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Histology > Cytology > Flashcards

Cytology Flashcards

1
Q

Cytoskeleton componets

A
  • Microfilaments
  • Intermediate filaments
  • Microtubules
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2
Q

Functions of cytoskeleton

A

-Shaping of cells
-Important in cellular movement
Movement of vesicles and organelles in the cytoplasm
Movement of parts of the cell forming pseudopodia
Movement of the cell as a whole as in spermatozoa
- Supportive internal skeleton to the cell

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3
Q

Microfilaments

Synonym

A

Actin Filaments

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4
Q

Microfilaments

Size

A

Thin filaments of 6nm in diameter

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5
Q

Microfilaments

Percentage

A

Actin constitues 15% of total protein content of non-muscle cell

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6
Q

Microfilaments

Sites

A

In non-muscle cells: form a sheath under the cell membrane and are also present in cell extensions like pseudopodian and microvilli
In muscle cells: ACtin filaments interdigitate with thick myosin filaments in parallel arrays

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7
Q

Microfilaments

Structure

A

It is found in the cytoplasm in 2 forms:
G-actin: dispersed in the cytosol, not visible with EM, polymerize together to firm F-actin
F-actin: The filament consists of a double stranded helix. Each strand is a polymer of G-actin

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8
Q

Actin filaments ends

A

Plus end where molecules are added leading t the elongation of the filament
Minus end where actin molecules are removed leading to shortening of actin filaments

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9
Q

Microfilaments

Functions

A

-Contraction of muscle cells
-Anchorage and movement of membrane proteins
-Movement of plasma membrane as in endo and exocytosis
-Formation of pseudopodia and microvilli
-Locomotion of cells
Formation of contractile ring during cell divisionn

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10
Q

Intermediate filaments

Size

A

10 nm

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11
Q

Intermediate filaments

Characteristics

A

Stable structures with neither a plus or minus end

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12
Q

Keratins

A

Include tonofilaments

They are found in most epithelia

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13
Q

Desmin

A

In muscles

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14
Q

Vimentin

A

In fibroblasts

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15
Q

Neurofilaments

A

In neurons (axons and dendrites)

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16
Q

Glial filaments

A

In neuroglial cells

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17
Q

Intermediate filaments

Sites in the cytoplasm

A
  • Keratin
  • Desmin
  • Vimentin
  • Neurofilaments
  • Glial filaments
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18
Q

Intermediate filaments

Sities in the nucleus

A

Lamins

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19
Q

Microtubules

Sites

A

Cytoplasm of all cells except RBCs

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20
Q

Microtubules

Size

A

24 nm

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21
Q

Microtubules

Structure

A

Longitudinally:long, straight, rigid, hollow cylinders
Transverse: fine circles with dense wall and hollow core

22
Q

Microtubules

Subunits

A

Tubulin

Is of 2 types: alpha and beta

23
Q

Tubulin dimers

A

One dimer is alpha and beta
They are organised into spiral with total number of 13 subunits in each complete turn of the spiralto form 13 linear protofilaments

24
Q

Microtubules

Types in the cytoplasm

A

Dispersed microtubules

Organised microtubules as in cilia and centrioles

25
Q

Microtubules

Functions

A

-Maintain the shape of the cell because of its rigidity
-Dispersed microtubules are responsible for intracellular transport of organelles and vesicles
-Microtubules provide basis structure for:
Centrioles
Cilia
Flagella
Mitotic spindle

26
Q

MTOC

Definition, function,examples

A

Microtubules organising centre is a structure found in eukaryotic cells
It is responsibe for polymerization of tubulin subunits to form microtubules
examples:
- Basal bodies of the cilia
- Centrioles
- Centromeres of the chromosomes

27
Q

Microtubules associated proteins (MAPs)

definition

A

They are special proteins that assist in intracellular movement of organelles and vesicles and also prevent depolarization of the mictrotubule

28
Q

Kinesin

A

Motor protein

Moves the vesicles towards the plus + end

29
Q

Cytoplasm dynein

A

Motor protein

Moves vesicles towards the minus - end

30
Q

Dynamin

A

it is a protein that forms cross-bridges between neighbouring microtubules

31
Q

Axonemal dynein

A

is a proteins that foms arms of the doublets of the shaft of the cilia and is motor protein responsible for ciliary movement

32
Q

Functions of centrioles

A

They form mitotic spindles
They forms basal bodies of cilia and flagella
They form microtubules organising centres (MTOCs)

33
Q

Cilia sites

A

Some cells of the respiratory system

Female genital tract (fallopian tube and uterus)

34
Q

Cilium size

A

Diameter 0.2 um and length of 7-10 um

35
Q

Functions of cilia

A

In trachea, they move to keep the airways clear of mucus and dirt
In the fallopian tube to move the ovum towards the uterus for possible pregnancy

36
Q

Nucleus stain

A

By H&E, the nucleus is basophilic because of its contents

By Feulgen stain, DNA is feulgen positive (red) while RNA is feulgen negative

37
Q

Nucleus structure by EM

A

Nuclear envelope
Nucleolus
Chromatin
Nucleoplasm or karyoplasm

38
Q

Nuclear envelope is formed of 2 parallel membranes each is a unit membrane seperated by……..

A

perinuclear cisternae

39
Q

Nuclear pore

A

It is a channel which provide bidirectional communication between nucleoplasm and cytoplasm

40
Q

Types of heterochromatin

A

Peripheral chromatin
Nucleolar associated chromatin
Islands of chromatin

41
Q

Nuleosome

A

is the basic structural unit of chromatin. DNA is wrapped twice around a core of 8 histones (octamer)
The octamer is formed of 2 molecules of H2A, H2B, H3 and H4
10-11 nm in diameter

42
Q

Selinoid

A

Nucelosomes become coiled around an axis with 6 nucleosomes per turn
30 nm

43
Q

Looped domain of chromatin

A

Further coiling of the 30 nm forming series of loops

300 nm

44
Q

Heterochromain and metaphase chromosomes

A

700 nm
1400 nm
formed during mitosis due to further coiling and condensation

45
Q

Nucleolus LM

A

Deepley basophilic due to its content of ribonucleoproteins

46
Q

Nucleolus EM

A

Pars amorpha
Pars fibrosa
Pars granulosa

47
Q

Pars amorpha

A

Round pale areas formed of tips of chromosomes 13, 14, 15, 21, 22
they are nucleolar organisers responsible for formation of rRNA

48
Q

Pars fibrosa

A

Formed of fine electron dense filments of newly formed rRNA

49
Q

Pars granulosa

A

dense strands having granular appearance and is the site of formation of ribosomal subunits

50
Q

Functions of nucleolus

A

Formation of ribosomes

Histology (5 decks)

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