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BIOLOGY 165 HISTOLOGY LAB MANUAL
NOTE: You may be asked to identify any structure, cell, tissue, or organ labeled in the figures/pictures within
this lab manual. In addition, you may be asked to name one function of each labeled item and one location
within the human body where it can be found. You are only responsible for the specific information contained
within this lab manual.
INTRODUCTION
Cells are the smallest units of life, and are named according to their function. Cells are arranged in organized
groups called tissues that carry out specific functions. Tissues are organized together to form organs, which
carry out more complex functions. Organs work together in groups to form systems, which in turn carry out
higher order functions. Systems make up the individual organism.
There are four basic types of tissues we will identify in the lab. These tissue types are epithelial tissues
(epithelia), connective tissues, muscular tissues, and nervous tissues.
EPITHELIAL TISSUES
1. There are two basic types of epithelial tissues:
a. Covering and lining epithelia.
i. Forms the outer covering of:
1. External body surfaces.
2. Some internal organs.
ii. Lines the interior of body and organ cavities:
1. Respiratory tract.
2. Gastrointestinal tract.
3. Blood vessels.
4. Reproductive tract.
5. Urinary tract.
b. Glandular epithelia.
i. Makes up the secreting portions and ducts of exocrine glands.
2. Epithelia are classified based on two things:
a. The number of cell layers between the basement membrane and the free (apical) surface.
Sometimes, the free surface faces the hollow cavity of and organ or tube; the hollow space
within these structures is referred to as a lumen.
i. 1 layer of cells = simple epithelium.
ii. More than 1 layer of cells = stratified epithelium.
b. The shape of the cells at the free surface:
i. Squamous (flat).
ii. Cuboidal (cube-shaped).
iii. Columnar (column-shaped).
3. Varieties of epithelia:
a. By using the classification scheme described in (2) above, the following combinations are
possible:
i. Simple squamous epithelium.
ii. Simple cuboidal epithelium.
iii. Simple columnar epithelium.
iv. Stratified squamous epithelium.
v. Stratified cuboidal epithelium.
vi. Stratified columnar epithelium.
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b. There are two additional epithelial tissues that do not neatly fit into the classification scheme
described above:
i. Pseudostratified columnar epithelium (with or without cilia at the free surface).
ii. Transitional epithelium.
As the figure below shows, all epithelial tissues adhere to a connective tissue membrane layer referred to as the
basement membrane. The basement membrane attaches the epithelium to the underlining connective tissues.
This figure depicts a simple columnar epithelium.
1. Simple Squamous Epithelium
As the diagram below and photomicrograph (on the next page) illustrates, this tissue consists of a single layer of
flat (squamous) cells, which resemble fish scales or fried eggs in a frying pan. The slide you are looking at in
lab has only simple squamous epithelium on it, so it is easy to find and identify.
Description: A single layer of flat cells. Looks like a platter of fried eggs "sunny-side up".
Location: Air sacs (alveoli) of lungs, lining the inside of the heart and blood vessels.
Function: Filtration, diffusion, osmosis.
Seen below: a drawing of simple squamous epithelium, showing its superior and lateral aspects.
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Seen below: light photomicrograph of simple squamous epithelium – superior aspect, frog skin (400X).
In this view the lumen associated with epithelium cannot be seen, as the viewer is looking down on the top
(superior aspect) of the tissue. Notice how the nucleus of each cell is clearly visible as a dark staining structure,
and how the cell membranes of each cell define their borders.
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2. Simple Cuboidal Epithelium
As the drawings and photomicrographs illustrate below, this tissue consists of a single layer of cube-shaped
cells. The slide you are looking at in lab is a slide of the kidney. This slide has many different types of tissues
on it, so it may take some work to find something similar to what is shown below.
Description: A single layer of (approximately) cube-shaped cells.
Location: Lining kidney tubules and the small ducts of many exocrine glands.
Function: Secretion and absorption.
Seen below: drawing of simple cuboidal epithelium showing its superior and lateral aspects.
Notice the central location of the nucleus within each cell in this
tissue (the distance from the nucleus to the top and bottom of cell is
about equal). The drawing gives the impression that this tissue is
cube shaped, when in fact it is more polyhedral in shape.
Seen below: light photomicrographs of simple cuboidal epithelium – from ducts within the kidney (40X [left]
and 400X [right]).
In this view of the kidney (left), a renal papilla can be seen. It is the nipple-like projection extending downward
and to the left. At this low magnification (40X) the ducts, which are lined with simple cuboidal epithelium, can
barely be seen. In the view on the right (400X), the kidney ducts are clearly seen. Note that the simple
cuboidal epithelium faces the lumen (inner space) of the duct. Each cuboidal cell is roughly cubed shaped with
a centrally located nucleus.
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3. Simple Columnar Epithelium
On this slide you must sometimes differentiate the liver from the gallbladder in order to locate the simple
columnar epithelium that lines the lumen of the gallbladder. Notice that this tissue is highly convoluted and is
found on finger-like projections of the mucosal lining, called mucosal folds.
Description: A single layer of tall rectangular cells that look like columns. Notice that the nucleus of each cell
is about 2/3 of the way down from the lumen, towards the basement membrane.
Location: Lines the gallbladder and most of the digestive tract organs (stomach, small and large intestines).
Function: Absorption and secretion.
Seen below: drawing of simple columnar epithelium – lateral aspect.
Seen below: light photomicrograph of simple columnar epithelium – from the gallbladder (40X).
Remember that the slide may have both liver
and gallbladder on it. To locate the
epithelium look for the mucosal folds of the
gallbladder, as illustrated in the figure at left
(and on the next page). Notice that the folds
extend into the lumen of the gallbladder.
The mucosal folds increase the surface area
of the epithelium, for more efficient
secretion and absorption.
Mucosal fold
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Seen below: light photomicrograph of simple columnar epithelium – from the gallbladder (100X).
The simple columnar epithelium can be seen in this
photomicrograph lining the lumen of the gallbladder.
Even at this relatively low magnification the position
of the nuclei toward the bottom of the cells (close to
the basement membrane) can be seen.
Seen below: light photomicrograph of simple columnar epithelium – from the gallbladder (400X).
The exact shape of each individual columnar cell is
hard to see in this photomicrograph. However, the
position of the nuclei in the bottom one-third of each
cell is an identifiable characteristic.
Seen below: light photomicrograph of simple columnar epithelium - from the small intestine (40X).
This micrograph shows the epithelium lining the small
intestine. The finger-like projections sticking into the
lumen of the small intestine are called villi (plural);
villus is the singular term of this word.
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Seen below: light photomicrograph of simple columnar epithelium - from the small intestine (100X).
At this magnification the position of the
nuclei in the bottom one-third of each cell
is obvious. As mentioned in the
description for the previous slide, the
finger-like projections sticking into the
lumen of the small intestine are called villi
(plural); villus is the singular term of this
word.
Villus
Seen below: light photomicrograph of simple columnar epithelium - from the small intestine (400X).
Simple columnar epithelium lining the
small intestine contains goblet cells, which
produce mucous. The mucous helps to
lubricate the passage of the food through
the digestive tract.
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4. Stratified Squamous Epithelium (keratinized and non-keratinized)
As the drawing and photomicrographs below (and on the next page) illustrate, this tissue consists of many
layers of cells. The cells next to the basement membrane are columnar to cuboidal in shape and the cells next to
the lumen are squamous in shape. Stratified tissues are named according to the shape of the cells at the free
surface of the tissue.
Description: Many layers of cells with squamous cells located at the free surface or facing the lumen.
Location: The keratinized variety is located on the outer surface of the skin (epidermis). The non-keratinized
variety lines the mouth, esophagus, and vagina.
Function: Protection.
Seen below: drawing of stratified squamous epithelium – superior and lateral aspect.
Notice that the cells near the basement membrane are
columnar to cuboidal in shape, and the cells near the free
surface/lumen are squamous in shape. Epithelial tissues are
always named according to the shape of the cells at the free
surface, so this is a stratified squamous epithelium.
Seen below: light photomicrograph of stratified squamous non-keratinized epithelium – from vagina (40X [left]
and 100X [right]).
At above left (40X) the stratified squamous non-keratinized epithelium rests on a slightly darker staining
basement membrane. At above right (100X) the basement membrane and epithelium is more obvious.
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Seen below: light photomicrograph of stratified squamous non-keratinized epithelium – from vagina (400X).
At this magnification, the squamous shape of the cells
next to the lumen can be seen. Notice that dark staining
nuclei can be seen in most cells, all the way up to the
free surface.
Seen below: light photomicrograph of stratified squamous keratinized epithelium – from skin (40X [left] and
100X [right]).
At above left (40X) the stratified squamous keratinized epithelium of the epidermis (skin) appears as two thick,
stained bands of cells next to the free surface. The lighter band closer to the lumen is composed of the
keratinized cells, which are dead. The darker staining band is composed of the living cells of this epithelium.
The three layers of the skin (epidermis, dermis, and hypodermis) are for orientation purposes only; you will not
be asked to identify these structures. However, adipose tissue (shown later in this packet) is sometimes visible
in the hypodermis. At above right (100X) the stratified nature of this epithelium can barely be seen.
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Seen below: light photomicrograph of stratified squamous keratinized epithelium – from skin (400X).
At this magnification the stratified nature of the
tissue can be discerned; however, the free surface
cannot be seen in this view.
5. Pseudostratified Ciliated Columnar Epithelium
As the photomicrographs below (and on the following pages) illustrate, this tissue is not really stratified (hence,
the prefix “pseudo”). Note that this tissue also contains numerous goblet cells and looks a lot like simple
columnar epithelium. However, unlike simple columnar epithelium, this tissue is not found lining the intestines
or gallbladder. The presence of cilia is an important identifying characteristic, as this is the only ciliated tissue
you will examine this quarter.
Description: Looks like a stratified tissue, but it is not. Each cell sits on the basement membrane, but only
some cells are tall enough to reach the free surface.
Location: Lines the upper respiratory tract, the epididymis, and part of the male urethra.
Function: Secretion and movement of mucous by ciliary action.
Seen below: light photomicrograph of pseudostratified ciliated columnar epithelium – from trachea (100X).
At this magnification the pseudostratified ciliated
columnar epithelium can be seen next to the
lumen. The epithelium has a darker stain than the
underlying connective tissue. A darker band of
pink-staining skeletal muscle can be seen running
diagonally in the lower right.
Pseudostratified ciliated
columnar epithelium
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Seen below: light photomicrograph of pseudostratified ciliated columnar epithelium – from trachea (400X).
At this magnification the cilia are clearly visible
as a fuzzy layer at the free surface. Notice that
the tissue appears to be stratified due to the
presence of nuclei at different levels, when in fact
it is not.
Pseudostratified ciliated
columnar epithelium
6. Transitional Epithelium
As the drawing and photomicrographs below (and on the next page) illustrate, this tissue has features common
to stratified cuboidal and stratified squamous epithelium (hence the name transitional). This tissue can be
identified easily from two distinguishing characteristics: 1) The surface cells are scalloped. 2) In the cells next
to the lumen, the nucleolus can be clearly seen within the nucleus of each cell.
Description: The appearance of this tissue can vary greatly, but cells at the free surface usually appear to have
a “scalloped” texture.
Location: Lines the urinary bladder and ureters.
Function: Permits distention (stretching) and elastic recoil.
Seen below: drawing of transitional epithelium – superior and lateral aspects.
Scalloped texture
This drawing illustrates the stratified nature of this tissue.
Notice the scalloped texture of the cells at the free surface.
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Seen below: light photomicrograph of transitional epithelium – ureter (100X).
The transitional epithelium in this
photomicrograph can best be identified by
its association with the characteristically
shaped lumen of the ureter; the scalloped
texture of the cells lining the lumen cannot
be seen at this low magnification.
Seen below: light photomicrograph of transitional epithelium – urinary bladder (400X).
The shape of the cells next to the lumen
(the presence of scalloping) and the visible
nucleolus within the nucleus of the cells
next to the lumen are all clues to identifying
this tissue.
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CONNECTIVE TISSUES
These are the most abundant tissue types in the body. Most connective tissues have a rich blood supply (they
are highly vascular). The exception to this rule is cartilage, which is avascular. Connective tissues are
characterized by widely scattered cells found in an extracellular matrix.
The flow chart below illustrates the various types of connective tissues found in the human body.
There are three basic elements found in connective tissue.
1. Cells (such as fibroblasts, chondrocytes, or osteocytes).
2. A ground substance. *
3. Protein fibers (collagen, reticular, and elastic). *
*The ground substance and fibers together make up the extracellular matrix.
The ground substance of a connective tissue may be:
(1)
(2)
(3)
(4)
(5)
Fluid – as in vascular connective tissue (blood).
Semifluid – as in areolar connective tissue.
Gelatinous – as in mucous connective tissue.
Fibrous – as in dense regular connective tissue.
Solid – as in osseous connective tissue (bone).
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7. Areolar Connective Tissue
As the photomicrograph below illustrates, this tissue has many collagen and elastic fibers running randomly
throughout it. The nuclei of many cells associated with the connective tissue can also be seen.
Description: Consists of collagen, elastic, and reticular fibers embedded in a semifluid matrix, together with
fibroblasts, mast cells, plasma cells and macrophages.
Location: Hypodermis (subcutaneous layer of skin), around most body organs, between muscles.
Function: Loosely binds organs together.
Seen at left: light photomicrograph of areolar
connective tissue (100X).
8. Vascular Connective Tissue (Blood)
Seen below: light photomicrograph of vascular connective tissue (400X). Blood is a connective tissue that has
a fluid matrix called plasma. Three basic types of cells are found suspended in plasma:
1. Erythrocytes (red blood cells).
Description: Biconcave cells that are stained pink.
The thinner center of the cell is lighter than the rim.
Location: Suspended in blood plasma.
Function: Transports respiratory gases (oxygen
and carbon dioxide).
2. Leukocytes (white blood cells).
Description: Cells with an obvious, darkly staining
(usually multi-lobed) nucleus.
Location: Suspended in blood plasma, and in
lymphatic tissues.
Function: Involved in immunity.
3. Thrombocytes (platelets) which are involved in blood clotting.
Description: Darkly stained structures much smaller than erythrocytes.
Location: Suspended in blood plasma.
Function: Involved in blood clotting.
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9. Adipose Connective Tissue (Fat)
As the photomicrograph below illustrates, this tissue consists of cells called adipocytes that encircle individual
lipid droplets.
Description: Resembles a chicken-wire fence. Each adipocyte has a large central area where fats are stored.
Location: Subcutaneous layer of skin (hypodermis), fatty-capsule surrounding the kidney, yellow bone
marrow, and around the heart.
Function: Energy storage, insulation, protection.
Seen below: light photomicrograph of adipose connective tissue (100X).
This is a slide of the skin (hypodermis). Connective
tissue fibers, blood vessels, and sweat glands can be
seen embedded in the adipose tissue. The lipid
droplets encircled by the individual adipocytes have
been washed away by the staining process used to
color the slide, so only empty spaces remain where
the lipid droplets were once located.
10. Dense Regular (White/Fibrous) Connective Tissue
This tissue contains of numerous collagen fibers oriented in the same direction. This produces great strength in
the direction that the fibers run.
Description: Contains many collagen fibers running
in the same direction. Individual fibers appear to be
"wavy". Fibroblasts can be seen between the fibers.
Location: Makes up tendons and ligaments.
Function: Attaches muscles to bones (tendons) and
bone to bone (ligaments).
Seen at left: light photomicrograph of dense regular
connective tissue (100X).
The collagen fibers in this tissue are densely packed
together and run in one direction (in this view, from
left to right). There is great strength in the direction
of the fibers, but this tissue can be relatively weaker
in a direction at right angles to the fibers. The fibers
are slightly wavy, allowing them to stretch (to some degree) down their length. The wavy appearance of the
fibers is an identifiable characteristic of this tissue.
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11. Hyaline Cartilage Connective Tissue
This tissue has a matrix that is firm enough to bear a lot of pressure without permanent distortion. Hence, it is
found covering the ends of the bones within our freely movable joints, where it reduces friction for the smooth
articulation of the bones within the joint. Bones in the embryo start off as hyaline cartilage templates for the
later developing bone. Cartilage is avascular and has no nerves.
Description: Consists of chrondrocytes (cartilage cells) located in spaces called lacuna, which are surrounded
by a translucent matrix interlaced with collagen fibers.
Location: Covering the ends of long bones within freely movable joints, costal cartilages between the ribs and
the sternum, tracheal rings, parts of the larynx, and the embryonic skeleton.
Function: Reduces friction in joints; support with flexibility.
Seen below: light photomicrograph of hyaline cartilage connective tissue (100X) – from trachea.
At this magnification a ring of hyaline cartilage
can be seen supporting the wall of the trachea.
The individual cells of the cartilage
(chondrocytes, within lacunae) are just visible as
dark purple dots. You will not be asked to
identify chondrocytes or lacunae; they are
mentioned for orientation purposes only.
Seen below: light photomicrograph of hyaline cartilage connective tissue (400X) – from trachea.
The chondrocytes in the lacuna are obvious at this
higher magnification. Notice that the
chondrocytes often are found in pairs inside the
lacuna. The matrix is translucent.
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12. Osseous connective tissue (bone)
The slide you are looking at is a slice of dense bone from the shaft of a long bone, ground down to become
extremely thin and translucent (hence the slide name – "ground bone"). Bone tissue has a hard matrix
containing ions of calcium and phosphorus. This matrix is laid down around a dense network of collagen fibers
in layers called lamellae. Systems of canals containing blood vessels, nerves, and lymphatic vessels can be
identified. These Haversian systems resemble tree stumps and are also known as osteons. Osteocytes (bone
cells) can be seen inside small hollow spaces (lacunae).
Description: A network of osteons makes ground bone resemble a field of tree stumps.
Location: Makes up the bones of the body.
Function: Protection, support, mineral storage, fat storage (yellow marrow).
Seen below: light photomicrograph of ssseous connective tissue (100X).
A Haversian canal is located in the center of each
osteon. In life, it contains nerves, lymphatic
vessels, and blood vessels that run the length of
the bone. The wide opening on the right is a
Volkmann's canal that transports the same
structures from the outside of the bone to the
inside of the bone (marrow cavity) and back. You
will not be asked to identify osteocytes, lacunae,
or Volkmann’s canals; they are mentioned for
orientation purposes only.
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MUSCLE TISSUES
Muscle tissues are composed of fibers that function to contract to shorten the muscle. There are three distinct
types of muscle tissue based on location, structural, and/or functional characteristics.
13. Skeletal Muscle Tissue
Skeletal muscle tissue is so-called because it attaches to bones and is involved in the movement of bones at
joints. It is also referred to as “voluntary muscle” because we have voluntary control of its contraction; in
addition, it is sometimes called “striated muscle” because of its striated appearance when you look at it through
a light microscope at high magnification.
Description: Long, striated cells (fibers) with the
nuclei located at the edges of the cells.
Location: Attached to bones by tendons.
Function: Moves bones to produce movement,
maintenance of posture, heat production.
Seen at left: light photomicrograph of skeletal muscle
tissue (400X).
Notice the striated appearance of this tissue and the
location of the nuclei at the edge of the fiber (cell) in
the lower right part of the picture. The striations run
perpendicular to the direction of the skeletal muscle
fibers (cells).
14. Smooth Muscle Tissue
Smooth muscle is composed of elongated cells that are not striated. Each smooth muscle cell is spindle-shaped
(largest at its midpoint and tapered towards its ends). Each cell has a single nucleus located in the middle
(broadest) part of the cell.
Description: Long tapered fibers with a centrally
located nucleus.
Location: Walls of hollow internal organs such as
the urinary bladder, stomach, intestines, uterus,
gallbladder, urinary bladder, and blood vessels.
Function: Movement of the substance inside the
hollow organ (example: food in the intestines, blood
in the heart, etc.).
Seen at left: light photomicrograph of smooth muscle
tissue (400X).
Notice the position of the single nucleus in the center
portion of the fiber. Notice also that the fibers are
non-striated.
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15. Cardiac Muscle Tissue
Cardiac muscle is composed of striated fibers that are branched. The nuclei are centrally located. The presence
of darkly stained intercalated discs is a good identification characteristic of this tissue.
Description: Branched striated fibers with a
centrally located nucleus.
Location: Wall of the heart.
Function: Pumps blood throughout the body, via
the blood vessels.
Seen at left: light photomicrograph of cardiac
muscle tissue (400X).
Intercalated discs are junctions where the ends of
cardiac muscle cells meet. They allow for the fast
communication between heart cells that allows all
the cells of the heart to act in unison, facilitating
the pumping action of the heart to propel the
blood through the blood vessels.
NERVOUS TISSUES
16. Nervous Tissue
Two basic types of cells are found in nervous tissue. Neurons are large cells that function to conduct electrical
impulses from one part of the body to another (example: from the spinal cord to the brain). Neuroglia are small
cells that support the neurons in a number of different ways.
Description: Large neuron cell bodies with
obvious processes (axons and dendrites)
extending from them. Many small nuclei of
neuroglial cells (including astrocytes) are visible
as dark dots (the neuroglial cells themselves
cannot be seen).
Location: Nervous system.
Function: Conduct electrical (nerve) impulses
throughout the body.
Seen at left: nervous tissue (100X) - from ox
spinal cord, motor neuron smear.
Notice that each neuron has a large cell body
with a conspicuous nucleus and multiple cell
processes. You will not be asked to identify the
axon, dendrite (cell processes), or axon hillock.
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