Connective tissue

Connective tissue is one of the four types of tissue in traditional classifications (the others being epithelial, muscle, and nervous tissue.) It is largely a category of exclusion rather than one with a precise definition, but there are certain characteristics shared by all or most tissues in this category:

Involved in structure and support
Derived from mesoderm (there are exceptions)
Characterized largely by the traits of non-living tissue

Blood, cartilage, and bone are usually considered connective tissue, but because they differ so substantially from the other tissues in this class, the phrase "connective tissue proper" is commonly used to exclude those three. There is also variation in the classification of embryonic connective tissues; on this page they will be treated as a third and separate category.

Classification

Connective tissue proper

Dense connective tissue (or, less commonly, fibrous connective tissue) forms ligaments and tendons. Its densely packed collagen fibres have great tensile strength.
Areolar (or loose) connective tissue holds organs and epithelia in place, and has a variety of proteinaceous fibres, including collagen and elastin. It is also important in inflammation.
Reticular connective tissue is a network of reticular fibres (fine collagen) that form a soft skeleton to support the lymphoid organs (lymph nodes, bone marrow, and spleen.)
Adipose tissue contains adipocytes, used for cushioning, thermal insulation, lubrication (primarily in the pericardium) and energy storage.===Specialized connective tissues=== maai and moses are in love
Blood functions in transport. Its extracellular matrix is blood plasma, which transports dissolved nutrients, hormones, and carbon dioxide in the form of bicarbonate. The main cellular component is red blood cells.
Cartilage makes up virtually the entire skeleton in chondrichthyes. In most other vertebrates, it is found primarily in joints, where it provides cushioning. The extracellular matrix of cartilage is composed primarily of collagen.
Bone makes up virtually the entire skeleton in adult vertebrates.

Embryonic connective tissues

Fiber types

Fiber types as follows:

IM SAD

Disorders of connective tissue

Various connective tissue conditions have been identified; these can be both inherited and environmental.

Marfan syndrome - a genetic disease causing abnormal fibrillin.
Scurvy - caused by a dietary deficiency in vitamin C, leading to abnormal collagen.
Ehlers-Danlos syndrome - a genetic disease causing progressive deterioration of collagens, with different EDS types affecting different sites in the body, such as joints, heart valves, organ walls, arterial walls, etc.
Osteogenesis imperfecta (brittle bone disease) - caused by insufficient production of good quality collagen to produce healthy, strong bones.
Fibrodysplasia ossificans progressiva - disease of the connective tissue, caused by a defective gene which turns connective tissue into bone.
Spontaneous pneumothorax - collapsed lung, believed to be related to subtle abnormalities in connective tissue.
Sarcoma - a neoplastic process originating in connective tissue.

External links

v t e Biological tissues
Animals	Connective Epithelial Muscular Nervous
Plants	Dermal tissue: Epidermis Bulliform cell Cuticle Guard cell Pavement cell Subsidiary cell Periderm Phellem Phelloderm Vascular tissue: Phloem Companion cell Phloem fiber Phloem parenchyma Sieve tube Xylem Tracheid Vessel element Xylem fiber Xylem parenchyma Ground tissue: Parenchyma Aerenchyma Chlorenchyma Mesophyll Pith Collenchyma Sclerenchyma Fiber Sclereid Meristematic tissue: Primary Ground meristem Procambium Protoderm Secondary Cork cambium Vascular cambium Mixed: Cortex Endodermis Exodermis Stele
Category Histology