Learning Objectives  Sites  Function  Composition  Types  Ligament & Tendon  Cartilage  Bone

Connective Tissue One of four basic types of tissues  Epithelium  Connective tissue  Muscle  Nervous tissue

Sites

Functions  Binding and support – Tendon & Ligament  Support and moving – Bone & Cartilage  Insulation – Adipose  Energy Store – Adipose  Transportation – Blood  Compartmentalizes structures i.e skeletal muscle  Immunity – Cells of immune system

Connective Tissue Extracellular Matrix Fibers – collagen,reticular&elastic “Ground substance” Cells Fixed: ???? Free: Immune cells (lymphocytes) Inflammatory cells (neutrophils,mast cell & macrophages)

General Features  Does not present on free surfaces nor body cavities  Has a nerve supply (except cartilage)  Highly Vascular (except cartilage and tendons)  Can replicate (healing & repair)

Cells  Fibroblasts – connective tissue proper  Chondroblasts – cartilage  Osteoblasts – bone  Hematopoietic stem cells – blood  White blood cells, plasma cells, macrophages, and mast cells

Connective Tissue Figure 4.5

Matrix  Ground Substance: Component of a connective tissue between the cells and fibers, supports cells, binds them together, and provides a medium through which substances are exchanged. Hyaluronic Acid Glycosaminoglycans (GAG’s) Proteoglycans Fibronectin and Laminin

Protein Fibers  Collagen  Elastic fibers  Reticular fibers

Marfan Syndrome

Clinical disorders resulting from defects in collagen synthesis TypeDiseaseSymptoms IOsteogenesis imperfecta Spontaneous fractures, progressive hearing loss, cardiac insufficiency IIIEhlers-Danlos (type IV) Hypermobility of digits, early morbidity/mortality from rupture of aorta or intestine multiple Scurvy (lack of vit. C, a cofactor for prolyl and lysyl hydroxylase) Ulceration of gums, hemorrhages

TTendon and Ligament CCartilage BBone

Tendon & Ligament

Tendon: Anatomy  Tight, parallel collagen bundles  Transmit forces muscle -> bone  Great tensile strength  Poor resistance to compression and shear forces  Surrounded by paratenon +/- sheath

Tendon: ECM  75% Collagen fibers ( 95% type I collagen, 5% type III collagen )  5% Proteoglycans ( decorin and biglycan ) Decorin most predominant cross-links antifibrotic. Aggrecanpresent at points of tendon compression

Tendon: Cells  Tenocyte: Fibroblast-like differentiated cells Synthesize ECM

Paratenon Covered Vs Sheathed

Tendon Classification  Unsheathed (Paratenon-covered) Highly vascular Majority of tendons (move in a straight line) Ex. Patellar tendon, Achilles  Sheathed Tendons that bend sharply Sheath acts as a pulley and directs tendon path Sliding is assisted by synovial fluid Ex. Flexor Tendons

Injury & Repair  Three stages of tendon healing: Inflammation (1 st week) Proliferation (maximal type III collagen production) 2 nd – 4 th week Remodeling (type I collagen)

Ligament

TTendon and Ligament CCartilage BBone

Cartilage: Functions  Support  Shock absorber  Bone movement  Bone development

Cartilage  Perichondrium : dense CT  Cartilage is AVASCULAR and NO nerve supply (but the perichondrium does)  Ground substance: ( Glycoptn, Proteoglycan & Hyaluronic acid)  Chondrocytes lie in lacunae

 According to fibers in matrix TypeFibers HyalineCollagen type II ElasticElastic fibers + Collagen II Fibrocartilage Collagen I

Elastic Cartilage  Similar to hyaline cartilage + elastic fibres in the matrix.  Sites: External ear. Epiglottis.

Fibrocartilage  No perichondrium.  Rows of chondrocytes in lacunae separated by parallel bundles of collagen fibers type I  Sites: Intervertebral discs. Symphysis pubis Knee Mensci

Growth Pattern of Cartilage  Interstitial Growth  “Growth from within” i.e Epiphyseal plate  Pre-exesting chondrocyes secrete matrix  Appositional Growth  “ Growth from outside”.  Chondroblast withen perichondrium secrete matrix  When surrounded by matrix  Chondrocyte  Cartilage stop grow in late teens  Regenerates poorly in adults

TTendon and Ligament CCartilage BBone

Bone Tissue (osseous tissue)  2 types – compact and spongy  Compact  Osteon – basic unit of compact bone  Lamellae – concentric circles of matrix  Lacunae – spaces in the matrix that house cells  Osteocytes – mature bone cells  Spongy  Trabeculae – columns of bone with spaces filled with red bone marrow

ECM Organic 50% Fiber Collagen I Ground Substance Glycoptn,Proteoglyca n Inorganic 50% Calcium, Phosphorus & Other

Micrograph of Spongy Bone

Connective Tissue: Bone (Osseous Tissue) Figure 4.8j

Connective Tissue: Bone (Osseous Tissue) Hard, calcified matrix with collagen fibers found in bone Osteocytes are found in lacunae and are well vascularized Supports, protects, and provides levers for muscular action Stores calcium, minerals, and fat Marrow inside bones is the site of hematopoiesis

Take Home Messages  Connective Tissue is one 4 types of tissues  Consist of ECM + Cells  Tendon: sheathed & Paratenon-Covered  Ligament similar to tendon except ???  Cartilage is A Vascular & No Nerve supply  Bone is the hardest connective tissue  Collagen fibers in bone mainly type I