Histology

1. Cell Division
Dr. Rabia Inam Gandapore
Assistant Professor
Head of Department Anatomy
(Dentistry-BKCD)
B.D.S (SBDC), M.Phil. Anatomy (KMU),
Dip. Implant (Sharjah, Bangkok, ACHERS) , CHPE
(KMU),CHR (KMU), Dip. Arts (Florence, Italy)

2. Teaching Methodology
 LGF (Long Group Format)
 SGF (Short Group Format)
 LGD (Long Group Discussion, Interactive discussion with the use of models or diagrams)
 SGD (Short Group)
 SDL (Self-Directed Learning)
 DSL (Directed-Self Learning)
 PBL (Problem- Based Learning)
 Online Teaching Method
 Role Play
 Demonstrations
 Laboratory
 Museum
 Library (Computed Assisted Learning or E-Learning)
 Assignments
 Video tutorial method

3. Goal/Aim (main objective)
 To help/facilitate/augment the students about the:
1. Explain the process of cell division.
2. Describe mitotic cell division with its stages
3. Explain the process of Meiosis.
4. Describe karyotyping.
5. Explain the non-disjunction of chromosomes.
6. Correlate the process of non-disjunction with chromosomal abnormalities

4. Specific Learning Objectives (cognitive)
At the end of the lecture the student will able to:
1. Explain the process of cell division.
2. Describe mitotic cell division with its stages
3. Explain the process of Meiosis.
4. Describe karyotyping.
5. Explain the non-disjunction of chromosomes.
6. Correlate the process of non-disjunction with chromosomal abnormalities
7. Enlist Difference between Mitosis and Meiosis

5. Psychomotor Objective: (Guided response)
 A student to draw labelled diagram of Mitosis and Meiosis and enlist its differences

6. Affective domain
 To be able to display a good code of conduct and moral values in the class.
 To cooperate with the teacher and in groups with the colleagues.
 To demonstrate a responsible behavior in the class and be punctual, regular, attentive and
on time in the class.
 To be able to perform well in the class under the guidance and supervision of the teacher.
 Study the topic before entering the class.
 Discuss among colleagues the topic under discussion in SGDs.
 Participate in group activities and museum classes and follow the rules.
 Volunteer to participate in psychomotor activities.
 Listen to the teacher's instructions carefully and follow the guidelines.
 Ask questions in the class by raising hand and avoid creating a disturbance.
 To be able to submit all assignments on time and get your sketch logbooks checked.

7. Lesson contents
Clinical chair side question: Students will be asked if they know what is the function of
Outline:
1. Activity 1 The facilitator will explain the student's process of cell division. mitotic cell division
with its stages and explain process of Meiosis.
 Activity 2 The facilitator will ask the students to make a labeled diagram of the mitosis and
meiosis
 Activity 3 The facilitator will ask the students a few Multiple Choice Questions related to it with
flashcards.

8.  Students assessment: MCQs, Flashcards, Diagrams labeling.
 Learning resources: Langman’s T.W. Sadler, Laiq Hussain Siddiqui, Snell Clinical Anatomy, Netter’s
Atlas, BD Chaurasia’s Human anatomy, Internet sources links.

9. Chromosome Theory of
Inheritance
 MITOSIS
 MEIOSIS
 GENE MUTATIONS

10. Chromosome Theory of Inheritance
 Specific genes on chromosomes inherited from father & mother
 Human= 35,000 genes on 46 chromosomes
 Linked Genes= Genes on same chromosome tend to inherited together
 Somatic cell= 23 Homologous paris chromosomes to form diploid number
46
 Autosome= 22 pair matching chromosome + One pair =sex chromosome
 Sex pair XX= Female
 Sex pair XY= Male
 Ocyte + sperm (Hyploid number 23 chromosome) & union of gametes at
fertilization restores diploid 46

12. Cell Division
EXPLAIN THE PROCESS OF CELL DIVISION.

13. Cell Division
 All cells of Human body originates by division of pre-existing cells.
 Cell division comprise of :
1. Karyokinesis: Nuclear division
2. Cytokinesis: Cytoplasmic division
 2 mechanism of Cell division:
1. Mitosis: Occurs in ordinary somatic cells
2. Meiosis: occurs in developing germ cells.

14. Cell Cycle
 Cell belonging to renewing cell population undergoes a sequence
of events that is repeated over & over again.This sequence is
called cell cycle
 2 main parts:
1. M Phase: Mitosis occurs , Time: 3—60 minutes to complete
2. Inter- Phase: Intervening period between consecutive cell
divisions; cell make necessary preparation for cell division, Time:
Longer time. Divided into 3 phases;
a. G1 (Gap 1) Phase
b. S (Synthesis) Phase
c. G2 (Gap 2) Phase
d. G0 (G Zero) Phase

15. Cell cycle or cell-division cycle= series of self regulated events that take place in cell leading to division & duplication (replication)
Only takes place in renewing cell population
G1 Phase:
 Follows Cell division
 Synthesis of RNA &
Proteins occur
 Cell Volume restored
 Duration: 8 Hours
S Phase:
 DNA Synthesis
 Exact replica of genetic
material
 Replication of centrioles
 Duration: 8 hours
G2 Phase:
 Between End of S phase &
beginning of mitosis
 Production & accumulation of
energy to be used during
mitosis
 Synthesis of Tubulin to be
assembled in mircotubules
during mitosis
 Duration: 2-4 hours
G0 Phase:
Resting phase
Static cells leave cell cycle
permanently (No mitosis further)
Stable cells retains its potential to
re-enter celly cycle ( Mitosis occurs
when needed

18. Cell Death
 Rate of cell proliferation & death determines net cell population in
human body
 2 types cell death
1. Necrosis (accidental): occurs in pathological condition, swelling
followed by cell fragmentation, release of cellular content into
extracellular space. Debris engulfed by macrophages which release
cytokines (triggers inflammation in tissue)
2. Apoptosis (programmed): Activation of internally encoded process
of self destruction (Intrinsic or extrinsic signals). Cell shrinks,
nucleus small & undergo fragmentation and breaks into apoptotic
bodies which are phagocytosed. No cytokines, no inflammatory
response. Occurs mainly during embryonic & fetal development.

19. MITOSIS
DESCRIBE MITOTIC CELL DIVISION WITH ITS STAGES

20. MITOSIS
 One cell divides, giving rise to 2 daughter cells; genetically identical to parent cell receives 46 chromosomes.
 Replication (Before cell enters mitosis): each chromosome replicates its deoxyribonucleic acid (DNA).
Chromosomes are extremely long & spread diffusely through the nucleus
 Onset of mitosis: chromosomes begin to coil, contract & condense; mark beginning of prophase.
1. Prophase: Each chromosome now consists of two parallel subunits, chromatids, joined at centromere.
chromosomes continue to condense, shorten, and thicken.
2. Prometaphase: chromatids become distinguishable, Nucleoli disappears. Mitotic spindle formed
3. Metaphase: chromosomes line up in equatorial plane (doubled structure is clearly visible). Each is attached by
interpolar microtubules extending from centromere to centriole, forming mitotic spindle. No nuclear envelope
4. Anaphase: centromere of chromosome divides & migration of chromatids to opposite poles of spindle.
5. Telophase: chromosomes uncoil & lengthen, nuclear envelope reforms & cytoplasm divides.
 Each daughter cell receives 46 chromosomes & maintains same number of chromosomes as mother cell

23. MEIOSIS
 EXPLAIN THE PROCESS OF MEIOSIS

24. MEIOSIS
 Cell division: takes place in germ cells to generate male & female gametes, sperm &
egg cells, respectively.
 Meiosis requires 2 cell divisions to reduce number of chromosomes to haploid (23):
a. Meiosis I
b. Meiosis II
1. Meiosis I: male and female germ cells (spermatocytes and primary oocytes) at the
beginning of meiosis I replicate their DNA so that each of the 46 chromosomes is duplicated
into sister chromatids. In contrast to mitosis, however, homologous chromosomes then
align themselves in pairs, a process called synapsis.
 Pairing is exact, except for XY combination.
 Homologous pairs then separate into 2 daughter cells.
2. Meiosis II: separates sister chromatids. Each gamete then contains 23 chromosomes

25. Prophase-1 5 Stages
1.Leptotene= chromosomes visble,
nucleus long thin strand
2. Zygotene: Homologous
Chromosome in close apposition long
its length= Synapses
3. Pachytene: Coiled, thick, shorter,
Nucleus (n), Chromosome pair called
bivalent.
4. Diplotene: 2 chromatids connected
at chiasmata (similar to crossing over )
5. Diakinesis: separation of
chromosomes. Chiasmata thickened,
Nucleolus & Nuclear envelope
disappears.
Metaphase
1. Spindle of
microtubules
produced by
centrioles.
2. Equatorial
plate &
chromosome
s alignment
at center of
spindle
Anaphase
1. Chromosomes separates and
moves to opposite poles of spindle
2. No division at centromeres (unlike
mitosis) & whole chromosome moves
to opposite poles
3. Haploid chromosome (both parent)
4. Homologous chromosome pair
faces certain pole and move towards
it
5.Maternal & Paternal chromosome in
each daughter cell becomes matter of
pure chance and random separation
add genetic diversity
Telophase
1. Nuclei
reconstituted,
2. cytoplasm
divides into 2
daughter cells
(Haploid 23) But
each
chromosome has
2 chromatids
Meiosis 2
1. Same as mitosis
( 4 stages)
2. Division at
centromere
3.Sister chromatids
separates & move
to opposite poles
4. Reconstitution of
nuclei occurs
5. Cytokinesis
divide cell into 2
cells. Haploid (n)

26. Crossover
 Meiosis I: interchange of chromatid segments between paired homologous chromosomes
 Segments of chromatids break & are exchanged as homologous chromosomes separate.
 As separation occurs, points of interchange are temporarily united and form an X-like
structure, a chiasma
 30 to 40 crossovers (1 or 2 per chromosome) with each meiotic I division are most
frequent between genes that are far apart on a chromosome.
 As a result of meiotic divisions,
(a) genetic variability is enhanced through crossover, which redistributes genetic material,
and through random distribution of homologous chromosomes to the daughter cells
(b) each germ cell contains a haploid number of chromosomes, so that at fertilization the
diploid number of 46 is restored

28. Polar Bodies
 During meiosis:
 1 primary oocyte: gives rise to 4 daughter
cells, each with 22 plus 1 X chromosomes.
Only 1 develops into a mature gamete
oocyte;other 3 polar bodies, receive little
cytoplasm & degenerate during subsequent
development.
 1 primary spermatocyte: gives rise to 4
daughter cells, two with 22 plus 1 X
chromosomes and two with 22 plus 1 Y
chromosomes. All 4 develop into mature
gametes.

30. First & second meiotic divisions

31. KARYOTYPING
DESCRIBE KARYOTYPING.

32. Karyotyping
(Diagnostic Technique to identify genetic abnormality)
 Laboratory technique that involves arranging an individual's chromosomes by:
1. size
2. shape,
3. banding pattern.
 This visual representation is called a karyotype
 It reveal chromosomal abnormalities, such as:
missing or extra chromosomes.

33. Karyotyping

36. CHROMOSOMAL
ABNORMALITIES
 CORRELATE THE PROCESS OF NON-DISJUNCTION WITH CHROMOSOMAL
ABNORMALITIES

37. Chromosomal abnormalities
 Numeric
Addition or loss of whole chromosomes in human cells
 Structural
change in structure of chromosome with deletion, duplication or
inversion of a segment
Causes: environmental factor-virusrs, radiations & drugs

38. NON-DISJUNCTION OF
CHROMOSOMES
 EXPLAIN THE NON-DISJUNCTION OF CHROMOSOMES

39. Non-disjunction of Chromosomes
 Non-disjunction is a mistake that can occur during cell
division, where chromosomes fail to separate properly.
 This can happen during meiosis I or II
 leading to an unequal distribution of chromosomes in
daughter cells.
 Increases in woman at 35 years and older

42.  Non-disjunction can result in abnormal numbers of chromosomes
in the daughter cells, leading to conditions like:
 Down syndrome (Trisomy 21: 47 chromosomes), where there is
an extra chromosome 21.
 Turner syndrome
 Klinefelter syndrome : only in males, 47 XXY type or 48
chromosomes: 44 autosome & XXXY
 Edwards syndrome
 Monosomy (45 chromosome)

43. Down syndrome
(trisomy,21) (13,14 &15)(47,xx or xy+21)
 common autosomal trisomy among live –born
children ,it has frequency of about 1 in 800 of
live birth .
 It doesn't usually run in families and it
increases with the mother age.
 Growth & mental retardation
 Craniofacial abnormalities
 Cardiac defects & hypotonia

45. Trisomy 18 and 13

46. Turner syndrome
 only in females
 results when one of X chromosomes
(sex chromosomes) is missing or
partially missing.
 Turner syndrome can cause a variety of
medical and developmental problems,
including
 short height
 failure of ovaries to develop
 heart defects.

48. Klinefelter Syndrome
 boys and men are born with
an extra X chromosome.
 Chromosomes are packages
of genes found in every cell in
the body.
 There are 2 types of
chromosome, called the sex
chromosomes, that determine
the genetic sex of a baby

50. Chromosomal Structural anomalies
 Cri du chat syndrome due to deletion of a region of
chromosome 5
 Newborns donot survive

52. Uncontrolled Mitosis or Mitotic catastrophe
 If mitosis is not controlled, unlimited cell
division occurs causing cancerous
tumors
 Oncogenes are special proteins that
increase the chance that a normal cell
develops into a tumor cell
Cancer cells

53. Assignment
 Assignment: Clinical Correlation
 Summarize each in PowerPoint and submit with your roll numbers, Name,
Class/batch, Year, Date of Submission to CR.

54. Thank You
ANY QUESTIONS?