Cytology is a science which study about human cells

1. CELL
STRUCTURE AND FUNCTION
Dr Khaleel
Associate Professor of Anatomy
Dr Khaleel

2. Dr Khaleel

3. CELLS
– are building blocks of the body.
– the basic structural and functional unit of
the living organism showing a variety of
functional specializations to perform all the
activities necessary for the survival, growth
and reproduction of the organism.
– are the smallest entities capable of
independent life.
Dr Khaleel

4. Activity 1:
1. Enumerate as many human body cells
as you can.
Dr Khaleel

5. Human Body Cells are diverse in
• Number (around 100 trillion cells = 1 x
1014
cells)
• Type (around 250 named cell types)
• Shape (round, oval, columnar,
multipolar, polyhedral, cylindrical,
fusiform, pyramidal, pyriform, etc.)
• Size (3 µm – 120 µm in diameter)
• Functions
Dr Khaleel

6. 250
Dr Khaleel

7. Blood cells are examples
of round cells
Dr Khaleel

8. Dorsal root ganglionic
cells are examples of
round cells
Dr Khaleel

9. Dorsal Root Spinal Ganglion (group of round cells)
Dr Khaleel

10. a. A micrograph of ovarian cortex shows several primordial follicles (PF) and their
flattened follicles cells (arrows), and two unilaminar primary follicles (UF) in which
the folliclar cells or granulosa cells (G) form a single cuboidal layer around the large
primary oocyte (O). Micrograph b was taken at the same magnification and shows a
larger multilayered primary follicle. Granulosa cells (G) have now proliferated to
form several layers. Dr Khaleel

11. Gastric secretory cells: p= parietal cells; c= chief cells
P
c
P
c
P
Dr Khaleel

12. Gastric secretory cells and supportive cells
Dr Khaleel

13. Tall absorptive columnar cells called Enterocytes (E) and goblet cells
(G) lining intestine
E E
G G
Dr Khaleel

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15. White & Brown Adipose/fat cells- oval shaped
White adipose tissue
Brown adipose tissue
Dr Khaleel

16. A large, multipolar, motor neuron of the anterior horn, seen whole, with all its
processes stretched out in a spinal cord smear. Notice the dark clumps of Nissl
substance in the cytoplasm. The axon cannot be identified with certainty in this
particular view. Neuroglial nuclei surround the neuron. Of these small nuclei, the
lightest ones, showing small clumps of chromatin, belong to astrocytes; any dark, round
ones (such as the one in the upper right corner) belong to oligodendroglia; and any
dark, thin, cigar-shaped ones to microglia (see possible one just to right of the neuron).
Dr Khaleel

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20. OSTEOCYTES (MULTIPOLAR CELLS)
Compact bone Dr Khaleel

21. Osteoclasts (cells with irregular shape/ border)
– Large, branched,
multinucleated
bone cells
– Sit in a depression
of bone matrix
known as Howship
lacunae(Resorption
Bay)
– Secrete enzymes
that digest bone
matrix
Dr Khaleel

22. Diverse Cellular Functions Specialized Cell(s)
1. Movement Muscle & other contractile cells
2. Form adhesive and tight junctions
between cells to form membranes Epithelial cells
3. Synthesize & secrete components of
the ECM
Fibroblasts, cells of bone and
cartilage
4. Convert physical & chemical stimuli
into action potentials
Neurons and sensory cells
5. Synthesis & secretion of enzymes Cells of digestive glands
6. Synthesis & secretion of mucous
substances Mucous-gland cells, goblet cells
7. Synthesis & secretion of steroids adrenal cortex, testis, & ovary
8. Ion transport
Cells of the kidney & salivary
gland ducts, stomach parietal
cells
9. Intracellular digestion Macrophages & some WBC
10. Lipid storage Fat cells (adipocytes)
11. Metabolite absorption Cells lining the intestine
Dr Khaleel

23. Composition human body cells
– A typical human cell, as seen by the light
microscope has two major parts: the
nucleus and cytoplasm.
– The nucleus is separated from the
cytoplasm by a nuclear membrane, and
the cytoplasm is separated from the
extracellular environment by a cell
membrane, also called the plasma
membrane.
– The different substances that make up
the cell are collectively called
protoplasm.
– Protoplasm is composed mainly of six
basic substances: water, electrolytes
(inorganic ions), proteins, lipids,
carbohydrates, and nucleic acids.
Dr Khaleel

24. Protoplasm = Nucleus + Cytoplasm
nucleus
Cytoplasm
Dr Khaleel

25. Chemistry of Protoplasm
Water
– is the principal fluid medium of the cell, present in most cells, except
for fat cells, in a concentration of 70 to 75%.
– many cellular chemicals are dissolved in the water. Others are
suspended in the water as solid particulates (colloids).
– Chemical reactions take place among the dissolved chemicals or at
the surfaces of the suspended particles or membranes.
Inorganic Ions
– The most important ions in the cell are potassium, magnesium,
phosphate, sulfate, bicarbonate, and smaller quantities of sodium,
chloride, and calcium.
– the ions provide inorganic chemicals for cellular reactions.
– also, they are necessary for operation of some of the cellular control
mechanisms.
– For instance, ions acting at the cell membrane are required for
transmission of electrochemical impulses in nerve and muscle fibers.
Dr Khaleel

26. Proteins
– After water, the most abundant substances in most cells are proteins,
which normally constitute 10 to 20% of the cell mass.
– These can be divided into two types: structural proteins and
functional proteins.
Structural proteins:
– are present in the cell mainly in the form of long filaments that
themselves are polymers of many individual protein molecules.
– are intracellular filaments which exist in the form of:
– microtubules that provide the "cytoskeletons" of such cellular
organelles as cilia, nerve axons, the mitotic spindles of dividing
cells,
– a tangled mass of thin filamentous tubules that hold the parts of
the cytoplasm and nucleoplasm together in their respective
compartments.
– Extracellularly, fibrillar proteins are found especially in the collagen
and elastin fibers of connective tissue and in blood vessel walls,
tendons, ligaments, and so forth. Dr Khaleel

27. The functional proteins
– are an entirely different types of proteins, usually composed of
combinations of a few molecules in tubular-globular form.
– are mainly the enzymes of the cell and, in contrast to the fibrillar
proteins, are often mobile in the cell fluid.
– also, many of them are adherent to membranous structures inside
the cell.
– The enzymes come into direct contact with other substances in the
cell fluid and thereby catalyze specific intracellular chemical
reactions.
– For instance, the chemical reactions that split glucose into its
component parts and then combine these with oxygen to form
carbon dioxide and water while simultaneously providing energy for
cellular function are all catalyzed by a series of protein enzymes.
Dr Khaleel

28. Lipids
– Lipids are several types of substances that are grouped together
because of their common property of being soluble in fat solvents.
– Especially important lipids are phospholipids and cholesterol, which
together constitute only about 2% of the total cell mass.
– The significance of phospholipids and cholesterol is that they are
mainly insoluble in water and, therefore, are used to form the cell
membrane and intracellular membrane barriers that separate the
different cell compartments.
– In addition to phospholipids and cholesterol, some cells contain large
quantities of triglycerides, also called neutral fat.
– In the fat cells, triglycerides often account for as much as 95% of the
cell mass.
– The fat stored in these cells represents the body's main storehouse of
energy-giving nutrients that can later be dissoluted and used to
provide energy wherever in the body it is needed.
Dr Khaleel

29. Carbohydrates
– have little structural function in the cell except as parts of
glycoprotein & glycolipid molecules, but they play a major
role in nutrition of the cell.
– Most human cells do not maintain large stores of
carbohydrates; the amount usually averages about 1% of
their total mass but increases to as much as 3% in muscle
cells and, occasionally, 6% in liver cells (hepatocytes).
– However, carbohydrate in the form of dissolved glucose is
always present in the surrounding extracellular fluid so that
it is readily available to the cell.
– Also, a small amount of carbohydrate is virtually always
stored in other cells also in the form of glycogen, which is
an insoluble polymer of glucose that can be depolymerized
and used rapidly to supply the cells' energy needs.
Dr Khaleel

30. Nucleic acids
– Are large macromolecules which consists of organic bases,
phosphate and sugar groups.
– Consists of DNA, RNA and various types of associated
macromolecules such as histones and others.
– Genes are contained in
a complex of DNA and
proteins (mostly
histones) called
chromatín, and its
basic unit of structure
is the nucleosome.
Drawing showing nucleosomes that form the basic unit of chromatin. Each nucleosome
consists of an octamer of histone proteins and approximately 140 base pairs of DNA.
Nucleosomes are joined into clusters by linker DNA and other histone proteins.
Dr Khaleel

31. Physical Structure of the Cell
– The cell is not merely a bag of fluid, enzymes, and
chemicals; rather it also contains highly organized physical
structures, called intracellular organelles, cytoskeletal
elements, and cytoplasmic inclusions.
– The physical nature of each organelle is as important as the
cell's chemical constituents for cell function.
– For instance, without one of the organelles, the
mitochondria, more than 95% of the cell's energy release
from nutrients would cease immediately.
Dr Khaleel

32. PARTS OF A CELL as seen by TEM
1. Plasma membrane/
Plasmalemma– the
outer limiting
membrane of a cell
that serves as a
selective barrier
2. Cytoplasm – the
protoplasm outside
of the nucleus which
contains the different
organelles and
inclusions of the cell
3. Nucleus – contains
the genetic material Dr Khaleel

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34. .
Dr Khaleel

35. PLASMA MEMBRANE (PM)
– the outer limiting membrane surrounding the cell.
– also known as the plasmalemma or cell membrane
– range from 7.5 to 10 nm in thickness & exhibits a trilaminar
structure (called the unit membrane) under transmission
EM microscope.
– envelope the cell & aids in maintaining its structural &
functional integrity.
– Both PM and other membranes of the different organelles
are composed of a lipid bilayer & associated proteins &
carbohydrates (Oligosaccharide chains).
– functions as a highly specific semi-permeable membrane
between the cytoplasm and the extracellular environment
– is also a sensory device that permits the cell to recognize
(and recognized by) other cells and macromolecules.
Dr Khaleel

36. Modified Fluid-Mosaic Model of PM
A. Lipid Bilayer
– is freely permeable to small nonpolar lipid-soluble
molecules but is impermeable to charged ions.
1.Molecular structure of the lipid bilayer
- is composed of phospholipids, glycolipids, & cholesterol
a.Phospholipids (60-70% of the membrane lipids)
– are amphipathic, meaning that they possess a polar (hydrophilic) head and two
nonpolar (hydrophobic) fatty acid tails.
– The polar head of each phospholipid molecule faces the
membrane surface, where as the two hydrophobic tails
projects into the interior of the membrane.
Dr Khaleel

37. PLASMA MEMBRANE
– Consist of a
bilayer of
phospholipid
molecules which
are amphipathic
i.e. have a polar
hydrophilic head
and two non-polar
hydrophobic fatty
acid tails
Dr Khaleel

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40. 2. Membrane Proteins
– are the molecular and functional components of membranes (~50%
w/w in the plasma membrane)
– are synthesized in the rough endoplasm reticulum, are modified and
completed in the Golgi apparatus, and transported in vesicles to the
cell surface.
– function as transport proteins (ion channels or carrier
proteins that bind ions and other molecules), enzymes, or
receptors (for hormones, drugs, etc)
– can be divided into two groups: Integral proteins- directly
incorporated/anchored within the lipid bilayer itself &
peripheral proteins- which exhibit a looser association with
one of the two membrane surfaces.
– The loosely bound peripheral proteins can be easily extracted from
cell membranes with inorganic salt solutions, whereas integral
proteins can be extracted only by drastic methods using detergents to
Dr Khaleel

41. Different functions of integral membrane proteins. The six major
categories of integral membrane proteins are shown in this diagram:
pumps, channels, receptors, linkers, enzymes, and structural
proteins. These categories are not mutually exclusive. A structural
membrane protein involved in cell-to-cell junctions might
simultaneously serve as a receptor, enzyme, linker, or a combination
of these functions.
Dr Khaleel

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43. 3. Oligosaccharide chains on
the external surface of the
plasmalemma form the
carbohydrate moieties of
the glycoproteins and
glycolipids.
–they are important
components of specific
molecules called receptors
that participate in
important interactions such
as cell adhesion,
recognition, and response
to protein hormones.
Dr Khaleel

44. The “Fluid Mosaic
Model”
– The membrane
proteins are
globular and float
like iceberg in a sea
of lipid
– The more
acceptable model
– Explains that
membrane is in a
dynamic state
Dr Khaleel

45. Fluidity of the lipid bilayer
– is crucial to such cellular activities as exocytosis, endocytosis,
membrane trafficking (flip-flop), & membrane biogenesis.
– is increased by a rise in temperature and by greater unsaturation of
the hydrocarbon (fatty acyl) tails.
– is decreased by an increase in the membrane’s cholesterol content.
Dr Khaleel

46. Support of the cell membrane
• PM is strengthened and supported by framework of
proteins (such as spectrin, actin & other attachment
proteins) attached to membrane via transmembrane
integral proteins. spectrin
actin in
junctional
complex
attachment proteins
Dr Khaleel

47. MAJOR FUNCTIONS of PLASMA MEMBRANE
1. Serves as a selective barrier, while maintaining integrity of
cell contents,
2. Allows for selective transport of molecules across it…into
and out of cell for purpose of ingestion and excretion and
allowing important electrolytes in and out.
3. Play a major role in cell to cell communication as receptors
are bound externally here on hormones and specialized
white blood cells etc.
Dr Khaleel

48. What Permeates the Membrane Easily?
Dr Khaleel

49. FUNCTIONS OF THE CELL SURFACE
1. Filtration barrier
2. Receptor site for
hormones & enzymes
3. Cell recognition
(GLYCOCALYX)
4. Transport across the
cell membrane
(diffusion of gases,
endocytosis,
exocytosis, etc)
Dr Khaleel

50. PHAGOCYTOSIS
EXOCYTOSIS
PINOCYTOSIS
Dr Khaleel

51. Endocytosis
–is a process in which a cell takes in material from the
extracellular fluid using dynamic movements and fusion of
the cell membrane to form cytoplasmic, membrane-
enclosed structures containing the material.
–Such cytoplasmic structures formed during endocytosis fall
into the general category of vesicles or vacuoles.
Endocytosis occurs as:
(a): Phagocytosis involves the extension from the cell of large folds
called pseudopodia which engulf large particles, for example
bacteria, and then internalize this material into a cytoplasmic vacuole
or phagosome.
(b): Pinocytosis: the cell membrane invaginates (dimples inward) to
form a pit containing a drop of small particles in solution.
• The pit pinches off inside the cell when the cell membrane fuses
and forms a pinocytotic vesicle containing the fluid.
Dr Khaleel

52. Dr Khaleel

53. Endocytosis
(c): Receptor-mediated endocytosis includes membrane proteins
called receptors which bind specific molecules (ligands).
• When many such receptors are bound by their ligands, they
aggregate in one membrane region which then invaginates and
pinches off to create vesicle or endosome containing both the
receptors and the bound ligands.
Dr Khaleel

54. Exocytosis
Dr Khaleel

55. Components of the cell
lysosome
mitochondrion
peroxisome
Golgi
apparatus
endoplasmic
reticulum
nuclear
envelope
vesicle
cytosol
plasma
membrane
nucleus
Dr Khaleel

56. Hepatocytes (liver cells ) with large, well-stained nuclei located in the
cytoplasm with one or more nucleoli
nucleus
Cytoplasm
Dr Khaleel

57. CYTOPLASM: Largest single compartment in most cells
nucleus
Cytoplasm
Dr Khaleel

58. CYTOPLASM
Consists of:
1- ORGANELLES: specialized
structures, ESSENTIAL for
vital processes of the cell.
2- Inclusions: They are not
essential for vitality of cells,
may be present or absent.
Examples are lipids, glycogen
and pigments like melanin.
3. Cytoskeleton (microtubules,
intermediate filaments and
microfilaments).
4. Cytosol: fluid portion

59. Cytoplasmic organelles
Cytoplasmic Membranous Organelles
– Mitochondria
– Rough Endoplasmic Reticulum (RER)
– Smooth Endoplasmic Reticulum (SER)
– Golgi apparatus or complex
– Lysosomes
– Coated vesicles
– Endosomes
– Peroxisomes
Non-membranous organelles
– Ribosomes (free or polyribosomes
– Centrioles & basal bodies: assembled
from microtubules
– Centrosome
– Proteasomes
Cytoskeleton:
– Microfilaments, Intermediate filaments &
– Microtubules
Cytoplasmic Inclusions
Stored foods
Glycogen
Fat (lipid) droplets
Pigments (occasionally present)
Exogenous
Carotene
Carbon particles
lead
Endogenous
Hemoglobin
Melanin
Hemosiderin
Bilirubin
Lipofuscin (lipochrome
pigment)
Secretory vesicles (granules)
Mucinogen
Zymogen granules
Cytosol
Fluid component of cytoplasm
Dr Khaleel

60. CYTOSOL
– Cell contents excluding
organelles and cytoskeleton
– Viscous aqueous solution
(gel) due to concentration of
large and small molecules
– Site of many chemical
reactions:
– initial stages in metabolic
breakdown of nutrients
– protein synthesis by
ribosomes
Adapted from ECB Fig 1-24
Dr Khaleel

61. Extracellular Fluid-The "Internal Environment“
– About 60% of the adult human body is fluid, mainly a water solution of
ions and other substances. Although most (2/3rd
) of this fluid is inside
the cells and is called intracellular fluid, about 1/3rd
is in the spaces
outside the cells and is called extracellular fluid.
– This extracellular fluid is in constant motion throughout the body.
– The extracellular fluid is also called the internal environment of the
body, or the milieu intérieur.
– Cells are capable of living, growing, and performing their special
functions as long as the proper concentrations of oxygen, glucose,
different ions, amino acids, fatty substances, and other constituents are
available in this internal environment.
Dr Khaleel

62. Differences Between Extracellular and Intracellular Fluids.
– The extracellular fluid contains large amounts of Na+
, Cl-
& bicarbonate ions
plus nutrients for the cells, such as oxygen, glucose, fatty acids, & amino
acids. It also contains carbon dioxide that is being transported from the
cells to the lungs to be excreted, plus other cellular waste products that
are being transported to the kidneys for excretion.
– The intracellular fluid differs significantly from the extracellular fluid;
specifically, by containing large amounts of K+
, Mg2+
& PO4
-3
ions instead of
the Na+
& Cl-
ions found in the extracellular fluid. Special mechanisms for
transporting ions through the cell membranes maintain the ion
concentration differences between the extracellular and intracellular
fluids. Dr Khaleel

63. CELLULAR ORGANELLES
1. Nucleus
2. Nucleolus
3. Ribosomes
4. Endoplasmic reticulum:
RER & SER
5. Mitochondria
6. Golgi Complex
7. Lysosomes and/or
endosomes
8. Peroxisomes
(microbodies)
9. Proteasomes
10. Centrioles or
centrosome/diplosome
11. Coated vesicles
12. Annulate lamellae
Dr Khaleel

64. CELLULAR ORGANELLES
Membranous organelles:
1. Nucleus
2. Mitochondria
3. Endoplasmic reticulum
(rough & smooth)
4. Golgi apparatus
5. Coated vesicles
6. Lysosomes
7. Peroxisomes
8. Annulate lamellae
Nonmembranous organelles:
9. Ribosomes
10. Proteasomes
11. Centrioles/Centrosome
12. Nucleoli

65. Main functions of cellular structures
Compartment Main function
Cytosol metabolic pathways, protein synthesis
Nucleus main genome, DNA & RNA synthesis
Endoplasmic reticulum (ER) most lipid synthesis, synthesis of
proteins in “secretory pathway”
Golgi apparatus protein modification, sorting and packaging
for delivery to cell surface or lysosomes
Lysosomes intracellular degradation
Endosomes sorting of endocytosed material
Mitochondrion ATP synthesis
Dr Khaleel

66. RIBOSOMES
– are small globular, non-
membranous, protein-producing
macromolecular assemblies
(bodies)
– about 20 x 30 nm in size
– they are protein factory of the cell
– ribosomes found in the cytosol are
composed of four segments of
rRNA and as many as 80 different
proteins.
– all ribosomes are composed of two
different-sized subunits (large &
small): both subunits consists of
rRNA & ribonucleoproteins.

67. RIBOSOMES
– the rRNA molecules of both subunits are synthesized
within the nucleus, at the nucleolus.
– their numerous proteins are synthesized in the cytoplasm
but imported to the nucleus where they associate with
rRNAs to form ribosomal subunits.
– The assembled large & small subunits then leave the
nucleus via nuclear pore & enter the cytoplasm to
participate in protein synthesis.
– Ribosomes are intensely basophilic because of the
numerous phosphate groups of the constituent rRNAs
which act as polyanions.
– Thus, sites in the cytoplasm rich in ribosomes stain
intensely with basic dyes such as hematoxylin, methylene
blue, toluidine blue, & called ergastoplasm or Nissl bodies.

68. ENDOPLASMIC RETICULUM
– Refers to an extensive membrane system throughout the
cytoplasm consisting of anastomosing network of
intercommunicating membranous channels, tubules,
saccules and and flattened cisternae.
– Exists in Two morphological forms:
A. Granular/Rough Endoplasmic Reticulum (RER)
– Most typical
– Interconnecting network of membranous tubules with
flattened cisternae
– Its outer surface is studded with ribosomes
B. Agranular/Smooth Endoplasmic Reticulum
Dr Khaleel

69. Dr Khaleel

70. Golgi apparatus
membrane
bounded
vesicles
Golgi
apparatus
endoplasmic reticulum
nuclear envelope
1 m
– Synthesis and
packaging of
molecules
secreted by cell
– Routing of
synthesized
protein to
correct cellular
compartment
– Organized into
stacks of
membrane-
bound sacs from
which vesicles
bud off
Dr Khaleel

71. RER & GOLGI COMPLEX
Dr Khaleel

72. Golgi Apparatus
– The secretory apparatus of
the cell.
– Consists of stacked saucer-
shaped flattened vesicles.
– Receives transfer vesicles
from RER.
Functions of Golgi apparatus:
1. Concentration &
modification of proteins.
2. Secretory vesicles
formation.
3. Membrane
recycling/economy
4. Formation of lysosomes.
Mature face
Forming face
Transfer
vesicles
Secretor
y
vesicles

73. Regulated and constitutive exocytosis/secretion
Dr Khaleel

74. MITOCHONDRIA (Gr. mitos, thread, + chondros, granule)
–are spherical, cylindrical or
filamentous organelles about
0.5–1 µm in diam & 10 µm
long
–may appear as slender rod or
cigar shaped
–mobile “power house/
plant/station of the cell”
–double membraned
–self-replicating by binary
fission
–vary in size, shape and number
depending on the cellular
activity
–present in all eukaryotic cells,
except few such as RBC. Dr Khaleel

75. Mitochondria
– Composed of two membranes: outer and inner
– The outer is smooth, the inner is folded to form cristae.
– the two membranes delimiting an intermembrane space.
– The outer membrane is relatively permeable and contains
enzymes that convert certain lipid substrates into forms that
can be metabolized within the mitochondrion.
– The cavity is filled with mitochondrial matrix, which
contains enzymes.
– The cristae are covered with globular units/dense bodies
with short stalks. These contain the ATP synthase
complexes that generate most of the cell's ATP.
– The mitochondrial matrix contains its own maternally
inherited DNA, which is circular in form with low
molecular weight.
Dr Khaleel

76. MITOCHONDRIA
– The inner membrane:
– is thrown into folds called cristae projecting into the
inner cavity which is filled with an amorphous substance
called matrix.
– the cristae increase surface area available for aerobic
respiration.
– contains the cytochromes, the carrier molecules of the
electron transport chain, and the enzymes involved in
ATP production.
– The mitochondrial matrix contains:
– Consists of a number of enzymes.
– Most of the enzymes involve in oxidation of fatty acids
and the kreb’s cycle.
Dr Khaleel

77. MITOCHONDRIA
– Three-dimensional representation of a mitochondrion with
its shelf-like lamellar cristae penetrating the matrix space.
Dr Khaleel

78. MEDICAL APPLICATION
– Several mitochondrial deficiency diseases have been
described, and most of them are characterized by
muscular dysfunction.
– Because of their high-energy metabolism, skeletal muscle
fibers are very sensitive to mitochondrial defects.
– These diseases typically begin with drooping of the upper eyelid
and progress to difficulties in swallowing and limb weakness.
DNA mutations or defects that can occur in the mitochondria or
the cell nucleus cause them.
– Mitochondrial inheritance is maternal.
– In the case of nuclear DNA defects, inheritance may be from
either parent or both parents.
– Generally, in these diseases the mitochondria show
morphological changes such as swelling.
Dr Khaleel

79. LYSOSOMES
–are small membrane
bound bodies of
varying shapes and
sizes containing a
number of hydrolytic
enzymes (ACID
HYDROLASES) for
intracellular digestion
–are formed through
the interaction
between the rough
endoplasmic reticulum
and Golgi apparatus.
Dr Khaleel

80. Function of lysosomes:
– Digest ingested bacteria, viruses, and toxins
– Degrade nonfunctional organelles
– Remove non functional tissues such as endometrium
during menstrual phase of menstrual cycle and after
child birth.
– Important for regression of uterus after of
childbirth
– Breakdown of glycoprotein thyroglobulin and release
thyroxine hormones
– Breakdown nonuseful tissues during organogenesis
– Removal of spent and deformed cells from circulation
– Breakdown bone matrix to release Ca2+
Dr Khaleel

81. PROTEASOMES
– recently described non-membranous organelles
– are cytoplasmic protein complexes not associated with
membrane, each approximately the size of the small
ribosomal subunit.
– function to degrade denatured, or redundant proteins or
otherwise nonfunctional polypeptides.
– also remove proteins no longer needed by the cell and
provide an important mechanism for restricting activity of
a specific protein to a certain window of time.
– Whereas lysosomes digest bulk material introduced into
the cell, or whole organelles and vesicles, proteasomes
target proteins as individual molecule.
Dr Khaleel

82. MEDICAL APPLICATION
– Failure of proteasomes or other aspects of a cell's
protein quality control can allow large aggregates of
protein to accumulate in affected cells.
– Such aggregates may adsorb other macromolecules to
them and damage or kill cells.
– Aggregates released from dead cells can accumulate in
the extracellular matrix of the tissue.
– In the brain this can interfere directly with cell function
and lead to neurodegeneration.
– Alzheimer disease and Huntington disease are two
neurologic disorders caused initially by such protein
aggregates.
Dr Khaleel

83. PEROXISOMES / MICROBODIES
– membrane bound bodies with
a finely granular homogenous
content and sometimes
containing a crystalloid body.
– De Duve's discoveries date to
1949,
– approximately 0.5 µm in
diameter
– are common in liver
(hepatocytes) and kidney cells
– involved in breakdown of
potentially harmful substances.
– contain several oxidative
enzymes in the production or
destruction (e.g. catalases) of
hydrogen peroxide.
Dr Khaleel

84. CENTRIOLES
–Paired cylindrical
organelles
–Hollow cylinder, open in
one end; closed in the
other
–Long axis: Perpendicular
to each other
–Important for cell division
–Absent in nondividing
cells such as neurons and
striated muscle fibers Dr Khaleel

85. MEDICAL AND BIOLOGICAL IMPORTANCE OF CELLS AND ORGANELLES
1. All higher living organisms including humans are made up of cells.
2. Human body contains wide variety of cells that differ in structure and function.
3. Human cell contains subcellular structures like nucleus, mitochondria, lysosomes and
peroxisomes etc.
4. Each subcellular structure the has unique shape and function.
5. Some diseases are due to a lack of subcellular structures. Zellwegers syndrome is due to lack
of peroxisomes.
6. Lysosomal enzymes are involved in spreading of cancer.
7. Lack of lysosomes or its enzymes results in lysosomal diseases.
8. Growth of cells requires cell divisions. Cell cycle encompasses all the events of cell division.
9. Cells are not immortal. They have finite life span. Because of this humans are not immortal.
10. Cell death is crucial for shaping of organs during development and for recovery from injuries.
11. Biochemistry explores molecular mechanisms of normal cellular processes as well as
diseases.
12. Mitochondria is involved in apoptosis. Dr Khaleel

86. THE CYTOSKELETON
– is the supporting framework of minute filaments & tubules.
– includes the fibrillar elements of cytoplasm
– a complex network of structural proteins & includes:
(1) microtubules,
(2) microfilaments (actin filaments), and
(3) intermediate filaments.
Functions
– support the cell & facilitate cell attachment
– determine the cell shape & are involved in all cell shape
changes such as those during endocytosis, exocytosis,
secretion, and cell locomotion,
– play an important role in the movements of organelles and
cytoplasmic vesicles, and also allow the movement of the
entire cell.
Dr Khaleel

87. Cytoskeleton
Microfilaments microtubules
intermediate
filaments
– Extensive network of long, thin protein filaments
– Thinnest filaments - actin  contractile machinery
– Thickest filaments - microtubules (minute hollow
tubes) - important for dividing cells - chromosomes
– Intermediate filaments - mechanical strengthening
Adapted from ECB Fig 1-27
Dr Khaleel

88. CYTOPLASMIC INCLUSIONS
–are lifeless accumulations of metabolites or cell products
regarded as dispensable and often temporary constituents;
not essential for survival of the cell.
–Includes:
1. Pigments – a. Endogenous
b. Exogenous
2. Lipid droplets
3. Glycogen granules
4. Protein Crystals
5. Secretory granules
6. Vacuoles Dr Khaleel

89. NUCLEUS
–Found in all human cells
except RBC, platelets,
reticulocytes or
spherocytes.
–The number, shape, size, &
location of nucleus vary in
different types and activity
of the cells.
–Commonly stains blue
because of its nucleic acids
and acidic proteins.
Dr Khaleel

90. Nucleus
Structure
Dr Khaleel

91. – The size and morphologic features of nuclei in a specific
normal tissue tend to be uniform.
– In contrast, the nuclei in cancer cells often have irregular
shapes, variable sizes, and atypical chromatin patterns.
– The nucleus is a highly specialized organelle that serves as
the information processing and administrative center of
the cell.
– Nucleus contains genetic apparatus encoded in the
deoxyribonucleic acid (DNA) of chromosomes.
Dr Khaleel

92. Functions of the Nucleus
1. It stores DNA, the cell's hereditary material
2. It coordinates the cell's activities, which include
growth, intermediary metabolism, protein
synthesis, and reproduction (cell division)
3. It is source of ribosomal, messenger and transfer
RNA
4. It is essential for the vitality and division of the
cell.
Dr Khaleel

93. –The nucleus has the nuclear envelope, nucleolus,
nucleoplasm, & chromatin.
– Directs protein synthesis in the cytoplasm via ribosomal
ribonucleic acid (rRNA), messenger RNA (mRNA), &
transfer RNA (tRNA), which are synthesized in the nucleus.
Nuclear Envelope
– Surrounds the nuclear material and separates the contents
of the nucleus from the cytoplasm.
–Outer limit of the nucleus separating it from the
cytoplasm (about 40 nm thick).
– consists inner and outer nuclear membranes separated
from each other by a narrow perinuclear space known as
perinuclear cisterna.
– Is perforated at intervals by openings called nuclear
pores.
Dr Khaleel

94. The nucleus
Dr Khaleel

95. NUCLEOPLASM (NUCLEAR SAP)
• The semi fluid gel-matrix found inside the nucleus is called nucleoplasm.
• Within the nucleoplasm, most of the nuclear material consists of chromatin,
the less condensed form of the cell's DNA that organizes to form
chromosomes during mitosis or cell division.
• The nucleus also contains one or more nucleoli, organelles that synthesize
protein-producing macromolecular assemblies called ribosomes, and a
variety of other smaller components, such as Cajal bodies, speckles, PML
bodies, splicing-factor compartments and interchromatin granule clusters.
Dr Khaleel

96. • Nucleus constitute more than10-20% of the cell volume
– a double membrane, two unit membranes, 20-30 nm apart
– This forms an interior space
– The space is continuous with the interior of the rough
endoplasmic reticulum
Nucleus Structure
Dr Khaleel

97. Interior of the nucleus:
– Nucleoplasm,
analogous to
cytoplasm
– Includes the soluble
protein
nucleoplasmin
– the nuclear matrix, a
network of protein
fibers which support
and organize the
chromatin and other
structures.
Nucleus Structure
Dr Khaleel

98. • Chromatins
– Active chromatin
(euchromatin): appear
lighter,
– Inactive chromatin
(heterochromatin): darker
and located near
periphery of nucleus
• Nucleolus: has
– a granular region
– site of ribosome
assembly
Interphase nucleus
Interior of the
Nucleus
Dr Khaleel

99. NUCLEAR CHROMATIN
–is Nuclear material that
contains DNA and proteins;
–the structural manifestation
of chromosomes in
interphase.
Two Types:
A. Heterochromatin – the
condensed coiled part;
metabolically inert
B. Euchromatin – the
dispersed, less coiled
regions of the
chromosome; active in
protein synthesis Dr Khaleel

100. NUCLEAR CHROMATIN
Dr Khaleel

101. Chromatin and Chromosomes
–Packed inside the nucleus of every human cell is nearly 2
meter of DNA, which is divided into 46 individual structures,
chromosome.
–Packing all this material into a microscopic cell nucleus is an
extraordinary feat of packaging.
–For DNA to function, it can't be crammed into the nucleus
like a ball of string.
–Instead, it is combined with proteins and organized into a
precise, compact structure, a dense string-like fiber called
chromatin.
Dr Khaleel

102. CHROMOSOMES
– May show irregular
densities of staining
along their lengths
– Small visible mass is the
sex chromatin/Barr
body.
– In female neutrophil
granular leukocytes is
seen as drumstick
appendage
– It has become possible
to determine by light
microscopy the genetic
sex of an individual. Dr Khaleel

103. a Karyotype of a human male
Dr Khaleel

104. – If the centromere is in the center and the arms are of approximately the same
length, the chromosome is said to be metacentric; if it is not centered and the arms
are of clearly different lengths, it is submetacentric; and if it is near one end, it is
acrocentric.
– The short arm of the chromosome is designated as “p” for “petite,” and the long
arm is designated as “q” for no other reason than it is the next letter of the
alphabet.
– The arms of the chromosome are indicated by the chromosome number followed
by the p or q designation (e.g., 15p).
– Chromosomes 13, 14, 15, 21, and 22 have small masses of chromatin called
satellites attached to their short arms by narrow stalks. At the ends of each
chromosome are special DNA sequences called telomeres.
– Telomeres allow the end of the DNA molecule to be replicated completely
Dr Khaleel

105. NUCLEOLUS
–A round conspicuous structure
eccentrically located in the
nucleus; rich in rRNA and basic
proteins; intensely basophilic
due to the presence of
ribonucleoproteins.
–Nucleus contains one or more
nucleoli
–Sites of ribosome production
– Ribosomes then migrate to the
cytoplasm through nuclear pores
Dr Khaleel

106. CELL CYCLE
– It is the whole life history of a cell.
– Involves two major stages: mitosis (dividing stage) and
interphase (non-dividing stage).
– Interphase: is the phase between two successive mitoses.
– In interphase, the cell nucleus appears as dark dot formed
by the chromatin.
Dr Khaleel

107. Dr Khaleel

108. The four Stages of the cell cycle
1. In G1 stage:
– the cell either continues the cycle or enters a quiescent phase called
G0.
– From this phase, most cells can return to the cycle, but most cells
stay in G0 for a long time or even for their entire lifetime.
– The checking or restriction point (R) in G1 stops the cycle under
conditions unfavorable to the cell.
– When the cell passes this restriction point, it continues the cycle
through
2. The synthetic phase (S)
– chromosomes duplicate longitudinally
– centrioles also duplicate
3. G2 stage: cell increase in size and ready for division
4. Mitosis (M stage) except when interrupted by another
Dr Khaleel

109. Phases of Mitosis:-
1- Prophase
– Nucleus enlarges.
– Chromatins start to condense & becomes rod-like
chromosomes.
– Each chromosome consists of two parallel sister
chromatids attached to one another at the centromere.
– Outside the nucleus, the centrosomes with their centrioles
separate and migrate to opposite poles of the cell.
– The duplication of the centrosome and centrioles occurs
during S phase of the interphase.
– Simultaneously with the centrosome migration, the
microtubules of the mitotic spindle appear between the
two centrosomes and the nucleolus disappears as
transcriptional activity there stops. Dr Khaleel

110. – In Late prophase, the nuclear envelope breaks down when
proteins of the nuclear lamina and inner membrane are
phosphorylated (PO4
3–
groups added).
– The nuclear lamina and pore complexes disassemble and
these proteins along with membrane vesicles disperse in
local cytosol and ER.
– Chromosomes appear as a line without arrangements.
Late prophase: No
distinct nuclear
envelope, no
nucleoli,
Condensed
chromosomes
Dr Khaleel

111. Prophase I:
– is normally extended for 3 weeks during male
gametogenesis (meiosis) in humans, whereas
– Primary oocytes arrest in this meiotic phase from the
time of their formation in the fetal ovary through the
woman's reproductive maturity, that is, for about 13
years to 50 years (5 decades).
Dr Khaleel

112. 2- Metaphase
– the condensed chromosomes
attach to microtubules of the
mitotic spindle at large
electron-dense protein
complexes called kinetochores
(Gr. kinetos, moving, + chora,
central region), which are
located at a constricted region
of each chromatid called the
centromere (Gr. kentron,
center, + meros, part).
– The chromosomes are moved
to the equatorial plane of the
now more spherical cell.
Dr Khaleel

113. 2- Metaphase
– Kinetochore microtubules
bound to sister chromatids are
continuous with centrosomes
at opposite poles of the mitotic
spindle.
– Chromosomes become very
thick & arranged in equatorial
plane.
– Mitotic spindle formed
completely.
– Nuclear envelop disappear
completely.
Dr Khaleel

114. Electron micrograph of the metaphase of a human lung cell in
tissue culture. Note the insertion of microtubules in the
centromeres (arrows) of the densely stained chromosomes.
Dr Khaleel

115. 3- Anaphase
In early anaphase:
• The sister chromatids separate from each other and are slowly pulled
at their kinetochores toward opposite spindle poles by kinesin motor
proteins moving along the microtubules.
• During this time the spindle poles also move farther apart.
• The sister chromatids separate longitudinally & pulled toward each
pole of the cell by microtubules.
Late anaphase: ixed by beginning of cytoplasmic division, &
initiate the cleavage furrow.
• A belt-like contractile ring, containing actin microfilaments
associated with myosins, develops in the peripheral cytoplasm
at the level of equator of the parent cell.
Dr Khaleel

116. Late anaphase: The chromosomes are located in both cell poles, to
distribute the DNA equally between the daughter cells. Cleavage
furrow also appeared at the equator of the parent cell.
Dr Khaleel

117. 4- Telophase
– the two sets of chromosomes are now at their destination (i.e. at
the spindle poles) and begin reverting to their uncondensed
(chromatid) state.
– Microtubules of the spindle disassemble and the nuclear envelope
begins to reassemble around each set of daughter chromosomes
This phase is characterized by:
– Reappearance of nuclear envelops and nuclei appear as 2 dark
spots.
– End of nuclear division.
– Cytokinesis: cytoplasm divides by further constriction of contractile
ring and this progresses until the cytoplasm and its organelles are
divided in two daughter cells.
Dr Khaleel

118. Telophase and cytokinesis
Dr Khaleel

119. Dr Khaleel

120. Telophase
At which phase of mitoses the
pointer indicates?
How do you know? (1 reason)
the nucleus reappears as 2 dark spots
Dr Khaleel

121. Meiosis
– is a specialized process involving two closely associated cell divisions
that occurs only in the cells that will form sperm and egg cells or
gametes in the gonads.
– Two key features characterize meiosis:
1. The cells produced are haploid, with just one chromosome from
each pair present in the rest of the body's (somatic) cells.
2. Early in the process the homologous chromosomes of each pair
(one from the mother, one from the father) physically associate
along their lengths in an activity termed synapsis.
– During synapsis, double-stranded breaks and repairs occur in
the DNA, some of which result in reciprocal DNA exchanges
called crossovers between the aligned maternal and paternal
chromosomes. Dr Khaleel

122. – Crossing over produces new combinations of genes in the
chromosomes in the germ cells so that few if any
chromosomes are exactly the same as those from the
mother and father.
– The cell entering meiosis has just completed DNA
replication in a typical S phase so that each of its
chromosomes contains the two identical copies referred to
as sister chromatids.
– Meiosis produces haploid cells with new genetic
combinations.
Dr Khaleel

123. Stem Cells and Tissue Renewal
– Most tissues undergo constant cell turnover because of
continuous cell division and the ongoing death of cells.
– Nerve and cardiac muscle cells are exceptions, because
they do not multiply postnatally and therefore have greatly
reduced potential for regeneration.
– The turnover rate of cells varies greatly from one tissue to
another—rapid in the epithelium of the digestive tract and
the epidermis, slow in the pancreas and the thyroid gland.
– Mitotic cells are often difficult to identify conclusively in
sectioned adult organs, but can be recognized in rapidly
growing tissues by high incidence of mitotic figures.
Dr Khaleel

124. Identify dividing cells (mitotic figers) in this slide
Dr Khaleel

125. Identify dividing cells (mitotic figers) in this slide
Dr Khaleel

126. Dr Khaleel

127. TIPS ON TERMINOLOGIES
1. Atrophy- diminish in size of cell, tissue or organ
– Senile atrophy
– Disuse atrophy
– Disease/pathologic atrophy
2. Hypertrophy- increase in size of cell, tissue or organ
3. Hyperplasia- increase in number of cells
4. Metaplasia- transformation from one cell type to another
5. Neoplasm/Tumor- abnormal mass of tissue or cells
– Benign tumor
– Malignant tumor
6. Apoptosis- normal programmed cell death
7. Necrosis- pathological cell or tissue death
8. Gangrene: gross pathological tissue or organ death sometimes accompanied by
microbial invasion.
Dr Khaleel

128. Hypertrophy of heart wall
Dr Khaleel

129. Hypertrophy of thyroid gland
Dr Khaleel

130. Thyroid gland, hypertrophy and hyperplasia
Dr Khaleel

131. Hypertrophy and atrophy of kidneys
Dr Khaleel

132. Foot, dry gangrene – Clinical presentation
Dr Khaleel

133. THANK U
Dr Khaleel