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CONNECTIVE TISSUE
The Major Structural Constituents of The Body
Tissue: A DefinitionA group of connected, interdependent cells that cooperate to perform a specific function
Categories of Tissue1. Epithelial Tissue
2. Connective Tissue
3. Muscle Tissue
4. Nervous Tissue
Function of CT
• Responsible for providing and maintaining form in the body.
• Provide a matrix that connects and binds cells and organs and ultimately supports body.
Components of CT
• Cells
• Extracellular matrix– Fibers
• Collagenous, reticular, elastic
– Ground substance• Hydrophilic macromolecules (glycoproteins,
glycosaminoglycans, proteogycans) bind to receptors on cells and add strength and rigidity to matrix
CT Cells• Fibroblasts• Synthesis of all fibers, ground substance.• Mast cells*
– Contain granules with histamine, heparin, leukotrienes.• Macrophages*
– Phagocytosis• Plasma cells*
– Derived from lymphocytes, produce antibodies.
• * Originate from hematopoietic stem cells in bone marrow, circulate in blood, move to CT where they remain and perform their functions
Fibroblasts
Synthesize collagen, elastin and macromolecules of ground substance.Rarely rarely undergodivision.
Fibroblasts (inactive)
Collagenous Fibers
• Collagenous– Most common protein in the body (30% of dry
weight)– Stain pink– Make up mesenteries, tendons, cartilage,
ligaments, lamina propria, every organ.
Collagenous Fibers(Dense Irregular CT)
Reticular CT(Adrenal Cortex)
Reticular Fibers
• Reticular– Are not stained by H&E, stain black with silver– Very delicate; hold cells together in organs.– Provide framework for spleen, lymph nodes,
red bone marrow, liver, endocrine glands.– Makes flexible network in arteries, intestinal
muscle layer, uterus
Reticular Fibers
Elastic Fibers
• Stretchable, highly resistant to pulling forces.
• Found in arteries, cartilage, mesenteries
Extracellular Matrix
• Fibers– Collagenous (collagen)– Reticular (collagen)– Elastic (elastin)
• Amorphous ground substance– Gel-like matrix in which fibers, cells are
embedded and through which fluid diffuses.
• Tissue fluid
Reticular CT
Collagen, Elastic Fibers(Areolar CT)
ADULT CT• CT proper
– Loose
– Reticular
– Adipose
– Dense irregular
– Dense regular• Collagenous
• Elastic
• Specialized CT– Cartilage
– Bone
– Blood
Loose (Areolar) Conn Tissue
Structure
Many cells
Jello-like matrix
Collagen + elastic fibers
Binding Tissue
Function: Binds organ parts together
Sample Locations: Skin, kidney, lungs
Loose CT
Elastic, Reticular Fibers
Dense Irregular CT
Dense Irregular CT
Section of rat skin. The subepithelial connective tissue (dermis) is loose connective tissue. In this area, the cells, most of which are fibroblasts, are abundant. The deepest part of the dermis consists of dense irregular connective tissue, which contains many randomly oriented thick collagen fibers, scarce ground substance, and few cells. H&E stain. Medium magnification. (Courtesy of TMT Zorn.)
Elastic Connective Tissue
Dense Regular C T
Structure
Few cells
Dense matrix
Aligned collagen fibers
DENSE CT