(3) Connective Tissues

1. 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).

2. 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-elasticغير 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.

3. أنسجة ضامة أصيلة أنسجة هيكلية 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 وعائية

4. A • Loose connective tissueالنسيج الضام الفجوي : - Binds epithelia to underlying tissues and functions a holding organs in place. - It has all three fiber types. - 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.

5. B • Adipose tissueالنسيج الدهني : It is a specialized form of loose connective tissues that store fat in adipose cellsخلايا دهنيةdistributed throughout the matrix. 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.

6. C • 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. Functions: • This type of connective tissue attaching muscles to bones, and joining bones to bones at joints.

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

8. 5 • 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. • 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.

9. 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 bloodclotting. 6

11. 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.

12. 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.