Development 3 Flashcards
Tissues
a group of cells similar in structure that perform common or related function.
• Histology: study of tissues.
• Pathology: A branch of medical specialization concerned with the study of the morphologic aspects of disease.
Which of the following tissue types would you expect to find on a surface of the body that is subjected to friction?
A. Epithelial tissue
B. Connective tissue
C. Muscle tissue
D. Nervous tissue
A. Epithelial tissue
The four basic tissue types
- Epithelial (Covers)
- Connective (Supports)
- Muscle (Moves)
- Nervous (Controls)
Epithelial Tissue
2 major categories
- Covering and lining epithelium lines internal (hollow organs, body cavities, ducts) or external surfaces (skin).
- Glandular(lines internal organs and releases muscous and other fluids,)epithelium is formed by cells specialized in producing secretions.
The 5 characteristics
- Polarity
- Specialized contacts
- Supported by connective tissues
- Avascular, but innervated
- Regeneration
Polarity
Epithelial cells have polarity (top vs. bottom).
• Apical surface exposed to surface or cavity, borders open space
• Basal surface attached to underlying connective tissue, next to underlying connective tissue
Specialized Contacts
Epithelial cells need to be together to form a tight barrier.
To achieve this, adjacent epithelial cells form two types of connections:
• tight junctions (impermeable to substance)
• desmosomes (anchoring structure)
Specialized Contacts
Epithelial cells need to be together to form a tight barrier.
To achieve this, adjacent epithelial cells form two types of connections:
• tight junctions (impermeable to substance)
• desmosomes (anchoring structure)
Supported by Connective Tissues
All epithelia are supported by connective tissue.
Their boundary is known as the basement membrane.
• consists of basal lamina (secreted by epithelial layer) and reticular lamina (produced by connective, a layer that sometimes sits below the basal and serves to anchor the basal to connecting tissues
Cancerous cells
Not contained by the basement membrane can invade underlying tissues resulting in try spread of cancer(methasis)
Cancerous cells
Not contained by the basement membrane can invade underlying tissues resulting in try spread of cancer(methasis)
Avascular but inverted
Epithelial tissues does not contain blood vessels
How do epithelial cells receive nutrients
Through diffusion of substances from the underlying connective tissue, through the basement membrane or other transport mechanism from the apical and lateral surfaces of the cell
- epithelial tissues are supplied by nerve fibres(innervated)
Regenerative
Epithelial cells undergo rapid cell division to replace damaged cells (as long as they receive adequate nutrition).
Example:
The skin undergoes constant shedding by removing the superficial layer of the epithelium.
Classification of Epithelail Tissue
How many layers does the epithelium has
• Simple (single-layered)
• Stratified (multi-layered)
• Pseudostratified (one layer of cells that rest on the basement membrane, but appears to have several layers)
- appears stratified because the cell nuclei are at different levels
When would a simple epithelium be useful?
Absorption, secretion and filtration
When would a stratified epithelium be useful
High abrasion and protection
What is the cell shape
What is the cell shape?
• Squamous (flat)
• Cuboidal (as tall as they are wide)
• Columnar (taller than they are wide)
The shape of the nucleus conforms to that of the cell.
Transitional Epithelium
A special type of stratified epithelial tissue that change shape when stretched.
Other structures associated with the epithelial tissue
• Goblet cells: mucus-producing cells. Are a unicellular exocrine gland
• Cilia: cell structure that move materials across the cell surface.
Grandular Epithelium
contain glands that secrete aqueous fluid.
Depending on site of release, they are classified as:
• endocrine: internally secreting (example: hormones)
• exocrine: externally secreting (example: sweat)
- they are either unicellular or multicellular
Where would you find goblet cells?
In the epithelial linings of the intestinal and respiratory tracts