Histopathology Flashcards
Define Histology and Pathology
Histology:
Study of the anatomy of cells and tissues of plants and animals and the study of their composition and function
- All diseases are alterations of normal histology
Pathology:
Study of nature and cause of disease
- Normal Pathology -> Pathogenesis -> Disease
Why do we stain?
- Most cells are transparent
- Histological sections have to be stained to make cells and their contents visible in order to determine cell type, tissue, pathology
- Staining with acidic and basic dyes allows visualisation of different organelles
What are the different properties of H&E stains?
- Most common histological stain
Haematoxylin (“H”)
:
- Blue
- stains like a basic dye
- Reacts with nucleic acids: DNA in the nucleus, RNA in ribosomes and in rough endoplasmic reticulum; carbohydrates in cartilage
Eosin (“E”)
:
- Pink
- acidic dye: negatively charged
- reacts with proteins, filaments in muscle cells, intracellular membranes, extracellular fibres
What are artefacts and the different types?
Artefact = pseudo-structure
- Scratch
- Fold
- Bubble
- Foreign Material
What are tissues and the four primary types?
Tissues = Groups/layers of similar specialised cells with common function
- Epithelial Tissue
- Muscle Tissue
- Connective Tissue
- Nervous Tissue
What are the roles and common characteristics of Epithelial tissue?
Roles:
- Secretion
- Barrier
- Absorption
- Protection
- Transcellular transport
- Sensing
Common Characteristics:
- Have polarity
- Highly cellular
- Cell to cell contacts
- Avascular
- Have nerve supply
- Epithelial cells resting on basement membrane
What is the structure and function of the basement membrane?
Structure:
- Mainly made of collagen fibres and glycoproteins
- Always sits on a bed of loose connective tissue
- Often stains very pink in H&E stain
Function:
- anchors epithelium to lose connective tissue
- forms organised scaffold to provide structural support
What are the different specific epithelial tissues?
- Simple Cuboidal
- Simple Squamous
- Simple Columnar
- Stratified Squamous
- Pseudostratified Columnar
What are the different specialisations of epithelial tissues?
Hint: All occur on the apical surface (portion of the cell exposed to the lumen)
Keratin
- Dead cell layers
- Function: Protection & barrier
- Extremely insoluble in water
Microvilli
Cillia
What is the difference between microvilli and cillia?
Cilia:
- About 10µm
- Anchored with basal body
- Transport mucus along surface
Microvilli:
- ~1 µm
- Increase surface area
- Absorption
What are the roles and common characteristics of Muscle Tissue?
Role: Movement
Common Characteristics:
- Can contract
- Highly cellular
- Highly vascular
- Contains myofilaments
What are the different specific muscle tissues?
- Skeletal Muscle
- Cardiac Muscle
- Smooth Muscle
What are the characteristics of skeletal muscle?
- Striated
- Nuclei near cell membrane
- Multiple nuclei per cell
- Voluntary contraction
What are the characteristics of cardiac muscle?
- Striated
- Intercalated Discs
- Branched
- Involuntary contraction
- Uni-nucleated
What are the characteristics of smooth muscle?
- Fusiform
- Nucleus central
- Involuntary contraction
- Lack striations
Often presents in two different planes
:
- Inner layer of smooth muscle tissue -> transverse section -> ”circular”
- Outer layer of smooth muscle tissue -> longitudinal cut of cells
What are the roles and common characteristics of connective tissue?
Roles:
- Support
- Protection
- Insulation
- Transport
- Storage
Common Characteristics:
- Very variable type of tissue
- Can be vascular or not
- Extracellular matrix between cells
What are the structure and function of extracellular matrix?
Structure:
- Fibres embedded in ground substance
- Ground substance mainly tissue fluid
Function:
- Scaffold between cells
- Biochemical support to the surrounding cells
What are the different specific connective tissues?
- Blood
- Adipose Tissue
- Bone
- Cartilages
- Dense (Irregular/Regular)
What are the roles and common characteristics of Nervous Tissue:
Role: Communication and Control
Common Characteristics: Highly Cellular
Found in the nervous system
- Central nervous system (CNS): brain, spinal cord
- Peripheral nervous system (PNS): ganglia
What are the different specific nervous tissues?
Neurons:
- excitable cells transmit electrical signals
Glial Cells:
- supporting cells
- Eg. Oligodendrocyte
s and Astrocytes
What is the structure of blood vessels?
Hint: Three layers (tunics)
Tunica adventitia = outer layer
- connective tissue with collagen fibres
Tunica media = middle layer
- circularly arranged smooth muscle and elastic fibers
Tunica intima = inner layer
- specialised simple squamous epithelium, often called the endothelium
Note: capillaries only have intima layer
What is the difference between veins arteries and capillaries?
Veins:
- Vein walls thinner than walls of arteries
- Veins can have valves
- Vein diameter is larger than of arteries
- Layering in the wall of veins is not very distinct compared to arteries
Arteries:
- Walls of arteries thick and compact
- Smooth muscle cell nuclei are frequent in the tunica media
- Collagen fibres and a few connective tissue cell nuclei are visible in the tunica adventitia
Capillaries:
- Very small vessels (diameter 4-15 µm)
- Wall of a segment of capillary may be formed by a single endothelial cell
- Low rate of blood flow and large surface area
- Functions:
provide nutrients and oxygen to surrounding tissues, absorption of nutrients, waste products & carbon dioxide, and excretion of waste products
