Lecture 12 Animal Tissues 3 Connective Tissues Connective

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 matrix ﺍﻟﻮﺳﻂ ﺑﻴﻦ ﺍﻟﺨﻠﻮﻱ. – The matrix generally consists of fibers ﺃﻠﻴﺎﻑ that 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) ﺍﻟﻤﺮﻧﺔ ﺍﻷﻠﻴﺎﻑ : 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 tissue ﺍﻟﻔﺠﻮﻱ , B)- Adipose connective tissue ﺍﻟﺪﻫﻨﻲ , C)- Fibrous connective tissue ﺍﻟﻠﻴﻔﻲ , D)- Cartilage ﺍﻟﻐﻀﺮﻭﻑ , E)- Bone ﺍﻟﻌﻈﻢ , F)- Blood ﺍﻟﺪﻡ. ﺃﻨﺴﺠﺔ ﺿﺎﻣﺔ ﺃﺼﻴﻠﺔ ﺃﻨﺴﺠﺔ ﻫﻴﻜﻠﻴﺔ ﺃﻨﺴﺠﺔ ﻭﻋﺎﺋﻴﺔ � Each has a structure correlated with its specialized function.

A. Loose connective tissue ﺍﻟﻨﺴﻴﺞ 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: 1. Fibroblasts ﺧﻼﻳﺎ ﻟﻴﻔﻴﺔ : secrete the protein ingredients of the extracellular fibers. 2. Macrophages ﺧﻼﻳﺎ ﺑﻠﻌﻤﻴﺔ : are amoeboid cells that engulfing bacteria and the debris of dead cells by phagocytosis. A

B. Adipose tissue ﺍﻟﻨﺴﻴﺞ 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.

C. Fibrous connective tissue ﺍﻟﻨﺴﻴﺞ 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. C

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

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

F. Blood ( ﺍﻟﺪﻡ 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: 1. Erythrocytes (red blood 2. 3. 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

4. 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.