Week 5: Connective Tissue 1 - Connective Tissue Classifications and Components

Question 1

Describe the origins of CT.

Answer 1

CT is derived from the mesoderm (middle) layer of embryonic tissue.
The first CT formed is mesenchyme.

Question 2

What is mesenchyme?

Answer 2

The first CT formed is mesenchyme, which contains:
- Primitive mesenchyme cells
- Abundant AGS
- Few fibres (mainly reticular fibres)

Question 3

What does mesenchyme give rise to?

Answer 3

Primitive mesenchyme cells give rise to:
- CT cells
- Stem blood cells

Question 4

What are the structural components of CT?

Answer 4

CT consists of cells, fibres and amorphous grounds substance.
CT has few cells and much intercellular material (fibres and AGS)

Question 5

What types of cells are found in CT?

Answer 5

• Structural cells: these synthesis (e.g., fibroblasts) and store (e.g., adipocytes)
• Immature cells, known as ‘blasts’=builders: these synthesise and secrete ECM, and divide and differentiate into mature cells.
• Mature cells, known as ‘cytes’: these are referred to as caretaker cells, i.e., maintain and monitor quality of ECM
• Defence cells: these protect the body against invasion. The main types seen are macrophages, mast cells, plasma cells adn white blood cells (lymphocytes, neutrophils and eosinophils)

Question 6

How does AGS differ in different locations?

Answer 6

• Fluid in blood
• Semifluid in cartilage
• Gelatinous in most loose and dense CTs
• Hard in bone

Question 7

Where is AGS found?

Answer 7

Located between cells and fibres

Question 8

What is the function of AGS?

Answer 8

Functions to provide medium for substance exchange, secures CT cells and fibres within the ECM

Question 9

What fibres types are found in CT? What are their functions?

Answer 9

Collagen: this is the main fibre, and it provides strength
Reticular: more delicate and smaller, providing a net-like framework
Elastic: provides strength and elasticity

Question 10

How can CT be classified?

Answer 10

• Types of cells
• Types of fibres
• Proportions of cells to fibres to AGS: if proportion of cells + AGS/ matrix > proportion of fibres, the CT is a loose CT. If proportion of cells + AGS/ matrix < proportion of fibres, the CT is a dense CT
• Organisation/ orientation of fibres (in dense CT): dense regular: fibres run parallel, these are good at withstanding tensile stresses (strong in 1 direction). Dense irregular: fibres run in all directions, these are good for counteracting stresses and strains in all directions.

Question 11

What is the function of a CT related to?

Answer 11

Related to the components that are present in the greatest quantity.

Question 12

What are functions of dense irregular CT?

Answer 12

• Connects and binds other tissue types and organs
• Provides mechanical protection

Question 13

What are functions of dense regular CT?

Answer 13

• Transmits force or provides strength in a single direction, e.g., tendons and ligaments
• Gives support and shape (special CT), e.g., cartilage and bone

Question 14

What are functions of loose CT?

Answer 14

• Stores energy and acts as insulation
• Transports nutrients/ waste products between blood and epithelium etc.
• Protects body from infections (involved in inflammation, immunity, healing)