Histology - Introduction:
Main types of microscopy:
Electron microscopy:
High magnified and small sections are viewed.
1. Transmission EM – Thin sections and electrons pass through onto a film. It is two-dimensional and
in black and white.
2. Scanning EM – Specimen coated with metal. It is three-dimensional and in black and white.
Light microscopy:
Thin slices of specimen stained and mounted on a slide, a light is shone through and specimen is
magnified.
As magnification is not very high, larger sections can be magnified.
Different stains reveal different characteristics and different colour images.
Used to look at basic cell and tissue architecture.
In studying the human body, it helps to recognize the levels of organization that make it up:
Atoms
Molecules
Macromolecules
Organelles
Cells
Tissues
Organs
Systems
Body (organisms)
Histology means “the study of tissues”.
A tissue is a group of similar cells and their intercellular substance functioning together to perform a
specialized activity.
Histology deals with the study of organs at the tissue level, what types of tissues make up the organs and why. It
will also refer to the cellular level frequently and therefore requires a solid basic knowledge of this from
physiology. A basic knowledge of the structure and function of the 11 body systems is also necessary.
There are foUr categories of tissues, called primary tissues. These are:
Epithelium – Tissue that covers body surfaces and lines cavities, and forms glands.
Connective tissue – Protects and supports and binds.
Muscular tissue – Responsible for movement (smooth, skeletal and cardiac).
Nervous tissue – Initiates and transmits nerve impulses that coordinate body activity.
,The cell:
The cell is the structural unit of the body. There are many different designs of cells you will learn about this year,
but each design is based on certain basic features, which then get amplified or specialized according to the
specialization of the cell concerned. They all have a plasma membrane, in which is located in cytoplasm. In the
cytoplasm are several different organelles, and inclusions, which are amplified according to the cellular
function.
The mitochondria: All cells receive oxygen and glucose. From these, it needs to manufacture its own energy
currency (ATP). It is the mitochondria that produce ATP. They are called the powerhouses of the cell.
The rough endoplasmic reticulum: RER and ribosomes are the site of protein production. It is here that the
amino acids chains forming proteins are constructed.
Cytoskeleton: An arrangement of microfilaments and microtubules which make up and internal cellular
scaffolding to maintain cellular shape. Can be disassembled and reassembled when necessary. The
myofilaments actin and myosin are contractile.
The nucleus: The control center of the cell where the plans and protein “recipe” for bodily design and function
are stored in the form of DNA. Surrounded by nuclear envelope. Some cells are multinucleate, and others
anucleate (no nucleus).
Golgi complex: A set of flattened membranes stacked on top of one another are the site where the final
packaging of proteins takes place. The packaged proteins bud off the sides of the Golgi, and are either used
internally, or secreted for external use.
Lysosomes: These are membrane bound packages of digestive enzymes. They are used to break down ingested
elements or to break down the cell itself when it dies.
Smooth endoplasmic reticulum: SER is the site of lipid synthesis, and sometimes calcium storage.
Inclusions: Storage areas in the cell where certain substances are kept for future use. Generally not membrane
bound, but simply located in between endoplasmic reticulum for example. May include lipids, glycogen, or
products to be secreted.
The plasma membrane: The membrane that surrounds all cells is very important. It surrounds the contents of
the cell, protecting the internal environment. It determines a lot of what may cross into the internal
environment. It contains receptors for chemical messengers, and protein tags for identification. There are
channel proteins, and intercellular adhesions found in the cellular membrane. It is via this membrane that a cell
must interact with the extracellular environment, and therefore any specializations of this membrane reflect its
external activities, for example, microvilli to increase surface area for absorption or secretion, pumps for
pumping ions in or out, or cilia to move fluids across the surface of the cell. Essentially composed of two layers
of phospholipids.
Staining of cells:
Stains or dyes are used to reveal features of cells and tissues for microscopic study. They can help us to
understand structure, composition and function of secretions being studied.
There are two main types of dye:
1. Basic dye: It is a commonly used basic dye that stains blue. Hematoxylin.
2. Acidic dyes: it is a commonly used acidic dye that stains pink or red. Eosin.
Structures that attract a basic dye are called “BASOPHILIC”. These are usually structures that themselves are
acidic. DNA in the nucleus or RNA on RER.
,Structures that attract an acidic dye are called “ACIDOPHILIC” (or often “eosinophilic” as this is the most
common acidic dye). These are usually structures that themselves are basic. Lysosomes, SER, mitochondria or
protein.
Nuclei will always stain basophilic (blue) but the overall stain of the rest of the cell will depend on which
organelles are most dominant (numerous). So if a cell has a function that amplifies a particular organelle, then
this will determine its staining characteristics. For example, osteoclasts are packed with lysosomes so they are
eosinophilic. Pancreatic cells produce protein enzymes and then store them intracellular in the apices of the
cells, they have basophilia in the basal region and eosinophila in the apical regions.
In addition to organelles, inclusion can also affect staining. For example, if a cell had glycogen, then the
cytoplasm will be pale and patchy where glycogen is stored.
Organelle: Function: Staining characteristics:
Nucleus Controls cells Basophilic (has DNA) Will be prominent I protein-producing cells (those
secretions collagen, protein hormones, and enzymes.
Note: Diploidy and polyploidy are usually not linked to
origin, and not function.
RER Site of protein Basophilic (has of RNA) Amplified in protein producing cells.
synthesis
Golgi Packages Acidophilic May be amplified in protein producing cell, but not
apparatus proteins much effect on staining capacity.
SER Produced Acidophilic Amplified in cells producing lipid hormones, as well as
lipids, stores being very extensive in muscle.
calcium in
muscle
Mitochondri Produce ATP, Acidophilic Amplified in cells that consume a lot of energy (muscle,
a and the energy or cells pumping ions against a concentration gradient).
currency of the
cell
Lysosomes Contain lytic Acidophilic Amplified in phagocytic like cells, but if debris present,
enzymes then debris takes on a dark stain.
Inclusion: Function: Staining characteristics: Found:
Glycogen Storage form of glucose Pale patchy areas Muscle and liver cells
Hemoglobin Found in red blood cells, Eosinophilic Red blood cells
carries Co2 around the body
Lipid Storage of fat or energy Pale patchy areas Adipocytes and liver cells
Protein (zymogen granules) Eosinophilic Protein producing cells e.g.
enzyme producing cells
,Histology - Epithelium:
As stated, epithelium is a sheet of cells which forms a covering, or lining for a body cavity. So it always lies on
a free surface. The cells are closely aggregated with minimal intercellular substances, and the cells are bound
firmly.
Most epithelia rest on a basement membrane, which separates it from the underlying connective tissue. In this
connective tissues are the blood vessels that supply nutrition to the epithelium and drain away wastes. The
epithelium itself is avascular (no blood vessels), and relies on diffusion from the underlying tissues.
Epithelia often perform specific functions, and we will study these in detail as we go along. Besides just forming
a covering, they are involved in protection of surfaces subject to mechanical abrasions or chemical danger,
they are involved in secretion, absorption, and specialized functions like olfaction and sperm production.
Epithelia also form all glands in the body.
Classification:
Epithelia is classified according to:
1. Number of cell layers:
One layer = simple
More layers = stratified
Pseudo stratified = an epithelium which appears to have many layers of cells but in fact all cells are in
contact the basement membrane . It only has one layer of cells but looks like many layers. There is many
goblet cells and nuclei.
2. Shape of surface cells:
Flat plate like (width > height) = squamous
Square (height = width) = cuboidal
Oblong (height > width) = columnar
3. Presence of any specializations:
Goblet cells – secrete mucous for moisture, protection against acid and to trap foreign particles
Cilia – beat in a wave like motion to move mucous
Microvilli – folds in plasma membrane to increase surface area for absorption
Keratin – Hard waterproof material for protection
Basal infoldings – increase basal membrane for absorption and mitochondria for energy
Specializations of epithelia:
Keratinization: Keratin is a tough proteinaceous material. It is resistant to mechanical injury and also
provides protection against bacterial invasion, water loss and chemical insults. Part of the keratinization
process involves death of the cell becoming keratinized. This process only happens in Stratified squamous
epithelium. The lower cells undergo mitosis, and as they are pushed upwards they undergo keratinization
(involves lysosomes rupture). In this way, the surface layers of cells are dead and filled with keratin. They are
constantly being shed and replaced by the continued process of mitosis and keratinization occurring below.
Under the light microscope stratified squamous epithelium can be identified as keratinized if the nuclei are
missing in the upper layers (indication of earlier death). Skin, hair, and nails.
Microvilli: Microvilli are miniature finger-like projections of the apical (top) plasma membrane, filled with
cytoplasm. They are non-motile, and function simply to increase the apical surface membrane, generally for
absorption, but sometimes for secretion. May occur singly, but epithelium is only classified as having microvilli
if they are fairly numerous. Under the microscope they appear as a fuzzy border on the surface of the cell (made
clearer by winding the fine focus back and forth). This is called a “striated border”. In the kidney tubules,
where they are involved in reabsorbing fluid filtered at the corpuscle, they are called a “brush border”.
,Cilia: Cilia are larger finger-like projections of the apical plasma membrane, which enclose microtubules
arranged in 9+2 configuration. These microtubules make the cilia motile. Groups of cilia beat in a rhythmical
fashion, moving a thin layer of fluid across the surface of epithelium. Cilia are numerous in the respiratory
tract where they trap foreign particles and beat to remove them. They are also found in the oviduct to move
the ovum along. Please note that cilia are delicate hair-like structures and incapable of moving larger volumes.
Food in the gut is moved by peristalsis, and cilia aren’t located here.
Basal infoldings: Deep infoldings of the basal (bottom) plasma membrane. Generally associated with tall
mitochondria that lie between the folds. This gives the appearance of “basal striations”. The folds increase
surface area and mitochondria provide energy. Found in epithelia active in fluid and ion transport. Found in
kidney tubules and salivary ducts.
Goblet cells: Goblet cells are secretory cells. They have an expanded apex filled with secretory droplets and a
narrow base with a dense nucleus. This gives the cells the appearance of a goblet. They secrete mucin that
outside the cell combines with water to form mucous. Mucous forms a mechanical barrier over the epithelium.
This has different functions depending on the location:
It always acts as a mechanical barrier preventing the entry of harmful microorganisms.
In addition it can trap larger particles such as dust and sand. This function is important in the
epithelium lining the respiratory tract.
It can also protect against acid and digestive enzymes. This function is important in the epithelium
lining he digestive system.
Lubrication.
Goblet cells are only found in simple columnar epithelium and pseudo stratified columnar epithelium. In
stratified epithelium, surface mucous has to be secreted by glands found under the epithelium that send ducts
up to the surface.
There are epithelia that don’t fit into this scheme of classification, and these are referred to as “specialized
epithelia”. You will come across these, and they have their own names. Examples include:
1. Visceral layer of Bowman’s capsule – The visceral epithelium of Bowman’s Kidney is made of
specialized cells called “podocytes”. Podocytes have extensive process that wrap around the glomerular
capillaries to help urinary filtration.
2. Seminiferous epithelium – The epithelium in the seminiferous tubules of the testes where sperm
production takes place.
3. Transitional epithelium – The epithelium lining the bladder that must be able to accommodate stretch
as well as the toxicity of urine.
Simple squamous epithelium:
Single layer of very flat thin cells. Large centrally located nucleus.
Locations and functions: This kind of epithelium is not suited to protection, but is very good for diffusion.
Therefore found in alveoli of lungs where gaseous exchange occurs. Also found lining heart and blood
vessels where nutrients and oxygen diffuse out into tissues, and carbon dioxide and wastes diffuse back into
blood vessels. Because it is so flat and smooth, it helps to promote smooth blood flow, and reduce friction. In
the circulatory system it is referred to as “endothelium”. It lines the serous membranes surrounding the heart
(pericardium), the lungs (pleura) and gut (peritoneum). Here it secretes serous fluid that acts as a lubricant.
Lining serous membranes it is called “mesothelium”.
Simple cuboidal epithelium:
Single layer of cube-shaped cells with a round central nucleus.
,Locations and functions: Found making up the thyroid gland where it secretes the thyroid hormones. Found in
the kidney tubules where it is involved in regulating formation of urine.
Simple columnar epithelium:
Single layer of tall column shaped cells. Nuclei oval and at base. Specialization according to functions.
Locations and functions:
Simple columnar with goblet cells and cilia: Found in the respiratory tract. The goblet cells secrete mucous
to trap foreign particles, and the cilia beat to remove mucous plus particles.
Simple columnar with goblet cells and microvilli: Found in the digestive tract. The goblet cells secrete
mucous to protect gut lining from enzymes and acid. The microvilli increase surface area to absorb nutrients
from food.
Pseudo stratified columnar epithelium with goblet cells and cilia:
Only one layer of cells, but nuclei on several levels giving the impression of many layers. Functions are the same
as simple columnar with goblet cells and cilia, but as it is thicker, it is a bit more protective.
Stratified squamous epithelium:
Many layers of cells, with nuclei that undergo changes. Start at the bottom being tall, but they get progressively
flatter. Bottom layers are continually undergoing replication (mitosis), and cells move slowly up, and sloughed
off at the surface, so there is a continual rejuvenation.
Locations and functions:
Not suited for secretion or diffusion, but is suited for protection.
Stratified squamous non-keratinized epithelium: Found on wet surface. Mouth, esophagus, vagina and
cornea.
Stratified squamous keratinized epithelium: Keratin is tough protein that increases protection and is
waterproof. Found on the skin.
Transitional epithelium:
Found lining the urinary system. Several layers of polygonal cells, and surface cells are large and bulging and
often contain more than one nucleus. It can stretch to accommodate urine.
Relaxed state: 4-5 layers thick
Stretched state: 2-3 layers thick
,Histology – connective tissue:
Connective tissue is the term applied to tissue that provides both structural and metabolic support for other
tissues and organs in the body. It occurs in many different forms with a wide range of physical properties. Some
connective tissues must be loose in order to form a packaging material. Others have to be rigid in order to form
the skeletal framework. In addition to the supportive, binding and protective function of connective tissues,
there are several metabolic functions. The metabolic functions include being a medium for transport or
diffusion of nutrients and wastes. It also includes storage of fat, and housing numerous cells of the
defense system. It is also greatly involved in the function of tissue repair. It includes tissues known as
“connective tissue proper”, as well as cartilage, bone and blood.
The three elements of connective tissue:
Almost all connective tissues have a ground substance in which one finds cells and extracellular fibers.
1. The ground substance:
The ground substance is made up of fluids and organic material. It occupies all the spaces between the
cells and fibers, and functions principally as a medium through which nutrients and waste products
can diffuse between cells and capillaries. It is mainly the ground substance that will determine the
physical properties of the different types of connective tissue. In addition the state of the ground
substance subdivides connective tissues into three categories:
Connective tissue with a semi-solid ground substance (connective tissue proper).
Connective tissue with a solid ground substance (cartilage and bone).
Connective tissue with a fluid ground substance (blood).
2. The extracellular fibers:
There are three fiber types found in connective tissues:
Collagen – Collagenous fibers are found in all types of connective tissue. Collagen is a very tough
protein, and the presence of collagen fibers gives strength to the tissue. Collagen fibers stain pink
(eosinophilic). In the fresh state they are white, and so sometimes these fibers are referred to as white
fibers. The secretory cells (fibroblasts and chondroblasts) will secrete tropocollagen. Tropocollagen,
once outside the cell will form collagen.
There are five different types:
Type I – 90% of collagen in body. Tropocollagen fibers aggregate to form strong bonds. Arranged in
bundles that have tremendous tensile strength. Found in tendons, ligaments, bone, areolar, and skin. Can
be arranged in parallel or irregularly. Bundles show faint longitudinal striations due to their component
fibrils.
Type II – Fine fibrils dispersed in the ground substance. In cartilage.
Type III – Called “reticular fibers”. Delicate meshwork of fine, short branching fibrils. In this form has
affinity for silver salts, stains black. Only visible in this stain. Present surrounding and supporting cells
(especially in very cellular organs like in the liver), as well as vessels, nerves, muscle fibers, and fat cells.
Type IV and V – Don’t form fibrils. Incorporated into tissues as proteins.
Elastin – Can be arranged as fibers or sheets, to give, elasticity to the tissue. Can be stretched and
return to their former length. Also branch to form a network. Stain darkly (although only displayed by
specific stains), and when relaxed, coil into loose spirals.
Structural glycoproteins – Glycoprotein molecules that group to form fibers.
3. Cells:
,Secretory cells – Fibroblasts or fibrocytes
Storage cells – Adipocytes
Defense cells – Any of the blood leucocytes
Fibroblast or fibrocytes:
Fibroblasts are the cells that secrete the fibers and matrix or ground substance. They are large
spindle-shaped (building central belly and tapering ends) with branching ends. They have an
elongated nucleus that is easily seen (cytoplasm doesn’t stain well).
When fibroblasts are surrounded by secreted material, they become dormant (but still very much
alive). Their nucleus pulls in and becomes darker staining. In this dormant state they are called
‘fibrocytes”. Fibrocytes remain in the area in case there is a need for growth or repair such as wound
healing. In this case, they revert back to their fibroblast state.
Adipocytes:
Adipocytes are cells specialized to store lipids. The lipids accumulate in the cytoplasm and coalesce
into large spherical droplet that pushes the cytoplasm and nucleus to a thin rim around the periphery.
Because the cells are fairly large, the nucleus doesn’t always show when the cell is sectioned.
Adipocytes can occur singly or in small groups. If they occur in large numbers, the tissue is
transformed into adipose tissues.
The blood leucocytes:
The blood leucocytes, also referred to as “white blood cells”, are all involved in some kind of defense.
Any of these cells can occur in connective tissue:
Leucocytes
Granulocytes Agranulocytes
Neutrophils Eosinophils Basophils Monocytes Lymphocytes
Neutrophils: These cells are active and mobile phagocytes and move quickly into any area of
inflammation. They are recognized by their multi-lobed nucleus. They have granules that stain palely.
Eosinophils: These cells are important in cleaning up in any inflammatory reaction, and are often
seen in the lactating breast and gut, and are associated with parasitic infections. They have a bi-loped
nucleus and eosinophilic granules.
Basophils: Basophils of the blood are the “mast cells” of connective tissue. They contain two very
important physiological substances: Heparin (an anti-coagulant) and histamine (a chemical
mediator of inflammation released in tissue injury). Mast cells are filled with basophilic granules
that obscure they nucleus in light microscopy.
Monocytes: The monocytes of the blood are the “macrophages” of connective tissue. As their name
suggests, they are large eating cells, and function in removing pathogens as well as debris from tissue
breakdown. They have an amplification of lysosomes and are therefore eosinophilic. They are difficult
to identify unless they have ingested material. They can be attached to fibers in specific organs (referred
to as “fixed” macrophages) or roam freely around the body (known as “free” macrophages”).
Lymphocytes: Lymphocytes are the cells involved in “specific defense” where each cell is only capable
of “recognizing” one particular pathogen . They have a nucleus that almost fills the cell, resulting in the
, cell looking like a dark circle in light microscopy. They are numerous in CT of the digestive and
reparatory system and make up the pulp of lymphatic organs such as the lymph nodes.
Connective tissue proper:
Loose irregular connective tissue (areolar):
Areolar connective tissue is often considered to be the prototype of connective tissues. This is because it has
all fiber types, and can have any of the cell types previously described. Collagen fibers are most abundant,
and there are also numerous reticular, and elastic fibers. It has many cell types including fibroblast,
fibrocytes, macrophages, mast cells and lymphocytes. The most numerous are the fiber secreting cells in
their active (fibroblast) as well as dormant (fibrocyte) state. Macrophages are also numerous though often
difficult to identify under the light microscope. Mast cells may be encountered, often ruptured with their
granules in the matrix. As this is the packaging and anchoring material of the body (surrounds all structures
and helps to support and protect them), it is found in almost every microscopic section of the body. It is
found surrounding nerves, blood vessels, and lymph vessels.
Dense regular connective tissue:
Collagen is the main fiber type, (although other fiber types will be found surrounding bundles of collagen
fibers). The collagen fibers are arranged in very regular rows with fibroblasts and fibrocytes in between. The
collagen fibers group into primary bundles covered by a small amount of connective tissue referred to as
endotendinium. Several primary bundles are grouped into secondary bundles called fascicles bounded by
connective tissue called peritendinium. Several fascicles make up the tendon itself, and is ensheathed by thick
connective tissue called epitendineum. Nerves and vessels will run in the connective tissue septa. This
arrangement of collagen makes this tissue extremely strong (has particularly great tensile strength), and so it
forms tendons, ligaments and aponeuroses.
Adipose tissue:
Made up of masses of adipocytes (cells with large fat vacuole, and nucleus and cytoplasm displaced to the
periphery). Each adipocyte is surrounded by a web of reticular fibers, in which one comes across fibroblasts,
fibrocytes, and lymphoid cells. The adipocytes pack together to form lobules. Collagenous fibers form fibrous
septa separating the lobules. Here one finds a rich network of blood capillaries (adipose is extremely vascular
tissue).
This tissue stores fat for energy, it acts as a shock absorber, and an insulator. It can develop anywhere where
areolar tissue is plentiful. Plentiful in subcutaneous tissue, mesenteries, bone marrow, around the kidney, and in
the breasts.
Too much adipose = great increase in vascular bed:
1. Heart must work harder = cardiac problems
2. Damage in a car accident / surgery = higher risk of excessive bleeding
Cartilage:
Cartilage is classified under “connective tissue with a solid matrix”. It is not as solid as bone, and is therefore
more cushioning and in some cases elastic. However, like bone it is specially adapted to provide support. It is
able to withstand considerable pressure and shearing forces.
The main cell of cartilage are called chondrocytes, which come from chondroblasts. As there is a solid matrix,
the chondrocytes are located within lacunae (spaces) in the matrix. There are no blood vessels in the matrix,
and the chondrocytes rely on diffusion in order to get their nutrients, and get rid of wastes. The fibers are
imbedded in the matrix. A perichondrium of connective tissue may be present at the edge of the cartilage
matrix. This is where chondroblasts would arise from. There are three types of cartilage have different physical
properties due to difference in abundance and type of fibers present:
1. Hyaline: Most common. Nasal cartilages, larynx, trachea and bronchi, sternal ends of ribs and on
articular surfaces (also in endochondral ossification – growing ends of long bones).
, 2. Fibrous: Found in the intervertebral discs, knee meniscus, pubic symphysis, glenoid fossa and
acetabulum.
3. Elastic: Found in the external ear, epiglottis, and Eustachian tubes.
The development of cartilage:
Cartilage is formed in primitive connective tissue called mesenchyme. Some of the cells become specialized for
secreting cartilage matrix called “chondroblasts”. Chondroblasts divide, increasing in number, and they secrete
the cartilage matrix and fibers. The secretions trap individual chondroblasts, separating them from each other.
These cells enlarge and mature forming chondrocytes. New chondroblasts develop at the periphery. The older
cells in the center keep enlarging and also divide, giving rise to cell nests called “isogenous groups”. This
accounts for the younger cartilage cells being flattened and located at the periphery, whilst the older
cells are hypertrophied located towards the center, and in cell nests.
From the above we can also understand the two types of cartilage growth referred to as appositional growth
and interstitial growth.
1. Appositional growth: The growth on the edge of the cartilage that occurs as a result of the
development of new chondroblasts, and their secretions.
2. Interstitial growth: The growth in the center of cartilage that occurs as a result of the divisions of the
chondrocytes and their secretions.
Hyaline cartilage:
A solid matrix with collagenous fibers (which cant be seen under the microscope as collagen and the matrix
have similar refractive indices). Has numerous lacunae containing the chondrocytes. Young cells are located
to the periphery, and are flattened with their long axis parallel to the surface. Older cells in the center are
hypertrophied and lie in cell nests or isogenous groups. (Chondrocytes undergo shrinkage during
preparation). The matrix is modified around each lacuna to form a cartilage capsule, and around isogenous
groups to form territorial matrix. In between groups the matrix is referred to as interterritorial
perichondrium, absent in articular cartilages. Lacks blood vessels and nerves.
Elastic cartilage:
Elastic cartilage has exactly the same arrangement as hyaline cartilage. The only major difference is that in
addition to collagen fibers, it also contains numerous elastic fibers. These elastic fibers can only be seen
when specifically stained for. Failing this, elastic cartilage will look like hyaline cartilage under the light
microscope. When specifically stained, the elastic fibers are numerous and black and are also seen to
concentrate in the regions of territorial matrix.
Fibrocartilage:
Fibrocartilage doesn’t develop in exactly the same manner as hyaline and elastic cartilage. It doesn’t
demonstrate hypertrophy of chondrocytes or cell nests. Rather it resembles dense regular connective tissue.
It of course has a solid matrix, and this permeated with many collagen fibers arranged in dense regular
parallel rows, orientated in the direction of the stress. All chondrocytes and lacunae are the same size, and
arrange in very regular rows between the fibers. Perichondrium absent.
Features: Hyaline: Fibro:
Shape of Small and flattened Large and round
chondrocytes
Arrangement of Lie in nest cells In very regular rows
chondrocytes
Arrangement of Irregular In dense regular parallel rows
fibers
Perichondrium Surrounds the cartilage, absent in Absent
articular
