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Study Guide for Chapter 4, Tissues, for Marieb Human Anatomy and Physiology text, p. 113.

Tissues are groups of cells of similar structure and function. Several tissues are found in an
organ which also has its own blood and nervous supplies. An organ system performs related
tasks, e.g., the digestive system that includes the gut tube, pancreas and liver.

See https://histo.life.illinois.edu/histo/atlas/slides.php

http://www.kumc.edu/instruction/medicine/anatomy/histoweb/index.htm

http://www.nursegroups.com/article/histology-resources.html

for on-line atlases.

TISSUE TYPES

1. EPITHELIUM - avascular cell layers that cover or line organs. If cells are in a single layer,

the epithelium is simple. If several layers thick, the epithelium is stratified. See pg. 119.

TYPES – see p. 115

Squamous - cells are tile-like. Nucleus is round from a surface view and squashed top to bottom

from a side view. Simple squamous epithelium is found in peritoneum which is a serous membrane

that secretes a watery lubricant on the abdominal organs as they rub together. Stratified squamous

epithelium is found in the skin and the mouth. In the mouth, it is part of a mucous membrane lubricated

by a thick, more sticky mucus. Mucus is secreted into the mouth by the exocrine (ducted)  salivary

glands. Cornified or keratinized stratified squamous epithelium is found in the outermost layer

of the skin. The cornified layer is composed of many dead, scaly cells.

b. Cuboidal - cells are box-like with a round nucleus. Mostly it is found as a
simple layer, i.e., thyroid follicles, bile and kidney ducts. In the sweat gland
ducts are lined with two-layers and are therefore stratified.

c. Columnar - Cells are shaped like columns. Simple columnar epithelium is lines the digestive tract
from the stomach to the rectum. In the small intestine food absorption occurs through this layer.
Ciliated columnar epithelium is found in the oviducts or Fallopian tubes. A more complex
pseudostratified columnar is found in the trachea, bronchioles and bronchi. In a pre cancerous stage
of lung cancer, this ciliated layer is replaced with a stratified squamous layer in the bronchioles.
Stratified columnar is found in the parts of the urethra that empties the bladder.

d. Transitional - a stratified layer with "dome" shaped cells on the outer surface when the layer
is relaxed. When stretched, the layers looks squamous. It is found in the ureters and urinary bladder.
Too bad it doesn't stretch further in the kids you are hauling in the family car!

1. CONNECTIVE TISSUES - it binds together and supports many tissues. It has three basic materials:

(1) ground substance is a secreted material outside the (2) connective tissue cells and (3) fibers.
Matrix includes the ground substance and fibers. For instance, calcium phosphate is secreted onto
collagen fibers in developing bone tissue.

            TYPES - See p. 124.
               a. Mesenchyme - star-shaped cells that fill spaces in an embryo.

               b. Fibrous Connective Tissues - composed mainly of collagenous and elastic fibers made by
                   fibroblasts.

Other cells include: the macrophage that eats bacteria and antibody labeled particles,
(e.g., viruses; the   plasma cell that makes antibodies) and the mast cell that makes histamines
that make blood vessels leaky so that more immunecells and chemicals from the blood can enter tissues
to fight infections. Edema or tissue swelling results and the area becomes reddened with increased
blood flow (inflammation).

                (1.)  Loose irregular or areolar C.T. - fibers run in various
                directions, it looks like cotton. It is found between muscles and the skin.

                (2.)  Dense irregular C.T. - found in bundles under the
                epidermis (epithelium) of the skin. Also, it is found in
                scar tissue.

                (3.)  Dense regular C.T. - found in tendons and
                ligaments where the collagen fibers are parallel.

                (4.)  Reticular - found as the network of fibers
                supporting the spleen.

    b.  Cartilage - the avascular, solid matrix is a porous protein.

        (1.) Hyaline cartilage - a clear, white cartilage composed of a somewhat brittle protein ground
        substance secreted by chondrocytes onto collagen fibers. See pg. //135.
        It is found  in the nose and on the ends of long bones where they come together and
        make joints.

        (2.)  Elastic cartilage - has large numbers of elastic fibers. Found in
        the ears and the epiglottis. See p. 131.

        (3.)  Fibrocartilage - filled with collagen fibers and a small amount
        of cartilage ground substance. In the vertebral disc, it makes a tire-like circle
        around the highly vascularized, gelatin-like central pulp.  Also it is found in the pubic
        symphysis which joins the pelvic bones anteriorly.

c.  Bone - the ground substance is calcium phosphate secreted by osteoblasts onto collagenous fibers.

d.  Adipose or fat - is found as yellow or white fat in the hollow portions (diaphyseal marrow cavity) of
bones, around the heart, and in the lowest layer of the skin. Yellow fat cells have a very large fat vacuole
and a very small amount of cytoplasm. Brown fat is rare as a tissue. It has lots of blood vessels and the
cells are filled with mitochondria. Brown fat is thought to regulate fat metabolism. See pg. //132.

e.  Muscle - muscle cell moves tissues including bones by contracting or shortening. There are three types.

(1.)  Striated Skeletal Muscle - stripes or striations are composed of the
contractile proteins actin and myosin. See the cell study guide. Cells are multi-nucleated
with the nuclei at the edges of the rod-like cells. They contract with a great deal of force
in moving bones as levers but, compared to the other types, fatigue easily. See pg. 138//140.

(2.)  Smooth muscle - these cells are shaped like spindle rollers, round in the
center and pointed at the ends. They are called smooth because they are not striated or
stripped. They are found around the gut where they produce the food moving, squeezing
motion of  peristalsis.

(3.)  Cardiac muscle - found in the heart. It is striated but the rod-like cells are
shorter and have round, centrally located nuclei. Weaving with each other, they join at
intercalated discs. Cardiac muscle will not enter into a state of constant contraction
(tetanus) as does skeletal muscle and it is resistant to fatigue.

Cancer - See p. 142 of text.

The progression of normal cells to malignant cells is characterized by changes in cell structure and activity. Precancerous changes include a change in cell structure called (1) metaplasia (one normal tissue type to another normal type; e.g., the bronchial epithelium of smokers lungs changes from pseudostratified ciliated columnar to stratified squamous), 2.) dysplasia (cells are not cancerous, but they have abnormal structure, such as very large nuclei), or anaplasia (cells are dividing rapidly and have changed in function). When the cells lose control of mitosis, abnormally high cell division rates (hyperplasia) results in a tumor. If the cells of a tumor are abnormal in structure, the mass is called a neoplasm (new tissue).

Tumors are masses of cells that do not serve a normal purpose, e.g., tumors of the adrenal cortex may result in an over-secretion of the steroid hormones it produces, certain other types of tumors may decreases the secretion of an endocrine gland. A tumor may be benign or malignant. A tumor becomes malignant when the hyperplastic tissue cells invade other tissues. Tumors may be confined or nodular, or they may be diffuse, spreading gradually into normal tissues.  Malignant cells secrete a growth/migration factors and metaloprotease enzymes that break down the collagen of basement membranes. When the tumor is larger, these cells secrete angiogenesis factors to vascularize (make blood vessels to serve) the tumor. Then the invasive cells make their way to blood vessels, lymph vessels and other stromal (under the basement membrane) tissues; thus, spreading to other locations and on to other organs in a process called metastasis. One newly developing tumor acts to supply seed cells for satellite tumors. Generally, the further away the satellite tumors are from the original tumor, the worse the prognosis for survival. Mutations of DNA are required for each stage (metaplasia, dysplasia or anaplasia, hyperplasia and metastasis). The current theory is that the mutations of suppressor genes cause the cells to revert to an "embryonic" state in that they lose control over mitosis and secrete the enzymes and growth factors that produce metastasis.

Intermediate Fibers and Malignant Tumors

GFAPs are found in glial cells of the brain. When the GFAP genes are over-expressed, the accumulation of GFAP is a "marker" the diagnosis of gliomas; specifically,  astrocytes or oligodentroctes. GFAP proteins are also found superimposed over the neurofibrillary plaques of Alzheimer's disease.

Several types of keratin fibers fill up cells in the glassy layer of the skin (stratum lucidum). Hyperkeratosis is considered to be a pre-cancerous condition if it occurs on the lip. Carcinomas are cancers of epithelial cell origin. The genes that produce certain types of keratin are over-expressed in carcinoma cells, particularly in those on the outside edge of the tumor. The excess keratin is needed for the movement or invasiveness of the cancer cells. Keratin may also help cancer cells resist the tumor necrosis (rotting) toxin produced by macrophages.

Vimentin is an intermediate fiber found the cells that are formed from the embryonic tissue mesoderm. Mesoderm forms blood vessels, muscle, connective and neural tissues. A sarcoma is a cancer of certain cells in bone or "soft tissues."  Vimentin genes are over-expressed in cells of sarcomas.

            Desmin and laminin are found in muscle cells. If a sarcoma has large amounts desmin and laminin in the tumor cells, the origin of the
            cancer was from muscle cells (leiomyocytoma). Malignant fibrous histiocytomas are cancerous tumors that originate from fibroblasts. They will contain large amounts of vimentin as practically the only intermediate filament.

http://www.fhcrc.org/science/education/courses/cancer_course/basic/img/colon.gif

Questions to ponder

1. A sarcoma was biopsied and the cells were tested for the presence and amount of keratin, vimentin, desmin, laminin and myoglobin. What kind of cells produced the sarcoma if the first test was negative, the second normal positive, third and fourth and fifth positive.

Genetic Engineering

Normal genes can be cut out of cellular DNA or RNA. These can be spliced into the genes of
harmless viruses. The normal genes can "jump" from the viral DNA or indirectly through the
viral RNA to the host cell DNA, thereby carrying good genes into the cells containing defective
ones. Gene replacement therapy shows promise in treating diseases like Duchienne muscular
dystrophy (due to a defective Ca⁺⁺channel) and cystic fibrosis (caused by a defective Cl^-
channel).

Aging Theories

1. Loss of telomeres - short pieces of the ends of chromosomes are lost with each mitotic

division. When the telomere has been shortened, a signal cannot be transmitted to start
cell division. The cell becomes senescent and dies. Each cell type is thought to have a set
number of times to divide. Cancer cells are the exception, they are immortal if maintained in
culture. They have an enzyme called telomerase that reconstructs the telomeres. There are
breast cancer cells alive today that were taken from a woman who died of that disease in 1968.

2. Accumulation of Mutations - not only is series of mutations a cause of cancer but they are

Suspected to be a cause of cellular senescence. Cell death and other chemical processes
produce highly reactive "free radicals" (peroxide groups and chemicals that have oxygen
atoms with unpaired electrons). These can damage genes and structural proteins. By
stimulating cell divisions, mitogens like nicotine, encourage the accumulation of mutations.
In general tumor suppressor genes are first mutated, that may then allow for the activation of oncogenes.
See the figure on page //146.

3. Accumulation of "Clinkers" - lipofuscin, undigested/yellowish fatty deposits accumulate

in cells over a lifetime. These interfere with cell metabolism and function.

4. Genetics - most species of plants and animals have a relatively narrow range of life expectancy.

If you want to live a long time, do a better job of picking your parents.

5. Glucose Cross-linking of Collagen - stiffens tendons and ligaments.
6. Taking Aliff’s tests.
7. Decreases in neural conduction and secretion of hormones - as one ages, secretions of

growth hormone, testosterone and estrogen decline. Changes include a decrease in muscle
mass and a corresponding increase in fat, and a thinning of the bones (osteoporosis) making
fractures more common and slow to heal.

            Why do dogs only live 10-12 years?

Study Questions
1. Explain how nicotine and anabolic steroids do not cause cancer but rather encourages
the development and spread of tumors.
2. Where is each type of epithelium found (one prominent location for each)?
3. Where is each type of connective tissue found?
4. Where is each type of muscle found?
5. Compare and contrast the functions of (1) elastic and collagen fibers, (2) bone
and cartilage, and (3) smooth, cardiac and skeletal muscle.

Email:john.aliff @ gpc.edu