Connective Tissues are attached to different structures just like muscle with skin or bones. They form a supporting framework of cartilage and bones in the body. Adipose connective tissue stores fat and fluid connective tissue namely blood and lymph transport material like food, hormones, gases, and wastes from one part of the part body to another. White blood corpuscles and lymphocytes of blood and lymph i.e., macrophages, monocytes, and neutrophils protect against bacterial infections as these act as phagocytes. Connective tissue forms a protective sheath around delicate organs such as ovaries, testes, kidneys and spleen. Adipose tissue forms cushion around organs like kidneys, ovaries and eyeballs. Areolar tissue acts as packing material for all the organs. Connective tissue gives contour to the body. It also provides colouration and colour patterns to the body. In human beings, skin colour is a device to protect the underlying body parts from solar radiation. Based on the nature of the matrix, the connective tissue types are as follows –
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Connective tissues proper
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Specialised Connective Tissue
Today we will learn about Specialised connective tissues.
Specialised connective tissues
Specialised connective tissues are classified into two parts-
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Skeletal Tissues
I. Cartilage
II. Bone
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Fluid Connective Tissues
I. Blood
II. Lymph
These have a unique extracellular matrix that allows them to perform their specialised functions.
1. Skeletal Tissues
I. Cartilage
Cartilage is a semi-rigid, tough but flexible tissue that has great tensile strength. It is supporting and protective in function. Cartilage is formed of perichondrium, matrix and chondrocytes or cartilage cells. Cartilage cells that arise from perichondrial fibroblast cells are called chondroblasts. They lie close to the perichondrium. The chondroblasts that are embedded in the matrix of cartilage are called chondrocytes or cartilage cells and are enclosed in lacunae. Cartilage is present in the articular surfaces of bones that form freely movable joints and between the vertebrae. It is found in the tip of the nose, the pin of the ear, the larynx, etc. In cartilaginous fishes, the entire exoskeleton is formed of cartilage. Cartilages are of 3 types –
1. Hyaline Cartilage – It is glassy and bluish-white. Its matrix is homogenous, translucent, fibreless and elastic. It occurs between the ribs and sternum, in the nasal septum, larynx and tracheal rings and in the hyoid apparatus of the frog.
2. Fibrous Cartilage – Its matrix has a large number of fibres. There are two types –
a. White fibrous cartilage,
b. Yellow elastic cartilage
3. Calcified Cartilage – It has calcium salts deposited in the matrix. It is very hard and inelastic.
II. Bone
Bone is the hardest tissue of the body. It supports and protects don’t parts of the body and helps in locomotion. It does help in maintaining optimal blood calcium levels and thus, acts as a homeostatic organ. There are types of bones –
a. Compact bones or Periosteal Bones
b. Spongy Bones or Cancellous Bones
c. Cartilaginous or Replacing bones
d. Dermal or Investing Bones or Membrane Bones
e. Sesamoid Bones
f. Visceral Bones
2. Fluid Tissues or Vascular Tissues
Vascular Tissues are fluid connective tissues. These include blood, lymph and tissue fluid.
i. These have a fibre-free fluid matrix that is not secreted by cells.
ii. The cells float freely in the matrix.
iii. They circulate in the body and are mainly associated with the transport of substances to and from body cells and help in body defence.
The vascular tissues develop from the embryonic mesoderm and are of two types – Blood and Lymph.
I. Blood
Blood is a red-coloured fluid that circulates in the body in closed blood vessels. An average healthy person of 70kg weight has about 5 to 6 litres of blood. It measures 6-10% of the body weight and about 30-35% of the extracellular fluid (ECF). Blood consists of a watery fluid, the plasma and formed elements of blood cells or corpuscles.
II. Lymph
The lymph is a transparent, slightly yellowish liquid of alkaline nature found in lymphatic vessels. Lymph and blood plasma are nearly identical in composition except that the average protein concentration is comparatively less. It carried some oxygen and the final products of digestion to be supplied to the tissue fluid. The lymph contains several WBCs, mostly lymphocytes. It contains prothrombin and is, therefore, capable of clotting. The composition of lymph varies from place to place and from time to time. Its main function is to carry materials from the tissues into the bloodstream and destroys the invading microorganisms.
Conclusion
Hence, the connective tissue holds other tissues together. It contains a large number of extracellular materials rich in fibres or deposited with mineral sales or fluid. Areola connective tissue forms the supporting framework of organs. It is made of several types of cells- fibroblasts, macrophages, plasma cells, fat cells, mesenchymal, lymphocytes, chromophore and mast cells, and white collagen and yellow elastic fibres. Areolar tissue attaches skin with muscles, blood vessels and nerves with surrounding tissues, peritoneum with body wall and viscera, and muscle fibres with one another. Blood is a fluid connective tissue composed of plasma and blood cells and blood platelets help in the clotting of blood plasma and blood cells and blood platelets help in the clotting of blood.