Introduction to Histology & Connective Tissue – 1
Human Structure & Development ANHB 2212 Semester 1, 2010
Avinash Bharadwaj Histology – What and Why
Histology – “Study of Tissues”
By extension, microscopic structure of the body
Basic Histology – study of tissues
“Systemic Histology” – Organs and Systems
Also called microanatomy.
Histology – the basis of function
Stepping stone to cellular basis of disease (Histopathology, a medical discipline)
© 2010 Avinash Bharadwaj A Different World…!
Microscopes – many varieties
Special preparation of material
Largely two-dimensional
Interpretation, analysis and application Explained in the manual and on the web
Makes functional anatomy meaningful
© 2010 Avinash Bharadwaj Theory and Lab Work
Go hand-in-hand!
Read preliminary material – manual, website
Some lab work aimed at understanding and interpretation of slides
Concepts and functional interpretation matter most!
© 2010 Avinash Bharadwaj Primary (Basic) Tissues
Recap from ANHB 1101. Course Reader Chapter 2
Basic features of cell structure and function.
Think of : size, shape, nucleus, organelles in the context of function.
Four tissues and subtypes.
Tissue – a group of cells with a common function.
(In histological technique a “tissue” is the bit under study).
© 2010 Avinash Bharadwaj Epithelium
Covering of external surfaces
Lining of cavities
Limiting structure
Control passage of substances
Variety of other functions
Compact sheets of cells
Very little intercellular substance
Avascularity … supporting tissue required.
© 2010 Avinash Bharadwaj Muscle Tissue
Movement
Sliding filaments of proteins
Classification details later!
Three structural types.
Intimately associated with connective tissue in most places.
© 2010 Avinash Bharadwaj Nervous Tissue
Generation and conduction of nerve impulses
“Excitable”cells
Neurons and their processes
Few neuron bodies in peripheral nervous system – largely nerve fibres.
Neuroglia
© 2010 Avinash Bharadwaj Connective Tissue
Found everywhere in the body except in the CNS Wide variety of structural features Wide variety of functions Connects other structures and tissues Binds together Nutritional support Site of defense reactions Transmits and resists forces Skeletal support Yet, all varieties have a common plan!
© 2010 Avinash Bharadwaj Integration… as seen in the intestine
Muscle – movement
Lining epithelium Barrier, secretion, absorption
Supporting CT
Thin muscle layer
Entire unit : Mucosa
Submucosa – CT in between Neurons/nerve plexuses © 2010 Avinash Bharadwaj Connective Tissue
Packing, wrapping, tying together, supporting… Structural strength Many varieties, many functional properties Stretchable, yet stretch resistant Rigid, yet can be remodelled Shock absorbers, insulators…
The list is far from complete These are some “physical” functions. More later!
Cells are too soft for such mechanical strength!... …so where does this strength lie?
© 2010 Avinash Bharadwaj Connective Tissue – General Features
Matrix : intercellular (extracellular) substance
Fibres (also called “formed” elements)
Mostly protein
Ground substance (“Amorphous”)
Complex chemical composition
Cells
One principal cell type produces matrix
Other cell types may be present
© 2010 Avinash Bharadwaj Connective Tissue Matrix – Fibres
Collagen Thicker bundles, generally wavy Resist stretching or transmit forces Types : Biochemical differences Elastic material Fibres or sheets (laminae) C E Fibres thin, straight, branched Reticular fibres Not seen in routine preparations Very thin, form network R Variety of collagen Supporting network in highly cellular structures Ground substance fills all remaining space!
© 2010 Avinash Bharadwaj Matrix – Ground Substance
Protein-carbohydrate complexes
Some have special features like sulfate ions
Ground substance generally difficult to distinguish in routine sections
Variable amount.
Loosely arranged fibres more space more ground substance.
Tightly packed fibres less space, less ground substance.
© 2010 Avinash Bharadwaj Connective Tissue – Main Types
“General” – fibrous – connective tissue “proper”
Special varieties
Adipose tissue (fat)
Skeletal tissues – cartilage and bone
Lymphoid tissues
Even blood!
All connective tissue is mesodermal! (Ignore exceptions in this unit)
© 2010 Avinash Bharadwaj Connective Tissue – Cells
“Principal” cell of each type all components of matrix.
Active cell : -blast. Inactive cell : -cyte
Fibrous tissue : fibroblast / fibrocyte Fibres and a fibroblast Cartilage : chondroblast / chondrocyte Bone : osteoblast / osteocyte
© 2010 Avinash Bharadwaj Connective Tissue Proper (Fibrous tissue) Arrangement of fibres (esp. collagen) Loose Dense, irregular Dense, regular Mechanical properties differ… Loose connective tissue : additional special functions, cells other than fibroblasts.
© 2010 Avinash Bharadwaj Next Lecture…
Types of fibrous connective tissue
Cells and matrix
Mechanical properties
Other functions
Cartilage
Cells and matrix
Growth
Properties and functions
© 2010 Avinash Bharadwaj