Introduction To Histology Flashcards
Organs are composed of
Tissues
Tissues consist of
Cells and their products
Cells are
Individually functional units, varying in form, size, and function
Histology is the
Study of cells and the tissues they form
5 steps for preparation of cells/tissues to be examined under the microscope
-Fixation
-Processing
-Embedding
-Sectioning
-Staining
Fixation (4)
-most important step
-fixatives (chemicals) used to preserve cellular structure by halting the processes of autolysis & decay and stabilizing proteins
-must be buffered to match pH and osmolarity of tissue
-10% neutral buffered formalin (NBF) most commonly used
Processing (3)
-infiltration with a paraffin wax formulation to keep tissue rigid
-tissue must first be dehydrated through a series of increasing concentrations of alcohol
-tissue then cleared of alcohol using xylene then infiltrated with paraffin wax under vacuum
Embedding
Paraffin-infiltrated tissue is embedded into a wax block
Sectioning
Using a microtome, sections are cut from the block and mounted onto glass slides
Staining (2)
-wax is removed by reversing prior steps (xylene —> decreasing alcohol series —> water)
-sections are stained to enable identification of different cell types and constituents
Most common stain
Haematoxylin and Eosin (H&E):
Haematoxylin is alkaline (binds to acids, blue)
Eosin is acidic (binds to alkali, pink)
Four main tissue types
-epithelial
-connective
-muscle
-nervous
Three types of embryonic germ layers
-ectoderm
-mesoderm
-endoderm
Gastrulation is
A series of cell re-arrangements occurring after fertilization and multiple cell division have occurred
What are the outer, middle, and inner layers of the embryonic germ layer
Outer: Ectoderm
Middle: Mesoderm
Inner: Endoderm
Epithelial Tissue (4)
-sheets of cells that form a lining
-externally = skin
-internally = lining of digestive, urogenitial and respiratory tracts, blood vessels
-forms glands
Three main types of connective tissue
-connective tissue proper (ligaments, tendons, adipose tissue)
-cartilage and bone
-blood
Connective tissue (3)
-provides physical support (cartilage and bone)
-provides physiological support (blood)
-used as packing between tissue (adipose, fascia, ligaments, tendons)
Three main types of muscle tissue
-skeletal (striated): voluntary movement
-smooth: not under voluntary control; found in viscera
-cardiac (the heart)
Nervous tissue (3)
-enables body to process and respond to information from external and internal environments
-consists of neurons (responsible for transmitting electrical impulses) and support cells
-brain, spinal cord, nerves, sensory receptors
