Tissues Test - 52

Each stomatal pore is surrounded by two guard cells that assist in stomatal opening driven by turgidity of guard cells. They are the only epidermal cells with unevenly thickened walls and having chloroplast. They are kidney shaped in dicots and dumbell shaped in monocots.

Hence the correct option is A.

• Epidermis forms the outer protective covering of primary plant body. The epidermal cells secrete cutin, which is a hydrophobic substance and prevents water loss. The cutin forms a covering outside the epidermal cells in all plants parts except root.
• The innermost layer of cortex forms endodermis, which has compactly arranged barrel shaped cells. The primary thin walled endodermis shows suberin deposition in the form of bands or strips that run around the radial and end walls of the cells called Casparian strips. 
• Hypodermis refers to 5-7 layers of cortical cells present just beneath the epidermis.

Solution:

• Correct answer is option A 

• Explanation for the correct option

Suberin is a waxy layer. It is impermeable to both gases and water. A mature cork cell is non-living and has cell walls that are composed of this waxy substance - suberin. Suberin prevents excess loss of water.

The brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. In a typical human, the cerebral cortex is estimated to contain 15-33 billion neurons, each connected by synapses to several thousand other neurons. These  neurons communicate with one another by means of long protoplasmic fibers called axons, which carry trains of signal pulses called action potentials to distant parts of the brain or body targeting specific recipient cells. These brain cells are the only cells which do not have the ability to regenerate.

• The dilator muscle of iris is a smooth muscle of the eye. 
• The middle layer of the uterus is formed of smooth muscles. 
• The bronchi and bronchioles also have a layer of smooth muscles which help them to contract and dilate. 

The basic parts of a neuron are the dendrites, the cell body and the axon. However, all neurons vary somewhat in size, shape and characteristics depending on the function and role of the neuron. Some neurons have few dendritic branches, while others are highly branched in order to receive a great deal of information. Some neurons have short axons, while others can be quite long. The longest axon in the human body extends from the bottom of the spine to the big toe and averages a length of approximately three feet.