Integrated Histology Tissue Flashcards
What are the 4 general characteristics of Epithelium tissue?
-Polar Orientation
-Lateral surfaces that are connected to neighbouring cells by anchoring junctions
-Avascular
-Innervated
What is meant by apical surface (apex)?
The surface that faces the lumen or body cavity
What is a basal surface or basement membrane?
The side of the cell that anchors the epithelium onto the body by attching istelf to underlying tissue
Briefly explain what desmosomes are.
The are a form of anchoring junction binding the epithelia cells together
Briefly explain what hemidesmosomes are.
They are a form of anchoring junction binding the epithelia to the basement membrane
What are the functions of anchoring junctions?
Assure tissue cohesion (strength)
What are tight (occluding) junctions?
Two pathways:
-Paracellular (between adjacent plasma membranes)
-Transcellular pathway (through the cell)
What is the function of a tight junction?
Control the entrance of specific compounds (nutrients/oral therapeutics) that have come from the intestinal lumen & must diffuse towards the blood vessels
-Limit paracellular movement of water & other molecules
What are Gap junctions?
Aqueous channels allowing small molecules (Molecular Weight ≤ 1000Da) to pass between adjacent cells.
They also allow for electrical impulses to directly pass through
What is the main function of gap junctions?
Allow for communication between the cells
What are the 3 main atypical modifications of epithelia?
Cilia
Microvilli
Stereocilia
What is the function of cilia?
Where is cilia located?
They a motile, long cell processes that move substances along
They are commonly found in the respiratory tract, oviduct & uterus)
What is the function of microvilli?
Where is it located?
Non motile, tiny projections whihc are specialised for absorption by increasing SA
Found in kidneys & intestines
Wat is the function of stereocilia
Where is it found?
Non motile, long villi whihc increase SA for absorption
Found within both parts of the male reproductive tract
What are the two things we classify epithelia by?
Morphology (cell shape & arrangement)
Function (glandular or non glandular)
What is simple epithelium?
Single layer of cells all attached to the basement membrane
What is stratified epithelium?
Multiple layers of cells
Relate the properties of simple squamous cell to its function
Flat thin cells so they are ideal for passive transport
-Found lining blood vessels and in Alveoli
Relate the properties of simple columnar & simple cuboidal cell to their functions
Square like cells (columnar go slightly deeper than cuboidal). They are markedly polarised and often have atypical modifications making them ideal for absorption and secretion
-Simple Cuboidal: Thyroid, Kidney, Lung, Ovary, Ducts & Secretory portions of many glands
-Simple Columnar: Intestine, Female reproductive tract, Many Exocrine glands
Relate the properties of simple pseudostratified columnar cells to their functions
Nuclei are not orientated in one level, giving the impression of multilayers. These are ideal for the secretion & movement of particles along tubular organs
-Found in trachea, bronchi, male reproductive tract
Relate the properties of stratified squamous cells to their functions
Start off on the basement membrane edge then as they mature and move up become flatter. Forms a stratified squamous epithelium on the surface that protects underlying tissues and prevents their desiccation
It can be keratinised or no keratinised
Relate the properties of stratified cuboidal & columnar cells to their functions
Not abundant & tend to cover transitional areas between simple and stratified epithelium
-Respiratory Tract, Ducts of Exocrine glands (bilayers)
Relate the properties of transitional epithelium cells to their functions
As the bladder distends and fills with urine these cells flatten out going from the appearance of thick stratified columnar to thin stratified squamous
Some of the surface cells are binucleated
Allow for great change in volume for an
Organ whilst retaining watertight
Found in Renal Pelvis, Ureter, Urinary Bladder, Urethra
What of the 5 classifications of epithelial glands?
Method of Secretion
Type of Secretion
Type of Secretion Product
Shape
Cell Numbers
What are endocrine glands?
Glands that lack a duct system and have no connections to external or internal surfaces
-Produce hormones
-Near blood vessels
What are exocrine glands?
Glands that posses ducts and secrete product to a lumen or free surface
What do Exocrine glands secrete?
-Merocrine: exocytosis, cell membrane intact (most glands are merocrine; e.g. pancreas)
-Holocrine: cell membrane rupture: detachment and cell death (e.g. sebaceous glands)
-Apocrine: “decapitation” secretion (e.g. mammary glands, sweat glands)
What types of secretion product to exocrine glands produce?
-Serous: Clear, watery fluid (e.g. exocrine pancreas)
-Mucous: more viscous fluid (e.g. goblet cells, sebaceous glands)
-Mixed: mixture of serous and mucous (e.g. some salivary glands)
Describe the shapes of Endocrine glands
High diversity in morphology
-Simple tubular
-Simple acinar
-Compound acinar
Describe the shapes of exocrine glands
-Of the secretory component: Tubular or acinar
-Of the tubular system: Simple (one unbranched tube) or compound (branched tubules)
Outline the 8 stages of preparing a histological slide
Tissue Collection
Fixation
-10% Formalin- prevents rotting
-Trimming- Rids of any unwanted parts
Dehydration
-Series of alcohol with increasing concentration up to 100%
-Usually be handled by a Pathologists team
Paraffin Embedding
-Rigidify the specimen
Sectioning
-Use a microtome to section (3-4µm)
Straightening
-Begin to curl due to the sectioning, use a water bath to straighten them
Transferring to a slide
-Stain to view
-Coverslip to protect
Staining & Cover slipping
What are the two stains generally used on a histological slide?
Haematoxylin & Eosin
What does Haematoxylin stain?
Stains mainly genetic material (DNA/RN)
Blue
What does Eosin stain?
Stains mainly proteins (mostly in the cytoplasm)
Pink
Outline 5 benefits of staining
View the architecture of the tissue by looking at the cellular level
-locations & position of the cell
-cell size
-Contours & shapes of cells
-staining intensity of cells and their nuclei
