Organs in animals are composed of a number of different tissue types. For example, the stomach:


What is the hierarchy of structure starting with atoms and ending with the organism?


What is the definition of tissues?

Cells and tissues that comprise the stomach.


Organs are composed of tissues, which are in turn composed of cells. Animals have four: epithelial, connective, muscle, and bone.

What are the 4 types of tissue?



Epithelial Tissue

Epithelial tissue

    1.  covers body surfaces and lines body cavities.

    2.  Functions include lining, protecting, and forming glands.

   Where do you find epithelial tissue?  What are some to this tissue's functions?

    Three types of epithelium occur:


What are the 3 basic shapes of epithelium?  What do each look like?

What does it mean when we say epithelial tissue is simple or stratified?


        1.  can be simple or stratified.

            a.  Simple epithelium has only a single cell layer.

            b.  Stratified epithelium has more than one layer of cells.

            c.  Pseudostratified epithelium is a single layer of cells so shaped that they appear at first glance to form two layers.

What is the basement membrane made of?  Is it living?  What is its role?


Is epithelial tissue vascular or avascular?  Where is its blood supply?

Skin is made up of what epithelial tissue?

Note the single layer of simple cuboidal epithelium lining either side of a tubule.

Functions of epithelial cells include:


Which shape of epithelial tissue is most closely related to glands? 

If you needed to have a high degree of exchange, you would expect to find what type of epithelium?


Glands are classified how?  Exocrine glands secrete what and how?  Endocrine glands?  Hormones are associated with which type of gland?

Which organ operates as both and endocrine gland and as an exocrine gland?

        1.  can be single epithelial cells, such as the goblet cells that line the intestine.

    Exocrine glands

        1.  glands whose secretions pass into a system of ducts that lead ultimately to the exterior of the body. So the inner surface of the glands and the ducts that drain them are topologically continuous with the exterior of the body (the skin).

    Endocrine glands

        1.  place their secretions into the internal environment - the blood.

Many animals have their skin composed of epithelium. Vertebrates have keratin in their skin cells to reduce water loss. Many other animals secrete mucus or other materials from their skin, such as earthworms do.

Cell Junctions

If you were expecting to find a high degree of flexibility between cells, you would expect to find what type of junctions?

If you were expecting to find a high degree of control over movement of substance thru intercellular spaces, you would expect to find what type of junctions?

If you were expecting to find a strong coordination of information among neighboring cells, you would expect to find what type of junctions?  What moves through gap junctions?


Tight Junction

fluid tight seal

prevents fluid from leaving a cavity


Anchoring Junction (adhesion)

tissues that stretch, ex. Heart muscle


Gap Junction

passage of chemical & electrical signals

Connective Tissue

What is the definition of connective tissue?

Connective tissue serves many purposes in the body:

Connective cells are separated from one another by an extensive extracellular matrix. The matrix may be solid (as in bone), soft (as in loose connective tissue), or liquid (as in blood).

 Loose Connective Tissue (LCT)

    1.   Fibroblasts (LCT) are separated by a collagen fiber-containing matrix.

        a.  Collagen fibers provide elasticity and flexibility.

Collagen provides what?

        b.  LCT occurs beneath epithelium in skin and many internal organs, such as lungs, arteries and the urinary bladder. This tissue type also forms a protective layer over muscle, nerves, and blood vessels.


Adipose tissue has enlarged fibroblasts storing fats and reduced intracellular matrix. Adipose tissue facilitates energy storage and insulation.

Why is fat and not glycogen used for long term energy storage?

Adipose tissue contains what?

Fibrous Connective Tissue

    1.  has many fibers of collagen closely packed together.

    2.  FCT occurs in tendons, which connect muscle to bone. Ligaments are also composed of FCT and connect bone to bone at a joint.

Tendons connect what to what?  Ligaments connect what to what?

Cartilage and bone

    1.  are "rigid" connective tissues.

    2.  Cartilage has structural proteins deposited in the matrix between cells. Cartilage is the softer of the two. Cartilage forms the embryonic skeleton of vertebrates and the adult skeleton of sharks and rays. It also occurs in the human body in the ears, tip of the nose, and at joints.

What connective tissue is found in the ears, tip of nose, and at joints?

A human embryo's skeleton is made up of what?



    3.  Bone has calcium salts in the matrix, giving it greater strength. Bone also serves as a reservoir (or sink) for calcium. Protein fibers provide elasticity while minerals provide elasticity.   

Bone's matrix is primarily made up of what?

Why is the presence of calcium ions so important?  What acts as the calcium reservoir in the body?


4.  Two types of bone occur.

        a.  Dense bone has osteocytes (bone cells) located in lacunae connected by canaliculi. Lacunae are commonly referred to as Haversian canals.

        b.  Spongy bone occurs at the ends of bones and has bony bars and plates separated by irregular spaces. The solid portions of spongy bone pick up stress.


Osteocytes are living bone cells.  They are found within lacuna (chamber) and connect with each other by canaliculi channels.  Osteoblasts are responsible for doing what? After performing this function, osteoblasts become what?   Osteoclasts are responsible for doing what?

    5.  Blood is a connective tissue of cells separated by a liquid (plasma) matrix. Two types of cells occur.

What is the matrix in blood?  What is the role of erythrocytes?  What is the role of leukocytes?  Platelets do what?

        a.  Red blood cells (erythrocytes) carry oxygen.

        b.  White blood cells (leukocytes) function in the immune system.

        c.  Plasma transports dissolved glucose, wastes, carbon dioxide and hormones, as well as regulating the water balance for the blood cells.

        d.  Platelets are cell fragments that function in blood clotting.



Human Red Blood Cells, Platelets and T-lymphocyte (erythocytes = red; platelets = yellow; T-lymphocyte = light green) (SEM x 9,900).


Muscle Tissue

Muscle tissue

    1.  facilitates movement of the animal by contraction of individual muscle cells (referred to as muscle fibers).

What is the primary function of muscle?

    2.  Three types of muscle fibers occur in animals (the only taxonomic kingdom to have muscle cells):

Know each muscle type and if it is striated or non-striated and if it is voluntary or involuntary.  Which muscle type is branched?

Organization of muscle.

Skeletal muscle fibers are multinucleated, with the nuclei located just under the plasma membrane. Most of the cell is occupied by striated, thread-like myofibrils. Within each myofibril there are dense Z lines. A sarcomere (or muscle functional unit) extends from Z line to Z line. Each sarcomere has thick and thin filaments. The thick filaments are made of myosin and occupy the center of each sarcomere. Thin filaments are made of actin and anchor to the Z line.

Bands and zones in a muscle fiber.

Skeletal (striated) muscle fibers have alternating bands perpendicular to the long axis of the cell. These cells function in conjunction with the skeletal system for voluntary muscle movements. The bands are areas of actin and myosin deposition in the cells.


Striated skeletal muscle fibers



Smooth muscle fibers lack the striated banding, although actin and myosin still occur. These cells function in involuntary movements and/or autonomic responses (such as breathing, secretion, ejaculation, birth, and certain reflexes). Smooth muscle fibers are spindle shaped cells that form masses. These fibers are components of structures in the digestive system, reproductive tract, and blood vessels.

Smooth muscle cells

Cardiac muscle fibers are a type of striated muscle found only in the heart. The cell has a bifurcated (or forked) shape, usually with the nucleus near the center of the cell. The cells are usually connected to each other by intercalated disks.

Cardiac muscle cells . Note the dark band of the intercalated disk that separates two muscle cells.

Heart Muscle Cell (nucleus, mitochondria, actin-myosin) (TEM x15,400).

Nervous Tissue

Nervous tissue

What is the main function of nervous tissue?  Each neuron has what parts? 

    1.  functions in the integration of stimulus and control of response to that stimulus.

    2.  Nerve cells are called neurons.

        a.  Each neuron has a cell body, an axon, and many dendrites.

    3.  Nervous tissue is composed of two main cell types: neurons and glial cells.

        a.  Neurons transmit nerve messages.

        b.  Neuro-Glial cells are in direct contact with neurons and often surround them.

The neuron is the functional unit of the nervous system. .

What is the role of the dendrite, the axon, and what is contained in the cell body?

    1.  While variable in size and shape, all neurons have three parts.

        a.  Dendrites receive information from another cell and transmit the message to the cell body.

        b.  The cell body contains the nucleus, mitochondria and other organelles typical of eukaryotic cells.

        c.  The axon conducts messages away from the cell body.

Organization of a neurron.

 Large multipolar neuron (center of image)