Topic 7 -Histology (Tissues) Flashcards
What is histology
The study of tissues
Tissue
A group of cells with similar structure and function
What are the four major types of tissues
Epithelial tissue
connective tissue
muscle tissue
nervous tissue
What are Cell connections
Where are they seen
How are they formed
Points of contact between adjacent cells
Seen in epithelial tissue, some nervous tissue and muscle cells
formed by cell membrane proteins
Three examples of cell junctions
Tight junctions
anchoring junctions
gap junctions
Tight junctions
a partial fusion of specific proteins on the lateral surface of the cell membrane
Form a Ring-like tight seal
Prevent material from passing between cells ex. Bacteria, proteins or fluid/ions
Anchoring junctions
Proteins that fasten cells to each other and/or to extracellular material (rivets cells together)
Gap junctions
Open channels(formed of proteins) through the adjacent cell membranes interconnecting the cytosols of the cells
Allow passage of ions in small molecules from one cell to the other
Tissues can then work as a unit (cardiac and smooth muscle) also found in epithelial
Epithelial tissue
Covers body surface (skin)
Lines body and organ cavities
Organ cavity is known as
Lumen
Characteristics of epithelial tissue
what is the basement membrane
Has one free surface
little extracellular space between the cells
avascular no blood vessels
basement membrane: extracellular layer -attaches epithelium to underlying connective tissue layer formed by both tissues (Velcro)
Classification of epithelium
Most subtypes are classified and named according to(except glandular):
number of cell layers sitting on the basement membrane:
One layer: simple
Multiple: stratified
shape of the cells in the apical layer (the layer touching the free surface)
Flattened: squamous
Cube/round: cuboidal
Taller than wide: columnar
Five types of epithelium
Simple epithelia
stratified epithelium
pseudostratified epithelium
transitional epithelium
glandular epithelium
Simple epithelia
One layer
allows for exchange of molecules, absorption/secretion
Subtypes of simple epithelia
Simple squamous: one layer of squished flat cells example lungs for exchange of gases
Simple cuboidal: one layer of cube shaped cells ex kidneys
Simple columnar: One layer of column shaped tall and thin cells ex stomach and small intestines
Stratified epithelium
More than one layer
Protective (areas of abrasion)
Subtypes of stratified epithelium
Stratified squamous: apical cells squished flat common in skin
Stratified cuboidal: apical cells cube shaped -rare
Stratified columnar: apical cells column shaped tall and thin -rare
Pseudostratified epithelium
Appear stratified (nuclei at different levels) but all cells sit on basement membrane (simple)
Lines most of respiratory tract plus ciliated
Transitional epithelium
Cell shape and layering varies with stretching found only on inner lining of urinary system
cuboidal to squamous when stretched
Subtypes of Glandular epithelium
Exocrine glands
Endocrine glands
Exocrine glands
Secrete products onto body surface or into a body cavity
they can be:
Unicellular ex goblet cells
Secrete mucus (into a cavity) in the digestive, urinary, reproductive and respiratory tracts
Multicellular
Consist of secretory and duct cells (ducts connect secretions to surface of cavity
Glands: sudoriferous (sweat), sebaceous (oil), mammary, digestive
Endocrine glands
No ducts
Secretions released directly into blood
Ex Thyroid gland secrets thyroid hormones
What are the functions of epithelia
Protection
-Often stratified squamous ex epidermis of skin
secretion
-Glandular epithelium ex thyroid or sweat glands
control of permeability
- Typically simple epithelium
- Exchange of material ex kidneys, intestine or capillaries
Connective tissue
Mainly supports and connects tissues
cells far apart separated by an extracellular matrix
extracellular material, gives CT subtypes they’re identifying characteristics
variable vascularity
