically through the chalaza to the nucellus inside the ovule. In chalazogamous plants, the pollen tubes enter the ovule through the chalaza instead of the micropyle opening.
Wolffian Duct:
An embryonal duct that forms from the 25–30th days of gestation in association with the rudimentary pronephros, later becoming the mesonephric excretory duct, the ‘second embryonal kidney’, giving rise to the male reproductive system—rete testis, efferent ducts, epididymis, vas deferens, seminal vesicles. In females, the lack of testosterone results in Wolffian duct regression at the 10–11th week, a portion of which remains as embryonal ‘rests’—Gartner’s duct cysts, epoophoron, Skene's glands, paroophoron.
Mullerian Duct:
The müllerian ducts are the primordial anlage of the female reproductive tract. They differentiate to form the fallopian tubes, uterus, the uterine cervix, and the superior aspect of the vagina. A wide variety of malformations can occur when this system is disrupted.
Bartholin Gland function:
Function. Bartholin's glands secrete mucus to provide vaginal lubrication.Bartholin's glands secrete relatively minute amounts of fluid when a woman is sexually aroused. The fluid may slightly moisten the labial opening of the vagina, serving to make contact with this sensitive area more comfortable.
An integument is a protective cell layer surrounding the ovule. Gymnosperms typically have one integument (unitegmic) while angiosperms typically have two (bitegmic). The evolutionary origin of the inner integument (which is integral to the formation of ovules from megasporangia) has been proposed to be by enclosure of a megasporangium by sterile branches (telomes). Elkinsia, a preovulate taxon, has a lobed structure fused to the lower third of the megasporangium, with the lobes extending upwards in a ring around the megasporangium. This might, through fusion between lobes and between the structure and the megasporangium, have produced an integument.
The origin of the second or outer integument has been an area of active contention for some time. The cupules of some extinct taxa have been suggested as the origin of the outer integument. A few angiosperms produce vascular tissue in the outer integument, the orientation of which suggests that the outer surface is morphologically abaxial. This suggests that cupules of the kind produced by the Caytoniales or Glossopteridales may have evolved into the outer integument of angiosperms.
The integuments develop into the seed coat when the ovule matures after fertilization.
The integuments do not enclose the nucellus completely but retain an opening at the apex referred to as the micropyle. The micropyle opening allows the pollen (a male gametophyte) to enter the ovule for fertilization. In gymnosperms (e.g., conifers), the pollen is drawn into the ovule on a drop of fluid that exudes out of the micropyle, the so-called pollination drop mechanism.Subsequently, the micropyle closes. In angiosperms, only a pollen tube enters the micropyle. During germination, the seedlings's radicle emerges through the micropyle.
Located opposite from the micropyle is the chalaza where the nucellus is joined to the integuments. Nutrients from the plant travel through the phloem of the vascular system to the funiculus and outer integument and from there apoplastically and symplastically through the chalaza to the nucellus inside the ovule. In chalazogamous plants, the pollen tubes enter the ovule through the chalaza instead of the micropyle opening.
Wolffian Duct:
An embryonal duct that forms from the 25–30th days of gestation in association with the rudimentary pronephros, later becoming the mesonephric excretory duct, the ‘second embryonal kidney’, giving rise to the male reproductive system—rete testis, efferent ducts, epididymis, vas deferens, seminal vesicles. In females, the lack of testosterone results in Wolffian duct regression at the 10–11th week, a portion of which remains as embryonal ‘rests’—Gartner’s duct cysts, epoophoron, Skene's glands, paroophoron.
Mullerian Duct:
The müllerian ducts are the primordial anlage of the female reproductive tract. They differentiate to form the fallopian tubes, uterus, the uterine cervix, and the superior aspect of the vagina. A wide variety of malformations can occur when this system is disrupted.
Bartholin Gland function:
Function. Bartholin's glands secrete mucus to provide vaginal lubrication.Bartholin's glands secrete relatively minute amounts of fluid when a woman is sexually aroused. The fluid may slightly moisten the labial opening of the vagina, serving to make contact with this sensitive area more comfortable.
