Cytology
Cytology
Anatomy and Physiology Text and Laboratory
Workbook, Stephen G. Davenport, Copyright 2006, All
Rights Reserved, no part of this publication can be
used for any commercial purpose. Permission requests
should be addressed to Stephen G. Davenport, Link
Publishing, P.O. Box 15562, San Antonio, TX, 78212
Lab Activity 1 – Cell Model
• Cytology is the study of the structure and
function of cells.
• Photomicrograph
– Photograph taken by using a light microscope. An
electron microscope produces an electron
micrograph.
• The cell is divided into three major parts:
– plasma membrane - the semipermeable boundary of
cell
– cytoplasm - area between nucleus and plasma
membrane which houses organelles and inclusions
– nucleus -the specialized organelle that controls the
cell
Exfoliated Squamous Cells
• The mouth is lined with a tissue covering
called stratified squamous epithelium.
Stratified squamous epithelium is
described as multi-layered (stratified) flat
(squamous) lining tissue (epithelium).
• The squamous surface cells can be
removed by scraping (exfoliation) and
observed for cell structure.
Fig 4.1
Lab Activity 2 –
Exfoliated Squamous Cells
•
•
•
•
•
Plasma membrane forms the
semipermeable boundary of the
cell.
Cytoplasm is the component of
the cell between the plasma
membrane and the nucleus. Its
fluid is called cytosol and houses
the cell’s organelles and
inclusions.
Organelles are “little organs” of
the cell. These structures, such as
the nucleus, are considered to be
functional components.
Inclusions are chemical or
foreign bodies in the cell. A lipid
droplet is a typical inclusion.
Nucleus is an organelle that is the
repository for the genetic material,
the DNA of the cell.
STRATIFIED SQUAMOUS
EPITHELIUM
• Stratified squamous epithelium is a
protective lining commonly found forming
the surface of areas that are subject to
abrasion.
• Prepared microscope slide of stratified
squamous epithelium are from locations
such as the inside lining of the mouth, the
esophagus, and the vagina.
Fig. 4.5
1
Lab Activity 4 –
Stratified Squamous Cells
• Stratified squamous
epithelium is a
protective surface
lining.
• Observe the
specimen’s surfaces
to locate the
distinctive dark
stained multicellular
layer of tissue.
Fig. 4.7
Fig. 4.8
ADIPOSE TISSUE
• Adipose cells
(adipocytes) are the
cells organized to
form adipose tissue.
Adipocytes are
specialized for the
storage of fat
(triglycerides) in the
form of a lipid droplet.
Fig. 4.9
Fig. 4.10
Lab Activity 5 –
Adipose Tissue
• Observe a prepared
microscope slide of
“Adipose tissue.” If a
slide preparation is
not available
complete the study
using the following
illustrations and
photographs.
Fig. 4.11
2
Lab Activity 6 –
Blood
BLOOD CELLS
• Red blood cells (erythrocytes) are highly
specialized cells that contain hemoglobin (an
inclusion) which mostly transports oxygen.
– Circulating red blood cells do not have a nucleus
(anucleate).
• White blood cells (leukocytes) are of several
different types, so there will be a variety of sizes
and structural characteristics observed among
the cells.
– All have a single nucleus; however, the nuclear
location and shape will vary depending upon the type
of white blood cell.
Fig. 4.13
•
Fig. 4.12
Human blood smear. Erythrocytes are
anucleate biconcave discs. The nuclei of
leukocytes stains blue and exhibit several
different shapes.
HUMAN SPERM
Sperm cells are highly specialized cells in structure
and function.
– Structurally, they have three distinctive regions: (1) a
head - that contains the nucleus (genetic material),
(2) a midpiece - that houses most of the cytoplasm,
and (3) a flagellum (tail) - that provides locomotion.
– The cellular features of streamlined shape and
structural specialization allow the sperm to move
through the female reproductive tract and fertilize the
egg.
Fig. 4.14
Lab Activity 7 –
Sperm
Fig. 4.15
Fig. 4.16
Sperm are small motile cells designed for
movement and fertilization of an egg (oocyte).
3
Lab Activity 8 –
Ciliated Columnar Epithelium
COLUMNAR CILIATED CELLS and GOBLET
(MUCOUS) CELLS
•
Columnar ciliated cells
are tall columnar cells with
cilia located on their
exposed (free) surface.
• They form epithelial linings
that function in the
movement of materials
(mucus) over the surface of
the cells (epithelium).
• The respiratory airway, the
trachea, is an ideal site for
the study of columnar
ciliated cells. The cells are
arranged in a single layer,
but some cells are taller
than others
Fig. 4.17
Fig. 4.18
• Observe a slide labeled "Pseudostratified Columnar
Ciliated Epithelium - Trachea" or "Trachea."
SMOOTH MUSCLE CELLS
Fig. 4.19
Fig. 4.20
•
Lab Activity 9 –
Smooth Muscle Cells
Smooth muscle cells are the constituents of
smooth muscle tissue. The cells are called
smooth because they lack the cross-bands
called striations that characterize the two other
types of muscle (skeletal and cardiac).
Lab Activity 10 –
Teased Smooth Muscle Cells
Fig. 4.23
Fig. 4.21
Fig. 4.22
• Observe a slide labeled "Intestine - jejunum (or Intestine
- duodenum, or Intestine - ileum)."
• Observe a preparation labeled "Teased Smooth Muscle."
If a slide preparation is not available complete the study
using the following illustrations and photographs.
4
Work Sheet
Fig. 4.11
Identify and give the function of the cells. What characteristics do
the cells share?
STRUCTURE AND FUNCTION OF A
GENERALIZED CELL
The following study of cell structures mostly relies
upon Figure 4.1, a drawing of a generalized cell. The
anatomy of the structures is mostly drawn from photographs
from electron microscopes (electron photomicrographs).
Generalized functions are given for each of the cell’s
structures.
5
Plasma Membrane
•
The is the limiting membrane which forms the cell
boundary. It separates the watery environments of the
cytoplasm (intracellular fluid) and the external
environment (extracellular fluid).
•
The plasma membrane is not a homogeneous
structure with the same organization and chemical
components over its entire surface.
• The molecular structure of the plasma membrane
determines its functions. Membrane functions include
the
–
–
–
–
Maintenance of Boundary
• The plasma membrane is not a homogeneous
structure with the same organization and
chemical components over its entire surface.
maintenance of a physical boundary,
the transport of materials into and out of the cell,
providing receptor sites, and
cell identity markers.
Boundary Functions
• Columnar cells that forms
the lining of the intestine
have different boundary
functions.
The columnar cells of the
intestinal epithelium
function in protection,
absorption, secretion of
absorbed nutrients into
the blood and lymphatics,
anchorage to neighboring
cells, prohibiting
intercellular diffusion, etc.
Fig. 4.24
Fig. 3A.6
•
Molecular Structure
•
The molecular structure of the plasma
membrane determines its functions.
Membrane functions include the
maintenance of a physical boundary, the
transport of materials into and out of the
cell, providing receptor sites, and cell
identity markers.
The plasma membrane consists of a
phospholipid framework. Other lipid molecules
of the plasma membrane include cholesterol and
glycolipids. Proteins are found both embedded
in the phospholipid framework or located on its
surface.
Fig. 4.25
6
Molecular Structure of Plasma
Membrane
Lipid Molecules
The lipids include phospholipids,
cholesterol, and glycolipids. The most
abundant lipids are the phospholipids.
Lipid Molecules
• Phospholipids
– The phospholipids are a group of lipids that have a polar
(charged) "head" region that contains phosphorus attached to a
nonpolar (uncharged) "tail" region that contains a pair of fatty
acids. Fundamental membrane structure (framework) is
produced by the phospholipids being arranged in two layers
(bilayer). They are amphiphilic molecules, hydrophobic and
hydrophlic.
• Glycolipids
– Glycolipids are lipid molecules with attached carbohydrates.
Glycolipids are located in the outer phospholipid layer.
• Cholesterol
– Cholesterol is distributed in both layers of the phospholipid
bilayer. Its hydrocarbon ring structure is hydrophilic and faces
the watery environments, and the carbon chain is hydrophobic
facing away from the watery environments (along with the
hydrophobic tails of the phospholipids).
Lipid Molecules - Functions
• Phospholipids
– Phospholipids produce the structural framework of
the plasma membrane. Also, the phospholipids allow
simple diffusion (movement from high to low
concentrations), of substances that are small,
nonpolar, and lipid soluble. Substances which are
large, polar, and are not lipid soluble have limited
ability to diffuse through the phospholipid bilayer.
Figure 4.26
Lipids of the plasma membrane include phospholipids, glycolipids and cholesterol.
Lipid Molecules - Functions
Glycolipids
– The glycolipids along with
the glycoproteins function in
producing the glycocalyx
(sugar covering) of cells.
The glycocalyx functions in
cell-to-cell adhesion and
cellular recognition. Some
glycolipids function in the
plasma membrane turn
over and recycling
mechanism.
Fig. 4.28
Fig. 4.27
7
Lipid Molecules - Functions
Cholesterol
– Cholesterol is a lipid
that belongs to the
steroid group of lipids.
Cholesterol functions
in stabilization the
plasma membrane,
and if transported
internally is used as a
precursor in the
manufacture of other
steroids such as
estrogen and
testosterone.
PROTEIN MOLECULES
Fig. 4.29
Integral or peripheral according to
their location.
Protein Location
• Integral proteins
– Integral proteins are located within the phospholipid
bilayer. They may be embedded in either the outer or
inner phospholipid layer or, they may penetrate both
layers as transmembrane proteins.
• Peripheral proteins
– are located at the phospholipid membrane surface
either associated with integral proteins or lipids.
– Glycoproteins are proteins with attached
carbohydrate chains. The carbohydrate chains
project away from the membrane into the extracellular
environment.
Protein Molecules – Functions
Fig. 4.30
Protein Molecules – Functions
• Channels
– Transmembrane protein channels allow the specific
passage either by passive or active transport (require
ATP) of small molecules and ions.
Fig. 4.31
• Carrier Molecules
– Transmembrane
protein carrier
molecules allow a type
of transport called
facilitated diffusion.
This type of transport
is passive and uses
carrier molecules with
specific receptor sites
to transport specific
substances across the
membrane.
Fig. 4.32
8
Protein Molecules – Functions
Protein Molecules – Functions
• Peripheral proteins
– Peripheral proteins
may serve as
structural proteins to
produce cell structure,
especially the
cytoskeleton.
Peripheral proteins
also function as
enzymes, which
mediate chemical
reactions by
functioning as
catalysts.
• Glycoproteins
– Glycoproteins have
various functions such
as cell identify markers
and receptors. They
are also the primary
contributors in
producing the cell’s
glycocalyx (sugar
covering), important in
cell-to-cell adhesion.
Fig. 4.33
Fig. 4.35
Fig. 4.34
Gap Junctions
MEMBRANE JUNCTIONS
A gap junction is a membrane junction formed by an
interaction of adjacent cell membrane proteins which
produces a channel between the two cells. The channel
allows the passage of small molecules and ions from
cell to cell. This type of membrane junction is found in
tissues such as cardiac muscle that conduct electrical
activity by the passage of charged atoms (ions).
Membrane junctions are direct
membrane to membrane interactions
and include gap junctions,
desmosomes, and tight junctions.
Fig. 4.36
Desmosomes
• A desmosome is a membrane junction formed by thin
intercellular filament proteins that are associated with
localized thickened membrane layers of adjacent cells.
The thin intercellular protein filaments bridge the two
separated membranes. This type of membrane junction
produces great mechanical strength and is typically
located in epithelial tissues such as the outer layer of the
skin where strong cell adhesion is required
Lab Activity 11 –
Desmosomes
• Obtain a prepared microscope slide labeled
“Intercellular bridges.” Intercellular bridges
(desmosomes) are observed in the epidermis of
the skin. Intercellular bridges provide great
mechanical strength to the tissue.
Fig. 4.38
Fig. 4.37
9
Tight Junctions
• A tight junction is a membrane junction formed by the
connection of proteins of the plasma membranes of
adjacent cells. The connection of the membranes
prevents the diffusion of substances through the
intercellular space. This type of junction is located in
areas such as the lining of the urinary bladder where
diffusion of water and ions across the lining membrane is
restricted.
MICROVILLI
Fig. 4.39
• Microvilli
– Microvilli are plasma membrane projections. A cell
which functions in the absorption of materials often
has its surface membrane modified into microvilli.
Microvilli increase the plasma membrane surface
area, which increases the capability of the cell to
interact with its extracellular environment.
Fig. 3A.6
Fig. 4.41
• Microvilli are extensions of the plasma membrane that increase
surface area. The photograph on the left (Fig 4.41) is of microvilli
(described as a brush border) of columnar cells lining the small
intestine (1,000x). Microvilli should not be confused with motile
surface organelles called cilia. The photograph on the right (Fig
4.41) is ciliated columnar cells from the trachea (430x).
Fig. 4.40
Cytosol
CYTOPLASM
Cytoplasm is the region between
the plasma membrane and the
nucleus.
• Cytosol is mostly water with a variety of
dissolved inorganic and organic substances
from ions to complex proteins. Suspended in
the cytosol are organelles and inclusions.
– Organelles are the "little organs" (functional
components) of the cell and include the nucleus,
mitochondria, ribosomes, etc. They may or may not
be surrounded by a membrane.
– Inclusions are chemical substances in the cytoplasm.
They are not functional units but are used in the
functioning of the cell. Inclusions include glycogen,
lipid droplets, and hemoglobin.
10
ORGANELLES
The organelles ("little organs") are
a variety of structures that perform
various cellular functions.
Fig. 4.42
NUCLEUS
• The nucleus is an organelle bounded by the
nuclear envelope.
– It contains a fluid called nucleoplasm, chromatin, and
nucleoli.
• The nucleus is the control center of the cell
because it contains the genetic material,
deoxyribonucleic acid (DNA), which directs cell
activity through protein synthesis.
Fig. 4.43
Nuclear Envelope
• The nuclear envelope is composed of two
layers, an inner and an outer phospholipid layer.
Small openings, the nuclear pores, are
distributed throughout the membrane. Nuclear
pores make the membrane selectively
permeable.
• The large molecules, DNA, are restricted to the
nucleus whereas small molecules such as
nucleotides, small proteins, and ribonucleic acid
(RNA) move freely across the membrane.
Fig. 4.44
Chromatin
• Chromatin is composed of
DNA and associated proteins
called histones and appears as
threads distributed throughout
the nucleus. Portions of the
DNA and histones become
arranged into organizational
structures called nucleosomes.
Inactivation of genes is
partially controlled by the
selective wrapping of portions
of the DNA.
• During cell division (mitosis
and meiosis) the chromatin is
further condensed into
structures called
chromosomes. This
packaging of the DNA into
chromosomes facilitates its
distribution to daughter cells.
Fig. 4.45
11
Chromatin & Chromosomes
Fig. 4.46
Fig. 4.47
Photograph of a cell (of whitefish
blastula, 1,000x) seen through a light
microscope showing threads of
chromatin.
Photograph of a cell (of whitefish
blastula, 1,000x) seen through a light
microscope showing chromosomes of
the mitotic phase, metaphase.
NUCLEOLI
• The nucleus may have a single
nucleolus or many nucleoli.
They appear as dark-stained
nuclear regions and are
associated with chromatin that
is active in the synthesis of
ribosomal RNA.
• At the nucleolar regions the
ribosomal RNA is combined
with proteins to make the
subunits of ribosomes. The
ribosomal subunits leave the
nucleus and enter the
cytoplasm where they
assemble into ribosomes.
• Since ribosomes are the sites
of protein synthesis, cells that
are active in protein synthesis
usually have several nucleoli.
MITOCHONDRIA
Mitochondria are cytoplasmic organelles that typically
appear rod-shaped or filamentous.
• The mitochondrion is bounded by a double membrane.
– The outer membrane surrounds the mitochondrion forming its
outermost boundary.
– The inner membrane folds deeply into the mitochondrion's
interior forming shelf-like partitions called cristae.
– The substance within the interior of the mitochondrion is called
the matrix.
– Mitochondria have their own DNA.
Fig. 4.49
Lab Activity 12 –
Mitochondria
• Obtain a prepared microscope slide labeled
“Mitochondria (Amphiuma liver).” Mitochondria (1,000x)
from the liver of Amphiuma (salamander). The
mitochondria appear granular, rod-shaped, and
filamentous.
Fig. 4.51
Fig. 4.48
Cell Respiration
•
Mitochondria function as the "powerhouses of the cell," in that
they produce most of the cell’s ATP. Aerobic respiration, which
generates most of the cell's energy-rich molecules (ATP), occurs
within the mitochondria. The two catabolic processes of
mitochondrial metabolism are Kreb’s cycle and the electron
transport system. In the catabolism of a molecule of glucose, 24 of
the 36 energy rich ATPs produced are derived from Kreb’s cycle and
the electron transport system of the mitochondrion.
Fig. 4.50
RIBOSOMES
• A ribosome is a very small organelle that consists of a
large and a small subunit. The subunits are composed
of a ribonucleic acid (RNA) called ribosomal ribonucleic
acid (rRNA) and proteins. The rRNA originates by
transcription from DNA in the nucleolus. It is then
combined with proteins to form the subunits which leave
the nucleus by way of the nuclear pores.
•
Ribosomes are found either attached to membrane
channels called the endoplasmic reticulum or are free in
the cytoplasm.
Fig. 4.52
12
Ribosomes – Protein Synthesis
• Ribosomes are described functionally as the sites of
protein synthesis. They receive protein coding
information transcribed from DNA in the form of another
type of ribonucleic acid (RNA) called messenger
ribonucleic acid (mRNA). The coding information
(mRNA) is then translated with the assembly of amino
acids to form proteins.
Ribosomes – Protein Synthesis
• Free ribosomes produce
proteins that become a
part of the cytosol.
• Attached ribosomes
release their proteins into
the endoplasmic
reticulum. In the
endoplasmic reticulum
the proteins may be
modified before they are
packaged into small
membranous sacs called
vesicles.
Fig. 4.53 Free Ribosome
Fig. 4.55 Attached Ribosome
Fig. 4.53
ENDOPLASMIC RETICULUM (ER)
•
The endoplasmic reticulum is structured as a
network of membranes which form fluid filled
channels. The endoplasmic reticulum (ER) is
distributed throughout the cytoplasm and usually
interconnects the nuclear and plasma
membranes.
•
Two types of endoplasmic reticulum can be
described depending upon the association with
ribosomes.
– Rough ER
• If ribosomes are attached to the endoplasmic reticulum,
rough (granular) endoplasmic reticulum (rough ER) is
formed.
– Smooth ER
• If ribosomes are not attached, smooth (agranular)
endoplasmic reticulum (smooth ER) is formed.
Rough ER & Transport Vesicle
•
Polypeptides produced at the ribosomes on the
rough ER membrane move into the endoplasmic
reticulum’s cavity (cisterna). Once in the ER’s cisterna
the polypeptides may be modified before being pinched
off in a membranous sac called a transport vesicle.
Transport vesicles mostly move the polypeptides to the
Golgi apparatus for processing.
Fig. 4.55
Endoplasmic reticulum (ER) is structured as a network of membranes
that form fluid filled channels. When ribosomes are attached, the
endoplasmic reticulum is described as rough endoplasmic reticulum
(rough ER). Otherwise the endoplasmic reticulum is described as smooth
endoplasmic reticulum (smooth ER).
Smooth ER
• Endoplasmic reticulum without ribosomes is smooth ER
and is often seen extending from the rough ER.
• The membranes of smooth ER contain proteins that
function as enzymes and mediate reactions that include
the production and modification of lipid and
carbohydrate molecules such as: phospholipids,
glycolipids, steroids, lipoproteins, glycogen, and fatty
acids.
• In skeletal and cardiac muscle smooth ER, known as the
sarcoplasmic reticulum, regulates the release of ionic
calcium. Ionic calcium functions as the trigger for the
interaction of contractile proteins that produce
contraction.
Fig. 4.55
13
Golgi Functions
GOLGI APPARATUS
• The Golgi apparatus is located near the
nucleus and consists of several to many
groups of flattened membranous sacs
stacked one upon the other.
•
The Golgi apparatus functions in the modification,
concentration, and packaging of various molecules (such
as polypeptides) that are received from transport
vesicles arriving from the rough ER.
• Small membrane sacs called vesicles transfer materials
to and from the Golgi apparatus.
• Delivery of polypeptides to the Golgi apparatus is by
transport vesicles that originated from the rough ER.
• The polypeptides are processed and packaged into
vesicles for three possible destinations:
– Secretion
– Membrane structure
– Lysosomes
Fig. 4.57
Fig. 4.56
Destinations of Transport Vesicles
Destinations of Transport Vesicles
• Secretory vesicles
– Secretory vesicles transport proteins to the plasma
membrane for exocytosis.
• Membrane-bound vesicles
– Membrane-bound vesicles deliver proteins to the
plasma membrane for incorporation into the
membrane
• Lysosomes
– Lysosomes (storage vesicles) contain proteins that
participate in intracellular functions; lysosomes
function in intracellular digestion.
Fig. 4.58
CENTROSOME AND
CENTRIOLES
LYSOSOMES
• Lysosomes are vesicles (storage vesicles) produced
by the Golgi apparatus. They contain digestive
(hydrolytic) enzymes which function in the digestion of
a variety of materials such as worn-out organelles,
inclusions such as glycogen, and particles engulfed by
phagocytosis.
• When particles are engulfed they are surrounded by a
portion of the plasma membrane and form a structure
called a phagosome.
• Lysosomes fuse with the phagosome and release their
digestive enzymes which digest the phagosome’s
contents.
•
Located near the nucleus, the centrosome is
an area of cytoplasm which contains a pair of
cylindrical structures called centrioles. The
centrosome functions as an organizing center in
the nondividing cell.
•
The paired centrioles of the centrosome are
positioned at right angles to each other and
each is composed of a group of small tubules
called microtubules arranged in nine triplets.
Fig. 4.59
14
CILIA AND FLAGELLA
CENTROSOME AND CENTRIOLES
• In the dividing cell, the centrioles function by acting as
the centers from which microtubules (spindle fibers)
originate. Microtubules (spindle fibers) function in the
organization and movement of the chromosomes during
cell division. Cells, such as nerve cells, which lack
centrioles cannot divide. Centrioles are also located at
the bases of cilia and flagella and form their basal
bodies.
•
Cilia and flagella are cellular
projections composed of microtubules and
surrounded by the plasma membrane.
Their micotubule pattern consists of nine
outer pairs and one central pair.
Fig. 4.60
Fig. 4.61
Fig. 4.62
Cilia
• Cilia are observed as short numerous extensions from
the exposed surface of ciliated cells.
• Cilia function in the movement of materials (such as
mucus) over the surface of the cells. The airways of the
respiratory tract are lined with ciliated cells
(pseudostratified ciliated columnar epithelium) which
move mucus away from the lungs.
Fig. 4.63
Flagella
• A flagellum has the same microtubule structure
and basal body association as a cilium. A
flagellum differs from a cilium in that a flagellum
is much longer and exists singly on the only
flagellated cell of the human, the sperm cell.
Fig. 4.64
INCLUSIONS
• Cell inclusions include a wide variety of chemical
substances and/or foreign bodies within the cell.
•
Inclusions are usually either membrane bound
in vacuoles or exist as undissolved substance in
the cytoplasm. Some common inclusions are lipid
droplets (stored lipid), glycogen granules (stored
glucose), and melanin granules (dark brown or
black pigment).
Fig. 4.65
Fig. 9.15
15