2-The connective tissues The connective tissue ,connects ,holds and supports body tissues and organs together. Connective Tissue is mesodermal in origin . It is characterized by the presence of several types of cells separated and immersed in an abundant intercellular formed by these cells. Function: Structural function ( tendon) . Defensive function (phagocytic cells-plasma cells). Neutritional functions due to its rich content of blood vessels and abundant matrix and tissue fluid .

Connective tissue composed of 3- Cells 1- Matrix (may be solid (as in bone), soft (as in loose connective tissue), or liquid (as in blood). 2- Fibers: A- Collagenous fibers (white) (protein=collagen) (flexible-bundles- unbranched ) B- elastic fibers (protein=elastin) ( elastic single-branched) C- reticular fibers. (protein =reticulin) 3- Cells fibroblast and fibrocytes- plasma cell –adipocytes-mast cell

Types of connective tissues: 1--Connective tissue proper: A-Loose connective tissue . B-Adipose connective tissue . C-Dense fibrous connective tissue . 2-Specialized connective tissue: A-cartilage (perichondrium- chondroblast and chondrocytes- matrix) B-bone (periosteum-osteoblasts-osteocytes)-ossien(calcium phosphates –calcium carbonate) C-Blood (red blood cells-white blood cell-plateletes )and lymph

1- Connective tissue proper A-Loose Connective tissue - Loose connective tissue has all three fiber types(collagen-elastic –reticular). Flexible-richly vascular -support epithelial T. It composes of different cell types: 1-fibroblast (secretes matrix & fibers) 2-Macrophage (defense by phagocytosis) 3- adipocyte (storage fat as a source of energy)

B-Adipose connective tissue It is a type of connective tissues that store fat in adipose cell distributed throughout the matrix Function: 1-Store energy . 2-Subcutaneous adipose tissue shapes the body. 3-Act as a fixative to vital organ as kidney and uterus.

C-Dense fibrous connective tissue dense collagen fibers-little amount of ground substance –less flexible and more resistant than loose CT. example :tendon

2-Specialized connective tissue A- cartilage We have cartilage in nose, ears, and vertebral disks (Support )

B- Bone The skeleton supporting most vertebrates is made of bone. The bone contain osteoblasts that deposit a matrix and collagen fibers . Hard mammalian bones consists of repeating units called osteon (Haversian system). Each osteon has a central canal containing blood vessels and nerves that service the bone.

C-Blood The matrix is a liquid called plasma, consisting of water, salts, and a variety of dissolved proteins. Types of blood cells are: Erythrocytes (red blood cells), Leukocytes (white blood cells) Platelets. Functions of cells: Red cells carry oxygen. White cells function in defense against microbes. Platelets help in blood clotting.

4-Nervous Tissue It consists of two types of cells : (b) Neuroglia It consists of two types of cells : (a)-Neurons (nerve cells) It consists of cell body and extensions, called dendrites and axon. The neurons(receive information and conduct it) (b)-Neuroglia (supporting cell )

Dendrites transmit nerve impulses from their tips toward the rest of the neuron. Axons transmit impulses toward another neuron or toward an effector, such as a muscle cell.