CONNECTIVE TISSUES

• Areolar

• White fibrous

• Yellow elastic

• Cartilage

• Bone

• Blood

• Connective tissue binds structures together, provides support and protection, fills spaces, stores fat, and forms blood cells

• They provide source cells for muscles and skeletal cells in animals that can regenerate lost parts

• Connective tissue cells are separated widely by a matrix, which is a non-cellular material that varies in consistency from solid to semi-fluid to fluid

(a) Loose Fibrous (b) Dense fibrous

- The cells of Loose fibrous and Dense Fibrous connective tissues are called fibroblast and are located some distance from one another and separated by a jelly-like matrix that contain white collagen fiber and yellow elastic fibers

• Connective tissue types differ in microscopic appearance, but all consists of cells, fibres and ground substance

• The types and subtypes are classified according to the amounts, types, and proportion of these components

2 Types of Fibers

• Collagen: provide flexibility and strength• Elastic: provide elasticity

(a)Loose fibrous connective tissue- supports epithelium and also many internal vertebrate organs- It forms protective covering enclosing many internal organs such as muscles, blood vessels and nerves

Elastic fiber

Collagen fiber

fibroblast

Loose fibrous connective tissue

(b) Dense fibrous connective tissue

• contains many collagenous fibers that are packed closely together

• Has more specific functions in vertebrates than loose connective tissue

• Found in tendon which connect muscles to bones, and in ligaments, which connect bones to other bones at joints

Dense fibrous connective tissue

Adipose tissue• insulates the body and provides padding because the fibroblasts enlarge and store fat

• In mammals, adipose tissue is found beneath the skin, around the kidneys, and on the surface of the heart

Reticular connective tissue• found in the lymph nodes, the spleen, and the bone marrow

Adipose tissue

• Several connective tissue are found in the human body

• Each of these consists of specialized cells imbedded/ surrounded by an intercellular matrix

• Cells produce this matrix which forms a basis of non living material in which the cells are scattered

• Supporting connective tissue is used to give strength, support, and protection to the soft parts of the body

• Cartilage and bone are two kinds of supporting connective tissue found in man

• The matrix in cartilage is a protein-polysaccharide mixture, called chondrin

(1)AreolarStructure• Tissue is loosely connected and consists of

fibroblasts, macrophages, mast cells, fat cells, white cells and elastic fibres in a matrix

Location• All over the human body

Function• Connects the layer of the skin and stores fat and

supports and protects the organs and muscles• Prevents blood clotting-Adipose tissue consists of fat deposits that form a

layer in the dermis of the skin, which helps to insulate th body against heat loss

-Blubber in whales and seals consists of many layers of adipose tissue

(2) White fibrousStructure• The tissue has bundles of collagen fibres to strengthen it and make it flexible

Location•The discs between the vertebrae and in all ball-and socket joints, like in the hips and shoulders

Functions• Acts as a shock absorber in the vertebrae of the spine and makes the sockets of joints deeper to prevent the bones from dislocating• Tendons connect muscle to bones

White fibrous

(3) Yellow elasticStructure• This cartilage has collagen fibres and yellow elastic fibres in its matrix and is strong, flexible and tightly packed

Location•The pinna of the ear, the epiglottis and in all ligaments

Functions• Give shape to the pinna of the ear•Give strength and support to the epiglottis•Ligaments attach bone to bone and prevent bones from moving out of place

(4) CartilageStructure• Cartilage tissue contains living cells called chondrocytes and live in little spaces called lacunae•The chondrocytes produce a strong, flexible see-through matrix

Location• The end of the nose, the C-shaped cartilage rings around the trachea in the throat, the connection of the ribs to the sternum (breast bone) and the ends of bones joints

Functions• Cartilage reduces friction in the joints of bones•It attaches bones to other bones• It keeps the trachea open so that we can breath freely

Hyaline cartilage

matrix

Cell within a lacuna

BONES

• Bone is rigid, strong, hard connective tissue that is the supporting structure for the rest of the body

• It forms an endoskeleton in mammals

2 Types of Bone• Spongy bone• Compact bone: cells in concentric rings, occur in bones of skeleton

• The cavity inside the bone is lined by the endosteum• The outside of the bone is covered by the periosteum

(4) BonesStructure• Bone cells are called osteocytes and live in cavities called lacunae• Layers called lamellae form around the osteocytes• Between the lamellae are tiny canals called canaliculi that link the osteocytes to each other• In the centre of bone tissue is the Haversian canal, which contains an artery, vein and a nerve

Location• Osteocytes form bones• Bones make up skeleton

Functions• Bones support and protect internal organs•Serve as an attachment for muscles and help us to move• The bone marrow of long bones produces red and white blood cells

compact bone

Spongy bone

Blood

• Blood is fluid connective tissue

• Adult humans have about 5.5 litres of blood flowing through their blood vessels

• Blood consists of plasma (the watery part) and haemocrit (the cells)

• Blood transports substances to and from the cells

(5) BloodStructure• Plasma is a straw coloured liquid that consists of 90% water

Functions• Substances like nutrients, wastes, inorganic salts, oxygen, carbon dioxide, plasma proteins, hormones, antibodies and enzymes are transported in the plasma

• Plasma helps to control the body temperature

-Haemocrit consists of three types of cells(i)Red blood cells(ii) White blood cells(iii) Blood platelets

Blood cells

(1)Red blood cells (corpuscles/erythrocytes)Structure•Cells are red in colour, have a biconcave shape and no nucleus• Contain haemoglobin• Iron is needed to make the haemoglobin and vitamin B12 to produce red blood cells• They are produced by the red bone marrow and live for 120 days• The liver and spleen break down the blood cells

FunctionsHaemoglobin carries oxygen from the lungs to all the cells as oxyhaemoglobin and helps to regulate the pH of the blood

(2) White blood cells (leucocytes)Structure• Cells are colourless, have an irregular shape and have a nucleus

•Are produced in the red bone marrow and live for 21 days

Functions• Leucocytes are able to “swallow” germs by a process called phagocytosis because they are able to change shape

• They produce antibodies, which destroy germs

(3) Blood platelets (thrombocytes)Structure• Are small discs, have no nucleus and are more like cell fragments which like to stick together

• Contain fibrinogen that helps to clot the blood

• Are produced by red bone marrow and live for 10n days

Functions• Block up small holes in blood vessels to stop bleeding

•Form blood clots by changing the fibrinogen into fibrin threads