Lecture 12: Animal Tissues (3) Connective Tissues Connective tissue functions: - They mainly to bind تربط and support تدعم other tissues. Structure: Connective tissues have a population of cells scattered مبعثرة through an extracellular matrixالوسط بين الخلوي . The matrix generally consists of fibers أليافthat may be liquid, jellylike, or solid. In most cases, the connective tissue cells secrete the matrix. The matrix may be solid (as in bone), soft (as in loose connective tissue), or liquid (as in blood).

Types of connective tissues fibers There are three kinds of connective tissues fibers, which are all proteins: a)- Collagenous fibers (white) الألياف الكوللاجين: Are made of collagen and non-elastic غير مرنة b)- Elastic fibers (Yellow) الألياف المرنة: Are long threads of elastin, which provide a rubbery quality. c)- Reticular fibers الألياف الشبكية: Are very thin and branched, and composed of collagen. It joins connective tissues to adjacent tissues.

Types of connective tissues The major types of connective tissues in vertebrates are: A)- Loose connective tissueالفجوي , B)- Adipose connective tissueالدهني , C)- Fibrous connective tissueالليفي , D)- Cartilageالغضروف , E)- Boneالعظم , F)- Bloodالدم . Each has a structure correlated with its specialized function. أنسجة ضامة أصيلة أنسجة هيكلية أنسجة وعائية

Loose connective tissueالنسيج الضام الفجوي : - Binds epithelia to underlying tissues and functions a holding organs in place. - It has all three fiber types. A - It composes of two cell types: Fibroblastsخلايا ليفية: secrete the protein ingredients of the extracellular fibers. Macrophages خلايا بلعمية : are amoeboid cells that engulfing bacteria and the debris of dead cells by phagocytosis.

Functions: Adipose tissueالنسيج الدهني : It is a specialized form of loose connective tissues that store fat in adipose cells خلايا دهنية distributed throughout the matrix. B Functions: Adipose tissue stores fuel as fat molecules. Each adipose cell contains a large fat droplet that swells when fat is stored and shrinks when the body uses fat as fuel.

Fibrous connective tissueالنسيج الضام الليفي : - It is dense, due to its large number of collagenous fibers. - The fibers are organized into parallel bundles making it strong. C Functions: This type of connective tissue attaching muscles to bones, and joining bones to bones at joints.

Cartilage الغضروف (Skeletal Tissue): It has an abundance of collagenous fibers embedded in a rubbery matrix D Chondrocytesالخلايا الغضروفية: helps making cartilage flexible support material. We have cartilage in nose, ears, and vertebral disks.

Boneالعظم (Skeletal Tissue): The skeleton supporting most vertebrates is made of bone, a mineralized connective tissue. This bone contains osteoblastsالخلايا العظمية that deposit a matrix of collagen. 5 Bone is harder than cartilage. Hard mammalian bones consists of repeating units called osteonsمحافظ عظمية (Haversian system). Each osteon has a central canal containing blood vessels and nerves that service the bone.

Bloodالدم (Vascular Tissue): Functions differently from other connective tissues, but it does have an extensive extra-cellular matrix. 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. 6

Nervous tissue: Senses stimuli and transmits signals from one part of the animal to another. The functional unit of nervous tissue is the neuron, or nerve cell. It consists of a cell body and two or more extensions, called dendrites and axons.

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.