introduction to histology & connective tissue – 1 human structure & development anhb 2212...
TRANSCRIPT
Introduction to Histology&
Connective Tissue – 1
Human Structure & Development ANHB 2212
Semester 1, 2008
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)
A Different World…!
Microscopes – many varieties
Special preparation of material
Largely two-dimensional
Interpretation, analysis and application
Makes functional anatomy meaningful
Theory and Lab Work
Go hand-in-hand!
Read preliminary material – manual,
website (Week 1)
Some lab work is aimed at understanding
and interpretation of slides
Concepts and functional interpretation
matter most!
Primary (Basic) Tissues
Recap from ANHB 1101.
Four tissue and subtypes.
Tissue – a group of cells serving a common
function.
(In histological technique the term is used
in a slightly different sense).
Epithelium
Covering of external surfaces Lining of cavities Limiting structure
Control passage substances across Variety of other functions Compact sheets of cells Very little intercellular substance Basement membranes Avascularity … supporting tissue required.
Muscle Tissue
Movement
Sliding protein filaments in cytoplasm
Classification details later!
Three structural types.
Intimately associated with connective
tissue in most places.
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
Connective Tissue
Ubiquitous 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!
Entire unit : Mucosa
Muscle – movement
Lining epitheliumBarrier, secretion, absorption
Supporting CT
Thin muscle layer
Submucosa – CT in between
Integration… as seen in the intestine
Neurons/nerve plexuses
Connective Tissue – General Features
Large amount of intercellular (extracellular) substance called matrix Fibres (also called “formed” elements)
Mostly protein, but in some cases combined with other substances
Ground substance (“Amorphous”) Complex chemical composition
Cells One principal type of cells produces matrix Other cell types may be present
Connective Tissue Matrix – Fibres
Collagen Thicker bundles, generally wavy Resist stretching or transmit forces Types of collagen – biochemistry and electron
microscopy Elastic material (“Elastica”)
Fibres or sheets (laminae) Fibres thin, straight, branched Biochemical composition
Reticular fibres Variety of collagen – not seen in routine
preparation Very thin, form network Abundant as supporting tissue in highly cellular
structures
Matrix – Ground Substance
Variety of biochemical compounds Protein-carbohydrate complexes Some have special features like
sulfate ions Ground substance generally difficult
to distinguish in routine sections Variable amount in different
connective tissues.
Connective Tissue – Main Types
“General” – fibrous – connective tissue “proper”
Special varieties Adipose tissue Skeletal tissues – cartilage and bone Lymphoid tissues Even blood!
All connective tissue is mesodermal!
Connective Tissue Proper
Principal cells – “fibroblasts” Fibroblasts are active cells When resting, usually called fibrocytes.
Classified into types (somewhat overlapping!)
Classification mainly based on fibre arrangement and density. Loose connective tissue (“Areolar” Tissue) Dense, irregular tissue Dense, regular tissue
Loose Connective Tissue Fewer fibres Abundant ground substance Functions
Supports epithelia Mechanical support Blood vessels and nerves
Separates and covers individual muscle cells and their small bundles
Also carries blood vessels and nerves Loose collagen bundles allow movement to a
certain extent (give examples!) but limit it as well
Elastic fibres allow restoration after movement (think of elastic fibre damage!)
Site of formation of tissue fluid Often site of initial defense reactions
Loose Connective Tissue – 2 Other cells
Fixed cells Wandering cells
White blood cells Others (may be derived from WBCs) Most cells other than fibroblasts involved in
defense reactions and associated vascular changes
(More details next time!)
Ep
Dense Irregular Tissue
Denser, more abundant fibre bundles Often like sheets of cloth Binds and separates structures (like
muscles) Deep fascia is a good example Also, thick capsules of organs
Forms the dermis of the skin Also carries major blood vessels and
nerves of skin
Ep
Dense Regular Tissue
Orderly or parallel bundles Arranged in the direction of forces to
be resisted Thick bundles Tendons, ligaments (also cornea) Most principal cells seen as resting
cells Fibrocytes Flattened between fibre bundles
Ep
Next Week…
More on fibres and cells Cartilage as a connective tissue More illustrations!...
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