LAB 1

                                                               ANIMAL TISSUES

In complex organisms, groups of cells are specialized to perform different functions within the organism.  These groups of cells are similar in structure and function and are called tissues.  Related groups of tissues form specialized organs, which, in turn, are organized to function as organ systems. Vertebrate tissues can be grouped into five major categories:

1.  Epithelial Tissue - functions: protection, absorption, secretion, diffusion, filtration, and
                 sensory.

2.  Connective Tissue - functions: support and attachment of tissues.

3.  Muscle Tissue - functions: movement

4.  Nervous Tissue - functions: integration of body functions, receiving stimuli and
                 controlling the  responses to those stimuli.

5.  Blood (Vascular) - functions: transportation of substances to and from body cells, body
                 defense or immunity.

Each of the five major tissue types are composed of cells designed for their specialized functions.  A single layer of cells comprises a simple tissue; a tissue comprised of multiple layers of cells is stratified.  Any stratified tissue may provide a protective function.

1.         Epithelial Tissue includes:
                       a.  Squamous Epithelium - found on skin surface, lining the mouth, esophagus,
                       reproductive tracts, blood vessels and body cavities.
                                                               Functions - diffusion and/or filtration

b. Cuboidal Epithelium (Glandular) -found in gland and gland‑like organs
                                                              Functions - absorption and secretion

c. Columnar Epithelium (Glandular) -found lining the stomach, small intestine and
                        large intestine.
                                                              Functions -absorption and secretion

d. Ciliated Epithelium ‑ found lining the respiratory tract and the oviducts
                                                              Functions - protection and reproduction

Question 1:    List the five major types of animal tissue and the function(s) of each.

 

 

 

 

Question 2:    Explain the difference between simple and stratified tissue.

 

Question 3:    List the four types of epithelium, the function and location of each.

 

2.         Connective Tissues - Connective tissues are characterized by few cells of varying
                        types scattered throughout a matrix of fibers or other non-living materials.  The
                        nature of the matrix determines the type of connective tissue.

a.  Fibrous Connective Tissue - functions - to hold skin to muscle and bind many
                        body parts together.  Ligaments and tendons are specialized fibrous connective
                        tissue.

                        b.  Cartilage - forms the skeletal framework of embryonic vertebrates and adult
                        cartilaginous fish

c.  Bone - forms the skeletal framework of most adult vertebrates

Question 4:    List the three types of connective tissue and their locations.

 

 

3.  Muscle Tissue includes:

a.  Cardiac Muscle - found only in the heart
                                                      - responsible for contraction of the heart resulting in the
                                                       "heart beat"

b. Smooth or Involuntary Muscle - responsible for movement of substances through
                                                        the body
                                                       - found in digestive tract, blood vessels, bladder, and
                                                       airpassages to the lungs

c. Skeletal or Voluntary Striated Muscle - found attached to the skeleton
                                                       - responsible for bodily movements

 

Question 5:    List the three types of muscle tissue, the function and location of each.

 

4.  Nervous Tissue - found throughout the body and comprising the brain and spinal cord
                                           -  functions: receiving stimuli and conducting the message to  another 
                                                  neuron, muscle or gland

5.  Blood Tissue - found circulating throughout vessels in the body
                                       - function - to transport substances to and from body cells

Question 6:    List the two remaining types of tissue, the function and location of each.

 

LAB OBJECTIVE: 

To be able to identify various animal tissues and their functions in animals.

 

Examine the following animal tissues using the slides indicated.  Always bring cells of the tissue into focus using the 4X object before switching to the 10X and 40X objectives.

I.          Epithelial Tissue
                        A. Squamous Epithelium
                        Recall that you have already examined the squamous epithelium of your mouth when
                        you prepared the slide of your cheek cells.  Obtain the prepared slide labeled
                        "Simple Squamous Epithelium". 

Examine the tissue and note the flat appearance and typical mosaic or flagstone arrangement of a sheet of the epithelium.  (Refer to Figure 1.)  This slide is difficult to bring into complete focus because it is stratified.  Use low light to examine the slide by adjusting the iris diaphragm.  Examine on all powers noting the large central nucleus and the plasma membrane.  You may also see pigment granules scattered throughout the cytoplasm which give color tone to the skin. 

Question 7:    List two distinguishing characteristics of squamous epithelium cells.

 

B. Cuboidal Epithelium
                         This epithelium is typically found in gland and gland‑like organs.  Obtain the slide labeled  "Simple Cubodial Epithelium".  This slide is of cubodial epithelium lining the kidney tubules. Look for small circles of cells.  Scan the slide on 4X.  Switch to 10X and find some cells  that have the characteristic shape.  (Refer to Figure 2.)

Question 8:    What is the shape of the cells that make up the walls of the tubules?

 

Question 9:    Where within each cell is the nucleus?

C. Columnar Epithelium
     Obtain the slide labeled "Columnar Epithelium".  This slide is a cross section through an animal's small intestine.  The cells you want to examine line the cavity of the intestine (in the center).  The lining of the cavity is folded into finger‑like projections called villi to increase the amount of surface area available for absorption of food.  The villi possess projections, microvilli, comprising their striated borders.  Notice some of the cells have a gap or plug on their free edges.  These are goblet cells, and the gap or plug is filled with mucous.  These goblet cells secrete mucous to cover and protect the columnar epithelium from being damaged by acid from the stomach.  (Refer to Figure 3.)

Question 10:  Where within the cells is the nucleus located?

 

Question 11:  What are goblet cells?

 

Question 12:  What type of epithelium are goblet cells?

 

D. Ciliated Columnar Epithelium
                        This epithelium is very similar in structure to columnar epithelium.  The only difference to be  noticed is the cilia (singular = cilium) which are short, hair like structures capable of  movement.  The slide you are examining is taken from the trachea of a frog.  You will have
to look very carefully using the 40X objective to see the cilia located on the free borders of
these cells.  (Refer to Figure 4.)

Question 13:  What is the function of the cilia?

Figure 2: Cubodial Epithelium

                   Figure 1:  Squamous Epithelium

Figure 3:  Columnar Epithelium

Figure 4:  Ciliated Columnar Epithelium

       II.   Connective Tissue

 A. White Fibrous Tissue:
                        This slide is specially stained to show the many dense fibers found in many of the connective tissues.  There is little on the slide except connective tissue fibers.  These fibers are composed of a protein called collagen and are white in their natural state.  The fibers are organized into parallel bundles. Glue is made from animal collagen fibers. 

Question 14:  What is collagen?

 

B. Hyaline Cartilage:
                        This is the most common type of cartilage.  The human skeletal framework is first cast in this type of  cartilage and later replaced by bone.  This cartilage is almost clear in its natural state.  The slide you have shows more than just the cartilage.  Locate the area of hyaline cartilage.  Identify the lacuna, chondrocyte (cartilage cell), and the matrix (composed of chondroiten sulfate and collagen fibers).   (Refer to Figure 5.)

Question 15:  What are lacunae?

 

C. Bone:
                        Bone is composed of cells (osteocytes) embedded in a matrix of collagen fibers on which calcium salts  are deposited.  The bone cells are living in the solid bone trapped in small chambers called lacunae.  Typically, bone is laid down in areas of concentric layers (lamellae) of solid bone forming Haversian Systems.  Examine the Haversian Systems in a slide of ground bone.  Identify lamellae, lacunae, Haversian Canal, and canaliculi.  (Refer to Figure 6.)

Question 16:  What is the function of the Haversian Canal?

 

 

      III.   Muscle Tissue

 A. Smooth or Involuntary Muscle:
                      This type of muscle is described as smooth because of its appearance under the microscope and is called involuntary because normally we do not have conscious control over this type of muscle.  The slide of smooth muscle was taken from the intestine which is surrounded by two layers of this type muscle ‑ one layer running lengthwise (longitudinal smooth muscle) and one layer running around the intestine (circular smooth muscle).  In the intestine these two layers of muscle are constantly contracting to move food along the digestive tract ‑ a process known as
peristalsis.  Because the layers are arranged in different directions you will get two different views of  these muscle fibers ‑ a cross section (longitudinal muscle) and a longitudinal section
(circular muscle).  Examine the fibers of the circular smooth muscle area.  Note the spindle shaped
muscle fibers.  Locate the nuclei of the cells.  (Refer to Figure 7.)

Question 17:  What evidence can you give that smooth muscle is not normally under voluntary control?

 

Question 18:  What is peristalsis?  (Refer to glossary.)

 

 

B. Skeletal or Voluntary Striated Muscle:
Skeletal muscle is the most abundant muscle in the body and is responsible for our bodily movements. It is attached to the skeleton and is under voluntary (conscious) control.  The slide of skeletal muscle shows the typical appearance of the fibers.  The fibers are long, unbranching, syncytial (many nuclei not set apart from each other into individual cells), and visibly patterned with faint, regular parallel lines (striations) crossing the fibers perpendicular to their length.  The nuclei are displaced to one side of the fiber.  (Refer to Figure 8.)

Question 19:  List the characteristics that distinguish striated muscle tissue.

 

 

C.  Cardiac Muscle:
                        Obtain the slide labeled "Intercalated Discs".  This muscle is found only in the heart.  In appearance it is very much like skeletal muscle, but it is like smooth muscle in action (involuntary).  Cardiac muscle is best remembered by the ways it differs from skeletal muscle.  As you examine cardiac muscle note that the fibers branch.  The nuclei are centrally located within the fibers.  The fibers are crossed by occasional thickened bands of color that appear lighter than the striations.  These are the intercalated discs (tight, thickened junctions between the end membranes of individual cells of the fiber), and these structures are unique to cardiac muscle.  Cardiac muscle is also much rougher in appearance than is  skeletal muscle.  (Refer to Figure 9.)

Question 20:  What are Intercalated Discs?

 

 

       IV.  Nervous Tissue - The basic cellular component of nervous tissue is the neuron (nerve cell).  There are several different types of neurons each slightly different in appearance.  The slide you have is a smear of nervous tissue from the spinal cord of an ox.  There are many nerve cells present, but locating a single neuron will be difficult.  Try to locate an isolated neuron.  Identify the nerve cell body, the nucleus, and the spidery processes (dendrites and axon) radiating from the nerve cell body.  The many processes radiating from the nerve cell bodies is the reason that single neurons are difficult to locate.  (Refer to Figure 10.)

Question 21:  What are the functions of axons and dendrites?

 

 

 

V.  Blood
Blood is a type of circulating connective tissue in a fluid matrix plasma rather than an independent tissue  type.  Blood consists of two major portions ‑ the liquid portion or plasma and the cellular portion.  The cellular portion is mainly composed of erythrocytes (red blood cells) which are many in number and leucocytes (white blood cells) which are relatively few in number in normal blood.  The slides you have are smears of stained, normal human blood.  When you examine it under 40X, you will see many red blood cells.  They are small and appear doughnut shaped.  They have no nucleus.  The leucocytes are few in number and scattered.  You will have to search for them.  They are larger than red blood cells, and their nuclei have been stained purple.  There are several different types of white blood cells, and each type is identified by the shape of its nucleus.  Locate several different white blood cells by the differing shapes of their nuclei.  Obtain a slide of "Amphibian Blood" and examine the slide on all powers.  Compare these two slides.

Question 22:  Why are there so few leukocytes present in the human blood smear as compared to erythrocytes?

 

Question 23:  What differences are evident between the blood of an amphibian and a human?

Figure 5:  Hyaline Cartilage

Figure 9: Cardiac Muscle