Epithelial and Connective Tissues (The stuff that makes your bones not fall out)

2006-03-02T16:05:00.000-08:00

Overview:

1) Epithelial Tissue
a. Structural and functional characteristics of epithelial tissue
b. Classification of the differing epithelial tissues including; functions and locations
c. Glands of epithelial tissue including; Exocrine and endocrine, and multicellular and unicellular glands.

2) Connective Tissue
a. Common characteristics of connective tissue including structural elements
b. Types of connective tissue found in the body including characteristic functions.
Prelude: The difference between unicellular organisms and multicellular are how the cell sustains itself. Unicellular organisms and amoebas contain all the necessities to sustain themselves without the use of another cell. They can collect and digest their food and expel their waste. As with the multicellular human body, cells are specialized and rely on cell clusters to survive. Each of these specialized cells helps to create the equilibrium inside our bodies. These communities of cells that act on a specialized function are tissues. These tissues are divided into four primary types; epithelial, connective, muscle and nervous. In the following I will be reviewing Epithelial and Connective tissues.

I. Epithelial Tissue
A. Structures and functions
1) A sheet of cells that covers a body surface or lines a body cavity.
2) Covering and epithelium forms the outer layer of the skin, lines the cavities of the cardiovascular, digestive, and respiratory systems, and covers the walls and organs of the closed ventral body cavity.
3) Glandular epithelium makes the glands of the body.
4) The epidermis is an example of how epithelial tissue is used to form a boundary from external and harsh environments.
5) Used for; protection, absorption, filtration, excretion, secretion, sensory reception.

B. Classification
1) Simple Epithelia are composed of a single cell layer. Typically found where absorption and filtration occur and a thin epithelial barrier is desirable.

2) Stratified Epithelia, are consisting of two or more layers of cells stacked on top of one another. The skin surface is a good example due to it’s high exposure to the elements and abrasion.

3)Epithelial cells have three common shapes. Squamous Epithelia are flattened and scalelike, Cuboidal cells are boxlike, Columnar cells are tall and column shaped.
For Futher Reference, D=Description, F=Function, and L=Location

Simple Squamous Epithelium (A1)
D. A single layer of flattened cells, It is the simplest of epithelia.
F. Simple Squamous allows passage of materials by diffusion and filtration in sites where protection is not important. Also secretes lubricating substances in serosae.
L. Kidney, Air sacs of lungs, lining of heart, blood vessels, and lymphatic vessels, as well as lining of ventral body cavity.

Simple Cuboidal Epithelium (A2)
D. Single layer of cubelike cells with large, spherical central nuclei.
F. Secretion and absorption,
L. Kidney tubules, ducts and secretory portions of small glands, ovary surface.

Most females would complain that their cuboidal cells need tuning around the bloating time of the month.

Simple columnar epithelium (A3)
D. Single layer of tall cells with round to oval nuclei; some cells bear cilia. Layer may contain goblet cells.
F. Absorption; secretion of mucus, enzymes and other substances; ciliated type propels mucus by ciliary action.
L. Nonciliated-Lines most of the digestive tract, gallbladder, excretory ducts of some glands. Cilitated-lines small bronchi, uterine tubes, and some regions of the uterus.

Pseudostratified columnar epithelium (A4)
D. Single layer of cells of differing heights, some not reaching free surface. Can contain goblet cells and bear cilia
F. Secretion of mucus, propulsion of mucus by ciliary action
L. Nonciliated type- male’s sperm-carrying ducts and ducts of large glands, Ciliated type- lines the trachea, upper respiratory tract.

Stratified squamous epithelium (A5)
D. Thick membrane composed of several cell layers. Basal cells are cuboidal or columnar. Surface cells are squamous. In the keratinized type, surface cells full of keratin and dead.
F. Protects underlying tissues in areas subjected to abrasion
L. Nonkeratinized; moist lining of the esophagus, mouth and vagina, Keratinized; epidermis of the skin.

Transitional Epithelium (A6)
D. Resembles both stratified squamous and stratified cuboidal.
F. Stretches readily and permits distension of urinary organ by contained urine.
L. Lines the ureters, bladder, and part of the urethra.

C. Exocrine and Endocrine Glands.

Exocrine Glands- These are the glands whose secretions pass into a system of ducts that will lead to the exterior of the body. Examples of exocrine glands are:
1. The salivary glands that secretes saliva into the mouth
2. The prostate gland
3. The portion of the pancreas that secretes pancreatic fluid
4. Gastric glands
5. Sweat glands

Endocrine Glands- Endocrine glands instead secrete hormones INTO the body. There are eight glands that fall under the endocrine system. These eight are:
1. Pituitary & Pineal Glands
2. Thyroid & Parathyroid Glands
3. Adrenal Gland
4. Pancreas
5. Gonads
6. (There are many other organs that add to this system)

II. Connective Tissue
A. Common characteristics
1) All connective tissues arise from mesenchyme
2) Connective Tissues include the entire spectrum of vascularity; ex. Cartilage=avascular, Dense connective tissue=poorly vascularized, other types of connective tissue= having rich supply of blood vessels.
3) Extracellular Matrix

B. Types of Connective Tissues. (B1)
1) Mesenchyme= first definitive tissue formed from the mesoderm germ layer. Composed of star-shaped mesenchymal cells and fluid ground substance.
D. Embryonic connective tissue
F. Gives rise to all other connective tissue types
L. Primarily in embryo

*** Two subclasses to Connective Tissue proper: Loose connective (areolar, adipose, and reticular) and Dense connective tissues (dense regular, dense irregular, and elastic). ***

2) Loose Connective tissue- Areolar
D. Gel-like matrix with all three fiber types; cells, fibroblasts, macrophages, mast cells and blood cells
F. Wraps and cushions organs, reduces inflammation, holds and conveys tissue fluid
L. Under epithelia of body, forms basement membrane
a. Supporting and binding other tissues via fibers
b. Holding body fluids via ground substance
c. Defending against infection via white blood cells and macrophages
d. Storing nutrients as fat via fat cells.

4)Adipose (Fat) Tissue= Similar to areolar tissue in structure and function but superior in nutrient-storage.
D. Matrix as in areolar, but very sparse. closely packed fat cells
F.Provides reserve food fuel, insulated agianst heat loss, supports and protects organs
L. Under skin, around kidneys and eyeballs, in breasts/within abdomen

5) Reticular Connective Tissue=forms a stroma that can support many free blood cells.
D. Network of reticular fibers in a typical loose ground substance.
F. Fibers form a soft internal skeleton that supports other cell types.
L. Lymphoid organs, bone marrow, spleen, lymph nodes.

6) Dense Regular Connective Tissue=Contains closely packed bundles of collagen fibers which allows this tissue to stretch a little but once pushed holds a tensile strength to create tendons.
D. Primarily parallel collagen fibers, small elastin fibers, major cell type is fibroblasts.
F. Attaches muscle to bone, bone to bone, strong tensile ability.
L. Tendons, most ligaments

7) Dense Irregular Connective Tissue= Irregularly placed collagen produces tissue used for leathery dermis and fibrous joint capsules.
D. Same as Dense Regular except fibers are irrugularly arranged
F. Able to withstand tension exerted in many directions instead of just one (as is the case in Regular)
L. Dermis of the skin, fibrous capsules of organs and of joints.

Cited Works:
http://www.uoguelph.ca/zoology/devobio/210labs/epithelial1.html Figures A-2 through A-5
http://faculty.une.edu/com/abell/histo/transep.gif Figure A-6
http://bms.brown.edu/curriculum/b189/Lab2/Slides/Mesenchyme_C088200xa.jpg Figure B1
http://acpcommunity.acp.edu/Facultystaff/moon/Biology2/Images/Connective Figure B2
http://www2.marianopolis.edu/bio-lcv/connectivetissues/adiposetissue400x.jpg Figure B3
www.usc.edu/hsc/dental/ ghisto/Images/ct/42.jpg Figure B4
http://www.mhhe.com/biosci/ap/histology_mh/densreg.jpg Figure B5
http://www.sru.edu/images/densect.jpg Figure B6

Information used from:

"Exocrine Glands." 14 Jan. 2002. 29 Feb. 2006 http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/E/ExocrineGlands.html.

Marieb, Elaine N. Human Anatomy & Physiology. Sixth ed. New York: Pearson.

2006-01-23T07:32:00.000-08:00

1. Noah Chu
2. Wareham (Tobey Hospital) 12/30/86
3. Sid Meier
4. Possible Biology Major
5. I have 2 sisters and one brother, living with my mom residing in Rochester, MA.

Welcome to the Page

2006-01-23T07:27:00.000-08:00

Welcome all my loyal readers (only you Mr. Frolich) to Chu's new Blog.

Noah's Anatomy Blog

Epithelial and Connective Tissues (The stuff that makes your bones not fall out)

Welcome to the Page