pulse october 7, 2009. -the study of tissues -but, what does all this mean? -put simply, it’s...
TRANSCRIPT
What is Histology?-THE STUDY OF TISSUES
-But, what does all this mean?-Put simply, it’s microanatomy!
But Why Do We Really Care?
NOT SO MUCH!
Because…structure correlates with function! In disease states,
normal tissue architecture changes.
If we understand the normal, then we understand the disease!
We can use this information to help us make a diagnosis and possibly even to guide treatment.
BORING!!!!!
Histology Basics
Cells are the basic structural and functional unit of the human body
All disease processes can be traced back to an underlying defect in the cell
BUT…We want the BIG PICTURE!!!!!! CellsTissuesOrgansOrgan Systems
What is a Tissue?
There are four basic types of tissues that come together to comprise organs: 1) Epithelium 2) Connective tissue 3) Muscle 4) Nervous tissue
Epithelium
EPITHELIUM IS A TYPE OF TISSUE THAT LINES THE SURFACES OF THE BODY AS WELL AS THE SURFACES OF BODY CAVITIES (E.G. THE GASTROINTESTINAL AND RESPIRATORY TRACTS)
IN ADDITION, MANY GLANDS (ENDOCRINE AND EXOCRINE) ARE ALSO FORMED FROM EPITHELIAL TISSUE.
Epithelium
Classification: By cell shape:
Squamous: Flat, “pancake-shaped” cells; flat nuclei
Cuboidal: Cube-shaped cells equal in width and height; circular nuclei
Columnar: Tall rectangular cells with a height greater than two times the width; stretched nuclei
Transitional: Complex! Not important…yet!
By the number of layers: Simple: One cell layer Stratified: Two or more cell layers
*The type of epithelium found in a given structure depends on the function of that structure!
Connective Tissue
Connective tissue is important in support and strength
It consists of cells (mostly fibroblasts) and extracellular matrix (laid down by the connective tissue cells
Connective Tissue: Classification
1) Connective Tissue Proper A) Loose connective tissue B) Dense irregular connective tissue C) Dense regular connective tissue
2) Embryonic Connective Tissue 3) Specialized Connective Tissue
A)Blood B)Cartilage C)Bone
Loose Connective Tissue
A lot of cells; not a lot of extracellular matrix
Often found beneath epithelial surfaces, around glands It serves as a place
for immune cells to “wait” beneath the epithelial surfaces to attack invading microbes
Dense Irregular Connective Tissue
Dense: More extracellular matrix (mostly collagen), less cells
Irregular: Collagen fibers have no specific pattern; wavy
Function: Resists stretching (e.g. found in the deep layer of the skin)
Dense Regular Connective Tissue Dense: More
extracellular matrix (mostly collagen), less cells
Regular: Collagen fibers are laid down in rows
Function: STRENGTH! Found in tendons
and ligaments
Skeletal Muscle
Skeletal muscle is what you think about when you hear the term “muscle”
Features: Multiple nuclei per
cell Nuclei at the
periphery of the cell Striated
Cardiac Muscle
Cardiac muscle is the muscle found in the heart
Responsible for pumping blood!
Features: One nucleus per cell Nucleus is centrally-
located in the cell Striated Intercalated discs Branching pattern
Smooth Muscle
Smooth muscle is the muscle found in blood vessels, glands, and the components of the GI tract
This is “involuntary” muscle We can’t make it contract by
thinking about it like we can with our skeletal muscles
Features: One nucleus per cell Nucleus is centrally-located
within the cell Not striated “Spindle-shaped” cells and
nuclei