Kharkov National Medical University CONNECTIVE TISSUE Department of

Kharkov National Medical University CONNECTIVE TISSUE Department of histology, cytology and embryology 2013 medical students

CONNECTIVE TISSUE • Connects other tissues, underlies or surrounds them. • Produces and maintains many different intercellular substances. • Provides support and nourishment.

Connective Tissues Classification： Blood & lymph Connective tissue proper : Loose connective tissue Dense connective tissue Specialized Cartilage & bone Adipose tissue Reticular tissue Mucoid tissue Pigment tissue

Note: All Connective Tissues have: Common origin - • from mesenchyme • Common structure Cells + Extracellular substance • Common similar) functions

• Note: Connective Tissues contain a high ratio of extracellular matrix to cells. • extracellular matrix is mostly secreted by cells, which are embedded in it. • extracellular matrix varies for different tissues and provides their structural and functional features. • Examples : the fluid part of blood the hard part of bone, the tough part of fascia, the resilient part of cartilage.

Embryonic Connective Tissue --- Mesenchyme • Consists of cells and ground substance with reticular fibers • Gives rise to all types of Connective Tissues

Connective tissue cells: • 1 st group - Fixed cells (intrinsic) – stable population: • 1. fibroblast – main cells, produce fibers • 2. adipocyte • 3. reticular cell • 4. pericyte 5. undifferentiated cells(adventitial, perivascular – stem cell) All arise from mesenchyme. • 6. Pigment cell – is from neural crest.

Connective tissue cells: • 2 nd group - Mobile cells – are the blood leucocytes.

Fibroblast is fiber forming cell Mature fibroblast is called fibrocyte.

Adipocytes (fat cells) function as store . house, mechanical support, conservation of body heat

Mobile cells = blood leukocytes Macrophage blood monocyte ps er ph lys

Plasma cell B-lymphocyte

Mast cells = basophils.

Other mobile cells: • • • All types of T-lymphocytes Microphage = neutrophil Tissue eosinophil

Connective tissue proper • Consists of cells and extracellular matrix, including fibers and ground substance. • Classified: • as loose or dense regular or irregular

Classification • loose – has predominance of ground substance • dense – has predominance of fibers • regular – fibers form parallel bundles • irregular – fibers are disordered

• Loose (Areolar) is always irreguar CT • Dense: – Dense regular CT – Dense irregular CT

Loose irregular connective tissue (L. I. C. T. ) • Is the most distributed • it contains blood vessels

The Cells and Fibers of L. I. C. T.

General components of matrix : 1. Fibers and 2. Ground substance – is a gel containing: • water, salts and • 3 kinds of molecules containing carbohydrates: – glycosaminoglycan or GAG, – proteoglycans and – glycoproteins

Extracellular matrix (ECM)

Features of ground substance: • Permeability • Barrier to the penetration of bacteria

Hylauronidase is an enzyme produced by WBC’s, sperm and some bacteria. Injection of hyaluronidase can speed the passage of drugs and fluid through the tissue.

Types of C. T. Fibers Three types of fibers – Collagen fibers • Strongest and most abundant Tensile strength > steel – Elastic fibers • “Yellow fibers” • Long, thin, branching fibers • Can stretch and recoil – Reticular fibers Fine collagenous fibers

Distribution of Connective tissue proper (CTP ) CTP is widely distributed. It forms the capsules of organs and thin septa inside them. It always underlines epithelia. It contains blood vessels and through its ground substance all nutrients and waste products diffuse between the blood and parenchymal cells of all other tissues and organs.

Connective tissue proper Functions: • • • Mechanical support Protection Exchange of metabolites. Homeostasis Protection against infections Repair after injury, plastic function

LCT: protection against infections, noxious agents: Cooperation of blood and connective tissue cells for: • Local reaction - inflammation • General immunological reaction

Repair after injury, plastic function of LCT • High regenerative capacity (fibroblast) • Fibrous scar formation • NOTE! LCT carries additional functions

Other types of Connective tissue proper (CTP): Dense Regular CTP Dense Irregular CTP Fibers are predominant elements

Dense Regular Connective Tissue fibrocyte • Collagen fibers form parallel bundles • fibrocytes tendons, aponeuroses Tensile strength in one direction

Dense Irregular Connective Tissue Fibrocyte • Collagen fibers are irregularly arranged • Tissue can resist tension from any direction • Very tough tissue -- dermis of skin

Connective tissue specialised Adipose: • Location – deep to skin: sides, buttocks, breasts; padding around eyeballs and kidneys • Function – insulation, mechanical support, stores energy. Reticular: • Location – spleen, lymph nodes, bone marrow • Function – supporting framework for haemopoietic organs • Mucoid: umbilical cord, incompressible

Adipose Tissue