Week 5 - Connective Tissue Series 1: Connective Tissues Characteristics
Connective tissue:
Embryonic origin - Derived from mesoderm.
Mesoderm - Forms muscle, CT and epithelium of reproductive, cardiovascular + renal systems.
Origin:
First CT is formed by mesenchyme. It contains:
Abundant Amorphous Ground Substance (AGS)
Few fibres (mainly reticular tissue)
Primitive mesenchyme cells, which give rise to:
All CT cell types
Stem cells which develop into blood cells
3 Components of CT:
Different CT types formed by differences in:
Types of cells
Types of fibres
Ratio of fibres: Cells + AGS
Fibres including collagen, elastic fibres + reticular fibres. These are elongated and have variable thickness.
Few cells, lots of intercellular material in form of fibres + AGS, which are products formed from CT cells
There are also resident cells, like mesenchymal cells, macrophages, adipocytes, fibreoblasts.
CT Cells:
There are also cells in CT. It is split up into two types:
Defence Cells:
Protect the body against invasion, involved in inflammation, immunity, healing.
Main types are macrophages, mast cells, plasma cells + white blood cells (lymphocytes, neutrophils + eosinophils)
Structural cells:
These produce CT in the first place.
They synthesise CT using cells like fibroblasts
Also act as storage sites within CT through adipocytes.
Structural CT cells are divided up into two types:
Immature cells known as blasts = builders:
Synthesis + secretion of ECM
Mature cells known as cytes or caretaker cells:
Maintain + monitor quality of ECM
Amorphous Ground Substance:
A filler material located between cells + fibres
Function:
Secures CT cells + fibres within ECM
Attracts lots of water. Functions as a medium for material exchange through CT + Blood Capillaries
Variations of AGS:
Located between cells + fibres.
Although, AGS form can vary depending on location.
For examples:
Cartilage - AGS is Semi-Fluid
Blood - AGS is Blood Plasma Fluid
Bone - Hard AGS
Most Loose + Dense CT - AGS is gelatinous
Fibres of CT:
3 Main Types:
Collagen:
Connects + binds tissues + organs
Providing strength + protection
Reticular Fibres:
More delicate + smaller
Provides a framework for support to cells. Holds cells in place for integrity
Elastic Fibres:
Can stretch and return to original state
Good for providing strength + elasticity for taking on physical force.
Classification of Different CTs:
Dependent on the proportion of cells to fibres to AGS.
If the proportion of cells + AGS is > proportion of fibres, CT is a loose CT
Hence role is most associated with functions of cells and AGS such as defence + transport.
Functions:
Stores energy + insulation
Transport nutrients/waste products between blood + epithelium
Protects body from infections
If the proportion of cells + AGS is < proportion of fibres, CT is a dense CT.
Role is most associated with connection and protection.
Dense CT can be further subdivided into types according to organisation/orientation of fibres:
Dense Regular CT: Fibres run parallel.
Good for withstanding stress in the same direction.
Transmits force + provide strength in a single direction, E.G. Tendons + Ligaments
Dense Irregular CT: Fibres run in all directions.
Good for counteracting stress + strain from all directions.
Connect + bind other tissue types + organs
Giving support + shape.
Learning Objectives:
Describe the origins of connective tissue (CT)
CT originates from the mesoderm embryonic tri-layer.
First CT is formed by mesenchyme. The CT has:
Abundant Amorphous Ground Substance (AGS)
Few fibres (mainly reticular tissue)
Primitive mesenchyme cells, which give rise to:
All CT cell types
Stem cells which develop into blood cells
Identify the structural components of CT & correlate them with their general functions
Structural cells:
These produce CT in the first place.
They synthesise CT using cells like fibroblasts
Also act as storage sites within CT through adipocytes.
Structural CT cells are divided up into two types:
Immature cells known as blasts = builders:
Synthesis + secretion of ECM
Mature cells known as cytes or caretaker cells:
Maintain + monitor quality of ECM
3 Main Types:
Collagen:
Connects + binds tissues + organs
Providing strength + protection
Reticular Fibres:
More delicate + smaller
Provides a framework for support to cells. Holds cells in place for integrity
Elastic Fibres:
Can stretch and return to original state
Good for providing strength + elasticity for taking on physical force.
Amorphous Ground Substance:
A filler material located between cells + fibres
Function:
Secures CT cells + fibres within ECM
Attracts lots of water. Functions as a medium for material exchange through CT + Blood Capillaries
Describe the basis for classification of CT types
Dependent on the proportion of cells to fibres to AGS.
If the proportion of cells + AGS is > proportion of fibres, CT is a loose CT
If the proportion of cells + AGS is < proportion of fibres, CT is a dense CT.
Dense CT can be further subdivided into types according to organisation/orientation of fibres:
Dense Regular CT: Fibres run parallel.
Dense Irregular CT: Fibres run in all directions.
Explain how the composition of individual CT types contributes to their function
The proportion of cells + AGS is > proportion of fibres, CT is a loose CT
Hence role is most associated with functions of cells and AGS such as defence + transport.
Functions:
Stores energy + insulation
Transport nutrients/waste products between blood + epithelium
Protects body from infections
If the proportion of cells + AGS is < proportion of fibres, CT is a dense CT.
Role is most associated with connection and protection.
Dense CT can be further subdivided into types according to organisation/orientation of fibres:
Dense Regular CT: Fibres run parallel.
Good for withstanding stress in the same direction.
Transmits force + provide strength in a single direction, E.G. Tendons + Ligaments
Dense Irregular CT: Fibres run in all directions.
Good for counteracting stress + strain from all directions.
Connect + bind other tissue types + organs
Giving support + shape.