Animal tissues - class-IX

Smooth muscles are spindle-shaped and are under involuntary control. They are seen in the internal organs such as the blood vessels, iris and the lung bronchi. In the blood vessels, they enable the blood flow. In iris, they increase the pupil size in the presence of bright light. They help in lung contraction and relaxation due to their presence in bronchioles. Thus the correct answer is option D.

Muscles contract via the action of proteins actin and myosin. Both these
proteins are present as microfilaments. Actin forms the thin filaments of
muscle cells and myosin forms the thick filaments.

"Myo" refers to "Muscles". Myology is the study of the muscular system, including the study of the structure, function, and diseases of muscle.

Cardiac muscles are specialized involuntary muscles found exclusively in the heart wall.

Striated and voluntary muscles are skeletal muscles, which are attached to bones and responsible for the movement of limbs.

Mast cells are immune cells that release histamine and heparin; they are commonly found in connective tissues, specifically areolar tissue.

Areolar Tissue is a common form of loose connective tissue. Areolar tissue is found in many locations around the body.

Mammary glands are a modification of the epithelial layer or epithelial tissue. They are formed of the glandular epithelium.

Tissues found on the upper surface of the skin is epidermis and dermis is found beneath it.

The external surfaces and internal linings of the animal body are made up of various kinds of epithelial tissues. Epithelial tissues have various functions all across our bodies like secretion, absorption, protection, sensing and, to some extent, thermoregulation. So, the correct answer is 'Epithelial'.

• Cardiac muscle is a type of involuntary striated muscle found only in the walls of the heart. 
• This is a specialized muscle that, while similar in some fundamental ways to smooth muscle and skeletal muscle, has a unique structure and with an ability not possessed by muscle tissue elsewhere in the body. 
• Cardiac muscle, like other muscles, can contract, but it can also carry an action potential (i.e., conduct electricity), like the neurons that constitute nerves.
•  Furthermore, some of the cells have the ability to generate an action potential, known as cardiac muscle automaticity. Cardiac muscle is adapted to be highly resistant to fatigue:
•  it has a large number of mitochondria, enabling continuous aerobic respiration, numerous myoglobins (oxygen-storing pigment), and a good blood supply, which provides nutrients and oxygen.