Structural Organisation in Animals Test - 3

Apart from being connective tissue, Areolar tissue is also protective in nature. It has large number of fibroblast cells which produce fibres. Mast cells, plasma cells and macrophages help to protect against pathogens and aid in tissue repair.

Smooth muscles are ‘involuntary’ muscles as they can't be directly controlled. We usually are not able to make it contract merely by thinking about it as we can do with skeletal muscles. Involuntary muscles are under control of medulla oblongata and part of cerebrum.  Smooth muscles are spindle shaped or fusiform, uninucleated and unstraited fibres.The wall of internal organs such as the blood vessels, stomach and intestine contains this type of muscle tissue.

The connective tissues have soft tissues to specialised types, which include cartilage, bone, adipose, and blood.

Tight junctions hold cells together. They are narrow belts that circle around the upper part of lateral surfaces of the adjacent epithelial cells to create a fusion point.  They stop substances from leaking across a tissue as they prevent passage of molecules and ions through space between adjacent cells.

The most abundant type of animal tissue connective tissue as it forms variety of tissues such as blood, bone, cartilage, adipose, lymph, tendon and ligament. These connective tissue types perform wide range of functions in the animal body such as giving support, packing, repairing, storing of fat, connecting different organs, etc.

In the early fetus, erythropoiesis takes place in the mesodermal cells of the yolk sac. Later, the production of RBCs starts in the fetal liver and increases till the 2^nd trimester. After this, the rate of synthesis begins to decline in liver as erythropoiesis increases in the bone marrow. RBCs are still produced in the liver for approximately 1 week after birth.

Study of organisms at tissues level is called histology.It includes study of tissue structure, origin, location and function.

Tongue is covered by non-keratinized squamous epithelial tissues having taste buds of different kinds in different regions of tongue.

Two animal cells are interconnected by desmosomes, through which exchange of materials takes place between two cells. It is formed from protein plaques in the cell membranes linked by filaments.