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Histology Exam 1 > Cytoskeleton & Cell Division > Flashcards

Cytoskeleton & Cell Division Flashcards

1
Q

Functions of cytoskeleton

A
  • Provide structural support for plasma membrane & cell organelles
  • Intracellular movement/transport of substances
  • Cell locomotion (amoeboid movement, embryonic development, cilia, flagella)
  • Muscle contraction
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2
Q

What are the 3 main elements of cytoskeleton

A
  1. microfilaments
  2. intermediate filaments
  3. microtubules
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3
Q

Microfilament structure and function

A

distributed in 3-D network throughout cytoplasm

•Important in maintaining cell shape; facilitate shape changes during movement, wound contraction during healing & Mm contraction

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4
Q

what makes up microfilament

A

actin and myosin

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5
Q

actin structure

A
  • Thin filament
  • made of smaller G-actinsubunits
  • 2 protofilaments twist together to form a double helix (F-actin). These combine to form larger actin filaments
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6
Q

G actin

A

G-actinis a small, globular protein monomer; polymerizes to form protofilaments

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7
Q

actin location

A

In microvilli& stereocilia, and beneath plasma membrane, actin links with another protein, filamin.

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8
Q

filamin

A
  • Forms support meshwork called cell cortex(= terminal web)

- Prevents cell from deformation

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9
Q

myosin structure

A
  • Thick
  • Myosin molecules are long & rod-shaped, with globular heads
  • Form thick, ropy “cables” with myosin heads sticking out sides
  • Myosin heads form cross-bridges between adjacent filaments
  • Ca & ATP required for movement of filaments for Mm contraction
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10
Q

what can myosin be classified as?

A

“motor protein” along with dynein and kinesin

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11
Q

intermediate filament structure

A
  • Intermediate in size between microfilaments & microtubules
  • Generally form large filaments that bind with intracellular structures
  • Heterogenous group; molecular make-up varies between cells
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12
Q

intermediate filament function

A
  • 1’ structural function
  • Several different classes, each expressed in different cell types—1 cell may produce more than 1 type of filament
  • Useful in immunohistochemistry & tumor ID
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13
Q

types of intermediate filaments (6)

A
  1. Cytokeratin
  2. vimentin
  3. desmin
  4. neurofilament proteins
  5. GFAP
  6. Lamin
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14
Q

Cytokeratin

A

characteristic of all epithelial cells; In epidermis of skin forms tonofibrils
(part of intermediate filament)

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15
Q

vimentin

A

found in mesodermal cells of mesenchymal origin (includes endothelial cells, muscle & neuroectodermalcells)

(part of intermediate filament)

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16
Q

desmin

A

unique to muscle cells; mesodermal origin

part of intermediate filament

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17
Q

neurofilament proteins

A

resent in nerve cells (neurons)

part of intermediate filament

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18
Q

GFAP

A

Glial Fibrillaryacidic Protein. Found in glial (support) cells of nervous system(astrocytes)

(part of intermediate filament)

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19
Q

Lamin

A

forms layer on inside of nuclear membrane.

part of intermediate filament

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20
Q

Microtubules Structure

A
  • Larger than microfilaments or intermediate filaments
  • Composed of 2 types of globular protein subunits—a& b tubulin—arranged in coiled, spiral pattern
  • Polymerize to form hollow tubes—readily assemble & disassemble
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21
Q

Microtubles Function

A
  • cell movement, maintenance of cell shape, & intracellular transport of substances
  • Movement occurs via addition or subtraction of tubulin subunits from microtubules
  • Stabilize microtubules along with capping proteins
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22
Q

Microtubule- associated proteins (MAP’s)

A

provide energy as ATPase

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23
Q

how do motor proteins interact with microtubules?

A

Motor proteins dynein& kynesinattach microtubules to organelles; allow movement in cytoplasm

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24
Q

Classic example of microtubules

A

cell spindle during cell division

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25
Q

what drugs inhibit polymerization of microtubules and cell division?

A

vincristine & vinblastin

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26
Q

Where can microtubules be found in?

A
  • cilia & flagella
  • centrioles
  • basal bodies of cilia
  • mitotic spindles
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27
Q

Axoneme Structure

A

•9 pairs of microtubules (peripheral doublets) containing dynein arms arranged in circle with central doublet in middle
(9 + 2 structure)
•Central doublet connects to peripheral doublets by radial spokes& peripheral doublets connect to each other by protein nexin

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28
Q

what is the structure of axoneme in cilia?

A

In cilia, axoneme grows from basal body, derived from modified centriole

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29
Q

Centrioles location

A

in region of cell called centrosome, or “cell center” near nucleus

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30
Q

Centrioles Function

A

cell divison. A pair of centrioles oriented at right angles to each other within centrosome

31
Q

what is a pair of centrioles called?

A

diplosome

32
Q

Centrioles Structure

A

Each centriole consists of 9 triplets of microtubules arranged in a cylinder

Acts as a nucleation center for microtubules

33
Q

Mitotic spindle

A

Occurs during mitosis, centrioles divide.

Role: controls distribution of chromosomes in daughter cells

34
Q

Cell division

A

Movement of chromosomes occurs via tubulin subunits & attachment proteins to chromatids at kinetochore(= centromere)

35
Q

Mitosis

A

growth & replication of cell

36
Q

What is interphase and its subphases?

A

“resting phase”, or time between divisions—occupies most of life of cell
subphases: (G1, S, G2)

37
Q

G1

A

Longest of cell phases (hrs to days); during which cell growth, maturation, & differentiation occur

38
Q

what specifically occurs during G1

A

hypertrophy—↑in cell size

39
Q

what specifically occurs during mitosis?

A

hyperplasia—↑in cell #

40
Q

Synthesis

A

Replication of DNA prior to division

41
Q

what happens at the beginning of S phase?

A

chromosome # is 2n;at end = 4n

42
Q

what happens prior to replication, in S phase?

A

each chromosome has a single chromatid with attached centromere

43
Q

what is the result of replication of centrioles during synthesis?

A

2 diplosomes

44
Q

G2

A
  • Preparation for mitosis

* Synthesis of ATP & tubulin for mitotic spindle

45
Q

during cell division, what is Mitosis characterized by?

A

karyokinesis (nuclear division) followed by cytokinesis (cytoplasmic division)=> 2 daughter cells

46
Q

what happens to chromosomes during S & M phase?

A

chromosomes condense, become visible, look like coiled snakes

47
Q

what happens to chromosomes during G1 & Go phase?

A

chromosomes exist in an unraveled mass

48
Q

Go

A

-extended phase where some cells end up when they lose capacity for cell divison.
-may be permanent or reversible
(“o” outside cell cycle)

49
Q

Facultative dividers

A

retain capacity for division with proper stimulus (e.g., reserve stem cells)

50
Q

Terminally differentiated

A

cells lose the capacity to divide (e.g., neurons, cardiac myocytes)

51
Q

Prophase

A
  • Chromosomes visibly condensed
  • Microfilaments & microtubules of cytoskeleton disaggregate
  • Centrioles migrate to poles of cell, form spindle apparatus with interpolarmicrotubules between them
52
Q

Prometaphase

A
  • late prophase
  • Nuclear membrane & nucleoli disappear at end of prophase
  • Mitotic spindle attaches to chromosomes at kinetochore
53
Q

Metaphase

A

chromosomes line up along equator (“metaphase plate”)

54
Q

Anaphase

A
  • centromeres split apart, chromosomes migrate to opposite ends of cell
  • Pulled by microtubules connecting centriole & kinetochore
55
Q

Telophase

A
  • Nuclear envelope reassembles, nucleoli reappear
  • Mitotic spindle disaggregates
  • Plasma membrane forms cleavage furrow, cytokinesisbegins => 2 genetically identical daughter cells
56
Q

Mitotic index

A
  • Used to describe proportion of cells in a tissue in mitosis at any given time
  • Important in tumors—estimated by counting # of mitotic figures / HPF (normally <1)
57
Q

Meiosis

A
  • Reduction division

- Sexual reproduction requires production of haploid gametes(eggs & sperm) via gametogenesis

58
Q

Where does meiosis occur?

A

only in germ cells of gonads; in male = spermatogenesis; in female = oögenesis

59
Q

what does meiosis involve?

A
  • Involves chromosomal duplication followed by two consecutive cell divisions (=> haploid gametes)
  • Fusion of gametes (fertilization) produces diploid zygote(fertilized egg)
60
Q

Result of meiosis

A

2 daughter cells

61
Q

what 2 ways do mitosis and meiosis differ?

A
  1. During prophase I, homologous pairs of chromosomes form tetrads, with exchange of chromatin via cx (chiasmataformation)
    Results in hybrid chromatids different from parents.
    Each chromosome pair has potential for cx during prophase I (23 pairs total in humans)
  2. Centromeres do not split during anaphase I
62
Q

Second meiotic division

A
  • Brief interphase II (interkinesis) with no replication of DNA
  • Nocrossing over during prophase II
  • Anaphase II—centromeres split
  • Telophase II—cytokinesis yields four haploid gametes, each genetically unique
63
Q

Gametogensis in male and female

A
  • In male 3 or 4 viable gametes (sperm) produced

* In female, cytoplasmic division unequal =>1 functional gamete (ovum) & 2 or 3 non-functional polar bodies

64
Q

when does spermatogenesis occur in males

A

at puberty

65
Q

when does oogenesis begin in females

A

during fetal development

66
Q

what occurs during oogenesis

A
  • Female germ cells enter prophase I ~ 5th month of gestation during fetal development & stop
  • Remain in prophase Iuntil ovulation (12-50 years later)
67
Q

what triggers apoptosis?

A
  • Timing in fetal development; referred to as programmed cell death
  • Some cells have finite, predetermined life spans (e.g., epithelial cells of skin or GI tract)
  • Growth & regression of ovarian follicles
  • Destruction of virus/tumor infected cells
  • Clonal deletion in thymus; removal of t-cells that react to “self” molecules

Failure of clonal deletion may => autoimmune diseases

68
Q

how does apoptosis happen?

A
  • Begins with nuclear chromatin condensation & shrinkage of nucleus (pyknosis)
  • Cell swells (as result of influx of water due to loss of ATP to maintain pumps in cell membrane)
  • Lysosomes release catalytic enzymes into cytoplasm => autolysis
69
Q

caspace cascade

A

final pathway initiated. caspaces are normally inactive enzymes

70
Q

karyolysis

A

chromatin in nucleus begins to degenerate

71
Q

Karyorhexis

A

nuclear material begins to fragment & nuclear membrane disintegrates

72
Q

what is apoptotic bodies, and what does it lead to?

A

Fragmented nuclear debris.

Leads to dead, necroticcells, later phagocytosed by macrophages & neutrophils

73
Q

Necrosis

A

refers to death of cells as a result of inflammation, traumatic injury, or pathology

Histology Exam 1 (10 decks)

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