Ultrastructure of nucleus

 Ultrastructure of Nucleus

🟦 Introduction
A Nucleus is made up of 4 part
*Nuclear membrane or karyotheca
*Nucleolus
*Nuclear sap or nucleoplasm
*Chromatin reticulum or nuclear reticulum

🟦Nuclear membrane or karyotheca
*Karyotheca is a bilayered membrane that surrounded nucleus

🟡structure-
1)made up of lipoprotein
2) this is the trilaminar membrane
3) diameter 62-90 Å
4) distance between to memories 100-500 Å
5) intermediate space between two membrane is called perinuclear cisternae or perinuclear space.

6) the pores presentation nuclear membrane called nuclear pores
7) diameter of the pores 300-500 Å
8) ribosome and endoplasmic reticulum is is attached to it outer membrane of the nuclear membrane

🟡Nuclear pore-
~nuclear pore is a complex structure.
~part of the pore is diaphragm, septum, plug or nucleoplasmin and various annuli.
~annulus is a circular part that covers the nuclear pores.

~a pore with annulus called pore complex.
~sometimes this pore complex is surrounded by a permeable membrane 
~ often it is made up of 9 cylinder among which one present at the centre and another 8 present at the peripheral part.
~often this nuclear pore shows network of granular filament
~this pore transfer RNA, ribosome,protein inside and outside the nucleus.

🟡Function of nuclear membrane
*Give a specific structure to the nucleus
*Protect the the middle part of the nucleus
*Nuclear pore show path to ribosome and RNA.
*Nuclear membrane control the interaction between nucleoplasm and cytoplasm
*Nuclear membrane take part in information of cisternae of endoplasmic reticulum.
*Indirectly take part in protein synthesis.


🟦 Nucleolus

🟡 Introduction
*In plural called nucleoli
*In 1781 Fontana discovered this
*In 1840 Wagner described this
*In 1840 Bowman name this 'nucleolus'
*Nucleolus is attached to it nuclear organiser by chromatin fibre
*In the nucleus, nucleolus be in one or more no.
*Rounded in shape and pigment in acidic pigment.
*Nucleolus is found in the the stationary phase of cell division.

🟡 Structure
Nucleus has four part
1) amorphous Portion
2) granular portion
3) fibrillar portion
4) chromatin portion

🔴 Amorphous Portion
*This is Homogeneous matrix of nucleolus
*This is made up of protein

🔴 Granular Portion
*This is made up of of numerous granule
*Volume of this granule are 150-200 Å
*It Scattered in the nucleolus
*This granule made up of protein and RNA in the ratio of 2:1
*This granule produce ribosome

🔴 Fibrillar Portion
*This portion is called Nucleolema
*This part made up of small and finute fibril
*Diameter of this finute fibril is 50-80Å
*This is made up of protein and RNA
*They may produce the granule

🔴 Chromatin Portion
*This is a part of chromatin which is attached with nucleolus.
*This chromatin are of two types-
  a) perinuclear chromatin (this chromatin present in the peripheral part of the nucleolus)
  b) intranuclear chromatin (this chromatin present in the inner side of the nucleolus)

🟡 Function of Nucleus
1) the main function of nucleolus is production of ribosomal RNA and protein synthesis.
2) nucleolus is the production centre of ribosomal content
3) after synthesis of ribosomal RNA (rRNA) and protein float into the nucleus fast and then into cytoplasm.
4) in the nucleus division nucleolus take a big role in spindle fibre formation
5) in the last Prophase phase of cell division nucleolus disappeared and in the telophase phase it's again appear.

🟦 Nucleoplasm
🟡 Feature
*Discovered by Strasburger in 1882
*Nucleolus and nuclear reticulum present in nucleoplasm or karyolimph.
*This is homogeneous, clear, semi liquid, colloidal, granular and little acidic in nature.
*Nucleolus and chromatin reticulum floats on the the nuclear sap.
*In Nucleoplasm DNA,RNA,phosphoprotein, histone and various type of enzyme (DNA polymerase RNA polymerase nucleoside phosphorylase etc), videos type of minerals (Na,Ca,P,Mg,K) present
*The part of nucleoplasm which is made up of finute fiber, which is acetic protein and act as chromatin structure is called nuclear matrix.
🟡 Function
Nucleoplasm act as the matrix of nucleus in which chromatin fibre and various other organ floats.

🟦 Nuclear reticulum or Chromatin reticulum
🟡 Introduction
*Nuclear reticulum can be found in nucleoplasm in the interphase phase of cell division in the form of net.
*Nuclear reticulum become pigmented in alkaline pigment
*Define finute fibre is made up of nucleoprotein.
*this finute fibre which is spindle in nature, they are called chromatin fibre
*This chromatin fibre is made up of nucleic acids (DNA, RNA) and protein
*In the interphase phase of cell division this chromatin fibre are are attached with one another to form an eight like structure inspirit in the whole nucleoplasm area.
*But in the prophase phase this fibre tangled to proforma definite chromosome.

🟡 Chromatin fibre
Heitz in 1928 classified chromatin fibre into 2 part one is euchromatin and another is heterochromatin.

🔴 Euchromatin
*This is very finute.
*diameter-10-30 nm
*Any stable nucleus or interphase nucleus these are expanded.
*it's take less pigmented in pigmentation.
*It's contain active gene.
🔴 Heterochromatin
*This chromatin is comparatively thick.
*Diameter 100 nm
*In stable  nucleus or in interface nucleus they are spindle in nature.
*It's take dark pigment in pigmentation
*Did not carry active gene.

🟣Karyosome
*The rounded substance in the nucleus is called karyosome.
*Karyosome refers to 

the chromatin material inside the cell nucleus when the cell is undergoing meiotic division.
*It appears to be a dense mass in the middle of the cell and is often mistaken for the nucleolus.
*The karyosome or karyosphere is particularly known for its role in oogenesis.
🟡 Functions
*Formation of chromosome in the time of cell division.
*it carry Hereditary substance or DNA.