W2 - Connective Tissue Proper Flashcards
LO1: Name the primary germ layer that connective tissue is derived from
MESODERM
- Embryonic connective tissue is called mesenchyme and ultimately gives rise to all types of connective tissue.
LO2: Describe the basic components and functions of connective tissue (name the components)
Protein fibres
Cells
Ground substance
LO2: Describe the basic components and functions of connective tissue (protein fibres)
- strengthen and support the tissue.
Collagen, elastic, and reticular (3 types)
The amount and type of fibres in a connective tissue will determine its degree of strength and support and thus, its function.
LO2: Describe the basic components and functions of connective tissue (cells)
Connective tissue is made of several different cell types that are specific to the type of connective tissue. The cells are scattered throughout the tissue rather than being tightly packed together.
LO2: Describe the basic components and functions of connective tissue (ground substance)
This is the material that the connective tissue cells and protein fibres are suspended within. It is mainly composed of protein and carbohydrate molecules with varying amounts of water.
Depending on the type of connective tissue, it can be fluid, semisolid or solid.
LO2: Describe the basic components and functions of connective tissue (functions)
- Physical protection: Connective tissue surrounds and therefore protects the organs of the body.
- Support: Connective tissue provides the framework for organs and other structures of the body.
- Binding: Connective tissue binds other tissues together. For example, ligaments connect bone to bone.
- Storage: Fat is the major form of energy storage in the body and bone stores minerals such as calcium and phosphorus.
- Transport: Blood transports several different substances such as gases, hormones, nutrients and waste products around the body.
- Immune protection: Some leukocytes, or white blood cells, can leave the bloodstream and enter the surrounding connective tissue to fight infection.
LO3: Name the five types of connective tissue and classify them as either connective tissue proper or specialised connective tissue
(Connective tissue proper) loose connective tissue and dense connective tissue
(Specialised connective tissue) bone, cartilage, and blood
LO4: Describe the cell and protein fibre types in connective tissue proper (describe connective tissue proper)
- A mixture of different connective tissue cell types and protein fibres within a viscous ground substance
- The amount and type of cells, protein fibres and ground substance will determine the properties of the connective tissue.
LO4: Describe the cell and protein fibre types in connective tissue proper (cells in connective tissue proper)
Classified as either resident or wandering cells.
- Resident cells are fixed within the connective tissue and are responsible for supporting and maintaining the extracellular matrix.
- Wandering cells move throughout connective tissue, involved in immune protection and tissue repair. Primarily types of leukocytes, or white blood cells, that have left the bloodstream and entered the surrounding connective tissue.
LO4: Describe the cell and protein fibre types in connective tissue proper (resident cells)
Fibroblasts
These are the most abundant resident cell type in connective tissue proper and are responsible for producing the protein fibres and ground substance (i.e. extracellular matrix). They are large, flat cells with tapered ends and a flattened, centrally located nucleus.
Adipocytes
These are more commonly known as fat cells and are found in clusters within some types of connective tissue proper. They are large cells containing a central lipid droplet, which pushes the nucleus to the periphery of the cell.
LO4: Describe the cell and protein fibre types in connective tissue proper (wandering cells)
Mast Cells
These are small cells with a granule-filled cytoplasm. They are involved in inflammatory responses, releasing substances from their granules including heparin to prevent blood clotting and histamine to dilate blood vessels and therefore increase blood flow to the tissue.
Plasma Cells
These are the activated form of a type of leukocyte called B-lymphocytes. They produce antibodies, which are proteins that fight specific antigens, or foreign bodies that induce an immune response.
Macrophages
These are the differentiated form of a type of leukocyte called monocytes. They are phagocytic, meaning they engulf anything that is foreign or damaged.
Other Leukocytes
In addition to plasma cells and macrophages which are derived from B-lymphocytes and monocytes, respectively, other leukocytes are also found in connective tissue proper. These are mainly neutrophils, which are a type of leukocyte that are primarily involved in the response to bacterial infection. They are phagocytic, meaning they engulf the bacteria causing the infection.
LO4: Describe the cell and protein fibre types in connective tissue proper (protein fibres)
Collagen Fibres
Collagen is the most abundant protein in the body. There are four subtypes of collagen which are specialised for specific functions. In connective tissue proper, it forms long, cable-like fibres that are strong and flexible. In histological slides, collagen fibres usually appear pink.
Elastic Fibres
These are thin fibres that contain the protein elastin, making them stretchy and capable of recoiling. In histological slides, elastic fibres usually appear wavy and black.
Reticular Fibres
These are thin, delicate fibres composed of type III collagen. In connective tissue proper, they intertwine to form strong, flexible networks (reticular = network).
LO5: Describe the structure, function and location of the different types of loose and dense connective tissue (describe loose connective tissue)
Loose connective tissue = lower proportion of cells and protein fibres and a relatively higher proportion of ground substance
- protein fibres are loosely arranged within the ground substance
- Forms the “packing material” of the body, as it fills the space around organs, blood vessels, nerves and other structures.
3 types = areolar connective tissue, adipose connective tissue and reticular connective tissue.
LO5: Describe the structure, function and location of the different types of loose and dense connective tissue (adipose connective tissue)
Primarily composed of adipocytes, or fat cells, which are tightly packed within the viscous ground substance.
Its main functions are to store energy, provide cushioning and shock absorption for organs and act as an insulator to minimise heat loss.
It is found in the subcutaneous layer underneath the skin and surrounding organs such as the kidneys.
LO5: Describe the structure, function and location of the different types of loose and dense connective tissue (areolar connective tissue)
The most abundant type of loose connective tissue in the body.
It contains all connective tissue cell and protein fibre types and these are loosely arranged within the viscous ground substance, which constitutes most of the volume of areolar connective tissue.
The main function of areolar connective tissue is to support, protect and bind other tissues and structures in the body.
It is found in the dermis layer of the skin, in the subcutaneous layer underneath the skin and surrounding organs, blood vessels, nerves and other structures.
LO5: Describe the structure, function and location of the different types of loose and dense connective tissue (reticular connective tissue)
This is composed of a network of reticular fibres as well as scattered fibroblasts and leukocytes within the viscous ground substance.
Due to the mesh-like arrangement of reticular fibres, the main function of reticular connective tissue is to form the framework of organs, which is called stroma.
It is found forming the stroma of the liver, spleen, thymus and lymph nodes.
LO5: Describe the structure, function and location of the different types of loose and dense connective tissue (describe dense connective tissue)
Relatively higher proportion of cells and protein fibres and a relatively lower proportion of ground substance
It is primarily composed of protein fibres and these are tightly packed within the ground substance rather than being loosely arranged.
The predominant protein fibre type in dense connective tissue is collagen fibres.
3 types = dense regular connective tissue, dense irregular connective tissue and elastic connective tissue.
LO5: Describe the structure, function and location of the different types of loose and dense connective tissue (elastic connective tissue)
This is primarily composed of elastic fibres, with fibroblasts scattered in the spaces between the fibres.
Due to the abundance of elastic fibres, the main function of elastic connective tissue is to allow structures to stretch and then recoil back to their original shape.
It is found in the walls of elastic arteries and parts of the respiratory tract such as the trachea and bronchi, as well as in the vocal cords and some ligaments.
LO5: Describe the structure, function and location of the different types of loose and dense connective tissue (dense regular connective tissue)
This is composed of tightly packed collagen fibres arranged in parallel bundles, with fibroblasts arranged in rows in between these bundles.
The bundles of collagen fibres are aligned in the direction in which forces are applied to the tissue, making it capable of resisting stress in one direction.
The main function of dense regular connective tissue is to bind other structures together. It is found in ligaments, which connect bone to bone, and tendons, which connect muscle to bone.
LO5: Describe the structure, function and location of the different types of loose and dense connective tissue (dense irregular connective tissue)
This is composed of tightly packed collagen fibres arranged in bundles that are aligned in different directions, with fibroblasts scattered in the spaces between these bundles.
The random alignment of the collagen bundles makes dense irregular connective tissue capable of resisting stress in multiple directions.
Its main function is therefore to protect other tissues and organs from forces applied to them in multiple directions.
It is found in the dermis layer of the skin, in the periosteum and perichondrium, which are the connective tissue coverings of bone and cartilage, respectively (‘peri’ = around, ‘osteum’ = bone, ‘chondrium’ = cartilage), and in the capsules of organs such as the liver, kidneys and spleen.
