Science Answer the questions.[Bio-2M]

Three features of cardiac muscles are:

1. Cardiac muscles are involuntary muscles that contract rapidly, but do not get fatigued.
2. The cells of cardiac muscles are cylindrical, branched, and uninucleate.
3. They control the contraction and relaxation of the heart.

Skeletal connective tissue are the tissues which join skeletal organs like bones. These oragans include tendons, ligaments and bones and make the whole skeletal system of our body.
Function:

1. It helps in the movement of body.
2. Protects major organs of our body like skull and rib cage.

Features of sclerenchyma fibers:

• These are dead elements.
• They have thick wall of lignin, are elongated and pointed at ends.
• They have pits also.
• They mostly occur in groups.

Features of sclereids:

• These are dead elements.
• These are oval, spherical and are thickened due to lognin deposition.
• They have very narrow cavities at the centre.

Sclerenchyma tissue are dead simple permanent tissue of the plant. The cells of sclerenchyma are closely packed without intercellular spaces, like tiles in mosaic floor so that, it can provide the strength, rigidity, flexibilty and elasticity to the plant to withstand various strains.

Sieve tube elements do not have nuclei but have cytoplasm. They are dependent on adjacent companion cells which contains dense and very active cytoplasm and a large elongated nucleus.

The different types of elements present in the phloem are:

1. Sieve tubes: Sieve tubes are slender, tube-like structures composed of elongated thin-walled cells, placed end to end. Their end walls are perforated by numerous pores and are called sieve plates.
   
2. Companion cells: It is a small thin-walled cell containing dense and very active cytoplasm and large elongated nucleus.
   
3. Phloem parenchyma: These are thin-walled, living cells of parenchyma of phloem. They have two functions, storage and slow lateral conduction of food.
   
4. Phloem Fibre: These are thick-walled, elongated spindled shaped dead cells which posses narrow lumen. They provide mechanical strength to the tissue.
   

The various cells of connective tissue are fibroblasts, adipose cells, macrophages, mast cells and lymphocytes.

The protein fibres of connective tissue are white fibres of collagen, yellow fibres of elastin and reticular fibres of reticulin.

Four main types of animal tissues are:

1. Epithelial tissues.
2. Muscular tissues.
3. Connective tissues.
4. nervous tissue.

Xylem Tissue:

1. Parenchyma:

2. Collenchyma:

Xylem:

1. It conducts water and minerals.
2. Conducting channels or tracheary elements are tracheids and vessels.

Phloem:

1. It conducts organic solutes and food materials.
2. Conducting channels are sieve tubes.

Tracheids:

1. Single celled.
2. The end walls remain intact.

Vessels:

1. Made up of a row of cells.
2. End walls get dissolved and become perforated.

Writing with hand is voluntary muscles action.

Pumping of heart involuntary, e., it is controlled by cardiac muscles.

Movement of choclate in your intestine is involuntary muscles.

Jumping of frog is the activity of voluntary muscles as it is controlled by skeletal muscles.

Aerenchyma: It have spaces or air channels on the leaves, stems and roots of few plants that allows exchange of gases between the shoot and root.
Chlorenchyma: It consists parenchyma cells that contain chloroplasts and forming the basic green tissue of plant leaves and stems.

Connective tissues are most abundant and widely distributed in the body of complex animals. The cells of connective tissue are loosely spaced and embedded in an inercellular matrix. The matrix may be jelly like, fluid, dense or rigid.

Cells of bark are dead and compactly arranged without intercellular spaces. They have a chemical called suberin in their walls that make them impervious to gases and water.

Fat acts as subcutaneous insulation of body for thermoregulation. The animals living in cold regions have various layers of fat so that the temperature of the body can be maintained and also because fats do not allow the internal heat to escape out of the body.

Because adipose tissue stores fats ,storage of fats act as insulator.