Tissues Test - 59

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'.

• Simple squamous epithelium lines the air sacs, or alveoli, of the lungs.
• Simple squamous epithelial cells in the alveoli allow the exchange of gases in the lungs.
• Striated, columnar and cuboidal epithelium is absent in the lines of alveoli. 

Hence, the correct answer is option 'C'.

• Root hair is the minute structure generally, present on the stem and the roots. It is a tubular outgrowth of a trichoblast, a hair-forming cell on the epidermis of a plant root.
• The trichomes often cover the plant body and are the result of divisions of epidermal cells. Trichomes may be either unicellular or multicellular and are either glandular, consisting of a stalk terminating in a glandular head, or non-glandular, consisting of elongated tapering structures.
• Guard cells are specialized cells regulating the opening and closing of stomata.
• Cuticle, collenchyma, and stomata are absent in roots. 

Dendrites are the extensions of a cell body of a neuron. They receive signals from sensory receptors or other neurons and bring them towards the cell body. Thus, the correct answer is option A.

Schwann/Schwarm cells of peripheral nervous system produce the myelin sheath around the myelinated fibers. Gaps between two Schwann cells form nodes of Ranvier which are the unmyelinated areas. Dendrites are the small extension of nerve cells that receive signals from sensory receptors or other neurons and brings them towards the cell body. The synaptic knob is the small button like structure present at the end of the axonal branch at the synapse and serves to store the neurotransmitters which are released in the synaptic cleft. The correct answer is A.

Cardiac muscles are found in the wall of the heart. The shape of the cardiac muscles is referred to as semi-spindle and they are composed of branched muscle fibres. They possess striations in the form of light and dark bands. The cardiac muscles are involuntary in nature and cannot be controlled willingly. 

The alveoli in the lungs are where the gaseous exchange takes place. Alveoli are lined by a single layer of squamous epithelial cells. These are the thin layered cells which allows the passage of the gases through the tissues during external respiration.